Search

4'-[methyl-C-11]thiothymidine (C-11-4DST) is a novel radiopharmaceutical that can be used for tumor imaging because of its rapid incorporation into DNA as a substrate for DNA synthesis. The in vivo stability of C-11-4DST is much greater than that of natural thymidine, because of the presence of a sulfur atom in the 4'-position. Here, we evaluated the tissue kinetics and biodistribution of C-11-4DST in a rodent tumor and acute sterile inflammation model in comparison with the previously published biodistribution data of 3'-deoxy-3'-F-18-fluorothymidine (F-18-FLT), F-18-FDG, C-11-choline, C-11-methionine, and 2 sigma-receptor ligands in the same animal model. Methods: C6 tumor cells were implanted subcutaneously into the right shoulder and turpentine (0.1 mL) was injected intramuscularly into the left hind leg of male Wistar rats 11 d and 24 h, respectively, before the scanning day. The animals were anesthetized with isoflurane, and C-11-4DST (20-50 MBq) was injected intravenously. A dynamic PET scan was performed for 60 min with either the shoulder or hind leg region in the field of view. The animals were sacrificed, and a biodistribution study was performed. Results: C-11-4DST showed the highest tumor uptake (standardized uptake value, 4.93) of all radiopharmaceuticals tested. Its tumor-to-muscle concentration ratio (12.7) was similar to that of F-18-FDG (13.2). The selectivity of C-11-4DST for tumor as compared with acute inflammation was high (37.7), comparable to that of the s-ligand F-18-FE-SA5845 and much higher than that of F-18-FDG (3.5). Rapidly proliferating tissues (tumor and bone marrow) showed a steadily increasing uptake. In inflamed muscle, C-11-4DST showed relatively rapid washout, and tracer concentrations in inflamed and noninflamed muscle were not significantly different at intervals greater than 40 min. Competition of endogenous thymidine for C-11-4DST uptake in target tissues was negligible, in contrast to competition for F-18-FLT uptake. Thus, pretreatment of animals with thymidine phosphorylase was not required before PET with C-11-4DST. Conclusion: In our rodent model, 11C-4DST showed high tumor uptake (sensitivity) and high tumor selectivity. The different kinetics of C-11-4DST in rapidly proliferating and inflammatory tissue may allow distinction between tumor and acute inflammation in a clinical setting. These promising results for C-11-4DST warrant further investigation in PET studies in patients with various types of tumors.

Early diagnosis of TB is essential for community health and infection control, as well as for starting appropriate therapy for patients. Early detection of MDR is essential for the same reasons, plus the fact that currently a very high percentage of MDR patients die, especially in developing countries. Both genotypic and phenotypic methods allowing assessment of MDR tuberculosis on the bacilli isolated from fluids of infected patients are available, but these tests are lengthy (6-16 weeks) and require infected body fluids, which are not always easily assessable. Patients presenting pulmonary TB can also be culture-negative. Diagnosis of active disease in a pulmonary tuberculoma has long been problematic because the non-specific character of the disease, its changing manifestations and the slow growth of the organisms make its isolation a long and time-consuming process. Determination of pulmonary tuberculoma activity may be mandatory for optimal treatment strategy, therefore imaging techniques may be helpful in early detection. The aim of this review is to assess the role of Positron Emission Tomography (PET) imaging in the diagnosis and therapy management of TB. Although studies and data on the potential role of FDG PET in the diagnosis of tuberculosis are limited, a literature search revealed some interesting studies on this subject. Most of the studies described indicate that PET imaging, especially FDG PET as diagnostic tool, could be a noninvasive method that gives additional information about the disease status, enabling improved therapeutic management of pulmonary mycobacterial infection. Furthermore, several studies provide evidence that PET imaging could be useful in tuberculostatic therapy evaluation.

Background The purpose of this prospective study is to evaluate the possibility of C-11-methionine (Met) PET compared with F-18-fluorodeoxyglucose (FDG) PET for the detection of recurrent or metastatic disease in patients with differentiated thyroid cancer (DTC).Materials and methods Twenty patients with clinical suspicion of recurrent DTC but negative posttreatment I-131-whole body scans were included in the study. Both C-11-Met PET and F-18+DG PET were performed within 1 week. PET images were analyzed by two independent and blinded physicians using visual and standardized uptake value analysis. PET results were also correlated with radiologic and/or cytological investigations.Results Thirteen patients showed concordant findings on both PET scans: six patients showed uptake and in seven no uptake was observed. In six of the seven patients without Met and FDG uptake, additional MRI and ultrasound-guided fine needle aspiration cytology of the lymph nodes revealed inconclusive or negative results. Six patients showed discordant findings on the PET scans: in three patients uptake was only observed on the Met PET, confirmed by MRI in one. In three patients lesions were seen on the FDG PET, confirmed by computed tomography or ultrasound-guided fine needle aspiration cytology. However, those lesions were not compatible with the lesions seen on the Met PET. In general, FDG uptake appeared to be higher than Met uptake, but was not significant (P=0.075).Conclusion This study shows that imaging using radiolabeled amino acids is feasible in DTC. For now, C-11-Met PET has not proven to be superior to F-18-FDG PET in the detection of recurrent disease in DTC. Complementary uptake of Met and FDG has, however, been observed, which has to be further clarified and long-term follow-up is needed to define the true clinical value of the C-11-Met PET, and possible other amino acids tracers.

