Purpose: To analyze the low dose volume regions in four facets: Analysis 1: low dose volume regions were compared between 3-dimensional conformal radiotherapy (3DCRT) and intensity modulated radiotherapy (IMRT) plans for each case; Analysis 2: the effect on low dose volume in 3DCRT as the number of fields are increased; Analysis 3: the same effect in IMRT, and Analysis 4: above two analysis were inter-compared between the two modalities.

Methods: For this work 18 patients were taken for which both 3DCRT and IMRT plans with varying number of beams were planned using Anisotropic Analytical Algorithm (AAA) in Eclipse 10 Version Treatment Planning System with two to nine beams and five to nine beams, respectively. The plans were analyzed on the basis of conformity index and dose to the critical structures.

Results: In Analysis 1, 5 Gy volume region was greater for IMRT than for 3DCRT but the 10 Gy, 15 Gy and 20 Gy volume regions were smaller for IMRT plans. In Analysis 2 and 3 shows that as the number of fields increases the low dose volume regions also increases. In Analysis 4, the effect pronounced due to increase in the beam portals is similar in 3DCRT as well as IMRT. Also it was seen that with same number of beams for both IMRT and 3DCRT, low dose volume region is higher in 3DCRT than IMRT.

Conclusion: Low dose volume regions are a major concern in 3DCRT and IMRT plans with multiple beams because of its risk of secondary cancer incidence. This study concludes that by increasing number of beams low dose volume regions increases in 3DCRT and IMRT. It shows that the low dose volume regions are slightly higher in IMRT than 3DCRT, however with proper optimization the volume of tissue receiving 10 Gy, 15 Gy and 20 Gy can be reduced.

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Cite this article as: Ekambaram V, Velayudham R. Analysis of low dose level volumes in intensity modulated radiotherapy and 3-D conformal radiotherapy. Int J Cancer Ther Oncol 2014; 2(3):02032. DOI: 10.14319/ijcto.0203.2