TABLE 3.
A Image quality quality assurance (QA) testing tolerances from American College of Radiology (ACR) and TG‐284 using the ACR Large MRI Phantom
| Tolerances | ||
|---|---|---|
| QA tests | TG‐284 | ACR |
| Image quality | ||
| Geometric accuracy | ±2 mm across 25‐cm field of view (FOV) with phantom >30 cm in diameter | ±2 mm using Large ACR Phantom |
| High contrast spatial resolution | ≤1.0 mm | ≤1.0 mm |
| Low contrast detectability |
21 (0.3 T) to 36 (1.5 T) total spokes, 40 spokes (3 T) |
≥7 spokes, 9 spokes preferred (1.5 T), ≥37 spokes (3 T) b |
| Artifact evaluation | No observable artifacts | No observable artifacts |
| Percent image uniformity (head coil) |
≥87.5% for 1.5 T, ≥82.0% for 3.0 T |
≥87.5 % for 1.5 T, ≥82.0 % for 3.0 T |
| Percent signal ghosting | ≤2.5% | ≤2.5 % |
| Central frequency | Vendor‐specified | Vendor‐specified (i.e. ± 500 Hz a ) |
| Transmitter gain | ±5% from baseline | Vendor‐specified (i.e. ± 0.05 dB a ) |
| Flexible RF coil testing | Individual elements, exceeds minimum vendor‐specified threshold | Vendor‐specified |
| B Mechanical, patient marking, system, and other quality assurance (QA) testing tolerances from American College of Radiology (ACR) and TG‐284 | ||
|---|---|---|
| Tolerances | ||
| QA tests | TG‐284 | ACR |
| Mechanical tests | ||
| Table movement smoothness and accuracy | ±1.0 mm from set distances | ±5.0 mm from set distance |
| Laser alignment with imaging isocenter | ±2.0 mm from expected distance offsets | NA |
| Laser movement smoothness and accuracy | ±2.0 mm from set distances | NA |
| Patient marking | ||
| Laser marking accuracy | ±2.0 mm | NA |
| System | ||
| Room temperature and humidity | Functional | Functional |
| Cold head operation | Functional | Functional |
| Cryogen level indicator | Functional | Functional |
| Other | ||
| Magnetic field homogeneity | Vendor specified across a specified DSV or <0.5 ppm volume root mean square (VRMS) over a 35 cm DSV | Vendor specified across a specified DSV (e.g. <2 ppm VRMS over a 24‐cm DSV c ) |
| RF coil evaluation | Coil and vendor dependent, ± one standard deviation from baseline for SNR, percent image uniformity, and percent signal ghosting | Coil and vendor specified for SNR, percent image uniformity, and percent signal ghosting |
| External Laser Alignment with Isocenter | ≤1 mm | NA |
a
Tolerance for Philips Ingenia 3.0 T system used for testing at our institution.
b
Tolerances are specified over all slices and for all 40 spokes per the ACR's measurement method for annual testing 2 .
c
Vendor‐specified tolerance for Philips Ingenia 3.0 T system used for testing at our institution.
Abbreviations: DSV, diameter spherical volume; NA, not applicable.