We retrospectively evaluated the usefulness of combined measurement of L-methyl-[¹¹C]methionine (MET) and 3'-deoxy-3'-[¹⁸F]fluorothymidine (FLT) positron emission tomography (PET) in the differential diagnosis between recurrent gliomas and necrotic lesions. Twenty-one patients with high-grade glioma, previously treated with surgery and radiotherapy with chemotherapy and first radiological suspicion of recurrence were enrolled. The uptake was assessed by the maximum standardized uptake value (SUVmax) and lesion-to-normal tissue count density ratio (L/N ratio). Of the 21 lesions, 15 were diagnosed recurrent gliomas and six were necrotic lesions. The average SUVmax was not significantly different between recurrent gliomas and necrotic lesions on either MET-PET or FLT-PET. The average L/N ratio of recurrent gliomas (3.36 ± 1.06) was significantly higher than that of necrotic lesions (2.18 ± 0.66) on MET-PET (p < 0.01) and the average L/N ratio of recurrent gliomas (7.01 ± 2.26) was also significantly higher than that of necrotic lesions (4.60 ± 1.23) on FLT-PET (p < 0.01). ROC curve analysis showed that the areas under the curves were high but not different between MET- and FLT-PET. PET studies using MET and FLT are useful in the differentiation of recurrent glioma from treatment-induced necrotic lesion. However, there is no complementary information in the differentiation with simultaneous measurements of MET- and FLT-PET.

Purpose: The efficiency of [¹⁸F]FDG PET/CT using volume-based indices was evaluated to assess the disease activity and response to therapy in patients with immunoglobulin G4-related disease (IgG4-RD).Methods: A total of 17 patients with IgG4-RD were examined with [¹⁸F]FDG PET/CT before and during treatment. The lesion boundary was determined using a fixed threshold of standardized uptake value (SUV) ≥ 2.5. The highest maximum SUV (SUVmax) among all affected lesions was calculated for individual patients. We summed metabolic tumor volume (MTV) and total lesion glycolysis (TLG) of each affected lesion to generate a total MTV and total TLG. PET results were compared with those of serum IgG4 and soluble interleukin-2 receptor (sIL-2R) levels.Results: The mean number of involved organs per patient was 3.8 as determined by [¹⁸F]FDG uptake. The number of involved organs, total MTV and total TLG were significantly correlated with IgG4 (P = 0.046, < 0.001, < 0.001, respectively) and sIL-2R (P < 0.001, = 0.031, 0.031, respectively). According to the clinical assessments for therapy response, all patients were classified as improved. The SUVmax, total MTV, and total TLG during therapy were all significantly lower than those before therapy (allP < 0.001).Conclusion: [¹⁸F]FDG PET/CT is valuable for assessing the extent of multi-organ involvement before therapy and monitoring subsequent therapy in patients with IgG4-RD. [¹⁸F]FDG PET/CT using volumetric indices correlated with serum IgG4 and sIL-2R levels.

Although TI-201 is highly sensitive for detecting bone and soft-tissue tumors, its uptake is not specific for malignant lesions. This study assessed the differentiation of malignant and benign lesions and evaluated the sensitivity, specificity, and accuracy of TI-201 imaging and three-phase bone scans. Forty bone and soft-tissue tumors (16 malignant and 24 benign) were evaluated. TI-201 static images were acquired 10 minutes (early) and 2 hours (delayed) after injection of the radionuclide. Within 14 days, three-phase bone scintigraphy was performed using Tc-99m HMDP with the patient in the same position. The count ratio of the lesion compared with the normal contralateral or adjacent site (L:N ratio) was measured. With TI-201 scintigraphy, mean (+/- SD) values of early and delayed L:N ratios were 3.36 +/- 1.25 and 2.88 +/- 1.20, respectively, in malignant lesions; and 1.88 +/- 1.14 and 1.48 +/- 0.76, respectively, in benign lesions. TI-201 accumulation in benign lesions was significantly less than that of malignancies on early and delayed images. However, an overlap of both ratios between malignant and benign lesions was seen. No such significance was detected on three-phase bone scintigraphy (L:N ratios of malignant and benign tumors were 2.57 +/- 1.22 and 2.24 +/- 2.11, respectively, for blood flow imaging; 2.41 +/- 0.78 and 2.26 +/- 1.54, respectively, for blood pool imaging; and 2.80 +/- 2.10 and 2.89 +/- 4.55, respectively, for bone imaging). When we assumed that the tumor was malignant when the delayed TI-201 L:N ratio exceeded the blood pool phase L:N ratio with bone scintigraphy, the sensitivity rate was 81%, specificity rate was 100%, and accuracy rate was 93%. TI-201 imaging for bone and soft-tissue tumors was better than three-phase bone scintigraphy alone but was not good enough to clearly differentiate malignant lesions from benign ones. TI-201 scintigraphy, performed in combination with three-phase bone scintigraphy, may be superior to either one of the two imaging procedures alone for bone and soft-tissue tumor diagnosis.

