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Mar 31, 2021
A new approach to assessing live and in situ radiation therapy doses

In collaboration with CSIC (Spain), Consuelo Guardiola (Health Physics Unit, Radiation and Life Team, IJCLab) recently filed a patent based on a micro-opto-electromechanical system (MOEMS) to measure the dose delivered to patients exposed to ionising radiation for therapeutic purposes.

 

In radiotherapy, an accurate assessment of the dose delivered to patients is fundamental. Traditionally, radiochromic films are considered the basic 2D passive detectors in the field of dose verification from tens of mGy to hundreds of Gy by determining how this dose has been absorbed as a function of depth for diagnostic instruments, such as X-ray radiography or mammography.


Due to their high spatial resolution, low energy dependence and near-equivalence in water, they are widely used for quality assurance measurements and treatment verification. However, they require post-irradiation processing that takes a minimum of 24 hours. This delay in analysis makes radiochromic films an inadequate tool for real-time, in situ daily dose assessments. In practice, when it is mandatory to provide real-time dose verification, films are supplemented by active radiation sensors such as solid-state or scintillation detectors, gas chambers, etc.

 
A new approach to assessing live and in situ radiation therapy doses

Sketch of the two modules of the optical sensing system. Left: LED light-emitting module. Center: Detector module consisting mainly of a photoresistor and 1 k? resistor. Right: Image of both assembled modules

In response to these problems, the IJCLab Health Physics Unit sought to create a new device using a different physical parameter and a new method for obtaining the dose derived from an innovative micro-opto-electro-mechanical system (MOEMS), which overcomes the limitations of processing radiochromic films by transforming a passive detector into an active sensor. The system consists of an optical sensor with light-emitting diodes and photodetectors integrated into a mechanical and electrical system. The portable system, which is configured to respond to the sensitive area to cover several centimetres, also includes a graphical user interface for direct data display. A patent was filed in March 2021.

 

Initial tests in a low-energy proton cyclotron have shown that it is feasible to use this system for in situ dose assessments. A complete active detector that integrates arrays of MOEMs and films into flexible printed circuits is being developed. This second prototype is part of a Déclic action (development devices within the CNRS) in collaboration with Nabil Karkour (Engineering Pole, Electronics Department, Analog and Microelectronics Development Service). Ultimately, this device will extend the clinical use of radiochromic films to verify the effects of radiotherapy treatments.

 
#128 - Last update : 03/31 2021

 

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