Feasibility of single scan for simultaneous evaluation of pulmonary ventilation and perfusion with dual-energy CT : an experimental study

Abstract

Purpose: To evaluate the feasibility of simultaneous single scan of krypton ventilation and iodine perfusion using dual-energy CT (DECT).

Materials & Methods: The study was approved by institutional animal experimental committee. For 10 beagle dogs, we first made an airway obstruction and then, a pulmonary arterial occlusion after one week. For each animal model, 3 sessions of DECT (Single static scan at the end of 80% krypton ventilation without iodine enhancement [krypton CT], 80% krypton ventilation with iodine enhancement [mixed contrast CT], iodine enhancement after a 30-minute washout with O2 [iodine CT]) were performed. Krypton maps were made for krypton CT and mixed contrast CT, and iodine maps were made for mixed contrast CT and iodine CT. Two radiologists assessed the presence of krypton or iodine defects on each map, and measured the overlay HU in the diseased segment and contralateral control segment. Results were compared between krypton maps of krypton CT and mixed contrast CT, and between iodine maps of iodine CT and mixed contrast CT using the Wilcoxon signed-rank test.

Results: In airway obstruction models, krypton defects were visually distinguishable only in the diseased segment on the krypton map of krypton CT, but not in mixed contrast CT. However, measured overlay HU values of the diseased segment (3.5 ± 1.4 and 39.9 ± 1.4, respectively) on krypton maps were significantly decreased compared to the contralateral segment (17.7 ± 2.6 and 46.3 ± 4.4, respectively) in both krypton CT and mixed contrast CT (P = 0.002 for both). In all pulmonary arterial occlusion models, iodine defects were noted in the diseased segment on the iodine map either from iodine CT or mixed contrast CT. In iodine maps of the pulmonary arterial occlusion model, measured overlay HU values were significantly lower in the diseased segment (9.51±4.72 and 13.78±4.49, respectively) than in the contralateral segment (86.7 ±10.4 and 90.2 ± 6.6, respectively) in both iodine CT and mixed contrast CT (P = 0.002 for both).

Conclusion: Although some qualitative limitations may exist, it might be feasible to analyze pulmonary ventilation and perfusion simultaneously using DECT.