title: Comparison of 4'-[methyl-(11)C]thiothymidine ((11)C-4DST) and 3'-deoxy-3'-[(18)F]fluorothymidine ((18)F-FLT) PET/CT in human brain glioma imaging.
abstract: BACKGROUND
  3'-deoxy-3'-[(18)F]fluorothymidine ((18)F-FLT) has been used to evaluate tumor malignancy and cell proliferation in human brain gliomas. However, (18)F-FLT has several limitations in clinical use. Recently, (11)C-labeled thymidine analogue, 4'-[methyl-(11)C]thiothymidine ((11)C-4DST), became available as an in vivo cell proliferation positron emission tomography (PET) tracer. The present study was conducted to evaluate the usefulness of (11)C-4DST PET in the diagnosis of human brain gliomas by comparing with the images of (18)F-FLT PET.
  
  
  METHODS
  Twenty patients with primary and recurrent brain gliomas underwent (18)F-FLT and (11)C-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 (11)C-4DST and (18)F-FLT in the tumor was evaluated using linear regression analysis. The relationship between the individual (18)F-FLT and (11)C-4DST uptake values in the tumors was also examined.
  
  
  RESULTS
  (11)C-4DST uptake was significantly higher than that of (18)F-FLT in the normal brain. The uptake values of (11)C-4DST in the tumor were similar to those of (18)F-FLT resulting in better visualization with (18)F-FLT. No significant differences in the uptake values of (18)F-FLT and (11)C-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 (11)C-4DST (r = 0.50, P < 0.05) and (18)F-FLT (r = 0.50, P < 0.05). Significant correlations were also found between the Ki-67 labeling index and the T/B ratio of (11)C-4DST (r = 0.52, P < 0.05) and (18)F-FLT (r = 0.55, P < 0.05). A highly significant correlation was observed between the individual T/N ratio of (11)C-4DST and (18)F-FLT in the tumor (r = 0.79, P = 0.0001).
  
  
  CONCLUSIONS
  The present study demonstrates that (11)C-4DST is useful for the imaging of human brain gliomas with PET. A relatively higher background uptake of (11)C-4DST in the normal brain compared to (18)F-FLT limits the detection of low-tracer-uptake tumors. Moreover, no superiority was found in (11)C-4DST over (18)F-FLT in the evaluation of cell proliferation.
authors: Department of Neurological Surgery, Faculty of Medicine, Kagawa University, Kagawa, 761-0793 Japan.
authors: Yasunori
authors: Y
authors: Toyota
authors: Department of Neurological Surgery, Faculty of Medicine, Kagawa University, Kagawa, 761-0793 Japan.
authors: Keisuke
authors: K
authors: Miyake
authors: Department of Neurological Surgery, Faculty of Medicine, Kagawa University, Kagawa, 761-0793 Japan.
authors: Nobuyuki
authors: N
authors: Kawai
authors: Department of Neurological Surgery, Faculty of Medicine, Kagawa University, Kagawa, 761-0793 Japan.
authors: Tetsuhiro
authors: T
authors: Hatakeyama
authors: Department of Radiology, Faculty of Medicine, Kagawa University, Kagawa, 761-0793 Japan.
authors: Yuka
authors: Y
authors: Yamamoto
authors: Research Team for Neuroimaging, Tokyo Metropolitan Institute of Gerontology, Tokyo, 173-0015 Japan.
authors: Jun
authors: J
authors: Toyohara
authors: Department of Radiology, Faculty of Medicine, Kagawa University, Kagawa, 761-0793 Japan.
authors: Yoshihiro
authors: Y
authors: Nishiyama
authors: Department of Neurological Surgery, Faculty of Medicine, Kagawa University, Kagawa, 761-0793 Japan.
authors: Takashi
authors: T
authors: Tamiya
keywords: 4DST (4′-thiothymidine); Cell proliferation; FLT (fluorothymidine); Glioma; Positron emission tomography