| Objective: High-intensity focused ultrasound (HIFU) is a new non-invasive technique to treat solid tumors. Experimental investigations has manifested that it can destruct tissues precisely. And it has clinically used to treat hepatocarcinoma, osteosarcoma, breast cancer, prostate cancer and etc. The literature had reported investigations of treating tumors on uterine wall of rabbit or rat with HIFU. Since Rhesus's genital system and genital physiology is similar to those of human, it is the most appropriate animal for experiment. In this study, tumor-like proliferation in Rhesas's uterus was treated using HIFU. The objective of this study was to determine the efficiency and safety of this non-invasive technique. Materials and methods: 16 female Rhesus were inspected in their breeding season and non-breeding season using B-mode ultrasound and MRI, the signals and dimensions of uterus being recorded; and the sizes of uteri were measured in 3 animals after laparotomy procedures. It was found that there was no significant difference between the uterine diameters determined by B-mode ultrasound or MRI and that measured under gross inspection (P＞0.05). B-mode ultrasound and MRI could clearly display uterine blood stream and echo reflecting response of uterine wall, so they were appropriate approaches to guide and follow up HIFU therapy of uterine leiomyoma. In order to establish the model of smooth muscle tumor-like proliferation in monkey uterus, Estradiolbenzoate (2 mg/time, 3 time/weekly, 3 months) and progesterone (5 mg/time, 2 time/weekly, 1 month) were administered in 12 monkeys for one course. After medication, their uteri were enlarged, and the pathology changes were similar to uterine leiomyoma in human. Results: The tumor-like proliferation of uterus in 11 monkeys was treated with HIFU. Results showed that HIFU could be precisely focused on target tissue to induce irreversible coagulative necrosis, which was confirmed by histology and microscopic examinations. Enzyme (SDH, G-6-P, ACP) stain was negative, showing that enzyme activity lost, and elastic fibers and collagen fibers stain was negative. The surrounding tissue was normal and the enzyme stain was positive. Oxytocin and rectal bracket using in treatment could improve the safety and efficiency. After HIFU treatment, ovarian function of the animals was not affected and pregnancy occurred in 40%. Follow-up procedures were performed after HIFU therapy using MRI and pathologic examination. They showed that the coagulative necrosis was shrunk and absorbed gradually, being replaced by thin fibrous tissue. Three months after HIFU, the necrosed region disappeared. Clinical treatment of leiomyoma in 7 patients using HIFU was investigated. The systemic stress reaction and hospitalized duration of patients were less than those of patients having hysterectomy. Clinical symptoms were alleviated and myoma volumes of patients decreased after receiving HIFU. Oxytocin and rectal bracket could protect uterine peripheral tissues and nerves against damage. Conclusion: The tumor-like proliferation model of monkeyuterus could meet the need of the experiment of treating uterine myoma using HIFU. HIFU could be precisely focused on target tissue on monkey uterus to induce coagulative necrosis, and had no damage to peripheral tissue. Combined with oxytocin and rectal bracket, safety and efficacy of treatment could be improved further. The ovarian function was satisfactorily preserved. Preliminary clinical application showed that it is safe and effective to treat uterine leiomyoma with HIFU.
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