Imaging Evaluation Of Peripheral Pulmonary Embolism And A Comparision Study With Pathology

Objective: By watching the dynamic changing process of animal models of peripheral pulmonary embolism(PE) with multiple imaging methods such as DSA, HCT, MRI and ECT, evaluating the roles of them in diagnosis of peripheral PE, and then comparing imaging appearances with pathologic findings , to improve the acknowledgement of the imaging appearance and the use of different imaging methods in diagnosing peripheral PE, give proof for the correct and prompt diagnosis to clinicians.Subjects and Methods: Eight dogs were studied. Animals were anesthetized and intubated, then a catheter was introduced into the main pulmonary artery to make peripheral PE models by injecting the clots-gelatin sponge. 1 hour, 3 day, 7 day , 14 day and 28 day after PE, HCT, MRI, or ECT were done to dynamically observe the imaging appearance and the changing process.After dogs were died,HE staining and immunohistochemistry staining were done respectively.And the pathologic appearance,small vessles density and the expression of basicfibroblast growth factor(bFGF) were watched respectively.Results: All dogs were made peripheral PE models successfully. DSA manifestations: 31 embolismic pulmonary arteries were found on DSA, the sensitivity of diagnosis was 80.6%,specificity 98.7%. HCT manifestations: (1)After PE, 5 animals had abnormal changes, 3 animals(37.5%) showed platelike atelectasis and 1 animal(12.5 % ) presented patchy areas of infiltration,2 animals(25%) showed Westermark signs in embolism lung; (2)On HCTPA, 30 arteries were diagnosed to be embolized, only 4 of 14 subsegmental arteries was correctly diagnosed. The sensitivity of HCTPA was 75%, specificity 93.2%. If the subsegmental emboli were not counted, the sensitivity would increase to 90.9%; (3)Enhanced HCT found the CT values of the embolic pulmonary parenchyma were obviously lower than that of the normal parenchyma(p<0.01), and on unenhancd HCT, the CT values between them were similar(p>0.05). MRI manifestations:(1)MRI also observed the atelectasis and infiltration after PE and the findings were identical with HCT;(2)27 embolic arteries were manifested on CE MRPA, with the sensitivity 66.7%, specificity 93.2%. 2 of 14 subsegmental emboli were correctly diagnosed. If the subsegmental emboli were not counted, the sensitivity would increase to 90.9%. MPR helped to find 4 embolic arteries which were not evident on the original images;(3)30 low perfusion areas of PE were observed on CE MRPP, with the sensitivity 75%, specificity 98.1%. The time-signal intensity curve of embolic parenchyma was evidently different with which of the normal parenchyma. 5 PE animal models showed low perfusion with the normal ventilation in embolismic areas with ECT V-P imaging.After PE,blood cells and fluid were found in pulmonary alveolus by HE staining.Blood cells and fluid were absorbed gradually, and recoveried normally on 28 day after PE.Tissue necrosis was not found.Small vessles density was increased on 7th day to 28th day after PE.The bFGF was increased from 1st day to 14th day after PE,and decreased to normal on 28th day.Conclusions: (1)HCTPA can manifest the emboli or the obstruction of the pulmonary arteries and make direct diagnosis of PE. PE of segmental arteries can be diagnosed with high sensitivity. (2) Enhanced HCT can find the low perfusion appearance due to embolism and make indirect diagnosis of PE when without finding the emboli. (3)Abnormalities of pulmonary parenchyma after PE could be found by unenhanced HCT,and disappeared gradually with orangic recorvery. (4)CE MRPA can also manifest the emboli or the obstruction of the pulmonary arteries and diagnose the segmental embolism correctly. The application of MPR is helpful in diagnosing the indistinct embolic arteries on the original images of CE MRPA. (5)CE MRPP can manifest the low perfusion areas due to embolism distinctly and then make indirect diagnosis of PE. (6)Both HCTPA and ECT V-P can serve as the first line examination methods for diagnosis of PE.(7) After PE, bFGF is increased obviously. it is one of factors to improve formation of collateral arteries between pulmonary artery system and bronchial artery system, and also to improve orangic recovery.