This project is a research into developing a compact, variable dose rate, variable precision small animal irradiator using a novel miniature x-ray source based on carbon nanotubes. The project's long-term goals include simulation, prototyping and validation of a high dose rate, low energy, directional x-ray tube no more than a few centimeters long. From there, a collimating apparatus will arrange several of these sources in a converging beam geometry with individual control over each source’s exposure rate and distance from the target to create variable dose rates and variable beam sizes. Further aims of this work are to have an irradiator capable of FLASH dose rates at one setting and ultrafine beam delivery in another setting, complete with 4D staging, treatment planning software, a robust 3-dimensional dose painting algorithm and validated QA routines. This invention will allow preclinical research to access far more of the modern radiotherapy parameter space than is currently accessible with commercial irradiators.
Currently, we are in the stages of designing the miniature x-ray source. Through Monte Carlo simulation, we have proven the advantageous dosimetric properties of our proposed geometry. In the next steps, we will design the electrodes, simulate the electron transport and calculate the heat transfer against various voltage waveforms before constructing the x-ray tube. Further steps will include a partnership with an engineering firm to develop a prototype of the source for experimental evaluation and characterization.
Update: Patent applications have been filed with the US Patent Office.
MD Anderson has formed a strategic partnership with Convergent Radiotherapy and Radiosurgery (CRNR Ltd.) to develop a novel focused x-ray radiotherapy device. Read a press release on this strategic alliance.
CRNR Ltd. developed a lens that produces a converging beam of x-rays from a diverging source such as a conventional x-ray tube. The nature of the physical process that produces the reflected x-rays within the lens structure results in a nearly monoenergetic beam stemming from a polyenergetic radiation source. Such a novel focused monoenergetic beam can deliver highly localized doses of radiation within the target with significantly decreased surface dose. The whole system, x-ray source and lens are mounted on a robotically controlled arm to manipulate the focal spot and paint conformal dose distributions.
MD Anderson’s contribution to the CRNR development is multi-faceted. We have recently installed the generation 2 prototype of the lens and x-ray tube. We currently perform various measurements to characterize the beam in clinically relevant materials. We have performed cell irradiation to determine the RBE of this unique beam. We are now preparing to perform small animal experiments.
Additionally, we are contributing to dosimetry development for this system by establishing a collaboration with Medscint inc. (Québec, Canada) to evaluate a small-field scintillation dosimeter for the CRNR beam. Furthermore, we have ongoing work to perform Monte Carlo simulations of the CRNR system, which involves developing a novel Geant4 application incorporating Bragg Diffraction as a Geant4 physics process. We are also contributing to the academic dissemination of the system's novelty. Our first manuscript on this work was published in Nature Scientific Reports: Analysis of a novel X-ray lens for converging beam radiotherapy.
The 2nd manuscript is on Physics in Medicine and Biology (PMB) online access website: Dosimetry of a novel focused monoenergetic beam for radiotherapy.
A novel electron beam delivery system is being researched and developed that uses Very High Energy Electrons (VHEE) to produce a localized spot of high dose within the target volume through a technique referred to as Magnetically Optimized Very High Energy Electron Therapy (MOVHEET). This high dose region is dynamically controlled to produce a dose intensity within the tumor volume higher than surrounding normal tissues, resulting in greater normal tissue sparing and a more significant degree of tumor control. The delivery system is based on the principle of dynamically focusing a beam of 50 – 250 MeV electrons to the desired target depth determined by a radiation treatment plan dose distribution where the output of the focusing system is a uniformly symmetric beam with a focusing angle that results in a low beam density at the patient surface thus producing low entrance dose. A set of quadrupole magnets are used to dynamically control the focal spot depth of the electron focusing system to alter the electron trajectories and produce the desired beam behavior.
A wide range of simulations and analyses of the parameters affecting converging beam dose delivery has been completed. Furthermore, additional simulations have been conducted to characterize the basic parameters required for the quadrupole delivery system. A patent on the said delivery system has been applied for and granted. Collaborations with accelerator physicists and manufacturers have been established, and parameters for a novel VHEE accelerator must be determined. Empyrean Medical Systems (Boca Raton, FL) has reached a licensing agreement with MD Anderson to develop the MOVHEET concept into a commercial radiotherapy device.