HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Figures Only Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Finn, J. P. Articles by Laub, G. Search for Related Content PubMed PubMed Citation Articles by Finn, J. P. Articles by Laub, G.

Cardiac MR Imaging: State of the Technology¹

¹ From the Department of Radiological Sciences, David Geffen School of Medicine, University of California Los Angeles, 10945 Le Conte Ave, Suite 3371, Los Angeles, CA 90095-7206 (J.P.F., K.N., O.R.), and Siemens Medical Solutions, Los Angeles, Calif (V.D., G.L.). Received November 2, 2004; revision requested January 3, 2005; revision received June 24; accepted July 20; final version accepted November 23; final review by J.P.F. May 16, 2006. Address correspondence to J.P.F. (e-mail: pfinn{at}mednet.ucla.edu).

	ABSTRACT

TOP ABSTRACT INTRODUCTION BLACK-BLOOD ANATOMIC IMAGING CARDIAC CINE IMAGING CINE MR WITH STEADY-STATE... MYOCARDIAL TAGGING FLOW QUANTIFICATION MYOCARDIAL VIABILITY IMAGING:... PERFUSION IMAGING CORONARY ARTERY IMAGING INTRAVASCULAR CONTRAST AGENTS CONCLUSION ESSENTIALS References

 
Recent developments in magnetic resonance (MR) imaging of the heart have refocused attention on the potential of MR and continue to attract intense interest within the radiology and cardiology communities. Improvements in speed, image quality, reliability, and range of applications have evolved to the point where cardiac MR imaging is increasingly seen as a practical clinical tool. As is often the case with MR imaging, not all of the most powerful techniques are necessarily easy to master or understand, and many—nonspecialists and specialists alike—are challenged to stay abreast. This review covers some of the major milestones that have led to the current state of cardiac MR and attempts to put into context some concepts that, although technical, have a real impact on the diagnostic power of cardiac MR imaging. Topics discussed include functional imaging, myocardial viability and perfusion imaging, flow quantification, and coronary artery imaging. A review such as this can only scratch the surface of what is a dynamic interdisciplinary field, but the hope is that sufficient information and insight are provided to stimulate the motivated reader to take his or her interest to the next level.

© RSNA, 2006

	INTRODUCTION

TOP ABSTRACT INTRODUCTION BLACK-BLOOD ANATOMIC IMAGING CARDIAC CINE IMAGING CINE MR WITH STEADY-STATE... MYOCARDIAL TAGGING FLOW QUANTIFICATION MYOCARDIAL VIABILITY IMAGING:... PERFUSION IMAGING CORONARY ARTERY IMAGING INTRAVASCULAR CONTRAST AGENTS CONCLUSION ESSENTIALS References

 
Although the potential of magnetic resonance (MR) imaging as a tool for noninvasive diagnosis of heart disease has long been recognized, its widespread adoption in clinical practice is only recently gaining pace. At various times, MR imaging has been hailed as the single modality capable of defining cardiac anatomy and function, myocardial perfusion, myocardial viability, and coronary artery anatomy (1,2). However, cardiac MR imaging has often been regarded as a difficult test with unpredictable results. In recent years, technical developments have had a dramatic effect on cardiac MR applications, such that the debate no longer focuses on the diagnostic power of MR imaging but on availability or local expertise.

More than any other organ system, the heart has played host to a perplexing evolution of MR techniques. Some of these methods, although highly sophisticated, have limited clinical applications. Others have found their way into clinical practice or stand poised to do so. In all cases, MR imaging of the heart must deal with cardiac and respiratory motion, with the conflicting requirements for high spatial and temporal resolution, and with the demand for accurate and reproducible measurements in a clinical environment.

Recognizing that development is an ongoing process, in this review we emphasize those techniques for which there are established clinical applications or that we believe will have a clinical role in the near term. We believe that important tools for today's cardiac MR imager include (a) fast, high-spatial-resolution, steady-state techniques for cine imaging and coronary angiography; (b) dependable techniques for T1-weighted imaging of contrast material–avid myocardial scar; (c) fast techniques to capture the first pass of intravenous contrast material through the heart; and (d) the option to apply parallel imaging to all of the above. The fact that few of these tools were widely available 4 years ago reflects well on the pace of development of the field and the speed of adoption by the community.

	BLACK-BLOOD ANATOMIC IMAGING

TOP ABSTRACT INTRODUCTION BLACK-BLOOD ANATOMIC IMAGING CARDIAC CINE IMAGING CINE MR WITH STEADY-STATE... MYOCARDIAL TAGGING FLOW QUANTIFICATION MYOCARDIAL VIABILITY IMAGING:... PERFUSION IMAGING CORONARY ARTERY IMAGING INTRAVASCULAR CONTRAST AGENTS CONCLUSION ESSENTIALS References

 
A necessary first step in cardiac MR imaging was the application of gating to spin-echo imaging (3–5). The resulting "dark blood" images of the myocardium and cardiac chambers focused attention on the outstanding potential of MR imaging of the heart (6–11). Today, spin-echo imaging plays a more secondary role, but for specific applications involving structural abnormalities of the ventricles and the pericardium, it may still prove useful (12,13). Traditional spin-echo imaging has given way to echo-train imaging, which is usually performed with breath holding.

Black-blood preparation schemes are now standard for spin-echo imaging of the heart and blood vessels, and this usually involves a double inversion pulse pair (Fig 1a) (14–16). With this approach, a single section is acquired per breath hold, and a full examination can be time consuming. At the extreme end of echo-train imaging is the single-shot method (half-Fourier rapid acquisition with relaxation enhancement), with which an image can be acquired within a single heartbeat (17,18) (Fig 1b, 1c). For many protocols involving anatomic surveys, single-shot spin-echo imaging can be a valuable supplement.

View larger version (21K): [in this window] [in a new window] [Download PPT slide]   Figure 1a: (a) Diagram of black-blood double-inversion turbo spin-echo MR sequence. When the electrocardiographic (ECG) R wave is detected, a spatially nonselective (non-sel) inversion pulse is applied and immediately followed by section-selective (sel) reversion pulse. The net effect is to leave spins within the section unaffected, while spins outside the section (including flowing blood) are inverted. Over time, inverted spins relax toward zero where, even if excited by subsequent radiofrequency pulses, they generate little signal. If the readout module, a 90° pulse followed by a train of refocusing 180° pulses, is applied when blood is relaxing to zero, inflowing blood produces no signal. TI = inversion time. (b) Diagram of black-blood double-inversion single-shot spin-echo echo-train sequence. Black-blood preparation is identical to that in a. In this case, however, all lines for the complete image are read out in a single heartbeat (ie, data acquisition is not "segmented"). (c) Adenocarcinoma of right lung invading left atrium. Coronal black-blood double-inversion single shot spin-echo echo-train MR image (repetition time (TR) msec/echo time msec, 2000/56; flip angle, 90°) was acquired in a single heartbeat. Note relatively uniform low signal intensity from blood in cardiac chambers and major vessels and how well the tumor (arrow) is shown invading left atrium from the right lung.

View larger version (15K): [in this window] [in a new window] [Download PPT slide]   Figure 1b: (a) Diagram of black-blood double-inversion turbo spin-echo MR sequence. When the electrocardiographic (ECG) R wave is detected, a spatially nonselective (non-sel) inversion pulse is applied and immediately followed by section-selective (sel) reversion pulse. The net effect is to leave spins within the section unaffected, while spins outside the section (including flowing blood) are inverted. Over time, inverted spins relax toward zero where, even if excited by subsequent radiofrequency pulses, they generate little signal. If the readout module, a 90° pulse followed by a train of refocusing 180° pulses, is applied when blood is relaxing to zero, inflowing blood produces no signal. TI = inversion time. (b) Diagram of black-blood double-inversion single-shot spin-echo echo-train sequence. Black-blood preparation is identical to that in a. In this case, however, all lines for the complete image are read out in a single heartbeat (ie, data acquisition is not "segmented"). (c) Adenocarcinoma of right lung invading left atrium. Coronal black-blood double-inversion single shot spin-echo echo-train MR image (repetition time (TR) msec/echo time msec, 2000/56; flip angle, 90°) was acquired in a single heartbeat. Note relatively uniform low signal intensity from blood in cardiac chambers and major vessels and how well the tumor (arrow) is shown invading left atrium from the right lung.

View larger version (118K): [in this window] [in a new window] [Download PPT slide]   Figure 1c: (a) Diagram of black-blood double-inversion turbo spin-echo MR sequence. When the electrocardiographic (ECG) R wave is detected, a spatially nonselective (non-sel) inversion pulse is applied and immediately followed by section-selective (sel) reversion pulse. The net effect is to leave spins within the section unaffected, while spins outside the section (including flowing blood) are inverted. Over time, inverted spins relax toward zero where, even if excited by subsequent radiofrequency pulses, they generate little signal. If the readout module, a 90° pulse followed by a train of refocusing 180° pulses, is applied when blood is relaxing to zero, inflowing blood produces no signal. TI = inversion time. (b) Diagram of black-blood double-inversion single-shot spin-echo echo-train sequence. Black-blood preparation is identical to that in a. In this case, however, all lines for the complete image are read out in a single heartbeat (ie, data acquisition is not "segmented"). (c) Adenocarcinoma of right lung invading left atrium. Coronal black-blood double-inversion single shot spin-echo echo-train MR image (repetition time (TR) msec/echo time msec, 2000/56; flip angle, 90°) was acquired in a single heartbeat. Note relatively uniform low signal intensity from blood in cardiac chambers and major vessels and how well the tumor (arrow) is shown invading left atrium from the right lung.

	CARDIAC CINE IMAGING

TOP ABSTRACT INTRODUCTION BLACK-BLOOD ANATOMIC IMAGING CARDIAC CINE IMAGING CINE MR WITH STEADY-STATE... MYOCARDIAL TAGGING FLOW QUANTIFICATION MYOCARDIAL VIABILITY IMAGING:... PERFUSION IMAGING CORONARY ARTERY IMAGING INTRAVASCULAR CONTRAST AGENTS CONCLUSION ESSENTIALS References

View larger version (17K): [in this window] [in a new window] [Download PPT slide]   Figure 2a: Diagrams of (a–c) prospectively ECG-triggered and (d) retrospectively ECG-gated cine MR pulse sequences. Ts = imaging time. (a) After the R wave, the first line of the first cardiac phase is acquired, followed in sequence by the first line of all the other cardiac phases, up to the final phase acquired. In the next cardiac cycle, the second line of all the cardiac phases is acquired, up to Np. This continues until all lines (N, phase-encoding steps) have been acquired, or for N heartbeats. In this scheme, the acquisition window is prescribed ahead of time and is generally chosen to be less than the average R-R interval so that the next R wave is not missed, should it occur earlier than anticipated. For this reason, the last 10% of diastole is usually not sampled with prospective triggering. (b) k-Space segmentation. After the R wave, first five lines (in this example) of first cardiac phase are acquired, followed in sequence by first five lines of all the other cardiac phases, up to Np. In the next cardiac cycle, next five lines of all cardiac phases are acquired, up to Np. This continues until all lines (phase-encoding steps) have been acquired, or for N/5 heartbeats. In general, if there are Ls lines per segment, it will take N/Ls heartbeats to acquire the cine study, and the duration of each cardiac phase will be Ls times the duration of the nonsegmented sequence. In this way, temporal resolution is traded against acquisition time. (c) k-Space segmentation and echo sharing. Similar to b, but central line of each segment is repeated between segments, and data are shared around this additional line. In this way, a "sliding temporal window" is generated that is five lines wide but is updated almost twice as often as in the non–echo-shared version. Therefore, almost twice as many cardiac phases are generated. (d) Similar to a, but acquisition window extends to the next R wave, sampling the entire cardiac cycle. Data are then re-sorted according to their location relative to the R-R interval.

