Patent Number: 
Section: claims

1. A radiation therapy delivery system comprising:a gantry;a patient fixation device configured to secure a patient with respect to the patient fixation device;a movable patient positioner connected to the patient fixation device so as to position the patient fixation device along translational and rotational axes;a radiation therapy nozzle connected to the gantry and adapted to selectively deliver radiation therapy along a beam axis;a plurality of external measurement devices which obtain position measurements of at least the patient fixation device and the nozzle with respect to a substantially fixed frame of reference; anda controller which receives the relative position measurements of at least the patient fixation device and the nozzle and provides control signals to the patient positioner to position the patient in a desired orientation with respect to the beam axis. 2. The system of claim 1, wherein the external measurement devices obtain optical images of at least the patient fixation device and the nozzle to obtain the relative position measurements. 3. The system of claim 1, further comprising a plurality of markers fixed to at least the patient fixation device and the nozzle wherein the external measurement devices obtain position measurements of the markers. 4. The system of claim 1, further comprising at least one local position feedback device in operative communication with at least one of the gantry and patient positioner wherein the at least one local position feedback device provides position data to the controller indicative of the relative position of the at least one of the gantry and patient positioner. 5. The system of claim 1, wherein the system further comprises a patient imaging system which obtains an image of the patient and determines the relative location of a patient target isocenter with respect to the nozzle. 6. The system of claim 5, wherein the system positions the patient in an initial position and, after imaging the patient, determines a correction vector and provides control signals to move the patient positioner and the patient target isocenter into a desired patient pose with respect to the nozzle. 7. The system of claim 5, wherein the patient imaging system comprises at least one x-ray source and at least one solid state x-ray imager. 8. The system of claim 5, wherein the patient imaging system is movable in and out of the beam axis. 9. The system of claim 1, wherein the nozzle is interconnected to the gantry so as to be revolvable about a gantry isocenter. 10. The system of claim 1, wherein the controller determines an orientation and position difference vector in the substantially fixed frame of reference and transforms the difference vector into at least one correction vector in a second frame of reference to position the patient in the desired pose with respect to the beam axis. 11. A patient positioning system for a radiation therapy system having a plurality of components at least some of which are subject to uncontrolled movement, the positioning system comprising:a plurality of external measurement devices arranged to obtain position measurements of the plurality of components with respect to a substantially fixed frame of reference;a movable patient support configured to support a patient substantially fixed in position with respect to the patient support and to controllably position the patient in multiple translational and rotational axes; anda controller receiving patient position information from the plurality of external measurement devices and configured to provide translation and rotation movement commands to the movable patient support to align the patient in a desired pose such that the positioning system compensates for uncontrolled movement of the plurality of components. 12. The positioning system of claim 11, wherein aligning the patient in the desired pose comprises aligning the patient support with respect to a beam delivery aiming point to which the radiation therapy system directs a radiation beam. 13. The positioning system of claim 12, further comprising a patient imager system which obtains an image of the patient and a target iso-center, wherein the positioning system determines the position of the target iso-center and aligns the target iso-center with the beam delivery aiming point. 14. The positioning system of claim 11, wherein at least one of the components subject to uncontrolled movement is also actively controllable and wherein the positioning system provides a feedback function to align the patient in the desired pose by providing control signals to position the at least one actively controllable component. 15. The positioning system of claim 11, further comprising a plurality of markers fixed to selected points of the plurality of the components subject to uncontrolled movement and wherein the external measurement devices obtain multiple position measurements of the markers so as to provide a more accurate measurement of a given marker's location than provided by a single measurement. 16. A method of registering and positioning a patient for delivery of therapy with a system having a plurality of components, wherein at least certain of the components, including a patient positioner and a therapy nozzle, are subject to uncontrolled movement, the method comprising the steps of:positioning a patient in an initial treatment pose with the patient positioner;externally measuring the location of selected monuments of the plurality of components with respect to a substantially fixed frame of reference so as to define the initial treatment pose in the substantially fixed frame of reference;determining a difference vector between the measured initial patient pose and a desired patient pose; andproviding movement commands to the patient positioner to bring the patient to the desired patient pose. 17. The method of claim 16, wherein externally measuring the location of the selected points of the plurality of components comprises employing a plurality of cameras to obtain optical images of the plurality of components. 18. The method of claim 16, wherein providing the movement commands comprises transforming the difference vector in the substantially fixed frame of reference into a corresponding movement vector for the patient positioner in a second frame of reference. 19. The method of claim 16, further comprising the step of obtaining a radiographic image of the patient and determining the difference vector based at least partially on the patient image. 20. The method of claim 19, wherein obtaining the radiographic image comprises the steps of:positioning an x-ray source and an x-ray imager generally along a therapy beam axis with the patient interposed therebetween;exposing the patient and the x-ray imager via the x-ray source; andremoving the x-ray source and imager from the therapy beam axis.