Functional MRI for radiotherapy dose painting

Abstract

Modern radiation therapy techniques are exceptionally flexible in the deposition of radiation dose in a target volume. Complex distributions of dose can be delivered reliably, so that the tumor is exposed to a high dose, whereas nearby healthy structures can be avoided. As a result, an increase in curative dose is no longer invariably associated with an increased level of toxicity. This modern technology can be exploited further by modulating the required dose in space so as to match the variation in radiation sensitivity in the tumor. This approach is called dose painting. For dose painting to be effective, functional imaging techniques are essential to identify regions in a tumor that require a higher dose. Several techniques are available in nuclear medicine and radiology. In recent years, there has been a considerable research effort concerning the integration of magnetic resonance imaging (MRI) into the external radiotherapy workflow motivated by the superior soft tissue contrast as compared to computed tomography. In MRI, diffusion-weighted MRI reflects the cell density of tissue and thus may indicate regions with a higher tumor load. Dynamic contrast-enhanced MRI reflects permeability of the microvasculature and blood flow, correlated to the oxygenation of the tumor. These properties have impact on its radiation sensitivity. New questions must be addressed when these techniques are applied in radiation therapy: scanning in treatment position requires alternative solutions to the standard patient setup in the choice of receive coils compared to a diagnostic department. This standard positioning also facilitates repeated imaging. The geometrical accuracy of MR images is critical for high-precision radiotherapy. In particular, when multiparametric functional data are used for dose painting, quantification of functional parameters at a high spatial resolution becomes important. In this review, we will address these issues and describe clinical developments in MRI-guided dose painting.

Commissioning of a new wide-bore MRI scanner for radiotherapy planning of head and neck cancer

“…However, in future, it is expected that vendors will bring to market more dedicated RF coils that will allow the acquisition of treatment position images across a number of sites. This will allow the radiotherapy community to build on the experience of other groups that have been so far restricted by diagnostic devices [20][21][22]. In the context of the current study, the addition of an anterior chest element to the oncology coil would extend coverage of the neck lower down and therefore remedy its current shortcoming.…”

Molecular Imaging to Plan Radiotherapy and Evaluate Its Efficacy

“…Scanners with large bores are preferred to accommodate the extra equipment. Positioning for functional MRI can be more challenging, depending on the tumor site (8). For example, for head and neck cancer, personalized masks are often used to ensure reproducible positioning and immobilization, but these masks often do not fit inside standard head coils.…”

Grand challenges in biomedical physics

“…The potential role of dynamic contrast enhanced CT and MRI (DCE-CT/DCE-MRI), diffusion weighted MRI (DW-MRI), MR spectroscopy or PET imaging is still subject of intensive research (Padhani and Miles, 2010;van der Heide et al, 2012). Today, only very few research centers explore the role of functional imaging techniques in radiation oncology.…”