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Updated: May 26, 2026
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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
In aqua vivo EPID dosimetry.
Markus Wendling1, Leah N McDermott, Anton Mans
1Department of Radiation Oncology, The Netherlands Cancer Institute--Antoni van Leeuwenhoek Hospital, Plesmanlaan 121, 1066 CX Amsterdam, The Netherlands. m.wendling@amc.uva.nl
Medical Physics
|January 10, 2012
Summary
A new in aqua vivo electronic portal imaging device (EPID) dosimetry method accurately verifies lung cancer treatments. This fast dose verification technique achieves accuracy comparable to sites without significant tissue inhomogeneities.
Area of Science:
- Medical Physics
- Radiation Oncology
- Image-Guided Radiation Therapy
Background:
- In vivo dosimetry using electronic portal imaging devices (EPID) is standard for most high-energy photon cancer treatments.
- Lung cancer treatments were initially excluded due to limitations of the standard back-projection algorithm in handling tissue inhomogeneities.
- Accurate dose verification is critical for effective and safe lung cancer radiotherapy.
Purpose of the Study:
- To evaluate a novel 'in aqua vivo' EPID dosimetry method for rapid dose verification in lung cancer irradiations.
- To assess the feasibility of adapting in vivo EPID dosimetry for lung cancer patients, overcoming previous limitations.
- To compare the accuracy of the new method against conventional algorithms for Intensity-Modulated Radiation Therapy (IMRT) and Volumetric-Modulated Arc Therapy (VMAT).
Main Methods:
- The 'in aqua vivo' method reconstructs dose by converting EPID images to a water-equivalent scenario.
- Dose reconstruction involves multiplying measured EPID images by the ratio of digitally reconstructed transmission images (unit-density vs. inhomogeneous).
- Verification used 2D/3D gamma (γ) evaluation (3%, 3 mm) on phantoms and 751 IMRT and 50 VMAT lung cancer patients, comparing with conventional methods.
Main Results:
- The 'in aqua vivo' method significantly improved γ values: percentage of γ ≤1 increased from 66.2% to 93.1% (IMRT) and 43.6% to 97.5% (VMAT).
- Mean γ values decreased substantially (IMRT: 0.99 to 0.43; VMAT: 1.71 to 0.40), aligning with accepted clinical standards.
- Deviation at the isocenter reduced from 5.3% to 0.5% (VMAT) and remained within 1% (IMRT), demonstrating high accuracy.
Conclusions:
- The 'in aqua vivo' approach enables accurate in vivo EPID dosimetry for lung cancer treatments (IMRT and VMAT).
- This method achieves accuracy comparable to that of dosimetry for sites without significant tissue inhomogeneities.
- The technique offers a reliable solution for fast dose verification in lung cancer radiotherapy.
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