IBA - Ion Beam Applications

Imaging solutions for a novel prompt gamma camera 

Trainee: Johannes Petzoldt
Supervisor: Damien Prieels

Ion therapy offers extremely high precision in beam delivery and hence demands very high accuracy to ensure that the maximum penetration depth coincides with the tumor. An online beam range verification is therefore highly desirable and would reduce the safety margins, which are currently applied in clinical practice. Prompt gamma rays are emitted along the particle track due to nuclear collisions between ions and patient tissue. Hence, they are an ideal probe to determine the particle range due to their correlation to the dose, the low attenuation inside the patient and their instantaneous emission.

The ‘slit camera’ of IBA measures the prompt gamma signal emitted by each pencil beam and allows therefore a range retrieval on a spot level. Two prototypes of the camera are used by clinical partners in the US and Europe. First patient measurements have been performed in 2015 and 2016 by the partner institutions showing the possibility to measure the proton range in patient treatment. The Fellow has developed and improved software tools to perform and test the various new treatment workflows made possible by the ‘slit camera’.

Furthermore, the Fellow has supported clinical partners in their efforts to increase the number of treatment indications that can be monitored by the camera. In this context, a trolley system was developed that enables positioning of the camera under the patient couch to allow for monitoring of abdominal and prostate treatments. The system further allows fast and highly reproducible positioning of the camera with respect to the patient and the room isocentre. This increases the quality of the measured prompt gamma data and improves the usage of the camera in the clinical workflow.

The new trolley system has been used since the end of 2018 during patient treatment at OncoRay and has already proven its benefit for prompt gamma measurements.