Abstract
Purpose: To systematically evaluate step-and-shoot Intensity-Modulated-Radiation-Therapy (IMRT) plans generated by Direct-Machine-Parameter-Optimization (DMPO) and by Two-Step-Approach (TSA) using identical optimization parameters in Pinnacle 3 treatment planning system. Method and Materials: Using Pinnacle 3 version7.6c, TSA plans of total eight patients with Head-and-Neck, Prostate and Lung cancers were generated using identical optimization parameters from clinical plans used DMPO. The dose of planned-target-volume (PTV) in TSA plan was scaled to closely match at prescribed dose volume in the DMPO plan. Three PTV dosimetric indices: dose-coverage, dose-conformity and dose-inhomogeneity, were generated for each plan. Dosimetric comparisons were performed for organ-at-risk (OAR) with both “maximum-dose-objectives” and “dose-volume-based-objectives”. Final dose recalculation using EGS4-based in-house Monte-Carlo program for each plan was performed and corresponding dosimetric data were obtained. Film-based IMRT QA was performed for three patients. Results: On average, total monitor-units (MUs) are about 25% higher of TSA than DMPO. The averaged segment-numbers and PTV dosimetric indices are almost identical between plans from DMPO and TSA. The maximum-dose (defined at 0.1cc) of Head-and-Neck and Lung OARs with “maximum-dose-objectives” of TSA are, on average, ∼2.5Gy and ∼0.9Gy lower than those of DMPO, respectively. The averaged dose difference in prostate OARs with “maximum-dose-objectives” is small. For OARs with “dose-volume-based-objectives”, there is little difference between TSA and DMPO for all sites. The Monte-Carlo dose recalculations showed similar trends. The agreement between Pinnacle3 calculations and film measurements is 99% for all fields using 3%–3mm criteria. Conclusion: Dosimetric comparisons between DMPO and TSA IMRT plans demonstrated that using identical optimization parameters, DMPO plans have less total MUs and similar averaged segment-number as well as almost identical PTV dosimetric index values as TSA plans. For Head-and-Neck and lung plans, TSA has noticeable better sparing of OARs with “maximum-dose-based-objectives”, which is confirmed by Monte-Carlo recalculations. Film QA demonstrated both TSA and DMPO plans are very accurate.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
