Six degrees-of-freedom quality assurance phantom for radiation therapy linear accelerators
A three-dimensional phantom for providing displacement profiles for a CT table having 6 degrees of freedom includes a body having at a top face, a side face and an end face; the top face and the side face sharing a common edge; the top face and the end face sharing a common edge; and the side face and the end face sharing a common edge; wherein an angle formed by the top face and the end face is less than 90 degrees; the side face including a first isocenter mark and a first offset mark, wherein the first offset mark has an angle corresponding to the angle formed by the top face and the end face; and an isocenter marker at the isocenter of the body.
1. A three-dimensional phantom for aligning a linear accelerator for radiation therapy equipped with a six degrees-of-freedom (6DoF) treatment table, comprising:
a body having at a top face, a side face and an end face;
the top face and the side face sharing a common edge;
the top face and the end face sharing a common edge; and
the side face and the end face sharing a common edge;
wherein an angle formed by the top face and the end face is less than 90 degrees;
the side face including a first isocenter mark and a first offset mark, wherein the first offset mark has an angle corresponding to the angle formed by the top face and the end face; and
an isocenter marker at the isocenter of the body.
2. The three-dimensional phantom of claim 1 , wherein the body comprises a material to simulate human tissue.
3. The three-dimensional phantom of claim 1 , further comprising a unique registration mark on at least the side face.
4. The three dimensional phantom of claim 3 , wherein the unique registration mark is embossed in the side face of the phantom.
5. The three-dimensional phantom of claim 3 , wherein the unique registration mark includes an asymmetrical character.
6. The three-dimensional phantom of claim 1 , wherein the first isocenter mark includes a first linear visual mark and a second linear visual mark, the first linear visual mark and the second linear visual mark orthogonal to each other in a first plane.
7. The three-dimensional phantom of claim 1 , wherein the first offset mark includes a first linear visual offset mark and a second linear visual offset mark, wherein an angle between the first linear visual offset mark and the second linear visual offset mark in a first plane is 90 degrees.
8. The three-dimensional phantom of claim 1 , wherein the first isocenter mark and the second isocenter mark indicate a projected position of the center of a ball bearing.
9. The three-dimensional phantom of claim 1 , the end face includes a second isocenter mark and a second offset mark, wherein the second offset mark has an angle corresponding to an angle formed by the top face and the side face.
10. A method of performing an alignment test for a computer tomography (CT) table having 6 degrees of freedom for use with a linear accelerator (LINAC) having alignment lasers, the method comprising:
placing a three-dimensional phantom on the CT table, the three-dimensional phantom having a body having at a top face, a side face and an end face; the top face and the side face sharing a common edge; the top face and the end face sharing a common edge; and the side face and the end face sharing a common edge; wherein an angle formed by the top face and the end face is less than 90 degrees; the side face including a first isocenter mark and a first offset mark, wherein the first offset mark has an angle corresponding to the angle formed by the top face and the end face; and an isocenter marker at the isocenter of the body;
aligning the alignment lasers with the first offset mark;
performing a cone-beam scan of the three-dimensional phantom to produce a data set;
comparing the data set with an initial data set previously generated with respect to the phantom leveled to be a true rectangular prism to produce a displacement profile to correct for translations in at least one of the lateral, longitudinal and vertical directions, roll, pitch and yaw of the CT table; and
applying the displacement profile to CT table; and
verifying alignment of the CT table by checking alignment of the alignment lasers against the isocenter marks.
11. The method of claim 10 , wherein the first isocenter mark includes a first linear visual mark and a second linear visual mark, the first linear visual mark and the second linear visual mark orthogonal to each other in a first plane.
12. The method of claim 10 , wherein the displacement profile includes translations for the lateral, longitudinal and vertical directions.
13. The method of claim 10 , wherein the displacement profile includes translations for roll, pitch and yaw of the CT table.
14. The method of claim 10 , wherein the body comprises a material to simulate human tissue.
15. The method of claim 10 , further comprising a unique registration mark on at least the side face.
16. The method of claim 15 , wherein the unique registration mark is used for verifying alignment of the phantom on the CT table.
17. The method of claim 10 , wherein the unique registration mark is embossed in the side face of the phantom.
18. The method of claim 10 , wherein the unique registration mark includes an asymmetrical character.