Table 3.
“Minimum” Recommended PCNSL 1.5T MRI Protocol*
| DWI | T1W-Preb | T2W | DSC Perfusiona,^ | CE-T2W-FLAIR | T1W-Posto,s | T1W-Postb,e | |
|---|---|---|---|---|---|---|---|
| Contrast Injectiona | |||||||
| Sequence | SS-EPId | IR-GREf,i,j,k | TSEc | GE-EPI | TSEc | TSE/SE | IR-GREf,i,j,k |
| Plane | Axial | Any | Any | Axial | Any | Axial | Any |
| Mode | 2D | 3D | 3Dn | 2D | 3Dn,i | 2Dp | 3D |
| TR (ms) | >5000 | 2100l | >2500 | 1000-1500 | >6000 | 400-600 | 2100l |
| TE (ms) | Min | Min | 80-120 | 45 ms | 90-140 | Min | Min |
| TI (ms) | 1100m | 2000-2500 | 1100m | ||||
| Flip angle | 90°/180° | 10°-15° | 90°/≥160° | 30-35° | 90°/≥160° | 90°/≥160° | 10°-15° |
| Frequency | 128 | 172 | ≥256 | ≥96 | ≥256 | ≥256 | ≥172 |
| Phase | 128 | 172 | ≥256 | ≥96 | ≥256 | ≥256 | ≥172 |
| NEX | ≥1 | ≥1 | ≥1 | 1 | ≥1 | ≥1 | ≥1 |
| FOV | 240 mm | 256 mm | 240 mm | 240 mm | 240 mm | 240 mm | 256 mm |
| Slice thickness | ≤4 mm | ≤1.5 mm | ≤1.5 mm | 3-5 mm as needed to cover tumorq | ≤1.5 mm | ≤4 mm | ≤1.5 mm |
| Spacing | 0 | 0 | 0 | 0-1 mm as needed to cover tumor | 0 | 0 | 0 |
| Other options | b = 0, 500 and 1000 s/mm2 ≥3 directions | Consider fat saturation | 30-60 pre-bolus time points; >120 total time points; centered on tumor. Either DCE or DSC is recommended at 1.5T | Consider fat saturation | Consider fat saturation | Consider fat saturation | |
| Parallel imagingh | Up to 2× | Up to 2× | Up to 2× | Up to 2× | Up to 2× | Up to 2× | Up to 2× |
| Estimated time (min)r | 2-5 | 5-10 | 5-10 | 2-4 | 5-10 | 3-6 | 5-10 |
Abbreviations: CE-T2W-FLAIR, contrast-enhanced T2-weighted fluid-attenuated inversion recovery; DCE, dynamic contrast-enhanced; DSC, dynamic susceptibility contrast; DWI, diffusion-weighted imaging; GE-EPI, gradient echo echo-planar imaging; IR-GRE, inversion recovery gradient echo; PCNSL, primary central nervous system lymphoma; SE, spin echo; SS-EPI, single-shot echo-planar imaging; TSE, turbo spin echo.
a0.1 mmol/kg dose injection with a gadolinium-chelated contrast agent as a single total dose is recommended. For DSC perfusion, contrast injection is performed after obtaining 30-50 DSC time points. In the absence of performing DCE, no DSC preload contrast dose is recommended given use of low flip angle. DSC perfusion can be performed with the “ideal” protocol at 3T as well as with the “minimum standard” protocols at 3T and 1.5T. The use of a power injector is desirable at an injection rate of 3-5 cc/sec.
