A patient was injected with ¹³¹I on Monday at 10:00 AM.On Tuesday at 10:00 AM, the thyroid probe was placed over the thyroid and produced 100,000 counts.On Thursday at 10:00 AM, the probe showed 25,000 counts.What is the effective half-life in this patient's thyroid?

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Quizplus · Accepted Answer

Typically the patient's organ excretes the radiopharmaceutical with some biologic half-life t_P while the radioactivity also decays physically with a physical half-life that is denoted as t_P.The counts observed by the gamma camera follow an exponential decay law based on the effective half-life t_E, where: 11ea6816_3f1f_5a5e_b611_55cbff154c7a_TB6242_11 or, in a format that is much easier for calculation purposes, 11ea6816_3f1f_5a5f_b611_23a5a31faa6b_TB6242_11 .The effective half-life is always less than or equal to the smaller of t_P or t_B.

A Patient Was Injected with 131I on Monday at 10:00

A Patient Was Injected with ¹³¹I on Monday at 10:00