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Proceedings Paper

The effect of dose reductions on lesion detection in head CT
Author(s): Saeed Elojeimy; Walter Huda; Kent M. Ogden; Ryan Owen; Ehsan Samei; Zoran Rumboldt
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Paper Abstract

The purpose of this study was to quantitatively evaluate the effect of reducing radiation dose (i.e., mAs) on lesion detection in head CT examinations. We used a simulation package (Syngo Explorer) to reconstruct 5-mm thick CT images of the brain of one patient pertaining to the centrum semiovale, the basal ganglia, and the sella turcica. Lesion detection was measured using two Alternate Forced Choice (2-AFC) experiments that measure the lesion contrast (I92%) corresponding to a detection accuracy of 92%. Two observers performed experiments to investigate detection of low contrast lesions with four sizes ranging from 3 mm to 10 mm and at four x-ray beam intensities ranging from 105 mAs to 300 mAs. Results were plotted as log[I92%] versus log[mAs], and the slopes were measured for each lesion size. Lowering the mAs always reduced lesion detection performance in all images, and for all lesion sizes. Average slopes of the I92% versus mAs curves were -0.23 for 3 mm lesions, -0.16 for 4.5 mm lesions, and ~-0.11 for the 7 and 10 mm lesions. For the smallest lesions investigated (3 mm), doubling the x-ray intensity improved lesion detection performance by ~ 15%, whereas for the largest sized lesions (7 and 10 mm), doubling the tube current improved lesion detection performance by ~ 7%. The observed improvements in detection performance are markedly lower than predicted by the Rose model where a doubling of the tube current would be expected to improve detection performance by 29% at all lesion sizes.

Paper Details

Date Published: 14 March 2009
PDF: 10 pages
Proc. SPIE 7258, Medical Imaging 2009: Physics of Medical Imaging, 72584Q (14 March 2009); doi: 10.1117/12.812051
Show Author Affiliations
Saeed Elojeimy, Medical Univ. of South Carolina (United States)
Walter Huda, Medical Univ. of South Carolina (United States)
Kent M. Ogden, SUNY Upstate Medical Univ. (United States)
Ryan Owen, Medical Univ. of South Carolina (United States)
Ehsan Samei, Duke Univ. Medical Ctr. (United States)
Zoran Rumboldt, Medical Univ. of South Carolina (United States)


Published in SPIE Proceedings Vol. 7258:
Medical Imaging 2009: Physics of Medical Imaging
Ehsan Samei; Jiang Hsieh, Editor(s)

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