Purpose: Development of an in‐house program facilitates a workflow that allows Electronic Portal Imaging Device (EPID) patient specific quality assurance (QA) measurements to be acquired and analyzed in the Portal Dosimetry Application (Varian Medical Systems, Palo Alto, CA) using a non‐Aria Record and Verify (R&V) system (MOSAIQ, Elekta, Crawley, UK) to deliver beams in standard clinical treatment mode. Methods: Initial calibration of an in‐house software tool includes characterization of EPID dosimetry parameters by importing DICOM images of varying delivered MUs to determine linear mapping factors in order to convert image pixel values to Varian‐defined Calibrated Units (CU). Using this information, the Portal Dose Image Prediction (PDIP) algorithm was commissioned by converting images of various field sizes to output factors using the Eclipse Scripting Application Programming Interface (ESAPI) and converting a delivered configuration fluence to absolute dose units. To verify the algorithm configuration, an integrated image was acquired, exported directly from the R&V client, automatically converted to a compatible, calibrated dosimetric image, and compared to a PDIP calculated image using Varian's Portal Dosimetry Application. Results: For two C‐Series and one TrueBeam Varian linear accelerators, gamma comparisons (global 3% / 3mm) of PDIP algorithm predicted dosimetric images and images converted via the inhouse system demonstrated agreement for ≥99% of all pixels, exceeding vendor‐recommended commissioning guidelines. Conclusion: Combinations of a programmatic image conversion tool and ESAPI allow for an efficient and accurate method of patient IMRT QA incorporating a 3rd party R&V system.

Purpose: To evaluate the equivalence of spine SBRT treatment plans created in Eclipse for the TrueBeam STx (Varian Medical System, Palo Alto, CA) compared to plans using CyberKnife and MultiPlan (Accuray, Sunnyvale, CA). Methods: CT data and contours for 23 spine SBRT patients previously treated using CyberKnife (CK) were exported from MultiPlan treatment planning system into Eclipse where they were planned using static IMRT 6MV coplanar beams. Plans were created according to the original prescription dose and fractionation schedule while limiting spinal dose according to the RTOG 0631 protocol and maintaining target coverage comparable to the original CK plans. Plans were evaluated using new conformity index (nCI), homogeneity index (HI), dose‐volume histogram data, number of MU, and estimated treatment time. To ensure all Eclipse plans were deliverable, standard clinical IMRT QA was performed. The plan results were matched with their complimentary CK plans for paired statistical analysis. Results: Plans generated in Eclipse demonstrated statistically significant (p<0.01) improvements compared to complimentary CK plans in median values of maximum spinal cord dose (17.39 vs. 18.12 Gy), RTOG spinal cord constraint dose (14.50 vs. 16.93 Gy), nCI (1.28 vs. 1.54), HI (1.13 vs. 1.27), MU (3918 vs. 36416), and estimated treatment time (8 vs. 48 min). All Eclipse generated plans passed our clinically used protocols for IMRT QA. Conclusion: CK spine SBRT replanned utilizing Eclipse for LINAC delivery demonstrated dosimetric advantages. We propose improvements in plan quality metrics reviewed in this study may be attributed to dynamic MLCs that facilitate treatment of complicated geometries as well as posterior beams ideal for centrally located and/or posterior targets afforded by gantry‐based RT delivery.

Aim: Microcomputers play an increasingly important role in the delivery of radiation therapy. Exposure to neutron irradiation can produce undesirable effects in modern microcomputers. The objective of this study is to measure acute and cumulative effects of neutron exposure of Intel-based microcomputers in photon and proton therapy treatment environments. Materials and methods: Multiple computers were irradiated with neutrons produced from MEVION S250 passive scattering proton therapy and from Varian 21EX Linear Accelerator photon therapy systems. The energy of the proton beam was 232 MeV and the photon beam energies were 6 and 18 MV. Rates of fatal errors in computer processing unit (CPU) cores were measured. Results: Varying rates of fatal system errors due to upsets in the CPU cores were observed. Post-exposure routine stress testing revealed no permanent hardware defects in the random access memory (RAM) or hard disk drive (HDD) of any tested systems. Microchip manufacturers fit increasingly high numbers of transistors in the same volume and the susceptibility to radiation thus increases. Conclusions: This work explores if the process size of a microchip is the dominant factor and also looked at the short- and long-term effects of neutron irradiation on modern microprocessors in a clinical environment. Additionally, methods of effective shielding are proposed.