View larger version (19K): [in this window] [in a new window] [Download PPT slide]   Figure 2b: Diagrams of (a–c) prospectively ECG-triggered and (d) retrospectively ECG-gated cine MR pulse sequences. Ts = imaging time. (a) After the R wave, the first line of the first cardiac phase is acquired, followed in sequence by the first line of all the other cardiac phases, up to the final phase acquired. In the next cardiac cycle, the second line of all the cardiac phases is acquired, up to Np. This continues until all lines (N, phase-encoding steps) have been acquired, or for N heartbeats. In this scheme, the acquisition window is prescribed ahead of time and is generally chosen to be less than the average R-R interval so that the next R wave is not missed, should it occur earlier than anticipated. For this reason, the last 10% of diastole is usually not sampled with prospective triggering. (b) k-Space segmentation. After the R wave, first five lines (in this example) of first cardiac phase are acquired, followed in sequence by first five lines of all the other cardiac phases, up to Np. In the next cardiac cycle, next five lines of all cardiac phases are acquired, up to Np. This continues until all lines (phase-encoding steps) have been acquired, or for N/5 heartbeats. In general, if there are Ls lines per segment, it will take N/Ls heartbeats to acquire the cine study, and the duration of each cardiac phase will be Ls times the duration of the nonsegmented sequence. In this way, temporal resolution is traded against acquisition time. (c) k-Space segmentation and echo sharing. Similar to b, but central line of each segment is repeated between segments, and data are shared around this additional line. In this way, a "sliding temporal window" is generated that is five lines wide but is updated almost twice as often as in the non–echo-shared version. Therefore, almost twice as many cardiac phases are generated. (d) Similar to a, but acquisition window extends to the next R wave, sampling the entire cardiac cycle. Data are then re-sorted according to their location relative to the R-R interval.

View larger version (14K): [in this window] [in a new window] [Download PPT slide]   Figure 2c: Diagrams of (a–c) prospectively ECG-triggered and (d) retrospectively ECG-gated cine MR pulse sequences. Ts = imaging time. (a) After the R wave, the first line of the first cardiac phase is acquired, followed in sequence by the first line of all the other cardiac phases, up to the final phase acquired. In the next cardiac cycle, the second line of all the cardiac phases is acquired, up to Np. This continues until all lines (N, phase-encoding steps) have been acquired, or for N heartbeats. In this scheme, the acquisition window is prescribed ahead of time and is generally chosen to be less than the average R-R interval so that the next R wave is not missed, should it occur earlier than anticipated. For this reason, the last 10% of diastole is usually not sampled with prospective triggering. (b) k-Space segmentation. After the R wave, first five lines (in this example) of first cardiac phase are acquired, followed in sequence by first five lines of all the other cardiac phases, up to Np. In the next cardiac cycle, next five lines of all cardiac phases are acquired, up to Np. This continues until all lines (phase-encoding steps) have been acquired, or for N/5 heartbeats. In general, if there are Ls lines per segment, it will take N/Ls heartbeats to acquire the cine study, and the duration of each cardiac phase will be Ls times the duration of the nonsegmented sequence. In this way, temporal resolution is traded against acquisition time. (c) k-Space segmentation and echo sharing. Similar to b, but central line of each segment is repeated between segments, and data are shared around this additional line. In this way, a "sliding temporal window" is generated that is five lines wide but is updated almost twice as often as in the non–echo-shared version. Therefore, almost twice as many cardiac phases are generated. (d) Similar to a, but acquisition window extends to the next R wave, sampling the entire cardiac cycle. Data are then re-sorted according to their location relative to the R-R interval.

View larger version (14K): [in this window] [in a new window] [Download PPT slide]   Figure 2d: Diagrams of (a–c) prospectively ECG-triggered and (d) retrospectively ECG-gated cine MR pulse sequences. Ts = imaging time. (a) After the R wave, the first line of the first cardiac phase is acquired, followed in sequence by the first line of all the other cardiac phases, up to the final phase acquired. In the next cardiac cycle, the second line of all the cardiac phases is acquired, up to Np. This continues until all lines (N, phase-encoding steps) have been acquired, or for N heartbeats. In this scheme, the acquisition window is prescribed ahead of time and is generally chosen to be less than the average R-R interval so that the next R wave is not missed, should it occur earlier than anticipated. For this reason, the last 10% of diastole is usually not sampled with prospective triggering. (b) k-Space segmentation. After the R wave, first five lines (in this example) of first cardiac phase are acquired, followed in sequence by first five lines of all the other cardiac phases, up to Np. In the next cardiac cycle, next five lines of all cardiac phases are acquired, up to Np. This continues until all lines (phase-encoding steps) have been acquired, or for N/5 heartbeats. In general, if there are Ls lines per segment, it will take N/Ls heartbeats to acquire the cine study, and the duration of each cardiac phase will be Ls times the duration of the nonsegmented sequence. In this way, temporal resolution is traded against acquisition time. (c) k-Space segmentation and echo sharing. Similar to b, but central line of each segment is repeated between segments, and data are shared around this additional line. In this way, a "sliding temporal window" is generated that is five lines wide but is updated almost twice as often as in the non–echo-shared version. Therefore, almost twice as many cardiac phases are generated. (d) Similar to a, but acquisition window extends to the next R wave, sampling the entire cardiac cycle. Data are then re-sorted according to their location relative to the R-R interval.

	CINE MR WITH STEADY-STATE FREE PRECESSION

TOP ABSTRACT INTRODUCTION BLACK-BLOOD ANATOMIC IMAGING CARDIAC CINE IMAGING CINE MR WITH STEADY-STATE... MYOCARDIAL TAGGING FLOW QUANTIFICATION MYOCARDIAL VIABILITY IMAGING:... PERFUSION IMAGING CORONARY ARTERY IMAGING INTRAVASCULAR CONTRAST AGENTS CONCLUSION ESSENTIALS References

 
In both its original and segmented form, spoiled GRE cine MR is largely a T1-weighted sequence. As such, it is dependent on through-plane flow enhancement to generate contrast between the blood and the myocardium, analogous to time-of-flight MR angiography (30). Like time-of-flight imaging, if the TR is too short or the flow is too slow, the blood becomes saturated. This is particularly the case for long-axis imaging, where blood may linger in the section, and even for short-axis imaging if myocardial function is poor. So, although hardware technology had evolved to the point where a very short TR was achievable, the dependency on flow-enhancement severely restricted the minimum TR that could be used in practice.

An effective alternative to the spoiled GRE approach is steady-state free precession (SSFP) (31,32). Originally described in the heart for real-time cine MR imaging with a very short TR, it proved possible to maintain the steady state for gated high-spatial-resolution cine imaging with k-space segmentation (33,34). In this form, segmented k-space SSFP cine MR imaging has largely replaced spoiled GRE cine MR imaging for all routine applications (35).

Among the advantages of SSFP cine imaging are the relative independence of contrast from blood flow, the speed of acquisition, and the high contrast-to-noise ratio per unit time. With SSFP, the blood signal is dependent on its relaxation time (specifically, the T2*/T1 ratio) rather than its speed of flow, so that even with very poor systolic function, blood-myocardial contrast is excellent. This property also makes myocardial segmentation more easily automated (36) and enhances the accuracy of myocardial mass measurements (37). SSFP techniques recycle coherent transverse magnetization by completely rewinding all gradients and alternating the phase of the radiofrequency excitation (31) (Fig 3a). SSFP cine works best with the shortest possible TR (on the order of 3 msec or faster) (32), so imaging speed is almost three times greater than that of spoiled GRE cine MR (34). A cine SSFP set with a high contrast-to-noise ratio can be acquired in as little as 7 seconds. Also, although it seems counterintuitive, SSFP cine imaging yields highest contrast-to-noise ratio when the largest flip angle achievable is used (Fig 3b). In practice, at a TR of 2.5–3.5 msec, the allowed specific absorption rate will generally limit the flip angle to 60°–70° at 1.5 T.

View larger version (21K): [in this window] [in a new window] [Download PPT slide]   Figure 3a: (a) Diagram of SSFP pulse sequence. Gradients (G) are fully balanced along all three (section-selective, phase-encoding, and readout) axes. Between each two radiofrequency pulses, the sum of positive gradient areas is exactly balanced by the sum of negative gradient areas. In this case, echo and readout occur midway between radiofrequency pulses. TE = echo time. (b) Short-axis breath-hold cine MR images. Comparison of SSFP (left column: 3/1.5; flip angle, 60°) and spoiled GRE (right column: 8/4; flip angle, 20°) cine images. Pericardial fluid (arrows, top row) has higher signal intensity on SSFP image (top left). Blood signal and myocardial definition (arrows, bottom row) are also better on SSFP image (bottom left). Arrowheads = papillary muscle. (Adapted and reprinted, with permission, from reference 34.)

View larger version (162K): [in this window] [in a new window] [Download PPT slide]   Figure 3b: (a) Diagram of SSFP pulse sequence. Gradients (G) are fully balanced along all three (section-selective, phase-encoding, and readout) axes. Between each two radiofrequency pulses, the sum of positive gradient areas is exactly balanced by the sum of negative gradient areas. In this case, echo and readout occur midway between radiofrequency pulses. TE = echo time. (b) Short-axis breath-hold cine MR images. Comparison of SSFP (left column: 3/1.5; flip angle, 60°) and spoiled GRE (right column: 8/4; flip angle, 20°) cine images. Pericardial fluid (arrows, top row) has higher signal intensity on SSFP image (top left). Blood signal and myocardial definition (arrows, bottom row) are also better on SSFP image (bottom left). Arrowheads = papillary muscle. (Adapted and reprinted, with permission, from reference 34.)

With the recent introduction of improved radiofrequency receiver chains and parallel imaging techniques (39,40), the performance of SSFP cine MR has been further enhanced (41). Parallel imaging technology makes use of the spatial sensitivity profiles of surface coils to provide information about where the MR signal is coming from. By combining such information with the spatial encoding of the imaging gradients, the number of gradient encodings (phase-encoding steps) necessary to reconstruct an image can be reduced several fold. For example, by halving the number of gradient encodings (by skipping every second one), the field of view in the phase-encoding direction is halved and the acquisition is accelerated by a factor of two. Normally, this would result in an overfolding artifact, but parallel acquisition techniques prevent or "unwrap" the overfolding by using the information from the surface coils.

