Purpose: To demonstrate radiation dose reduction for sinus imaging using ultra-high-resolution (UHR) photon-counting-detector computed tomography (PCD-CT) with tin filtration.
Methods: A whole-body PCD-CT system equipped with a 0.4mm tin (Sn) filter was used to demonstrate dose reduction for sinus CT examinations. A head phantom containing a realistic skull was scanned on a commercial CT system (120kV, 13.5 mGy) with an energy-integrating detector (EID), and on the PCD-CT system (UHR mode, Sn-100kV, 10.1 mGy). Two patients referred for clinically-indicated sinus CT were scanned using a commercial EID-CT scanner (120kV, 13.6 mGy). After obtaining informed consent, PCD-CT scans were also performed (UHR mode, Sn-100kV, 7 mGy on one patient, 10mGy on the other patient). EID-CT images were reconstructed using weighted-filtered back projection (WFBP), H70 kernel, 0.75mm thickness, and with iterative reconstruction (SAFIRE), J70 kernel, 0.6mm thickness. PCD-CT images were reconstructed using WFBP, H70 kernel, 0.75mm thickness, and with SAFIRE, PCD-specific sharp kernel V71 kernel, 0.5mm thickness. Image noise (standard deviation of CT numbers) was measured from circular ROIs, and compared between EID-CT and PCD-CT. Potential dose reduction was calculated at matched image noise for a given kernel and image thickness.
Results: Phantom results demonstrated 26% lower noise on PCD-CT with Sn-filter relative to the conventional EID-CT, even with use of a lower dose (PCD: 10.1mGy vs. EID: 13.5mGy). This corresponds to a dose reduction of 70% at matched image noise. Patient images from PCD-CT demonstrated 31% lower noise compared to EID-CT at the lowest PCD-CT dose (PCD: 7mGy vs. EID: 13.6mGy). This corresponds to a dose reduction of 78% at matched image noise. PCD-CT images using a PCD-specific sharp kernel (V71) improved the delineation of sinus structures.
Conclusion: PCD-CT using UHR mode and an additional Sn-filter demonstrated a potential dose reduction of up to 78% and facilitates better delineation of sinus anatomy.
Funding Support, Disclosures, and Conflict of Interest: This research was supported by NIH Grants R01-EB016966 and C06-RR018898. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. The research photon-counting CT system described herein is not commercially available.