The Clinical And Experimental Study Of ¹¹C-Acetate PET/CT Imaging In Primary Brain Tumor

Purpose Firstly, to evaluate the clinic value of 11C-ACE PET/CT in diagnosing and grading of the primary brain tumor and the correlation with Ki67 compared with 18F-FDG and 11C-MET. Secondly, to compare the value of 11C-ACE and 18F-FDG PET/CT for differentiating tumor from inflammation and granulomas in rat models.Materials and methods In our clinic study, twelve patients with suspected primary brain tumor were examined with ACE and FDG PET/CT preoperatively in our center, three of them also examined with MET. Pathologic diagnosis was obtained in all cases. Twenty-eight cases with astrocytoma proved by pathology were examined with MET PET/CT as the control group. PET results were evaluated by visual and semi-quantitative analysis. The SUVmax and T/W ratio were calculated. We investigated the correlations among the tracer uptake, tumor grade, tumor type, and tumor proliferation activity(Ki67 LI).In our animal study,30 normal SD rats were randomly divided into 3 groups(n=10, in each group):groupⅠconsisted of the rats model bearing both tumors(C6 rat glioma) and turpentine oil-induced acute inflammation, groupⅡconsisted of both tumors and turpentine oil-induced chronic inflammation, groupⅢconsisted of both tumors and BCG-induced granulomas. All received 11C-ACE and 18F-FDG PET/CT examination. The lesion-to-muscle(L/M) ratios and the tumor selectivity index were calculated. Statistical analyses were performed to evaluate the significance of differences in values between the 2 types of lesions(tumor vs. turpentine-induced inflammation or tumor vs. granuloma).Results In clinic study, the sensitivities of ACE, MET and FDG were 100%,100% and 61.5%, respectively. The ACE and FDG SUV and T/W in high-grade tumors were significantly higher than that in low-grade tumors (SUVACE,3.15±0.87 vs. 1.93±0.57, P<0.05; T/WACE,4.03±1.28 vs.2.10±0.55, P<0.05; SUVFDG, 15.50±8.76 vs.6.43±2.09, P<0.05; T/WFDG,3.75±2.17 vs.1.41±0.38,P<0.05). MET T/W in high-grade tumors were significantly higher than that in low-grade tumors(5.07±1.98 vs.3.20±1.73, P<0.05), but no significant differences were observed using MET SUV. Positive correlations between ACE and FDG uptake were observed(SUV, r=0.741, P<0.05; T/W, r=0.832, P<0.05).There were significant correlations between the SUV and T/W ratios of each tracer and the Ki67, and the ACE T/W showed the best correlation with Ki67(r=0.797, P<0.05). In animal study, there was no significant difference in the level of ACE uptake (SUV and L/M) between the tumor and inflammation tissues, but the ACE uptake in the granuloma was significantly lower than that in the tumor(SUV,2.31±0.23 vs. 3.50±0.54,P<0.001; L/M,1.21±0.15 vs.1.83±0.30, P<0.001). The level of FDG uptake in the tumor was significant higher than that in the inflammation and granuloma tissues. SIACEⅢwas significantly higher than SIFDGⅢ(SI,5.96±3.64 vs. 2.52±0.79, P<0.05), SIACEⅠand SIACEⅡ, but SIACEⅠwas comparable to SIACEⅡ, SIFDGⅡwas significantly higher than SIACEⅡ(SI,5.24±4.36 vs.1.90±1.83, P<0.05), but there was no significant difference among SIFDGⅠ, SIFDGⅡ, SIFDGⅢ, the ACE uptake in the granuloma tissues was significantly lower than that in the inflammation, but there was no significant difference between acute and chronic inflammation, and there were no significant difference in the level of FDG uptake among the acute, chronic inflammation and granuloma tissues.Conclusions The sensitivity of ACE and MET was significantly higher than FDG PET/CT. Both SUV and T/W ratios of ACE and FDG enable grading of brain tumors which was superior to MET PET. The T/W ratio was found to be better than SUV for differentiating high-from low-grade brain tumors. All of the tracers appear to be useful in evaluating proliferative activity of brain tumors, especially ACE PET. ACE is a potentially useful radiotracer for brain tumors, and when we combined ACE and FDG PET, the clinic value will be increased.In our animal study, FDG showed significantly better selectivity for distinguishing tumor from chronic inflammation tissue than did ACE, but the selectivity of FDG for tumor versus acute inflammation tissue was comparable to that of ACE. ACE uptake was significantly lower in the granuloma than in the tumor, and it showed significantly better selectivity for distinguishing tumor from granuloma than did FDG. 11C-ACE PET/CT has the potential to differentiate malignant tumors from granulomatous lesions which may overcome a major drawback of 18F-FDG imaging, but 11C-ACE was not able to differentiate tumors from inflammation lesions. When we combined ACE and FDG PET, the diagnostic accuracy maybe improved.