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Thorax: Low-Dose Contrast-enhanced Three-dimensional MR Angiography with Subsecond Temporal Resolution—Initial Results¹

¹ From the Department of Radiology, Northwestern University Medical School, 448 E Ontario St, Suite 700, Chicago, IL 60611 (J.P.F., V.B., J.C.C., R.M.M., F.S.P.); and Siemens Medical Systems, Chicago, Ill (R.K., G.L.). From the 2000 RSNA scientific assembly. Received May 31, 2001; revision requested July 12; final revision received February 18, 2002; accepted March 14. Address correspondence to J.P.F. (e-mail: pfinn@northwestern.edu).

View larger version (30K): [in a new window]   Figure 1. Timing diagram for the subsecond 3D MR angiographic sequence. With 1.60/0.65 (repetition time [TR] msec/echo time [TE] msec) and radio-frequency spoiling, transverse coherences are destroyed, and T1 weighting is isolated on the resulting images. Asymmetric sampling is used in frequency to shorten the echo time and with both in-plane (Np) and through-plane (Ns) encoding steps to shorten the acquisition. G = gradient, = pulse, ADC = analog digital converter.

View larger version (153K): [in a new window]   Figure 2a. (a) Subsecond MR angiograms (1.60/0.65), left anterior oblique projection, in a healthy 32-year-old woman. Six frames are shown from a 24-frame series. Contrast material is shown sequentially in the pulmonary artery (PA), pulmonary parenchyma, pulmonary veins (arrows), left atrium (LA), and aorta (A). The frame time for this study was 750 msec, after injection of 6 mL of gadolinium-based contrast agent at a rate of 6 mL/sec. (b) Time-intensity curves show clear separation of the curves for the right and left sides of the heart. = pulmonary artery, = pulmonary vein, = ascending aorta. Time 0 corresponds to the start of the contrast material injection into the antecubital vein. (c) Subsecond MR angiograms (1.60/0.65), coronal projection, after a second injection of 6 mL of gadolinium-based contrast agent at a rate of 6 mL/sec. Six frames are shown from a 24-frame series. Contrast material is shown sequentially in the pulmonary artery (PA), pulmonary parenchyma, pulmonary veins (arrows), left atrium (LA), and aorta (A).

View larger version (25K): [in a new window]   Figure 2b. (a) Subsecond MR angiograms (1.60/0.65), left anterior oblique projection, in a healthy 32-year-old woman. Six frames are shown from a 24-frame series. Contrast material is shown sequentially in the pulmonary artery (PA), pulmonary parenchyma, pulmonary veins (arrows), left atrium (LA), and aorta (A). The frame time for this study was 750 msec, after injection of 6 mL of gadolinium-based contrast agent at a rate of 6 mL/sec. (b) Time-intensity curves show clear separation of the curves for the right and left sides of the heart. = pulmonary artery, = pulmonary vein, = ascending aorta. Time 0 corresponds to the start of the contrast material injection into the antecubital vein. (c) Subsecond MR angiograms (1.60/0.65), coronal projection, after a second injection of 6 mL of gadolinium-based contrast agent at a rate of 6 mL/sec. Six frames are shown from a 24-frame series. Contrast material is shown sequentially in the pulmonary artery (PA), pulmonary parenchyma, pulmonary veins (arrows), left atrium (LA), and aorta (A).

View larger version (117K): [in a new window]   Figure 2c. (a) Subsecond MR angiograms (1.60/0.65), left anterior oblique projection, in a healthy 32-year-old woman. Six frames are shown from a 24-frame series. Contrast material is shown sequentially in the pulmonary artery (PA), pulmonary parenchyma, pulmonary veins (arrows), left atrium (LA), and aorta (A). The frame time for this study was 750 msec, after injection of 6 mL of gadolinium-based contrast agent at a rate of 6 mL/sec. (b) Time-intensity curves show clear separation of the curves for the right and left sides of the heart. = pulmonary artery, = pulmonary vein, = ascending aorta. Time 0 corresponds to the start of the contrast material injection into the antecubital vein. (c) Subsecond MR angiograms (1.60/0.65), coronal projection, after a second injection of 6 mL of gadolinium-based contrast agent at a rate of 6 mL/sec. Six frames are shown from a 24-frame series. Contrast material is shown sequentially in the pulmonary artery (PA), pulmonary parenchyma, pulmonary veins (arrows), left atrium (LA), and aorta (A).

