Small field intensity modulated radiation therapy machine
A small field radiation therapy machine having an aperture diameter of 30 cm or less provides improved ray definition for specialized treatment of portions of the human body such as head a breast.
1. A small field radiation therapy machine comprising:
a radiation source providing a radiation beam directed along a beam axis from a radiation origin;
a support rotatably guiding the radiation origin to be constrained within a rotation plane about a rotation axis, so that the beam axis is directed across a rotation axis and the radiation origin is separated from the rotation axis by no more than 60 cm; and
a beam modulator independently controlling the radiation fluence of multiple rays within the radiation beam.
2. The small field radiation therapy machine of claim 1 further including a patient support providing an opening extending into the rotation plane and sized for admission of a body member of a patient.
3. The small field radiation therapy machine of claim 2 wherein the body member is a human head.
4. The small field radiation therapy machine of claim 3 wherein the rotation plane is substantially vertical.
5. The small field radiation therapy machine of claim 3 further including a table for supporting the patient in a horizontal position with the opening of the patient support attached at one end of the table.
6. The small field radiation therapy machine of claim 2 wherein the body member is a human breast.
7. The small field radiation therapy machine of claim 6 wherein the rotation plane is substantially horizontal.
8. The small field radiation therapy machine of claim 6 further including a table for supporting a patient in a horizontal position with one breast passing downward through an opening in the table providing the patient support.
9. The small field radiation therapy machine of claim 1 wherein the beam modulator is a series of bi-stable shutters blocking or passing rays of the beam to control the fluence for the rays.
10. The small field radiation therapy machine of claim 1 wherein the support includes a bearing providing a race having a diameter greater than 60 cm.
11. The small field radiation therapy machine of claim 1 wherein the beam modulator provides for at least 16 independently modulated rays.
12. The small field radiation therapy machine of claim 1 wherein the beam modulator provides or independently modulated rays having a width at the rotation axis measured along the rotation plane of no more than 0.6 cm.
13. The small field radiation therapy machine of claim 1 wherein the beam axis is a centerline of the beam and is tipped with respect to the rotation plane.
14. The small field radiation therapy machine of claim 1 wherein the radiation source is a linear accelerator providing static portion arranged to accelerate electrons along the rotation axis and a rotating coupling to a wave guide rotating with the support.
15. The small field radiation therapy machine of claim 1 wherein the support provides a radiation shield extending along the radiation beam to one side of the radiation beam adjacent to a patient.
16. The small field radiation therapy machine of claim 1 including a radiation shield blocking radiation from the radiation source to a chest wall of a patient.
17. The small field radiation therapy machine of claim 1 wherein the radiation source provides a beam energy of not more than 5 MV.
18. The small field radiation therapy machine of claim 1 wherein the radiation source is a radioactive isotope.