FASt single‐breathhold 2D multislice myocardial T1 mapping (FAST1) at 1.5T for full left ventricular coverage in three breathholds

Figure 1. FAST1 sequence diagram and acquisition scheme. Five T1 maps are acquired in one breathhold, each based on a two‐heartbeat imaging block including a slice‐selective inversion pulse and the acquisition of two ECG‐triggered single‐shot images. Minimal inversion time is used for each imaging block to reduce the impact of cardiac motion between the slice‐selective inversion pulse and the first image acquisition. An inversion slice thickness larger than the imaging slice thickness is used to minimize the impact of cardiac motion. Recovery heartbeats are introduced between the third and fourth imaging blocks to minimize potential slice crosstalk between the slice‐selective inversion pulses. In the physiological HR range (50–110 bpm), the corresponding nominal breathhold duration is 9–13 sec.

Figure 2. Accuracy and precision of FAST1‐BS, FAST1‐IR, and MOLLI in numerical simulation. FAST1‐BS provided higher accuracy and reduced precision than FAST1‐IR and MOLLI. FAST1‐IR led to reduced accuracy and precision when compared with MOLLI. All techniques were T2‐dependent.

Figure 3. Slice crosstalk using different TRD and RTHK using FAST1‐BS and FAST1‐IR in phantom. (a) Maximum interslice T1 variations among all vials using different TRD from 4 sec to 10 sec and a fixed RTHK of 4. With TRD exceeding 6 sec, maximum interslice T1 variations were restricted to <13 msec. (b) Maximum interslice T1 variations among all vials using different RTHK from 2 to 8 and a fixed TRD of 6 sec. With RTHK not exceeding 4, maximum interslice T1 variations were restricted to <11 msec.

Figure 4. T1 accuracy (a), spatial variability (b), and repeatability (c) of FAST1‐BS, FAST1‐IR, and MOLLI in phantom. T1 error was –26 ± 5 msec vs. –73 ± 53 msec vs. –56 ± 36 msec, T1 spatial variability was 9 ± 6 msec vs. 8 ± 4 msec vs. 6 ± 4 msec and T1 repeatability was 2 ± 1 msec vs. 1 ± 1 msec vs. 1 ± 0 msec, respectively.

Figure 5. Example native myocardial T1 maps measured in one healthy volunteer using FAST1‐BS, FAST1‐IR, and MOLLI. Each row for FAST1‐BS and FAST1‐IR represents one FAST1 acquisition in a separated breathhold. Both FAST1 techniques enabled the acquisition of 15 contiguous slices covering the entire left ventricle in the same time as the acquisition of three slices using MOLLI (ie, 3 breathholds). Note the blue rectangles indicate the three common slice locations in FAST1 and MOLLI.

Figure 6. Native myocardial T1 times (a), spatial variability (b), and repeatability (c) using FAST1‐BS, FAST1‐IR, and MOLLI in healthy volunteers. Average (bar plots) and SD (error bars) over all healthy volunteers are presented. FAST1‐BS, FAST1‐IR, and MOLLI provided different native myocardial T1 times (P < 0.0001). FAST1‐BS and FAST1‐IR led to higher spatial variability than MOLLI (P < 0.001). There were no statistically significant differences between all techniques for T1 repeatability (P = 0.18).

Figure 7. Segment‐wise native myocardial T1 measures, spatial variability, and repeatability using FAST1‐BS, FAST1‐IR, and MOLLI in healthy volunteers. There were no statistically significant differences between all techniques in terms of segmental variations of native T1 measures (P = 0.20), spatial variability (P = 0.32), and repeatability (P = 0.58).

Figure 8. Example native myocardial T1 maps obtained using FAST1‐BS, FAST1‐IR, and MOLLI in a 31‐year‐old male patient admitted for suspected myocarditis. Each row for FAST1‐BS and FAST1‐IR represents one FAST1 acquisition in a separated breathhold. Both FAST1 techniques enabled the acquisition of 15 contiguous slices covering the entire left ventricle in the same time as the acquisition of three slices using MOLLI (ie, three breathholds). Note that the blue rectangles indicate the three common slice locations in FAST1 and MOLLI.

Figure 9. Example postcontrast myocardial T1 maps obtained using FAST1‐BS, FAST1‐IR, and MOLLI in a 31‐year‐old male patient admitted for suspected myocarditis. Each row for FAST1‐BS and FAST1‐IR represents one FAST1 acquisition in a separated breathhold. Both FAST1 techniques enabled the acquisition of 15 contiguous slices covering the entire left ventricle in the same time as the acquisition of three slices using MOLLI (ie, three breathholds). Note the blue rectangles indicate the three common slice locations in FAST1 and MOLLI.

Figure 10. Pearson correlation and Bland–Altman analyses between FAST‐BS and MOLLI (a,c) as well as between FAST1‐IR and MOLLI (b,d) for both native and postcontrast myocardial T1 times measured in both healthy volunteers and patients. In Pearson correlation analysis plots, confidence interval (solid lines) and identity line (y = x, dashed line) are also plotted besides the linear regression line (solid line). FAST1‐BS and FAST1‐IR yielded highly linearly correlated T1 times with MOLLI (Pearson correlation coefficient = 0.93 for native and 0.98 for postcontrast myocardial T1 times).