Radiology
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Published online before print July 29, 2004, 10.1148/radiol.2323031225
This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
2323031225v1
232/3/669    most recent
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Jahnke, C.
Right arrow Articles by Nagel, E.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Jahnke, C.
Right arrow Articles by Nagel, E.
(Radiology 2004;232:669-676.)
© RSNA, 2004

Cardiac Imaging

Coronary MR Angiography with Steady-State Free Precession: Individually Adapted Breath-hold Technique versus Free-breathing Technique1

Cosima Jahnke, MD, Ingo Paetsch, MD, Bernhard Schnackenburg, PhD, Axel Bornstedt, PhD, Rolf Gebker, MD, Eckart Fleck, MD and Eike Nagel, MD

1 From the Department of Internal Medicine/Cardiology, German Heart Institute, Berlin, Germany. Received August 1, 2003; revision requested October 3; final revision received December 29; accepted January 15, 2004. Supported by a grant from the Stifterverband für die Deutsche Wissenschaft. C.J. supported by a research grant from the German Cardiac Society. Address correspondence to C.J., Department of Cardiology, University of Freiburg, Hugstetter Str 55, 79106 Freiburg, Germany (e-mail: jahnke@med1.ukl.uni-freiburg.de).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
RESULTS
DISCUSSION
 REFERENCES
 
PURPOSE: To compare image quality and coronary artery stenosis detection with breath-hold (BH) and free-breathing navigator-gated (NAV) coronary magnetic resonance (MR) angiography performed with the same imaging sequence (steady-state free precession) and identical spatial resolution in patients suspected of having coronary artery disease.

MATERIALS AND METHODS: Forty consecutive patients suspected of having coronary artery disease underwent steady-state free precession MR imaging of the left or the right coronary artery twice. Correction of breathing motion was performed once with NAV and again with BH. Maximal BH duration and coronary artery rest period were individually determined, and duration of data acquisition was adapted (parallel imaging with different sensitivity encoding factors was used). Quantitative analysis of coronary MR angiography data was performed with multiplanar reformatting software to determine visual score for image quality, vessel sharpness, visible vessel length, and number of visible side branches. Diagnostic accuracy for detection of coronary stenosis of 50% or greater was determined in comparison with results of conventional invasive angiography. The two techniques were compared regarding differences in angiographic parameters with paired Student t testing. {chi}2 or Fisher exact testing was used when appropriate.

RESULTS: More coronary artery segments were assessable with NAV than with BH MR angiography (254 [79.4%] vs 143 [44.7%] of 320 segments). Overall sensitivity and specificity with NAV were 72% (26 of 36 segments) and 91.7% (200 of 218 segments), versus 63% (12 of 19 segments) and 82.3% (102 of 124 segments) with BH; NAV enabled correct diagnosis in 13% more segments. BH yielded nondiagnostic images in 14 patients, while NAV yielded diagnostic images in all patients. When these 14 patients were excluded, there was a significant increase in visual score for left (3.0 vs 2.4, P < .01) and right (3.3 vs 3.0, P < .05) coronary arteries and no significant difference in vessel sharpness but significant improvement in visible vessel length in left coronary artery (85.9 vs 71.4 mm, P = .003) and number of visible side branches in left (4.9 vs 3.9, P = .04) and right (2.8 vs 2.4, P = .04) coronary arteries on NAV images as compared with BH images.

CONCLUSION: Free-breathing NAV was superior to BH coronary MR angiography in terms of image quality and diagnostic accuracy of stenosis detection.

© RSNA, 2004

Index terms: Coronary vessels, MR, 54.12142 • Coronary vessels, stenosis or obstruction, 54.76 • Magnetic resonance (MR), motion correction, 54.12142 • Magnetic resonance (MR), vascular studies, 54.12142


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
 REFERENCES
 
In the past decade, coronary magnetic resonance (MR) angiography has emerged as a noninvasive tool for diagnosing coronary artery disease (1,2). Although coronary MR angiography has been evolving rapidly (3–5), visualization of the whole coronary arterial tree with reproducibly high diagnostic image quality remains challenging. One of the major problems of coronary MR imaging is the effective suppression of respiratory motion. Two approaches have been proposed to compensate for respiratory motion in coronary imaging (6–8): breath-hold (BH) imaging and free-breathing navigator-gated (NAV) imaging. To date, clinical trials have mostly involved the use of two-dimensional BH (1,9) or three-dimensional retrospective NAV (10–12) approaches for respiratory compensation. More recently, three-dimensional BH techniques (13,14) and free-breathing respiratory-gated techniques with a prospective navigator algorithm (15) have been introduced and have led to improved image quality. In patients, BH capability is often limited, resulting in short BH periods and diaphragmatic drift. Thus, NAV techniques have been developed, and their use has been reported as being advantageous for patients (16).

