SU-C-209-01: Validation of the Simulated Detectability Metric (G-ROD) Using the Experimental Generalized Measured Relative Object Detectability Metric (GM-ROD)




The Generalized Relative Object Detectability (G-ROD) family of ideal observer metrics are a well-characterized set of task-based metrics used for quantitatively comparing imaging systems that include the detector, focal spot geometry and scatter characteristics on the basis of system abilities in imaging a given simulated object. The G-ROD metric takes the integral over spatial frequencies of the Fourier transform of a simulated object function weighted with the detector generalized DQE (GDQE), divided by the comparable integral for another detector. When a measured image of an actual object is used, the generalized measured-ROD (GM-ROD) metric can compare detector systems without explicitly determining detector MTF. In this work, the results of simulated and measured ROD calculations for the same object are compared for the first time.


G-ROD calculations were performed to compare a high resolution microangiographic fluoroscopic (MAF) detector to a flat panel detector (FPD) using 5mm segments of simulated copper wires of varying diameter (d=0.05–0.6mm) as the object function for three different focal spot sizes at two magnifications. A GM-ROD experiment with similar parameters was performed to compare the same detector system using three actual 5mm copper wires (d=0.113mm,0.238mm,0.558mm) imaged under identical but simulated conditions used in G-ROD calculations to determine the agreement between simulated and experimentally obtained results.


The G-ROD and GM-ROD calculations examined relative detector system imaging performance. The GM-ROD results for all three different sized wires imaged with low magnification and a small focal spot size were 2.1, 1.38, and 1.1, respectively, and the G-ROD results for the same calculation was 1.81, 1.3, and 1.07, corresponding to percent deviations of 13%, 5.8%, and 2.7%.


These results indicate experimental validation of the simulated metric results.

Partial support from NIH grant R01EB002873 and an equipment grant from Toshiba Medical Systems Corp.