医用直线加速器获取锥形束CT的图像空间扩展技术

Technique of image spatial extendibility for cone-beam CT on medical linear accelerator

提出了一种改进的锥形束CT(CBCT)图像获取流程,并在此基础上开发算法实现了CBCT图像的空间扩展.对实现算法进行了详细描述,并从放射剂量学角度对用于放射剂量计算可行性进行验证,相同放疗计划下对比胸部计划CT和扩展CBCT剂量计算结果表明,全肺受照射剂量大于等于20Gy的相对体积平均相差0.5%±0.22%,全肺平均受照射剂量平均相差(38.2±8.82)cGy,因此认为扩展后CBCT图像用于放射剂量计算与计划CT无显著差异.该技术拓宽了锥形束CT在影像引导放射治疗中的应用范围,提高了肿瘤放射治疗的精度,为开展自适应放疗、准确评价放疗计划提供了科学手段,有广泛的临床应用前景.由此带来的更多低剂量辐射对患者正常器官及皮肤造成的损伤有待进一步开展临床研究.

The traditional cone-beam CT （CBCT） scanning process on medical linear accelerator was improved. The CBCT image fields were rewrote to extend the image spatial length. The veraci- ties and feasibilities of this technique were validated in the dosimetric methods. Same conformal radi- ation therapy plans were added on planning CT and spatial extended CBCT respectively. Comparing the dose distribution on two different image spaces, difference on relative percentage of total-lung volume receiving dose larger than 20 Gy is 0.5% _＋0. 22% and on total-lung mean dose is （38.2 _ 8.82） cGy, which mean there are no significant dose distribution difference between planning CT and CBCT. This technique, which enlarges the CBCT field and improves the accuracy of oncology radiation therapy, would not only provide scientific method for adaptive radiation therapy plan evaluation but also has good prospect of application and extension. The complications from the additive low-dose radiation to patient＇s normal tissue and skin should be investigated in future clinical trials.