Prospective respiratory-triggered 64-slice CT pulmonary angiography for detection of pulmonary embolism—a feasibility study in a porcine model

The objective of this study is to investigate the feasibility of prospectively respiratory-triggered CT pulmonary angiography (CTPA) for detection of pulmonary embolism (PE) in a porcine model. A free-breathing respiratory-triggered multislice CTPA (120 kV, 140 mAs_eff, 2.5-mm slice thickness) and two CTPA in breath-hold technique (120 kV, 140 mAs_eff. and 250mAs_eff, 1-mm and 3-mm image reconstruction) were performed in six pigs with pulmonary embolism. Diagnostic accuracy was computed, and differences in detection rates between both techniques were assessed on a per-embolus basis with the Wilcoxon test. Thin-sliced 1-mm images, acquired with 250mAs_eff, served as the standard of reference. Respiratory-triggered CTPA reached high diagnostic accuracy in detection of lobar and segmental PE equal to the results with the breath-hold technique (p > 0.05). For detection of subsegmental emboli, standard breath-hold techniques performed significantly better than respiratory-gated CTPA (sensitivity, 68.3% versus 24.4%; p < 0.05). Free-breathing respiratory-triggered CTPA is feasible for detection of lobar and segmental PE, with diagnostic accuracy equivalent to that of a standard CTPA in breath-hold. Although this technique is not recommended for assessment of emboli in the subsegmental vasculature, prospective respiratory-triggered CTPA may be of added value in patients who cannot hold their breath appropriately for CTPA scanning.