Two broad approaches to parallel imaging are in general use. The methods described by Sodickson and Manning (39) and the modifications described by Griswold et al (42) work by substituting directly for phase-encoding steps prior to Fourier transformation. The unmeasured intermediate k-space lines are derived from the measured ones by multiplying each measured signal by a sinusoid, which is approximated by an array of surface coils. Such approaches are said to work in the k-space domain, and they prevent overfolding. The second approach, originally described by Pruessmann et al (43), works on the image data after Fourier transformation. Here, the sensitivity profile of an array of surface coils is used to unwrap the overfolding by means of the mathematic process of matrix inversion.

Parallel acquisition is a general tool with applications across a wide spectrum of cardiac and noncardiac techniques. When used appropriately and with suitable radiofrequency coils and channels, it can enhance speed, coverage, or both (43). Depending on the quality of the information available from the surface coils, acquisition speed may be enhanced several fold.

A drawback of parallel acquisition is the decrease in signal-to-noise ratio (SNR), which invariably occurs. Several factors may contribute to this decrease in SNR, including a geometry factor determined by the coils, a decrease in acquisition time (if acquisition speed is increased), and a decrease in voxel size (if image resolution is increased). Because it is intrinsically a high-SNR technique, SSFP cine MR is more tolerant of the SNR penalty inherent in parallel imaging than is spoiled GRE cine MR. For parallel imaging with an acceleration factor of two, a diagnostic-quality cine set can be acquired in about 4 seconds, or multiple sections can be acquired in a single reasonable breath hold.

It should be noted, however, that whereas parallel imaging can speed image acquisition and help minimize susceptibility artifacts with multiecho techniques such as echo-planar imaging, it does not address the fundamental mechanism of artifact with SSFP cine MR, which is dependent on the shortest TR achievable by the gradients.

Cine MR with Non-Cartesian k-Space Sampling
As most commonly used, SSFP cine MR is implemented with Cartesian, or rectilinear, k-space sampling and cardiac gating. Other schemes, however, have also been described. Because radial k-space sampling seems likely to become more widely used in clinical practice, for angiographic as well as for cardiac applications, we will outline some of its more important properties below. In radial k-space sampling, radial projections replace the rectilinear phase-encoding steps (44). The following apply in the case of radial k-space SSFP cine MR:

1. In place of a phase-encoding gradient, the direction of the frequency-encoding gradient is rotated in a series of projections like the spokes of a wheel.

2. The sampling density is nonuniform; the outer portions of k-space are less densely sampled than the inner portions. All projections include the center of k-space—that is, the center is oversampled, and a filter must be applied to correct for this.

3. Whereas Cartesian undersampling produces an anatomically recognizable wraparound artifact, radial undersampling results in a linear streak artifact, which can have a bizarre appearance. This is because the undersampling occurs in the angular (azimuthal) direction rather than in the (constant) phase-encoding direction, as happens with Cartesian sampling (Fig 4a).

View larger version (14K): [in this window] [in a new window] [Download PPT slide]   Figure 4a: (a) Diagram shows radial scanning. Data are acquired along radius of a circle. Multiple projections are acquired, with angular increment k between projections. Distance between samples along radius kr defines field of view (FOV) in the frequency-encoding direction, 1/kr, as in standard Cartesian sampling. Note that FOV in the angular direction is given by 1/k, which is a function of radial distance from the center. So, angular FOV for high spatial frequencies is smaller than that for low spatial frequencies. However, because the center of k-space is sampled with every projection, full signal amplitude is acquired with all projections. This is different from Cartesian sampling and results in potentially high-signal-intensity streak artifacts, depending on the patient's geometry. kx = Cartesian k-space x-axis, ky = Cartesian k-space y-axis. (b) Short-axis SSFP cine MR images (2.2/1.1; flip angle, 45°) with radial k-space undersampling (top row) versus Cartesian k-space undersampling (bottom row). Characteristic wraparound artifact seen with Cartesian undersampling (arrows, bottom row) is replaced with streak artifact, characteristic of undersampled radial k-space acquisition (arrows, top row). (Adapted and reprinted, with permission, from reference 44.)

5. Radial sampling is also associated with a moderate decrease in SNR, compared with the SNR in Cartesian sampling.

Real-time SSFP Cine MR Imaging
Although now most commonly used in its segmented k-space implementation, the original description of SSFP cine imaging was as a real-time ungated application (32). When the image matrix and spatial resolution are decreased, it is possible to shorten the TR further. In this mode, a low-resolution image can be acquired in less than 100 msec. When data acquisition is continuous, real-time imaging results, such that actual heartbeats are recorded, rather than "average" heartbeats, as is the case with a segmented acquisition. In this way, cine imaging can be performed without cardiac gating and, if needed, without breath holding (44,45) (Fig 4b). Although limited in spatial and temporal resolution in its current format, real-time cine imaging has potentially useful applications in cases of severe arrhythmia or when a gating signal is not available.

View larger version (166K): [in this window] [in a new window] [Download PPT slide]   Figure 4b: (a) Diagram shows radial scanning. Data are acquired along radius of a circle. Multiple projections are acquired, with angular increment k between projections. Distance between samples along radius kr defines field of view (FOV) in the frequency-encoding direction, 1/kr, as in standard Cartesian sampling. Note that FOV in the angular direction is given by 1/k, which is a function of radial distance from the center. So, angular FOV for high spatial frequencies is smaller than that for low spatial frequencies. However, because the center of k-space is sampled with every projection, full signal amplitude is acquired with all projections. This is different from Cartesian sampling and results in potentially high-signal-intensity streak artifacts, depending on the patient's geometry. kx = Cartesian k-space x-axis, ky = Cartesian k-space y-axis. (b) Short-axis SSFP cine MR images (2.2/1.1; flip angle, 45°) with radial k-space undersampling (top row) versus Cartesian k-space undersampling (bottom row). Characteristic wraparound artifact seen with Cartesian undersampling (arrows, bottom row) is replaced with streak artifact, characteristic of undersampled radial k-space acquisition (arrows, top row). (Adapted and reprinted, with permission, from reference 44.)

SSFP Cine MR Imaging at 3.0 T
Recently, whole-body 3.0-T MR imaging systems have become available, and initial reports suggest they may have a role in cardiac imaging (49–51). There are, however, technical challenges for cardiac MR imaging at 3.0 T, particularly in relation to SSFP cine methods. Radiofrequency uniformity can be a problem at 3.0 T and, relative to 1.5-T imaging, radiofrequency power deposition increases by a factor of four. Therefore, specific-absorption-rate considerations limit the allowable flip angles and the minimum achievable TR. Also, the increased magnetic susceptibility effects at 3.0 T heighten sensitivity to off-resonance artifacts. These factors combine to make SSFP cine imaging more challenging at higher field strengths, because off-resonance (dark-band) artifacts are more troublesome. In the future, intravascular contrast agents may provide an alternative approach for cardiac cine imaging independent of SSFP techniques (52,53) (Fig 5). If the T1 of the blood is short, then spoiled GRE cine imaging with a very short TR becomes practical, with performance characteristics similar to those of SSFP. At the time of writing, however, no intravascular contrast agents have been approved by the Food and Drug Administration for cardiac imaging.

View larger version (104K): [in this window] [in a new window] [Download PPT slide]   Figure 5a: Use of intravascular contrast agent at 3.0-T cine MR imaging in swine model. (a) Before contrast material injection, long-axis SSFP cine MR image (3.2/1.5 msec; flip angle, 55°; bandwidth, 900 Hz/pixel) shows considerable off-resonance artifact (arrows). (b) Also before injection, long-axis spoiled GRE cine image (3.1/1.7 msec; flip angle, 15°; bandwidth, 610 Hz/pixel) shows marked inhomogeneity as a result of blood saturation. (c) After injection of 0.1 mmol/kg Gadomer-17 (Schering, Berlin, Germany), image obtained with same sequence as in b shows uniformly high signal intensity for blood and excellent myocardial definition.

View larger version (146K): [in this window] [in a new window] [Download PPT slide]   Figure 5b: Use of intravascular contrast agent at 3.0-T cine MR imaging in swine model. (a) Before contrast material injection, long-axis SSFP cine MR image (3.2/1.5 msec; flip angle, 55°; bandwidth, 900 Hz/pixel) shows considerable off-resonance artifact (arrows). (b) Also before injection, long-axis spoiled GRE cine image (3.1/1.7 msec; flip angle, 15°; bandwidth, 610 Hz/pixel) shows marked inhomogeneity as a result of blood saturation. (c) After injection of 0.1 mmol/kg Gadomer-17 (Schering, Berlin, Germany), image obtained with same sequence as in b shows uniformly high signal intensity for blood and excellent myocardial definition.

View larger version (142K): [in this window] [in a new window] [Download PPT slide]   Figure 5c: Use of intravascular contrast agent at 3.0-T cine MR imaging in swine model. (a) Before contrast material injection, long-axis SSFP cine MR image (3.2/1.5 msec; flip angle, 55°; bandwidth, 900 Hz/pixel) shows considerable off-resonance artifact (arrows). (b) Also before injection, long-axis spoiled GRE cine image (3.1/1.7 msec; flip angle, 15°; bandwidth, 610 Hz/pixel) shows marked inhomogeneity as a result of blood saturation. (c) After injection of 0.1 mmol/kg Gadomer-17 (Schering, Berlin, Germany), image obtained with same sequence as in b shows uniformly high signal intensity for blood and excellent myocardial definition.

	MYOCARDIAL TAGGING

TOP ABSTRACT INTRODUCTION BLACK-BLOOD ANATOMIC IMAGING CARDIAC CINE IMAGING CINE MR WITH STEADY-STATE... MYOCARDIAL TAGGING FLOW QUANTIFICATION MYOCARDIAL VIABILITY IMAGING:... PERFUSION IMAGING CORONARY ARTERY IMAGING INTRAVASCULAR CONTRAST AGENTS CONCLUSION ESSENTIALS References

Tagging can be used to measure myocardial strain in three dimensions, but quantitative analysis of tagged images is not straightforward. Recently, a fast simplified analysis of tagged images has been proposed (56), whereby strain is calculated by using the Fourier properties of the deformation pattern. In clinical practice, tagged images are usually analyzed subjectively to distinguish between normal and hypokinetic myocardial segments, and to evaluate regional circumferential contraction. A limitation of tagging is that the tag lines fade and the edges blur due to longitudinal relaxation (Fig 6). Tagging with SSFP imaging has recently been described, with advances in speed and SNR as compared with those of spoiled GRE tagging (57); however, clinical experience with this approach is limited at the time of writing. Although extremely powerful as a tool to study cardiac mechanics, the complexity of quantitative analysis limits the use of tagging to the subjective evaluation of wall motion, where it complements cine imaging very well. As a research tool, myocardial tagging has extensive applications.

