孔径调制，平移床全身放射治疗。

Aperture modulated, translating bed total body irradiation.

机构信息

Department of Medical Physics, Tom Baker Cancer Centre, Calgary, Alberta T2N 4N2, Canada.

出版信息

Med Phys. 2011 Feb;38(2):932-41. doi: 10.1118/1.3534196.

DOI:10.1118/1.3534196

PMID:21452729

Abstract

PURPOSE

Total body irradiation (TBI) techniques aim to deliver a uniform radiation dose to a patient with an irregular body contour and a heterogeneous density distribution to within +/-10% of the prescribed dose. In the current article, the authors present a novel, aperture modulated, translating bed TBI (AMTBI) technique that produces a high degree of dose uniformity throughout the entire patient.

METHODS

The radiation beam is dynamically shaped in two dimensions using a multileaf collimator (MLC). The irregular surface compensation algorithm in the Eclipse treatment planning system is used for fluence optimization, which is performed based on penetration depth and internal inhomogeneities. Two optimal fluence maps (AP and PA) are generated and beam apertures are created to deliver these optimal fluences. During treatment, the patient/phantom is translated on a motorized bed close to the floor (source to bed distance: 204.5 cm) under a stationary radiation beam with 0 degree gantry angle. The bed motion and dynamic beam apertures are synchronized.

RESULTS

The AMTBI technique produces a more homogeneous dose distribution than fixed open beam translating bed TBI. In phantom studies, the dose deviation along the midline is reduced from 10% to less than 5% of the prescribed dose in the longitudinal direction. Dose to the lung is reduced by more than 15% compared to the unshielded fixed open beam technique. At the lateral body edges, the dose received from the open beam technique was 20% higher than that prescribed at umbilicus midplane. With AMTBI the dose deviation in this same region is reduced to less than 3% of the prescribed dose. Validation of the technique was performed using thermoluminescent dosimeters in a Rando phantom. Agreement between calculation and measurement was better than 3% in all cases.

CONCLUSIONS

A novel, translating bed, aperture modulated TBI technique that employs dynamically shaped MLC defined beams is shown to improve dose uniformity in three dimensions. In comparison with the fixed open beam TBI technique, homogeneity of dose distribution is greatly improved.

摘要

目的

全身照射（TBI）技术旨在将不均匀的体轮廓和不均匀的密度分布的患者的辐射剂量均匀地输送至处方剂量的正负 10%范围内。在本文中，作者提出了一种新颖的、孔径调制的平移床 TBI（AMTBI）技术，该技术可在整个患者中产生高度均匀的剂量。

方法

使用多叶准直器（MLC）在二维方向上动态地形成辐射束。Eclipse 治疗计划系统中的不规则表面补偿算法用于进行适形优化，该算法基于穿透深度和内部不均匀性进行优化。生成两个最佳的通量图（AP 和 PA），并创建光束孔径以输送这些最佳通量。在治疗过程中，患者/体模在靠近地板的电动床上进行平移（源到床的距离：204.5cm），在静止的辐射束下，0 度机架角。床运动和动态光束孔径同步进行。

结果

AMTBI 技术比固定的开放式平移床 TBI 产生更均匀的剂量分布。在体模研究中，沿中线的剂量偏差从纵向的 10%减少到规定剂量的 5%以下。与未屏蔽的固定开放式光束技术相比，肺剂量减少了 15%以上。在身体侧面边缘，从开放式光束技术接收的剂量比脐平面中线的规定剂量高 20%。使用 AMTBI，同一区域的剂量偏差减少到规定剂量的 3%以下。在 Rando 体模中使用热释光剂量计对该技术进行了验证。在所有情况下，计算与测量之间的一致性均优于 3%。