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Related Experiment Video

Updated: Jun 6, 2026

Irradiator Commissioning and Dosimetry for Assessment of LQ α and β Parameters, Radiation Dosing Schema, and in vivo Dose Deposition

Irradiator Commissioning and Dosimetry for Assessment of LQ α and β Parameters, Radiation Dosing Schema, and in vivo Dose Deposition

Published on: March 11, 2021

Modeling silicon diode dose response factors for small photon fields.

Karin Eklund¹, Anders Ahnesjö

¹Section of Oncology, Department of Oncology, Radiology and Clinical Immunology, Uppsala University, Uppsala, Sweden.

Physics in Medicine and Biology

|November 25, 2010

Summary

This summary is machine-generated.

Accurate dosimetry in small radiotherapy fields is crucial. A new model accounts for charged particle disequilibrium, improving silicon diode accuracy to 1-2% for small fields and 0.5% for larger fields.

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Last Updated: Jun 6, 2026

Irradiator Commissioning and Dosimetry for Assessment of LQ α and β Parameters, Radiation Dosing Schema, and in vivo Dose Deposition

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Published on: March 11, 2021

Characterization of Recombination Effects in a Liquid Ionization Chamber Used for the Dosimetry of a Radiosurgical Accelerator

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Published on: May 9, 2014

Area of Science:

Medical Physics
Radiotherapy Dosimetry

Background:

Accurate dose measurement in small radiotherapy fields is essential for high-resolution photon therapy.
Silicon diodes offer high signal and small detection volumes, suitable for small fields but susceptible to response variations.
Variations in unshielded diode response in small fields arise from spectral changes and loss of lateral electron equilibrium.

Purpose of the Study:

To develop and validate a dosimetry model for silicon diodes in small radiotherapy fields.
To investigate the impact of charged particle disequilibrium on diode response.
To improve the accuracy of dose measurements in small radiation fields.

Main Methods:

A dosimetry model incorporating charged particle disequilibrium effects was developed.
Local photon spectra were calculated using fluence pencil kernels, with low and high energy components treated using different cavity theories.
Monte Carlo-derived correction factors were applied to account for electron equilibrium deviations.

Main Results:

The model achieved dose response accuracy of 1-2% for the smallest fields (0.5 × 0.5 cm²) and 0.5% for larger fields (up to 20 × 20 cm²).
Spectral variations had minimal impact on small field response.
Volume averaging and interface transient effects were identified as significant factors in non-equilibrium conditions.

Conclusions:

The developed model accurately predicts silicon diode response in small radiotherapy fields, even under non-equilibrium conditions.
Diode design should consider padding the active volume between inactive silicon layers to mitigate transient effects.
The findings contribute to more reliable dose delivery in advanced radiotherapy techniques.