Advantages and disadvantages of single-source dual-energy whole-body CT angiography with 50% reduced iodine dose at 40 keV reconstruction

Abstract

Objectives: To assess the feasibility of whole-body dual-energy computed tomographic angiography (DECTA) at 40 keV with 50% reduced iodine dose protocol.

Methods: Whole-body CTA was performed in 65 patients; 31 of these patients underwent 120 kVp single-energy computed tomographic angiography (SECTA) with standard iodine dose (600 mgI/kg) and 34 with 40 keV DECTA with 50% reduced iodine dose (300 mgI/kg). SECTA data were reconstructed with adaptive statistical iterative reconstruction of 40% (SECTA group), and DECTA data were reconstructed with adaptive statistical iterative reconstruction of 40% (DECTA-40% group) and 80% (DECTA-80% group). CT numbers of the thoracic and abdominal aorta, iliac artery, background noise, signal-to-noise ratio (SNR), and arterial depiction were compared among the three groups. The CT dose index volumes (CTDI_vol) for the thorax, abdomen, and pelvis were compared between SECTA and DECTA protocols.

Results: The vascular CT numbers and background noise were found to be significantly higher in DECTA groups than in the SECTA group (p < 0.001). SNR was significantly higher in the order corresponding to DECTA-80%, SECTA, and DECTA-40% (p < 0.001). The arterial depiction was comparable in almost all arteries; however, intrapelvic arterial depiction was significantly worse in DECTA groups than in the SECTA group (p < 0.0001-0.017). Unlike the pelvic region (p = 0.055), CTDI_vol for the thorax (p < 0.0001) and abdomen (p = 0.0031) were significantly higher in the DECTA protocol than in the SECTA protocol.

Conclusion: DECTA at 40 keV with 50% reduced iodine dose provided higher vascular CT numbers and SNR than SECTA, and almost comparable arterial depiction, but had a degraded intrapelvic arterial depiction and required a larger radiation dose.

Advances in knowledge: DECTA enables 50% reduction of iodine dose while maintaining image quality, arterial depiction in almost all arteries, vascular CT numbers, and SNR; however, it does not allow clear visualization of intrapelvic arteries, requiring a slightly larger radiation dose compared with SECTA with standard iodine dose.

Figure 1.

A 78-year-old male with abdominal aortic aneurysm. Single-energyCTA obtained with standard iodine dose (600 mgI/kg) at 120 kVp. Anterior whole-body volume-rendered CTA (a) with and (b) without bone, and (c) maximum intensity projection image clearly shows the aorta, abdominal aortic aneurysm, and arterial branches, especially in intrapelvic arteries compared to dual-energy CTA in Figures 2 and 3. (d) Axial CTA of the pelvis clearly shows intrapelvic arteries. CTA, CT angiography.

Figure 2.

An 82-year-old male with aortic dissection in the ascending aorta. Dual-energy CTA obtained with 50% reduced iodine dose (300 mgI/ kg) at 40 keV. Anterior whole-body volume-rendered CTA reconstructed with ASiR of 40% (a) with and (b) without bone, and (c) maximum intensity projection image clearly shows the aorta and its arterial branches. (d) Axial CTA of the pelvis clearly shows the intrapelvic arteries, but background noise is relatively marked. ASiR, adaptive statistical iterative reconstruction; CTA, CT angiography.

Figure 3.

An 82-year-old male with aortic dissection in the ascending aorta, the same case as in Figure 2. Dual-energy CTA obtained with 50% reduced iodine dose (300 mgI/kg) at 40 keV. Anterior whole-body volume-rendered CTA reconstructed with ASiR of 80% (a) with and (b) without bone, and (c) maximum intensity projection image clearly shows the aorta and its arterial branches. (d) Axial CTA of the pelvis clearly shows the intrapelvic arteries, and background noise is reduced compared with the case shown in Figure 2d. ASiR, adaptive statistical iterative reconstruction; CTA, CT angiography.