IMG-21

Mean glandular dose

MGD = DgN × K. Conversion from entrance air kerma.

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MammographyDance MGD

Governing equation

\mathrm{MGD}=D_{gN}K

where

D_{gN}: Conversion DgN (mGy/mGy)
K: Entrance air kerma (mGy)
MGD: Mean glandular dose (mGy)

Lecture brief

Historical brief

Larmor precession, CT Beer projections, SNR and Nyquist sampling are why MRI and CT images exist as numbers. The lab computes frequency, dose and resolution limits. This sheet (IMG-21 — Mean glandular dose) is the form associated with Dance MGD. Working symbols: $D_{gN}$ , $K$ $\rightarrow$ $MGD$ . Dance: MGD = K g c s, with g HVL, c glandularity, s spectrum. Typical MGD 1–2 mGy per view.

Purpose

Purpose: compute

MGD

from

D_{gN}

K

in Medical imaging via

\mathrm{MGD}=D_{gN}K

MGD = DgN × K. Conversion from entrance air kerma. Use it when a real medical imaging question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

D_{gN} = 0.200\,\mathrm{mGy/mGy}

K = 8.000\,\mathrm{mGy}

, the governing relation

\mathrm{MGD}=D_{gN}K

yields

MGD = 1.600\,\mathrm{mGy}

. A compressed breast and a glandular-dose bar. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Conversion DgN D_{gN}0.2 mGy/mGyEntrance air kerma K8 mGy

Outputs

Mean glandular dose MGD1.600 mGy

Reading speed

Watch on YouTube

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Narration of this film

A compressed breast and a glandular-dose bar.

Dance: MGD = K g c s, with g HVL, c glandularity, s spectrum. Typical MGD 1–2 mGy per view.

Reading speed

Watch on YouTube