NMD-33

In-vivo decay

Physical decay of activity.

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Nuclear medicinedecay

Governing equation

A=A_0 e^{-\\lambda t}

where

A_0: A0 (MBq)
\lambda: λ (1/h)
t: t (h)
A: A (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-33 — In-vivo decay) is the form associated with decay. Working symbols: $A_0$ , $\lambda$ , $t$ $\rightarrow$ $A$ . Physical decay of activity.

Purpose

Purpose: compute

A

from

A_0

\lambda

t

in Nuclear medicine via

A=A_0 e^{-\\lambda t}

Physical decay of activity. 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}

\lambda = 0.115\,\mathrm{1/h}

t = 6.000\,\mathrm{h}

, the governing relation

A=A_0 e^{-\\lambda t}

yields

A = 200.63\,\mathrm{MBq}

. Physical decay of activity. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

A0 A_0400 MBqλ \lambda0.115 1/ht t6 h

Outputs

A A200.63 MBq

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Narration of this film

Physical decay of activity.

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