X-Tream quality assurance in synchrotron X-ray microbeam radiation therapy

Microbeam radiation therapy (MRT) is a novel irradiation technique for brain

tumours treatment currently under development at the European Synchrotron

Radiation Facility in Grenoble, France. The technique is based on the spatial

fractionation of a highly brilliant synchrotron X-ray beam into an array of

microbeams using a multi-slit collimator (MSC). After promising pre-clinical

results, veterinary trials have recently commenced requiring the need for

dedicated quality assurance (QA) procedures. The quality of MRT treatment

demands reproducible and precise spatial fractionation of the incoming

synchrotron beam. The intensity profile of the microbeams must also be quickly

and quantitatively characterized prior to each treatment for comparison with

that used for input to the dose-planning calculations. The Centre for Medical

Radiation Physics (University of Wollongong, Australia) has developed an

X-ray treatment monitoring system (X-Tream) which incorporates a highspatial-

resolution silicon strip detector (SSD) specifically designed for MRT. Inair

measurements of the horizontal profile of the intrinsic microbeam X-ray field

in order to determine the relative intensity of each microbeam are presented,

and the alignment of the MSC is also assessed. The results show that the SSD is

able to resolve individual microbeams which therefore provides invaluable QA

of the horizontal field size and microbeam number and shape. They also

demonstrate that the SSD used in the X-Tream system is very sensitive to any

small misalignment of the MSC. In order to allow as rapid QA as possible, a fast

alignment procedure of the SSD based on X-ray imaging with a low-intensity

low-energy beam has been developed and is presented in this publication.