Fluence based proton beam quality assurance with Micromegas

Project: Research project

Project Details

Description

Fluence based proton beam quality assurance with Micromegas Fluence based proton beam quality assurance with Micromegas Mayo Clinic proton beam therapy facilities in Rochester and Phoenix are expected to treat approximately 1200 patients each per year. In order to ensure patient safety it is mandatory that each patient treatment undergo a rigorous patient specific quality assurance (QA) process. During QA patient treatments are delivered to a measurement device in order to determine to what degree the deliverable treatment coincides with the planned treatment, which represents the radiation oncologist's intent. In the current state of the art QA requires on average three hours of dose measurements in the treatment room during which patient treatments cannot be carried out, because the beam is fully dedicated to QA. Furthermore, current QA practice fails to predict what effect an observed deviation from the planned patient treatment would have on the outcome of treatment. Current QA is based on dose measurements in water or a water-like medium (phantom) and requires a bulky experimental set-up. In order to characterize the dose in the phantom the measuring device needs to be moved to make several measurements. With current technology this process takes approximately three hours in the treatment room. In order to treat 1200 patients per year 60 hours of QA would need to be conducted every week. In order to reach the goal of 1200 patients per year the proton beam therapy facility needs to treat patients in two daily shifts of 8 hours each. This precludes the use of 60 hours per week of treatment room time for QA purposes. Therefore, if the Mayo proton therapy facilities are to reach the goal of treating 1200 patients per year, a less time consuming process for patient specific QA is urgently needed. Furthermore, current technology precludes the radiation oncologist from evaluating the effect of differences between planned treatment and deliverable treatment in terms of treatment outcome. This is due to the fact that in proton beam therapy the dose distribution in the homogeneous phantom is drastically different from the dose distribution in the in-homogeneous patient. In order to allow the radiation oncologist to evaluate the appropriateness of the deliverable treatment, a tool is needed, which allows the physician to evaluate the effect of the deliverable treatment on the patient. Our research investigates whether it is possible to carry out patient specific QA in a very efficient way by incorporating tools from modern high energy physics. This translational research is designed to improve the state of the art of radiation therapy by incorporating tools from modern high energy physics into the practice of proton beam therapy. Our objective in this grant application is the development of a novel QA process based on the measurement of proton fluence using micro-mesh gaseous structure detectors (Micromegas), which will reduce the time used for QA in the treatment room from three hours to 20 minutes. Micromegas are used with great success in modern high energy physics. In 2001, twelve large Micromegas detector planes of 40 x 40 cm were used for the first time in a large scale experiment at COMPASS situated on the Super Proton Synchrotron accelerator at CERN. Since 2002 they have been detecting millions of passing particles per second and still continue today. The invention of bulk technology allows for the integration of the micro-mesh with the signal-reading printed circuit board which results in a monolithic detector array. Such detectors are proven to be very robust and can be produced via cost-efficient industrial processes. Their characteristics make them uniquely suitable for application in proton beam therapy. Among these characteristics are: high coordinate resolution, accurate fluence mapping, radiation hardness and mechanical durability. The novel Micromegas-based QA process under investigation will allow the radiation oncologist to estimate the effect of the deliverable treatment (as opposed to the planned treatment) on the patient by visualizing, in three dimensions, dose to patient caused by the deliverable treatment. In particular, the proposed novel QA process will allow the physician to compare the deliverable dose the planned dose and thereby judge the appropriateness of treatment. The research team consists of the Lead Physicist for the proton beam therapy project at Mayo Clinic, Arizona. He has extensive experience in the characterization of proton beams through fluence measurements. The co-investigator is an expert in high-energy particle detector design.
StatusFinished
Effective start/end date8/15/148/14/17

Funding

  • Mayo Clinic Arizona: $57,494.00

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