Quick and easy evaluation of the 3D dose distribution

Clinical presentation

Presentation by David Gensanne, Chief Medical Physicist at the Centre Henri Becquerel in Rouen, France.

The presentation focuses on the results of an study aimed to clinically validate the modelling of the Varian Halcyon X6FFF accelerator using the Delta4 Phantom+.

  • Validation of the TPS
  • Evaluation of the distribution of the delivered dose
  • Comparison between the Delta4 Phantom+ and EBT3 films.



We have met with David Gensanne, Chief Medical Physicist in Radiotherapy and Medical Physic Department at the Centre Henri Becquerel, Rouen. David Gensanne and his colleagues treat around 200 patients per week using 5 different linacs, among them a new Varian Halcyon. We asked Mr. Gensanne about the patient QA process for Halcyon, tips & tricks on how to improve the quality of analysis by using the Delta4 Phantom+, and what one shouldn´t miss when visiting Rouen in France.

You recently upgraded from the Varian Unique to the Varian Halcyon. What is your impression?

The main advantages of the Halcyon over the Unique Linac are the improvements in onboard imaging and the short treatment time. We now perform all types of treatments on Halcyon.

Why did you choose the Delta4 Phantom+ as your patient QA tool for Halcyon?

Right after the Halcyon commissioning, we wanted to quickly validate several types of irradiations and determine the dose distribution in 3D. This is what we are doing with the Delta4 Phantom+.

The objective was to evaluate in a reduced time the distribution of the delivered dose.

Delta4 Phantom has been used since 2008 in our department. For several years, it has been systematically used for patient QA during IMRT or VMAT treatments. Approximately 1,000 QA were carried out during this period. Thus, when the Halcyon was installed in our department, we wanted to test its performance with the Delta4 Phantom+ for different treatment conditions. The objective was to evaluate in a reduced time the distribution of the delivered dose. The same evaluation using films would have required a longer time.

What features were important when considering the QA solution for Halcyon?

Delta4 on a Halcyon bore

The Delta4 Phantom+ geometry is well suited for Halcyon treatments that deliver coplanar beams. The evaluation of the 3D dose distribution is one of the advantages of Delta4 Phantom+. In addition, it is easy to use and the real-time dose assessment limits the time spent on quality assurance. We will continue to use the Delta4 Phantom+ to validate new treatments or new ballistics on Halcyon.

Do you have any tips and tricks for improving your patient QA for the Halcyon?

The position of the Delta4 Phantom+ in the Halcyon can be adjusted by the CBCT KV, which improves the quality of analysis.

Rouen is described as the vibrant, historic and cultural capital of Normandy. What do you think a visitor should not miss when visiting Rouen?

Rouen is well known for its cathedral and the “Gros Horloge”. The Rouen Cathedral, built and rebuilt over a period of more than eight hundred years, has features from Early Gothic to late Flamboyant and Renaissance architecture. The Gros-Horloge (English: Great-Clock)  is a 14th-century astronomical clock. From the top of the belfry, there is an outstanding view of the city of Rouen and the Seine River.

Tell us about your clinic

Center Henri Becquerel The Henri Becquerel Center is one of the 18 French Cancer Centers (CLCC) of the Unicancer Group. It is a non-profit private health establishment (ESPIC). Its main missions are care, research, and teaching in cancerology. The radiotherapy department is equipped with a dedicated scanner and 5 linacs. Intensity modulation treatments currently account for about 80% of curative treatments whatever the localizations.

Around 200 patients are treated per week. The radiotherapy department and the imaging department work in close collaboration, which makes it possible to provide PET and/or MRI examinations under treatment conditions. This concept of trimodality helps physicians to improve the definition of the target volumes and to follow the tumor evolution.

A warm thank you to David Gensanne and his team for sharing the Centre Henri Becquerel experience!

Learn more about the Delta4 Phantom+

Visit the Varian Halcyon website ( external link)

Delta4 on a Halcyon bore

User experience

Validation of the beam modeling of the Halcyon

This study aims to clinically validate the beam modeling of the Halcyon X6FFF (Varian) accelerator before introducing it in the clinical workflow. Several pre-treatment verifications, including one of a double-isocenter plan, were studied with excellent results. Poster by the Centre Henri Becquerel.

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