Purpose: To clinically validate RapidArc delivery and planning, a Volume Modulated Arc Radiotherapy, for the Mosaiq Record and Verification (R&V) system (beta status) and prostate planning.
Method and Materials: Five patients undergoing conventional dynamic IMRT were re-planned with RapidArc (8.5) using the AAA 8.2.23 calculation engine and heterogeneity corrections. Efforts were made to match the Dose Volume Histograms (DVH) between the dynamic IMRT plan and the VMAT to the best degree possible (emphasis on the 95% PTV). The plans were delivered using both Mosaiq 1.6 beta and direct ?DICOMRT mode? (Digital Imaging and COmmunication in Medicine in RadioTherapy). ?DICOMRT mode? is a non R&V delivery option with Varian 4DTC consoles which allows the direct loading and delivery of DICOMRT plans. Film analysis and ion chamber readings for both delivery methods were compared and analyzed. MLC and Linac Dynalog files were captured and analyzed using custom MATLAB codes from Washington University, MO. All five plans were delivered five times each via Mosaiq and DICOMRT mode to test reproducibility. Each delivery?s MLC and Clinac Dynalog files were processed to measure delivery accuracy and consistency. Ion chamber readings for each delivery were recorded for reproducibility and each set was benchmarked with dosimetric film analysis with ion chamber verification.
Results: Similar Matched plans between of dynamic IMRT and Rapid Arc techniques could be achieved and delivered after minor modifications to the planning CTs. Mosaiq deliveredRapidArc plans delivered via Mosaiq differed in ion chamber QA readings by an average of -0.53% from DICOMRT mode delivered plans. Repeated delivery standard deviations in dose standard deviation averaged 0.003 in both Mosaiq and DICOMRT delivery mode. Dose-position standard deviations (gantry deg monitoring) were 0.005 and 0.003 (Mosaiq, DICOMRT). Film based QA?s and Dynalog file analysis showed no significant difference between R&V delivery versus DICOMRT mode delivery.
Conclusion: Mosaiq 1.6 provides a stable, accurate delivery platform for RapidArc plans. Comparable prostate plans generated with AAA hetero-corrected algorithms (showing similar DVH coverage to same patient dynamic IMRT plans) can be delivered quickly and accurately.
Conflict of Interest (only if applicable): none
Monroe, J,
Investigating RapidArc Prostate Radiotherapy Delivery with the Mosaiq Record and Verify System. Radiological Society of North America 2009 Scientific Assembly and Annual Meeting, November 29 - December 4, 2009 ,Chicago IL.
http://archive.rsna.org/2009/8502266.html
