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Proceedings Paper

Temporal modulation transfer function of fluoroscopic systems: small-signal versus large-signal approaches
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Paper Abstract

Metrics of system performance are used to assess the abilities and safety of x-ray imaging systems. The detective quantum efficiency (DQE) is used as a measure of "dose efficiency" but, when applied to fluoroscopic systems, requires a measurement of the temporal modulation transfer function (MTF) to account for the effects of system lag. It is shown that the temporal MTF is exposure-rate dependent, and hence must be measured under the specific exposure conditions of interest. We develop a small-signal approach to temporal MTF measurements using a semi-transparent moving slanted edge. Using an x-ray image intensifier-based bench-top system, we show that there is a 50% overstatement of the DQE when not properly accounting for lag. The small-signal approach is used to calculate a lag-free fluoroscopic DQE that agrees with a radiographic DQE measurement under the same exposure-rate conditions. It was found that the temporal MTF did not change within measured precision over normal fluoroscopic conditions, and the radiopaque falling-edge results were consistent with the small-signal temporal MTF. This approach could be implemented in a clinical setting with access to raw (linear or linearized) fluoroscopic image data and could be generalized for use on pulsed-exposure systems.

Paper Details

Date Published: 18 March 2008
PDF: 12 pages
Proc. SPIE 6913, Medical Imaging 2008: Physics of Medical Imaging, 691320 (18 March 2008); doi: 10.1117/12.770819
Show Author Affiliations
S. N. Friedman, Robarts Research Institute (Canada)
The Univ. of Western Ontario (Canada)
I. A. Cunningham, Robarts Research Institute (Canada)
The Univ. of Western Ontario (Canada)
London Health Sciences Ctr. (Canada)


Published in SPIE Proceedings Vol. 6913:
Medical Imaging 2008: Physics of Medical Imaging
Jiang Hsieh; Ehsan Samei, Editor(s)

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