Image-guided radiation therapy: emergence of MR-guided radiation treatment (MRgRT) systems

Radiation therapy has been on the march toward highly conformal and precise placement of radiation dose within the human body. Development of image-guidance systems based upon x-ray and ultrasound have advanced our capabilities to the level of a few millimeters of uncertainty in many sites. However, there are a subset of existing applications, and potentially many new applications that could be improved upon or pursued if greater targeting accuracy could be achieved. This is motivating the creation of magnetic resonance image-guided radiation treatment units (MRgRT) that either operate simultaneously or provide pre-treatment MR-based targeting capabilities. In this review, the motivation for these pursuits, an overview of recent developments, and a commentary on the challenges they face is presented.

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