Intrinsic and total system performance evaluation for a newly developed solid state X-ray image intensifier (SSXII) detector

The new Solid State X-ray Image Intensifier (SSXII) is a high-resolution, high-sensitivity, real-time region-ofinterest (ROI) x-ray imaging detector. Evaluations were made of both standard linear systems metrics (MTF, DQE) and total system performance with generalized linear systems metrics (GMTF, GDQE) including scatter and geometric un-sharpness for simulated clinical conditions. The SSXII is based on a 1k x 1k EMCCD sensor coupled to a 300 μm thick CsI(Tl) phosphor through a 2.88:1 fiber optic taper resulting in a 37 μm effective pixel size and an effective 3.7 cm x 3.7 cm square field-of-view (FOV). Standard methods were used to calculate MTF, NNPS and DQE. Generalized metrics were calculated and compared for three different magnifications (1.03, 1.11 and 1.2) and three different focal spots (0.3 mm, 0.5 mm and 0.8 mm) for a scatter fraction of 0.28. For an RQA5 spectrum, at 5 cycles/mm the MTF was found to be 0.06 and DQE was 0.04, while the DQE(0) was 0.60. Focal spot un-sharpness and scatter significantly degrades the GMTF and GDQE performance of the detector. A low frequency drop is caused by scatter and is almost independent of focal spot size and magnification. The degradation for middle range frequencies is caused by geometric un-sharpness and increases with focal spot size and magnification. This degradation was least in the case of the small focal spot and almost independent of magnification. In spite of this degradation, the high resolution SSXII with a small FOV may have a significant impact on ROI image-guided neuro-interventions since it demonstrates far better performance than standard current detectors.