At Amethyst, we mainly focus on radiation therapy, which is used to treat about 60% of people at some point during their cancer treatment. In some of our centres, we also offer chemotherapy, in partnership with public or private hospitals, to provide integrated patient care.
The first step of “centring” aims to obtain an anatomical representation in three dimensions of the tumour area to be irradiated and neighbouring organs to be spared. This essential step must be carried out with the utmost care so that the patient’s position during the centring scan is the same as the treatment position (the use of immobilization systems and small dots tattooed on the skin may be necessary). This stage of treatment preparation requires the use of a dedicated radiotherapy scanner, which is available to all centres of the Amethyst group. These scanners are characterised by a large field of view (to improve patient positioning comfort), millimetre spatial accuracy and excellent low-contrast resolution to obtain noise-free images. In addition, reconstruction technologies based on iterative models allow visualisation of the smallest details and a reduction of artefacts generated by orthopaedic implants (especially hip prostheses in prostate cancers). Finally, the realisation of scans indexed on the different respiratory phases allowing better consideration of tumour movement (especially for chest and digestive cancers), despite an excellent quality of the scanned image performed during centring, complementary imaging (PET, MRI, etc.) may be necessary to determine the target volumes to be irradiated. Fusion, which consists of matching several images, is then necessary (multi-modality imaging). Strong collaborations with medical imaging services allow Amethyst cancer centres to obtain the different imaging modalities needed to prepare for treatment.
Implementation of the treatment planing system (TPS)
When the target volumes are determined by the radiotherapist, the next step is to implement treatment ballistics aimed at irradiating the tumour volumes and sparing the surrounding healthy tissue. Obtaining this compromise is complex and requires software called TPS (Treatment Planning System) whose purpose is to predict using a calculation algorithm the energy, called the dose, deposited by the radiation in the treated area.
The accuracy of these algorithms is decisive for obtaining a treatment plan that achieves the therapeutic objectives and avoids miscalculations that can lead to over-dosing or under-dosing.
In order to guarantee an optimal treatment quality, the radiotherapy centres of the Amethyst group are equipped with high-precision algorithms (such as the Collapsed Cone Convolution Superposition) allowing all existing radiotherapy techniques (RC3D, IMRT, VMAT, Stereotaxis) to be carried out in complete safety.
Control of treatment plans before the first session
When the treatment plan formulated by a physicist or a dosimetrist has been validated by the radiotherapist, the final step in the treatment preparation consists of verifying that the planning performed by the TPS on a computer corresponds to the dose actually delivered. Before starting each treatment, the delivered dose distribution is measured using specific tools and is compared to the theoretical dose distribution. This quality process implemented in all radiotherapy centres of the Amethyst group ensures a perfect match between the validated treatment plan and the treatment plan delivered to the patient.
Treatments are carried out using linear accelerators that deliver high-energy particle beams (photons or electrons). The Amethyst group is equipped at the different sites with the latest-generation accelerators, such as the Trubeam (Varian®) to treat all locations with submillimetric-precision tumour targeting. These accelerators are equipped with embedded imaging systems allowing a perfect reposition of the tumour lesion at each session (this is image-guided radiation therapy: IGRT), and high-mechanical precision. They also automatically interrupt the treatment session when a significant anatomical variation is detected by the imaging system during the session (Auto-Beam Hold), ensuring maximum treatment safety.
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