Direct conversion flat panel detector for region-of-interest angiography

Minimally invasive image-guided interventions require very high image resolution and quality, specifically over regions-of-interest (ROI) crucial to the procedure. An ROI high quality image allows limited patient radiation deposition while permitting rapid frame transfer rates. Considering current developments in direct conversion Flat Panel Detectors (FPD), advantages of such an imager for ROI angiography were investigated. The performance of an amorphous-selenium based FPD was simulated to evaluate improvements in MTF and DQE under various angiographic imaging conditions. The detector envisioned incorporates the smallest pixel size of 70 μm, reported to date, and a photoconductor thickness of 1000 μm to permit angiography. The MTF of the FPD is calculated to be 60% at the Nyquist frequency of 7.1 lp/mm compared to 6% for a previously reported CsI(Tl)-based ROI CCD camera. The DQE(0) of the FPD at 0.7 mR and 70 kVp is 74% while for the CCD camera is 70%. At 7.1 lp/mm, the FPD's DQE is 26% while for the CCD camera it is 12%. Images of an undeployed stent with 70 μm pixel mammography FPD prototype, compare favorably with images acquired with the CCD camera. Thus a practical direct flat-panel ROI detector with both improved performance and physical size is proposed.