Traditional digital subtraction angiography provides rather limited evaluation of contrast flow dynamics when studying and treating intracranial brain aneurysms. A 1000-frames-per-second photon-counting x-ray detector was used to image detailed iodinecontrast flow patterns in an internal carotid artery aneurysm of a 3D-printed vascular phantom. High-speed imaging revealed differences in vortex and inflow patterns with and without a Pipeline Embolization Device flow diverter in more detail and clarity than could be seen in standard pulsed angiography. Improved temporal imaging has the potential to impact the outcomes of endovascular interventions by allowing clinicians to better understand and act on flow dynamics in real-time.
Purpose:
To compare the visualization of neurointervention procedure and
treatment devices using a 194 µm pixel Flat Panel Detector mode (FPD)
and a 76 µm pixel Complementary Metal Oxide Semiconductor detector
mode (HiDef ) of a new generation x-ray detector system using a blinded
rater study.
Materials and Methods:
Deployment of flow diversion devices for the treatment of internal
carotid artery aneurysms was performed under FPD and HiDef mode image
guidance in a neurointervention phantom simulating patient cranium and
tissue attenuation, embedded with 3D printed intracranial vascular models,
each with an aneurysm in the ICA segment. Image sequence pairs of device
deployments for each detector mode, under similar exposure and FOV
conditions were evaluated by two blinded experienced neurointerventionists
who independently selected their preferred image based on visualization of
anatomical features, image noise and treatment device. They rated their
selection as either similar; better; much better; substantially better than
the other. Inter and Intra rater agreements were calculated and categorized
as poor, moderate and good.
Results:
Both the raters demonstrating good inter and intra rater agreements,
selected HiDef mode images with a frequency of at least 95% each and on an
average rated the HiDef images as much better than FPD images with a
frequency of 73% from a total of 60 image pairs.
Conclusion:
Due to their higher resolution, HiDef mode images are sharper and
visually preferred compared to the FPD images. The improved imaging provided
by the HiDef mode can potentially provide an advantage during
neurointervention procedures.
The prospect of improved low noise, high speed, and dual-energy imaging that may be associated with the use of photon-counting imaging detectors (PCD) has motivated this evaluation of a newly upgraded version of a prototype PCD. The XCounter Actaeon was evaluated in its four acquisition modes each based upon varying signal processing firmware including a mode with charge sharing correction that enables neighboring pixels that share the energy from one incident x-ray photon detection to be counted only once at the proper summed energy in the pixel with the largest charge deposition. Since this PCD is a CdTe-based direct detector with 100 μm pixels, such charge sharing for typical medical x-ray energy photons may occur frequently and must be corrected to achieve more accurate counts. This charge sharing correction is achieved with an Anti-Coincidence Circuit (ACC) which prevents double pixel counting from one event as well as prevents counting from either event if they are below a preset threshold. Various physical parameters of the PCD were evaluated including linearity, sensitivity, pulse pile-up effects, dark noise, spatial resolution, noise power spectrum, and detective quantum efficiency.
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