Table 1. Treatment parameters, estimated in situ peak rarefaction pressures, and results of third ventriculostomies in 9 swine treated using the ExAblate 4000 MRIgFUS system.
| Frequency (kHz) |
Acoustic Power (W) |
Simulated (MPa) |
dT/dt (MPa)* |
McDannold (MPa)† |
Pulse Duration (sec) |
No. of Pulses |
Successful? | Size (mm) |
Vessel Damage (mm) |
Rim of Damage (mm) |
|---|---|---|---|---|---|---|---|---|---|---|
| 650 | 1000 | 27.5 | 15.7 | 15.0 | 0.1 | 1 | yes | 2.3 | 0.9 | 0.9 |
| 650 | 2200 | 29.8 | 17.0 | 16.2 | 0.1 | 2 | no | |||
| 650 | 1500 | 36.1 | 20.6 | 19.6 | 0.3 | 3 | no | |||
| 650 | 1000 | 39.7 | 22.7 | 21.6 | 1 | 1 | yes | 6.6 | 0.6 | 0.6 |
| 650 | 2000 | 44.7 | 25.5 | 24.4 | 1 | 1 | yes | 9.2 | 1.5 | 0.7 |
| 650 | 2000 | 47.0 | 26.8 | 25.6 | 1 | 1 | yes | 9.3 | 0.4 | 0.4 |
| 650 | 1500 | 50.4 | 28.8 | 27.4 | 1 | 1 | yes | 8.5 | 1 | 0.6 |
| 650 | 1900 | 20.6 | 11.8 | 11.2 | 5 | 1 | no | |||
| 230 | 2900 | 16.3 | 9.3 | 8.8 | 1 | 1 | yes | 4.7 | 3.2 | 0.7 |
*
The error was estimated to be ± 9% without skull and ± 22% with skull. This method extended to 230 kHz assumed a gain proportional to frequency. The error was attributable to the uncertainty in the physical parameters used in the model, as well as the measurement error in skull transmission.
†
The calibration error was reported to be ± 10%,21 leading to an estimate of ± 24% for our measurements. The increased error is due to the combination of uncertainty in the transmission through skull, the attenuation of brain tissue, and the intensity loss due to steering. This method extended to 650 kHz similarly assumed an increased gain proportional to the frequency.