[Biodistribution of hypoxic marker, 99mTc-HL91 (4,9-diaza-3,3,10,10-tetramethyldodecan-2,11-dione dioxime)]

99mTc-HL91 (4,9-diaza-3,3,10,10-tetramethyldodecan-2,11-dione dioxime) was developed as a hypoxic marker. Athymic mice bearing human tumors were administered with 99mTc-HL91 to evaluate it from the clinical point view. The tumor was visualized clearly 4 hours after injection. The biodistribution study revealed that 99mTc-HL91 was accumulated in the liver (tissue-to-blood ratio (T/B) = 11.5) and kidney (2.25) with higher than in the tumor (1.01). Oxygen condition of the tumor and muscle was measured by using the probe. 99mTc-HL91 uptake of tumors with PO2 (tumor-to-muscle ratio) under 0.55 was higher than that with 0.55 or higher PO2. Oxygen condition of tumors with 1.0 or higher uptake (tumor-to-blood ratio) was lower than that with the lower uptake. Autoradiography of tumor sections indicated that 99mTc-HL91 was scarcely accumulated in the necrotic and viable areas while strong radioactivity was observed in the border zone (speculated to be hypoxic condition). Our experimental results suggest that the 99mTc-HL91 scintigraphy may be useful for evaluating oxygenation status of some tumors in non-abdominal region.