View larger version (155K): [in a new window]   Figure 3a. (a) Subsecond MR angiograms (1.60/0.65), left anterior oblique projection, in a 37-year-old female patient with a patent ductus arteriosus and Eisenmenger syndrome. Six frames are shown from a 24-frame series. Contrast material is hyperintense simultaneously in the main pulmonary artery (PA) and distal arch (DA); these findings confirm a right-to-left shunt, with later filling of the pulmonary veins (arrows), left atrium (LA), and ascending aorta (AA). The frame time for this study was 900 msec. (b) Time-intensity curves show complete overlap of the curves for the pulmonary artery () and proximal descending aorta (x), with later filling of the ascending aorta (). = pulmonary vein. Time zero corresponds to the start of the contrast material injection into the antecubital vein. (c) Subsecond MR angiograms (1.60/0.65), coronal projection, show the same sequence of enhancement. Six frames are shown from a 24-frame series. A separate injection of 10 mL of contrast material was given at a rate of 6 mL/sec. Note the prominent proximal pulmonary arteries (PA) and narrowed distal branches; these findings are consistent with pulmonary hypertension. AA = ascending aorta, LA = left atrium, arrows = pulmonary veins.

View larger version (24K): [in a new window]   Figure 3b. (a) Subsecond MR angiograms (1.60/0.65), left anterior oblique projection, in a 37-year-old female patient with a patent ductus arteriosus and Eisenmenger syndrome. Six frames are shown from a 24-frame series. Contrast material is hyperintense simultaneously in the main pulmonary artery (PA) and distal arch (DA); these findings confirm a right-to-left shunt, with later filling of the pulmonary veins (arrows), left atrium (LA), and ascending aorta (AA). The frame time for this study was 900 msec. (b) Time-intensity curves show complete overlap of the curves for the pulmonary artery () and proximal descending aorta (x), with later filling of the ascending aorta (). = pulmonary vein. Time zero corresponds to the start of the contrast material injection into the antecubital vein. (c) Subsecond MR angiograms (1.60/0.65), coronal projection, show the same sequence of enhancement. Six frames are shown from a 24-frame series. A separate injection of 10 mL of contrast material was given at a rate of 6 mL/sec. Note the prominent proximal pulmonary arteries (PA) and narrowed distal branches; these findings are consistent with pulmonary hypertension. AA = ascending aorta, LA = left atrium, arrows = pulmonary veins.

View larger version (106K): [in a new window]   Figure 3c. (a) Subsecond MR angiograms (1.60/0.65), left anterior oblique projection, in a 37-year-old female patient with a patent ductus arteriosus and Eisenmenger syndrome. Six frames are shown from a 24-frame series. Contrast material is hyperintense simultaneously in the main pulmonary artery (PA) and distal arch (DA); these findings confirm a right-to-left shunt, with later filling of the pulmonary veins (arrows), left atrium (LA), and ascending aorta (AA). The frame time for this study was 900 msec. (b) Time-intensity curves show complete overlap of the curves for the pulmonary artery () and proximal descending aorta (x), with later filling of the ascending aorta (). = pulmonary vein. Time zero corresponds to the start of the contrast material injection into the antecubital vein. (c) Subsecond MR angiograms (1.60/0.65), coronal projection, show the same sequence of enhancement. Six frames are shown from a 24-frame series. A separate injection of 10 mL of contrast material was given at a rate of 6 mL/sec. Note the prominent proximal pulmonary arteries (PA) and narrowed distal branches; these findings are consistent with pulmonary hypertension. AA = ascending aorta, LA = left atrium, arrows = pulmonary veins.

