Table 1.
(a) Magnet and gradient design specifications of the compact 3.0T specialty MRI scanner compared to that of typical whole-body 3.0T MRI scanners. (b) Performance characteristics of the asymmetric gradient design. Although the maximum simultaneous gradient performance is 85 mT/m at 750 T/m/s, the system operates at a nominal 80 mT/m at 700 T/m/s to provide sufficient head-room for eddy current, linear shim, and concomitant gradient corrections.
| (a) | ||
|---|---|---|
| Whole-body 3.0T MRI | Compact 3.0T MRI | |
| Imaging FOV | 45–50 cm DSV | 26 cm DSV |
| Length | 160–175 cm | 126 cm |
| Width (OD) | 190–200 cm | 162 cm |
| Warm bore (ID) | 88–92 cm | 62 cm |
| Weight | 5,500 – 8,000 kg | <1,900 kg |
| Liquid Helium volume | 1,500–2,000 liters | 12 liters |
| 5G fringe field from center | 3 m × 5 m | 2 m × 3 m |
| Target field homogeneity (p-p) | < 1ppm (45–50 cm FOV) | < 1 ppm (26 cm DSV) |
| Gradient | ||
| Slew rate | 200 T/m/s | 700 T/m/s |
| Gradient amplitude | 50–80 mT/m | 80 mT/m |
| Inner diameter | 65–75 cm | 42 cm |
| Patient bore (head with RF coil) | 60–70 cm | 37 cm |
| Patient bore (shoulders) | 60–70 cm | 60 cm |
| Weight | 500–1,000 kg | 250 kg |
| (b) | |
|---|---|
| Gradient Coil Characteristic | Performance |
| Inner diameter | 42 cm |
| Outer diameter | 59 cm |
| Length | 92 cm |
| Linearity over 26-cm DSV | < 17% |
| Uniformity over 26-cm DSV | < 52% |
| Maximum driver current | 660 A |
| Nominal driver current | 620 A |
| Coil gain (gradient efficiency, η) [x y z] | 0.129/0.129/0.132 mT/m/A |
| Inductance, L [x y z] | 0.234/0.204/0.186 mH |
| Maximum slew rate @ 85 mT/m at 1500V | 708 T/m/s |
| Post-compensated eddy current [x y z] | < 0.08% |
| Net force at 660 A [x y z] | < 100 N |
| Net torque at 660 A [x y z] | < 50 Nm |
| Thermal capacity (cooling) | 25 kW continuous |
| Gr.m.s. at 100% duty cycle (at 320A r.m.s.) | 40 mT/m |