View larger version (151K): [in this window] [in a new window] [Download PPT slide]   Figure 6a: Short-axis breath-hold spoiled GRE myocardial tagging MR images (15/5; flip angle, 20°; acquisition time, 14 seconds; temporal resolution, 45 msec) obtained (a) 145, (b) 425, and (c) 700 msec after R wave. Note how distortion of tag pattern (arrow) gives insight into motion of myocardial wall. Note also that intensity of tag pattern fades over time, owing to longitudinal relaxation of tagged spins.

View larger version (152K): [in this window] [in a new window] [Download PPT slide]   Figure 6b: Short-axis breath-hold spoiled GRE myocardial tagging MR images (15/5; flip angle, 20°; acquisition time, 14 seconds; temporal resolution, 45 msec) obtained (a) 145, (b) 425, and (c) 700 msec after R wave. Note how distortion of tag pattern (arrow) gives insight into motion of myocardial wall. Note also that intensity of tag pattern fades over time, owing to longitudinal relaxation of tagged spins.

View larger version (139K): [in this window] [in a new window] [Download PPT slide]   Figure 6c: Short-axis breath-hold spoiled GRE myocardial tagging MR images (15/5; flip angle, 20°; acquisition time, 14 seconds; temporal resolution, 45 msec) obtained (a) 145, (b) 425, and (c) 700 msec after R wave. Note how distortion of tag pattern (arrow) gives insight into motion of myocardial wall. Note also that intensity of tag pattern fades over time, owing to longitudinal relaxation of tagged spins.

	FLOW QUANTIFICATION

TOP ABSTRACT INTRODUCTION BLACK-BLOOD ANATOMIC IMAGING CARDIAC CINE IMAGING CINE MR WITH STEADY-STATE... MYOCARDIAL TAGGING FLOW QUANTIFICATION MYOCARDIAL VIABILITY IMAGING:... PERFUSION IMAGING CORONARY ARTERY IMAGING INTRAVASCULAR CONTRAST AGENTS CONCLUSION ESSENTIALS References

View larger version (155K): [in this window] [in a new window] [Download PPT slide]   Figure 7a: Normal aortic valve leaflet motility. Imaging was performed orthogonal to left ventricular outflow tract at the level of aortic valve cusps. (a) SSFP cine (3/1.5; flip angle, 60°; acquisition time, 8 seconds) and (b) phase velocity-encoding (56/2.6; flip angle, 30°; acquisition time, 15 seconds) MR images show normal valve area (arrow). (c) Graphs show flow velocity profiles corresponding to a (left) and b (right).

View larger version (128K): [in this window] [in a new window] [Download PPT slide]   Figure 7b: Normal aortic valve leaflet motility. Imaging was performed orthogonal to left ventricular outflow tract at the level of aortic valve cusps. (a) SSFP cine (3/1.5; flip angle, 60°; acquisition time, 8 seconds) and (b) phase velocity-encoding (56/2.6; flip angle, 30°; acquisition time, 15 seconds) MR images show normal valve area (arrow). (c) Graphs show flow velocity profiles corresponding to a (left) and b (right).

View larger version (13K): [in this window] [in a new window] [Download PPT slide]   Figure 7c: Normal aortic valve leaflet motility. Imaging was performed orthogonal to left ventricular outflow tract at the level of aortic valve cusps. (a) SSFP cine (3/1.5; flip angle, 60°; acquisition time, 8 seconds) and (b) phase velocity-encoding (56/2.6; flip angle, 30°; acquisition time, 15 seconds) MR images show normal valve area (arrow). (c) Graphs show flow velocity profiles corresponding to a (left) and b (right).

View larger version (95K): [in this window] [in a new window] [Download PPT slide]   Figure 8a: Severe aortic stenosis. (a) Breath-hold SSFP cine MR image (3/1.5; flip angle, 60°) through aortic valve shows severe restriction (arrow) in leaflet motion (cf, Fig 6a). (b) Flow quantification image (56/2.6; flip angle, 30°) through the valve. (c, d) Pulsatile flow profiles show greatly increased peak flow velocity of 500 cm/sec (d). Maximum valve area, which is clearly shown and easily quantified with planimetry, was 0.6 cm2, reflecting critical stenosis.

View larger version (89K): [in this window] [in a new window] [Download PPT slide]   Figure 8b: Severe aortic stenosis. (a) Breath-hold SSFP cine MR image (3/1.5; flip angle, 60°) through aortic valve shows severe restriction (arrow) in leaflet motion (cf, Fig 6a). (b) Flow quantification image (56/2.6; flip angle, 30°) through the valve. (c, d) Pulsatile flow profiles show greatly increased peak flow velocity of 500 cm/sec (d). Maximum valve area, which is clearly shown and easily quantified with planimetry, was 0.6 cm2, reflecting critical stenosis.

View larger version (13K): [in this window] [in a new window] [Download PPT slide]   Figure 8c: Severe aortic stenosis. (a) Breath-hold SSFP cine MR image (3/1.5; flip angle, 60°) through aortic valve shows severe restriction (arrow) in leaflet motion (cf, Fig 6a). (b) Flow quantification image (56/2.6; flip angle, 30°) through the valve. (c, d) Pulsatile flow profiles show greatly increased peak flow velocity of 500 cm/sec (d). Maximum valve area, which is clearly shown and easily quantified with planimetry, was 0.6 cm2, reflecting critical stenosis.

	MYOCARDIAL VIABILITY IMAGING: DELAYED CONTRAST ENHANCEMENT

TOP ABSTRACT INTRODUCTION BLACK-BLOOD ANATOMIC IMAGING CARDIAC CINE IMAGING CINE MR WITH STEADY-STATE... MYOCARDIAL TAGGING FLOW QUANTIFICATION MYOCARDIAL VIABILITY IMAGING:... PERFUSION IMAGING CORONARY ARTERY IMAGING INTRAVASCULAR CONTRAST AGENTS CONCLUSION ESSENTIALS References

In recent years, myocardial viability imaging with delayed contrast enhancement has become widely accepted for the detection and characterization of acute and chronic myocardial infarction (76). The improved spatial resolution of MR imaging, compared with that of radionuclide imaging, provides clear advantages, particularly for nontransmural infarction, such that MR imaging is considered by some to outperform nuclear tomography (79–81). The precise mechanisms underlying contrast agent localization in nonviable myocardium are still somewhat controversial, but the phenomenological observation is straightforward. For an overview of the use of contrast agents in cardiac MR, the reader is referred to a recent publication by Edelman (82).

After intravenous injection, an extracellular tracer becomes distributed in the first pass according to myocardial blood flow and in the steady state according to extracellular fluid volume. Because myocardial scar is associated with a larger extracellular fluid volume than is viable myocardium, the steady-state concentration of gadolinium in scar is markedly higher than that in remote (noninfarcted) myocardium. In acute myocardial infarction, abnormal cell-membrane permeability allows free access of diffusible contrast material to the intracellular fluid space, and the apparent distribution volume of the agent may be even higher than that in the scar of chronic infarction. In either case, gadolinium-based agents tend to accumulate in nonviable myocardium within several minutes after intravenous injection and to wash out only slowly. The localization of such agents can be made conspicuous with an appropriate T1-weighted imaging technique, such as segmented k-space inversion-recovery GRE, as detailed by Simonetti et al (83) (Fig 9a). With magnitude reconstruction, the value of the chosen TI is important, because it determines the contrast between remote (viable) and infarcted myocardium. At the optimum TI, the signal from normal myocardium is nulled, while contrast-enhanced tissue is bright, having relaxed past the null point. The correct TI generally lies in the range of 200–300 msec, but this should be confirmed empirically on a patient-specific basis. If the TI is too short, normal myocardium will not be nulled and (with magnitude image reconstruction) positive signal will be generated because the myocardium has not yet relaxed to the null point. This may result in the so-called bounce artifact, where the signal from pixels with negative phase may be indistinguishable from those with positive phase, and pixels between adjacent positive and negative ones are dark (Fig 9b). To complicate matters further, the T1 (and therefore the optimum TI) of remote myocardium changes as the contrast agent is cleared from the blood pool.

View larger version (12K): [in this window] [in a new window] [Download PPT slide]   Figure 9a: (a) Diagram shows segmented k-space inversion-recovery turbo fast low-angle shot (FLASH) MR sequence. After R wave and suitable delay a spatially nonselective inversion pulse is applied, followed the TI. At this point, several lines (in this case, 23) of data are acquired during diastole. Next cardiac cycle is skipped. This pattern is repeated until required number of phase-encoding lines (a multiple of 23) is acquired. TI is generally chosen to null normal myocardium. (b) Effect of TI on regional myocardial signal intensities on 15 short-axis segmented turbo FLASH MR images (TR msec, echo time msec/TI msec, 8/4/110–450 [TI shown on each image]; flip angle, 20°) in a dog. Note transition from low to high signal intensity in anterior infarcted region (arrows) as TI increases. In this case, optimal contrast enhancement was achieved with 275-msec TI, when signal intensity of normal myocardium is nulled. (Reprinted, with permission, from reference 83.)

View larger version (112K): [in this window] [in a new window] [Download PPT slide]   Figure 9b: (a) Diagram shows segmented k-space inversion-recovery turbo fast low-angle shot (FLASH) MR sequence. After R wave and suitable delay a spatially nonselective inversion pulse is applied, followed the TI. At this point, several lines (in this case, 23) of data are acquired during diastole. Next cardiac cycle is skipped. This pattern is repeated until required number of phase-encoding lines (a multiple of 23) is acquired. TI is generally chosen to null normal myocardium. (b) Effect of TI on regional myocardial signal intensities on 15 short-axis segmented turbo FLASH MR images (TR msec, echo time msec/TI msec, 8/4/110–450 [TI shown on each image]; flip angle, 20°) in a dog. Note transition from low to high signal intensity in anterior infarcted region (arrows) as TI increases. In this case, optimal contrast enhancement was achieved with 275-msec TI, when signal intensity of normal myocardium is nulled. (Reprinted, with permission, from reference 83.)

Both implementations of segmented inversion-recovery GRE MR are usually performed as breath-hold techniques, where one section is acquired in about 12 seconds and the whole heart is covered in about 10–12 sections (Fig 10). It is also possible to perform a single three-dimensional breath-hold acquisition to cover the entire heart, albeit with a longer breath hold. A free-breathing version of three-dimensional inversion-recovery GRE sequence has also been described (85), where navigator echoes from the diaphragm are used for respiratory gating. The various implementations of delayed contrast-enhanced inversion-recovery GRE work comparably well when used appropriately. The selection of the version to use may be a matter of personal choice, vendor platform, or availability.

