NMD-23

Tc-99m decay

A = A0 (1/2)^{t/6.01 h}. The workhorse 140 keV generator daughter.

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RadionuclidesTc-99m

Governing equation

A=A_0\,(1/2)^{t/6.01\,\mathrm{h}}

where

A_0: Eluted activity (MBq)
t: Time since elution (h)
A: Remaining Tc-99m (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-23 — Tc-99m decay) is the form associated with Tc-99m. Working symbols: $A_0$ , $t$ $\rightarrow$ $A$ . T½ = 6.01 h, γ 140 keV (89 %). Elute the 99Mo/99mTc generator; 99Mo T½ is 66 h.

Purpose

Purpose: compute

A

from

A_0

t

in Nuclear medicine via

A=A_0\,(1/2)^{t/6.01\,\mathrm{h}}

A = A0 (1/2)^{t/6.01 h}. The workhorse 140 keV generator daughter. 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 = 800.000\,\mathrm{MBq}

t = 4.000\,\mathrm{h}

, the governing relation

A=A_0\,(1/2)^{t/6.01\,\mathrm{h}}

yields

A = 504.4\,\mathrm{MBq}

. A decaying elution, a 6-hour clock. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Eluted activity A_0800 MBqTime since elution t4 h

Outputs

Remaining Tc-99m A504.4 MBq

Reading speed

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Narration of this film

A decaying elution, a 6-hour clock.

T½ = 6.01 h, γ 140 keV (89 %). Elute the 99Mo/99mTc generator; 99Mo T½ is 66 h.

Reading speed

Watch on YouTube