Imaging for Physicists

Prompt Events  Single event

● single photon is counted by detector (1-10%)  True coincidence ● event derives from single positron-electron annihilation ● both photons reach tomograph without interaction  Random coincidence ● two nuclei decay at approximately the same time ● random event count rate (R ab ) between two detectors a and b :

2 ∝ ⋅ N NN R b a

2 = τ

ab

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ESTRO Teaching Course Advanced Imaging: PET – Basic Principles