View larger version (112K): [in this window] [in a new window] [Download PPT slide]   Figure 10a: Myocardial infarction. Breath-hold two-dimensional segmented inversion-recovery turbo fast low-angle shot MR images (2000/5/300; flip angle, 10°) obtained in vertical (a) long- and (b, c) short-axis orientations show subendocardial delayed hyperenhancement in anteroseptal (arrow) and inferoseptal (arrowhead) walls.

View larger version (107K): [in this window] [in a new window] [Download PPT slide]   Figure 10b: Myocardial infarction. Breath-hold two-dimensional segmented inversion-recovery turbo fast low-angle shot MR images (2000/5/300; flip angle, 10°) obtained in vertical (a) long- and (b, c) short-axis orientations show subendocardial delayed hyperenhancement in anteroseptal (arrow) and inferoseptal (arrowhead) walls.

View larger version (106K): [in this window] [in a new window] [Download PPT slide]   Figure 10c: Myocardial infarction. Breath-hold two-dimensional segmented inversion-recovery turbo fast low-angle shot MR images (2000/5/300; flip angle, 10°) obtained in vertical (a) long- and (b, c) short-axis orientations show subendocardial delayed hyperenhancement in anteroseptal (arrow) and inferoseptal (arrowhead) walls.

More recently, variants of SSFP have been successfully used to address myocardial hyperenhancement imaging of viability. Inversion-recovery SSFP can be performed as a single-shot technique within a heartbeat or as a segmented technique that can also be used to detect intracardiac thrombus (Fig 11), in a manner similar to that for segmented inversion-recovery GRE. Because, in this context, the bandwidth for SSFP is several-fold wider than that for GRE, more lines of data can be captured in the same amount of time. Also, because the SSFP readout perturbs the longitudinal relaxation only slightly (88), it is possible to sample several images with different TIs throughout the cardiac cycle and to choose the single optimum TI for subsequent use (89). This process, sometimes referred to as TI surfing can be used as an alternative or a complement to phase-sensitive reconstruction (Fig 12).

View larger version (143K): [in this window] [in a new window] [Download PPT slide]   Figure 11a: Bland thrombus in a patient with atrial fibrillation. Oblique coronal (a) SSFP cine (3/1.5; flip angle, 60°) and (b) gadolinium-enhanced two-dimensional segmented inversion-recovery SSFP (2000/1.5/300; flip angle, 60°) MR images show nonenhancing thrombus (arrow) in left atrial appendage.

View larger version (158K): [in this window] [in a new window] [Download PPT slide]   Figure 11b: Bland thrombus in a patient with atrial fibrillation. Oblique coronal (a) SSFP cine (3/1.5; flip angle, 60°) and (b) gadolinium-enhanced two-dimensional segmented inversion-recovery SSFP (2000/1.5/300; flip angle, 60°) MR images show nonenhancing thrombus (arrow) in left atrial appendage.

View larger version (19K): [in this window] [in a new window] [Download PPT slide]   Figure 12a: (a) Diagram of MR survey sequence to determine correct TI (TI surfing). After a single inversion pulse, series of images are read out during T1 relaxation. Depending on how long after the inversion pulse a specific readout is centered, magnetization will have relaxed to a variable degree. Time at which normal myocardium passes through the null point will be noted as that readout time when its signal is minimized. This works best for SSFP-based techniques. (b) SSFP MR images for TI surfing (2000/1.5/150–350 [TI shown on each image]; flip angle, 60°) for correct TI after contrast agent administration. Because enhanced blood pool has short T1, it is nulled with short TI (150 msec). At this point, phase of normal myocardium is still negative, but myocardium appears bright on magnitude images. By 250 msec, myocardium has reached the zero point and continues to recover at later TIs. In this case, optimal TI for magnitude reconstruction is 250 msec.

View larger version (33K): [in this window] [in a new window] [Download PPT slide]   Figure 12b: (a) Diagram of MR survey sequence to determine correct TI (TI surfing). After a single inversion pulse, series of images are read out during T1 relaxation. Depending on how long after the inversion pulse a specific readout is centered, magnetization will have relaxed to a variable degree. Time at which normal myocardium passes through the null point will be noted as that readout time when its signal is minimized. This works best for SSFP-based techniques. (b) SSFP MR images for TI surfing (2000/1.5/150–350 [TI shown on each image]; flip angle, 60°) for correct TI after contrast agent administration. Because enhanced blood pool has short T1, it is nulled with short TI (150 msec). At this point, phase of normal myocardium is still negative, but myocardium appears bright on magnitude images. By 250 msec, myocardium has reached the zero point and continues to recover at later TIs. In this case, optimal TI for magnitude reconstruction is 250 msec.

	PERFUSION IMAGING

TOP ABSTRACT INTRODUCTION BLACK-BLOOD ANATOMIC IMAGING CARDIAC CINE IMAGING CINE MR WITH STEADY-STATE... MYOCARDIAL TAGGING FLOW QUANTIFICATION MYOCARDIAL VIABILITY IMAGING:... PERFUSION IMAGING CORONARY ARTERY IMAGING INTRAVASCULAR CONTRAST AGENTS CONCLUSION ESSENTIALS References

 
The potential of MR contrast agents for imaging of myocardial perfusion was suggested in the late 1980s (91,92). Although perfusion can be measured in isolated hearts with arterial spin labeling and without contrast agents (93), there are as yet few reports on its clinical applications (94). The initial reports of myocardial perfusion MR imaging in humans performed with first-pass contrast enhancement were published in the early 1990s (95,96). Atkinson et al (95) used a T1-weighted single-shot inversion-recovery turbo fast low-angle shot technique to capture an image in each heart cycle during bolus intravenous injection of gadolinium-based contrast material. Since then, workers have applied various T1 preparation pulses and readout schemes, but the basic approach is still the same. Currently, magnetization preparation with either inversion (180° pulse) or saturation (90° pulse) is followed by a very fast spoiled GRE acquisition or a short-echo-train (segmented) echo-planar readout. Advances in hardware and pulse sequences have generated a variety of improvements in imaging speed, such that multisection acquisition within a heartbeat by using a saturation prepulse is now standard (97–101).

The authors of several clinical reports have endorsed the accuracy of dynamic myocardial perfusion MR imaging, mostly in combination with adenosine or dipyridamole stress (102). In one article from 2003 (103), an accuracy on the order of 90% was reported for detection of angiographically significant coronary artery disease by using first-pass perfusion MR imaging with inversion-recovery SSFP. Nonetheless, the task of capturing the first pass of a contrast agent bolus with sufficient spatial resolution and absence of artifact is challenging (104). Moreover, variability in the shape of the bolus because of the patient's hemodynamics makes standardization difficult, even with sophisticated processing (100,105). Recent work with SSFP perfusion methods (103,106) and parallel-acquisition echo-planar imaging (101) have produced positive results, with some improvement over the results achievable with existing methods.

A report published in 2003 (107) highlights promising results with a new class of manganese-based MR contrast agent that can be studied in the steady state. The ability to image the steady-state distribution of a perfusion agent rather than during its first pass would offer a definite advantage. An alternative technique, blood oxygenation level–dependent MR imaging, has recently been described in a dog model (108). This approach also involves the use of multishot high-spatial-resolution imaging and, if sufficiently sensitive, would represent an important advance. However, clinical results with blood oxygenation level–dependent imaging are not yet available.

	CORONARY ARTERY IMAGING

TOP ABSTRACT INTRODUCTION BLACK-BLOOD ANATOMIC IMAGING CARDIAC CINE IMAGING CINE MR WITH STEADY-STATE... MYOCARDIAL TAGGING FLOW QUANTIFICATION MYOCARDIAL VIABILITY IMAGING:... PERFUSION IMAGING CORONARY ARTERY IMAGING INTRAVASCULAR CONTRAST AGENTS CONCLUSION ESSENTIALS References

 
MR imaging of native coronary arteries is difficult because of cardiac and respiratory motion, the size and tortuosity of the coronary arteries, and the distance of the arteries from surface coils. The caliber of the proximal coronary arteries rarely exceeds 5 mm in healthy humans. The spatial displacement of coronary arteries during the heart cycle is on the order of 1–2 cm, and the peak velocities are more than 20 cm/sec during certain phases, such as rapid cardiac contraction and relaxation (11).

All current MR methods for imaging the coronary arteries use an ECG-triggered segmented three-dimensional data acquisition (Fig 13). During each heartbeat, several phase-encoding steps are acquired during middiastole. Data collected over several consecutive heartbeats are used to cover one plane of k-space. This process is repeated until the entire three-dimensional k-space is covered.

View larger version (10K): [in this window] [in a new window] [Download PPT slide]   Figure 13: Diagram shows three-dimensional (3D) coronary artery MR sequence. Images are built sequentially by adding groups of in-plane and through-plane phase-encoding steps until sufficient heartbeats have registered. NAV = navigator echo, TD = interval between R wave and magnetization preparation pulse.

View larger version (163K): [in this window] [in a new window] [Download PPT slide]   Figure 14a: Coronary artery MR imaging with respiratory gating. Respiratory motion is tracked with navigator echoes. (a) Coronal chest MR scout localizer image shows lung-liver interface. (b) Temporal display of multiple navigator echoes shows diaphragmatic motion. Data are accepted only if acquired within acceptance window defined by diaphragm position.

View larger version (103K): [in this window] [in a new window] [Download PPT slide]   Figure 14b: Coronary artery MR imaging with respiratory gating. Respiratory motion is tracked with navigator echoes. (a) Coronal chest MR scout localizer image shows lung-liver interface. (b) Temporal display of multiple navigator echoes shows diaphragmatic motion. Data are accepted only if acquired within acceptance window defined by diaphragm position.

View larger version (89K): [in this window] [in a new window] [Download PPT slide]   Figure 15a: Whole-heart three-dimensional SSFP coronary MR angiography (3.3/1.5; flip angle, 90°; bandwidth, 975 Hz/pixel). Near isotropic resolution (<1 mm3), high blood-to-muscle contrast, and good fat suppression enable clear delineation of left and right coronary arteries on (a) reformatted and (b) volume-rendered images.

View larger version (89K): [in this window] [in a new window] [Download PPT slide]   Figure 15b: Whole-heart three-dimensional SSFP coronary MR angiography (3.3/1.5; flip angle, 90°; bandwidth, 975 Hz/pixel). Near isotropic resolution (<1 mm3), high blood-to-muscle contrast, and good fat suppression enable clear delineation of left and right coronary arteries on (a) reformatted and (b) volume-rendered images.

View larger version (12K): [in this window] [in a new window] [Download PPT slide]   Figure 16: Diagram of segmented three-dimensional SSFP coronary MR sequence. T2 preparation (T2prep) is optional. Also, depending on whether respiratory gating is used, navigator echo (NAV) is optional. These are followed by fat-suppression (FS) pulse, linearly increasing flip-angle SSFP dummy cycles (Prep), and data acquisition. Radiofrequency (rf) and gradient events (GSS, GPE, GRO) and readout (ADC) during single TR are shown at the bottom.

