PURPOSE: To investigate the use of a commercially available video-based EPID for in vivo dosimetry during treatment of prostate cancer patients. METHODS: For 10 prostate cancer patients, the inter-fraction variation within measured portal dose images (PDIs) was assessed and measured PDIs were compared with corresponding predicted PDIs based on the planning CT scan of the patient. RESULTS: For the lateral fields, the average standard deviation in the measured on-axis portal doses during the course of a treatment was 0.9%; for the anterior fields this standard deviation was 2.2%. The difference between the average on-axis measured portal dose and the predicted portal dose was 0.3+/-2.1% (1 SD) for the lateral fields and 0.7+/-3.4% (1 SD) for the anterior fields. Off-axis differences between measured and predicted portal doses were regularly much larger (up to 15%) and were caused by frequently occurring gas pockets inside the rectum of the patients during treatment or during acquisition of the planning CT scan. The detected gas pockets did sometimes extend into the gross tumour volume (GTV) area as outlined in the planning CT scans, implying a shift of the anterior rectum wall and prostate in the anterior direction (internal organ motion). CONCLUSIONS: The developed procedures for measurement and prediction of PDIs allow accurate dosimetric quality control of the treatment of prostate cancer patients. Comparing measured PDIs with predicted PDIs can reveal internal organ motion.
RCT Entities:
PURPOSE: To investigate the use of a commercially available video-based EPID for in vivo dosimetry during treatment of prostate cancerpatients. METHODS: For 10 prostate cancerpatients, the inter-fraction variation within measured portal dose images (PDIs) was assessed and measured PDIs were compared with corresponding predicted PDIs based on the planning CT scan of the patient. RESULTS: For the lateral fields, the average standard deviation in the measured on-axis portal doses during the course of a treatment was 0.9%; for the anterior fields this standard deviation was 2.2%. The difference between the average on-axis measured portal dose and the predicted portal dose was 0.3+/-2.1% (1 SD) for the lateral fields and 0.7+/-3.4% (1 SD) for the anterior fields. Off-axis differences between measured and predicted portal doses were regularly much larger (up to 15%) and were caused by frequently occurring gas pockets inside the rectum of the patients during treatment or during acquisition of the planning CT scan. The detected gas pockets did sometimes extend into the gross tumour volume (GTV) area as outlined in the planning CT scans, implying a shift of the anterior rectum wall and prostate in the anterior direction (internal organ motion). CONCLUSIONS: The developed procedures for measurement and prediction of PDIs allow accurate dosimetric quality control of the treatment of prostate cancerpatients. Comparing measured PDIs with predicted PDIs can reveal internal organ motion.
Authors: Angelo Piermattei; Andrea Fidanzio; Luigi Azario; Francesca Greco; Alessandra Mameli; Savino Cilla; Luca Grimaldi; Guido D'Onofrio; Boris Giuseppe Augelli; Gerardina Stimato; Diego Gaudino; Sara Ramella; Rolando D'Angelillo; Francesco Cellini; Lucio Trodella Journal: Med Biol Eng Comput Date: 2009-02-17 Impact factor: 2.602
Authors: Indra J Das; Minsong Cao; Chee-Wai Cheng; Vladimir Misic; Klaus Scheuring; Edmund Schüle; Peter A S Johnstone Journal: J Appl Clin Med Phys Date: 2011-02-02 Impact factor: 2.102