AbstractID: 6566 Title: MRI guided radiotherapy: MRI as position verification system
MRI is ideal for on-line position verification during radiotherapy. MRI is able to make fast
2D images of soft tissues with orientation along and perpendicular to the field axis, allowing
imaging at critical locations which are predefined during the treatment planning procedure.
This beams eye field display in the actual anatomy may greatly enhance the accuracy of the
daily irradiation. To use a MRI system for on line position verification this system must be
fully integrated with the accelerator system. Both systems must function independently but
simultaneously. A solution under investigation is a MRI system integrated with a 6MV
accelerator, both using the same isocentre.
Clinical rationale and the major engineering problems involved in the design of such an
integrated system are being investigated. Imaging studies on stationary cervical tumours and
moving lung tumours indicate useful visibility. The disturbing effect of the accelerator system
on the MRI B0-field homogeneity and vice versa the effect of MRI B0-field on the accelerator
tube is being investigated. To allow integration of both systems the isocentre collimator
distance of the accelerator is being enlarged. Our institute committed itself to the development
of such an integrated system. The results of the first design study will be presented.
Modern radiotherapy will be image guided. MRI can provide this guidance. The integration of
a MRI system with a linear accelerator will revolutionise radiotherapy.