Dual-energy CT Aortography with 50% Reduced Iodine Dose Versus Single-energy CT Aortography with Standard Iodine Dose
William P Shuman1, Keith T Chan1, Janet M Busey1
1Department of Radiology, University of Washington School of Medicine, Box 357115, 1959 NE Pacific Street, Seattle, WA 98195.
Insights
Dual-energy CT (DECT) aortography with 50% less iodine provides excellent aortic visualization, comparable to standard-dose single-energy CT (SECT). This reduced iodine approach offers a safe and effective alternative for patients with renal issues.
Area of Science:
- Radiology
- Medical Imaging
- Cardiovascular Imaging
Background:
- Patients with aortic pathology often have impaired renal function, necessitating reduced iodine contrast doses.
- Standard-dose single-energy computed tomography (SECT) aortography carries risks for these patients.
- Dual-energy computed tomography (DECT) offers potential for dose reduction while maintaining image quality.
Purpose of the Study:
- To evaluate DECT aortography with a 50% reduced iodine dose against standard-dose SECT aortography.
- To assess image quality metrics including aortic attenuation, noise, and enhancement.
- To compare radiation dose between DECT and SECT.
Main Methods:
- Fifty patients underwent DECT aortography with 50% reduced iodine dose.
- Thirty-four patients had prior SECT aortography with standard iodine dose for comparison.
- DECT images were reconstructed at 50 and 77 keV; image noise, attenuation, and enhancement were scored. Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were calculated.
Main Results:
- Mean iodine dose was significantly lower in DECT (24 g) versus SECT (47 g).
- DECT at 50 keV yielded higher aortic attenuation (570 HU) than 77 keV DECT (239 HU) or SECT (356 HU) (P<0.05).
- SNR and CNR were comparable between 50 keV DECT and standard SECT, with similar vascular enhancement scores.
Conclusions:
- DECT aortography with 50% reduced iodine at 50 keV achieves superior aortic attenuation and good enhancement compared to standard SECT.
- Image noise at 77 keV DECT was comparable to standard SECT.
- DECT with reduced iodine is a viable alternative for aortic imaging in patients with renal compromise.
Rationale And Objectives:
Because many patients with aortic pathology also have compromised renal function, we wished to investigate dual-energy computed tomography (DECT) aortography with 50% reduced iodine dose compared to single-energy computed tomography (SECT) aortography with standard iodine dose.
Materials And Methods:
Fifty patients had DECT aortography with 50% reduced iodine dose. Thirty-four of these patients had prior SECT aortography with standard iodine dose. DECT images were reconstructed at both 50 and 77 keV and were compared to SECT 120 kVp images. Reviewers measured aortic attenuation, image noise, and scored vascular enhancement. Signal-to-noise ratios (SNR) and contrast-to-noise ratios (CNR) were calculated. Volume CT dose index was recorded.
Results:
Mean iodine dose was 47 g for SECT and 24 g for DECT. Aortic attenuation was highest at reduced iodine dose DECT 50 keV (570 ± 105 Hounsfield units [HU]) compared to 77 keV (239 ± 40 HU) or to standard iodine dose SECT 120 kVp (356 ± 69 HU) (P < 0.05). Image noise was greatest at 50 keV compared to 77 keV and 120 kVp (P < 0.05) but was similar between 77 keV and 120 kVp (P > 0.05). SNR and CNR were the same at 50 keV and 120 kVp (P > 0.05). Mean vascular enhancement scores were all above 3.0 (good, typical enhancement). Volume CT dose index was 11.7 mGy for DECT and 11.8 mGy for SECT (P = 0.37).
Conclusions:
DECT aortography with 50% reduced iodine reconstructed at 50 keV resulted in significantly greater aortic attenuation, good subjective vascular enhancement, and comparable SNR and CNR compared to standard iodine dose SECT. DECT image noise at 77 keV was similar to SECT at 120 kVp.
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