A new diagnostic method of cancer with Positron Emission Tomography

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Objective) Hematoporphirin derivatives (HpD) accumulate in cancer tissues in preference to normal tissues and subsequent 630 nm-laser light irradiation to tumor results in tumor necrosis. Photofrin II (a kind of HpD ; Ph2) is clinically available for photodynamic therapy of cancer from April, 1996 in Japan. The aims of this study were to label an isotope which releases positron, to Ph2, to examine the tissue distribution of Ph2 in rats, and to detect tumors on the back of rats by imaging with positron emission computed tomography (PET) and Planner Imaging. Methods) ^<68>Ga was extracted from ^<68>Ge-^<68>Ga generator. ^<68>Ga was labelled to Ph2 and ^<68>Ga-labelled Ph2 (^<68>Ga-Ph2) was refined, analyzed with thin layr chromatography and high pressure liquid chromato-graphy, and fused for medication The ^<68>Ga-Ph2 was intravenously administered to rats with or without tumors. Tissue distribution of the ^<68>Ga-Ph2 was observed with PET for 6 hours and with scintillation counter for 1 … More 2 hours after administration. Amount of the ^<68>Ga-Ph2 in organs was measured quantitatively by PET.Images by PET were contrasted with those by magnetic resonance imaging. Tumors on the back of rats were imaged by PET and Planner Imaging (HPK). Results) Labelling rates of ^<68>Ga to Ph2 were 46.4(]SY.+-.])21.1%, ranging from 17.3 to 84.7%. Although the ^<68>Ga-Ph2 accumulated densely in the liver, spleen and kidney immediately after intravenous administration, its concentration in the kidney decreased rapidly, compared to those in the liver and spleen. The ^<68>Ga-Ph2 concentration in tumors increased significantly until 12 h after the administration. At 6-12 hours after administration, ^<68>Ga-Ph2 accumulated in the following organs in the order showing higher uptake : liver>spleen>kidney>tumor>blood>lung>small intestine>heart>skin. Detection rate of tumors was 100%, however, Planner Imaging (Hamamatsu Photonics) revealed images of stronger accumulation of ^<68>Ga-Ph2 in tumors than PET.In conclusion, we succeeded in labelling ^<68>Ga to Ph2. However, because half-life of ^<68>Ga is short, using the ^<68>Ga-Ph2 raised difficulties in detection of tumor and labelling ^<68>Ga to Ph2. Less