Optical surface tracking camera placement for radiotherapy

A method for imaging a subject using a radiotherapy device comprising a rotatable gantry including a radiotherapy treatment device configured to deliver a therapeutic dose of radiation therapy to a subject positioned within a bore, a support surface, a controller, and a plurality of cameras, the method comprising:

• moving the support surface with the subject disposed thereon into the bore of the rotatable gantry from a side of the radiotherapy device corresponding to a front of the rotatable gantry;
• obtaining one or more images of the subject using a rear camera of the plurality of cameras, the rear camera being disposed outside of the bore and adjacent to a rear of the rotatable gantry, wherein the rear camera is a time of flight camera;
• obtaining one or more images of the subject using one or more near-bore cameras of the plurality of cameras, wherein the one or more near-bore cameras are disposed on or adjacent to the front of the rotatable gantry or disposed on or adjacent to an interior of the bore proximal to the front of the rotatable gantry, wherein the rear camera and the one or more near-bore cameras have at least partially overlapping views and are arranged to view the subject in a treatment position in which most or all of the support surface is inside of the bore;
• determining, using the controller, an average of distance measurements to a surface of the subject over a plurality of pixels of the rear camera;
• and
• using the determined average of distance measurements and location data from the one or more near-bore cameras, verifying that the subject is positioned for accurate delivery of radiotherapy treatment to one or more target regions within the subject and controlling radiation treatment device to deliver the therapeutic dose of radiation therapy to the subject positioned within the bore as verified.