以超音波燒灼肝臟腫瘤過程之模擬

Abstract

肝癌涉及肝臟內某些細胞不正常且大量的增生之現象。基於非侵入式的優 點，超音波熱治療是肝癌治療的理想方式之一。過往研究所建立的幾何模型大多 以規則的外型為主，本研究利用MRI 所切片重建的肝臟外型，並保留主要的動脈 血管，探討肝腫瘤在血管附近的超音波燒灼問題，三維血液灌流效應對超音波熱 治療的影響，即當熱傳導效應將熱從超音波聚焦處帶至血管附近時，會因血液的 流動把些許的熱能帶走。 由於組織的吸收參數對於組織的吸熱有著顯著的影響，因此整理文獻資料並 比較肝腫瘤在不同吸收參數時的組織的吸熱情況。當腫瘤的吸收參數較大時，使 用超音波照射12 秒，腫瘤內最高溫度為83°C；當腫瘤的吸收參數較小時，腫瘤內 最高溫度為62°C ，由於人體內此一參數取得不易，所以在模擬之前取得適當的參 數對模擬的正確性是必要的。

Hepatocellular carcinoma is a group of diseases in which cells are aggressive. Because of the advantage of focused ultrasound surgery(FUS), which is a non-invasive system, the focused ultrasound surgery becomes one of the ideal ways to kill the tumor. Most of the geometrical models considered in the previous studies were regular. In this study, the liver model containing a liver, blood vessel(artery), and a liver tumor, which is closed to the blood vessels, and considered. Since the presence of blood perfusion can limit the ability of elevating the temperature owing to convective heat transport, the reduction of lesion area is investigated. Tissue absorbing coefficients play an important role in raising tumor temperature. The range of the absorbing coefficients (liver tumor) is 0.0529(nepes/cm/MHz) to 0.1473(nepes/cm/MHz). After exposing to a high intensity focused ultrasound(HIHU) for 12sec, the highest temperature with large absorbing coefficient can reach 83°C , and the highest temperature with a lower absorbing coefficient is predicted to be 62°C . It is difficult to get the coefficients in human body. Prior to the simulation, to acquire the absorbing coefficients is essential to predict good quality solution.