雙相位陣列超音波換能器應用於乳房腫瘤熱手術之探討

Abstract

此研究目的為探討使用兩個相位陣列式超音波換能器經由快速切換不同聚焦點於乳房腫瘤之熱治療。使用換能器之驅動頻率、曲率半徑、長度、寬度分別為1.0MHz、15cm、16cm及1.5cm。這兩個相位陣列式換能器以24cm的距離環繞著乳房面對面設置，而換能器的共焦中心點設定在規劃目標區(PTV)的中心位置。依照腫瘤的寬度以2mm的間距規劃出多個單一聚焦點，由左至右依序加熱，當目標區達到某一合適加熱時間後，換能器以水平的方式旋轉90°後，同樣以2mm的間距規劃出多個單一聚焦點繼續加熱，使目標區形成一個適當的治療體積且不傷到正常組織。在此，本研究以電腦模擬的方式探討治療區(PTV)內血流的影響、旋轉前後的加熱時間比、腫瘤位於皮膚表面淺層位置的規劃治療，以及將換能器傾斜角度後對肋骨的影響。實驗的材料使用變色仿體和新鮮的里肌肉進行離體實驗。由實驗結果顯示，此加熱系統可在目標區內形成一個均勻的治療單元，也證實當換能器平行於肋骨時可減少肋骨部位的溫升，淺層部位的加熱可使用水溫進行冷卻，減少皮膚熱量的累積。從研究的結果顯示，使用兩個相位陣列超音波換能器做適當的配置與加熱規劃可以形成一均勻治療單元，且有效減少肋骨與皮膚的溫升。

The purpose of this study was to investigate the feasibility of using two curved ultrasound phased arrays with a rapid focus-scanning scheme for breast tumor thermal therapy. The driving frequency, radius of curvature, length and width of the phased arrays are 1.0 MHz, 15 cm, 16 cm and 1.5 cm, respectively. The two curved arrays were arranged face-to-face with a distance of 24 cm, and the breast was set between the two arrays to have the planning target volume (PTV) located at the center. The foci of the phased arrays were located at the PTV and scan sequentially. After an appropriate sonication time, the set of arrays was rotated 90 degree and then continued the sonication to achieve a uniform heating for the PTV without overheating the normal tissues. The location of PTV, blood perfusion rate, the ratio of sonication time before and after the rotation, and a superficial PTV has been studied. The computer simulation and experiments with color-changeable phantom and flesh pork phantom had been used to evaluate the proposed heating system. The results indicated that the heating system was able to create a uniform heating in the PTV with a minimum acoustic power deposition in ribs due to the acoustic beam parallel to the ribs. In addition, the temperature rise on the breast surface could be minimized since a sufficient acoustic window was used for the proposed heating system. A shallow PTV could even be heated as a low temperature of cooling water was used. The results of this study showed that the two ultrasound phased-arrays with a suitable arrangement and heating scheme was able to achieve a uniform heating for breast tumor thermal therapy without overheating the ribs and the skin within a short treatment time.