| PREFACECT perfiision imaging describes a rapid sequence of images acquired after the injection of intravascular contrast medium at the same slice, generates the time - density curve of each pixel in the slice and calculates perfusion parameters by different mathematical models. As a functional imaging, it combines fine anatomical details and quantitative information about perfusion in the same scan sequence and becomes popular in recent years. Such a technique has been used to investigate the perfusion of solid organs such as brain, liver, kidney and tumor.Early detecting rate of pulmonary masses is raising gradually with the development of digital imaging techniques, hence the diagnosis and differential diagnosis of pulmonary masses become more difficult by using conventional morphological examinations. The lung is an organ of which the first CT attenuation's increasing depends on regional perfusion after rapidly bolus injecting contrast medium. The vasculari-ty in different pulmonary masses is quite different, which offers opportunity for CT perfusion imaging. To date, there are only a few investigations about pulmonary masses perfusion study and the results are lack of confirmation and comparison. Most of the former studies are single slice located and provide only limited information. The adventof multi - slice CT allows providing more information about perfusion with its high speed and long volume coverage.PURPOSEAims to evaluate the clinical efficacy of multi - slice CT perfusion imaging in differential diagnosis of pulmonary masses.MATERIALS AND METHODSThirty-four patients (24 men, 10 women; age range, 25 -78 years; mean age, 51. 8 years) with proven pulmonary masses (21 malignant, 8 benign, 5 inflammatory) were studied.The CT perfusion scanning was performed between a conventional unenhanced examination and a contrast - enhanced examination with use of Marconi MX8000 CT scanner. Four contiguous slices that demonstrated the pulmonary mass best were selected for perfusion imaging. The CT perfusion protocol comprised 20 scans that were obtained at the single level with the following parameters; 120 KV, 220 mAs, 2.5 mm or 5 mm slice thickness, 0.5 s scan time, 1.5s cycle time. Fifty milliliters of nonionic iodinated contrast agent ( omnipaque 350mgl/ml) was administered at a rate of 5 ml/sec via an antecubital vein with a power injector. The scanning started at 11 s after the beginning of injection.All perfusion images were transferred to CT workstation for data analysis by using FUNCTIONAL CT software. Regions of interest ( ROI) were drawn over the mass and the aorta in a slice that demonstrated the mass best. Time - density curves of aorta and mass as wellas perfusion parametric maps were created automatically. The aorta peak enhancement and the pulmonary mass perfusion parameters such as perfusion value ( P) ; peak enhancement ( PE ) ; time to peak (TIP) and mean transit time (MTT) were recorded. The ratio of mass - to - aorta peak enhancement was calculated as follows: PEmass/ PEaorta x 100%.The results of the five perfusion parameters among three groups were compared using simple factor analysis. The relationships among perfusion parameters were assessed by correlation analysis. A P value less than 0.05 was considered statistically significant.RESULTSThe time - density curves were apparently different in malignant and inflammatory masses firom in benign masses. The time - density curves of malignant and inflammatory pulmonary masses increased rapidly and maintained a plateau when they reached the peak enhancement , whereas the time - density curve of benign pulmonary masses was flat with no evident increase. Compared with the inflammatory masses, in malignant masses, the growing slopes were larger, the times to peak were earlier and the peak enhancements were higher. Precontrast attenuation of malignant masses and inflammatory masses was higher than that of benign masses.Perfusion values, peak enhancements and mass - to - aorta peak enhancement ratios of maligna...
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