Shortening of the image acquisition duration might also help overcome the limitations of BH imaging. Such shortening can be achieved with the use of parallel imaging techniques (eg, sensitivity encoding [17]), which are especially beneficial in combination with the newer flow-independent steady-state free precession sequences. First reports on steady-state free precession sequences for coronary MR angiography are promising (18,19), owing to the high signal-to-noise ratio (SNR) and the intrinsically high contrast yielded by these sequences (20,21). Additionally, the use of steady-state free precession sequences, with their inherently high blood pool signal, has further improved vessel border definition (19,22).

To our knowledge, no direct comparison of a BH approach with a free-breathing approach has yet been performed by using identical sequences. Thus, the objective of the present study was to compare image quality and coronary artery stenosis detection with BH and NAV techniques by using the same MR imaging sequence (steady-state free precession) and identical spatial resolution in patients clinically suspected of having coronary artery disease.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
DISCUSSION
 REFERENCES
 
Subjects
Forty consecutive patients (mean age, 62.4 years; age range, 38–86 years) were examined. There were 24 men (mean age, 61.9 years; age range, 38–86 years) and 16 women (mean age, 63.2 years; age range, 44–77 years). All patients were scheduled to undergo diagnostic coronary angiography because of a clinical suspicion of coronary artery disease. Patients were included in the study during a period of about 2 months (from January 15, 2003 to March 18, 2003). Patients with contraindications to MR imaging (eg, those who had cardiac pacemakers or other ferromagnetic implants or claustrophobia) were excluded from the study. Written informed consent was obtained from all patients, and the study was approved by the ethics committee of the Virchow Klinikum und Charité, Berlin, Germany.

MR Imaging
All patients were examined in the supine position by using a 1.5-T whole-body MR imaging system (Intera CV 1.5 T; Philips, Best, the Netherlands) equipped with a PowerTrak6000 gradient system (23 mT/m, 219-µsec rise time) and specifically designed software (Release 9). A five-element cardiac synergy coil was used for signal detection. Cardiac synchronization was performed by using four electrodes placed on the left anterior portion of the hemithorax (so that a vector electrocardiogram could be obtained), and image acquisitions were triggered on the R-wave of the electrocardiogram (23). A rapid gradient-echo sequence (a multistack multisection survey with steady-state free precession; repetition time msec/echo time msec, 4.0/1.3; flip angle, 55°) was used to determine the location of the heart in the three standard planes (transverse, sagittal, and coronal).

Subsequently, a fast NAV and navigator-corrected (15) transverse low-spatial-resolution three-dimensional steady-state free precession sequence (3.4/1.3; flip angle, 70°) was performed in the target region with the navigator (with a 5-mm gating window) positioned on the dome of the right hemidiaphragm. By using an imaging sequence (cine steady-state free precession, retrospective gating, 40 phases per cardiac cycle) with a transverse section orientation, the rest periods of the left coronary artery (LCA) and the right coronary artery (RCA) were individually determined after a region of interest was placed on the cross section of the artery. The rest period was defined as the duration of time when the movement of the coronary artery was less than 25% of its cross-sectional area. The region of interest was always placed by the same observer (C.J.), and the exact same defined rest period was used for both the NAV and the BH coronary MR imaging sequences.

Individual BH capability was measured during end-expiratory BH with a dynamic navigator sequence (temporal resolution, 1 second). Thereafter, coronary MR angiography of the LCA or the RCA (randomly selected) was performed twice. Correction of breathing motion was performed once with the NAV approach and once with the BH approach (in random order). The examinations were limited to one coronary artery system (LCA or RCA) to achieve an acceptable total examination duration for all consecutive patients.

BH MR imaging.—BH MR imaging was performed during one end-expiratory BH without navigator correction: The acquisition duration per heartbeat was adapted with regard to the individual rest period of the coronary artery, with a predefined maximum of 150 msec. Increasing the sensitivity encoding reduction factor (range, 1.5–5.0) enabled us to adapt the total imaging duration to the patient’s BH capability (Fig 1). Twenty overcontiguous sections were obtained by using a flow-independent steady-state free precession sequence (4.5/2.3; flip angle, 90°) with a fat-suppression and T2 preparation prepulse (24,25). In-plane spatial resolution was 1.3 x 1.3 mm with a 3-mm section thickness.



View larger version (15K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 1. The course of the coronary MR angiographic examination. RR = R-R interval (in milliseconds), SENSE = sensitivity encoding, TR = repetition time (in milliseconds).

 
The three-point "planscan tool" in the MR imaging system software was used for planning the optimal imaging plane of the coronary sequence as follows (15): For the LCA, the first reference point was the origin of the left main artery, the second reference point was a distal point of the left anterior descending (LAD) artery, and the third reference point was chosen in the middle-to-distal portion of the left circumflex (LCX) segment. For the RCA, three reference points along the main axis of the vessel were indicated.

