A new water calorimeter for modern radiotherapy


This new primary standard will definitely contribute to the safe introduction of future radiotherapy techniques”. This quote comes from our colleague Leon de Prez, who is defending his PhD Thesis on Thursday 26 September 2019 at Utrecht University. Leon has been working in dosimetry for nearly twenty years and in the last two years was involved in a close collaboration between the University Medical Centre Utrecht and VSL. This collaboration focussed on the development and international acceptance of a new primary standard for dosimetry, primarily on two key improvements: developing a standard which is insensitive to magnetic fields and which is transportable, for use on-site.

During radiotherapy, the location of the tumor is first determined with a CT or MRI scanner. The tumor is subsequently irradiated with a high dose of ionizing radiation using a medical linear accelerator. The more accurate the positioning of the tumor and the more well-measured the dosage of the irradiation, the more effective the treatment and the smaller the side effects. In recent research, the University Medical Centre Utrecht succeeded in combining an MRI scanner with a medical linear accelerator with, a so-called MRI-linac. This enables a simultaneous, very accurate, tumor position and treatment. Unfortunately, the high magnetic field of the MRI scanner has an impact on the distribution of the radiation dose in the tumor, and current calibration of the radiation equipment and measuring instruments is also strongly influenced by the magnetic field.

The eye-catching result of the collaboration between the University Medical Centre Utrecht and VSL is a new primary standard for dosimetry, in the form of a water calorimeter, which is able to measure accurately under these conditions. The water calorimeter has been shown to perform at the highest international level as the Dutch national standard. It allows for measurement of the radiation "absorbed-dose" with the highest accuracy in the MRI-linac, primarily because it is insensitive to magnetic fields. Moreover, the water calorimeter is transportable, enabling calibration  on-site at radiotherapy cancer treatment centres and paving the way towards new radiotherapy treatments in other medical fields .

We are proud of this development, which we feel will be setting a new standard in dosimetry, not just for radiotherapy, but in other applications as well. We are proud as well of Leon for reaching this personal milestone and of our colleague Jacco de Pooter who takes part in Leon’s committee as one of his advisors.

Reference: L.A. de Prez (2019), A new water calorimeter for modern radiotherapy. PhD Thesis, Utrecht University, ISBN 978-94-6375-470-5.

Should you have questions on the scientific work laid down in this thesis, please contact Leon at ldprez@vsl.nl. For inquiries on calibrations using our water calorimeter, please contact our sales department at vsl@vsl.nl.