Premium
SU‐EE‐A3‐06: Dose Reduction in CBCT Via Intensity Weighted Region of Interest Imaging
Author(s) -
Pearson E,
Cho S,
Pan X,
Pelizzari C
Publication year - 2008
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 - 10.1118/1.2961391
Subject(s) - image quality , optics , region of interest , materials science , intensity (physics) , noise reduction , cone beam computed tomography , reduction (mathematics) , nuclear medicine , signal to noise ratio (imaging) , filter (signal processing) , physics , computer science , artificial intelligence , mathematics , computer vision , medicine , image (mathematics) , computed tomography , radiology , geometry
Purpose: Reporting preliminary evaluation results of an intensity weighted region of interest (IWROI) imaging technique that utilizes recent developments in cone‐beam CT (CBCT) reconstruction theory to reduce patient exposure and detected scattered radiation. Method and Materials: Patient dose can be reduced by decreasing the x‐ray source fluence, however this comes with the cost of a decreased signal‐to‐noise‐ratio in the resulting images. IWROI imaging introduces filters into the x‐ray beam such that the central ROI receives the full beam intensity, and thus maintains SNR level while the periphery of the field‐of‐view (FOV) is illuminated by a reduced intensity, filtered beam. Reconstruction is done with the recently developed chord‐based BPF algorithm, which has been shown to be robust against some forms of truncation and to have favorable noise propagation properties. This algorithm enables IWROI to be used more flexibly and yields higher image quality. Experimental studies were carried out by constructing aluminum and copper filters which could be attached directly to the CBCT source. Scans were taken with 125 kVp, 80 mA and 15 ms pulse length exposure setting. Dose measurements were made using LiF TLDs 10cm deep in a 20cm stack of 30cm×30cm solid water slabs. Results: For the 3mm copper filter case the measurements showed a 7% dose reduction for the central ROI and a 37% reduction for the low intensity region of the image. The coefficient of variation for the full intensity ROI after BPF reconstruction was 0.053 and 0.100 in the filtered region indicating relative noise levels. Conclusion: IWROI imaging can reduce radiation exposure to sensitive regions of the anatomy while still producing high image quality in the region of interest. The filtered region also contains enough information for comparison of the gross anatomy with the planning scan. Conflict of Interest: Work supported by Varian Medical Systems, Inc.