Room: Exhibit Hall | Forum 9
Purpose: To evaluate image quality of virtual monochromatic images reconstructed from dual-energy CT (DECT).
Methods: CT scans of a Catphan 504 phantom were acquired on a commercial DECT scanner (1.5 mm slices, 0.6 pitch). DECT images were acquired simultaneously using two x-ray tubes (80, & 150 kVp). 120 kVp single tube scans were acquired to compare the DECT results with a standard imaging technique. Three physical setups were utilized to evaluate consistency. Scans were acquired at different effective mAs to permit equi-dose comparisons of low contrast visibility (LCV), uniformity (ÏƒHU), and spatial frequency (MTF50) of the source images and monochromatic reconstructions from the DECT.
Results: For 300 mAs scans, the reported dose was 13 mGy for the DECT scan and 20 mGy for the 120 kVp scan. A 200 mAs 120 kVp scan replicated the 13 mGy DECT dose. Dose was halved (6.6 mGy) for a 150 mAs DECT. Monochromatic images with E>60 keV have lower LCV and ÏƒHU than their source images and lower than the equi-dose 120 kVp images. Monochromatic LCV and ÏƒHU increased with decreasing energy for E<70 keV, and were flat from 70-190 keV. The MTF50 varied little with reconstruction energy, and for the source images. The mean value was 0.55 at 300mAs and 0.47 at 150mAs. At 150 mAs LCV and ÏƒHU increased by 34% and 44% respectively, and reduced MTF50 by 17%.
Conclusion: Synthetic monochromatic images derived from DECT have better LCV and ÏƒHU than equi-dose 120 kVp scans and could improve low contrast detectability by reducing noise.