DVH Analysis of Cobalt-60 treatment plans incorporating a recently developed MLC

Purpose: The aim of this investigation was to measure the gain in DVH indices when the recently developed MLC was used for Cobalt-60 treatments.Methods: A prototype multileaf collimator (MLC) that was retrofitted to telecobalt-60 therapy machine was reported and is currently proposed for clinical trials in our institution. Ten patients’ plans that were previously planned through an ECLIPSE® treatment planning system and were treated with open beams from Cobalt-60 machine were imported into Radiation Oncology Planning System [ROPS] and the dose calculations and dose volume histogram (DVH) analysis were performed. The plans were re-planned using the Cobalt-MLC, a feature available in the ROPS planning system. The DVH analysis consisted of conformity index (CI), homogeneity index (HI) and conformation number (CN). The results of this study are presented in this paper. The analysis specifically aimed at measuring the gain in these indices when the MLC was compared with open beams.Results: DVH Comparison of ten sites using open and Cobalt MLC fields showed that the use of MLC results in reduced normal tissue dose, while maintaining the GTV dose. Lower value of CI for normal structures was observed demonstrating the sparing of critical organs when MLC was used. The index HI was studied to show the significance of hot spots outside the PTV. Hot spots were observed even with MLC beams for some cases due to less number of fields.Conclusion: It has been demonstrated through DVH analysis that the use of the recently developed MLC for Cobalt Teletherapy machine results in benefit for the treatment of patients

Evaluation of Eclipse 3D plans using an independent treatment planning system

Purpose: The goal of the current investigation was to compare complex 3D conformal plans generated on Eclipse™ treatment planning system (TPS) with independent dose calculations from radiation oncology planning system (ROPS™) TPS used as a secondary quality assurance check.Methods: Fifteen cancer patients that were treated with complex conformal treatment plans with cobalt and linac beams, using Eclipse TPS, were selected for this study. The structure sets, treatment beam data and prescription information were exported from the Eclipse TPS using DICOM-RT export. Using custom software, these data were imported into ROPS TPS. Independent dose calculation on the ROPS planning system using Clarkson summation algorithm was done. The dose volume histograms (DVH) from both planning systems were extracted and analyzed using custom software. Dose assessment was accomplished by defining criteria based on gross tumor volume (GTV) dose coverage, dose homogeneity and mean dose. For organs at risk (OAR) other than GTV, the main dose parameters were, mean dose and percentage of volume receiving 95% of prescription dose.Results: For the GTV, all 15 cases met the criteria set for the mean dose and dose homogeneity index. However, breast cases were found to have deviation in the percentage volume receiving the 95% of prescription dose.Conclusion: Using the criteria set for plan acceptance, all the 15 clinical cases were evaluated. Except for breast tangent plans, all plans passed all the criteria set. The large deviation for breast tangent plans was attributed to differences in dose calculation algorithms

DVH Analysis of Cobalt-60 treatment plans incorporating a recently developed MLC

Purpose: The aim of this investigation was to measure the gain in DVH indices when the recently developed MLC was used for Cobalt-60 treatments.Methods: A prototype multileaf collimator (MLC) that was retrofitted to telecobalt-60 therapy machine was reported and is currently proposed for clinical trials in our institution. Ten patients’ plans that were previously planned through an ECLIPSE® treatment planning system and were treated with open beams from Cobalt-60 machine were imported into Radiation Oncology Planning System [ROPS] and the dose calculations and dose volume histogram (DVH) analysis were performed. The plans were re-planned using the Cobalt-MLC, a feature available in the ROPS planning system. The DVH analysis consisted of conformity index (CI), homogeneity index (HI) and conformation number (CN). The results of this study are presented in this paper. The analysis specifically aimed at measuring the gain in these indices when the MLC was compared with open beams.Results: DVH Comparison of ten sites using open and Cobalt MLC fields showed that the use of MLC results in reduced normal tissue dose, while maintaining the GTV dose. Lower value of CI for normal structures was observed demonstrating the sparing of critical organs when MLC was used. The index HI was studied to show the significance of hot spots outside the PTV. Hot spots were observed even with MLC beams for some cases due to less number of fields.Conclusion: It has been demonstrated through DVH analysis that the use of the recently developed MLC for Cobalt Teletherapy machine results in benefit for the treatment of patients.</p