William P Shuman1, Ryan B O'Malley2, Janet M Busey2, Mario M Ramos2, Kent M Koprowicz2. 1. Department of Radiology, University of Washington, 1959 NE Pacific Street, Box 357115, Seattle, WA, 98195, USA. wshuman@uw.edu. 2. Department of Radiology, University of Washington, 1959 NE Pacific Street, Box 357115, Seattle, WA, 98195, USA.
Abstract
PURPOSE: To compare dual-energy computed tomography (DECT) aortography using a 70% reduced iodine dose to single-energy CT (SECT) aortography using a standard iodine dose in the same patient. METHODS: Twenty-one patients with a prior SECT aortography using standard iodine dose had DECT aortography using 70% reduced iodine dose. Section 120 kVp images were compared to DECT images reconstructed at both 50 and 77 keV. Reviewers measured image noise and attenuation in the aorta at eight locations from proximal to distal and subjectively scored vascular enhancement on a four-point scale. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. The volume CT dose index (CTDIvol) for each exam was recorded. RESULTS: Mean iodine dose was 50 g for SECT and 15 g for DECT (70% reduction). Mean aortic attenuation was similar for section 120 kVp (350 ± 67 HU) and DECT 50 keV (338 ± 57 HU, p = 0.547) but was lower at 77 keV (152 ± 23 HU). Measured image noise was greatest at 50 keV (12 ± 5 HU) and was lowest at 77 keV (7 ± 2 HU, p > 0.001). There was no difference in SNR or CNR between 120 kVp and 50 keV (p > 0.05). Mean subjective vascular enhancement scores for SECT were between good and excellent (3.33-3.69), and for DECT at 50 keV were between moderate and good (2.54-2.93, p < 0.0001). CTDIvol was 13.6 mGy for SECT and 13.1 mGy for DECT (p = 0.637). CONCLUSION: 70% Reduced iodine DECT aortography may result in similar aortic attenuation, CNR, SNR, and lower although acceptable subjective image scores when compared to standard iodine SECT aortography in the same patient.
PURPOSE: To compare dual-energy computed tomography (DECT) aortography using a 70% reduced iodine dose to single-energy CT (SECT) aortography using a standard iodine dose in the same patient. METHODS: Twenty-one patients with a prior SECT aortography using standard iodine dose had DECT aortography using 70% reduced iodine dose. Section 120 kVp images were compared to DECT images reconstructed at both 50 and 77 keV. Reviewers measured image noise and attenuation in the aorta at eight locations from proximal to distal and subjectively scored vascular enhancement on a four-point scale. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were calculated. The volume CT dose index (CTDIvol) for each exam was recorded. RESULTS: Mean iodine dose was 50 g for SECT and 15 g for DECT (70% reduction). Mean aortic attenuation was similar for section 120 kVp (350 ± 67 HU) and DECT 50 keV (338 ± 57 HU, p = 0.547) but was lower at 77 keV (152 ± 23 HU). Measured image noise was greatest at 50 keV (12 ± 5 HU) and was lowest at 77 keV (7 ± 2 HU, p > 0.001). There was no difference in SNR or CNR between 120 kVp and 50 keV (p > 0.05). Mean subjective vascular enhancement scores for SECT were between good and excellent (3.33-3.69), and for DECT at 50 keV were between moderate and good (2.54-2.93, p < 0.0001). CTDIvol was 13.6 mGy for SECT and 13.1 mGy for DECT (p = 0.637). CONCLUSION: 70% Reduced iodine DECT aortography may result in similar aortic attenuation, CNR, SNR, and lower although acceptable subjective image scores when compared to standard iodine SECT aortography in the same patient.
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