NMD-18

Collimator resolution

Rc = d (Leff + z) / Leff. Hole diameter d, effective length Leff, distance z.

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Gamma cameraCollimator resolution

Governing equation

R_c=d\,(L_{\mathrm{eff}}+z)/L_{\mathrm{eff}}

where

d: Hole diameter (mm)
L_{eff}: Effective length (mm)
z: Source distance (mm)
R_c: Collimator FWHM (mm)

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-18 — Collimator resolution) is the form associated with Collimator resolution. Working symbols: $d$ , $L_{eff}$ , $z$ $\rightarrow$ $R_c$ . Leff = L − 2/μ accounts for septal penetration. Resolution degrades linearly with distance.

Purpose

Purpose: compute

R_c

from

d

L_{eff}

z

in Nuclear medicine via

R_c=d\,(L_{\mathrm{eff}}+z)/L_{\mathrm{eff}}

Rc = d (Leff + z) / Leff. Hole diameter d, effective length Leff, distance z. 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

d = 1.500\,\mathrm{mm}

L_{eff} = 24.000\,\mathrm{mm}

z = 100.000\,\mathrm{mm}

, the governing relation

R_c=d\,(L_{\mathrm{eff}}+z)/L_{\mathrm{eff}}

yields

R_c = 7.75\,\mathrm{mm}

. A hole looking at a point a distance z away. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Hole diameter d1.5 mmEffective length L_{eff}24 mmSource distance z100 mm

Outputs

Collimator FWHM R_c7.75 mm

Reading speed

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Narration of this film

A hole looking at a point a distance z away.

Leff = L − 2/μ accounts for septal penetration. Resolution degrades linearly with distance.

Reading speed

Watch on YouTube