NMD-11

Gamma-camera sensitivity

S = C / (A t). Counts per second per MBq in air.

Reading speed

Gamma cameraNEMA NU-1

Governing equation

S=C/(A t)

where

C: Counts (—)
A: Activity (MBq)
t: Live time (s)
S: Sensitivity (cps/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-11 — Gamma-camera sensitivity) is the form associated with NEMA NU-1. Working symbols: $C$ , $A$ , $t$ $\rightarrow$ $S$ . LEHR collimators run ~70–100 cps/MBq. Sensitivity and resolution trade through hole geometry.

Purpose

Purpose: compute

S

from

C

A

t

in Nuclear medicine via

S=C/(A t)

S = C / (A t). Counts per second per MBq in air. 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

C = 250000.000\,\mathrm{—}

A = 20.000\,\mathrm{MBq}

t = 60.000\,\mathrm{s}

, the governing relation

S=C/(A t)

yields

S = 208.3\,\mathrm{cps/MBq}

. A flood or point source, a count total, a sensitivity. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Counts C250000 —Activity A20 MBqLive time t60 s

Outputs

Sensitivity S208.3 cps/MBq

Reading speed

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Narration of this film

A flood or point source, a count total, a sensitivity.

LEHR collimators run ~70–100 cps/MBq. Sensitivity and resolution trade through hole geometry.

Reading speed

Watch on YouTube