Relative object detectability (ROD) quantifies the relative performance of two image detectors for a specified object of
interest by taking the following ratio: the integral of detective quantum efficiency of a detector weighted by the
frequency spectrum of the object divided by that for a second detector. Four different detectors, namely the microangiographic
fluoroscope (MAF), the Dexela Model 1207 (Dex) and Hamamatsu Model C10901D-40 (Ham) CMOS xray
detectors, and a flat-panel detector (FPD) were compared. The ROD was calculated for six pairs of detectors: (1)
Dex/FPD, (2) MAF/FPD, (3) Ham/FPD, (4) Dex/Ham, (5) MAF/Ham and (6) MAF/Dex for wires of 5 mm fixed
length, solid spheres ranging in diameter from 50 to 600 microns, and four simulated iodine-filled blood vessels of outer
diameters 0.4 and 0.5 mm, each with wall thicknesses of 0.1 and 0.15 mm.
Marked variation of ROD for the wires and spheres is demonstrated as a function of object size for the various detector
pairs. The ROD of all other detectors relative to the FPD was much greater than one for small features and approached
1.0 as the diameter increased. The relative detectability of simulated small iodine-filled blood vessels for all detector
pairs was seen to be independent of the vessel wall thickness for the same inner diameter. In this study, the ROD is
shown to have the potential to be a useful figure of merit to evaluate the relative performance of two detectors for a
given imaging task.