Recommended Acquisition Protocols for Perfusion-Weighted (PWI) and Diffusion-Weighted (DWI) MR Imaging
| PWI | DWI | |
|---|---|---|
| Sequence | Single-shot gradient-echo echoplanar imaging | Single-shot diffusion-weighted spin-echo echoplanar imaging |
| Image acquisition parameters | TR≤1500 ms* | TR≥4000 ms but can be as high as needed to fit all slices |
| TE=35 to 45 ms @ 1.5T | TE minimum (partial Fourier) | |
| TE=25 to 30 ms @ 3T | b=0 and 1000 sec/mm2 | |
| flip angle α=60 to 90° @ 1.5T, 60° @ 3.0T | (at least 3 orthogonal directions) eddy current correction (dual-spin echo or postprocessing) | |
| Parallel imaging and coil selected at the discretion of the site | ||
| Image acquisition duration | 90 to 120 seconds image acquisition started 10 seconds before initiation of injection to achieve at least 10 to 12 baseline images and also record slow uptake in stroke regions | 90 to 260 seconds |
| Coverage and slice thickness | Whole brain coverage using ≥12 slices slice thickness 5 mm gap 0 to 1 mm* matrix size 128×128* phase-encoding along A/P direction field of view ≈24 cm | Whole brain coverage using ≥12 slices slice thickness 5 mm gap 0 to 1 mm matrix size 128×128 phase-encoding along A/P direction field of view ≈24 cm |
| Slice orientation | Parallel to hard palate | Parallel to hard palate (ideally perpendicular to the scanner bore) |
| Contrast material | Standard gadolinium-based contrast material | … |
| Contrast volume | Single dose (for half-molar agent, ≈20 mL for 100 kg person) followed by 20 to 40 mL saline flush | … |
| Injection rate | 4 to 6 mL per second (power injector required) same injection rate for contrast and saline | … |
| IV access | 18 to 20 gauge IV line right antecubital vein preferred | … |
| Miscellaneous | PWI can be performed before or after MR-angiography | … |
MRI scanner: 1.5T or 3T (MRI scanners with 512 image limit per series should be excluded).
* Interslice gap can be increased and matrix size can be decreased to achieve whole-brain coverage (TR can also be optimized to afford entire brain coverage but should be ≤1500 to 2000 ms).