Artificial intelligence iterative imaging reconstruction with low-dose CT scans for hepatic metastases

Contrast-enhanced CT is commonly used in the evaluation of hepatic metastatic lesions. This prospective study aimed to assess the capability of artificial intelligence iterative reconstruction (AIIR) in low-dose CT for detection of hepatic metastases. Thirty-two patients with hepatic metastases were enrolled and underwent dual-phase CT scans in the venous phase. Each patient received a standard-dose (SD) scan (120 kVp, 180 mAs) followed by a reduced-dose (RD) scan (120 kVp, 30 mAs). All data were analyzed. Compared with the SD CT scan, the volume CT dose index (CTDI_vol), dose length product (DLP), and effective dose (ED) were significantly lower in the RD CT, with an average radiation reduction of approximately 80%. Radiation dose reduction significantly increased the image noise and degraded the overall image quality. However, higher reconstruction levels resulted in an increasingly prominent "waxy" texture on CT images. There were significant (P < 0.05) differences in liver noise, subcutaneous fat noise, liver parenchymal SNR, portal vein SNR, liver parenchymal contrast-to-noise ratio (CNR), and portal vein CNR among the groups, with the ranking of noise, SNR and CNR: RD AIIR Group 1 < RD AIIR Group 3 < RD AIIR Group 5 < SD Karl group < RD Karl group. In the SD Karl group, 218 metastatic nodules were identified in 32 patients, whereas in the RD Karl group, 176 (80.7%) nodules were detected. However, the RD AIIR 3 group identified 204 (93.6%) nodules. As the metastatic nodules size decreased, the detection rate in the RD Karl significantly declined, with the detection rate 14.29% in the RD Karl for nodules < 5 mm. In RD AIIR 3, the detection rate reached 100% for lesions ≥ 10 mm and 57.14% for lesions < 5 mm, which was significantly higher than in the RD Karl group (P < 0.05). The CNR of intrahepatic nodules in the SD Karl, RD Karl, and RD AIIR 3 was 2.68 (2.17, 3.80), 2.18 (1.64, 2.79), and 6.34 (4.34, 8.36), respectively, with significant differences among them. The signal-to-noise ratio of the lesions in the RD AIIR 3 group was the highest. AIIR-assisted low-dose CT reconstruction yields image quality comparable to standard-dose CT, while preserving diagnostic performance for the detection of small hepatic metastases.