Radiation Safety, Environmental Sciences, and Medical Physics (REM)

This is a new unified program focused on the applications of nuclear science and technology to human health and the environment.

Medical physics is primarily concerned with the use of ionizing and non-ionizing radiation and the application of physical and mathematical techniques in the diagnosis and treatment of disease. Medical physicists work actively in the physical aspects of diagnostic radiology, diagnostic ultrasound, magnetic resonance imaging, radiation oncology, nuclear medicine, and radiation safety. Much of medical physics involves basic applications of ionizing and non-ionizing radiation science directly overlapping the NERS Department's historical interests (basic radiation transport, photonics, neutronics, electron transport, basic radiation physics, radiation shielding, transport methods, and Monte Carlos methods).  It should be noted that the medical physics program is a research-oriented interrelated program of radiation safety, environmental sciences, and medical physics.  The REM program is not a clinically-based program; i.e., REM is research-oriented.   

Radiological health engineering (RHE) deals with the application of engineering and scientific principles to the solution of radiation safety problems that involve individuals, populations, or environment. RHE, of which health physics and applied radiation biology are considered important subjects, applies a broad knowledge of radiation biology, radiation protection practices, radiation dose estimation, and radiation measurements. NERS faculty hold particular expertise in development of detectors, dosimeters, and imaging devices for specific RHE applications and radiobiological research, as well as covering the breadth of the different technical aspects of the low-level and high-level radioactive waste management problem.

The overall objective of the RHE is the protection of people and the environment from unnecessary exposure to radiation to achieve this, the radiological health engineer requires a sound education in the fundamental physics of radiation and radioactive materials and in the basic engineering principles required to apply that knowledge.

Some areas of research include:

Advanced Monte Carlo-based treatment planning

This research is devoted to making dose calculations via Monte Carlo methods, practical in day-to-day clinical use. Monte Carlo is considered to be the most accurate method of dose calculation technology for radiation treatment planning, though it suffers from enormous demands on computer resources. Research may involve 1) multi-platform, modestly parallel computer architecture implementation, 2) basic Monte Carlo algorithms development, or 3) statistical noise reduction via mathematical methods.

Enhanced Radiation Therapy Treatment Planning and Delivery

For treatment of cancer by external-beam radiotherapy, more dose to the diseased tissue, accompanied by less dose to the healthy tissue, results in higher cure rates and lower rates of healthy tissue damage. However, these treatments are affected by patient motion associated with treatment setup and breathing. Cancer therapy could be more aggressive if patient motion were better characterized, and/or better controlled. Optimization methods can be used to help incorporate these effects in the treatment planning process as well as streamline treatment delivery. Currently, strategies to mitigate and/or incorporate the effects of tumor and normal tissue motion due to patient movement and breathing are being actively investigated. Additionally, applied mathematical approaches to treatment planning and delivery are being pursued.

Combined 3D X-ray and 3D Ultrasound Breast Imaging System

In collaboration with GE Global Research, a new dual-modality system is being developed that images the breast with x-rays and ultrasound in the same geometry, thereby insuring perfect registration between the masses detected with both modalities. The system acquires multiple x-ray projections and reconstructs images of 1 mm thick slices using a technique called tomosynthesis. This significantly reduces the overlap problem in conventional single projection mammography in which masses are often camouflaged by overlying and underling dense tissues. The dual modality system should improve breast mass characterization, thereby eliminating unnecessary biopsies and workups and it should also facilitate the earlier detection of breast cancer. Preliminary trials with patients have shown much promise. Research is ongoing in determining better tomosynthesis reconstruction methods and incorporating and developing advanced imaging modes for the dual-modality system such as ultrasound Doppler and elasticity imaging and contrast enhanced x-ray imaging.

Diagnostic Radiology Quality Assurance Research Projects

Medical Physicists in the department of Diagnostic Radiology at the University of Michigan Hospital have performed research in many aspects of quality assurance including: a Monte Carlo method for estimating the normalized average glandular dose in magnification mammography, dose reduction techniques in pediatric fluoroscopy, solid state skin dose monitor accuracy, the line-pair pattern method for evaluating focal spot size in mammography, x-ray transmission through lead equivalent aprons, and gray-scale ultrasound system evaluation. Current projects include evaluation of scatter fractions for CT scanner shielding calculations and evaluation of automated analysis of images of a contrast-detail test object for the assessment of computed radiography and digital radiography systems.

Medical X-ray Imaging Research

Advanced methods for x-ray imaging continue to improve the detection and management of disease in medicine. Currently active research in this laboratory involves digital radiography, tomo-synthesis, and high resolution computed tomography. A project on computational simulation is directed at methods to optimize radiographic techniques. For digital radiographs, the perception of disease in background noise is being investigated along with image processing methods designed to improved observer performance. High resolution imaging of joints is being developed in conjunction with Industry using advanced digital detectors and limited angle tomography acquisition (tomo-synthesis). In an experimental micro-tomography laboratory, specimen and small animal imaging computed tomography methods are being developed.

