NMD-24

F-18 decay

A = A0 (1/2)^{t/109.8 min}. PET's 511 keV workhorse.

Reading speed

RadionuclidesF-18

Governing equation

A=A_0\,(1/2)^{t/109.8\,\mathrm{min}}

where

A_0: Calibrated activity (MBq)
t: Time since calibration (min)
A: Remaining F-18 (MBq)

Lecture brief

Historical brief

MIRD schema, in-vivo decay, uptake fractions and PET coincidence turned unsealed sources into organ dose. The sheets compute activity, residence and well-counter geometry. This sheet (NMD-24 — F-18 decay) is the form associated with F-18. Working symbols: $A_0$ , $t$ $\rightarrow$ $A$ . β+ 97 %, Emax 634 keV, T½ 109.8 min. FDG uptake is imaged after ~60 min, so decay is already a factor ~0.7.

Purpose

Purpose: compute

A

from

A_0

t

in Nuclear medicine via

A=A_0\,(1/2)^{t/109.8\,\mathrm{min}}

A = A0 (1/2)^{t/109.8 min}. PET's 511 keV workhorse. Use it when a real nuclear medicine question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

A_0 = 400.000\,\mathrm{MBq}

t = 60.000\,\mathrm{min}

, the governing relation

A=A_0\,(1/2)^{t/109.8\,\mathrm{min}}

yields

A = 273.9\,\mathrm{MBq}

. A cyclotron batch fading on the way to the camera. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Calibrated activity A_0400 MBqTime since calibration t60 min

Outputs

Remaining F-18 A273.9 MBq

Reading speed

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Narration of this film

A cyclotron batch fading on the way to the camera.

β+ 97 %, Emax 634 keV, T½ 109.8 min. FDG uptake is imaged after ~60 min, so decay is already a factor ~0.7.

Reading speed

Watch on YouTube