The Study Of Multi-slice Computed Tomography Perfusion Imaging To The Diagnostic Value Of Peripheral Pulmonary Embolism

Objective: Approaching the display of MSCT perfusion imaging to lung perfusion defects within the lung parenchyma in segmental and subsegmental pulmonary embolism (PE), then evaluate its effects to diagnose.Methods and materials: MSCT pulmonary arteriography to 118 suspected PE patients was used; the patients was performed on 16-slice multi-detector-row CT scanner (GE),dorsal position,breath holding at the end of deep inspiration. Constrast medium intellect auto-track technology was used, chose proper retardation time scan according to the constrast medium peak value of main pulmonary artery,the scan ambit was upper bound to lower bound of lung and the orientation was from caudal to capitulum. Intravenous injection 100ml non-ionic contrast media via antebrachial vein, high pressure syringe was used, flow rate was 3.5ml/s. Scan parameters : 140kV, 100mAs, collimate:0.75×16mm, table speed :12mm/r, rotation speed: 0.37s/r. Axial source images were reconstructed with an effective slice thickness of 1.25 mm and imported to standard medical workstation (AW4.2) for observation and disposal. In the workstation , axial contrast-enhanced CTPA images were rated first, followed by an analysis of the combination images,the positions and numbers of embolus and the conditions of lung and mediastinum were recorded respectively. Rejected the patients of central pulmonary embolism and other diseases in lungs,we studied the patients of peripheral pulmonary embolism(group A) and normal(group B). A new image processing technique was deployed to group A and B.Based on these source images , an automated 3D-segmentation of the lungs was performed followed by threshold based extraction of major airways , vascular structures,chest wall and the interpleural space and so on. Through the function of erosion and dilation, the air wall and the main bronchi wall could be removed; The filtered volume data were color encoded and finally overlayed onto the original CT images. This color encoded display of parenchymal density distribution of the lung was shown in axial, coronal sagittal plane orientation and adlibitum incline plane. Observed the perfusion image, then recorded the location and numbers of perfusion defects. Compared the results of original CTPA and the perfusion image,the results were got: CTPA images display embolus and defects within perfusion images ,CTPA images display embolus but no defects within perfusion images,CTPA images display no embolus but defects within perfusion images.In the workstation , we rered the corresponding pulmonary artery that CTPA images without embolus but defects within perfusion images in group A and the perfusion defects in group B: reconstructive region-of-interest (0.75mm/0.5mm ) was carefully observed in axial contrast-enhanced CTPA and combined with the tech of MPR,CPR, MIP and VRT, we could affirm if there were embolus.Results: In the 118 patients, we elected 64 patients to study. Group A had 28 peripheral PE patients and group B had 36 normal patients.230 embolus were detected in group A. In the workstation,we applied perfusion image tech to group A and B ,then observed the images,428 perfusion defects were founded(351 within group A,77 within group B). Compared the original CTPA images with perfuse imaging of group A: CTPA images display embolus and defects within perfusion images were 205,CTPA images display embolus but no defects within perfusion images were 25,CTPA images display no embolus but defects within perfusion images were 146.In group B,29 patients displayed perfusion defects . Rered the pulmonary arteries that CTPA images displayed no embolus but defects within perfusion images in group A,97 occluded arteries were new found (39 segmental arteries , 58 subsegmental arteries). Rered the corresponding pulmonary arteries with perfusion defects in group B,25 PE patients were new diagnosed and 68 occluded arteries were new found (27 segmental arteries,41 subsegmental arteries). Combination of CTPA and perfusion imaging compared with sole CTPA can evident raise the diagnostic correct rate to PE(χc2=23.04, P<0.001) .The sensitivity of perfusion defects to display the embolus was 93.7%, and positive predictive value was 86.4%.Conclusions: The apply of MSCT perfusion imaging could display the lung perfusion defects within the parenchyma led by the blood current decrease within downstream of occluded subsegmental arteries, showing lower or missing enhancement compared with normally perfused lung parenchyma. The display of the perfusion defects was important indirect signs for the diagnosis of PE. It can raise the sensibility of finding extenuation artery embolism and cue tiny artery embolism that CTPA can't find. Perfusion imaging provides the double information of morphology and function,offering comprehensive assessment on PE patients.