The present specification provides a treatment device (110, 110', 400, 400', 500, 500', 600, 600'). The treatment device (110, 110', 400, 400', 500, 500', 600, 600') may include a
magnetic resonance imaging (MRI) device (310) for acquiring MRI data about a
region of interest (ROI); and a radiotherapy device (300) for applying
therapeutic radiation to at least a portion of the ROI. The MRI device (310) may include an annular
cryostat (403, 503, 603, 700) having one or more chambers (403a, 403b, 503a, 503b, 603a, 603b), an annular structural device, and a groove (408, 508, 608) provided on the annular structural device. The radiotherapy apparatus (300) may include at least an accelerator (409, 509) and one or more collimation assemblies (412, 410, 512, 510, 612, 610).