Increased glucose metabolism of inflammatory tissues is the main source of false-positive F-18-FDG PET findings in oncology. It has been suggested that radiolabeled nucleosides might be more tumor specific. Methods: To test this hypothesis, we compared the biodistribution of 3'-deoxy-3'-F-18-fluorothymidine (FLT) and F-18-FDG in Wistar rats that bore tumors (C6 rat glioma in the right shoulder) and also had sterile inflammation in the left calf muscle (induced by injection of 0.1 mL of turpentine). Twenty-four hours after turpentine injection, the rats received an intravenous bolus (30 MBq) of either F-18-FLT (n = 5) or F-18-FDG (n = 5). Pretreatment of the animals with thymidine phosphorylase (>1,000 U/kg, intravenously) before injection of F-18-FLT proved to be necessary to reduce the serum levels of endogenous thymidine and achieve satisfactory tumor uptake of radioactivity. Results: Tumor-to-muscle ratios of F-18-FDG at 2 h after injection (13.2 +/- 3.0) were higher than those of F-18-FLT (3.8 +/- 1.3). F-18-FDG showed high physiologic uptake in brain and heart, whereas F-18-FLT was avidly taken up by bone marrow. F-18-FDG accumulated in the inflamed muscle, with 4.8 +/- 1.2 times higher uptake in the affected thigh than in the contralateral healthy thigh, in contrast to F-18-FLT, for which this ratio was not significantly different from unity (1.3 +/- 0.4). Conclusion; In F-18-FDG PET images, both tumor and inflammation were visible, but F-18-FLT PET showed only the tumor. Thus, the hypothesis that F-18-FLT has a higher tumor specificity was confirmed in our animal model.

The aims of the study were to compare the value of L-[1-C-11]tyrosine (TYR) and [F-18]fluoro-2-deoxy-D-glucose (FDG) as tumor tracers in patients with breast cancer, to investigate the correlation between quantitative values and standardized uptake values (SUVs) and to estimate the value of SUVs for the evaluation of therapy. Methods: Eleven patients with one or more malignant breast lesions and two patients with one or more benign breast tumors were studied with TYR and FDG. Doses of 300 MBq of TYR and 230 MBq of FDG were given intravenously. All PET sessions were performed using a Siemens ECAT 951/31 camera. Of 10 malignant tumors and the 3 benign lesions, glucose consumption and protein synthesis rate were quantified. All lesions were studied using SUVs based on body weight, body surface area and lean body mass, with and without correction for plasma glucose or tyrosine levels. Results: All malignant tumors were visualized with both FDG and TYR, but the visual contrast was better with FDG, Increased uptake of the tracers was seen in patients with fibrocystic tissue and complicated the visual assessment and the outlining of tumor tissue. Uptake in fibrocystic disease was more prominent with FDG than with TYR. No difference in tumor/nontumor ratio between the two tracers could be established. FDG showed a false-positive result in one benign lesion. No major differences between the SUVs as defined above were found, although the best correlation between glucose consumption and the SUV was observed when the SUV was based on body surface area and corrected for plasma glucose level (r = 0.85-0.87). The SUV based on lean body mass was found to correlate best with protein synthesis rate (r = 0.83-0.94). Conclusion: in this group of patients, TYR appears to be a better tracer than FDG for breast cancer imaging, because of lower uptake in fibrocystic disease, SUVs correlate well with quantitative values, but future studies must determine whether treatment evaluation is also reliable with SUVs.

