Measurement of 99mTc gamma-spectrum

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This exercise will teach you to use a NaI-detector to take a spectrum of the γ from 99mTc. You learn to analyse the sectrum to determine the amount of 99mTc in the sample.

Remember gloves, glasses and lab-coat. If there is some spillage on the gloves control them and immediately change them . Contaminated gloves goes in the designated waste bucket for solid active waste.

Extract 0.5 mL of 99mTc from the solution you received from the supervisor with an automatic pipette and transfer it to a 20 mL glass vial and put on the lid. Throw away the pipette tip in the designated waste bucket for solid radioactive waste.

Control the outside of the glass vial by drying it with some paper then measure the paper for contamination with the hand held detector.

When you are certain that the glass vial is not contaminated on the outside you can take it to the counting room. The supervisor will show you how you use the NaI detector and the γ spectroscopy analytical program Maestro.

Set the counter to 180 seconds to measure the background ( don't put your glass vial infront of the detector) print out the background spectrum.

Delete the background spectrum and put your sample of 99mTc in front of the counter. Take a new spectrum of your sample set it to count for 180 seconds, when it is done print out the spectrum. The Tc top is marked with red, if it not marked the tops should be around 322 keV. Press the left mouse button on the top and you will receive data on it. Number of counts, N, in the top (“Net Area”): ….............................
Total number of counts, Ntot, in the marked area(“gross area”):.................
live time : …........................sec
count rate, R=N/t: …..................sec
energy of γ -gamma top ................ keV
will the background give false counts in the 99mTc-top? (ask counsellor) Explain why/why not with a sketch: