※ 引述《Leni (喔…真不知该怎麽办)》之铭言： : 最近在准备考试，有一题关於放射元素的问题，想请知道的人帮我解释 : Thyroxine labeled with I131 is administered to a patient for the : purpose of imaging the thyroid gland. The radioactive half-life : of the isotope is 8 days. The biological half-life (the time required : for half of the compound to be eliminated from the body) is 2 days. : The time at which 3/4 of the original radioactivity will no longer : be detectable in the body is closest to? : 答案是 3.2 days. : 虽然有答案在手，但我还是不太了解怎麽计算。希望有人可以帮个忙，感恩~~ T:有效半衰期 Tb: 生物半衰期 Tp:物理半衰期 1/T = 1/Tb + 1/Tp = 1/2 + 1/8 = 0.625 λ = 0.693 / T = 0.433 A = A0e^-λt => 0.25 = e^-0.433t t = 3.2 --

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