Purpose: This work aimed at bringing the energy-discriminating solid-state photon counting detector (PCD) technology to C-arm interventional systems to enable intraoperative PCD-CT imaging with superior low-contrast detectability and material differentiation capability. This abstract reports the hardware development of a rotating-gantry C-arm PCD-CT system and results from preliminary in-vivo porcine studies.
Methods: The prototype system was constructed with minimal modification to an existing interventional system using a custom-made mounting device. A CdTe-based PCD strip (51cm×0.6cm; 100μm pixels) equipped with 2 energy thresholds and state-of-the-art anti-charge sharing technology was installed and can be translated in/out of the beam for switching between flat panel detector (FPD)-based imaging mode and PCD-CT mode. Artifacts due to gantry wobbling was corrected using an in-house geometric calibration phantom; the inter-CdTe panel response nonuniformity was corrected by imaging materials of known radiological pathlengths. Low-contrast detectability, image uniformity, and artifact level were characterized using physical phantoms. To explore the potential benefits of C-arm PCD-CT, four swine were imaged by both PCD-CT and FPD-based CBCT at clinical dose (35 mGy) and reduced-dose (7.1 mGy) levels with 7s gantry rotation time.
Results: Phantom studies demonstrated, at matched collimation (2.5 cm), spatial resolution (8 lp/mm), slice thickness (4.2 mm), and dose level, PCD-CT resolved the 0.3% (3HU) 3mm inserts in Catphan and demonstrated excellent uniformity without any perceivable geometric distortion or ring artifacts. For the in vivo studies, interventional radiologists indicated that porcine abdominal PCD-CT showed a much better delineation of visceral detail and improved soft tissue contrast compared with FPD-CBCT acquired at matched dose levels; the reduced-dose PCD-CT porcine chest images closely matched the quality of the full-dose CBCT images.
Conclusion: A prototype PCD-CT system was developed to generate high-quality and artifact-free images. In-vivo porcine studies demonstrated potential benefits in soft tissue imaging and radiation dose efficiency when compared to FPD-CBCT.