RAD-24

CPE dose–kerma link

D = K (1 − g) under charged-particle equilibrium. Radiative fraction g.

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DosimetryCPE

Governing equation

D=K(1-g)

where

K: KERMA (Gy)
g: Radiative fraction (—)
D: Dose under CPE (Gy)

Lecture brief

Historical brief

Beer attenuation, Compton (1923), Klein–Nishina, Bragg–Gray cavity and KERMA are the transport of photons and charged particles in matter. The sheets compute fluence, kerma and stopping. This sheet (RAD-24 — CPE dose–kerma link) is the form associated with CPE. Working symbols: $K$ , $g$ $\rightarrow$ $D$ . g is a few percent in tissue at MV energies, tiny at kV. Transient CPE in build-up.

Purpose

Purpose: compute

D

from

K

g

in Radiation physics via

D=K(1-g)

D = K (1 − g) under charged-particle equilibrium. Radiative fraction g. Use it when a real radiation physics question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

K = 2.000\,\mathrm{Gy}

g = 0.003\,\mathrm{—}

, the governing relation

D=K(1-g)

yields

D = 1.9940\,\mathrm{Gy}

. A kerma bar, a slightly smaller D. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

KERMA K2 GyRadiative fraction g0.003 —

Outputs

Dose under CPE D1.9940 Gy

Reading speed

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Narration of this film

A kerma bar, a slightly smaller D.

g is a few percent in tissue at MV energies, tiny at kV. Transient CPE in build-up.

Reading speed

Watch on YouTube