The application of an inversion-recovery snapshot FLASH series of images with different T 1 weightings, and requires ( f ast low-angled shot) imaging sequence to the dynamic measureapproximately 10 minutes of imaging time. Variants of this ment of monoexponential T 1 relaxation was investigated. The ef- (10) have been used to measure multiexponential relaxfect of (a) a reduction in the overall sequence repetition time, and ation (9, 10, 12) required for accurate evaluation of T 1 in (b) an increase of the read-pulse flip angle, on the measurement some tissues. of T 1 was analyzed. The error in T 1 introduced by these factors is Multiple images have been obtained with an inversioncalculated, and a fuller analysis that takes them into account is recovery snapshot-FLASH ( fast low-angled shot) or Turpresented. Data from a phantom are used to confirm this analysis.
boFLASH imaging sequence (13), and used to measure T 1 .
The magnitude of the errors is illustrated by measuring myocardial
Here an inversion pulse is applied, and as the longitudinal T 1 in patients with acute ischaemic heart disease during the injecmagnetization recovers, a series of images is acquired. Each tion of a bolus of the contrast medium gadobenate dimeglumine.
Overall, there was a 10% difference between the T 1 values when the image is formed by applying a train of low-flip-angle pulses, approximate and exact solutions were used; this was statistically each of which gives one phase-encode line. There is a change significant. However, the difference was on average 25% for pain longitudinal magnetization due to the application of the tients with a high heart rate (because of the shorter sequencereadout pulses, and a method of correction for this has been repetition time) in areas of infarcted myocardium (because of the shown ( ).
longer T 1 ). α§ 1997 Academic Press
If T 1 is changing rapidly, then methods that need multiple images may not be practical. Measurement of T 1 can be achieved in the shortest time by repeatedly acquiring just a THEORY