Head-to-Head Pilot Comparison of Photon-Counting Versus Conventional CT: Radiologist Confidence and Visual...

To prospectively estimate the ability of photon-counting detector (PCD) CT to improve radiologist confidence for peritoneal disease compared with conventional energy-integrating detector (EID) CT.

Patients with suspected abdominopelvic peritoneal disease underwent clinically indicated EID-CT followed by a same-day research PCD-CT after informed consent. Both scans used IV contrast (up to 200 mL total across both scans). In separate evaluation sessions, 4 radiologists independently reviewed each subject's images once per session, randomly evaluating EID-CT images (1 or 2 mm) or PCD-CT images (120 kV threshold low 1 mm or 50 keV 2 mm). Readers evaluated right versus left supracolic, and inframesocolic spaces, rating confidence in peritoneal malignancy (0 to 100). Overall tumor burden in these regions and on serosal surfaces of the liver, spleen, small bowel, and anterior peritoneal reflection was also graded (0 to 3 scale). In side-by-side comparisons (blinded to CT modality and reconstruction configuration), radiologists ranked preference for each modality/configuration from greatest to least, with ties permitted and with differences ≥ of 2 indicating increased confidence in diagnosis, with separate comparisons for the upper abdomen, mid-abdomen, and pelvis. Linear regression with mixed effects was used to compare confidence and tumor burden scores for each modality/configuration while logistic regression with mixed effects was used for side-by-side comparisons.

Twenty-one patients underwent same-day EID-CT and PCD-CT (mean CTDI vol EID-CT-11.6 versus PCD-CT-11.2 mGy). Despite significantly less iodinated contrast used at PCD-CT (63.8±11.7 versus 136.2±11.7 mL, P <0.0001), confidence scores were similar between modalities. Tumor burden was estimated to be greater for serosal metastases to the liver ( P =0.043) when using 1 mm PCD-CT images. In blinded side-by-side comparisons, the odds of 120 kV 1-mm or 50 keV 2-mm PCD-CT images having a preference rank reflecting increased confidence compared with EID-CT 1 mm in the mid-abdomen was significant [odds ratios (OR): 5.19 and 8.54, respectively, P <0.001] with similar findings in the pelvis (OR for 50 keV PCD-CT: 5.26, P =0.007).

Despite using substantially less IV contrast, radiologist confidence in malignancy was similar at PCD-CT performed after EID-CT. In side-by-side comparisons, PCD-CT images had a significantly increased odds of increasing radiologist confidence compared with EID-CT in the mid-abdomen and pelvis.