Free-breathing NAV MR imaging.—The identical procedure with the same spatial resolution was performed for the NAV approach, without using sensitivity encoding. Correction of breathing motion was performed with a real-time prospective navigator (15,26) that had a gating window of 5 mm and a correction factor of 0.6 and that was placed on the dome of the right hemidiaphragm to relate the superoinferior position of the diaphragm to the superoinferior position of the proximal coronary arteries (8). Navigator efficiency was defined as the number of accepted NAV acquisitions divided by the total number of navigator acquisitions (values are given as percentages).

Image Analysis
The following 16 segments of the coronary arteries were evaluated for stenosis with reference to the suggested American College of Cardiology/American Heart Association guidelines (27): the left main segment, the proximal segment of the LAD artery, the middle segment of the LAD artery, the distal segment of the LAD artery, the first diagonal branch of the LAD artery, the second diagonal branch of the LAD artery, the proximal segment of the LCX artery, the middle segment of the LCX artery, the distal segment of the LCX artery, the first marginal branch of the LCX artery, the second marginal branch of the LCX artery, the proximal segment of the RCA, the middle segment of the RCA, the distal segment of the RCA, the right posterolateralis segment, and the posterolateral descending artery segment.

Each coronary artery segment was classified as being able to be evaluated or as being impossible to evaluate (meaning that the segment was not visible); impossible-to-evaluate segments were not considered in the analysis of diagnostic ratings. The segments that were classified as being able to be evaluated were classified as having either significant (≥50% reduction in diameter) stenosis or occlusion or no significant stenosis or occlusion at visual assessment. The appearance of a reduction in segmental diameter or a loss of signal intensity on MR images was considered to be indicative of a significant coronary artery stenosis or occlusion (2–4). Analysis of the MR coronary angiograms was performed in a random manner and in consensus by two observers with 1 (C.J.) and 5 (I.P.) years of experience in cardiac MR imaging. The readers were blinded to the MR imaging technique used and were not aware of the conventional coronary angiography results.

A visual score was used to grade the visibility of the coronary arteries as follows: A grade of 1 indicated that artery visibility was poor or the image was uninterpretable (the artery was visible but had markedly blurred borders); a grade of 2, that artery visibility was good (the artery was visible and had moderately blurred borders); a grade of 3, that artery visibility was very good (the artery was visible and had mildly blurred borders); and a grade of 4, that artery visibility was excellent (the artery was visible and had sharply defined borders) (4).

The visual score was determined in consensus by the same two readers (C.J., I.P.) who had evaluated the images for stenosis and who were blinded to patient data and to the technique used to obtain a given MR image. For objective assessment of vessel sharpness, a previously published dedicated quantitative coronary analysis tool with an edge-detection and vessel sharpness algorithm was applied to the raw data (28,29). Vessel sharpness was defined as the average signal intensity along the vessel border on the edge image, with higher values indicating better vessel delineation (24). The values were determined for the first 4 cm of the proximal segments of the LCA (left main artery and LAD artery) and the RCA. For quantification of angiographic parameters and visualization of coronary artery anatomy, multiplanar reformatting of the three-dimensional data set was performed with the same dedicated quantitative coronary analysis software to facilitate measurement of vessel length and assessment of the number of visible side branches. All quantitative angiographic parameters were assessed by the same reader (C.J.).

Conventional Coronary Angiography
All patients underwent conventional invasive coronary angiography within 3 weeks after MR imaging. Conventional coronary angiography was performed by using the transfemoral Judkins approach, with selective catheterization of the LCA and RCA systems in multiple projections. Visual assessment of the angiograms was performed by a highly experienced interventionalist (E.F., with ≥25 years of experience in performing cardiac catheterization) who was not involved in the coronary MR imaging examinations and who was blinded to the MR imaging data at the time of the readings. Diameter reductions exceeding 50% were considered to represent relevant stenoses.

Subgrouping
For further analysis, the patient population was divided retrospectively into subgroups by using the following criteria: Subgroup 1 consisted of patients requiring a sensitivity encoding factor of 3.5 or less at BH imaging, and subgroup 2 consisted of patients with optimal image quality (visual score = 4) during BH imaging. In addition, a statistical analysis was performed to verify differences in all quantitative parameters and BH capability with regard to age and sex: The patient population was classified into male and female groups and into a group of patients who were less than 65 years of age and a group of patients who were 65 years of age or older.

