Radiation therapy system and method

A radiation therapy system comprising:

• a magnetic resonance imaging (MRI) apparatus configured to acquire MRI data with respect to a region of interest (ROI), the MRI apparatus including:
• an annular cryostat including at least one outer wall and at least one inner wall coaxially around an axis of the annular cryostat, wherein the annular cryostat includes an annular concave structure formed at the at least one inner wall and having a depth along a radial direction of the annular cryostat;
• and
• a radiation therapy apparatus configured to apply therapeutic radiation to at least one portion of the ROI, the radiation therapy apparatus including:
• a linear accelerator configured to accelerate electrons in an electron beam to produce a beam of the therapeutic radiation:
• a multi-leaf collimator (MLC) accommodated in the annular concave structure of the annular cryostat and configured to control a shape of the beam of the therapeutic radiation that passes through it, wherein the linear accelerator and the MLC are separated by the annular cryostat and arranged at different sides of the annular cryostat along the radial direction of the annular cryostat.