IMG-19

PET coincidence rate

R = 2 ε² A e^{−μd}. True coincidences through a pair of detectors.

Reading speed

PETPET coincidence

Governing equation

R=2\varepsilon^{2}A e^{-\mu d}

where

A: Activity (MBq)
\varepsilon: Detector efficiency (—)
\mu: Attenuation μ (1/cm)
d: Path through patient (cm)
R: True coincidence rate (kcps)

Lecture brief

Historical brief

Larmor precession, CT Beer projections, SNR and Nyquist sampling are why MRI and CT images exist as numbers. The lab computes frequency, dose and resolution limits. This sheet (IMG-19 — PET coincidence rate) is the form associated with PET coincidence. Working symbols: $A$ , $\varepsilon$ , $\mu$ , $d$ $\rightarrow$ $R$ . A 511 keV pair. Randoms grow as singles² × 2τ. Scatter fraction is the other contaminant.

Purpose

Purpose: compute

R

from

A

\varepsilon

\mu

d

in Medical imaging via

R=2\varepsilon^{2}A e^{-\mu d}

R = 2 ε² A e^{−μd}. True coincidences through a pair of detectors. Use it when a real medical imaging question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

A = 200.000\,\mathrm{MBq}

\varepsilon = 0.150\,\mathrm{—}

\mu = 0.096\,\mathrm{1/cm}

d = 25.000\,\mathrm{cm}

, the governing relation

R=2\varepsilon^{2}A e^{-\mu d}

yields

R = 0.82\,\mathrm{kcps}

. Two opposed crystals and a line of response. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Activity A200 MBqDetector efficiency \varepsilon0.15 —Attenuation μ \mu0.096 1/cmPath through patient d25 cm

Outputs

True coincidence rate R0.82 kcps

Reading speed

Watch on YouTube

Free library

Full library

Free PDF / open book

YouTube channels

00:0 / 00:08

Narration of this film

Two opposed crystals and a line of response.

A 511 keV pair. Randoms grow as singles² × 2τ. Scatter fraction is the other contaminant.

Reading speed

Watch on YouTube