Statistical Analysis
Statistical analysis was performed by using the SPSS software package, release 11.01 (SPSS, Chicago, Ill). For all continuous parameters, means ± standard deviations are given. Analysis for statistical differences between the two MR imaging techniques was performed as follows: Group differences were tested for continuous variables by using the paired Student t test and for categorical variables by using the Wilcoxon test. A contingency analysis with a {chi}2 or Fisher exact test was used to calculate sensitivity, specificity, and diagnostic accuracy; to assess statistical significance, analysis of variance was used. Group differences for age and sex were analyzed by using the unpaired Student t test for all continuous variables and the Mann-Whitney U test for all categorical variables. All tests were two-tailed; P < .05 was considered to indicate a statistically significant difference.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
DISCUSSION
 REFERENCES
 
Sequence Duration and Navigator Efficiency
The mean nominal sequence duration was 94.8 seconds ± 20.9 for the NAV approach. Depending on the navigator efficiencies, the effective sequence duration had a wide range of variability (100.2–674.3 seconds) and was significantly longer at NAV imaging in comparison to BH imaging (Table 1). At BH imaging, the mean sensitivity encoding factor was 3.2 ± 1.0. Table 2 shows the possible BH durations at coronary MR angiography with a sensitivity encoding factor of 2.0 according to the individual rest period of the coronary artery and the heart rate.


View this table:
[in this window]
[in a new window]

  		TABLE 1. Imaging Characteristics of BH and NAV Techniques

 

View this table:
[in this window]
[in a new window]

  		TABLE 2. BH Duration according to Individual Heart Rate and Coronary Artery Rest Period

 
MR Angiographic Parameters
With the BH approach, the mean overall visual score was 2.0 ± 1.0 for the LCA system and 2.2 ± 1.1 for the RCA system. NAV coronary artery imaging, as compared with BH coronary artery imaging, resulted in a significant increase in mean overall visual score for the LCA and RCA systems (3.0 ± 0.6 [P < .01] and 3.2 ± 0.6 [P < .01], respectively). Quantitative MR angiographic parameters are supplied in Table 3. For both the LCA and the RCA, the visible vessel length and the number of visible side branches increased significantly when the free-breathing NAV technique was used. There was a significant increase in vessel sharpness with the NAV approach as well (Table 3, Fig 2).


View this table:
[in this window]
[in a new window]

  		TABLE 3. Quantitative Angiographic Parameters at BH and NAV MR Imaging in Different Patient Groups

 


View larger version (175K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 2. Images in 69-year-old woman. A, B, Multiplanar reformatted MR images (4.5/2.3, 90° flip angle) of LCA system acquired with NAV and BH (sensitivity encoding factor, 2.7) approaches. Note improved delineation of vessel border of LCA system in NAV image. Increased visibility of the LCX and coronary side branches on the NAV image can be appreciated. C, D, Multiplanar reformatted MR images (4.5/2.3, 90° flip angle) of RCA acquired with BH (sensitivity encoding factor, 2.6) and NAV approaches. Note the improved image quality beyond the crux of the RCA on the NAV image. Ao = aorta, LM = left main artery.

 
Conventional Coronary Angiography
At conventional invasive coronary angiography, 25 (62%) of 40 patients had significant coronary artery disease: Five (12%) of the 40 patients had one-vessel disease, 11 (28%) had two-vessel disease, and nine (22%) had three-vessel disease.

Diagnostic Accuracy of Coronary MR Angiography
With BH imaging, 177 (55.3%) of 320 coronary artery segments had to be excluded from further analysis owing to poor image quality (Table 4). In the remaining 143 segments, 12 of 19 significant coronary artery stenoses or occlusions and the absence of significant stenoses in 102 of 124 segments were correctly identified. Sensitivity, specificity, and diagnostic accuracy with each of the two techniques are listed in Table 4.


View this table:
[in this window]
[in a new window]

  		TABLE 4. Results of Evaluation of Coronary Artery Stenoses at BH and NAV MR Imaging

 
With the NAV approach, 66 (20.6%) of 320 coronary artery segments could not be evaluated owing to impaired image quality. In the 254 segments that could be evaluated, 26 of 36 significant coronary artery stenoses or occlusions and the absence of significant stenoses in 200 of 218 segments were correctly identified (Table 4, Fig 3). Consequently, with the NAV approach, 13% more coronary artery segments were correctly classified.



View larger version (130K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 3. A-C, Images in 72-year-old woman. Both, A, NAV, and, B, BH (sensitivity encoding factor, 2.3) multiplanar reformatted coronary MR angiograms (4.5/2.3, 90° flip angle) show significant stenosis (white arrow) of the middle portion of the LAD artery. C, Conventional coronary angiogram confirms 75% stenosis (arrow) of the LAD artery. Note that the three-dimensional coronary MR angiographic data set displays the findings of biplane conventional coronary angiography in one imaging plane. D-F, Images in 58-year-old man. Both, D, NAV, and, E, BH (sensitivity encoding factor, 2.8) coronary MR angiograms show midarterial stenosis (white arrow) in the identical location in the RCA of the same patient. F, Conventional coronary angiogram shows 75% stenosis (arrow) of the midportion of the RCA. Ao = aorta, Cath = catheter.

