Dual-energy computed tomographic pulmonary angiography: a pilot study to assess the effect on image quality and diagnostic confidence.

PURPOSE: The aim of this study was to assess if dual-energy computed tomographic pulmonary angiography (DE-CTPA) protocol performed on a dual-source CT scanner can improve image quality and diagnostic confidence compared with 80- and 140-kilovolt (peak) (kVp) image data sets.

MATERIALS AND METHODS: In an international review board-approved study, 22 patients (women-men, 12:10; mean [SD] age, 58.5 [16.5] years; age range, 18-85 years) underwent DE-CTPA on a dual-source CT for assessing pulmonary embolism. Scan parameters comprised reference milliampere-second of 140 at 140 kVp and 400 at 80 kVp with a pitch of 1.1- and 1.25-mm reconstructed slice thicknesses, respectively. Two radiologists analyzed the 140-kV, 80-kV, and dual-kilovolt images for vessel contrast, subjective image noise, presence of motion, artifacts, and diagnostic confidence at the level of main, lobar, and segmental or subsegmental pulmonary arteries on a 5-point scale (1, uninterpretable; 5, excellent). Computed tomographic numbers and objective noise were measured in these arteries. Data were analyzed using Student t test, Friedman chi2 analysis of variance, and Wilcoxon rank sum test (with Bonferroni correction).

RESULTS: At 80 kVp, regardless of motion artifacts, there was a 104% increase in intravascular CT numbers, (mean [SD], 257 [104] Hounsfield units [HU] at 140 kVp and 525 [214] HU at 80 kVp) and 75% increase in objective noise (20 HU at 140 kVp and 35 HU at 80 kVp). Improvement in subjective contrast opacification and CT numbers with 80 kVp compared with 140 kVp was most marked in interlobar, segmental, and subsegmental arteries. Effective radiation dose decrease approximately 28% from a CTDI vol of 26.7 mGy to 20.1 mGy between dual-energy (case) and single-energy (control) groups. In conclusion, DE-CTPA has potential advantages for evaluations of pulmonary embolism and regarding improved image noise, vessel contrast, and diagnostic confidence compared with single higher-kilovolt (peak) protocols.