Trial Information

Investigating the Feasibility of Using Real-time Cine-MRI for Treating Moving and Deforming Tumors

Accurate dose delivery remains one of the weakest aspects of radiotherapy, especially in the
case of thoracic and abdominal tumors, where significant patient motion occurs during dose
delivery (intrafraction motion). Such motion results in geometric and dosimetric
uncertainties that compromise treatment quality. Effective management of intrafraction
motion is therefore key to realizing the full potential of modern image-guided radiation
therapy (IGRT). While external markers have been found to be well-correlated with internal
anatomy within an imaging session, there is no guarantee that these correlations will
continue to exist and be constant throughout the course of the therapy. In general,
implanted, radio-opaque seeds have been found to be more reliable than external markers.
However, implantation of fiducials, whether radio-opaque or electromagnetic, is necessarily
invasive and carries with it the risk of associated complications - an issue that becomes
especially important for cancer patients with weakened immune systems. Currently, MR imaging
is the only modality that is non-invasive and provides high quality volumetric information
for the whole body.

The "ideal" intrafraction motion management requires complete spatio-temporal knowledge of
the irradiated anatomy. However, to date, there is no clinical method of directly
visualizing the tumor volume during dose delivery. Most techniques rely on external or
internal surrogate markers which often provide (usually non-volumetric) information of
limited accuracy and reliability. In addition, internal markers impose significant "costs"
on the patient in terms of interventional complications and increased imaging dose. In this
work, we investigate the feasibility of using in-room, fast cine MR imaging as a
non-invasive means to provide real-time, soft-tissue-based, volumetric image guidance for
continuous monitoring of the target and surrounding anatomy. To date, there has been no
systematic investigation of the imaging requirements of an integrated MRI+linac for the
specific task of real-time radiotherapy guidance.