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Published in Harald Paganetti, Proton Therapy Physics, 2018
Peter van Luijk, Marco Schippers
Direct comparison of 3D dose distributions of alternative treatment plans is very inconvenient. Therefore, present practice is to summarize the 3D dose distribution in a dose–volume histogram (DVH). For each (relative) dose level, this histogram gives the volume that receives that dose (Figure 23.1D). In practice, the cumulative DVH, giving the volume receiving more than a certain dose as a function of that dose, is reported by treatment planning systems (Figure 23.1E). Even though a DVH discards a lot of information as compared to the 3D dose distribution, at present, this DVH is the starting point for the derivation of figures of merit, based on which the treatment plan can be optimized. Classically, individual DVH points, the mean dose or generalized forms of the mean dose are used for this. However, since the relation of these figures of merit to clinical outcome is not trivial, large efforts have been made to develop and use models explicitly describing the risk of normal tissue damage instead.
New Dosimetry Materials, Devices, and Systems
Published in Siyong Kim, John Wong, Advanced and Emerging Technologies in Radiation Oncology Physics, 2018
Generally, 2D dosimetric QA provides insufficient information on the highly complex IMRT/VMAT delivery. For in-depth evaluation, it is recommended that the clinical relevance of dose-volume values for targets and critical structures from the dose-volume histogram (DVH) curves be analyzed (Nelms et al., 2011). This can be achieved through dose reconstruction using a 3D volumetric CT scan of phantom or patient using the existing 2D measured dose maps. This method is more desirable than the conventional pretreatment QA techniques because dosimetric errors can be evaluated more thoroughly in 3D space.
Integration of biological and statistical models toward personalized radiation therapy of cancer
Published in IISE Transactions, 2019
Xiaonan Liu, Mirek Fatyga, Teresa Wu, Jing Li
The goal of NTCP modeling is to link the radiation dose delivered to a normal tissue/organ (not the organ with cancer) with the risk/probability that the normal organ will develop a complication. In this article, we focus on the rectum, which is a normal organ that could develop a complication from radiation toxicity, for patients with prostate cancer. For each patient, treatment planning software generates a three-dimensional (3-D) dose map, which contains the radiation dose value on each voxel of a 3-D image (CT or MRI) of the rectum. In biological NTCP models, the 3-D dose map is first converted to a Dose-Volume-Histogram (DVH) by binning the voxel-wise dose values. Figure 1 shows an example of a DVH, in which the horizontal axis corresponds to dose values from low to high; the vertical axis is the fraction of voxels (i.e., volume) of the rectum that receive a certain dose.