量研学術機関リポジトリ「QST-Repository」は、国立研究開発法人 量子科学技術研究開発機構に所属する職員等が生み出した学術成果（学会誌発表論文、学会発表、研究開発報告書、特許等）を集積しインターネット上で広く公開するサービスです。 Welcome to QST-Repository where we accumulates and discloses the academic research results(Journal Publications, Conference presentation, Research and Development Report, Patent, etc.) of the members of National Institutes for Quantum and Radiological Science and Technology.
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Recently, we developed [methyl-11C]4'-thiothymidine (11C-4DST) as an in vivo cell proliferation marker. The present study was performed to determine the safety, distribution, radiation dosimetry, and initial brain tumor imaging of 11C-4DST in humans. Methods: Multiorgan biodistribution and radiation dosimetry of 11C-4DST were assessed in 3 healthy humans, who underwent 2-h whole-body PET scanning. Radiation dosimetry was estimated from the residence times of source organs using the OLINDA program. Six brain tumor patients underwent dynamic 11C-4DST scans with arterial blood sampling. These patients were also evaluated with 11C-methionine PET on the same day (n = 4) as, or 3 wk before (n = 2), 11C-4DST PET studies. Metabolites in plasma and urine samples were analyzed by high-performance liquid chromatography. Breakdown of the blood–brain barrier in tumor tissue was confirmed by gadolinium-enhanced T1-weighted MRI. Results: There were no serious adverse events in any subjects at any time during the study period. 11C-4DST PET demonstrated selective uptake in the bone marrow, which has a high rate of proliferation. In addition, high-level uptake was also seen in the liver. The highest absorbed organ dose was in the urinary bladder wall (17.6 muGy/MBq). The estimated effective dose for 11C-4DST was 4.2 muSv/MBq. 11C-4DST showed little uptake in normal brain tissues, resulting in low background activity for imaging of brain tumors. In contrast, 11C-4DST PET demonstrated rapid uptake in aggressive tumor masses, whereas no signal of 11C-4DST was seen in clinically stable disease in which 11C-methionine uptake was high. The distribution pattern of 11C-methionine in tumor regions was not always identical to that of 11C-4DST. Analysis of plasma samples by high-performance liquid chromatography indicated that more than 60% of the radioactivity was present as unchanged 11C-4DST at 20 min. Conclusion: The initial findings of the present study in a small group of patients indicated that 11C-4DST PET is feasible for imaging of brain tumors. Dosimetry and pharmacologic safety were acceptable at the dose required for adequate PET images.
Whole-Body Distribution and Brain Tumor Imaging with 11C-4DST: a Pilot Study
