Study Of CT Diagnosis And CT Perfusion Of Parotid Tumors

【Objective】1, Analysing the CT manifestations of parotid tumors, investigate the value ofCT in differential diagnosis between benign and malignant tumors.2, Analysing the parameter difference in CT perfusion of parotid tumors,investigate the value of CT perfusion in differential diagnosis between benign andmalignant tumors.【Meterials and Methods】1,SubjectsPart One: 85 patients with parotid tumors in Nanfang Hospital were collectedduring May 2001 to March 2007.Part Two: 23 patients with parotid tumors in Nanfang Hospital underwent CTperfusion scan.2,Equipment and contrast mediumPart One:(1) Siemens Sonmatom Plus 4 scanner or GE lightspeed 16-detector rowscanner.(2) KMP810P high pressure syringe (Medrad corp.).(3) Nonionic iodinated contrast agent 300mgI/ml.Part Two: (1) GE lightspeed 16-detector row scanner.(2) High pressure syringe and contrast agent as part one.3,Examination techniquePart One:Axial scan ranged from external auditory foramen to the level ofmandibular angle, in which the scan parameters included 5mm slice thickness, pitch1.375, 120Kv and 40mA. An enhancement was done 20 seconds after 60～70mlnonionic contrast injected using the flowing rate at 2.0～2.5ml/s.Part Two: A "localizer" non-contrast CT was obtained as Part One. The range ofinterest for measuring perfusion was centered on the largest area of gross anatomicabnormality identified on the non-contrast localizing images. Four adjacent, 5-mmslices were selected at the level of the tumor. Forty milliliters of nonioniccontrast(300mgI/ml) were injected at 4ml/s. At 5 seconds into the injection, acine(continuous) acquisition was initiated using the following parameters: 120Kv,40mA, 4×5mm, 1-second rotation and 1-second interval for a duration of 104seconds. After completion of the perfusion acquisition, intravenous contrast wasadministered at 2.5ml/s and 30ml, and the routine enhancement was obtained usingthe parameters of plain scan.4,Data processing and imaging evaluationPart One: After scanning, all the primitive data was sent to GE ADW 4.2workstation for reformation. Image analysis included the size of thetumors(represented as maximum diameters in cross section), sharpness of the border,plain scan density, the enhanced values and lymph node of neck.Part Two: The perfusion data was postprocessed using commercially availablePerfusion3 software package on GE ADW 4.2 workstation. A region of interest wasplaced in the input artery, export vein and in the tumors to generate time-densitycurve by contrast enhancement. Some perfusion parameters were generated automatically, including blood flow(BF), blood volume(BY), mean transit time(MTT)and permeability surface area product(PS).5,Statistical MethodPart One: Pearson Chi-Square (x²) Test was used to compare gender, location,border, plain scan density and lymph node of neck between benign and malignanttumors. Age, max-diameter in cross section and enhanced value were compared bythe means of Inedpendent-Samples T Test. Discriminant function was established bythe variable of max-diameter, border, plain scan density and lymph node of neck.Part Two: For each of the perfusion parameters(BF, BV, MTT and PS), wecompared measurements between benign and malignant tumors. To determine astatistically significant difference between the two groups, the Independent-SamplesT Test, a parametric test was employed.SPSS13.0 software package was applied to statistical analysis in both parts ofstudy. Statistical significance level was set as a=0.05, statistically significantdifference was defined as P value less than 0.05.[Results]Part One(1) 85 patients with parotid tumors underwent CT scan, in which 65 werebenign(76.5%)and 20 were malignant(23.5%).(2) Statistically significant difference was found in age, max-diameter in crosssection, border, enhanced value and lymph node of neck between benign andmalignant tumors(P＜0.05). But no statistically significant difference was found inlocation, gender and plain scan density.(3) The discriminant function had a high coincidence of discrimination whenjudged by the variable of max-diameter, border, enhanced value and lymph node ofneck. 92.9% of original grouped tumors correctly classified(93.8% in benign tumors and 90.0% in malignant ones).Part Two(1) 23 patients with parotid tumors underwent CT perfusion exam, in which 17were benign(73.9%)and 6 were malignant(26.1%).(2) The perfusion parameters of the tumors were as follows: BF of the benigntumors(57.92±37.08 ml·min^-1·100g^-1), BV of the benign tumors(4.69±2.05 ml·100g^-1),MTT of benign tumors(5.92±3.14S), PS of benign tumors(12.52±7.03ml·min^-1·100g^-1); BF of malignant tumors(141.40±99.91 ml·min^-1·100g^-1), BV ofmalignant tumors (7.78±3.38 ml·100g^-1), MTT of malignant tumors(5.74±2.65S), PSof malignant tumors (23.00±8.95 ml·min^-1·100g^-1). Statistically significant differencewas found in BF, BV and PS compared with benign and malignant tumors.[Conclusions]Part One1,Parotid tumors have innate contrast with the fat of parotid. CT exam hashigher organism and spatial resolution, and takes less time. It should be the first pickof medical imaging examination.2,Using plain scan and enhancement, not only the position and shape of tumorscould be confirmed but also the structures surrounded and lymph node of neck can beobserved which can provide a higher diagnostic value.3,We can make a aggregate analysis of every observation index by establishinga discriminant function. Our study shows that the variables of max-diameter, border,enhanced value and lymph node of neck had better capability to distinguish betweenbenign and malignant parotid tumors. The discriminant function has a highcoincidence of discrimination when judged by these variables(93.8% in benigntumors and 90.0% in malignant ones).Part Two 1,As an organ of head and neck, parotid has a locked position and hardlyeffected by breathing which is convenient for CT perfusion study.2,CT perfusion imaging is an non-invasive functional imaging that can evaluateperfusion condition of organism. Our study shows that the perfusion index of BF,BV and PS in malignant parotid tumors are much higher than in benign tumors, thedifferences have statistical significance, which is valuable for differential diagnosis.3,We could obtain both morphology and function information of parotid tumorsby CT peffusion in one scan, and it will offer more diagnostic evidences to clinics.Therefore, CT perfusion of parotid tumors is a promising tool in clinical practice.