 
Age- and Sex-specific Analysis
The study population was divided into patients less than 65 years of age (n = 19) and patients 65 years or older (n = 21) and into male (n = 24) and female (n = 16) groups. There were no statistically significant differences in terms of age distribution between the male and female subgroups (P = .69). Statistical analysis of all quantitative parameters of image quality, as well as BH capability, revealed no significant difference between groups.

Subgroup 1
The NAV approach allowed visualization of the epicardial coronary arteries in all patients. The BH approach yielded nondiagnostic images in 14 patients (35%) owing to a relative SNR (SNRr)—calculated as SNRr = (SNRSENSEI · 100)/SNR0, where SNRSENSEI is the SNR with the individual sensitivity encoding factor and SNR0 is the SNR of the non–sensitivity encoding sequence—of less than 45% (sensitivity encoding factor, >3.5). After these 14 patients were excluded, the remaining 26 patients formed subgroup 1 (Fig 4). In subgroup 1, the mean sensitivity encoding factor was 2.5 ± 0.5 (mean sequence duration, 25.7 seconds ± 4.7). For the LCA system, the mean visual score with the BH approach was 2.4 ± 0.9, versus 3.0 ± 0.6 with the NAV approach (P < .01). For the RCA system, the mean visual score with the BH approach was 3.0 ± 0.5, versus 3.3 ± 0.6 for the NAV approach (P < .05). Quantitative MR angiographic parameters are shown in Table 3. For both the LCA and RCA systems, the visible vessel length and the number of visible side branches were significantly greater with the free-breathing NAV approach, but no significant difference in vessel sharpness was demonstrated. Of a total of 214 coronary artery segments, 71 were considered nonassessable with the BH approach and 43 were considered nonassessable with the NAV approach; hence, 143 (66.8%) coronary segments could be evaluated with the BH technique and 171 (79.9%) could be evaluated with the NAV technique.



View larger version (28K):
[in this window]
[in a new window]
[Download PPT slide]
  		Figure 4. Diagram shows classification of patient population into subgroups 1 and 2. Subgroup 1 consisted of patients (pts.) with a relative SNR of 45% or greater, in whom coronary MR angiography with the BH approach was deemed to yield images of reasonable quality. Subgroup 2 consisted of those patients in subgroup 1 in whom BH imaging yielded excellent visualization (visual score = 4).

 
Subgroup 2
BH images of seven patients obtained with a mean sensitivity encoding factor of 2.0 ± 0.5 and a mean sequence duration of 31.9 seconds ± 2.4 were given a visual score of 4 (excellent) (Fig 4). NAV images obtained in these seven patients also were given a visual score of 4. Quantitative MR angiographic parameters for subgroup 2 are provided in Table 3. Owing to the small number of patients in this subgroup, no statistical analyses were performed.


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
DISCUSSION
REFERENCES
 
In the present study, we compared individually adapted BH coronary MR angiography with free-breathing NAV coronary MR angiography by using steady-state free precession sequences. We found parameters of image quality to be superior with prospective NAV imaging. At comparison of the BH technique with the NAV technique, we found that the NAV technique enabled the correct diagnosis of 13% more coronary segments, resulting in higher diagnostic accuracy. BH image quality is mainly influenced by the limited data acquisition duration, which depends on the individual BH capability and coronary artery rest period of the patient. Consequently, the ability to acquire BH coronary MR angiograms of reasonable quality is restricted in a relevant proportion of patients owing to the required BH duration.

For this study, a low-spatial-resolution sequence (1.3 x 1.3 x 3 mm) was chosen to make BH possible for most patients. Even though spatial resolution can be better when navigator techniques are used and the ability to obtain images with submillimeter spatial resolution has been reported (24,30), our choice to use a lower resolution was based on reports of successful coronary MR angiography being performed with a low-spatial-resolution sequence (31–33) and the restrictions for maximal BH duration.

For both approaches—BH and free-breathing NAV—the rest period of the imaged coronary artery was individually determined and used to define the acquisition duration per heartbeat. The acquisition duration was limited to a maximum of 150 msec per heartbeat because a longer acquisition duration leads to an increase in vessel blurring, especially in the distal segments of the coronary arteries, owing to extensive movement. Additionally, the signal decrease during the acquisition is acceptable (<30%) when an acquisition duration shorter than 150 msec is used. In combination with the individual BH capability of each patient, the sensitivity encoding factor could be determined for optimal adaptation of the total length of data acquisition to the patient’s characteristics.

