AREAL MODULATOR FOR INTENSITY MODULATED RADIATION THERAPY

• US 20080260098A1
• Filed: 02/27/2008
• Published: 10/23/2008
• Est. Priority Date: 02/27/2007
• Status: Active Grant

• Current Assignee: David C. Westerly, Jihad H. Al-Sadah, Patrick M. Hill, Thomas R. Mackie
• Original Assignee: David C. Westerly, Jihad H. Al-Sadah, Patrick M. Hill, Thomas R. Mackie
• Inventors: Mackie, Thomas R., Westerly, David C., Hill, Patrick M., Al-Sadah, Jihad H.
• Granted Patent: US 8,129,701 B2
• Time in Patent Office: Days
• US Class Current: 378/65
• CPC Class Codes: A61N 2005/1087 Ions; Protons
• CPC Class Codes: A61N 2005/1095 Elements inserted into the radiation path within the system, e.g. filters or wedges
• CPC Class Codes: A61N 5/1042 with spatial modulation of the radiation beam within the treatment head

Abstract

A modulator for radiation therapy provides modulation of an area beam to decrease treatment time. Separate channels passing modulated “beamlets” are possible by spacing the channels such that spreading of the beams and multiple angles of treatment eliminate cold spots. The space between the channels allows well-defined channel walls and space for modulator mechanisms.

Claims

1. A radiation therapy machine comprising:

a patient support;

a source of a radiation providing an area beam directed toward a patient on the patient support to expose tissue of the patient,

an areal modulator positioned between the source of radiation and the patient support providing;

(i) a radio-opaque plate extending over an area of the area beam and having a plurality of channels dispersed in two dimensions within the area for passing radiation, a portion of the radio-opaque plate outside of the channels blocking passage of the radiation;

(ii) attenuation elements, located in each of the channels to independently attenuate radiation passing through the channels;

wherein the channels are spaced with respect to each other so that divergence of the radiation after passing through the radio-opaque plate permits substantially uniform exposure of the tissue of the patient over an area corresponding to the area of the radio-opaque plate holding the channels.

2. The radiation therapy machine of claim 1 disposed within a gantry that is moved through a plurality of gantry angles during a radiation therapy session, and further including a controller that independently controls the attenuation through each of the channels as a function of gantry angle.

3. The radiation therapy machine of claim 1 wherein the attenuation elements are cylinders extending along an axis of the channels to hold attenuating fluid and connected to at least one valve system configured to adjust a height of attenuating fluid along the axis to continuously vary the energy fluence of radiation passing through the channels.

4. The radiation therapy machine of claim 3 wherein the attenuating fluid is selected from the group consisting of oil and water.

5. The radiation therapy machine of claim 3 wherein each cylinder connects to at least two valves one connected to a high-pressure reservoir to fill the cylinder and one connected to a low-pressure reservoir to empty the cylinder.

6. The radiation therapy machine of claim 3 wherein the cylinders include a floating piston defining a boundary between the attenuating fluid and a second non-attenuating fluid.

7. The radiation therapy machine of claim 6 further including sensors for sensing the height of the piston and providing an electrical signal to a control system for regulating the height of the fluid in the cylinder.

8. The radiation therapy machine of claim 3 disposed within a gantry that is moved through a plurality of gantry angles during a radiation therapy session, and further including a controller that controls the height of the attenuating fluid along the axis to vary continuously as a function of gantry angle.

9. The radiation therapy machine of claim 1 further wherein the attenuation elements are shutters providing a variable blocking of the channels to continuously vary radiation passing through the channels.

10. The radiation therapy machine of claim 9 wherein the shutters variably block the channels by changing an amount of overlap between different shutter elements.

11. The radiation therapy machine of claim 1 wherein the shutters are disks rotating about a common axis centered within the channel having cutouts that move into and out of alignment with rotation of the disks.

12. A method of radiation therapy comprising:

(a) supporting a patient on a patient support to receive an area beam of radiation directed to the patient from a radiation source,

(b) positioning an areal modulator between the source of radiation and the patient support wherein the areal modulator extends over an area of the beam and has a plurality of channels within the area for passing radiation, and an area outside of the channels blocking passage of the radiation;

(c) controlling attenuation elements located in each of the channels to independently attenuate radiation passing through the channels;

wherein the channels are spaced with respect to each other so that divergence of the radiation after passing through the areal modulator permits substantially uniform exposure of the patient over an area corresponding to the area of the areal modulator.

13. The method of claim 12 wherein the areal modulator is disposed within a gantry and further including the steps of moving the gantry through a plurality of gantry angles while independently controlling the attenuation through each of the channels as a function of gantry angle.

14. The method of claim 12 wherein the attenuation elements are cylinders extending along an axis of the channels to hold attenuating fluid and including the step of adjusting a height of attenuating fluid along the axis to continuously vary the energy fluence of radiation passing through the channels.

15. The method of claim 14 wherein the attenuating fluid is selected from the group consisting of oil and water.

16. The method of claim 14 wherein each cylinder connects to at least two valves, one connected to a high-pressure reservoir and one connected to a low-pressure reservoir and including the step of changing a connection of the cylinder between the reservoirs to control the height of the fluid in the cylinder.

17. The method of claim 14 further including the step of sensing the height of the fluid in the cylinder to control the height of the fluid in the cylinder.

18. The method of claim 14 wherein the areal modulator is disposed within a gantry and including the step of moving the gantry through a plurality of gantry angles during a radiation therapy session while controlling the height of the attenuating fluid along the axis to vary continuously as a function of gantry angle.

19. The method of claim 12 wherein the attenuation elements are shutters and including the step of moving the shutters to provide a continuously variable blocking of the channels to control radiation passing through the channels.

20. The method of claim 19 wherein the shutters variably block the channels by changing an amount of overlap between different shutter elements in both modulation systems.