Introduction: the study was designed to dosimetrically compare the treatment planning optimization techniques to analyze the equivalence of co-60 and ir-192 HDr Brachytherapy sources. further, the present study planned to analyze the equivalence on the basis of technical, logistical and clinical aspects for both the sources.Methods: Thirty-two patients with confirmed diagnosis of carcinoma cervix were included in the study. Comparative treatment plans were made for three different treatment planning optimization techniques for both the sources Co-60 and ir-192 i.e. (a) plans with prescription on point a (Manchester system) with identical dwell position, (b) plans with inverse planning and (c) plans with prescription on Hr-ctV with manual optimization. treatment plans were evaluated on the basis of clinical parameters Hr-ctV V200%, V150%, V100%, D95%, D50%, D2cc Bladder, D2cc rectum and point dose on icrU rectum and Bladder reference point.Results: For the plans with prescription on Point A with identical dwell position, the average percentage difference were found Hr-ctV V200% (6.3%), V150% (5.1%), V100% (1.8%), D2cc rectum (2.3%) and icrU rectum reference point (2.1%) and all these parameters were statistically significant for both the sources. For the Plans with inverse planning optimization, these parameters were found significant with average percentage difference HR-CTV V200% (6.1%), V150% (4.9%), D50% (2.1%) and icrU rectum reference point (2.3%). for the plans with dose prescription on Hr-ctV and manual optimization, most of the average percentage differences were found non-significant and clinical parameters were observed clinically comparable to each other for both the sources. further, it was also observed that on an average ir-192 source required only 42% of the treatment time required by co-60 for the same treatment plan delivery.Conclusion: among all the three planning techniques, the planning technique with prescription on Hr-ctV & manual optimization was found to have comparable clinical quality for both the sources. this analysis revealed that geometry of source placement can overcome the differences in individual source characteristics.
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.
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