Photon-counting CT yields superior abdominopelvic image quality at lower radiation and iodinated contrast doses.

Abstract

Background: Photon-counting detector (PCD) computed tomography (CT) has been shown to provide better image quality at lower radiation and intravenous contrast doses than energy-integrating detector (EID) CT in adult patients. There is limited data on these benefits for the pediatric population especially for abdominopelvic CT examinations.

Objective: This study examines a reduced weight-based iodinated contrast dosing strategy in pediatric abdominopelvic CT on a PCD-CT system compared to standard dosing protocols on EID-CT using 1 mL/kg and 2 mL/kg, respectively. Image quality is assessed using both quantitative and qualitative measures. We also compare the radiation dose profile between the two PCD-CT and EID-CT cohorts.

Materials and methods: This HIPAA-compliant, IRB-approved, retrospective study included pediatric patients (≤18 years of age) who underwent contrast-enhanced CT examinations of the abdomen and pelvis for routine clinical care (01/2022 - 01/2023) in the portal-venous phase on a PCD-CT (NAEOTOM Alpha; Siemens Healthineers). Inclusion criteria included a similar prior examination within 12-months on a dual-source EID-CT scanner from the same vendor. All PCD-CT and EID-CT scans were acquired using weight-based dosing for intravenous contrast media, 1 mL/kg and 2 mL/kg, respectively, based on institutional protocols. Contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) were measured in the aorta, portal vein, liver parenchyma, and skeletal muscle. Three pediatric radiologists qualitatively evaluated each scan for overall image quality, noise, and contrast on a scale of 0-100. Confidence in small structure detection (common bile duct) was also rated on a scale of 0-3. Radiation doses (size-specific dose estimate (SSDE)) were calculated. Statistical analysis included paired t-tests and a mixed linear effects model to account for patient age, sex, and X-ray tube voltage. A P<0.05 indicated statistical significance.

Results: A total of 49 patients were included (24 female; mean [SD] age 9.9 [6.3] years, range 0.6-18 years). Compared to EID-CT, PCD-CT had a higher mean SNR in the portal vein (23.4 [SD=9.3] vs 17.2 [SD=7.4], P<0.001), aorta (23.4 [SD=11.6] vs 17.7 [10.1], P=0.017), hepatic parenchyma (15.2 [SD=5.6] vs 13.2 [5.1], P=0.016), and skeletal muscle (5.7 [SD=3.1] vs 4.5 [SD=3.1], P=0.01). Compared to EID-CT, PCD-CT also had a higher mean CNR in the portal vein (27.5 [SD=9.6] vs 22.1 [SD=21.1], P=0.003), aorta (27.3 [SD=9.6] vs 22.3 [SD=11.8], P=0.004), hepatic parenchyma (20 [SD=6.9] vs 16.9 [SD=8.5], P=0.013), and skeletal muscle (14.6 [4.9] vs 12.1 [5.6], P=0.008). Overall image quality, image noise, and small structure detection confidence scores were higher on PCD-CT than EID-CT (P=0.037, P<0.001, and P=0.006, respectively). Mean SSDE for PCD-CT was lower than EID-CT (9.1 mGy [SD=4.3] vs 11 mGy [5.9], P=0.012).

Conclusion: Compared with EID-CT, contrast-enhanced pediatric abdominopelvic CT offers improved subjective and objective image quality, even at lower radiation doses and reduced intravenous contrast medium volumes.