View larger version (123K): [in this window] [in a new window] [Download PPT slide]   Figure 17a: Breath-hold three-dimensional SSFP (3.8/1.4; flip angle, 90°) MR imaging of normal coronary arteries. Maximum intensity projections show (a) left anterior descending (arrow), (b) right (arrow), and (c) circumflex (arrow) coronary arteries. Breath-hold time for each orientation was approximately 23 seconds.

View larger version (111K): [in this window] [in a new window] [Download PPT slide]   Figure 17b: Breath-hold three-dimensional SSFP (3.8/1.4; flip angle, 90°) MR imaging of normal coronary arteries. Maximum intensity projections show (a) left anterior descending (arrow), (b) right (arrow), and (c) circumflex (arrow) coronary arteries. Breath-hold time for each orientation was approximately 23 seconds.

View larger version (105K): [in this window] [in a new window] [Download PPT slide]   Figure 17c: Breath-hold three-dimensional SSFP (3.8/1.4; flip angle, 90°) MR imaging of normal coronary arteries. Maximum intensity projections show (a) left anterior descending (arrow), (b) right (arrow), and (c) circumflex (arrow) coronary arteries. Breath-hold time for each orientation was approximately 23 seconds.

View larger version (140K): [in this window] [in a new window] [Download PPT slide]   Figure 18a: Respiratory-gated SSFP (3.8/1.4; flip angle, 90°) MR images. Compare with Figure 15. (a) Left anterior descending (arrow), (b) right (arrow), and (c) circumflex (arrow) coronary arteries are well shown. Acquisition time for each vessel was approximately 5 minutes.

View larger version (133K): [in this window] [in a new window] [Download PPT slide]   Figure 18b: Respiratory-gated SSFP (3.8/1.4; flip angle, 90°) MR images. Compare with Figure 15. (a) Left anterior descending (arrow), (b) right (arrow), and (c) circumflex (arrow) coronary arteries are well shown. Acquisition time for each vessel was approximately 5 minutes.

View larger version (118K): [in this window] [in a new window] [Download PPT slide]   Figure 18c: Respiratory-gated SSFP (3.8/1.4; flip angle, 90°) MR images. Compare with Figure 15. (a) Left anterior descending (arrow), (b) right (arrow), and (c) circumflex (arrow) coronary arteries are well shown. Acquisition time for each vessel was approximately 5 minutes.

	INTRAVASCULAR CONTRAST AGENTS

TOP ABSTRACT INTRODUCTION BLACK-BLOOD ANATOMIC IMAGING CARDIAC CINE IMAGING CINE MR WITH STEADY-STATE... MYOCARDIAL TAGGING FLOW QUANTIFICATION MYOCARDIAL VIABILITY IMAGING:... PERFUSION IMAGING CORONARY ARTERY IMAGING INTRAVASCULAR CONTRAST AGENTS CONCLUSION ESSENTIALS References

	CONCLUSION

TOP ABSTRACT INTRODUCTION BLACK-BLOOD ANATOMIC IMAGING CARDIAC CINE IMAGING CINE MR WITH STEADY-STATE... MYOCARDIAL TAGGING FLOW QUANTIFICATION MYOCARDIAL VIABILITY IMAGING:... PERFUSION IMAGING CORONARY ARTERY IMAGING INTRAVASCULAR CONTRAST AGENTS CONCLUSION ESSENTIALS References

 
Cardiac MR imaging, although still evolving rapidly, has matured to the point where it is now a powerful tool with a range of clinical and research applications. For evaluation of complex anatomy, cardiac function, myocardial viability, valvular disease, myocardial perfusion, and congenital heart disease, MR imaging may be especially effective. Although recent advances in multisection computed tomography present a serious challenge to MR imaging with regard to the assessment of coronary artery anatomy, it is likely that MR imaging will meet the challenge through continued developments in machine hardware, pulse sequences, motion compensation, and the use of novel contrast agents.

	ESSENTIALS

TOP ABSTRACT INTRODUCTION BLACK-BLOOD ANATOMIC IMAGING CARDIAC CINE IMAGING CINE MR WITH STEADY-STATE... MYOCARDIAL TAGGING FLOW QUANTIFICATION MYOCARDIAL VIABILITY IMAGING:... PERFUSION IMAGING CORONARY ARTERY IMAGING INTRAVASCULAR CONTRAST AGENTS CONCLUSION ESSENTIALS References

 

• Breath-hold cine MR imaging with steady-state free precession (SSFP) has become the standard for combined anatomic and functional imaging of the heart.
  
• Imaging of myocardial delayed contrast enhancement has arguably become the new standard for in vivo MR imaging of myocardial scar and assessment of myocardial viability.
  
• Perfusion MR imaging continues to evolve in quality and reliability and is most effectively performed with pharmacologic stress.
  
• Coronary artery MR imaging with a three-dimensional SSFP sequence continues to evolve in both breath-hold and free-breathing implementations, even without the use of intravenous contrast agents.
  
• Parallel imaging techniques may increase the performance of the entire spectrum of pulse sequences used for cardiac MR imaging.
  

	FOOTNOTES

 

Abbreviations: ECG = electrocardiographic • GRE = gradient recalled echo • SNR = signal-to-noise ratio • TI = inversion time • TR = repetition time

	References

TOP ABSTRACT INTRODUCTION BLACK-BLOOD ANATOMIC IMAGING CARDIAC CINE IMAGING CINE MR WITH STEADY-STATE... MYOCARDIAL TAGGING FLOW QUANTIFICATION MYOCARDIAL VIABILITY IMAGING:... PERFUSION IMAGING CORONARY ARTERY IMAGING INTRAVASCULAR CONTRAST AGENTS CONCLUSION ESSENTIALS References

 

