Development of an MRI-Compatible, Dynamic, and Deformable Imaging Phantom
Washington University in St. Louis Biomedical Engineering Senior Design Course
Group 29
Group Members: Jacintha Sales, Leah Laux
Mentors: Dr. Olga Green and Dr. Parag Parikh, Washington University School of Medicine (Radiology-Oncology Department)
Title: Development of a MRI-Compatible Dynamic and Deformable Imaging Phantom
Background
Technological advancements in hardware and software have enabled magnetic resonance imaging (MRI) to flourish, establishing it as an invaluable instrument in the visualization of internal structures and the characterization of physiological motion. This overall increase in imaging capability has triggered the vast increase in the range of MRI applications, which has recently been extended to the field of oncology and radiation therapy in a revolutionary way.
In the past, MRI has been used in radiation therapy for pre-treatment planning and daily patient setup on the treatment machine. A single set of images taken once before treatment would typically be used to initially plan treatment and then to attempt to replicate, over multiple weeks of fractional treatment, patient position captured in the planning images. Shaped ionizing radiation beams would then be aimed from several angles to intersect at the predicted tumor location based on the MRI images taken before treatment. But even perfect patient-position replication cannot account for the internal organ movement and deformation or tumor growth and shrinkage that occur throughout the treatment process and even during radiation therapy. These deformations, though just centimeters in magnitude, can greatly affect the tumor-targeting precision and overall effectiveness of the treatment. To solve this problem, ViewRay Incorporated developed the ViewRay system, the first commercially available MRI-guided radiation therapy system. The first ViewRay system was installed at the Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine in January 2012 for clinical research, and it received marketing clearance from the U.S. FDA in May 2012.
Using a patented combination of full-time MR-imaging and radiation therapy delivery technology, the ViewRay system provides high-quality pretreatment images as well as continuous soft-tissue imaging during radiation treatment. Being able to see the target and watch precisely where the radiation dose is delivered better allows clinicians to assess and adapt treatment according to changes in patient anatomy. The ViewRay system additionally comes with built-in treatment planning and delivery software, which allows physician descriptions to define the parameters—dose, constraints, and objectives—of the treatment process. The software provides continuous, MRI-guided soft-tissue tracking and automatic beam control during treatment, as well as the ability to pause treatment if the predicted dose goes out of tolerance due to organ motion, deformation, or other changes.
This key feature of the ViewRay software system is extremely important in radiation therapy delivery, since it spares normal tissue from exposure to harmful radiation beams as much as possible. Ionizing radiation therapy works by damaging the DNA of exposed tissue and consequently causing cellular death of the targeted tumor. Since this destructive effect is also experienced by any normal tissue receiving the radiation dosage, radiation therapy delivery systems necessitate stringent tests of accuracy in regard to both imaging and dosimetry. Considering the newness of the ViewRay machine along with the potential dosimetric effects that arise from the passing of a radiation beam through an MR field, the ViewRay system is currently in great need of a means of testing the accuracy of its software.
The safest and most reliable test of accuracy in the field of medical imaging is with imaging phantoms, which are objects with tissue-like properties specifically designed to be imaged in order to evaluate, analyze, and tune the performance of imaging devices. Therefore, in order to test the accuracy of the new ViewRay system software in computing deformation, a phantom with known deformation and tissue-like properties is needed to be imaged, processed by the software, and ultimately used to evaluate overall ViewRay performance. Several imaging phantoms of a similar type have been previously developed, however most of these phantoms are made with metals and consequently are not compatible with MRI. Similar work has additionally been done in the field of MR-cardiac imaging, but these phantoms typically display limited or no deformation or are in need of improved accuracy. Therefore, this project will attempt to solve the problems of MRI-compatibility and tissue-like deformation in the process of developing a complete imaging phantom design for quality assurance purposes.
Group 29
Group Members: Jacintha Sales, Leah Laux
Mentors: Dr. Olga Green and Dr. Parag Parikh, Washington University School of Medicine (Radiology-Oncology Department)
Title: Development of a MRI-Compatible Dynamic and Deformable Imaging Phantom
Background
Technological advancements in hardware and software have enabled magnetic resonance imaging (MRI) to flourish, establishing it as an invaluable instrument in the visualization of internal structures and the characterization of physiological motion. This overall increase in imaging capability has triggered the vast increase in the range of MRI applications, which has recently been extended to the field of oncology and radiation therapy in a revolutionary way.
In the past, MRI has been used in radiation therapy for pre-treatment planning and daily patient setup on the treatment machine. A single set of images taken once before treatment would typically be used to initially plan treatment and then to attempt to replicate, over multiple weeks of fractional treatment, patient position captured in the planning images. Shaped ionizing radiation beams would then be aimed from several angles to intersect at the predicted tumor location based on the MRI images taken before treatment. But even perfect patient-position replication cannot account for the internal organ movement and deformation or tumor growth and shrinkage that occur throughout the treatment process and even during radiation therapy. These deformations, though just centimeters in magnitude, can greatly affect the tumor-targeting precision and overall effectiveness of the treatment. To solve this problem, ViewRay Incorporated developed the ViewRay system, the first commercially available MRI-guided radiation therapy system. The first ViewRay system was installed at the Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine in January 2012 for clinical research, and it received marketing clearance from the U.S. FDA in May 2012.
Using a patented combination of full-time MR-imaging and radiation therapy delivery technology, the ViewRay system provides high-quality pretreatment images as well as continuous soft-tissue imaging during radiation treatment. Being able to see the target and watch precisely where the radiation dose is delivered better allows clinicians to assess and adapt treatment according to changes in patient anatomy. The ViewRay system additionally comes with built-in treatment planning and delivery software, which allows physician descriptions to define the parameters—dose, constraints, and objectives—of the treatment process. The software provides continuous, MRI-guided soft-tissue tracking and automatic beam control during treatment, as well as the ability to pause treatment if the predicted dose goes out of tolerance due to organ motion, deformation, or other changes.
This key feature of the ViewRay software system is extremely important in radiation therapy delivery, since it spares normal tissue from exposure to harmful radiation beams as much as possible. Ionizing radiation therapy works by damaging the DNA of exposed tissue and consequently causing cellular death of the targeted tumor. Since this destructive effect is also experienced by any normal tissue receiving the radiation dosage, radiation therapy delivery systems necessitate stringent tests of accuracy in regard to both imaging and dosimetry. Considering the newness of the ViewRay machine along with the potential dosimetric effects that arise from the passing of a radiation beam through an MR field, the ViewRay system is currently in great need of a means of testing the accuracy of its software.
The safest and most reliable test of accuracy in the field of medical imaging is with imaging phantoms, which are objects with tissue-like properties specifically designed to be imaged in order to evaluate, analyze, and tune the performance of imaging devices. Therefore, in order to test the accuracy of the new ViewRay system software in computing deformation, a phantom with known deformation and tissue-like properties is needed to be imaged, processed by the software, and ultimately used to evaluate overall ViewRay performance. Several imaging phantoms of a similar type have been previously developed, however most of these phantoms are made with metals and consequently are not compatible with MRI. Similar work has additionally been done in the field of MR-cardiac imaging, but these phantoms typically display limited or no deformation or are in need of improved accuracy. Therefore, this project will attempt to solve the problems of MRI-compatibility and tissue-like deformation in the process of developing a complete imaging phantom design for quality assurance purposes.