锥形束CT引导下调强放射治疗不同乳腺厚度的摆位误差及配准方式

The positioning error and registration methods of IMRT for breast of different thickness under guidance of CBCT

目的:分析锥形术CT(CBCT)引导下调强放射治疗(IMRT)不同乳腺厚度的摆位误差及配准方式。方法:选择行IMRT的149例乳腺癌患者,将乳腺厚度<30 mm的患者分为Ⅰ组(47例),厚度30~45 mm的患者分为Ⅱ组(63例),厚度>45 mm的患者分为Ⅲ组(39例),比较三组患者CT骨性配准和灰度配准下组间的摆位误差,并分析摆位误差的产生因素。结果:三组患者CT骨性配准和灰度配准摆位在X轴、Y轴、Z轴及冠状位(GY)中存在显著差异(t=3.424,t=4.215,t=3.643,t=3.135;P<0.05)。骨性配准下,三组患者摆位误差在Z轴和GY有显著差异(F=5.764,F=5.576;P<0.05),其中Ⅰ组Z轴误差显著大于Ⅱ组和Ⅲ组,Ⅱ组GY误差显著小于I组和Ⅲ组。灰度配准下,三组患者摆位误差无显著差异。摆位误差的主要原因为皮肤牵拉、身体扭曲(占34.80%)及患者紧张等心理因素(占19.44%)。结论:骨性配准和灰度配准的摆位误差存在差异,其中乳腺厚度对于灰度配准摆位误差影响较小。

Objective To analyze the positioning errors and registration methods of intensity modulated radiation therapy （IMRT） for breast of different thickness under guidance of cone beam CT （CBCT）. Methods： 149 patients with breast cancer who underwent IMRT were divided into group I （47 cases whose breast thickness were less than 30mm）, group II （63 cases whose breast thickness were between 30-45mm） and group III （39 cases whose breast thickness were larger than 45mm） according to breast thickness. And the positioning errors under CT diffuse idiopathic skeletal hyperostosis （DISH） registration and CT grayscale registration among three groups were compared, and the factors that affected positioning error were further analyzed. Results： The differences of positioning errors of CT DISH registration and grayscale registration at X axis, Y axis, Z axis, coronal position （GY） among three groups were significant （t=3.424, t=4.215, t=3.643, t=3.135, P〈0.05）. Under DISH registration, the differences of positioning errors at Z axis and GY among three groups were significant （F=5.764, F=5.576; P〈0.05）. And the error of Z axis of group I was significantly higher than that of group II and group III, respectively. And the error of GY of group II was significantly less than that of group I and group III, respectively. Under grayscale registration, the positioning errors among three groups were no significant. The main reasons of positioning error included skin traction, body distortion （34.80%）, tension and other psychological factors （19.44%）. Conclusion： There are differences at the positioning errors between DISH registration and grayscale registration, and breast thickness has little effect on the positioning errors of grayscale registration.