大孔径CT模拟定位系统在放射治疗中的应用

目的：探讨大孔径CT模拟定位系统在放射治疗中的应用价值。材料和方法：分别取12位鼻咽癌和12位乳腺癌患者行欠孔径CT模拟定位，并设计放疗计划。治疗中心精度的验证：对治疗中心进行第二次层厚1．25mm扫描，并与计划治疗中心对比，测出其在X，Y，Z方向上的误差分别为dx，dy，dz，计算出实际治疗中心和计划治疗中心的距离误差Di；治疗中心准确度验证：利用EPID（电子影像系统）拍摄0°和90°单曝光高清晰验证片，通过与DRR定位片的比对和软件处理，计算出实际治疗中心与计划治疗中心在X、Y、Z方向上的误差。结果：12位鼻咽癌患者和12位乳腺癌患者按放射治疗体位要求进行CT模拟定位。治疗中心精度验证结果显示：鼻咽癌患者实际治疗中心与计划治疗中心距离误差Di=1．7mm，乳腺患者实际治疗中心与计划治疗中心距离误差Di=2．7mm。治疗中心准确度验证结果：鼻咽癌患者实际治疗中心与计划治疗中心在x轴误差为0nun；Y轴误差为0．4mm；Z轴误差为-0．4mm。乳腺癌患者实际治疗中心与计划治疗中心在x轴误差为2．0mm，Y轴误差为2．1mm，Z轴误差为-0．4mm。结论：大孔径CT模拟机不仅能够满足不同患者不同体位的扫描要求，而且定位的精确性高，完全能够满足开展3D—CRT和IMRT精确放射治疗定位的要求。

Clinical Application Of Large Bore CT Simulation in Radiation Oncology

Purpose： To discuss the clinical applying value of laige bore CT simulation in Radiation Oneology. Materials and methods： 12 NPC patients and 12 breast cancer patients are simulated by using large bore CT and planed, respectively.The precise verification of isocenter treated： all isocenters treated are secondly scaned with 1.25 cm slice thickness and compared with isocenter planed. The deviations between isocenter treated and isocenter planed in X axis （right left direction）, Y axis （superior inferior direction）, Z axis （anterior posterior direction） were dx, dy, dz, respectively. Then the distant deviations （Di） between iseeenter treated and isocenter planed are calculated.The accuracy verification of isocenter treated： Two orthogonal portal images were taken by EPID, All Portal images were registered automatically into the digitally reconstructed radiography （DRR） Then the deviations between isocenter treated and isocenter planed were calculated in X axis, Y axis , Z axis.Results： 12 NPC patients and 12 breast cancer patients are simulated in an optimal treatment position. The precise verification of iseeenter treated： the distant deviation （Di） of NPC patients between isocenter treated and isocenter planed is 1.7 mm. the distant deviation （Di） of breast cancer patients between isoeenter treated and isocenter planed is 2.7 mm. The accuracy verification of isocenter treated： the deviations of NPC patients between isocenter treated and isocenter planed in X axis, Y axis, Z axis are 0 mm, 0.4 mm, - 0.4 m, respectively.the deviations of breastcancer patients between isocenter treated and isocenter planed in X axis, Y axis , Z axis are 2.0 mm, 2.1 mm, -0.4 mm, respectively.Conclusion： Large bore CT simulation not only can satisfy to scan in an optimal treatment position, but also is accuracy.So it can fully satisfy to develop 3D- CRT and the IMRT radiotherapy.