The effect on patient dose and image quality of simultaneous acquisition of high-resolution small field of view (FOV) and regular-resolution large FOV imaging modes of a dual-resolution imaging detector

A new imaging x-ray detector with 194µm pixel conventional FPD imaging mode for large area visualization with detector field-of-views (FOV) ranging from 12 inch to 6 inch and a 76µm pixel high resolution high-definition (Hi-Def) zoom mode for smaller region-of-interest (ROI) visualization with FOV’s from 3 to 1.5 inches in one detector panel was built to improve visualization of endovascular devices during neurovascular interventions. In this work we investigate the effect of simultaneous use of both imaging modes on entrance kerma area product (KAP) and scatter at the detector. The entrance KAP and the scatter reaching the detector during simultaneous acquisition is the same as the large FOV FPD mode acquisitions, both higher than just Hi-Def mode acquisition. When a 0.7mm thick differential ROI Cu attenuator with a circular 10mm hole was aligned to the Hi-Def detector area, the entrance air kerma is reduced by 70%. To study the effect of scatter on image quality, Hi-Def images of the devices such as guide catheter and stents placed on a head equivalent phantom were acquired with the x-ray field opened to 8inch FOV, with and without the grid. Compared to the 3 inch Hi-Def FOV, with the grid the contrast of the guide catheter tip was reduced by 11% when the FOV was opened to 8 inch; however, without the grid the reduction in contrast was 36%. With the ROI attenuator and no grid the contrast was reduced by 16% when the FOV was opened to 8inch.