Program Information
Estimating the Degree of Iodine Load Reduction with Monoenergetic Images Synthesized From Spectral CT
S Merchant1*, T Merchant1 , Y Yagil2 , D Tsang1 , C Hua1 , (1) St. Jude Children's Research Hospital, Memphis, Tennessee, USA (2) Philips Medical Systems, Haifa, Israel
Presentations
WE-DE-605-12 (Wednesday, August 2, 2017) 10:15 AM - 12:15 PM Room: 605
Purpose: To estimate the potential gain in iodine contrast enhancement and feasibility of iodine load reduction with monoenergetic images synthesized from the detector-based spectral CT.
Methods: A commercial Dual Energy CT phantom (33cm diameter, 5cm thick) with iodine inserts (2, 2.5, 5, 7.5, 10, 15, 20 mg/ml concentration) was scanned using a single-source, double-layer detector spectral CT (Philips iQon) with a CTDIvol of 30mGy under a variety of conditions (80-140kVp with iterative reconstruction of different noise reduction levels, 120-140kVp with 40-200keV monoenergetic reconstruction at a medium level of noise reduction). The contrast-to-noise ratio (CNR) was calculated for each iodine concentration relative to water background with circular ROIs (250mm² area).
Results: Iodine CNRs of 40keV and 50keV images synthesized from 120kVp scans were 3.8 and 2.6 times higher than those from polychromatic 120kVp images with iterative reconstruction (iDose4, level 3) for all iodine concentrations. The same CNR from 120kVp images can be achieved by 40keV and 50keV images with iodine concentrations of 4 and 2.5 times lower, respectively. Although CNRs of polychromatic images increased with lower kVp, they were lower than those of 40keV and 50keV images. Only when images were reconstructed with the model-based iterative algorithm and the highest noise reduction (IMR, level 3) did 80kVp produce comparable CNRs. Image noise at 40keV was 10-30% higher than that at 80keV and above, but was similar to current noise levels of institutional protocols (120kVp, iDose4 , level 3). Although actual gains in iodine contrast enhancement may depend on blood vessel location and size, injection speed, and scan timing, initial patient images indicated 1.7-3.7 times improvement at 50keV, not deviating significantly from 2.6 based on phantom measurements.
Conclusion: Phantom measurements demonstrated that spectral CT has potential to reduce the iodine load in patients receiving contrast scans, justifying prospective clinical studies.
Funding Support, Disclosures, and Conflict of Interest: This study was performed as a part of research agreement between St. Jude Children's Research Hospital and Philips Healthcare.
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