22 March 2016 Over-exposure correction in knee cone-beam CT imaging with automatic exposure control using a partial low dose scan
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Abstract
C-arm-based cone-beam CT (CBCT) systems with flat-panel detectors are suitable for diagnostic knee imaging due to their potentially flexible selection of CT trajectories and wide volumetric beam coverage. In knee CT imaging, over-exposure artifacts can occur because of limitations in the dynamic range of the flat panel detectors present on most CBCT systems. We developed a straightforward but effective method for correction and detection of over-exposure for an Automatic Exposure Control (AEC)-enabled standard knee scan incorporating a prior low dose scan. The radiation dose associated with the low dose scan was negligible (0.0042mSv, 2.8% increase) which was enabled by partially sampling the projection images considering the geometry of the knees and lowering the dose further to be able to just see the skin-air interface. We combined the line integrals from the AEC and low dose scans after detecting over-exposed regions by comparing the line profiles of the two scans detector row-wise. The combined line integrals were reconstructed into a volumetric image using filtered back projection. We evaluated our method using in vivo human subject knee data. The proposed method effectively corrected and detected over-exposure, and thus recovered the visibility of exterior tissues (e.g., the shape and density of the patella, and the patellar tendon), incorporating a prior low dose scan with a negligible increase in radiation exposure.
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Jang-Hwan Choi, Jang-Hwan Choi, Kerstin Muller, Kerstin Muller, Scott Hsieh, Scott Hsieh, Andreas Maier, Andreas Maier, Garry Gold, Garry Gold, Marc Levenston, Marc Levenston, Rebecca Fahrig, Rebecca Fahrig, } "Over-exposure correction in knee cone-beam CT imaging with automatic exposure control using a partial low dose scan", Proc. SPIE 9783, Medical Imaging 2016: Physics of Medical Imaging, 97830L (22 March 2016); doi: 10.1117/12.2217347; https://doi.org/10.1117/12.2217347
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