Background-Contrast MRI enhancement patterns in several pathophysiologies resulting from ischemic myocardial injury are controversial or have not been investigated. We compared contrast enhancement in acute infarction (AI), after severe but reversible ischemic injury (RII), and in chronic infarction. Methods and Results-In dogs, a large coronary artery was occluded to study AI and/or chronic infarction (nϭ18), and a second coronary artery was chronically instrumented with a reversible hydraulic occluder and Doppler flowmeter to study RII (nϭ8). At 3 days after surgery, cine MRI revealed reduced wall thickening in AI (5Ϯ6% versus 33Ϯ6% in normal, PϽ0.001). In RII, wall thickening before, during, and after inflation of the occluder for 15 minutes was 35Ϯ5%, 1Ϯ8%, and 21Ϯ10% and Doppler flow was 19.8Ϯ5.3, 0.2Ϯ0.5, and 56.3Ϯ17.7 (peak hyperemia) cm/s, respectively, confirming occlusion, transient ischemia, and reperfusion. Gd-DTPA-enhanced MR images acquired 30 minutes after contrast revealed hyperenhancement of AI (294Ϯ96% of normal, PϽ0.001) but not of RII (98Ϯ6% of normal, PϭNS). Eight weeks later, the chronically infarcted region again hyperenhanced (253Ϯ54% of normal, nϭ8, PϽ0.001).High-resolution (0.5ϫ0.5ϫ0.5 mm) ex vivo MRI demonstrated that the spatial extent of hyperenhancement was the same as the spatial extent of myocyte necrosis with and without reperfusion at 1 day (Rϭ0.99, PϽ0.001) and 3 days (Rϭ0.99, PϽ0.001) and collagenous scar at 8 weeks (Rϭ0.97, PϽ0.001). Conclusions-In the pathophysiologies investigated, contrast MRI distinguishes between reversible and irreversible ischemic injury independent of wall motion and infarct age.

The segmented inversion-recovery turboFLASH sequence produced the greatest differences in regional myocardial signal intensity in animals. Application of this technique in patients with infarction substantially improved differentiation between injured and normal regions.

The normal LV differs in volume and mass between sexes and among certain ethnic groups. When indexed by body surface area, LV mass was independent of age for both sexes. Studies that assess cardiovascular risk factors in relationship to cardiac function and structure need to account for these normal variations in the population.

In five healthy subjects and 18 patients, cine magnetic resonance (MR) imaging of the heart was performed with a true fast imaging with steady-state precession (FISP) sequence. Results were compared both quantitatively and qualitatively with those at cine fast low-angle shot (FLASH) MR imaging. The blood-myocardial contrast-to-noise ratio (CNR) was 2.0 times higher and the normalized (for measurement time and pixel size) blood-myocardial CNR was 4.0 times higher for true FISP compared with FLASH MR imaging. Qualitative scores for image quality were significantly higher with true FISP MR imaging. Segmented cine true FISP MR imaging generated high-contrast MR images of the heart in healthy subjects and in patients with heart disease and produced image quality superior to that with cine FLASH MR imaging.

The purpose of this work was to develop an ECG-triggered, segmented 3D true-FISP (fast imaging with steady-state precession) technique to improve the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of breath-hold coronary artery imaging. The major task was to optimize an appropriate magnetization preparation scheme to permit saturation of the epicardial fat signal. An ␣/2 preparation pulse was used to speed up the approach to steady-state following a frequencyselective fat-saturation pulse in each heartbeat. The application of dummy cycles was found to reduce the oscillation of the magnetization during data acquisition. The fat saturation and magnetization preparation scheme was validated with simulations and phantom studies. Volunteer studies demonstrated substantially increased SNR (55%) and CNR (178%) for coronary arteries compared to FLASH (fast low-angle shot) with the same imaging time. Volume-targeted breath-hold imaging (VCATS) has recently been described for MR angiography of the coronary arteries (1). VCATS employs a 3D steady-state incoherent gradient-echo sequence, FLASH (fast low-angle shot), for data acquisition. In such a sequence, the transverse magnetization is spoiled at the end of each repetition time (TR) to create T 1 -weighted contrast. As TR is shortened and bandwidth increased to speed up data acquisition, the available signal-to-noise ratio (SNR) becomes a limiting factor with FLASH. Injection of contrast media is necessary to shorten the blood T 1 to improve SNR and contrastto-noise ratio (CNR) (2-6).True-FISP (fast imaging with steady-state precession) has recently found important applications in cardiac cine imaging (7,8) for the evaluation of left ventricular function. Significant improvements in blood SNR and blood-myocardium CNR were obtained as compared to FLASH. In true-FISP, the transverse magnetization is maintained between successive RF pulses because the net gradient moments are zero in all three directions and no RF spoiling is implemented. Coherent transverse magnetization continues to contribute to the signal in successive TRs, resulting in a higher SNR than in magnetization-spoiled techniques such as FLASH. For the same reason, large flip angles close to 90°can be used in true-FISP because there are no saturation effects and the magnetization is restored and reused. Analysis using the Bloch equations predicts that the signal intensity in true-FISP is T 2 /T 1 -weighted. The contrast between blood and myocardium is therefore enhanced because blood has a much higher T 2 /T 1 than myocardium.The concept of true-FISP (9) and its applications in brain and spine imaging (10) were proposed years ago. However, because of the zero net applied gradients, there was no averaging of the resonant offsets and, with relatively long minimum TRs achievable at the time, the technique was extremely sensitive to field inhomogeneities and was not used in cardiac imaging. With recent improvements in gradient capabilities, short TRs on the order of 3-4 msec have been achieved. Comb...