System and method for multi-target single-isocenter radiation therapy quality assurance

A system for quality assurance in single-isocenter, multi-target (SIMT) radiation therapy, the system comprising:

• (1) a phantom comprising an off-isocenter radiation opaque marker;
• (2) a linear accelerator (LINAC) configured to generate a radiation beam, wherein the LINAC comprises an imaging device configured to acquire a two-dimensional (2D) radiation transmission image indicative of a radiation field of the generated radiation beam after passing through the off-isocenter radiation opaque marker of the phantom, and the off-isocenter radiation opaque marker is offset from an isocenter of the LINAC in at least one spatial dimension;
• (3) a measurement system configured to measure an actual marker position in a three-dimensional (3D) coordinate system of the LINAC, wherein the actual marker position is a measured position of the off-isocenter radiation opaque marker of the phantom, and the off-isocenter radiation opaque marker is offset from an isocenter of the LINAC in at least one spatial dimension;
• and
• (4) processing circuitry configured to:
• (a) use the actual marker position to compute a beam's eye view marker position, wherein the beam's eye view marker position is a projected position of the off-isocenter radiation opaque marker in an expected field contour of an expected radiation beam, and the expected radiation beam is a radiation beam expected to be generated by the LINAC;
• (b) determine a centroid of the expected field contour;
• (c) use the 2D radiation transmission image to determine (i) a measured field contour and (ii) a measured marker contour, wherein the measured field contour is a boundary of the radiation field of the generated radiation beam in the 2D radiation transmission image, and the measured marker contour is a boundary of a shadow of the off-isocenter radiation opaque marker in the radiation field of the generated radiation beam in the 2D radiation transmission image;
• (d) determine a centroid of the measured field contour and a centroid of the measured marker contour;
• (e) align the beam's eye view marker position with the centroid of the measured marker contour at a common marker reference point;
• and
• (f) with the beam's eye view marker position aligned with the centroid of the measured marker contour at the common marker reference point, determine a geometric error, wherein the geometric error is a 2D distance between the centroid of the expected field contour and the centroid of the measured field contour.

A method for quality assurance in single-isocenter, multi-target (SIMT) radiation therapy, the method comprising:

• (a) using a measurement system to acquire megavoltage, kilovoltage, and/or surface images of a phantom, wherein the measurement system comprises a kilovoltage imaging system, a megavoltage imaging system, and/or a surface imaging device, and the phantom comprises one or more off-isocenter radiation opaque markers;
• (b) using the megavoltage, kilovoltage, and/or surface images to determine one or more three-dimensional (3D) positions of the one or more off-isocenter radiation opaque markers;
• (c) calculating a rotational deviation of the phantom, wherein calculating the rotational deviation of the phantom comprises comparing the one or more determined 3D positions of the one or more off-isocenter radiation opaque markers with one or more expected 3D positions of the one or more off-isocenter radiation opaque markers;
• and
• (d) using the calculated rotational deviation of the phantom to adjust an orientation of the phantom.

A system for quality assurance in single-isocenter, multi-target (SIMT) radiation therapy, the system comprising:

• a phantom comprising one or more off-isocenter radiation opaque markers;
• a measurement system configured to acquire megavoltage, kilovoltage, and/or surface images of a phantom, wherein the measurement system comprises a kilovoltage imaging system, a megavoltage imaging system, and/or a surface imaging device;
• processing circuitry configured to:
• (1) use the megavoltage, kilovoltage, and/or surface images to determine one or more three-dimensional (3D) positions of the one or more off-isocenter radiation opaque markers;
• and
• (2) calculate a rotational deviation of the phantom, wherein calculating the rotational deviation of the phantom comprises comparing the one or more determined 3D positions of the one or more off-isocenter radiation opaque markers with one or more expected 3D positions of the one or more off-isocenter radiation opaque markers.

A method for generating an expected field contour for use in quality assurance of single-isocenter, multi-target (SIMT) radiation therapy treatments, the method comprising:

• (a) obtaining, from a treatment planning system (TPS), a two-dimensional (2D) dose distribution computed in a beam's-eye view plane at a depth of an off-isocenter radiation opaque marker of a phantom, wherein the off-isocenter radiation opaque marker is offset from an isocenter of a linear accelerator (LINAC) in at least one spatial dimension;
• (b) extracting an isodose contour by applying an isodose threshold to the 2D dose distribution;
• and
• (c) using the extracted isodose contour as the expected field contour against which a 2D radiation transmission image acquired by an imaging device of the LINAC is compared to determine a geometric accuracy of radiation field delivery at a position of the off-isocenter radiation opaque marker.

