Re-188은 반감기가 17시간이고 진단을 위한 영상화가 가능한 감마선(155keV)을 방출하며 치료용으로 적당한 베타선(2.12MeV)을 동시에 방출하여 혈관성형술 풍선에 넣어 조사하는 접촉 베타선 방출체 치료용 방사성핵종으로 유력하다. 이 연구에서는 Re-188-DTPA를 관상동맥풍선 성형술시 풍선에 주입하는 방사성 동위원소로 쓸 수 있을지 알기 위해 우선 표지법과 풍선에서 혈관내로 샜을 때의 생체내 분포를 조사하였다. Re-188과 DTPA를 표지하는 방법을 확립하였고 표지효율은 95%, 실온과 사람 혈청에서 안정하였다. 마우스의 체내분포와 랫트와 실험견에서 얻은 신장 시간방사능곡선이 Re-188-DTPA가 신장을 통해 빠르게 제거된다는 것을 밝혔다. 이러한 결과는 Re 188-DTPA를 관상동맥의 재협착을 방지하기 위해 관상동맥풍선 성형술시 풍선에 주입하는 방사성 동위원소로 사용하여도 좋음을 시사한다.
Re-188 is useful candidate for therapeutic radionuclide because it has a physical half life of 17 hours, contains beta emissions suitable for therapy(maximum energy 2.12MeV) and emits a gamma ray that is suitable for quantitative diagnostic scanning(155keV). To use Re-188 as a radionuclide compound of angioplasty balloon radiotherapy, we investigated the labelling method and biodistribution of Re-188-DTPA We postulated that labeled Re-188-DTPA is preferable because it would be excreted via urinary system more easily than other compounds. To label Re-188 with DTPA, 1ml of 222MBq(6mCi) of Re-188 was added to DTPA solution(DTPA 20mg, $SnCl_2{cdot}2H_2O$ 10mg, pH 3.5) and boiled at $100^{circ}C$ for 120min in water bath. pH was adjusted to 5 with 2.3% sodium acetate. Labeling efficiency was measured using TLC-SG(acetone, saline). We evaluated biodistribution of Re-188-DTPA in sacrificed mice at 10 and 60 minutes after injection. We acquired images of kidneys, and drew time-activity curves in normal dogs and rats and calculated Tmax and Tl/2 in rats. The labelling efficiency was 95.7% on average. Labelling of Re-188-DTPA was.stable(90% after 5hours) in vitro at room temperature. According to time-activity curves of dogs and rats, it took 15 to 20 minutes after injection for Re-188-DTPA to be washed out through kidneys. In conclusion, Re-188-DTPA was successfully labeled, Re-188-DTPA was stable in vitro and was excreted early via kidneys in animals. We could recommend Re-188-DTPA as radionuclide of potential use in angioplasty balloon radiotherapy.
