Ho Cheng-Shiao, Ju Kuen-Cheng, Cheng Tze-Yuan, Chen Yung-Yaw, Lin Win-Li
Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan.
Phys Med Biol. 2007 Aug 7;52(15):4585-99. doi: 10.1088/0031-9155/52/15/015. Epub 2007 Jul 10.
The purpose of this study is to investigate the feasibility of using a 1 MHz cylindrical ultrasound phased array with multifocus pattern scanning to produce uniform heating for breast tumor thermal therapy. The breast was submerged in water and surrounded by the cylindrical ultrasound phased array. A multifocus pattern was generated and electrically scanned by the phased array to enlarge the treatment lesion in single heating. To prevent overheating normal tissues, a large planning target volume (PTV) would be divided into several planes with several subunits on each plane and sequentially treated with a cooling phase between two successive heatings of the subunit. Heating results for different target temperatures (T(tgt)), blood perfusion rates and sizes of the PTV have been studied. Furthermore, a superficial breast tumor with different water temperatures was also studied. Results indicated that a higher target temperature would produce a slightly larger thermal lesion, and a higher blood perfusion rate would not affect the heating lesion size but increase the heating time significantly. The acoustic power deposition and temperature elevations in ribs can be minimized by orienting the acoustic beam from the ultrasound phased array approximately parallel to the ribs. In addition, a large acoustic window on the convex-shaped breast surface for the proposed ultrasound phased array and the cooling effect of water would prevent the skin overheating for the production of a lesion at any desired location. This study demonstrated that the proposed cylindrical ultrasound phased array can provide effective heating for breast tumor thermal therapy without overheating the skin and ribs within a reasonable treatment time.
本研究的目的是探讨使用具有多焦点模式扫描的1兆赫圆柱形超声相控阵为乳腺肿瘤热疗产生均匀加热的可行性。将乳房浸入水中，并被圆柱形超声相控阵包围。相控阵产生多焦点模式并进行电扫描，以在单次加热中扩大治疗病灶。为防止正常组织过热，将大的计划靶体积（PTV）划分为几个平面，每个平面上有几个亚单元，并在亚单元的两次连续加热之间进行冷却阶段的顺序治疗。研究了不同靶温度（T(tgt)）、血液灌注率和PTV大小的加热结果。此外，还研究了不同水温下的浅表乳腺肿瘤。结果表明，较高的靶温度会产生稍大的热损伤，较高的血液灌注率不会影响加热损伤大小，但会显著增加加热时间。通过使超声相控阵的声束大致平行于肋骨方向，可以将肋骨中的声功率沉积和温度升高降至最低。此外，所提出的超声相控阵在凸形乳房表面上的大的声窗以及水的冷却作用将防止皮肤过热，从而在任何期望位置产生损伤。本研究表明，所提出的圆柱形超声相控阵能够在合理的治疗时间内为乳腺肿瘤热疗提供有效的加热，而不会使皮肤和肋骨过热。
