The use of a segmented transducer for rib sparing in HIFU treatments
The use of a segmented transducer for rib sparing in HIFU treatments
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DOI：
10.1016/j.ultrasmedbio.2006.06.005
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发表时间：
2006-11-01
影响因子：
2.9
通讯作者：
Ter Haar, Gail
中科院分区：
文献类型：
--
作者：
Civale, John;Clarke, Robert;Ter Haar, Gail
使用聚焦超声作为肿瘤的微创治疗正在迅速扩大。靶器官包括肝脏和肾脏。单元件换能器和相控阵换能器都可用于临床。肋骨架的存在在高强度聚焦超声（HIFU）治疗计划中提出了问题，这是由于其对HIFU束的高衰减导致焦点处的功率损失以及肋骨处和覆盖组织（包括皮肤）的损伤风险增加。本文研究了一种线性分段换能器，其中所有的有源元件都是同相驱动的。本研究的目的是研究如何通过去除换能器一侧边缘段对场的贡献来实现具有临床有用轮廓的射束。我们已经考虑的情况下，在治疗过程中的HIFU束接近肋骨架和研究配置的换能器的边缘上的三个部分被关闭。这个问题已经初步研究了使用线性声场程序来模拟分段换能器的声束轮廓。换能器的声场的实验测量进行了使用自动波束绘图系统。使用细线热电偶对两种换能器配置的肋表面进行温度测量。使用热致变色液晶材料来定性地评估由超声波束产生的加热图案。我们显示了肋骨保留潜力的分割换能器在HIFU治疗过程中，通过展示减少的预聚焦宽度的超声波束时，边缘段被关闭。这已经预测与声场模型和实验证明由超声波束产生的加热模式的声场测量和观察。与所有段都处于活动状态时相比，在三个边缘段被关闭的情况下，观察到肋上的温升显著降低。我们得出结论，分段换能器扩展了治疗肝肿瘤的潜力。在肿瘤位于肋骨后面但靠近肋骨边缘的情况下，可以通过关闭边缘段来避免焦点处的能量损失以及肋骨和覆盖组织中的过度加热。
The use of focused ultrasound as a minimally invasive treatment for tumours is rapidly expanding. Target organs include the liver and kidneys. Both single element and phased array transducers may be used in the clinic. The presence of the rib cage presents a problem in high intensity focused ultrasound (HIFU) treatment planning, due to its high attenuation of the HIFU beam resulting in a loss of power at the focus as well as an increase in the risk of damage at the rib and to overlying tissues, including the skin. In this paper, a linearly segmented transducer, in which all active elements are driven in phase, has been investigated. The aim of the study was to investigate how a beam with a clinically useful profile could be achieved by removing the contribution of edge segments from one side of the transducer to the field. We have considered the case in which the HIFU beam approaches the rib cage during a treatment and investigated configurations of the transducer for which up to three segments on the edge are switched off. This problem has been studied initially using a linear acoustic field program to model the segmented transducer's acoustic beam profile. Experimental measurements of the transducer's acoustic field were performed using an automated beam plotting system. Temperature measurements were made on a rib surface for two transducer configurations using a fine wire thermocouple. A thermochromic liquid crystal material was used to assess qualitatively the heating pattern generated by the ultrasound beam. We show the rib sparing potential of the segmented transducer during HIFU treatment by demonstrating a reduction in the prefocal width of the ultrasound beam when edge segments are switched off. This has been predicted with the acoustic field model and demonstrated experimentally by acoustic field measurements and observations of the heating pattern generated by the ultrasound beam. A significant decrease in the temperature rise on a rib was observed in the case for which three edge segments were switched off compared with when all segments were active. We conclude that a segmented transducer extends the potential for treating liver tumours. In the case where the tumour lies behind, but close to the edge of, the ribs, energy loss at the focus and excessive heating in the rib and overlying tissue can be avoided by switching off edge segments.