Quantitative Estimation of Integral Doses and Skin Entry Exit Doses during Different Radiation Treatment Delivery Techniques for Craniospinal Irradiation Patients

Abstract

Introduction: The present study includes a qualitative analysis of skin entry exit doses and Integral doses (ID) utilizing various treatment planning strategies. Material and Methods: For this study, we have taken 20 patients suffering from medulloblastoma and planned for Craniospinal irradiation (CSI) with Helical Intensity Modulated radiation therapy HIMRT, Helical three dimensional conformal radiation therapy H3DCRT, and Volumetric modulated arc therapy VMAT treatment planning techniques on Accuray Radixact X9 and Elekta Synergy (Agility) linear accelerator. Results: Various dosimetric parameters like Dmax, Dmean, D80%, D50%, D30%, and D10% have been calculated for skin and skin_ring. Integral doses have been calculated for PTV-Brain and PTV-Spine, taking into consideration at least V95% (target coverage by 95% of the prescribed dose). Statistical analysis was done using SPS software version 22. Mean skin entry and exit doses were [HIMRT=7.07±0.703, H3DCRT = 7.87±0.958 VMAT=4.09±0.706]. For Phase-1mean integral dose for PTV_Brain and PTV_Spine was [HIMRT=11.37±4.458, H3DCRT=12.30±5.00, VMAT=7.21±2.990] and Phase-2 mean integral doses for GTV_Boost was [HIMRT=0.10±0.10 H3DCRT = 0.11±0.117 VMAT=0.03±0.067]. Skin entry exit doses and integral doses were observed to be highest in H3DCRT and then HIMRT. Meanwhile, VMAT plans show minimum entry exit doses and integral doses for Phase 1 and Phase 2. Conclusion: This study concludes that VMAT treatment planning techniques showing less skin entry exit doses and integral doses compared with helical treatment planning techniques. Taking care of these factors can give better clinical outcomes in terms of less late side effects.

Keywords

• volumetric modulated arc therapy helical tomotherapy radiation therapy three
• dimensional conformal radiotherapy