18 March 2008 Temporal modulation transfer function of fluoroscopic systems: small-signal versus large-signal approaches
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Proceedings Volume 6913, Medical Imaging 2008: Physics of Medical Imaging; 691320 (2008); doi: 10.1117/12.770819
Event: Medical Imaging, 2008, San Diego, California, United States
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.
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S. N. Friedman, I. A. Cunningham, "Temporal modulation transfer function of fluoroscopic systems: small-signal versus large-signal approaches", Proc. SPIE 6913, Medical Imaging 2008: Physics of Medical Imaging, 691320 (18 March 2008); doi: 10.1117/12.770819; https://doi.org/10.1117/12.770819
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KEYWORDS
Modulation transfer functions

X-rays

Sensors

Imaging systems

X-ray imaging

Copper

Quantum efficiency

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