Improving Diagnostic Imaging for Obese Populations: Dose Efficiency of PCCT

Photon-counting CT (PCCT) offers key advantages over energy-integrating detector CT (EID-CT), especially low-dose scans and imaging larger patients. As obesity rates rise, maintaining diagnostic image quality is critical for diagnostic accuracy. This study evaluated the dose efficiency of a PCCT prototype using phantoms representing a range of patient sizes. A 3D-printed anthropomorphic pancreas phantom and inner section of a multi-energy CT phantom were scanned with extension rings representing the 50th, 75th, 85th, and 95thpercentiles of adult waist circumference in the U.S (water equivalent diameters of$32,34,37$, and 39 cm, respectively). Scans were performed on an EID-CT (Aquilion One Insight Edition, Canon Medical Systems Corporation) and a CZT PCCT (Canon Medical Systems Corporation) at a tube voltage of 120 kVp and different dose levels (CTDIvol0.5-19 mGy). Noise was measured on FBP images to compare the noise-dose relationship between scanners. Additional images were acquired for each phantom size to determine dose reduction with PCCT. At matched dose, PCCT demonstrated greater noise reduction as dose decreased and phantom size increased. With the 95thpercentile phantom, noise was$20 \pm 9 \text{HU}$less with PCCT compared to that of EID-CT at 19 mGy. Difference in noise between scanners increased to$64 \pm 23 \text{HU}$at 2 mGy. To match PCCT noise of the 95thpercentile phantom at 15.5 mGy, radiation doses of 7.6,5.4, and 2.7 mGy were required for 85th, 75th, and 50thpercentile phantoms, respectively. Corresponding noise-matched doses in EID-CT were 27.6, 11.8, 7.7, and 4.3 mGy, respectively, highlighting an average dose reduction of 36 % and indicating enhanced dose efficiency. This improvement is particularly impactful at larger phantom sizes and lower dose settings, enabling effective imaging of obese patients without compromising the image quality necessary for precise disease diagnosis and monitoring.