Initial investigations of scatter cross-talk in simultaneous biplane high-speed 1000 frames per second neuro-angiography using Monte Carlo simulations.

The Aries photon counting detector (PCD) by Direct Conversion Inc. can image up to 1000 frames per second and is used to track contrast bolus in neuro-vasculature for hemodynamic calculations. For 3D tracking, synchronized biplane imaging with 1 ms acquisition times is used such that both imaging planes are exposed simultaneously. This leads to cross-scattered radiation being detected and a degradation of image quality compared to single-plane imaging. In this study, we utilize Monte Carlo (MC) methods to quantify the increase in scatter due to cross-talk without the use of a radiographic grid. EGSnrc biplane simulations were performed with the Zubal anthropomorphic head phantom. The total scatter plus primary and cross-scatter was calculated in the imaging planes for two orthogonal AP and lateral beams with a field size consistent with the 7.5×5 cm Aries detector, while the primary was determined with a 1×1 mm beam. The forward scatter was then determined from the difference between total and primary. The scatter is seen to increase by 4%-56% for AP projections and 48%-71% for lateral projections depending on detector orientation during simultaneous exposure. Scatter degradation from cross-talk can be reduced using an anti-scatter grid as well as the energy thresholding capabilities of the Aries PCD.