Decay is not a nuisance. It is the clock of every elution, every SUV, every delayed image.
For Nuclear-medicine physicists · technologists·8 min
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You will be able to
01Decay-correct an activity across a wait.
02Say what SUV normalises, and what it assumes.
03Read a generator as secular equilibrium, not magic.
Chapter 01
The only clock that matters
A equals A-zero e to the minus lambda t. After one half-life, half remains. After two, a quarter. Every syringe you assay, every delayed PET, every leftover in the pig, lives on this curve. Forget the wait from calibration and you invent activity.
Write the calibration time on the same line as the activity.
Simulation
Radioactive decay — Change the numbers; the scene follows.
Variables
A = 261.9309 MBq
A=A0e−λt
Keep thisWrite the calibration time on the same line as the activity.
SUV is activity in a voxel, scaled by injected activity and body size, decay-corrected to scan time. It is a ratio, not a histology. Uptake time, plasma glucose, reconstruction, and partial volume all move it. Compare like with like.
Simulation
Standardized uptake value — Change the numbers; the scene follows.
Variables
SUV = 2.8 g/ml
Keep thisA SUV without uptake time is an incomplete sentence.
A molybdenum-99 generator yields technetium-99m because the parent is long and the daughter is short — secular equilibrium. Elute too soon after a previous elution and the yield is poor. That is not a faulty cow. That is the Bateman equation.
Time since last elution belongs on the worksheet.
Simulation
Mo-99 / Tc-99m generator — Change the numbers; the scene follows.
Variables
A_Tc = 13.5157 GBq
Keep thisTime since last elution belongs on the worksheet.