Challenge
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Who we are
We are a team of medical physicists involved in the planning and preparation of cancer treatment by means of ionising radiation – i.e. radiotherapy.
Our task is to ensure highest levels of both safety and effectiveness of radiotherapeutic procedures. Among other things, we perform quality control tests of medical accelerators.
Motivation and challenges
In our everyday work, we have observed that there is a lack of precise devices for performing geometric tests of linear accelerators, in particular the accelerator isocenter.
Geometric calibration is vital for radiotherapy but of utmost importance for modern volumetric rotational irradiation techniques. This observation pushed us to investigate methods and tools enabling precise, independent of the tested device and quick isocenter measurement.
Methodology
A precise measurement of the position of any movable part of an accelerator can be performed in a number of ways. However, very precise measurement, one with an uncertainty level below 0.1 mm, which is necessary for isocenter measurement is hard to achieve
We therefore decided to develop a tool using photogrammetric methods, i.e. to measure the position based on registration of images.
The aim was to build a device which:
- Allows for the measurement of the actual isocenter of gantry, treatment table and collimator with an accuracy of 0.1 mm.
- Meets the requirement of traceability.
- Ensures measurement which is independent of the accelerator for which the measurement is performed.
- Is mobil, i.e. single measurement system should enable measurements on each accelerator installed in the radiotherapy department.
- Has a short measurement time, not exceeding 25 minutes.
- Is easy to use so that the training of a medical physicist does not last longer than two working days.
- Provides objective proof of measurement.
