AIM: Modern radiotherapy attempts to improve the dose distribution to conform the high dose region to the planning target volume (PTV). The present work aimed to assess which clinicodosimeteric scenario could benefit the more from IMRT as compared to three dimensional conformal radiation therapy (3DCRT).MATERIAL AND METHODS:The number of organs at risk (OARs) overlapping the planning target volume (PTV) was the parameter describing the clinical dosimetric pattern. Twenty four previously irradiated patients of high grade gliomas were retrieved and replanned with both 3DCRT and IMRT. The cases were divided into 4 groups( 6 patients in each group). Each group represents a scenario where 0, 1, 2 or 3 OARs overlapped the target volume respectively. A total dose of 60 GY was delivered with a dose/fraction of 2 GY, five fractions weekly. The dose was normalized to the isocentre.RESULTS:We compared the average values of the dosimeteric parameters for the four groups. We observed that the group where OARs overlapping were 0, the TV95% and HI were roughly equal for the 3DCRT and IMRT plans. For group 2 where 1 OARs overlapped ,the TV95% for the IMRT plan was 96.50 % versus 96.03 % for 3DCRT.For group 3, where 2 OARs overlapped the dosimeteric plans were competitive. The IMRT plan had better TV95% (96.53 %) as compared to 3DCRT(94.82%).For group 4, where number of OARs overlap was 3, the IMRT dosimeteric plan were better with TV95% (96.78 %) and HI values (1.072) and the TV95% values(92.89 %) and HI values(1.14) were inferior in case of 3DCRT plans. IMRT provided better target coverage (V95%) than 3DCRT, the difference ranged from 0.05% for group 1 to 3.84 % for group 4, passing through 0.47% and 1.71 % for group 2 and 3, respectively. Conclusion: Results suggest that the overlap of these OARs can be used as a criteria to select which patient should receive IMRT treatment. IMRT seems a superior technique compared to 3DCRT where there are multiple overlaps between OARs and PTV.
Gupta, M,
A Dosimetric Criterion for Patient Selection: Intensity Modulated Radiation Therapy or Three Dimensional Conformal Radiation Therapy—In High Grade Gliomas. Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL.
http://archive.rsna.org/2014/14042025.html
