Beam-quality factors and W_air for ion dosimetry · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
Beam-quality factors and $W_{\mathrm{air}}$ for ion dosimetry
Plain
Converting a detector reading into dose in a particle beam needs the average energy spent to make one ion pair in air. Its uncertainty, especially for carbon ions, dominates the dose error.
Precise · changed · core
Revision 1: Reduce the uncertainty in the mean energy per ion pair in air $W_{\mathrm{air}}$ and in the beam-quality correction factor $k_Q$ for carbon and other ions to the level needed for a total dosimetric uncertainty below $1.5\,\mathrm{percent}$. ICRU 90 values are $W_{\mathrm{air}}$ of about $34.44\,\mathrm{eV}$ for protons (about $0.4\,\mathrm{percent}$ standard uncertainty) and $34.71\,\mathrm{eV}$ for carbon ions (about $1.5\,\mathrm{percent}$). An answer is a measured value set with reduced uncertainty.
Revision 2: Reduce the uncertainty in the mean energy per ion pair in air $W_{\mathrm{air}}$ and in the beam-quality correction factor $k_Q$ for carbon and other ions to the level needed for a total dosimetric uncertainty below $1.5\%$. ICRU 90 values are $W_{\mathrm{air}}$ of about $34.44\,\mathrm{eV}$ for protons (about $0.4\%$ standard uncertainty) and $34.71\,\mathrm{eV}$ for carbon ions (about $1.5\%$). An answer is a measured value set with reduced uncertainty.
Settled by
Calorimetric determination of $W_{\mathrm{air}}$ and $k_{Q}$ in clinical ion beams.
Kind
well-posed
Answer type
value
References
(empty)
Literature status
partially-resolved
Status note
IAEA TRS-398 Rev. 1 (2024) adopted the ICRU 90 data; for carbon ions the $W_{\mathrm{air}}$ and $k_{Q}$ terms still keep the total uncertainty near 3 percent.
Posed since
1990

Decisions