Technetium-99m is used in MIBI scans, a common method of cardiac imaging. Once t

Question

Technetium-99m is used in MIBI scans, a common method of cardiac imaging. Once the Technetium-99m has been extracted from the Technetium cow, it is incorporated into the pharmaceutical Technetium Sestamibi, which distributes itself proportionately to the blood flow and thus can be used to monitor how blood is flowing through the heart. The half-life of Technetium-99m is 6.0 hours (02-2.16x10 s). A 30 mCi sample of Technetium Sestamibi is prepared. c4 points] How many nuclei of Technetium-99m are initially present in the sample? The imaging takes place roughly 15 minutes (900 s) after the initial injection of the sample d) [4 points] How many decays have occurred by this point? The Technetium Sestamibi sample spends roughly one day (24.0 hrs) in the body before it is excreted 4 points] What is the activity of the sample at this point?

Explanation / Answer

(d) 1 Ci = 8.8639 x 10^-14 moles x half life in seconds  

30 mCi = (30 x 10^-3) (8.8639 x 10^-14) (2.16 x 10^4)

= 5.744 x 10^-11 moles

nuclies= (5.744 x 10^-11)(6.022 x 10^23) = 3.46 x 10^13 nuclies. ..........Ans

(d) N = N0 2^(-t/T) = (3.46 x 10^13) 2^(-15/360)

N = 3.36 x 10^13

decay occured = N0 - N = 1 x 10^12 decay

(e) acitivity = initial activity e^(-0.692 t / half life)

Or N = N0 e^(- t / hald life)

N = 30 mCi 2^(-24/6) = 1.875 mCi
  

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