RATIONALE AND OBJECTIVES: To compare tumor conspicuity of small hepatocellular carcinomas (HCCs) and image quality on knowledge-based iterative model reconstruction low-dose computed tomography (IMR-LDCT) with hybrid iterative reconstruction standard-dose CT (iDose4-SDCT). METHODS: Thirty-two patients (mean age 61.9 ± 9.7 years; male:female 27:5; mean body mass index 25.6 ± 3.8 kg/m2) with cirrhosis and 40 HCCs in IMR-LDCT group and 33 patients (mean age 60.1 ± 7.4 years; male:female 28:5; body mass index 26.7 ± 3.2 kg/m2) with cirrhosis and 40 HCCs in iDose4-SDCT group were included in this retrospective study. Objective analysis of reconstructed iDose4 and IMR images was done for contrast-to-noise ratio of HCCs (CNRHCC), image noise, signal-to-noise ratio of portal vein (SNRPV), and inferior vena cava (SNRIVC). Subjective analysis of tumor conspicuity and image quality was done by two independent reviewers in a blinded manner. Mean volume CT dose index, dose length product, and effective dose for both groups were compared. RESULTS: The CNRHCC was significantly higher in IMR-LDCT compared to iDose4-SDCT in both arterial phase (AP), p < 0.0001, and delayed phase (DP), p < 0.0001. Image noise was significantly lower in IMR-LDCT compared to iDose4-SDCT in AP, portal venous phase, and DP with p < 0.0001. IMR-LDCT showed significantly higher SNRPV (p < 0.0001) and SNRIVC (p < 0.0001) compared to iDose4-SDCT. On subjective analysis, IMR-LDCT images showed better image quality in AP, portal venous phase, and DP and better tumor conspicuity in AP and DP. IMR-LDCT (21.4 ± 4.6 mSv) achieved 36.9% reduction in the effective dose compared to iDose4-SDCT (33.9 ± 6.2 mSv). CONCLUSION: IMR algorithm provides better image quality and tumor conspicuity with considerable decrease in image noise compared to iDose4 reconstruction technique even on LDCT.
RATIONALE AND OBJECTIVES: To compare tumor conspicuity of small hepatocellular carcinomas (HCCs) and image quality on knowledge-based iterative model reconstruction low-dose computed tomography (IMR-LDCT) with hybrid iterative reconstruction standard-dose CT (iDose4-SDCT). METHODS: Thirty-two patients (mean age 61.9 ± 9.7 years; male:female 27:5; mean body mass index 25.6 ± 3.8 kg/m2) with cirrhosis and 40 HCCs in IMR-LDCT group and 33 patients (mean age 60.1 ± 7.4 years; male:female 28:5; body mass index 26.7 ± 3.2 kg/m2) with cirrhosis and 40 HCCs in iDose4-SDCT group were included in this retrospective study. Objective analysis of reconstructed iDose4 and IMR images was done for contrast-to-noise ratio of HCCs (CNRHCC), image noise, signal-to-noise ratio of portal vein (SNRPV), and inferior vena cava (SNRIVC). Subjective analysis of tumor conspicuity and image quality was done by two independent reviewers in a blinded manner. Mean volume CT dose index, dose length product, and effective dose for both groups were compared. RESULTS: The CNRHCC was significantly higher in IMR-LDCT compared to iDose4-SDCT in both arterial phase (AP), p < 0.0001, and delayed phase (DP), p < 0.0001. Image noise was significantly lower in IMR-LDCT compared to iDose4-SDCT in AP, portal venous phase, and DP with p < 0.0001. IMR-LDCT showed significantly higher SNRPV (p < 0.0001) and SNRIVC (p < 0.0001) compared to iDose4-SDCT. On subjective analysis, IMR-LDCT images showed better image quality in AP, portal venous phase, and DP and better tumor conspicuity in AP and DP. IMR-LDCT (21.4 ± 4.6 mSv) achieved 36.9% reduction in the effective dose compared to iDose4-SDCT (33.9 ± 6.2 mSv). CONCLUSION: IMR algorithm provides better image quality and tumor conspicuity with considerable decrease in image noise compared to iDose4 reconstruction technique even on LDCT.