The use of sensitivity encoding factors greater than 3.5 results in a decrease in the SNR to less than 45% of the SNR on images acquired without sensitivity encoding factors. In 14 (35%) of the 40 patients in the present study, the individually designed BH imaging protocol required the use of a sensitivity encoding factor greater than 3.5 because of an insufficient BH capability and/or a short coronary artery rest period and resulted in nondiagnostic MR images. This group of patients would obviously profit most from the use of the NAV approach, and diagnostic images could be obtained with this alternative technique in all patients.

Subgroup 1 included all patients (n = 26) in whom the physiologic parameters allowed us to perform BH imaging that yielded images of reasonable quality. Even in this group, the NAV approach resulted in superior image quality, higher diagnostic yield, and better diagnostic accuracy, with 13% more correctly diagnosed coronary segments. This difference can be attributed to the better image quality yielded with the NAV approach.

In a previous study by Kessler et al (32) in which BH and NAV coronary artery MR imaging were compared, no significant differences in image quality between the two techniques were found. In this study, however, lower spatial resolution was allowed with the BH but not with the NAV approach. A second study by the same investigators (34) resulted in slightly better diagnostic accuracy with both techniques as compared with our results; however, that study was restricted to proximal and middle coronary segments only. In that study, the NAV approach was inferior to the BH approach because a retrospective navigator, which has been described as a less favorable navigator technique, was used (15).

Subgroup 2 in the present study consisted of seven patients (18% of the total of 40 patients) who had an excellent visual score at BH imaging. In these patients, BH and free-breathing NAV MR imaging yielded images of similar quality at quantitative evaluation. Subgroup 2 was characterized by a favorable BH capability (mean, 31.9 seconds ± 2.4) in combination with longer coronary artery rest periods. This group did not profit when NAV MR imaging was performed with the spatial resolution chosen in this study. Differences, however, may occur if imaging with higher spatial resolution is attempted.

In our study, no attempt was made to differentiate between significant stenoses and total occlusions of coronary arteries. Because partial volume effects may cause a subtotal stenosis to appear as a total occlusion, it may be impossible to determine whether such a coronary lesion represents a subtotal stenosis or a total occlusion with filling of the distal segments by collateral flow. No grading of the coronary stenosis was attempted with MR imaging. At present, even a submillimeter spatial resolution at coronary MR angiography is insufficient to enable one to determine the exact degree of coronary stenosis and may also contribute to low sensitivity. Similarly, the degree of stenosis was estimated visually on conventional coronary angiograms, without the use of quantitative coronary artery analysis. Currently, coronary MR angiography should be used for either the detection or the exclusion of coronary artery disease and thus the decision of whether or not to proceed to invasive angiography. Thus, stenosis grading is of less importance, since no decision regarding the type and extent of treatment is made.

Low-spatial-resolution coronary artery MR images obtained with steady-state free precession were nondiagnostic in 14 (35%) of 40 patients when the BH technique was used, whereas they were diagnostic in 100% (40 of 40) of patients when the free-breathing NAV technique was used. The free-breathing NAV technique was superior to the BH technique and enabled a correct diagnosis in 13% more coronary segments—even in patients with a more favorable combination of BH capability and coronary artery rest period. Only in a group of seven patients (18% of the total of 40 patients) who had optimal BH capability and long coronary artery rest periods did the BH and free-breathing NAV techniques yield similar results. Consequently, individual determination of BH capability and coronary artery rest period is essential for choosing the adequate breathing-motion suppression technique when image quality and economy of time are also considerations.


   ACKNOWLEDGMENTS
 
We thank Marc Kouwenhoven, PhD, for technical input and constructive criticism.


   FOOTNOTES
 
Authors stated no financial relationship to disclose.

Abbreviations: BH = breath hold, LAD = left anterior descending, LCA = left coronary artery, LCX = left circumflex, NAV = navigator gated, RCA = right coronary artery, SNR = signal-to-noise ratio

Author contributions: Guarantors of integrity of entire study, C.J., E.N.; study concepts, E.N., I.P.; study design, C.J.; literature research, C.J., R.G., B.S.; clinical studies, C.J., R.G.; data acquisition and analysis/interpretation, C.J., B.S., A.B.; statistical analysis, C.J., B.S.; manuscript preparation, C.J., I.P., E.N.; manuscript definition of intellectual content, I.P., E.N.; manuscript editing, C.J., I.P.; manuscript revision/review, E.F.; manuscript final version approval, E.N., E.F.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
DISCUSSION
 REFERENCES
 