A method for end-to-end quality assurance in single-isocenter, multi-target (SIMT) radiation therapy, the method comprising:

• (a) obtaining a reference marker position from a treatment planning system (TPS), wherein the reference marker position is a derived position of an off-isocenter radiation opaque marker of a phantom, the off-isocenter radiation opaque marker is offset from an isocenter of a linear accelerator (LINAC) in at least one spatial dimension, and the reference marker position is derived from one of:
• (i) a centroid of a marker structure contour defined in a radiotherapy (RT) structure set generated during treatment planning and (ii) a centroid of a volume of the off-isocenter radiation opaque marker as represented in an RT dose distribution computed by the TPS;
• (b) projecting the reference marker position into a beam's-eye view corresponding to a planned gantry angle and couch angle of the LINAC, without applying a correction for physical positioning errors of the phantom;
• (c) using the LINAC to generate a radiation beam;
• (d) using an imaging device of the LINAC to acquire a two-dimensional (2D) radiation transmission image indicative of a radiation field of the generated radiation beam after passing through the off-isocenter radiation opaque marker of the phantom;
• (e) using the 2D radiation transmission image to determine (1) a measured field contour and (2) a measured marker contour, wherein the measured field contour is a boundary of the radiation field of the generated radiation beam in the 2D radiation transmission image, and the measured marker contour is a boundary of a shadow of the off-isocenter radiation opaque marker in the radiation field of the generated radiation beam in the 2D radiation transmission image;
• (f) determining a centroid of the measured field contour and a centroid of the measured marker contour;
• (g) aligning the reference marker position with the centroid of the measured marker contour at a common marker reference point;
• and
• (h) with the reference marker position aligned with the centroid of the measured marker contour at the common marker reference point, determining a geometric error, wherein the geometric error is a 2D distance between a centroid of an expected field contour of an expected radiation beam and the centroid of the measured field contour, and the expected radiation beam is a radiation beam expected to be generated by the LINAC.

A system for end-to-end quality assurance in single-isocenter, multi-target (SIMT) radiation therapy, the system comprising:

• (1) a phantom comprising an off-isocenter radiation opaque marker;
• (2) a linear accelerator (LINAC) configured to generate a radiation beam, wherein the LINAC comprises an imaging device configured to acquire a two-dimensional (2D) radiation transmission image indicative of a radiation field of the generated radiation beam after passing through the off-isocenter radiation opaque marker of the phantom, and the off-isocenter radiation opaque marker is offset from an isocenter of the LINAC in at least one spatial dimension;
• and
• (3) processing circuitry configured to:
• (a) obtain a reference marker position from a treatment planning system (TPS), wherein the reference marker position is a derived position of the off-isocenter radiation opaque marker of the phantom, and the reference marker position is derived from one of:
• (i) a centroid of a marker structure contour defined in a radiotherapy (RT) structure set generated during treatment planning and (ii) a centroid of a volume of the off-isocenter radiation opaque marker as represented in an RT dose distribution computed by the TPS;
• (b) project the reference marker position into a beam's-eye view corresponding to a planned gantry angle and couch angle of the LINAC, without applying a correction for physical positioning errors of the phantom;
• (c) use the 2D radiation transmission image to determine (1) a measured field contour and (2) a measured marker contour, wherein the measured field contour is a boundary of the radiation field of the generated radiation beam in the 2D radiation transmission image, and the measured marker contour is a boundary of a shadow of the off-isocenter radiation opaque marker in the radiation field of the generated radiation beam in the 2D radiation transmission image;
• (d) determine a centroid of the measured field contour and a centroid of the measured marker contour;
• (e) align the reference marker position with the centroid of the measured marker contour at a common marker reference point;
• and
• (f) with the reference marker position aligned with the centroid of the measured marker contour at the common marker reference point, determine a geometric error, wherein the geometric error is a 2D distance between a centroid of an expected field contour of an expected radiation beam and the centroid of the measured field contour, and the expected radiation beam is a radiation beam expected to be generated by the LINAC.