全身照射中患者特定剂量模式。

Patterns of patient specific dosimetry in total body irradiation.

机构信息

Department of Radiation Oncology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA.

出版信息

Med Phys. 2013 Apr;40(4):041719. doi: 10.1118/1.4795335.

DOI:10.1118/1.4795335

PMID:23556889

Abstract

PURPOSE

Total body irradiation (TBI) has been used for bone marrow transplant for hematologic and immune deficiency conditions. The goal of TBI is to deliver a homogeneous dose to the entire body, with a generally accepted range of dose uniformity being within ± 10% of the prescribed dose. The moving table technique for TBI could make dose uniform in whole body by adjusting couch speed. However, it is difficult to accurately estimate the actual dose by calculation and hence in vivo dosimetry (IVD) is routinely performed. Here, the authors present patterns of patient-specific IVD in 161 TBI patients treated at our institution.

METHODS

Cobalt-60 teletherapy unit (Model C9 Cobalt-60 teletherapy unit, Picker X-ray Corporation) with customized moving bed (SITI Industrial Products, Inc., Fishers, IN) were used for TBI treatment. During treatment, OneDose(TM) (Sicel Technology, NC) Metal Oxide-silicon Semiconductor Field Effect Transistor detectors were placed at patient body surface; both entrance and exit side of the beam at patient head, neck, mediastinum, umbilicus, and knee to estimate midplane dose. When large differences (>10%) between the prescribed and measured dose were observed, dose delivery was corrected for subsequent fractions by the adjustment of couch speed and/or bolus placement. Under IRB exempt status, the authors retrospectively analyzed the treatment records of 161 patients who received TBI treatment between 2006 and 2011.

RESULTS

Across the entire cohort, the median ± SD (range) percent variance between calculated and measured dose for head, neck, mediastinum, umbilicus, and knee was -2.3 ± 10.2% (-66.2 to +35.3), 1.1 ± 11.5% (-62.2 to +40.3), -1.9 ± 9.5% (-66.4 to +46.6), -1.1 ± 7.2% (-35.2 to +42.9), and 3.4 ± 12.2% (-47.9 to +108.5), respectively. More than half of treatments were within ± 10% of the prescribed dose for all anatomical regions. For 80% of treatments (10%-90%), dose at the umbilicus was within ± 10%. However, some large differences greater than 35% were also found at several points. For one case, the knee received double the prescribed dose. When the dose differences for multiple fractions were averaged, compliance (± 1 0%) between the prescription and measured dose was improved compared to the dose difference of the first single fraction, for example, as at umbilicus, which improved from 83.9% to 98.5%.

CONCLUSIONS

Actual dose measurement analysis of TBI patients revealed a potentially wide variance from the calculated dose. Based from their IVD method for TBI using Cobalt-60 irradiator and moving table, ± 10% over entire body is hard to achieve. However, it can be significantly improved with immediate feedback after the first fraction prior to subsequent treatments.

摘要

目的

全身照射（TBI）已被用于治疗血液学和免疫缺陷疾病的骨髓移植。TBI 的目的是向全身提供均匀的剂量，通常接受的剂量均匀性范围在规定剂量的±10%以内。TBI 的移动床技术可以通过调整治疗床速度使全身剂量均匀。然而，通过计算准确估计实际剂量是困难的，因此通常进行体内剂量测定（IVD）。在此，作者介绍了在我院治疗的 161 例 TBI 患者的特定患者 IVD 模式。

方法

使用定制的移动床（SITI Industrial Products，Inc.，Fishers，IN）的钴-60远距离治疗机（Model C9 Cobalt-60 teletherapy unit，Picker X-ray Corporation）进行 TBI 治疗。在治疗过程中，在患者身体表面放置 OneDose（TM）（Sicel Technology，NC）金属氧化物-硅半导体场效应晶体管探测器；在患者头部、颈部、纵隔、脐部和膝关节的射束入口和出口侧放置探测器，以估计中平面剂量。当观察到规定剂量和测量剂量之间存在较大差异（>10%）时，通过调整治疗床速度和/或放置填充物来纠正随后的分次剂量。在 IRB 豁免状态下，作者回顾性分析了 2006 年至 2011 年间接受 TBI 治疗的 161 例患者的治疗记录。

结果

在整个队列中，头部、颈部、纵隔、脐部和膝关节的计算剂量与测量剂量之间的中位数±SD（范围）百分比差异分别为-2.3±10.2%（-66.2 至+35.3）、1.1±11.5%（-62.2 至+40.3）、-1.9±9.5%（-66.4 至+46.6）、-1.1±7.2%（-35.2 至+42.9）和 3.4±12.2%（-47.9 至+108.5）。超过一半的治疗剂量在所有解剖区域都在规定剂量的±10%以内。对于 80%的治疗（10%-90%），脐部的剂量在±10%以内。然而，也在几个点发现了一些大于 35%的较大差异。对于一个病例，膝关节接受了两倍于规定的剂量。当将多个分次的剂量差异平均化时，与测量剂量的处方相比，（±10%）的符合率得到了改善，例如在脐部，从 83.9%提高到 98.5%。