The Value Of Tc-somatostatin Receptor Imaging And Spiral CT In The Evaluation Of The Pulmonary Nodules

Objective:To compare the value of the diagnosis of the pulmonary nodules with somatostatin receptor imaging and spiral computed tomography and to estimate the value of the diagnosis of the pulmonary nodules with adopting the two methods at the same time.Methods:29 cases of pulmonary nodules include 19 men and 10 women.The diameter range of the focuses are from 0.8cm to 4.0cm.SSTR imaging: ⁹⁹Tc^m-somatostatin was synthesized by Amercian Novartis company.The imaging apparatus was the double head detector of GE company HAWKEYE.patients drank more times after they were injected ⁹⁹Tc^m- somatostatin,static imagings were collected at 1,4,5 hour, traverse imagings in 4-6 hours after injection with the matrix 128×128,45s per frame.The fused imagings of nuclide and CT was obtained with OSEM software.CT imaging:Patients were trained how to breathe normally and hold breathing with supine position before examining. Scanning was performed when patients breathed normally and held breath in Toshiba Asteion spiral CT.Regular scanning range was from lung apex to the bottom of costophrenic angle which was more deep.CT imagings were acquired with slice thickness 10mm,120kV, 180mA,pitch 1.0,0.75s per circle.After nodules were founded, thin layer scanning was performed with slice thickness 3mm,120kV, 150mA,pitch 1.0,0.75s per circle.Enhanced scanning was achieved with high pressure injector,100ml Omnipaque was injected with the rate of 3ml per second by elbow vein,images were obtained at 25s after injection.The visual qualitative analysis of SSTR imaging was carried through by two nuclear medicine specialists with blindness.The quantitative ananlysis was clmpleted by calculating the radioactivity ratio of tumor and normal tissues.Two CT specialists evaluated together the images of unenhancement and enhancement without learning the pathologic results.They estimated the focus property after discussion and contrasted with pathologic outcome.Results:29 pulmonary nodels included 18 malign nodules,there were 9 squama cancer,6 adenocarcinoma,2 small cell cancer,1 big cell cancer.11 benign nodules included 5 tubercle,4 inflammtory pseudotumor and 2 uncertain tissue origin.Malign nodules were manifested by more radioactivity, benign nodules had no or less radioactivity.The difference of the ratio between malign and benign nodules had significant meaning.The sensitivity and the specificity of diagnosing pulmonary nodules with somatostatin receptor imaging were 88.9% and 72.7% separately. In spiral CT images the characteristics of lung cancer consisted of the sign of deep lobulation,short and thin skin needling,pleura excavation,cavern with partial center, minute calcification and physalis.The focus density of unenhancement CT was even,the foci become even or uneven intensification. The characteristics of tuberculoma were composed of smooth borderline,long and thick skin needling,thin wall cavity and central calcification, The focus density of unenhancement CT was even,the foci had no or marginal enhancement.Inflammtory persudotumor had lubricous brim and had no signs of cavity, calcification,skin needling or lobulation.The focus edge density was less than central portion in unenhancement,but had even or uneven intensification. The sensitivity and the specificity of diagnosing pulmonary nodules with CT were 77.8% and 63.6% separately.If malign nodule was diagnosed when either of somatostatin receptor imaging and CT was positive,the sensitivity and the specificity of diagnosing pulmonary nodules were 94.4% and 54.5%. If malign nodule was diagnosed when both of somatostatin receptor imaging and CT were positive,the sensitivity and the specificity of diagnosing pulmonary nodules were 72.2% and 81.8%.Conclusion:The sensitivity and the specificity of diagnosing pulmonary nodules with somatostatin receptor imaging were more than CT, but there had no significance between them.The single positive method had more sensitivity and less specificity, so had little value in clinic.The double positive method might improve the diagnosis specificity, somatostatin receptor imaging had preferable importance when CT had difficulty in determining the characterization of pulmonary nodules in practice.