Systems and methods for managing motions of an anatomical region of interest of a patient during image-guided radiotherapy are disclosed. An exemplary system may include an image acquisition device, a radiotherapy device, and a processor device. The processor device may be configured to determine a primary plane of motion of the anatomical region of interest and determine a plurality of 2D slices parallel to the primary plane. The plurality of 2D slices may define a 3D volume substantially enclosing the anatomical region of interest. The processor device may also be configured to control the image acquisition device to acquire a plurality of 2D images based on the plurality of 2D slices and determine a motion of the anatomical region of interest based on at least a subset of the acquired plurality of 2D images. The processor device may be further configured to control radiation delivery based on the determined motion.