Tumor and organs at risk motion: an opportunity for better DMLC IMRT delivery systems
Abstract
Radiation therapy is an important tool for the treatment of various types of cancer and works by damaging the DNA of cancerous cells. Doses of radiation are typically applied by sweeping a beam head across an area of the patient's body and activating the beam of radiation when the head is over the tissues to be treated. Although effective at destroying cancer cells, the radiation can damage or destroy healthy tissue as well. Several techniques have been developed in an attempt to minimize movement but these are not always practical and are limited in effectiveness. Our research utilizes computational geometry algorithms and applies them in radiation therapy studies. Our investigation branches into four major directions:
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Moving regions approach
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GPU acceleration and its application to the simulation of treatment planning
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Kinetic bichromatic circular separability
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Algorithms for optimal delivery of volumetric modulated arc therapy
If we know the motion of the target and the surrounding tissues and approximate the shape of the tissues as simple polygons, the problem reduces to determining the time at which the amount of area overlap between the target polygon and the remaining non-target polygons is minimal. This time of minimal area overlap corresponds to maximum exposure of the target. This time (or interval of time) can be determined by maintaining a set of structures that defines the area of intersection between the target polygon P and non-target polygon Q, for all non-target polygons. We can approximate the motion of the tissue as a polyline (the flight plan of the polygon representing the tissue) and keep track of the area of intersection as each polygon moves along its flight plan in time.
Our IMRTVision treatment visualization system provides physicians with the ability to view and compare multiple radiation treatment scenarios at various levels of detail. Users are able to choose from a quad-view, which displays a given treatment ay multiple levels of granularity at once, or an enlarged single granularity level, which is in 3D and fully navigable. Our system also allows the user to load multiple treatments from a database of patient treatments, and run their simulations side-by-side to compare their effectiveness and accumulated dosages over time. At the core of our system is an intensity mapping algorithm which calculates and displays not only a 3D representation of a given treatment at certain time-steps, but is also capable of representing the total accumulated radiation as it is delivered to the tumor and the surrounding tissue over the course of a multi-step treatment.
The kinetic bichromatic circular separability considers the kinetic version of the minimum separating circle problem where one has to find a smallest circle such that it encloses all red points and the smallest possible number of blue points. In the kinetic version of the problem, all points move with constant speed along straight trajectories. With the aid of kinetic data structure we maintain the smallest enclosing circle(s) over time at any given time With the aid of kinetic data structure we maintain the smallest enclosing circle(s) over time at any given time t. The problem has a wide range of applications including: biomedical engineering, image processing, military planning, network router placement, etc.
The rapid delivery of VMAT arc therapy requires fast motion of the gantry around the patient. The difficulty is that the large inertia of the accelerator gantry limits rotation speed changes restricting the ability of the accelerator to arc as fast as possible without violating the integrity of the plan. We examine arc therapy deliveries for static and moving target in presence of acceleration limitation for gantry angular speed. We compute the shortest time of arc therapy delivery, provided different acceleration limitations are imposed. The problem of arc delivery to a moving target is a complex optimal control due to dependence of motion constraints of the state of the evolution. More stringent limits on the acceleration lead to longer delivery time and successive decrease of the mechanical strain on the gantry rotation mechanism.
Award ID: 1035460
Submitted by Ovidiu Daescu
on
Abstract
Radiation therapy is an important tool for the treatment of various types of cancer and works by damaging the DNA of cancerous cells. Doses of radiation are typically applied by sweeping a beam head across an area of the patient's body and activating the beam of radiation when the head is over the tissues to be treated. Although effective at destroying cancer cells, the radiation can damage or destroy healthy tissue as well. Several techniques have been developed in an attempt to minimize movement but these are not always practical and are limited in effectiveness. Our research utilizes computational geometry algorithms and applies them in radiation therapy studies. Our investigation branches into four major directions:
-
Moving regions approach
-
GPU acceleration and its application to the simulation of treatment planning
-
Kinetic bichromatic circular separability
-
Algorithms for optimal delivery of volumetric modulated arc therapy
If we know the motion of the target and the surrounding tissues and approximate the shape of the tissues as simple polygons, the problem reduces to determining the time at which the amount of area overlap between the target polygon and the remaining non-target polygons is minimal. This time of minimal area overlap corresponds to maximum exposure of the target. This time (or interval of time) can be determined by maintaining a set of structures that defines the area of intersection between the target polygon P and non-target polygon Q, for all non-target polygons. We can approximate the motion of the tissue as a polyline (the flight plan of the polygon representing the tissue) and keep track of the area of intersection as each polygon moves along its flight plan in time.
Our IMRTVision treatment visualization system provides physicians with the ability to view and compare multiple radiation treatment scenarios at various levels of detail. Users are able to choose from a quad-view, which displays a given treatment ay multiple levels of granularity at once, or an enlarged single granularity level, which is in 3D and fully navigable. Our system also allows the user to load multiple treatments from a database of patient treatments, and run their simulations side-by-side to compare their effectiveness and accumulated dosages over time. At the core of our system is an intensity mapping algorithm which calculates and displays not only a 3D representation of a given treatment at certain time-steps, but is also capable of representing the total accumulated radiation as it is delivered to the tumor and the surrounding tissue over the course of a multi-step treatment.
The kinetic bichromatic circular separability considers the kinetic version of the minimum separating circle problem where one has to find a smallest circle such that it encloses all red points and the smallest possible number of blue points. In the kinetic version of the problem, all points move with constant speed along straight trajectories. With the aid of kinetic data structure we maintain the smallest enclosing circle(s) over time at any given time With the aid of kinetic data structure we maintain the smallest enclosing circle(s) over time at any given time t. The problem has a wide range of applications including: biomedical engineering, image processing, military planning, network router placement, etc.
The rapid delivery of VMAT arc therapy requires fast motion of the gantry around the patient. The difficulty is that the large inertia of the accelerator gantry limits rotation speed changes restricting the ability of the accelerator to arc as fast as possible without violating the integrity of the plan. We examine arc therapy deliveries for static and moving target in presence of acceleration limitation for gantry angular speed. We compute the shortest time of arc therapy delivery, provided different acceleration limitations are imposed. The problem of arc delivery to a moving target is a complex optimal control due to dependence of motion constraints of the state of the evolution. More stringent limits on the acceleration lead to longer delivery time and successive decrease of the mechanical strain on the gantry rotation mechanism.
Award ID: 1035460