Table 1.
MRI protocol. Synoptic table summarizes the imaging parameters of MR sequences. Axial T2-weighted SSFSE sequence is used as second localiser. Sagittal T2-weighted FRFSE sequence is oriented parallel to the longitudinal axis of the rectum identified on the previous axial T2-weighted SSFSE sequence. Oblique coronal and oblique axial T2-weighted FRFSE sequences are oriented respectively perpendicular or parallel to the longitudinal axis of the rectal tumor.
| MRI protocol | Axial T2 W SSFSE | Sagittal T2 W FRFSE | Oblique coronal T2 W FRFSE | Oblique axial T2 W FRFSE | Axial DWI SE EPI |
|---|---|---|---|---|---|
| Repetition time/Echo time (m s) | 765/59 | 3560/100 | 3440/100 | 3440/100 | 5425/74.8 |
| Flip angle | 90° | 90° | 90° | 90° | 90° |
| Echo train length | – | 21 | 23 | 23 | – |
| Section thickness (mm) | 6 | 3 | 3 | 3 | 5 |
| Interslice gap (mm) | 0.6 | 0,3 | 0.3 | 0.3 | 1 |
| Bandwidht (kHz) | 31.25 | 25 | 31.25 | 31.25 | 250 |
| Field of view (cm) | 38 | 30 | 28 | 28 | 40 |
| Matrix | 320 × 288 | 288 × 224 | 288 × 224 | 288 × 224 | 160 × 160 |
| No. of averages | 0.54 | 3 | 4 | 4 | 8 |
| No. of images | 30 | 30 | 30 | 30 | 24 |
| Frequency direction | Right to left | Anterior to posterior | Right to left | Anterior to posterior | Right to left |
| Acquisition time | 24 s | 4 min 10 s | 4 min 41 s | 4 min 49 s | 2 min 59 s |
| b-value (sec/mm2) | – | – | – | – | 0−800 |
T2W = T2-weighted, SSFSE = single-shot fast spin-echo, FRFSE = fast relaxation fast spin-echo, DWI = diffusion-weighted imaging, SE = spin-echo, EPI = echoplanar imaging.