Author: Meghan Lubner, Aria M. Salyapongse, Teva Shapiro, Scott D. Slavic, Timothy P. Szczykutowicz, Giuseppe Toia, Zhye Yin 👨🔬
Affiliation: GE HealthCare, Departments of Radiology and Medical Physics, University Wisconsin-Madison, GE Healthcare, University of Wisconsin-Madison, University of Wisconsin - Madison, UW-Madison, University of Wisconsin Madison, Department of Radiology 🌍
Purpose:
To compare iodine quantification on a prototype deep silicon photon-counting detector (PCD) CT and conventional clinical energy-integrating (EID) dual-energy (DE) CT.
Methods:
A phantom (Gammex MECT) with known iodine quantities [0-20 mg/mL] was scanned on a prototype PCD CT scanner with 120 kV, 600 mA, 0.42 mm slice thickness, 0.8 s rotation time, and 40 mm collimation axial scanning. The phantom was also scanned on a commercially available EID DE CT system which used fast 80/140 kV switching, 600 mA, 5 mm slices, 0.8 s rotation time, 0.981:1 pitch, and 40 mm collimation helical scanning. Iodine (water) images were made with a prototype material decomposition algorithm for PCD images, and with commercially available material decomposition software for EID images. Regions of interest were placed over the iodine rods for both PCD and EID images. A correction based on the iodine quantification in the 0 mg/mL rod and the relative rod densities was applied to the iodine quantification. Iodine percent error was determined by taking the difference between quantified and known iodine, dividing by known iodine, and multiplying by 100.
Results:
Iodine quantification was within 0.15 mg/mL for 0-20 mg/mL on the prototype PCD CT. This translates to iodine percent errors between 0.4-4.3%. On EID CT, iodine quantification was within 0.2 mg/mL for 0-20 mg/mL, with iodine percent errors between 1.1-76%. PCD CT was more accurate for 0 mg/mL iodine, with 0.1 mg/mL error compared to the EID error of 0.2 mg/mL.
Conclusion:
Iodine quantification on the prototype deep silicon PCD CT was within 4% 0-20 mg/mL iodine densities, which is similar or better than the performance of the clinical EID CT scanner and previous work on this system. The observed systematic error will likely improve with further material calibration improvements.