View larger version (109K): [in a new window]   Figure 4a. (a) Digital subtraction angiogram, right anterior oblique projection, in a 79-year-old female patient with an atrial septal defect. The catheter has been introduced cephalad from the inferior vena cava, it crosses the atrial septal defect, and its tip (arrow) lies in the left atrium. After the injection, the contrast material is hyperintense in the left side of the heart and aorta. (b) Subsecond MR angiograms (1.60/0.65), left anterior oblique projection. Six frames are shown from a 24-frame series. The contrast material is hyperintense simultaneously in both the right (RA) and left (LA) atria; this finding confirms the presence of a right-to-left shunt. Shortly thereafter, the main pulmonary artery (PA) and ascending aorta (AA) are enhanced simultaneously. Filling of the pulmonary veins occurs later (arrows), with a subsequent second peak in the ascending aorta. The frame time for this study was 900 msec after injection of 6 mL of gadolinium-based contrast agent at a rate of 6 mL/sec. (c) Time-intensity curves show complete overlap of the pulmonary arterial () peak and the first peak of the ascending aorta (); this finding confirms the presence of a right-to-left shunt. Subsequently, delayed filling of the pulmonary veins is followed by the second aortic peak. = pulmonary vein. Time 0 corresponds to the start of the contrast material injection into the antecubital vein.

View larger version (156K): [in a new window]   Figure 4b. (a) Digital subtraction angiogram, right anterior oblique projection, in a 79-year-old female patient with an atrial septal defect. The catheter has been introduced cephalad from the inferior vena cava, it crosses the atrial septal defect, and its tip (arrow) lies in the left atrium. After the injection, the contrast material is hyperintense in the left side of the heart and aorta. (b) Subsecond MR angiograms (1.60/0.65), left anterior oblique projection. Six frames are shown from a 24-frame series. The contrast material is hyperintense simultaneously in both the right (RA) and left (LA) atria; this finding confirms the presence of a right-to-left shunt. Shortly thereafter, the main pulmonary artery (PA) and ascending aorta (AA) are enhanced simultaneously. Filling of the pulmonary veins occurs later (arrows), with a subsequent second peak in the ascending aorta. The frame time for this study was 900 msec after injection of 6 mL of gadolinium-based contrast agent at a rate of 6 mL/sec. (c) Time-intensity curves show complete overlap of the pulmonary arterial () peak and the first peak of the ascending aorta (); this finding confirms the presence of a right-to-left shunt. Subsequently, delayed filling of the pulmonary veins is followed by the second aortic peak. = pulmonary vein. Time 0 corresponds to the start of the contrast material injection into the antecubital vein.

View larger version (24K): [in a new window]   Figure 4c. (a) Digital subtraction angiogram, right anterior oblique projection, in a 79-year-old female patient with an atrial septal defect. The catheter has been introduced cephalad from the inferior vena cava, it crosses the atrial septal defect, and its tip (arrow) lies in the left atrium. After the injection, the contrast material is hyperintense in the left side of the heart and aorta. (b) Subsecond MR angiograms (1.60/0.65), left anterior oblique projection. Six frames are shown from a 24-frame series. The contrast material is hyperintense simultaneously in both the right (RA) and left (LA) atria; this finding confirms the presence of a right-to-left shunt. Shortly thereafter, the main pulmonary artery (PA) and ascending aorta (AA) are enhanced simultaneously. Filling of the pulmonary veins occurs later (arrows), with a subsequent second peak in the ascending aorta. The frame time for this study was 900 msec after injection of 6 mL of gadolinium-based contrast agent at a rate of 6 mL/sec. (c) Time-intensity curves show complete overlap of the pulmonary arterial () peak and the first peak of the ascending aorta (); this finding confirms the presence of a right-to-left shunt. Subsequently, delayed filling of the pulmonary veins is followed by the second aortic peak. = pulmonary vein. Time 0 corresponds to the start of the contrast material injection into the antecubital vein.

