Papoutsis Iosif, Skjei Knudtsen Ingerid, Peter Skaug Sande Erlend, Louni Rekstad Bernt, Öllers Michel, van Elmpt Wouter, Røthe Arnesen Marius, Malinen Eirik
Department of Physics, University of Oslo, P.O. Box 1048 Blindern, N-0316 Oslo, Norway.
Department of Medical Physics, Oslo University Hospital, P.O. Box 4953 Nydalen, N-0424 Oslo, Norway.
Phys Imaging Radiat Oncol. 2022 Feb 26;21:101-107. doi: 10.1016/j.phro.2022.02.013. eCollection 2022 Jan.
Dose painting by numbers (DPBN) require a high degree of dose modulation to fulfill the image-based voxel wise dose prescription. The aim of this study was to assess the dosimetric accuracy of F-fluoro-2-deoxy-glucose positron emission tomography(F-FDG-PET)-based DPBN in an anthropomorphic lung phantom using alanine dosimetry.
A linear dose prescription based on F-FDG-PET image intensities within the gross tumor volume (GTV) of a lung cancer patient was employed. One DPBN scheme with low dose modulation (Scheme A; minimum/maximum fraction dose to the GTV 2.92/4.26 Gy) and one with a high modulation (Scheme B; 2.81/4.52 Gy) were generated. The plans were transferred to a computed tomograpy (CT) scan of a thorax phantom based on CT images of the patient. Using volumetric modulated arc therapy (VMAT), DPBN was delivered to the phantom with embedded alanine dosimeters. A plan was also delivered to an intentionally misaligned phantom. Absorbed doses at various points in the phantom were measured by alanine dosimetry.
A pointwise comparison between GTV doses from prescription, treatment plan calculation and VMAT delivery showed high correspondence, with a mean and maximum dose difference of <0.1 Gy and 0.3 Gy, respectively. No difference was found in dosimetric accuracy between scheme A and B. The misalignment caused deviations up to 1 Gy between prescription and delivery.
DPBN can be delivered with high accuracy, showing that the treatment may be applied correctly from a dosimetric perspective. Still, misalignment may cause considerable dosimetric erros, indicating the need for patient immobilization and monitoring.
数字剂量描绘（DPBN）需要高度的剂量调制以实现基于图像的体素级剂量处方。本研究的目的是使用丙氨酸剂量测定法评估基于氟-2-脱氧葡萄糖正电子发射断层扫描（F-FDG-PET）的DPBN在人体肺部模型中的剂量测定准确性。
采用基于肺癌患者大体肿瘤体积（GTV）内F-FDG-PET图像强度的线性剂量处方。生成了一种低剂量调制的DPBN方案（方案A；GTV的最小/最大分次剂量为2.92/4.26 Gy）和一种高调制方案（方案B；2.81/4.52 Gy）。根据患者的CT图像，将计划转移到胸部模型的计算机断层扫描（CT）上。使用容积调强弧形放疗（VMAT），将DPBN输送到嵌入丙氨酸剂量计的模型中。还将一个计划输送到故意错位的模型中。通过丙氨酸剂量测定法测量模型中各个点的吸收剂量。
处方、治疗计划计算和VMAT输送的GTV剂量之间的逐点比较显示出高度一致性，平均和最大剂量差异分别<0.1 Gy和0.3 Gy。方案A和方案B在剂量测定准确性方面未发现差异。错位导致处方和输送之间的偏差高达1 Gy。
DPBN可以高精度地输送，表明从剂量测定的角度来看，该治疗方法可以正确应用。尽管如此，错位可能会导致相当大的剂量测定误差，这表明需要对患者进行固定和监测。
