Quantitative comparison of Hi-Def and FPD zoom modes in an innovative detector using Relative Object Detectability (ROD) metrics

Neuro-endovascular image-guided interventions (EIGIs) are aided by use of detectors with improved spatial resolution. A new detector is capable of switching between standard resolution, flat-panel detector (FPD) zoom and high-definition (Hi-Def) zoom modes, with 194 and 76 μm pixels respectively. The relative performance of the two zoom modes to image specific, high-resolution objects was quantitatively investigated. Detector DQEs were measured for both zoom modes and used to determine the Relative Object Detectability (ROD), which compares two imaging detectors' relative abilities to image a simulated object by integrating the DQE of one detector with the square of the Fourier transform of the simulated object function and dividing the result by a similar integral for a second reference detector. Initial evaluations used a pre-whitened matched filter (PWMF) ideal-observer model. Comparisons were also made using the generalized-ROD (G-ROD) which uses the generalized-DQE (GDQE) that includes the effects of clinically relevant parameters such as magnification, focal-spot size, and scatter and the generalized-measured-ROD (GM-ROD) which uses the square of the Fourier transform of the actual images of the object acquired with the detectors. Each of the metrics demonstrated improved performance of the Hi-Def zoom mode over the standard FPD mode in imaging a wide array of objects such as stents, wires, and spheres. Of particular note is the greater performance of the Hi-Def when considering the high spatial frequencies necessary for visualizing fine image details of a pipeline stent. These initial investigations demonstrate the great potential of the Hi-Def zoom mode during neuro-interventions.