View larger version (110K): [in a new window]   Figure 5a. (a) True fast imaging with steady-state precession cine MR image (3.2/1.6, section thickness of 5 mm, acquisition time of 20 seconds, contrast material dose of 30 mL of gadopentetate dimeglumine at a rate of 2 mL/sec), left anterior oblique projection, in a 55-year-old male patient, depicts an ascending aortic aneurysm. A large smooth aneurysm extends from the aortic outlet (Ao) and tapers toward the arch (Ar), without evidence of dissection or thrombus. (b) Conventional partition MR angiograms (2.52/0.88), left anterior oblique projection, confirm the extent and form of the aneurysm. Note the pulsation artifact in the ascending aorta on several of the images and the persistent enhancement of the pulmonary arteries (arrows) and veins (arrowheads) that can obscure detail on MIPs (not shown). (c) Subsecond MR angiograms (1.60/0.65), left anterior oblique projection, are six frames from a 24-frame series. Contrast material is shown sequentially in the right side of the heart, main pulmonary artery (PA), pulmonary parenchyma, pulmonary veins (arrows), left atrium (LA), and aorta (A). The appearance, size, and extent of the ascending aortic aneurysm are similar to those shown in a and b. There is, however, extended volume coverage relative to b and clear separation of phases in the right and left sides of the heart relative to a. The frame time for this study was 900 msec.

View larger version (188K): [in a new window]   Figure 5b. (a) True fast imaging with steady-state precession cine MR image (3.2/1.6, section thickness of 5 mm, acquisition time of 20 seconds, contrast material dose of 30 mL of gadopentetate dimeglumine at a rate of 2 mL/sec), left anterior oblique projection, in a 55-year-old male patient, depicts an ascending aortic aneurysm. A large smooth aneurysm extends from the aortic outlet (Ao) and tapers toward the arch (Ar), without evidence of dissection or thrombus. (b) Conventional partition MR angiograms (2.52/0.88), left anterior oblique projection, confirm the extent and form of the aneurysm. Note the pulsation artifact in the ascending aorta on several of the images and the persistent enhancement of the pulmonary arteries (arrows) and veins (arrowheads) that can obscure detail on MIPs (not shown). (c) Subsecond MR angiograms (1.60/0.65), left anterior oblique projection, are six frames from a 24-frame series. Contrast material is shown sequentially in the right side of the heart, main pulmonary artery (PA), pulmonary parenchyma, pulmonary veins (arrows), left atrium (LA), and aorta (A). The appearance, size, and extent of the ascending aortic aneurysm are similar to those shown in a and b. There is, however, extended volume coverage relative to b and clear separation of phases in the right and left sides of the heart relative to a. The frame time for this study was 900 msec.

View larger version (107K): [in a new window]   Figure 5c. (a) True fast imaging with steady-state precession cine MR image (3.2/1.6, section thickness of 5 mm, acquisition time of 20 seconds, contrast material dose of 30 mL of gadopentetate dimeglumine at a rate of 2 mL/sec), left anterior oblique projection, in a 55-year-old male patient, depicts an ascending aortic aneurysm. A large smooth aneurysm extends from the aortic outlet (Ao) and tapers toward the arch (Ar), without evidence of dissection or thrombus. (b) Conventional partition MR angiograms (2.52/0.88), left anterior oblique projection, confirm the extent and form of the aneurysm. Note the pulsation artifact in the ascending aorta on several of the images and the persistent enhancement of the pulmonary arteries (arrows) and veins (arrowheads) that can obscure detail on MIPs (not shown). (c) Subsecond MR angiograms (1.60/0.65), left anterior oblique projection, are six frames from a 24-frame series. Contrast material is shown sequentially in the right side of the heart, main pulmonary artery (PA), pulmonary parenchyma, pulmonary veins (arrows), left atrium (LA), and aorta (A). The appearance, size, and extent of the ascending aortic aneurysm are similar to those shown in a and b. There is, however, extended volume coverage relative to b and clear separation of phases in the right and left sides of the heart relative to a. The frame time for this study was 900 msec.

View larger version (34K): [in a new window]   Figure 6. Bar graph depicts visualization ratings for anatomic structures on conventional partition MR images (black bars), conventional MIPs (gray bars), and subsecond MR angiograms (white bars). Higher scores imply easier visualization. RA = right atrium or ventricle, PA = pulmonary artery, PV = pulmonary vein, LA = left atrium or ventricle, AA = ascending aorta, DA = descending aorta. Conventional partition and subsecond MR images were not significantly different from each other, whereas both were significantly better than conventional MIPs (P < .05). This difference is explained by overlap of complex 3D anatomic structures on conventional 3D MIPs.