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Abstract
In this study, we evaluate the effect of respiration on the dose distribution in patient target volume (PTV) during intensity-modulated radiation therapy (IMRT) and research methods to reduce this impact. The dose distributions, homogeneity index (HI), coverage index (CVI), and conformity index of the PTV, which is calculated from the dose–volume histogram (DVH), are compared between the maximum intensity projection (MIP) image-based plan and other images at respiration phases of 30%, 60% and 90%. In addition, the reducing effect of complication caused by patient respiration is estimated in the case of a bolus and the expended PTV on the skin. The HI is increased by approximately twice, and the CVI is relatively decreased without the bolus at other respiration phases. With the bolus and expended PTV, the change in the dose distribution of the PTV is relatively small with patient respiration. Therefore, the usage of the bolus and expended PTV can be considered as one of the methods to improve the accuracy of IMRT in the treatment of breast cancer patients with respiratory motion.
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Fig. 1.
Breast intensity-modulated radiation therapy (IMRT) plan: (a) axial dose distribution of the breast IMRT plan without bolus, (b) axial dose distribution of the breast IMRT plan with bolus.
Fig. 2.
Dose-volume histogram (DVH) of PTV for MIPS, phase 30%, phase 60% and phase 90%: (a) DVH of the breast IMRT plan without bolus, (b) DVH of the breast IMRT plan with bolus.
Table 1.
HI, CVI and CI for breast IMRT cases with and without the bolus when original MIP image based treatment plan was projected to respiratory phase 30%, 60%, and 90% of CT image sets.
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