TABLE 1.
ACRIN 6698 DW-MRI Protocol Parameters and Protocol Adherence for N = 89 Test/Retest Cohort
| Parameter | DWI protocol specification | Test/retest cohort values (N) | Nacq out of protocola |
|---|---|---|---|
| Acquisition order | DWI precontrast injection | Compliant (88), mixed (1)b | 1 |
| Sequence type | SS-EPI | All compliant | |
| Frequency direction | R/Lc | R/L (60), A/P (10), mixed (1)d | |
| FOV (mm) | 260–360 | 280–390 | 4 |
| Matrix-frequency | 128–192 | 128–196 | 2 |
| Matrix-phase | 128–192 | 128–194 | 2 |
| Fat-suppression | Active fat-sat | All compliant | |
| TR (msec) | ≥4,000 | 4800–9400 | |
| TE (msec) | Minimum TE (50–100) | 59.2–114.0 | 5 |
| Flip Angle | 90 degrees | 90 | |
| B values | 0, 100, 600, 800 s/mm2 | All compliant | |
| Slice thickness (mm) | 4–5 | 4 (44), 5 (27) | |
| Number of slices | Complete bilateral coverage | 24–50 | |
| Slice gap (mm) | ≤ 1.0 | 0 | |
| No. averages | ≥2 | 2–5 | |
| Parallel imaging factor | ≥2 | N/C | |
| Total acquisition time | ≤ 5 minutes | N/C |
SS-EPI: Single-shot echo-planar imaging, N/C: data not collected.
a
Number of acquisitions (test or retest) with out-of-protocol values.
b
One study was done with the retest DWI acquisition following the contrast injection.
c
Protocol requirement of R/L frequency encoding was relaxed after investigation indicated better image quality with A/P frequency on some scanners.
d
One study was done with reversed phase/frequency encoding directions between test and retest scans.