Exercise 19.48 At 8:00 A.M., a patient receives a 56 {\ m -\\,mg}dose of {\ m I}

Question

Exercise 19.48

At 8:00 A.M., a patient receives a 56 { m -,mg}dose of { m I}-131 to obtain an image of her thyroid.

Part A

If the nuclide has a half-life of 8 days, what mass of the nuclide remains in the patient at 5:00 P.M. the next day?

Express your answer using two significant figures.

53

Exercise 19.48

At 8:00 A.M., a patient receives a 56 { m -,mg}dose of { m I}-131 to obtain an image of her thyroid.

Part A

If the nuclide has a half-life of 8 days, what mass of the nuclide remains in the patient at 5:00 P.M. the next day?

Express your answer using two significant figures.

53

Explanation / Answer

Elapsed time: 33 hours
Convert the half life to an elimination constant (k):
* k = 0.693/t½
* k = 0.693 / 192hr
* k = 0.0036 hr^-1

Formula is : Cp = Cp e^-kt
here Cp = plasma concentration at t time , Cp = initial plasma concentration, k = elimination constant and t = time.
* Cp = 56mg * e^(-0.0036 hr^-1 * 33 hr) [ here the hr cancel]
* Cp = 56mg * e^-0.1188
* Cp = 56mg * 0.887
* Cp = 55.113 mg

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