Evaluation of Dosimetric Parameters for Adolescent Craniospinal Irradiation

Abstract

Background: Craniospinal irradiation (CSI) is an important and challenging radiotherapy technique used for the treatment of Medulloblastoma, one of the most common pediatric cancers. Pediatric patients present with wide variability in weight, height, spine length, brain diameter, body size, intra and inter fractional motion depending on their age as compared to adults. These parameters have significant impact on radiation dose delivery to target and normal structures during radiotherapy of pediatric cancer patients. The present study was aimed to evaluate dosimetric parameters and generate plan quality indices for adolescent CSI. Materials and Methods: A 17 years old male adolescent patient with Medulloblastoma was recruited in the present sturdy. The patient was planned with RapidArc TM / Volumetric Modulated Arc Therapy (VMAT) mode using 6 MV X-Ray photon beam from Varian Trilogy with FFF machine. The dose points such as max, mean, 2%, 98%, 95%, 105% and 107% were collected using dose statistics and dose volume histogram (DVH) and analyzed for calculation of various dosimetric parameters. The in-vivo dosimetry was performed and radiation doses to eyes were assessed using CaSO4:Dy TLD powder. Results: The plans were approved with a gamma passing rate (3%, 3mm) of more than 95%. The dose homogeneity index and conformity index were observed 0.074 and 1.10 respectively. The average doses to eyes were observed approximately 35% of the tumor dose during RapidArc TM-CSI. The results of the present study demonstrated that V5 was observed high the normal structures except kidneys. Esophagus and thyroid were receiving significant low dose spillage at a cost of high homogeneity and conformity of dose to PTV which were needed to enhance tumor control probability (TCP) of Medulloblastoma. Conclusion: The present study developed a benchmark guide for adolescent RapidArc TM-CSI.