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Munck Af Rosenschold P.,Sloan Kettering Cancer Center | Munck Af Rosenschold P.,Radiation Medicine Research Center | Munck Af Rosenschold P.,Copenhagen University | Desai N.B.,Sloan Kettering Cancer Center | And 8 more authors.
Radiotherapy and Oncology | Year: 2014

Purpose To investigate the influence of treatment plan data and image guidance (IG) on positioning uncertainty during prostate cancer (PCa) radiotherapy (RT). Methods Body mass index (BMI), planning target volume (PTV), bladder volume (BV), and rectal cross section area (RCS) were collected for 267 consecutive PCa patients undergoing daily IGRT. Radiographic isocenter corrections to intra-prostatic fiducials for 12,490 treatment fractions were used to derive random (RE) and systematic (SE) inter-fraction uncertainties for the cardinal axes. These data were used to simulate RE and SE for weekly IG and Action Level (AL)-IG treatment protocols. Results SE and RE were 2-5 and 3-4 mm in the cardinal axes, respectively, during simulation of no IG. Without IG, positive correlations (p < 0.01) were noted for (1) anterior-posterior RE vs. RCS and BV and (2) cranio-caudal RE vs. RCS, BV and BMI. The RE increase was 3 mm for the highest quartile of RCS, BV and BMI. Daily IGRT eliminated this relationship. 3D IG corrections of 1 cm or more occured in 27% of treatment fractions and in 97% of patients. Conclusion PCa patients with elevated pre-treatment BV, RCS and BMI have increased inter-fractionation positioning uncertainty and appear the primary candidates for daily IGRT. © 2014 Elsevier Ireland Ltd. All rights reserved.

Fredh A.,Radiation Medicine Research Center | Scherman J.B.,Radiation Medicine Research Center | Fog L.S.,Radiation Medicine Research Center | Munck Af Rosenschold P.,Radiation Medicine Research Center | Munck Af Rosenschold P.,Copenhagen University
Medical Physics | Year: 2013

Purpose: The purpose of the present study was to investigate the ability of commercial patient quality assurance (QA) systems to detect linear accelerator-related errors. Methods: Four measuring systems (Delta 4®, OCTAVIUS®, COMPASS, and Epiqa™) designed for patient specific quality assurance for rotational radiation therapy were compared by measuring four clinical rotational intensity modulated radiation therapy plans as well as plans with introduced intentional errors. The intentional errors included increasing the number of monitor units, widening of the MLC banks, and rotation of the collimator. The measurements were analyzed using the inherent gamma evaluation with 2% and 2 mm criteria and 3% and 3 mm criteria. When applicable, the plans with intentional errors were compared with the original plans both by 3D gamma evaluation and by inspecting the dose volume histograms produced by the systems. Results: There was considerable variation in the type of errors that the various systems detected; the failure rate for the plans with errors varied between 0% and 72%. When using 2% and 2 mm criteria and 95% as a pass rate the Delta4® detected 15 of 20 errors, OCTAVIUS® detected 8 of 20 errors, COMPASS detected 8 of 20 errors, and Epiqa™ detected 20 of 20 errors. It was also found that the calibration and measuring procedure could benefit from improvements for some of the patient QA systems. Conclusions: The various systems can detect various errors and the sensitivity to the introduced errors depends on the plan. There was poor correlation between the gamma evaluation pass rates of the QA procedures and the deviations observed in the dose volume histograms. © 2013 American Association of Physicists in Medicine.

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