Kirov A S, Piao J Z, Mathur N K, Miller T R, Devic S, Trichter S, Zaider M, Soares C G, LoSasso T
Department of Medical Physics, Memorial Sloan-Kettering Cancer Center, New York, NY, USA.
Phys Med Biol. 2005 Jul 7;50(13):3063-81. doi: 10.1088/0031-9155/50/13/007. Epub 2005 Jun 22.
The need for fast, accurate and high resolution dosimetric quality assurance in radiation therapy has been outpacing the development of new and improved 2D and 3D dosimetry techniques. This paper summarizes the efforts to create a novel and potentially very fast, 3D dosimetry method based on the observation of scintillation light from an irradiated liquid scintillator volume serving simultaneously as a phantom material and as a dose detector medium. The method, named three-dimensional scintillation dosimetry (3DSD), uses visible light images of the liquid scintillator volume at multiple angles and applies a tomographic algorithm to a series of these images to reconstruct the scintillation light emission density in each voxel of the volume. It is based on the hypothesis that with careful design and data processing, one can achieve acceptable proportionality between the local light emission density and the locally absorbed dose. The method is applied to a Ru-106 eye plaque immersed in a 16.4 cm3 liquid scintillator volume and the reconstructed 3D dose map is compared along selected profiles and planes with radiochromic film and diode measurements. The comparison indicates that the 3DSD method agrees, within 25% for most points or within approximately 2 mm distance to agreement, with the relative radiochromic film and diode dose distributions in a small (approximately 4.5 mm high and approximately 12 mm diameter) volume in the unobstructed, high gradient dose region outside the edge of the plaque. For a comparison, the reproducibility of the radiochromic film results for our measurements ranges from 10 to 15% within this volume. At present, the 3DSD method is not accurate close to the edge of the plaque, and further than approximately 10 mm (<10% central axis depth dose) from the plaque surface. Improvement strategies, considered important to provide a more accurate quick check of the dose profiles in 3D for brachytherapy applicators, are discussed.
放射治疗中对快速、准确和高分辨率剂量学质量保证的需求，已经超过了新型和改进的二维及三维剂量学技术的发展速度。本文总结了基于观察来自受辐照液体闪烁体体积（其同时充当体模材料和剂量检测介质）的闪烁光，来创建一种新颖且可能非常快速的三维剂量学方法的相关工作。该方法名为三维闪烁剂量学（3DSD），它利用液体闪烁体体积在多个角度的可见光图像，并将断层成像算法应用于一系列这些图像，以重建该体积中每个体素的闪烁光发射密度。它基于这样的假设：通过精心设计和数据处理，可以在局部光发射密度与局部吸收剂量之间实现可接受的比例关系。该方法应用于浸没在16.4 cm³液体闪烁体体积中的Ru - 106眼敷贴器，并将重建的三维剂量图沿选定的轮廓和平面与放射变色胶片和二极管测量结果进行比较。比较表明，在敷贴器边缘外无障碍、高梯度剂量区域的一个小体积（约4.5 mm高和约12 mm直径）内，3DSD方法与相对放射变色胶片和二极管剂量分布的一致性在大多数点上为25%以内，或在约2 mm距离内达到一致。作为对比，我们测量中放射变色胶片结果在该体积内的重现性范围为10%至15%。目前，3DSD方法在靠近敷贴器边缘以及距敷贴器表面超过约10 mm（<10%中心轴深度剂量）处不准确。文中讨论了一些改进策略，这些策略对于为近距离放射治疗施源器提供更准确的三维剂量轮廓快速检查被认为是很重要的。
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