| Objective This study was designed to investigate the safety, efficacy and feasibility of using focused ultrasound surgical clamp (FUSC) for bloodless hepatectomy, and to provide significant data for this novel surgical instrument in liver resection and its clinical application.Methods (1)A FUSC was comprised of two ultrasound transducers fixed on a forceps-like handle. The directions of focused ultrasound beams produced by both transducers were opposite, with the same central axes. Ultrasound energy was continuously delivered by ether single transducer or two transducers to ablate in vitro bovine liver located between both transducers. The frequency was 1.6MHz, and the acoustic power was 150W. The thickness of in vitro bovine liver ranged from 4 to 10cm. The characteristics of complete coagulation necrosis and exposure time were measured after FUSC exposure, and pathological changes in the treated bovine liver tissue were observed. (2)After anaesthesia was performed, five healthy goats underwent laparotomy, and then the liver was totally exposed for an ablative procedure. The FUSC (acoustic power: 150W, frequency: 1.6MHz) was used to ablate the liver with various thickness. The characteristics of coagulation necrosis and exposure time were recorded after FUSC exposure, and pathological changes in the treated liver tissue were observed.(3)After surgical exposure, the FUSC (acoustic power: 150W, frequency: 1.6 MHz) was used in 10 goats to ablate a predetermined liver tissue along with a resection line, followed by the left lobectomy. The shape and size of the ablated tissue, blood loss, and the time required for the hepatectomy were recorded. Histological changes were observed in the removed liver, and 5ml blood samples were collected in each goat to measure blood cells and hepatic and renal functions after surgical procedure.Results (1)FUSC exposure with 2 transducers was able to induce complete coagulation necrosis in all thickness of bovine liver samples. The size of coagulation necrosis was corresponded with the FUSC focus, with 2.72～3.20 cm in length and 1.44～1.80 cm in width. However, under the same exposure energy, exposure time required for complete necrosis increased while the thickness of the liver increased. Furthermore, FUSC exposure with 1 transducer could induce complete necrosis in the 4-6cm thickness of the bovine liver. However, it was unable to cause complete damage in the 8-10cm thickness of the bovine liver. (2) FUSC induced complete coagulation necrosis of ex vitro liver in all goats. The size of coagulation necrosis was corresponded with the FUSC focus, with 2.54～2.60 cm in length and 1.84～1.94 cm in width. Under the same exposure energy, exposure time required for complete necrosis increased while the thickness of the liver increased. Pathological examination showed coagulation necrosis of the targeted liver tissue, and small blood vessels were severely destroyed, with the occlusion of the ablated vessels(.3)Liver resection was successfully performed in all animals. The size of coagulation necrosis was 7.4±1.2cm in length,1.9±0.2 in width, and 2.8～3.0cm in thickness. Mean FUSC exposure time was 270 seconds and the time for liver resection was 5～14 minutes. Average blood loss was 10～30ml during liver resection. After surgical procedure, all animals survived well with normal renal function. A transient increase of serum ALT and AST was immediately seen in all goats, and they reduced to a normal level 7 days after surgery. No complications were observed during follow-up period.Conclusion (1)FUSC exposure with 2 transducers can induce complete coagulation necrosis of targeted bovine liver with various thicknesses. Two-transducer exposure is much better than one-transducer exposure in terms of local deposition of ultrasound energy and ablation efficiency. ( 2 ) FUSC can induce complete coagulation necrosis of predetermined liver in all goats with the occlusion of small blood vessels.(3)FUSC used in assisting hepatectomy procedure is safe, effective and feasible. It can significantly reduce blood loss, decrease operation time, and be easy to perform during procedure. It will provide a novel surgical instrument for bloodless liver resection.
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