  1. Duerinckx AJ, Urman MK. Two-dimensional coronary MR angiography: analysis of initial clinical results. Radiology 1994; 193:731-738.[Abstract/Free Full Text]
  2. Manning WJ, Li W, Edelman RR. A preliminary report comparing magnetic resonance coronary angiography with conventional angiography. N Engl J Med 1993; 328:828-832.[Abstract/Free Full Text]
  3. Pennell DJ, Keegan J, Firmin DN, Gatehouse PD, Underwood SR, Longmore DB. Magnetic resonance imaging of coronary arteries: technique and preliminary results. Br Heart J 1993; 70:315-326.[Abstract/Free Full Text]
  4. Kim WY, Danias PG, Stuber M, et al. Coronary magnetic resonance angiography for the detection of coronary stenoses. N Engl J Med 2001; 345:1863-1869.[Abstract/Free Full Text]
  5. Li D, Kaushikkar S, Haacke EM, et al. Coronary arteries: three-dimensional MR imaging with retrospective respiratory gating. Radiology 1996; 201:857-863.[Abstract/Free Full Text]
  6. Edelman RR, Manning WJ, Burstein D, Paulin S. Coronary arteries: breath-hold MR angiography. Radiology 1991; 181:641-643.[Abstract/Free Full Text]
  7. McConnell MV, Khasgiwala VC, Savord BJ, et al. Prospective adaptive navigator correction for breath-hold MR coronary angiography. Magn Reson Med 1997; 37:148-152.[Medline]
  8. Wang Y, Riederer SJ, Ehman RL. Respiratory motion of the heart: kinematics and the implications for the spatial resolution in coronary imaging. Magn Reson Med 1995; 33:713-719.[Medline]
  9. Post JC, van Rossum AC, Hofman MB, de Cock CC, Valk J, Visser CA. Clinical utility of two-dimensional magnetic resonance angiography in detecting coronary artery disease. Eur Heart J 1997; 18:426-433.[Abstract/Free Full Text]
  10. Post JC, van Rossum AC, Hofman MB, Valk J, Visser CA. Three-dimensional respiratory-gated MR angiography of coronary arteries: comparison with conventional coronary angiography. AJR Am J Roentgenol 1996; 166:1399-1404.[Abstract/Free Full Text]
  11. Muller MF, Fleisch M, Kroeker R, Chatterjee T, Meier B, Vock P. Proximal coronary artery stenosis: three-dimensional MRI with fat saturation and navigator echo. J Magn Reson Imaging 1997; 7:644-651.[Medline]
  12. Sandstede JJ, Pabst T, Beer M, et al. Three-dimensional MR coronary angiography using the navigator technique compared with conventional coronary angiography. AJR Am J Roentgenol 1999; 172:135-139.[Abstract/Free Full Text]
  13. Goldfarb JW, Edelman RR. Coronary arteries: breath-hold, gadolinium-enhanced, three-dimensional MR angiography. Radiology 1998; 206:830-834.[Abstract/Free Full Text]
  14. Regenfus M, Ropers D, Achenbach S, et al. Noninvasive detection of coronary artery stenosis using contrast-enhanced three-dimensional breath-hold magnetic resonance coronary angiography. J Am Coll Cardiol 2000; 36:44-50.[Abstract/Free Full Text]
  15. Stuber M, Botnar RM, Danias PG, et al. Double-oblique free-breathing high resolution three-dimensional coronary magnetic resonance angiography. J Am Coll Cardiol 1999; 34:524-531.[Abstract/Free Full Text]
  16. Taylor AM, Keegan J, Jhooti P, Gatehouse PD, Firmin DN, Pennell DJ. Differences between normal subjects and patients with coronary artery disease for three different MR coronary angiography respiratory suppression techniques. J Magn Reson Imaging 1999; 9:786-793.[CrossRef][Medline]
  17. Pruessmann KP, Weiger M, Scheidegger MB, Boesiger P. SENSE: sensitivity encoding for fast MRI. Magn Reson Med 1999; 42:952-962.[CrossRef][Medline]
  18. 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]
  19. Spuentrup E, Buecker A, Stuber M, et al. Navigator-gated coronary magnetic resonance angiography using steady-state-free-precession: comparison to standard T2-prepared gradient-echo and spiral imaging. Invest Radiol 2003; 38:263-268.[CrossRef][Medline]
  20. Duerk JL, Lewin JS, Wendt M, Petersilge C. Remember true FISP? a high SNR, near 1-second imaging method for T2-like contrast in interventional MRI at .2 T. J Magn Reson Imaging 1998; 8:203-208.[Medline]
  21. 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]
  22. Spuentrup E, Bornert P, Botnar RM, Groen JP, Manning WJ, Stuber M. Navigator-gated free-breathing three-dimensional balanced fast field echo (TrueFISP) coronary magnetic resonance angiography. Invest Radiol 2002; 37:637-642.[CrossRef][Medline]
  23. Fischer SE, Wickline SA, Lorenz CH. Novel real-time R-wave detection algorithm based on the vectorcardiogram for accurate gated magnetic resonance acquisitions. Magn Reson Med 1999; 42:361-370.[CrossRef][Medline]
  24. 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]
  25. Brittain JH, Hu BS, Wright GA, Meyer CH, Macovski A, Nishimura DG. Coronary angiography with magnetization-prepared T2 contrast. Magn Reson Med 1995; 33:689-696.[Medline]
  26. Danias PG, McConnell MV, Khasgiwala VC, Chuang ML, Edelman RR, Manning WJ. Prospective navigator correction of image position for coronary MR angiography. Radiology 1997; 203:733-736.[Abstract/Free Full Text]
  27. Austen WG, Edwards JE, Frye RL, et al. A reporting system on patients evaluated for coronary artery disease: report of the Ad Hoc Committee for Grading of Coronary Artery Disease, Council on Cardiovascular Surgery, American Heart Association. Circulation 1975; 51(4 suppl):5-40.[Medline]
  28. Etienne A, Boesiger P, Manning W, Nagel E, Botnar R, Stuber M. Quantitative coronary analysis and visualization based on three dimensional coronary magnetic resonance angiography (abstr). J Cardiovasc Magn Reson 2002; 4:90.
  29. Etienne A, Botnar RM, Van Muiswinkel AM, Boesiger P, Manning WJ, Stuber M. "Soap-bubble" visualization and quantitative analysis of 3D coronary magnetic resonance angiograms. Magn Reson Med 2002; 48:658-666.[CrossRef][Medline]
  30. Giorgi B, Dymarkowski S, Maes F, Kouwenhoven M, Bogaert J. Improved visualization of coronary arteries using a new three-dimensional submillimeter MR coronary angiography sequence with balanced gradients. AJR Am J Roentgenol 2002; 179:901-910.[Abstract/Free Full Text]
  31. Achenbach S, Regenfus M, Ropers D, Kessler W, Daniel WG, Moshage W. Imaging of the coronary arteries using magnetic resonance angiography. Z Kardiol 2000; 89(suppl 1):21-26.[CrossRef]
  32. Kessler W, Laub G, Achenbach S, Ropers D, Moshage W, Daniel WG. Coronary arteries: MR angiography with fast contrast-enhanced three-dimensional breath-hold imaging—initial experience. Radiology 1999; 210:566-572.[Abstract/Free Full Text]
  33. Li D, Carr JC, Shea SM, et al. Coronary arteries: magnetization-prepared contrast-enhanced three-dimensional volume-targeted breath-hold MR angiography. Radiology 2001; 219:270-277.[Abstract/Free Full Text]
  34. Regenfus M, Ropers D, Achenbach S, et al. Comparison of contrast-enhanced breath-hold and free-breathing respiratory-gated imaging in three-dimensional magnetic resonance coronary angiography. Am J Cardiol 2002; 90:725-730.[CrossRef][Medline]



