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WE‐A‐134‐06: Performance Characterization of Kilovoltage Intrafraction Monitoring; a Novel Real‐Time Tumor Localization Modality
Author(s) -
Ng J,
O' Brien R,
Poulsen P,
Fledelius W,
Kuncic Z,
Keall P
Publication year - 2013
Publication title -
medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.473
H-Index - 180
eISSN - 2473-4209
pISSN - 0094-2405
DOI - 10.1118/1.4815512
Subject(s) - medicine , fiducial marker , quality assurance , nuclear medicine , computer science , medical imaging , image guided radiation therapy , radiology , external quality assessment , pathology
Purpose: Kilovoltage Intrafraction Monitoring (KIM) is a novel real‐time tumor localization modality. Previously, KIM was used to determine the prostate trajectories during treatment retrospectively. We have recently further developed KIM for real‐time tumor localization. This study aims to characterize the performance of KIM in a real‐time clinical environment as a necessary condition for a prospective clinical trial. Methods: Intrafraction kilovoltage images acquired during Intensity Modulated Arc Therapy (IMAT) delivery from 9 prostate cancer patients (244 fractions) with implanted fiducial gold markers were used to simulate real‐time acquisition with the real‐time KIM software. The images were passed to the software in an exact replica of the clinical workflow. The software estimates the 3D positions in real‐time from the 2D projection images by maximum likelihood estimation of a 3D probability density function. The root‐mean‐square‐errors (RMSE) between the real‐time and retrospective KIM data from a previous study were computed to evaluate the 3D position determination accuracy. The average processing time per image was computed to determine the real‐time operability. Results: For the 9 patient dataset, the RMSEs between real‐time and retrospective KIM are: 0.98 mm (left‐right), 0.35 mm (superior‐inferior), 0.99 mm (anterior‐posterior) and 1.49 mm (3D). The average processing time per image is 0.24 s. Conclusion: The feasibility and accuracy of real‐time KIM has been demonstrated. With additional quality assurance tests, this work enables a clinical trial of real‐time KIM involving 30 prostate cancer patients, for which ethics approval has been sought. Funding support was received from the Australian National Health and Medical Research Council Australia Fellowship and US National Institutes of Health/National Cancer Institute grant CI R01CA93626. Drs Keall and Poulsen are inventors of the kilovoltage intrafraction motion monitoring method investigated clinically in this study. Stanford University has filed a US patent application (no. 20100172469) and has licensed the method to Varian Medical Systems. No commercial support was received for this study.