RPR-14

Head leakage

Ḣ_L = f Ḋ_iso (d_iso/d)². Leakage shall not exceed 0.1 % of primary at 1 m.

Reading speed

LeakageIEC 60601-2-1NCRP 151

Governing equation

\dot H_L=f\dot D_{\mathrm{iso}}(d_{\mathrm{iso}}/d)^{2}

where

\dot D_{iso}: Isocentre output (Gy/h)
f: Leakage fraction f (—)
d_{iso}: Isocentre distance (m)
d: Distance to point (m)
\dot H_L: Leakage dose rate (mSv/h)

Lecture brief

Historical brief

Inverse-square, half-value layer, ICRP weighting and ALARA are the protection craft since the 1920s commissions. The lab computes transmission, equivalent dose and a shielding snapshot. This sheet (RPR-14 — Head leakage) is the form associated with IEC 60601-2-1 · NCRP 151. Working symbols: $\dot D_{iso}$ , $f$ , $d_{iso}$ , $d$ $\rightarrow$ $\dot H_L$ . IEC: average leakage ≤ 0.1 %, maximum ≤ 0.2 % of the useful beam at 1 m. IMRT multiplies leakage workload by the MU ratio.

Purpose

Purpose: compute

\dot H_L

from

\dot D_{iso}

f

d_{iso}

d

in Radiation protection via

\dot H_L=f\dot D_{\mathrm{iso}}(d_{\mathrm{iso}}/d)^{2}

Ḣ_L = f Ḋ_iso (d_iso/d)². Leakage shall not exceed 0.1 % of primary at 1 m. Use it when a real radiation protection question must be answered in SI before a code check.

Live realistic example

In symbols

Live case. Given

\dot D_{iso} = 4.000\,\mathrm{Gy/h}

f = 0.001\,\mathrm{—}

d_{iso} = 1.000\,\mathrm{m}

d = 3.000\,\mathrm{m}

, the governing relation

\dot H_L=f\dot D_{\mathrm{iso}}(d_{\mathrm{iso}}/d)^{2}

yields

\dot H_L = 0.444\,\mathrm{mSv/h}

. A shielded head, isotropic leakage, inverse-square spheres. Move a slider: the numbers are this situation, not a canned story.

Calculator

Inputs

Isocentre output \dot D_{iso}4 Gy/hLeakage fraction f f0.001 —Isocentre distance d_{iso}1 mDistance to point d3 m

Outputs

Leakage dose rate \dot H_L0.444 mSv/h

Reading speed

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Narration of this film

A shielded head, isotropic leakage, inverse-square spheres.

IEC: average leakage ≤ 0.1 %, maximum ≤ 0.2 % of the useful beam at 1 m. IMRT multiplies leakage workload by the MU ratio.

Reading speed

Watch on YouTube