Obese patient imaging: Potential dose reduction with photon‐counting CT

Abstract Background Photon‐counting CT (PCCT) offers key advantages over energy integrating detector CT (EID‐CT), especially in low‐dose scans and imaging larger patients. As obesity rates rise, minimizing image noise is critical for diagnostic accuracy. Purpose To evaluate the dose efficiency of cadmium‐zinc‐telluride (CZT) based PCCT compared to EID‐CT across phantom sizes. Methods A patient‐specific 3D‐printed pancreas phantom and a phantom with tissue mimicking inserts were placed in extension rings corresponding to the 50 th , 75 th , 85 th , and 95 th percentile adult waist circumferences. Phantoms were scanned on both PCCT and EID‐CT with CTDI vol ranging from 0.5 to 19.4 mGy. Noise was measured in both phantoms to evaluate dose efficiency. Non‐Poisson noise at low doses (<2 mGy) was quantified using root mean square error from linear fits of the noise‐dose relationship. Potential dose reduction was then assessed by matching noise levels between scanners across phantom sizes. Results PCCT demonstrated reduced noise compared to EID‐CT across all phantom sizes and doses with average noise reductions of 22%, 23%, 25%, and 28% for the 50 th , 75 th , 85 th , and 95 th percentile phantoms, respectively. Noise reduction was greater at lower doses and larger phantom sizes, reaching 88 HU at 1 mGy for the 95 th percentile phantom. Non‐Poisson noise decreased significantly with PCCT compared to EID‐CT for all phantom sizes (p < 0.013). At matched noise levels, PCCT enabled potential dose reductions of 33% and 44% for the 50 th and 95 th percentile phantoms, respectively. Conclusions PCCT exhibited superior dose efficiency compared to EID‐CT across a range of phantom sizes. The enhanced dose efficiency enables both noise reduction and potential dose reduction for the imaging of obese patients and low‐dose imaging applications. Further evaluation with task‐based image quality metrics remains necessary before clinical implementation of dose reduction.