Region of interest micro-angiography: Radiographic imaging optimized for vascular interventions

By changing the design paradigm for radiographic detectors to optimize imaging of a region of interest (ROI) for endovascular interventions, a new class of micro-angiographic detectors is proposed. Such ROI imagers optimized for high spatial resolution over a fraction of the conventional FOV accept compromises in x-ray absorption so that the desired high frequency DQE is achieved. A prototype demonstration system based upon a CsI(Tl) phosphor coupled by a fiber taper to a CCD is compared with an image-intensifier-based digital angiographic (DA) system for imaging typical neuro-vascular pathologies (stenoses, aneurysms, arterio-venous malformations (AVMs)) and a variety of stents with wire diameter down to 50 μm. Although the zero frequency DQE of the DA unit exceeded that of the prototype with its thin phosphor layer, the prototype excelled in the desired frequency range of 3-10 lp/mm. Using an artery block phantom, the smallest 1 mm diameter stenoses and aneurysms were clearly visualized only with the prototype. For imaging stents, details of wires and struts were only visible with the prototype. ROI images of an AVM pig rete model showed more detailed angio-architecture compared to blurred-appearing DA images. It is expected that future such ROI cameras should allow improved clinical interventions.