Spectral CT imaging in the diagnosis of pulmonary embolism using quantitative iodine-based material decomposition images / 中华放射学杂志

ABSTRACT

Objective To assess the diagnostic value of CT spectral imaging using quantitative iodine-based material decomposition images in the evaluation of pulmonary embolism. Methods Fifty-three patients underwent CT angiography with spectral imaging mode on a GE Discovery CT750HD scanner. Iodine distribution in the lung parenchyma using the iodine-based material decomposition images was quantitatively measured by post-processing. Monochromatic CT angiographic images were reconstructed from the same data sets and thee images were reviewed for the identification and localization of pulmonary embolism as well as the degree ( partial or complete) of the embolic occlusion. The number and location of perfusion defects were recorded. The iodine content of perfusion defects and normal lung parenchyma on the iodine maps were measured by one reader using an ROI analysis. Comparative analyses were obtained using the Chi-square test for categorical data. Two independent samples rank test and 2 related samples signed-rank test were used to compare iodine densities between different groups. Results CT angiography showed no pulmonary embolism in 33 patients, and iodine distribution was homogeneous. A total of 93 clots with lobar ( n = 26), segmental (n = 54) and sub-segmental (n=13) distribution were detected in 19 patients; Fifty-one clots were occlusive and 42 clots were non-occlusive. The iodine-based material decomposition images of all occlusive clots showed lobar, segmental or sub-segmental iodine distribution defects; whereas eleven of 42 non-occlusive clots had evidence of iodine distribution defects. There was significant difference ( x2 = 39. 94,P＜0. 01 ) in the perfusion defects between occlusive and non-occlusive clots. There was a significant difference in iodine content between normal lung parenchyma [ (1.92 ±0. 54) g/L] and perfusion defects [ (0. 30 ± 0. 20)g/L] (Z= -5.63, P ＜ 0. 01 ). There was a significant difference in the iodine content of peffusion defects before [ (0. 26 ± 0. 23 )g/L] and after anticoagulation [ (0. 94 ± 0. 50 )g/L ] ( Z = -3.93,P ＜ 0. 01 ). Conclusion With the ability of iodine mapping, CT spectral imaging is areliable method in the evaluation of pulmonary embolism both qualitatively and quantitatively, and may be a useful tool in providing information regarding the severity of PE and monitoring therapeutic efficacy.