Proceedings Article | 18 October 2022
KEYWORDS: Scanners, CT reconstruction, Brain imaging, Sensors, Modulation transfer functions, Head, Brain, Imaging systems, Tomography, Image quality, X-rays, X-ray sources, Image resolution
Hemorrhagic stroke accounts for up to 20% of all stroke cases, and requires a treatment pathway drastically different to ischemic stroke. Prompt triage is therefore crucial and often only attainable with neuroimaging for intracranial hemorrhage (ICH) evaluation, for which MDCT is the frontline modality. Availability of ICH dedicated imaging in the pre-hospital setting, with portable CT systems, would facilitate early ICH diagnosis. However, current CT or cone-beam CT (CBCT) approaches often use conventional x-ray sources mounted on a rotating gantry limiting their minimum weight and footprint. Recent advances on cold-cathode, compact X-ray sources, based on carbon nanotube (CNT) technology, enable the development of ultra-compact designs based on source-array arrangements on stationary configurations. However, such geometrical arrangements show limited angular sampling, and sparse, non-stationary, volume sampling. In this work we present first investigation of geometric configuration and effects of 3D sampling pertinent to the task of ICH detection on an ultra-portable stationary CBCT for ICH imaging. The baseline configuration included 31 CNT sources on a curved array illuminating a curved panel detector (871 mm length), on a compact geometrical configuration (SDD = 690 mm). Metrics of sampling completeness, sampling density, and MTF shape and band-width integral were explored for configurations varying in source angular span (30°-170°), source array and detector curvature radius (250 mm to flat), use of 2D matrix source arrangements, and multi-acquisition protocols. The results show that sufficient sampling and resolution can be achieved with a combination of moderate curvature (~450 mm radius) of the source array and detectors, with better sampling properties for approximately matched curvature radii (up to 30% BWI improvement). Improved image quality was demonstrated with configurations featuring matrix source arrangements in combination with multi-acquisition protocols (around a 6% of improvement in sampling completeness).