Development of Personnel and Environmental Dosimeters

Protection of personnel and members of the general public from radiation produced by a variety of industrial, defense, power, and medical sources requires appropriate technology for dose assessment. Inexpensive, passive, integrating dosimeters that use optically or thermally stimulated luminescent materials are commonly used. However, these dosimeters fail to provide information about the temporal delivery of radiation dose and the energy of the radiation. A number of projects are underway which are aimed at overcoming these deficiencies.

Environmental Radionuclide Tomography

Detection systems that are under development which would enable the positional sensing of positional radionuclide distributions radiation spectra in the environment in, which would be useful for assessment of contaminated sites and for decommissioning work. A method has been developed which uses measurements conducted at different angles to extract radionuclide concentrations as a function of depth. An extension of this method using positional sensors would result in three-dimensional measurements of environmental contaminations. This is of great interest, as rapid assessments are of interest in the case of accidents and nuclear terrorist events, and for decreasing the costs of decontamination and decommissioning projects, of which half are related to measurements of radioactivity. The study of minimum detectable concentrations, and verifying environmental levels of radiations for acceptable site "cleanup" for restoration and decommissioning actions are also being pursued.

Applied Environmental Radiation Measurements Laboratory

A new facility has been established which focuses on the measurement of small amounts of radiation in the environment and in laboratory samples. Unique, practical capabilities to solve actual industrial, medical, nuclear power, and national laboratory radiation safety challenges are to be developed through applied research. A variety of specific projects, relating to nuclear facility decommissioning, nuclear power plant emissions verification, geological research, radiotracer experiments, responses to radiological terrorists events, and the clean-up of contaminated environments are possible. Capabilities include alpha spectroscopy, portable and laboratory gamma and X-ray spectroscopy with HPGe and NaI, integrative and temporal radon and radon progeny measurement, and thermoluminescent dosimetry. Experiments are being developed for comparing experimental and simulated models of interest to radiological engineers

Radioactive Materials Transportation Risk Assessment

RADTRAN is the international standard code for transportation risk assessment. Enhancements now under investigation include incorporatino of uncertainty, mapping to a GIS or GoogleEarth system, an international routing code, and two-dimensional plume representation.

Disposal of Radioactive Waste

Preparation of an Environmental Impact Statement (EIS) for disposal of greater than Class C radioactive waste. The project includes performance assessment, facility design, determination of worker and public exposure, and transportation risk assessment.

Detection of Systems Illicit Nuclear and Radiological Materials

Illicit nuclear materials for atomic or nuclear weapons or for use in radiological dispersive devises (dirty bombs) have become of great national interest since September 11. This research project has as its goals the investigative of optically stimulated and thermally stimulated materials for use to detect such materials through the integration and read-out of signals in unique ways. New materials with specific temporal properties are also being investigated. The ultimate goal is a system that would be inexpensive enough to enable 100% monitoring of shipping containers.

Detection of Concealed Conventional Bulk Explosives

Several different neutron-based methods for detecting explosives are possible, all based upon detection of either the excess nitrogen or characteristic hydrogen, carbon, oxygen, and nitrogen ratios found in explosives. This project has as its goals the investigation of several new approaches, as well as the combination of existing approaches for improved sensitivity and specificity. Experimental facilities using neutron generators are being designed and constructed. In addition, simulations being performed to fully characterize the interrogation of objects and the environment. The simulations should lead to an understanding of the best approach for the detection of explosives. The problems of land mines, improvised explosive devices, car bombs, and large amounts of explosives held in shipping containers are each somewhat different and interesting challenges.

Radioactive Waste Management

This research program includes research on all aspects of the "back-end" of the nuclear fuel cycle, including: design and evaluation of nuclear waste forms, corrosion of spent nuclear fuel, colloid transport of actinides, performance assessment of nuclear waste repositories, far-field migration of radionuclides and the use of natual analogues to evaluate the long-term behavior of radionuclides in the environment.

REM Faculty:

Kimberlee Kearfott, Alex Bielajew, Rodney Ewing

Adjunct Faculty:

Ruth Weiner, Mike Flynn, Randall Ten Haken

REM Labs:

• Radiological Health Engineering Laboratory
  http://www.ners.engin.umich.edu/rhelab/
• Radiation Effects & Radioactive Waste Management Group
  http://www.geo.lsa.umich.edu/relw/
• Department of Radiation Oncology
  http://www2.med.umich.edu/departments/radonc/