Table 1.
Number | (MPa) | (MPa) | p0 (MPa) | ILinsitu (kW∕cm2) | Wel (W) | tpulse (ms) | PRF (Hz) | DFb | tb (ms) |
---|---|---|---|---|---|---|---|---|---|
Polyacrylamide gel phantom | |||||||||
76 | 13.5 | 0.57 | 19.5 | 250 | 10 | 1 | 0.01 | 3.8 | |
Bovine heart tissue | |||||||||
1 | 45 | 9.0 | 0.37 | 7.23 | 110 | 10 | 1 | 0.01 | N∕A |
2 | 61 | 11.0 | 0.46 | 11.23 | 164 | 10 | 1 | 0.01 | 8.1 |
3 | 67 | 12.0 | 0.55 | 16 | 236 | 10 | 1 | 0.01 | 4.5 |
4 | 67 | 12.0 | 0.55 | 16 | 236 | 10 | 0.3–100 | 0.003–1 | 4.5 |
5 | 67 | 12.0 | 0.55 | 16 | 236 | 0.2–100 | 0.1–50 | 0.01 | 4.5 |
The HIFU frequency was 2.158 MHz and the initial pressure at the surface of the transducer, p0, was estimated using low amplitude measurements and modeling (Ref. 11). The in situ peak intensity at the focus was calculated assuming linear propagation, IL, as , where G = 48 is the linear focusing gain of the transducer in water, α0 is ultrasound attenuation coefficient, and L is depth of the focus in tissue. In situ values for peak compression and peak rarefaction pressures, p + and p−, were determined from the measured waveforms and corrected via modeling to compensate for the limited bandwidth of the FOPH (Ref. 10).
Duty factor.