Saul N Friedman BSC, Presenter: Nothing to Disclose

Ian Cunningham PhD, Abstract Co-Author: Nothing to Disclose

To calculate the spatiotemporal detective quantum efficiency (DQE) of fluoroscopic systems to gain a comprehensive understanding of system performance.

We introduce a spatiotemporal DQE to describe the performance of fluoroscopic systems in both spatial and temporal frequency domains. It requires measurements of the temporal noise power spectrum (NPS) and the presampling temporal modulation transfer function (MTF) in addition to standard measurements of the average density rate of input x-ray quanta and the output average flat-field dark-subtracted pixel value required for the DQE. Temporal NPS measurements are obtained using a series of open-field fluoroscopic frames and the “synthesis method”. Temporal MTF measurements are obtained using the previously developed “semi-transparent moving slanted-edge method”. Spatiotemporal DQE calculations are made on a bench-top fluoroscopic system and compared to spatial-only DQE measurements obtained by applying a temporal correction factor to account for the frame-averaging effects of system lag.

The spatiotemporal DQE exhibits a fall-off in values along the temporal-frequency direction due to noise aliasing present in the temporal NPS. The spatiotemporal DQE provides a comprehensive metric of both spatial and temporal system performance characteristics. The conventional (spatial) DQE, once corrected for the effects of lag, represents a single “slice” of the spatiotemporal DQE along the temporal zero-frequency axis.

Fluoroscopic systems are fundamentally spatiotemporal and thus require the comprehensive spatiotemporal DQE to describe system performance in both space and time. These measurements will be necessary for the understanding as well as prediction of spatiotemporal tasks and observer performance involved in fluoroscopic procedures.

The spatiotemporal DQE provides a basis for understanding observer performance using fluoroscopic systems in spatiotemporal detection tasks as well as a metric for quality assurance programs.

Friedman, S, Cunningham, I, Measuring the Spatiotemporal Detective Quantum Efficiency of Fluoroscopic Systems.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6008835.html