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 Science and Technology.
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L-[methyl-11-C] methionine(11C-MET) is a tracer for PET that can be use to assess metabolism of amino acid in tumor cells. The purpose of this study is to assess the ability of MET-PET to detect choroidal melanoma lesion and the feasibility of MET-PET as an evaluation method of therapeutic effect in carbon ion beam radiotherapy(CIRT).
We studied cansecutive 24 patients with the choroidal melignant melanoma who had been referred to our hospital carbon ion beam therapy in 2001-2003. 9 patients were female and 15 patients were male. The average patienrt age was 55.5 years(range 25 to 82). All patients were treated with carbon ion beam from the Heavy Ion Medical Accelerator in Chiba(HIMAC) in our hospital.
All patients underwent at least three MET-PET scans before therapy, one month after therapy(averaged 31.2days, ranged from 17 to 43 days) and about 6 months(averaged 6.6 months, ranged from 5 to 8 months) after therapy. First, we evaluated the uptake of primary lesion visually. Second, we evaluated the uptake in the choroidal melanoma lesion semiquantitatively on the basis of the Tumor-To-Brain Ratio(TBR), which was calculated by dividing the mean tradioactivity of the tumor ROI by that of the bilateral cerebellum(or occipital lobe) ROI.
All choroidal lesions were positive(100%) on the static image of 11C-MET-PET. The TBR averaged 1.88( 0.65 SD), ranged 0.63 to 3.17. There was no correlatiton between TBR and tumor size(R2=0.25). MET was accumulated in all cases of choroidal melanoma and is considered to be a usefull tracer to detect choroidal melanoma. MET-PET at six months and later of CIRT is considered to reflect the therapeutic response more sharply than the measurement of tumor size on MRI. It is suggested that there is the risk of recurrence or regrowth if the uptake at 12 months after CIRT is not decreased enough. MET-PET provides us with another information about tumor metabolism and may be an alternative method to evaluate the effect of radiotherapy, in addition to the measurement of tumor size.
眼窩原発悪性黒色腫のC-11メチオニンPETによる画像診断と治療効果判定法の研究
