IMG-22

Dose–area product

DAP = K × A. Inverse-square invariant kerma–area product.

Reading speed

FluoroscopyDAP / KAP

Governing equation

\mathrm{DAP}=K\,A

$A \in \left[20, 800\right]$

where

K: Air kerma (mGy)
A: Field area (cm²)
DAP: Dose–area product (Gy·cm²)

The figure, part by part

Each numbered marker wears the color of its card. Hover a card to light the marker. Tap a marker to jump to that card. The slider walks a red point along the curve; Animate drawing traces it like a pen.

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①

Governing law — red

\mathrm{DAP}=K\,A

$A \in \left[20, 800\right]$

$A = 20$ $DAP = 0.1$

Along the curve

②

Domain of the variable — blue

A_{\min} = 20,\quad A_{\max} = 800

$A \in \left[20, 800\right]$

$A = 20$ $A = 20$

Along the curve

③

Response curve — green

\mathrm{DAP}=K\,A

$A \in \left[20, 800\right]$

$A = 20$ $DAP = 0.1$

Along the curve

④

Rate of change — amber

\frac{\mathrm{d}DAP}{\mathrm{d}A}

$A \in \left[20, 800\right]$

$A = 24.91$ $DAP^{\prime} = 0.005$

Along the curve

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-22 — Dose–area product) is the form associated with DAP / KAP. Working symbols: $K$ , $A$ $\rightarrow$ $DAP$ . Effective dose ≈ DAP × conversion (e.g. 0.2 mSv/(Gy·cm²) for abdomen). Skin dose is not DAP.

Purpose

Purpose: compute

DAP

from

K

A

in Medical imaging via

\mathrm{DAP}=K\,A

DAP = K × A. Inverse-square invariant kerma–area product. 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

K = 5.000\,\mathrm{mGy}

A = 200.000\,\mathrm{cm^{2}}

, the governing relation

\mathrm{DAP}=K\,A

yields

DAP = 1.000\,\mathrm{Gy·cm^{2}}

. A field, an air-kerma, a product. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Air kerma K5 mGyField area A200 cm²

Outputs

Dose–area product DAP1.000 Gy·cm²

Reading speed

Watch on YouTube

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Narration of this film

A field, an air-kerma, a product.

Effective dose ≈ DAP × conversion (e.g. 0.2 mSv/(Gy·cm²) for abdomen). Skin dose is not DAP.

Reading speed

Watch on YouTube