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

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 ۲۰ patients suffering from medulloblastoma and planned for Craniospinal irradiation (CSI) with Helical Intensity Modulated radiation therapy HIMRT, Helical three dimensional conformal radiation therapy H۳DCRT, and Volumetric modulated arc therapy VMAT treatment planning techniques on Accuray Radixact X۹ and Elekta Synergy (Agility) linear accelerator. Results: Various dosimetric parameters like Dmax, Dmean, D۸۰%, D۵۰%, D۳۰%, and D۱۰% have been calculated for skin and skin_ring. Integral doses have been calculated for PTV-Brain and PTV-Spine, taking into consideration at least V۹۵% (target coverage by ۹۵% of the prescribed dose). Statistical analysis was done using SPS software version ۲۲. Mean skin entry and exit doses were [HIMRT=۷.۰۷±۰.۷۰۳, H۳DCRT = ۷.۸۷±۰.۹۵۸ VMAT=۴.۰۹±۰.۷۰۶]. For Phase-۱mean integral dose for PTV_Brain and PTV_Spine was [HIMRT=۱۱.۳۷±۴.۴۵۸, H۳DCRT=۱۲.۳۰±۵.۰۰, VMAT=۷.۲۱±۲.۹۹۰] and Phase-۲ mean integral doses for GTV_Boost was [HIMRT=۰.۱۰±۰.۱۰   H۳DCRT = ۰.۱۱±۰.۱۱۷ VMAT=۰.۰۳±۰.۰۶۷]. Skin entry exit doses and integral doses were observed to be highest in H۳DCRT and then HIMRT. Meanwhile, VMAT plans show minimum entry exit doses and integral doses for Phase ۱ and Phase ۲. 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