Table 1.

Summary of exposure parameters in gel and in bovine heart tissue.^a

Number	$p_{\mathit{in}\mathit{situ}}^{+}$ (MPa)	$p_{\mathit{in}\mathit{situ}}^{-}$ (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

^aThe 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, I_L, as $I_L=(p_0^2∕2{\rho }_0{c}_0)G^2\exp (-2{\alpha }_{0}L)$, 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).

^bDuty factor.