Background The purpose of this prospective study is to evaluate the possibility of C-11-methionine (Met) PET compared with F-18-fluorodeoxyglucose (FDG) PET for the detection of recurrent or metastatic disease in patients with differentiated thyroid cancer (DTC). Materials and methods Twenty patients with clinical suspicion of recurrent DTC but negative posttreatment I-131-whole body scans were included in the study. Both C-11-Met PET and F-18+DG PET were performed within 1 week. PET images were analyzed by two independent and blinded physicians using visual and standardized uptake value analysis. PET results were also correlated with radiologic and/or cytological investigations. Results Thirteen patients showed concordant findings on both PET scans: six patients showed uptake and in seven no uptake was observed. In six of the seven patients without Met and FDG uptake, additional MRI and ultrasound-guided fine needle aspiration cytology of the lymph nodes revealed inconclusive or negative results. Six patients showed discordant findings on the PET scans: in three patients uptake was only observed on the Met PET, confirmed by MRI in one. In three patients lesions were seen on the FDG PET, confirmed by computed tomography or ultrasound-guided fine needle aspiration cytology. However, those lesions were not compatible with the lesions seen on the Met PET. In general, FDG uptake appeared to be higher than Met uptake, but was not significant (P=0.075). Conclusion This study shows that imaging using radiolabeled amino acids is feasible in DTC. For now, C-11-Met PET has not proven to be superior to F-18-FDG PET in the detection of recurrent disease in DTC. Complementary uptake of Met and FDG has, however, been observed, which has to be further clarified and long-term follow-up is needed to define the true clinical value of the C-11-Met PET, and possible other amino acids tracers.

The aims of the study were to compare the value of L-[1-C-11]tyrosine (TYR) and [F-18]fluoro-2-deoxy-D-glucose (FDG) as tumor tracers in patients with breast cancer, to investigate the correlation between quantitative values and standardized uptake values (SUVs) and to estimate the value of SUVs for the evaluation of therapy. Methods: Eleven patients with one or more malignant breast lesions and two patients with one or more benign breast tumors were studied with TYR and FDG. Doses of 300 MBq of TYR and 230 MBq of FDG were given intravenously. All PET sessions were performed using a Siemens ECAT 951/31 camera. Of 10 malignant tumors and the 3 benign lesions, glucose consumption and protein synthesis rate were quantified. All lesions were studied using SUVs based on body weight, body surface area and lean body mass, with and without correction for plasma glucose or tyrosine levels. Results: All malignant tumors were visualized with both FDG and TYR, but the visual contrast was better with FDG, Increased uptake of the tracers was seen in patients with fibrocystic tissue and complicated the visual assessment and the outlining of tumor tissue. Uptake in fibrocystic disease was more prominent with FDG than with TYR. No difference in tumor/nontumor ratio between the two tracers could be established. FDG showed a false-positive result in one benign lesion. No major differences between the SUVs as defined above were found, although the best correlation between glucose consumption and the SUV was observed when the SUV was based on body surface area and corrected for plasma glucose level (r = 0.85-0.87). The SUV based on lean body mass was found to correlate best with protein synthesis rate (r = 0.83-0.94). Conclusion: in this group of patients, TYR appears to be a better tracer than FDG for breast cancer imaging, because of lower uptake in fibrocystic disease, SUVs correlate well with quantitative values, but future studies must determine whether treatment evaluation is also reliable with SUVs.

Increased glucose metabolism of inflammatory tissues is the main source of false-positive F-18-FDG PET findings in oncology. It has been suggested that radiolabeled nucleosides might be more tumor specific. Methods: To test this hypothesis, we compared the biodistribution of 3'-deoxy-3'-F-18-fluorothymidine (FLT) and F-18-FDG in Wistar rats that bore tumors (C6 rat glioma in the right shoulder) and also had sterile inflammation in the left calf muscle (induced by injection of 0.1 mL of turpentine). Twenty-four hours after turpentine injection, the rats received an intravenous bolus (30 MBq) of either F-18-FLT (n = 5) or F-18-FDG (n = 5). Pretreatment of the animals with thymidine phosphorylase (>1,000 U/kg, intravenously) before injection of F-18-FLT proved to be necessary to reduce the serum levels of endogenous thymidine and achieve satisfactory tumor uptake of radioactivity. Results: Tumor-to-muscle ratios of F-18-FDG at 2 h after injection (13.2 +/- 3.0) were higher than those of F-18-FLT (3.8 +/- 1.3). F-18-FDG showed high physiologic uptake in brain and heart, whereas F-18-FLT was avidly taken up by bone marrow. F-18-FDG accumulated in the inflamed muscle, with 4.8 +/- 1.2 times higher uptake in the affected thigh than in the contralateral healthy thigh, in contrast to F-18-FLT, for which this ratio was not significantly different from unity (1.3 +/- 0.4). Conclusion; In F-18-FDG PET images, both tumor and inflammation were visible, but F-18-FLT PET showed only the tumor. Thus, the hypothesis that F-18-FLT has a higher tumor specificity was confirmed in our animal model.