Effects of fascia lata on HIFU lesioning in vitro.

The effects of fascia lata on high intensity focused ultrasound (US), or HIFU,-induced lesions were demonstrated through comparison with and without fascia lata in bovine thigh muscle tissue. Experiments were conducted in an arrangement with a three-way multiscan ultrasonic inspection system and imaging done by B-mode US. Bovine thigh muscle (8-cm thick) was treated with 1.5 MHz for 8 s. Spatial peak intensity (ISP) was 3000 W/cm2. B-mode US imaging detected appearance at the HIFU treatment site. At a free-field intensity of 4000 W/cm2, the observed lesion length (along the axis) with fascia lata was 12 +/- 1.82 mm, compared with 4 +/- 1.54 mm for samples without fascia lata. At 3000 W/cm2, the values for samples with fascia lata and samples without fascia lata, respectively, were 13 +/- 1.50 mm and 2 +/- 1.42 mm. During a 30-s exposure, at ISP of 2000 W/cm2, the peak temperature reached 41 degrees C in samples without fascia lata and 70 degrees C in samples with fascia lata. At ISP of 3000 and 4000 W/cm2, the peak temperature reached, respectively, 73 degrees C and 84 degrees C in samples without fascia lata, compared with 102 degrees C and 104 degrees C, respectively, for samples with fascia lata. The results confirm that fascia lata contributes to increasing tissue necrosis, temperature elevation and echogenicity in US images.