1. Boxerman JL, Mosher TJ, McVeigh ER, Atalar E, Lima JA, Bluemke DA. Advanced MR imaging techniques for evaluation of the heart and great vessels. RadioGraphics 1998;18:543–564.[Abstract]
2. Poon M, Fuster V, Fayad Z. Cardiac magnetic resonance imaging: a "one-stop-shop" evaluation of myocardial dysfunction. Curr Opin Cardiol 2002;17:663–670.[CrossRef][Medline]
3. Fletcher BD, Jacobstein MD, Nelson AD, Riemenschneider TA, Alfidi RJ. Gated magnetic resonance imaging of congenital cardiac malformations. Radiology 1984;150(1):137–140.[Abstract/Free Full Text]
4. van Dijk P. ECG-triggered NMR imaging of the heart. Diagn Imaging Clin Med 1984;53:29–37.[Medline]
5. Lanzer P, Barta C, Botvinick EH, Wiesendanger HU, Modin G, Higgins CB. ECG-synchronized cardiac MR imaging: method and evaluation. Radiology 1985;155:681–686.[Abstract/Free Full Text]
6. Higgins CB, Stark D, McNamara M, Lanzer P, Crooks LE, Kaufman L. Multiplane magnetic resonance imaging of the heart and major vessels: studies in normal volunteers. AJR Am J Roentgenol 1984;142:661–667.[Abstract/Free Full Text]
7. Lieberman JM, Botti RE, Nelson AD. Magnetic resonance imaging of the heart. Radiol Clin North Am 1984;22:847–858.[Medline]
8. Waterton JC, Jenkins JP, Zhu XP, Love HG, Isherwood I, Rowlands DJ. Magnetic resonance (MR) cine imaging of the human heart. Br J Radiol 1985;58:711–716.[Abstract/Free Full Text]
9. Alfidi RJ, Masaryk TJ, Haacke EM, et al. MR angiography of peripheral, carotid, and coronary arteries. AJR Am J Roentgenol 1987;149:1097–1109.[Free Full Text]
10. Higgins CB. MRI of heart disease. Int J Card Imaging 1987;2:259–265.[CrossRef][Medline]
11. Paulin S, von Schulthess GK, Fossel E, Krayenbuehl HP. MR imaging of the aortic root and proximal coronary arteries. AJR Am J Roentgenol 1987;148:665–670.[Abstract/Free Full Text]
12. Bluemke DA, Krupinski EA, Ovitt T, et al. MR Imaging of arrhythmogenic right ventricular cardiomyopathy: morphologic findings and interobserver reliability. Cardiology 2003;99:153–162.[CrossRef][Medline]
13. Bomma C, Rutberg J, Tandri H, et al. Misdiagnosis of arrhythmogenic right ventricular dysplasia/cardiomyopathy. J Cardiovasc Electrophysiol 2004;15:300–306.[Medline]
14. Edelman RR, Chien D, Kim D. Fast selective black blood MR imaging. Radiology 1991;181:655–660.[Abstract/Free Full Text]
15. Atkinson DJ, Edelman RR. Cineangiography of the heart in a single breath hold with a segmented turboFLASH sequence. Radiology 1991;178:357–360.[Abstract/Free Full Text]
16. Simonetti OP, Finn JP, White RD, Laub G, Henry DA. "Black blood" T2-weighted inversion-recovery MR imaging of the heart. Radiology 1996;199:49–57.[Abstract/Free Full Text]
17. Hennig J, Nauerth A, Friedburg H. RARE imaging: a fast imaging method for clinical MR. Magn Reson Med 1986;3:823–833.[Medline]
18. Stehling MK, Holzknecht NG, Laub G, Bohm D, von Smekal A, Reiser M. Single-shot T1- and T2-weighted magnetic resonance imaging of the heart with black blood: preliminary experience. MAGMA 1996;4:231–240.[CrossRef][Medline]
19. Glover GH, Pelc NJ. A rapid-gated cine MRI technique. Magn Reson Annu 1988;299–333.
20. Sechtem U, Pflugfelder PW, Cassidy MM, et al. Mitral or aortic regurgitation: quantification of regurgitant volumes with cine MR imaging. Radiology 1988;167:425–430.[Abstract/Free Full Text]
21. Firmin DN, Nayler GL, Klipstein RH, Underwood SR, Rees RS, Longmore DB. In vivo validation of MR velocity imaging. J Comput Assist Tomogr 1987;11:751–756.[Medline]
22. Firmin DN, Nayler GL, Kilner PJ, Longmore DB. The application of phase shifts in NMR for flow measurement. Magn Reson Med 1990;14:230–241.[Medline]
23. Underwood SR, Firmin DN, Rees RS, Longmore DB. Magnetic resonance velocity mapping. Clin Phys Physiol Meas 1990;11(suppl A):37–43.[Medline]
24. Edelman RR, Manning WJ, Gervino E, Li W. Flow velocity quantification in human coronary arteries with fast, breath-hold MR angiography. J Magn Reson Imaging 1993;3:699–703.[Medline]
25. Mackey ES, Sandler MP, Campbell RM, et al. Right ventricular myocardial mass quantification with magnetic resonance imaging. Am J Cardiol 1990;65:529–532.[CrossRef][Medline]
26. Sechtem U, Pflugfelder P, Higgins CB. Quantification of cardiac function by conventional and cine magnetic resonance imaging. Cardiovasc Intervent Radiol 1987;10:365–373.[Medline]
27. Semelka RC, Tomei E, Wagner S, et al. Normal left ventricular dimensions and function: interstudy reproducibility of measurements with cine MR imaging. Radiology 1990;174:763–768.[Abstract/Free Full Text]
28. Lund JT, Ehman RL, Julsrud PR, Sinak LJ, Tajik AJ. Cardiac masses: assessment by MR imaging. AJR Am J Roentgenol 1989;152:469–473.[Abstract/Free Full Text]
29. Young AA, Cowan BR, Thrupp SF, Hedley WJ, Dell'Italia LJ. Left ventricular mass and volume: fast calculation with guide-point modeling on MR images. Radiology 2000;216:597–602.[Abstract/Free Full Text]
30. Laub GA. Time-of-flight method of MR angiography. Magn Reson Imaging Clin N Am 1995;3:391–398.[Medline]
31. Oppelt A, Graumann R, Barfuss H. FISP: a new fast MRI sequence. Electromedica 1986;54:15–18.
32. Deimling M, Heid O. Magnetization prepared TrueFISP imaging [abstract]. In: Proceedings of the First/Second Meeting of the Society of Magnetic Resonance. Berkeley, Calif: Society of Magnetic Resonance, 1994; 495.
33. Bundy J, Simonetti O, Laub G, Finn, P. TrueFISP imaging of the heart [abstract]. In: Proceedings of the Seventh Meeting of the International Society for Magnetic Resonance in Medicine. Berkeley, Calif: International Society for Magnetic Resonance in Medicine, 1999; 1282.
34. Carr JC, Simonetti O, Bundy J, Li D, Pereles S, Finn JP. Cine MR angiography of the heart with segmented true fast imaging with steady-state precession. Radiology 2001;219:828–834.[Abstract/Free Full Text]
35. Barkhausen J, Ruehm SG, Goyen M, Buck T, Laub G, Debatin JF. MR evaluation of ventricular function: true fast imaging with steady-state precession versus fast low-angle shot cine MR imaging—feasibility study. Radiology 2001;219:264–269.[Abstract/Free Full Text]
36. Francois CJ, Fieno DS, Shors SM, Finn JP. Left ventricular mass: manual and automatic segmentation of true FISP and FLASH cine MR images in dogs and pigs. Radiology 2004;230(2):389–395.[Abstract/Free Full Text]
37. Shors SM, Fung CW, Francois CJ, Finn JP, Fieno DS. Accurate quantification of right ventricular mass at MR imaging by using cine true fast imaging with steady-state precession: study in dogs. Radiology 2004;230(2):383–388.[Abstract/Free Full Text]
38. Li W, Storey P, Chen Q, Li BS, Prasad PV, Edelman RR. Dark flow artifacts with steady-state free precession cine MR technique: causes and implications for cardiac MR imaging. Radiology 2004;230(2):569–575.[Abstract/Free Full Text]
39. Sodickson DK, Manning WJ. Simultaneous acquisition of spatial harmonics (SMASH): fast imaging with radiofrequency coil arrays. Magn Reson Med 1997;38:591–603.[Medline]
40. Jakob PM, Griswold MA, Edelman RR, Manning WJ, Sodickson DK. Accelerated cardiac imaging using the SMASH technique. J Cardiovasc Magn Reson 1999;1:153–157.[Medline]
41. Wintersperger BJ, Nikolaou K, Dietrich O, et al. Single breath-hold real-time cine MR imaging: improved temporal resolution using generalized autocalibrating partially parallel acquisition (GRAPPA) algorithm. Eur Radiol 2003;13:1931–1936.[CrossRef][Medline]
42. Griswold MA, Jakob PM, Heidemann RM, et al. Generalized autocalibrating partially parallel acquisitions (GRAPPA). Magn Reson Med 2002;47:1202–1210.[CrossRef][Medline]
43. Pruessmann KP, Weiger M, Scheidegger MB, Boesiger P. SENSE: sensitivity encoding for fast MRI. Magn Reson Med 1999;42:952–962.[CrossRef][Medline]
44. Shankaranarayanan A, Simonetti OP, Laub G, Lewin JS, Duerk JL. Segmented k-space and real-time cardiac cine MR imaging with radial trajectories. Radiology 2001;221:827–836.[Abstract/Free Full Text]
45. Lee VS, Resnick D, Bundy JM, Simonetti OP, Lee P, Weinreb JC. Cardiac function: MR evaluation in one breath hold with real-time true fast imaging with steady-state precession. Radiology 2002;222:835–842.[Abstract/Free Full Text]
46. Larson AC, Simonetti OP. Real-time cardiac cine imaging with SPIDER: steady-state projection imaging with dynamic echo-train readout. Magn Reson Med 2001;46:1059–1066.[CrossRef][Medline]
47. Larson AC, White RD, Laub G, McVeigh ER, Li D, Simonetti OP. Self-gated cardiac cine MRI. Magn Reson Med 2004;51:93–102.[CrossRef][Medline]
48. Tsao J, Kozerke S, Boesiger P, Pruessmann KP. Optimizing spatiotemporal sampling for k-t BLAST and k-t SENSE: application to high-resolution real-time cardiac steady-state free precession. Magn Reson Med 2005;53:1372–1382.[CrossRef][Medline]
49. Michaely HJ, Nael K, Schoenberg SO, et al. Analysis of cardiac function: comparison between 1.5 tesla and 3.0 tesla cardiac cine magnetic resonance imaging—preliminary experience. Invest Radiol 2006;41:133–140.[CrossRef][Medline]
50. Wintersperger BJ, Bauner K, Reeder SB, et al. Cardiac steady-state free precession CINE magnetic resonance imaging at 3.0 tesla: impact of parallel imaging acceleration on volumetric accuracy and signal parameters. Invest Radiol 2006;41:141–147.[CrossRef][Medline]
51. Gutberlet M, Noeske R, Schwinge K, Freyhardt P, Felix R, Niendorf T. Comprehensive cardiac magnetic resonance imaging at 3.0 tesla: feasibility and implications for clinical applications. Invest Radiol 2006;41:154–167.[CrossRef][Medline]
52. Misselwitz B, Schmitt-Willich H, Ebert W, Frenzel T, Weinmann HJ. Pharmacokinetics of Gadomer-17, a new dendritic magnetic resonance contrast agent. MAGMA 2001;12:128–134.[CrossRef][Medline]
53. Fonseca CG, Nael K, Weinmann HJ, Nyborg GK, Laub G, Finn JP. Cardiac cine MRI at 3.0T: initial experience with gadomer-17 in a swine model [abstract]. In: Proceedings of the 14th Meeting of the International Society for Magnetic Resonance in Medicine. Berkeley, Calif: International Society for Magnetic Resonance in Medicine, 2006; 6.
54. Zerhouni EA, Parish DM, Rogers WJ, Yang A, Shapiro EP. Human heart: tagging with MR imaging—a method for noninvasive assessment of myocardial motion. Radiology 1988;169:59–63.[Abstract/Free Full Text]
55. McVeigh ER, Atalar E. Cardiac tagging with breath-hold cine MRI. Magn Reson Med 1992;28:318–327.[Medline]
56. Osman NF, Kerwin WS, McVeigh ER, Prince JL. Cardiac motion tracking using CINE harmonic phase (HARP) magnetic resonance imaging. Magn Reson Med 1999;42:1048–1060.[CrossRef][Medline]
57. Herzka DA, Guttman MA, McVeigh ER. Myocardial tagging with SSFP. Magn Reson Med 2003;49:329–340.[CrossRef][Medline]
58. Stahlberg F, Nordell B, Ericsson A, et al. Method for quantification of low flow velocities by magnetic resonance phase imaging. Acta Radiol Suppl 1986;369:486–489.
59. Matthaei D, Haase A, Merboldt KD, Hanicke W, Deimling M. ECG-triggered arterial FLASH-MR flow measurement using an external standard. Magn Reson Imaging 1987;5:325–330.[CrossRef][Medline]
60. Kilner PJ, Firmin DN, Rees RS, et al. Valve and great vessel stenosis: assessment with MR jet velocity mapping. Radiology 1991;178:229–235.[Abstract/Free Full Text]
61. Mitchell L, Jenkins JP, Watson Y, Rowlands DJ, Isherwood I. Diagnosis and assessment of mitral and aortic valve disease by cine-flow magnetic resonance imaging. Magn Reson Med 1989;12:181–197.[Medline]
62. Hundley WG, Li HF, Willard JE, et al. Magnetic resonance imaging assessment of the severity of mitral regurgitation: comparison with invasive techniques. Circulation 1995;92:1151–1158.[Abstract/Free Full Text]
