Method and apparatus to employ a multi-layer multi-leaf collimator when administering a radiation therapy treatment

1. A method for use with a radiation therapy treatment platform having a multi-layer multi-leaf collimation system wherein a proximal layer of a plurality of collimation leaf pairs are vertically offset with respect to a distal layer of a plurality of collimation leaf pairs such that the two multi-layer multi-leaf collimators combine to form a plurality of linearly-sequential high-resolution aperture possibilities, the method comprising:

by a control circuit:

administering a radiation treatment plan that specifies a planned total radiation dose for a radiation treatment session for a given patient by, at least in part and for a first treatment field, administering two and only two radiation exposures, wherein:

a first radiation exposure for the first treatment field comprises modulating a radiation beam using a first fixed aperture that includes at least one high-resolution aperture that is formed using one of the plurality of linearly-sequential high-resolution aperture possibilities; and

a second separate radiation exposure for the first treatment field comprises modulating the radiation beam using a second fixed aperture that is different from the first fixed aperture and that includes at least one high-resolution aperture that is formed using one of the plurality of linearly-sequential high-resolution aperture possibilities.

2. The method of claim 1 wherein at least some of the plurality of linearly-sequential high-resolution aperture possibilities have a height resolution that is twice the resolution of aperture possibilities that are available with either of the proximal or distal layer of the plurality of collimation leaf pairs alone.

3. The method of claim 2 wherein at least substantially all of the plurality of linearly-sequential high-resolution aperture possibilities have a height resolution that is twice the resolution of aperture possibilities that are available with either of the proximal or distal layer of the plurality of collimation leaf pairs alone.

4. The method of claim 1 wherein at least one of the high-resolution apertures has at least one boundary defined only by the proximal layer and at least one other boundary defined only by the distal layer.

5. The method of claim 1 wherein the first radiation exposure for the first treatment field comprises modulating a radiation beam using a first fixed aperture comprised of at least substantially only high-resolution apertures that are formed using the plurality of linearly-sequential high-resolution aperture possibilities and wherein the second radiation exposure for the first treatment field comprises modulating a radiation beam using a second fixed aperture that is different from the first fixed aperture and that is comprised of at least substantially only high-resolution apertures that are formed using the plurality of linearly-sequential high-resolution aperture possibilities.

6. The method of claim 1 wherein the high-resolution apertures are grouped in sequential pairs and the sequential pairs of high-resolution apertures are separated from one another by a pair of sequential unused high-resolution aperture possibilities of the plurality of linearly-sequential high-resolution aperture possibilities.

7. An apparatus comprising:

a source of therapeutic radiation configured to emit a radiation beam;

a multi-layer multi-leaf collimation system wherein a proximal layer of a plurality of collimation leaf pairs are vertically offset with respect to a distal layer of a plurality of collimation leaf pairs such that the two multi-layer multi-leaf collimators combine to form a plurality of linearly-sequential high-resolution aperture possibilities; and

a control circuit operably coupled to the source of therapeutic radiation and to the multi-layer multi-leaf collimation system, the control circuit being configured to administer a radiation treatment plan that specifies a planned total radiation dose for a radiation treatment session for a given patient, at least in part and for a first treatment field, by administering two and only two radiation exposures, wherein:

a first radiation exposure for the first treatment field comprises modulating a radiation beam using a first fixed aperture that includes at least one high-resolution aperture that is formed using one of the plurality of linearly-sequential high-resolution aperture possibilities; and

a second separate radiation exposure for the first treatment field comprises modulating the radiation beam using a second fixed aperture that is different from the first fixed aperture and that includes at least one high-resolution aperture that is formed using one of the plurality of linearly-sequential high-resolution aperture possibilities.

8. The apparatus of claim 7 wherein at least some of the plurality of linearly-sequential high-resolution aperture possibilities have a height resolution that is twice the resolution of aperture possibilities that are available with either of the proximal or distal layer of the plurality of collimation leaf pairs alone.

9. The apparatus of claim 8 wherein at least substantially all of the plurality of linearly-sequential high-resolution aperture possibilities have a height resolution that is twice the resolution of aperture possibilities that are available with either of the proximal or distal layer of the plurality of collimation leaf pairs alone.

10. The apparatus of claim 7 wherein at least one of the high-resolution apertures has at least one boundary defined only by the proximal layer and at least one other boundary defined only by the distal layer.

11. The apparatus of claim 7 wherein the control circuit is configured to administer the radiation treatment plan by modulating the radiation beam using at least substantially only high-resolution apertures that are formed using the plurality of the linearly-sequential high-resolution aperture possibilities.

12. The apparatus of claim 7 wherein the high-resolution apertures are grouped in sequential pairs and the sequential pairs of high-resolution apertures are separated from one another by a pair of sequential unused high-resolution aperture possibilities of the plurality of linearly-sequential high-resolution aperture possibilities.

13. A method for use with a radiation therapy treatment platform having a multi-layer multi-leaf collimation system wherein a proximal layer of a plurality of collimation leaf pairs are vertically offset with respect to a distal layer of a plurality of collimation leaf pairs such that the two multi-layer multi-leaf collimators combine to form a plurality of linearly-sequential high-resolution aperture possibilities, the method comprising:

by a control circuit:

administering a radiation treatment plan that specifies a planned total radiation dose for a radiation treatment session for a given patient by, at least in part and for a first treatment field, administering two radiation exposures, wherein:

a first radiation exposure for the first treatment field comprises modulating a radiation beam using a first fixed aperture that includes at least one high-resolution aperture that is formed using one of the plurality of linearly-sequential high-resolution aperture possibilities; and

a second separate radiation exposure for the first treatment field comprises modulating the radiation beam using a second fixed aperture that is different from the first fixed aperture and that includes at least one high-resolution aperture that is formed using one of the plurality of linearly-sequential high-resolution aperture possibilities.