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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).

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.

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.

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.)

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.)

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.)

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.

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.

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.

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.)

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.

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.

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.