63. Hartiala JJ, Foster E, Fujita N, et al. Evaluation of left atrial contribution to left ventricular filling in aortic stenosis by velocity-encoded cine MRI. Am Heart J 1994;127:593–600.[CrossRef][Medline]
64. Boxt LM. Magnetic resonance and computed tomographic evaluation of congenital heart disease. J Magn Reson Imaging 2004;19:827–847.[CrossRef][Medline]
65. Kruger S, Haage P, Hoffmann R, et al. Diagnosis of pulmonary arterial hypertension and pulmonary embolism with magnetic resonance angiography. Chest 2001;120:1556–1561.[Abstract/Free Full Text]
66. Frank H, Globits S, Glogar D, Neuhold A, Kneussl M, Mlczoch J. Detection and quantification of pulmonary artery hypertension with MR imaging: results in 23 patients. AJR Am J Roentgenol 1993;161:27–31.[Abstract/Free Full Text]
67. Murray TI, Boxt LM, Katz J, Reagan K, Barst RJ. Estimation of pulmonary artery pressure in patients with primary pulmonary hypertension by quantitative analysis of magnetic resonance images. J Thorac Imaging 1994;9:198–204.[Medline]
68. Hofman MB, van Rossum AC, Sprenger M, Westerhof N. Assessment of flow in the right human coronary artery by magnetic resonance phase contrast velocity measurement: effects of cardiac and respiratory motion. Magn Reson Med 1996;35:521–531.[Medline]
69. van Dijkman PR, Doornbos J, de Roos A, et al. Improved detection of acute myocardial infarction by magnetic resonance imaging using gadolinium-DTPA. Int J Card Imaging 1989;5:1–8.[CrossRef][Medline]
70. van Dijkman PR, van der Wall EE, de Roos A, et al. Gadolinium-enhanced magnetic resonance imaging in acute myocardial infarction. Eur J Radiol 1990;11:1–9.[CrossRef][Medline]
71. van der Wall EE, van Dijkman PR, de Roos A, et al. Diagnostic significance of gadolinium-DTPA (diethylenetriamine penta-acetic acid) enhanced magnetic resonance imaging in thrombolytic treatment for acute myocardial infarction: its potential in assessing reperfusion. Br Heart J 1990;63:12–17.[Abstract/Free Full Text]
72. Saeed M, Wagner S, Wendland MF, Derugin N, Finkbeiner WE, Higgins CB. Occlusive and reperfused myocardial infarcts: differentiation with Mn-DPDP–enhanced MR imaging. Radiology 1989;172:59–64.[Abstract/Free Full Text]
73. Lima JA, Judd RM, Bazille A, Schulman SP, Atalar E, Zerhouni EA. Regional heterogeneity of human myocardial infarcts demonstrated by contrast-enhanced MRI: potential mechanisms. Circulation 1995;92:1117–1125.[Abstract/Free Full Text]
74. Judd RM, Kim RJ. Imaging time after Gd-DTPA injection is critical in using delayed enhancement to determine infarct size accurately with magnetic resonance imaging. Circulation 2002;106:e6.[Free Full Text]
75. Judd RM, Lugo-Olivieri CH, Arai M, et al. Physiological basis of myocardial contrast enhancement in fast magnetic resonance images of 2-day-old reperfused canine infarcts. Circulation 1995;92:1902–1910.[Abstract/Free Full Text]
76. Kim RJ, Wu E, Rafael A, et al. The use of contrast-enhanced magnetic resonance imaging to identify reversible myocardial dysfunction. N Engl J Med 2000;343:1445–1453.[Abstract/Free Full Text]
77. Kim RJ, Shah DJ, Judd RM. How we perform delayed enhancement imaging. J Cardiovasc Magn Reson 2003;5:505–514.[CrossRef][Medline]
78. Kim RJ, Chen EL, Lima JA, Judd RM. Myocardial Gd-DTPA kinetics determine MRI contrast enhancement and reflect the extent and severity of myocardial injury after acute reperfused infarction. Circulation 1996;94:3318–3326.[Abstract/Free Full Text]
79. Klein C, Nekolla SG, Bengel FM, et al. Assessment of myocardial viability with contrast-enhanced magnetic resonance imaging: comparison with positron emission tomography. Circulation 2002;105:162–167.[Abstract/Free Full Text]
80. Wagner A, Mahrholdt H, Holly TA, et al. Contrast-enhanced MRI and routine single photon emission computed tomography (SPECT) perfusion imaging for detection of subendocardial myocardial infarcts: an imaging study. Lancet 2003;361:374–379.[CrossRef][Medline]
81. Lee VS, Resnick D, Tiu SS, et al. MR imaging evaluation of myocardial viability in the setting of equivocal SPECT results with ^99mTc sestamibi. Radiology 2004;230(1):191–197.[Abstract/Free Full Text]
82. Edelman RR. Contrast-enhanced MR imaging of the heart: overview of the literature. Radiology 2004;232(3):653–668.[Abstract/Free Full Text]
83. Simonetti OP, Kim RJ, Fieno DS, et al. An improved MR imaging technique for the visualization of myocardial infarction. Radiology 2001;218:215–223.[Abstract/Free Full Text]
84. Kellman P, Arai AE, McVeigh ER, Aletras AH. Phase-sensitive inversion recovery for detecting myocardial infarction using gadolinium-delayed hyperenhancement. Magn Reson Med 2002;47:372–383.[CrossRef][Medline]
85. Saranathan M, Rochitte CE, Foo TK. Fast, three-dimensional free-breathing MR imaging of myocardial infarction: a feasibility study. Magn Reson Med 2004;51:1055–1060.[CrossRef][Medline]
86. Oshinski JN, Yang Z, Jones JR, Mata JF, French BA. Imaging time after Gd-DTPA injection is critical in using delayed enhancement to determine infarct size accurately with magnetic resonance imaging. Circulation 2001;104:2838–2842.[Abstract/Free Full Text]
87. Thomson LE, Kim RJ, Judd RM. Magnetic resonance imaging for the assessment of myocardial viability. J Magn Reson Imaging 2004;19:771–788.[CrossRef][Medline]
88. Scheffler K, Hennig J. T(1) quantification with inversion recovery TrueFISP. Magn Reson Med 2001;45:720–723.[CrossRef][Medline]
89. Shea SM, Deshpande VS, Chung YC, Li D. Three-dimensional true-FISP imaging of the coronary arteries: improved contrast with T2-preparation. J Magn Reson Imaging 2002;15:597–602.[CrossRef][Medline]
90. Hundley WG, Morgan TM, Neagle CM, Hamilton CA, Rerkpattanapipat P, Link KM. Magnetic resonance imaging determination of cardiac prognosis. Circulation 2002;106:2328–2333.[Abstract/Free Full Text]
91. Brown JJ, Higgins CB. Myocardial paramagnetic contrast agents for MR imaging. AJR Am J Roentgenol 1988;151:865–871.[Abstract/Free Full Text]
92. Miller DD, Holmvang G, Gill JB, et al. MRI detection of myocardial perfusion changes by gadolinium-DTPA infusion during dipyridamole hyperemia. Magn Reson Med 1989;10:246–255.[Medline]
93. Williams DS, Grandis DJ, Zhang W, Koretsky AP. Magnetic resonance imaging of perfusion in the isolated rat heart using spin inversion of arterial water. Magn Reson Med 1993;30:361–365.[Medline]
94. Wacker CM, Fidler F, Dueren C, et al. Quantitative assessment of myocardial perfusion with a spin-labeling technique: preliminary results in patients with coronary artery disease. J Magn Reson Imaging 2003;18:555–560.[CrossRef][Medline]
95. Atkinson DJ, Burstein D, Edelman RR. First-pass cardiac perfusion: evaluation with ultrafast MR imaging. Radiology 1990;174:757–762.[Abstract/Free Full Text]
96. Burstein D. MR imaging of coronary artery flow in isolated and in vivo hearts. J Magn Reson Imaging 1991;1:337–346.[Medline]
97. Wilke N, Jerosch-Herold M, Wang Y, et al. Myocardial perfusion reserve: assessment with multisection, quantitative, first-pass MR imaging. Radiology 1997;204:373–384.[Abstract/Free Full Text]
98. Buonocore MH. Visualizing blood flow patterns using streamlines, arrows, and particle paths. Magn Reson Med 1998;40:210–226.[Medline]
99. Jerosch-Herold M, Wilke N, Stillman AE. Magnetic resonance quantification of the myocardial perfusion reserve with a Fermi function model for constrained deconvolution. Med Phys 1998;25:73–84.[CrossRef][Medline]
100. Jerosch-Herold M, Swingen C, Seethamraju RT. Myocardial blood flow quantification with MRI by model-independent deconvolution. Med Phys 2002;29:886–897.[CrossRef][Medline]
101. Kellman P, Derbyshire JA, Agyeman KO, McVeigh ER, Arai AE. Extended coverage first-pass perfusion imaging using slice-interleaved TSENSE. Magn Reson Med 2004;51:200–204.[CrossRef][Medline]
102. Al-Saadi N, Nagel E, Gross M, et al. Noninvasive detection of myocardial ischemia from perfusion reserve based on cardiovascular magnetic resonance. Circulation 2000;101:1379–1383.[Abstract/Free Full Text]
103. Chiu CW, So NM, Lam WW, Chan KY, Sanderson JE. Combined first-pass perfusion and viability study at MR imaging in patients with non-ST segment-elevation acute coronary syndromes: feasibility study. Radiology 2003;226:717–722.[Abstract/Free Full Text]
104. Burstein D, Taratuta E, Manning WJ. Factors in myocardial "perfusion" imaging with ultrafast MRI and Gd-DTPA administration. Magn Reson Med 1991;20:299–305.[Medline]
105. Dale BM, Jesberger JA, Lewin JS, Hillenbrand CM, Duerk JL. Determining and optimizing the precision of quantitative measurements of perfusion from dynamic contrast enhanced MRI. J Magn Reson Imaging 2003;18:575–584.[CrossRef][Medline]
106. Fenchel M, Helber U, Simonetti OP, et al. Multislice first-pass myocardial perfusion imaging: comparison of saturation recovery (SR)-TrueFISP-two-dimensional (2D) and SR-TurboFLASH-2D pulse sequences. J Magn Reson Imaging 2004;19:555–563.[CrossRef][Medline]
107. Storey P, Danias PG, Post M, et al. Preliminary evaluation of EVP 1001-1: a new cardiac-specific magnetic resonance contrast agent with kinetics suitable for steady-state imaging of the ischemic heart. Invest Radiol 2003;38:642–652.[Medline]
108. Fieno DS, Shea SM, Li Y, Harris KR, Finn JP, Li D. Myocardial perfusion imaging based on the blood oxygen level-dependent effect using T2-prepared steady-state free-precession magnetic resonance imaging. Circulation 2004;110:1284–1290.[Abstract/Free Full Text]
109. Botnar RM, Stuber M, Danias PG, Kissinger KV, Manning WJ. Improved coronary artery definition with T2-weighted, free-breathing, three-dimensional coronary MRA. Circulation 1999;99:3139–3148.[Abstract/Free Full Text]
110. Weber OM, Martin AJ, Higgins CB. Whole-heart steady-state free precession coronary artery magnetic resonance angiography. Magn Reson Med 2003;50:1223–1228.[CrossRef][Medline]
111. Deshpande VS, Shea SM, Laub G, Simonetti OP, Finn JP, Li D. 3D magnetization-prepared true-FISP: a new technique for imaging coronary arteries. Magn Reson Med 2001;46:494–502.[CrossRef][Medline]
112. Deshpande VS, Chung YC, Zhang Q, Shea SM, Li D. Reduction of transient signal oscillations in true-FISP using a linear flip angle series magnetization preparation. Magn Reson Med 2003;49:151–157.[CrossRef][Medline]
113. Nishimura DG, Vasanawala S. Analysis and reduction of the transient response in SSFP imaging [abstract]. In: Proceedings of the Eighth Meeting of the International Society for Magnetic Resonance in Medicine. Berkeley, Calif: International Society for Magnetic Resonance in Medicine, 2000; 301.
114. Huber ME, Paetsch I, Schnackenburg B, et al. Performance of a new gadolinium-based intravascular contrast agent in free-breathing inversion-recovery 3D coronary MRA. Magn Reson Med 2003;49:115–121.[CrossRef][Medline]
115. Bedaux WL, Hofman MB, Wielopolski PA, et al. Three-dimensional magnetic resonance coronary angiography using a new blood pool contrast agent: initial experience. J Cardiovasc Magn Reson 2002;4:273–282.[CrossRef][Medline]

This article has been cited by other articles:

				G. B. Chavhan, P. S. Babyn, B. G. Jankharia, H.-L. M. Cheng, and M. M. Shroff Steady-State MR Imaging Sequences: Physics, Classification, and Clinical Applications RadioGraphics, July 1, 2008; 28(4): 1147 - 1160. [Abstract] [Full Text] [PDF]

This Article Abstract Figures Only Full Text (PDF) Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Finn, J. P. Articles by Laub, G. Search for Related Content PubMed PubMed Citation Articles by Finn, J. P. Articles by Laub, G.