Background: 3′-deoxy-3′-[¹⁸F]fluorothymidine (¹⁸F-FLT) has been used to evaluate tumor malignancy and cell proliferation in human brain gliomas. However, ¹⁸F-FLT has several limitations in clinical use. Recently, ¹¹C-labeled thymidine analogue, 4′-[methyl-¹¹C]thiothymidine (¹¹C-4DST), became available as an in vivo cell proliferation positron emission tomography (PET) tracer. The present study was conducted to evaluate the usefulness of ¹¹C-4DST PET in the diagnosis of human brain gliomas by comparing with the images of ¹⁸F-FLT PET. Methods: Twenty patients with primary and recurrent brain gliomas underwent ¹⁸F-FLT and ¹¹C-4DST PET scans. The uptake values in the tumors were evaluated using the maximum standardized uptake value (SUVmax), the tumor-to-normal tissue uptake (T/N) ratio, and the tumor-to-blood uptake (T/B) ratio. These values were compared among different glioma grades. Correlation between the Ki-67 labeling index and the uptake values of ¹¹C-4DST and ¹⁸F-FLT in the tumor was evaluated using linear regression analysis. The relationship between the individual ¹⁸F-FLT and ¹¹C-4DST uptake values in the tumors was also examined. Results: ¹¹C-4DST uptake was significantly higher than that of ¹⁸F-FLT in the normal brain. The uptake values of ¹¹C-4DST in the tumor were similar to those of ¹⁸F-FLT resulting in better visualization with ¹⁸F-FLT. No significant differences in the uptake values of ¹⁸F-FLT and ¹¹C-4DST were noted among different glioma grades. Linear regression analysis showed a significant correlation between the Ki-67 labeling index and the T/N ratio of ¹¹C-4DST (r = 0.50, P < 0.05) and ¹⁸F-FLT (r = 0.50, P < 0.05). Significant correlations were also found between the Ki-67 labeling index and the T/B ratio of ¹¹C-4DST (r = 0.52, P < 0.05) and ¹⁸F-FLT (r = 0.55, P < 0.05). A highly significant correlation was observed between the individual T/N ratio of ¹¹C-4DST and ¹⁸F-FLT in the tumor (r = 0.79, P = 0.0001). Conclusions: The present study demonstrates that ¹¹C-4DST is useful for the imaging of human brain gliomas with PET. A relatively higher background uptake of ¹¹C-4DST in the normal brain compared to ¹⁸F-FLT limits the detection of low-tracer-uptake tumors. Moreover, no superiority was found in ¹¹C-4DST over ¹⁸F-FLT in the evaluation of cell proliferation.

Background: Muscle enzymes are the major noninvasive diagnostic parameters useful in polymyositis/dermatomyositis (PM/DM). Few studies have yet correlated findings on ¹⁸F-FDG PET with disease activity in patients with PM/DM. Purpose: We evaluated ¹⁸F-FDG muscle uptake in patients with PM/DM compared with non-muscular diseases and correlated the results with serum muscle enzymes. Methods: A total of 28 patients with untreated PM/DM and 28 control patients with non-muscular diseases were examined with ¹⁸F-FDG PET/CT. ¹⁸F-FDG uptake was evaluated in 9 proximal skeletal muscle regions bilaterally. The uptake was scored as follows: 0 = less than that of the mediastinal blood vessels, 1 = greater than or equal to that of the mediastinal blood vessels, and 2 = greater than or equal to that of the liver. A score 1 or 2 was considered positive. The mean and maximum standardized uptake values (SUV) were calculated in each muscle and were averaged for all muscle regions. PET findings were correlated with serum muscle enzymes. Results: ¹⁸F-FDG uptake was observed in 82% of patients with PM/DM and 7% of control patients. The number of positive regions, total score, mean SUVmean, and mean SUVmax in patients with PM/DM were significantly higher than those in the control patients (all P < 0.001). The total score of 2 was the best cut-off value that could discriminate patients with PM/DM from control patients. The total score, mean SUVmean, and mean SUVmax showed significant correlations with creatine kinase (P = 0.047, 0.002, 0.010, respectively) and aldolase (P = 0.036, 0.005, 0.038, respectively). Conclusion: ¹⁸F-FDG PET/CT using visual and SUV methods demonstrated its usefulness by discriminating PM/DM from non-muscular diseases and correlating with serum muscle enzymes in patients with PM/DM.