Stationary x-ray tomography for hemorrhagic stroke imaging: sampling and resolution properties

Abstract

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).

Multi-source semi-stationary CT for brain imaging: development and assessment of a prototype system and image formation algorithms

“…The detector arc center (𝑂 𝑑 ) is placed at a distance of 285 mm from 𝑂 𝑠 , resulting in a source-to-detector distance, SDD, of 650 mm, defined for the central element in the MXA. This scanner configuration was developed based on prior work on sampling density and completeness with stationary MXA CT [4]. The number of sources is based on the projected size of miniaturized CNT x-ray sources, developed within an industry-academic research collaboration with Micro-X Ltd. (Adelaide, Australia).…”

“…Previous work illustrated the theoretical feasibility of hemorrhagic stroke imaging with a compact scanner design integrating a CNT-based MXA coupled to a large curved-area detector, and implementing stationary and semi-stationary acquisition protocols [4]. The MXA configuration yielded a cone-beam geometry with view-dependent source-detector relative pose, that departs from conventional CBCT systems with circular acquisition trajectories.…”

“…Our previous work showed mitigation of sparse and limited sampling effects in stationary CT for brain imaging via novel posterior sampling strategies within unsupervised learning-based diffusion generative models [5]. Feasibility of accurate estimation of scatter in stationary MXA geometries was demonstrated via adaptive deep scatter estimation methods that effectively combined estimation of scatter in a virtual, invariant, CBCT geometry with adaptive warping and ray-dependent weighting operators [6].…”

Diffusion posterior sampling for nonlinear CT reconstruction

“…In these efforts, the measurement model has been presumed to be linear. Lopez-Montes et al 14 recently applied such an approach to tomographic data.…”

Adaptive kernel-based scatter correction for multi-source stationary CT with non-circular geometry

“…1 Such sources can be arranged into multi-source arrays (MXAs), that when coupled with curved, large-area, x-ray detectors can serve as the basis for ultra-compact, lightweight, stationary tomographic systems in which multiple poses are obtained by virtue of the MXA arrangement, without need for a moving gantry. Previous work showed feasibility of a stationary CT configuration for point of care imaging of hemorrhagic stroke 2 . The stationary configuration (Fig.…”