^At 1.5T only DCE or DSC is recommended. If only DCE acquisition is desired, the DCE sequence will replace the DSC and employ the full single dose (0.1 mmol/kg) contrast injection. Given the limitations of contrast-to-noise ratio at 1.5T field strength, ½ + ½ dosing is not recommended. As such, the use of a total single dose (0.1 mmol/kg) cannot accommodate the acquisition of both DCE and DSC, unless larger contrast dosage is employed.
bPost-contrast 3D T1-weighted images should be collected with equivalent parameters to pre-contrast 3D T1-weighted images.
cTSE = turbo spin echo (Siemens and Philips) is equivalent to FSE (fast spin echo; GE, Hitachi, Toshiba).
dIn the event of significant patient motion, a radial acquisition scheme may be used (eg, BLADE [Siemens], PROPELLER [GE], MultiVane [Philips], RADAR [Hitachi], or JET [Toshiba]); however, this acquisition scheme can cause significant differences in ADC quantification and should be used only if EPI is not an option. Furthermore, this type of acquisition takes considerable more time.
e3D post-contrast T1-weighted images are collected between 4 and 8 min after contrast injection and this timing is constant across all MR exams performed in each patient.
fAcceptable 3D T1W TSE sequences include CUBE (GE), SPACE (Siemens), VISTA (Philips), isoFSE (Hitachi), or 3D MVOX (Canon).
hInvestigators are encouraged to work with their scanner vendors to determine the best parallel imaging strategies, which may include simultaneous multislice imaging (SMS), controlled aliasing in parallel imaging resulting in higher acceleration (CAIPI), iPAT, GRAPPA, as well as turbo or other acceleration factors. High performance MRI scanners may be capable of higher acceleration factors.
i2D FLAIR is an optional alternative to 3D FLAIR, with sequence parameters as follows per previously published recommendations (Kaufmann et al): 2D TSE/FSE acquisition; TE = 100-140 ms; TR = >6000 ms; TI = 2000-2500 ms (chosen based on vendor recommendations for optimized protocol and field strength); GRAPPA ≤ 2; fat suppression; slice thickness ≤ 3 mm; orientation axial; FOV ≤ 250 mm × 250 mm; matrix ≥ 244 × 244. FL2D = two-dimensional fast low angle shot (FLASH; Siemens) is equivalent to the spoiled gradient-recalled echo (SPGR; GE) or T1-fast field echo (FFE; Philips), fast field echo (FastFE; Toshiba), or the radiofrequency spoiled steady-state acquisition rewound gradient echo (RSSG; Hitachi). A fast gradient echo sequence without inversion preparation is desired.
jIR-GRE = inversion-recovery gradient-recalled echo sequence is equivalent to MPRAGE = magnetization prepared rapid gradient-echo (Siemens and Hitachi) and the inversion-recovery spoiled gradient-echo (IR-SPGR or Fast SPGR with inversion activated or BRAVO; GE), 3D turbo field echo (TFE; Philips), or 3D fast field echo (3D Fast FE; Toshiba).
kA 3D acquisition without inversion preparation will result in different contrast compared with MPRAGE or another IR-prepped 3D T1-weighted sequences and therefore should be avoided.
lFor Siemens and Hitachi scanners. GE, Philips, and Toshiba scanners should use a TR = 5-15 ms for similar contrast.
mFor Siemens and Hitachi scanners. GE, Philips, and Toshiba scanners should use a TI = 400-450 ms for similar contrast.
n2D TSE should be performed if 3D volumetric sequence is not available. Minimal slice thickness should be utilized for 2D sequence.
oIf IR-GRE T1W imaging is utilized in place of 3D TSE then 2D post-contrast TSE/SE sequence is recommended prior to IR-GRE T1W.
pWhenever possible 3D TSE is recommended as the preferred T1W sequence. If 3D TSE is able to be performed at 1.5T, then IR-GRE sequences should be eliminated.
qIf the lesion extends beyond the original DSC coverage of tumor, an increase in slice thickness (up to 5 mm) or increase in gap could be considered to ensure adequate coverage.
rImaging times provided as an estimation only. Exact imaging times will depend upon individual scanner and hardware performance capabilities.
sPatient comfort and potential for movement may require 3D T1W IR-GRE sequence prior to the 2D T1W TSE/SE. However, diminished lesion conspicuity observed with 3D T1W IR-GRE sequence can be improved by delaying acquisition until the end of the examination.
*Adapted from Refs.4–6