Low-iodine-dose computed tomography coupled with an artificial intelligence-based contrast-boosting technique in children: a retrospective study on comparison with conventional-iodine-dose computed tomography

Abstract

Background: Low-iodine-dose computed tomography (CT) protocols have emerged to mitigate the risks associated with contrast injection, often resulting in decreased image quality.

Objective: To evaluate the image quality of low-iodine-dose CT combined with an artificial intelligence (AI)-based contrast-boosting technique in abdominal CT, compared to a standard-iodine-dose protocol in children.

Materials and methods: This single-center retrospective study included 35 pediatric patients (mean age 9.2 years, range 1-17 years) who underwent sequential abdominal CT scans-one with a standard-iodine-dose protocol (standard-dose group, Iobitridol 350 mgI/mL) and another with a low-iodine-dose protocol (low-dose group, Iohexol 240 mgI/mL)-within a 4-month interval from January 2022 to July 2022. The low-iodine CT protocol was reconstructed using an AI-based contrast-boosting technique (contrast-boosted group). Quantitative and qualitative parameters were measured in the three groups. For qualitative parameters, interobserver agreement was assessed using the intraclass correlation coefficient, and mean values were employed for subsequent analyses. For quantitative analysis of the three groups, repeated measures one-way analysis of variance with post hoc pairwise analysis was used. For qualitative analysis, the Friedman test followed by post hoc pairwise analysis was used. Paired t-tests were employed to compare radiation dose and iodine uptake between the standard- and low-dose groups.

Results: The standard-dose group exhibited higher attenuation, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR) of organs and vessels compared to the low-dose group (all P-values < 0.05 except for liver SNR, P = 0.12). However, noise levels did not differ between the standard- and low-dose groups (P = 0.86). The contrast-boosted group had increased attenuation, CNR, and SNR of organs and vessels, and reduced noise compared with the low-dose group (all P < 0.05). The contrast-boosted group showed no differences in attenuation, CNR, and SNR of organs and vessels (all P > 0.05), and lower noise (P = 0.002), than the standard-dose group. In qualitative analysis, the contrast-boosted group did not differ regarding vessel enhancement and lesion conspicuity (P > 0.05) but had lower noise (P < 0.05) and higher organ enhancement and artifacts (all P < 0.05) than the standard-dose group. While iodine uptake was significantly reduced in low-iodine-dose CT (P < 0.001), there was no difference in radiation dose between standard- and low-iodine-dose CT (all P > 0.05).

Conclusion: Low-iodine-dose abdominal CT, combined with an AI-based contrast-boosting technique exhibited comparable organ and vessel enhancement, as well as lesion conspicuity compared to standard-iodine-dose CT in children. Moreover, image noise decreased in the contrast-boosted group, albeit with an increase in artifacts.

Keywords: Artificial intelligence; Computed tomography; Contrast enhancement; Image quality; Iodine; Pediatrics.

Fig. 1

Axial contrast-enhanced computed tomography (CT) images of a 9-year-old boy with upper arm synovial sarcoma. Sequential abdominal CT was conducted within 2 months. a Standard-dose image shows excellent organ (liver, 167.6 ± 9.0 Hounsfield unit (HU)) and vessel (aorta, 327.0 ± 16.7 HU; portal vein, 324.8 ± 10 HU) enhancement with some grainy noise. b Low-dose image exhibits decreased organ (liver, 152.0 ± 12.1 HU) and vessel (aorta, 208.2 ± 12.6 HU; portal vein, 228.2 ± 14.9 HU) enhancement with persistent grainy noise. c Contrast-boosted image shows excellent organ (liver, 174.7 ± 9.5 HU) and vessel (aorta, 260.0 ± 11.9 HU; portal vein, 285.2 ± 12.1 HU) enhancement with reduced grainy noise. The qualitative organ enhancement scores for the standard-dose, low-dose, and contrast-boosted images were 4/4, 3/3, and 4/4, respectively (reader 1’s score/reader 2’s score). Vessel enhancement scores were 5/4, 3/3, and 4/4, whereas noise scores were 3/4, 3/3, and 4/4. Overall image quality scores were 4/4, 4/3, and 4/4

Fig. 2

Axial contrast-enhanced computed tomography (CT) images of a 1-year-old girl with adrenal gland neuroblastoma and liver metastasis. Sequential abdominal CT was conducted within 3 months. a Standard-dose image shows a 1.3 cm relatively well-defined low attenuated metastatic nodule in liver segment 7/8 (arrow). b Low-dose image shows a 1.1-cm ill-defined low attenuated metastatic nodule in liver segment 7/8 (arrow). c In the contrast-boosted image, the nodule looks more well-defined (arrow) and the lesion conspicuity is improved compared to the low-dose image. The qualitative lesion conspicuity scores of the standard-dose, low-dose, and contrast-boosted images were 4/4, 3/3, and 4/4, respectively (reader 1’s score/reader 2’s score)

Fig. 3

Axial contrast-enhanced computed tomography (CT) images of a 2-year-old girl with immature teratoma. Sequential abdominal CT was conducted within 4 months. a Standard-dose image shows a minimal streak artifact underneath both ribs (arrows). b Low-dose image shows a mild streak artifact underneath both ribs (arrows). c In the contrast-boosted image, the streak artifact is more prominent in the more enhanced liver and spleen (arrows). The qualitative artifact scores of the standard-dose, low-dose, and contrast-boosted images were 5/4, 4/4, and 3/3, respectively (reader 1’s score/reader 2’s score)