NMD-31

Noise-equivalent count rate

NECR = T² / (T + S + k R). PET figure of merit versus activity.

Reading speed

PETNEMA NECR

Governing equation

\mathrm{NECR}=T^{2}/(T+S+kR)

where

T: Trues (kcps)
S: Scatter (kcps)
R: Randoms (kcps)
k: Randoms factor k (—)
NECR: NECR (kcps)

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-31 — Noise-equivalent count rate) is the form associated with NEMA NECR. Working symbols: $T$ , $S$ , $R$ , $k$ $\rightarrow$ $NECR$ . k = 1 for a noiseless randoms estimate, 2 if randoms are measured. Peak NECR sits near 10–20 kBq/ml for many scanners.

Purpose

Purpose: compute

NECR

from

T

S

R

k

in Nuclear medicine via

\mathrm{NECR}=T^{2}/(T+S+kR)

NECR = T² / (T + S + k R). PET figure of merit versus 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

T = 120.000\,\mathrm{kcps}

S = 50.000\,\mathrm{kcps}

R = 40.000\,\mathrm{kcps}

k = 2.000\,\mathrm{—}

, the governing relation

\mathrm{NECR}=T^{2}/(T+S+kR)

yields

NECR = 57.6\,\mathrm{kcps}

. Trues, scatter, randoms pouring into one ratio. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Trues T120 kcpsScatter S50 kcpsRandoms R40 kcpsRandoms factor k k2 —

Outputs

NECR NECR57.6 kcps

Reading speed

Watch on YouTube

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Narration of this film

Trues, scatter, randoms pouring into one ratio.

k = 1 for a noiseless randoms estimate, 2 if randoms are measured. Peak NECR sits near 10–20 kBq/ml for many scanners.

Reading speed

Watch on YouTube