This article has been cited by other articles:


Home page
 RadiologyHome page
M. Miyazaki and V. S. Lee
Nonenhanced MR Angiography
Radiology, July 1, 2008; 248(1): 20 - 43.
[Abstract] [Full Text] [PDF]

Home page
 ANN INTERN MEDHome page
M. Dewey, F. Teige, D. Schnapauff, M. Laule, A. C. Borges, K.-D. Wernecke, T. Schink, G. Baumann, W. Rutsch, P. Rogalla, et al.
Noninvasive detection of coronary artery stenoses with multislice computed tomography or magnetic resonance imaging.
Ann Intern Med, September 19, 2006; 145(6): 407 - 415.
[Abstract] [Full Text] [PDF]

Home page
 RadiologyHome page
C. Jahnke, I. Paetsch, S. Achenbach, B. Schnackenburg, R. Gebker, E. Fleck, and E. Nagel
Coronary MR Imaging: Breath-hold Capability and Patterns, Coronary Artery Rest Periods, and {beta}-Blocker Use
Radiology, April 1, 2006; 239(1): 71 - 78.
[Abstract] [Full Text] [PDF]

Home page
 Eur Heart JHome page
C. Jahnke, I. Paetsch, K. Nehrke, B. Schnackenburg, R. Gebker, E. Fleck, and E. Nagel
Rapid and complete coronary arterial tree visualization with magnetic resonance imaging: feasibility and diagnostic performance
Eur. Heart J., November 1, 2005; 26(21): 2313 - 2319.
[Abstract] [Full Text] [PDF]

This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF)
Right arrow All Versions of this Article:
2323031225v1
232/3/669    most recent
Right arrow Submit a response
Right arrow Alert me when this article is cited
Right arrow Alert me when eLetters are posted
Right arrow Alert me if a correction is posted
Right arrow Citation Map
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Jahnke, C.
Right arrow Articles by Nagel, E.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Jahnke, C.
Right arrow Articles by Nagel, E.

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
RADIOLOGY RADIOGRAPHICS RSNA JOURNALS ONLINE