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19 March 2007 How do kV and mAs affect CT lesion detection performance?
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Abstract
The purpose of this study was to investigate how output (mAs) and x-ray tube voltage (kV) affect lesion detection in CT imaging. An adult Rando phantom was scanned on a GE LightSpeed CT scanner at x-ray tube voltages from 80 to 140 kV, and outputs from 90 to 360 mAs. Axial images of the abdomen were reconstructed and viewed on a high quality monitor at a soft tissue display setting. We measured detection of 2.5 to 12.5 mm sized lesions using a 2 Alternate Forced Choice (2-AFC) experimental paradigm that determined lesion contrast (I) corresponding to a 92% accuracy (I92%) of lesion detection. Plots of log(I92%) versus log(lesion size) were all approximately linear. The slope of the contrast detail curve was ~ -1.0 at 90 mAs, close to the value predicted by the Rose model, but monotonically decreased with increasing mAs to a value of ~ -0.7 at 360 mAs. Increasing the x-ray tube output by a factor of four improved lesion detection by a factor of 1.9 for the smallest lesion (2.5 mm), close to the value predicted by the Rose model, but only by a factor of 1.2 for largest lesion (12.5 mm). Increasing the kV monotonically decreased the contrast detail slopes from -1.02 at 80 kV to -0.71 at 140 kV. Increasing the x-ray tube voltage from 80 to 140 kV improved lesion detection by a factor of 2.8 for the smallest lesion (2.5 mm), but only by a factor of 1.7 for largest lesion (12.5 mm). We conclude that: (i) quantum mottle is an important factor for low contrast lesion detection in images of anthropomorphic phantoms; (ii) x-ray tube voltage has a much greater influence on lesion detection performance than x-ray tube output; (iii) the Rose model only predicts CT lesion detection performance at low x-ray tube outputs (90 mAs) and for small lesions (2.5 mm).
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
W. Huda, K. M. Ogden, K. Shah, C. Jadoo, E. M. Scalzetti, R. L. Lavallee, and M. L. Roskopf "How do kV and mAs affect CT lesion detection performance?", Proc. SPIE 6510, Medical Imaging 2007: Physics of Medical Imaging, 65104P (19 March 2007); https://doi.org/10.1117/12.708498
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