Detection of iodine and air distribution in abnormal pulmonary perfusion using spectral CT imaging
YU Meng-meng1, BAI Xue-dong2, CHEN Rong1, ZHANG Di1, JI Yang1, SU Bei-er1, WANG Dan1
1. Department of Radiology, the Fourth Affiliated Hospital of Harbin Medical University, Harbin 150001, China;2. Department of Radiology, the Affiliated Hospital of Chengde Medical College, Chengde Hebei 067000, China
Abstract：Objective: To explore the feasibility of using spectral CT to evaluate the distribution of iodine and air in pulmonary perfusion disorders with different pathological changes. Materials and Methods: Seventy patients suspected of pulmonary embolism underwent CT scanning with GE Discovery CT 750HD scanner. 70 keV CTPA images, iodine-based material decomposition images and Min IP images were acquired. Location, type and number of pulmonary emboli were observed on CTPA. Location and type of abnormal perfusion were observed on iodine-based material decomposition images, and iodine content was calculated. Aeration of abnormally perfused lung parenchyma was analyzed based on Min IP images. Results: In 33 normal persons, CTPA showed no pulmonary embolism, with even iodine distribution. Iodine content in anterior, middle and posterior regions of lung parenchyma showed gradient distribution from ventral to dorsal. There was no obvious difference between left and right lungs(P>0.05) for iodine, and air distributed homogeneously on Min IP. In 18 patients with pulmonary embolism, a total of 110 emboli were found, including 38 occlusive clots and 72 non-occlusive clots. Thirty-five cases with non-occlusive clots showed reduced perfusion(iodine content 0.62 mg/mL), and the air content presented no obvious increment. Perfusion exhibited noticeable reduction in all cases with occlusive clots(iodine content 0.13 mg/mL), and the air content increased on Min IP. Five patients with pulmonary ground-glass opacity showed areas of hyper-perfusion(iodine content 2.56 mg/mL) and reduced aeration on the Min IP. Six patients with pulmonary hypertension showed diffuse perfusion defect of iodine(iodine content 0.48 mg/mL) but normal CTPA. On Min IP, areas of increased aeration were seen, corresponding to the areas of reduced perfusion. In 4 cases of diffuse emphysema, the iodine content was 0.20 mg/mL. Areas with markedly reduced density on the Min IP matched those with reduced perfusion on the iodine maps. In 4 cases of interstitial fibrosis, reduced perfusion(iodine content -0.07 mg/mL) of the pulmonary parenchyma was found, together with reduced aeration on Min IP. Conclusions: Spectral CT imaging is able to quantitatively measure the content of iodine and the distribution of gas in lungs with different pathological changes, which can be used as a visualization of the pulmonary blood flow/ventilation changes.
2014, Vol. 25 
