Prone Photon-counting Computed Tomography With Iodine Mapping for Differentiating Breast Masses

OBJECTIVES: Photon-counting CT (PC-CT) offers higher spatial resolution and enables iodine quantification compared with conventional CT. Its potential role in breast imaging is currently under evaluation. PURPOSE: To assess whether prone-positioned PC-CT with iodine mapping can differentiate malignant from benign breast masses, and to evaluate the clinical utility of iodine mapping (PC-CTIodine), monoenergetic postcontrast images (PC-CTC+), and virtual noncontrast reconstructions (PC-CTVNC) for lesion conspicuity, image quality, anatomic correlation with MRI, and reader's preference. MATERIALS AND METHODS: This prospective single-center study (December 2021 to August 2023) included patients with biopsy-proven breast cancer who underwent thoracoabdominal PC-CT in prone, compression-free breast positioning, breast MRI, and tomosynthesis during staging. Reconstructions included PC-CTIodine, PC-CTC+ with 65 kiloelectronvolts (keV), and PC-CTVNC. Quantitative analysis included iodine concentrations and contrast-to-noise ratio (CNR), each with additional subtype analysis; qualitative ratings included lesion conspicuity, noise, artifacts, lesion localization, and reader preferences. Statistical analysis included Kruskal-Wallis, Friedman and Wilcoxon signed-rank tests, and Cohen kappa. RESULTS: Among 90 potentially eligible participants, 78 participants (mean age, 55 y ± 15 SD, 77 women) with 134 breast masses (106 malignant, 28 benign) were included. Benign masses differed from malignant lesions (P < 0.001). Breast cancers showed the highest median iodine concentration [2.6 mg/mL (IQR, 2.0 to 3.3)], significantly higher than DCIS (1.7 mg/mL), fibroadenomas (0.5 mg/mL), and cysts (-0.1 mg/mL; all P < 0.05). Iodine values for papillomas and lymph nodes overlapped with cancers (P > 0.05). CNR was higher for PC-CTC+ than PC-CTIodine (P < 0.001). Readers preferred PC-CTIodine for detection and PC-CTC+ for morphologic assessment. Lesion localization matched MRI, and no relevant artifacts were observed. CONCLUSION: Prone PC-CT with iodine mapping enables accurate lesion localization, quantification, and differentiation between malignant and benign breast masses. Compression-free breast positioning enhances localization accuracy. The method may serve as an accessible adjunct to MRI in staging, with complementary use of iodine and postcontrast reconstructions recommended for optimal assessment.