| Objectives:For the evaluation of bone metastases in patients with cancer,99Tcm-MDP bone scintigraphy is an important tool,but some limitations exist.One of these is the differential diagnosis of malignant and benign bone disease.The aim of this study was to differentiate them using 99Tcm-Citrate and 99Tcm-MDP scintigraphy.Methods:44 patients(107 lesions)with malignant or benign bone disease were studied,for which the results of 99Tcm-MDP scintigraphy were positive.99Tcm-Citrate scintigraphy was performed 2-7 days after 99Tcm-MDP scintigraphy,at a dose of 740～925MBq.Acquisition protocol:static,2-3hr,planar or SPECT images when required.Each lesion was confirmed as benign or malignant,which was independently verified,using conventional techniques (histopathology,X-ray,CT,MRI,bone scintigraphy and clinical follow up),so they were divided into two subgroups,malignant group and benign group.Benign lesions in patients with malignant disease were also evaluated and are included in benign group.(1)The 99Tcm-MDP uptake and 99Tcm-Citrate to 99Tcm-MDP RUR(lesion-to-background radioisotope uptake ratio) for a lesion was calculated.The critical point was determined using receive operating characteristic curve(ROC curve),in both groups of patients,then calculated the highest sensitivity,specificity and accuracy.(2)Two expericnced nuclear medicine physicians evaluated the images as positive or negative by visual analysis,then calculated the sensitivity,specificity and accuracy.Results:Of these,5 patients(15 lesions)were excluded because of the the difficulty to make a final diagnosis.Ultimately,92 lesions met all the criteria,including 44 benign bone disease and 48 malignant bone disease.(1)Uptaking of 99Tcm-MDP in the two groups is of the same(1.76±0.30 vs.1.80±0.32,t=0.61,P=0.545),while the mean 99Tcm-citrate/99Tcm-MDP RUR in the benign group was significantly lower than the mean in the malignant group(0.49±0.19 vs.0.70±0.20,t=5.39,P＜0.01).The critical point was determined using ROC curve in both groups of patients.The one with the highest sensitivity and specificity,0.66,was designated the critical point,where the sensitivity was 66.7%for metastases bone disease,the specificity was 87.4%for benign bone disease,and the accuracy was 76.6%.(2)For the diagnosis of bone lesions by visual analysis,the sensitivity,specificity and accuracy of this technique were 72.92%, 88.64%and 80.43%,respectively. Conclusions:99Tcm-Citrate scintigraphy combined with 99Tcm-MDP scintigraphy is a promising method to differentiate malignant from benign bone lesions seen as areas of increased activity on 99Tcm-MDP bone scintigraphy.
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