Can virtual monochromatic images from dual-energy CT replace low-kVp images for abdominal contrast-enhanced CT in small- and medium-sized patients?

OBJECTIVE: To investigate the image quality and radiation dose of dual-energy computed tomography (DECT) with automatic spectral imaging protocol selection (ASIS) compared with those of low-kVp CT in abdominal multiphase CT. METHODS: Four groups of 60 patients each underwent abdominal scans with low-kVp CT (A, 80 kVp/300 mg I/kg, body mass index [BMI] ≤ 23.9 kg/m2; C, 100 kVp/400 mg I/kg, BMI ranging from 24 to 28.9 kg/m2) or DECT with ASIS, and the 40- to 60-keV virtual monochromatic images (VMIs) generated (B and D) were matched by age, gender, BMI, cross-sectional area, and contrast agent dose; 9 patients were excluded due to technical failures. The CT number, image noise, contrast-to-noise ratio, and subjective image quality were compared between the matched protocols (A and B or C and D) on 1.25-mm reconstructed images. RESULTS: VMIs at approximately 55 keV and 62 keV had CT numbers and contrast similar to those of 80-kVp and 100-kVp CT images, respectively. Compared to matched low-kVp images, VMIs at 50 keV provided a higher CT number and image noise and a similar or higher contrast and overall image quality. The radiation dose for DECT was higher than that of 80-kVp CT (increased by 10%), but was similar to that of 100-kVp CT. CONCLUSION: Compared to matched low-kVp CT, VMIs at 50 keV in DECT with ASIS provided similar or higher overall image quality, with no or minimal dose penalty in small- and medium-sized patients. KEY POINTS: • Virtual monochromatic images at approximately 55 keV and 62 keV have CT numbers and contrast similar to those of 80-kVp and 100-kVp CT images, respectively, with a given noise index. • The radiation dose in dual-energy CT with automatic spectral imaging protocol selection was slightly higher than that of 80-kVp CT (increased by 10%) but was similar to that of 100-kVp CT. • Dual-energy CT may be able to replace l00-kVp CT for routine clinical abdominal contrast-enhanced CT scans.

Duke Scholars

Author Daniele Marin Radiology, Abdominal Imaging