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How different are human models from spherical cows (from the perspective of radiation interactions)?

Computational models of the human body for use in estimation of radiation dose have improved greatly with computational capabilities over the decades. Models have improved from simple geometric shapes representing the human body (#sphericalcow) to physiological models based on CT-based scans of actual humans. As advances have been made to more accurately model the behavior of radiation in more physiologically realistic models of the human body, the better these models can inform radiation regulation and better associate radiation risks and effects.

THE EVOLUTION OF COMPUTATIONAL PHANTOM MODELS. REPRODUCED FROM: LEE, C. (2015). DOSIMETRY TOOLS FOR MEDICAL RADIATION STUDIES. RADIATION EPIDEMIOLOGY & DOSIMETRY COURSE.

When conducting the update from the Environmental Protection Agency’s Federal Guidance Report No. 12: External Exposure to Radionuclides in Air, Water, and Soil (1993) to Report No. 15 (2019), Dr. Shaheen Dewji sought to quantify the differences between older generation mathematical stylized phantoms used in Report No. 15 with the latest models offered by the International Commission on Radiological Protection in their published voxel phantoms in Publication 110 and their pediatric counterparts. Results from Monte Carlo radiation transport simulations of a phantom submersed in an infinite cloud of gamma radiation demonstrated the differences in the stylized and voxel models, which were reported by Dr. Dewji and colleagues for the adult male, adult female, and pediatric series (newborn, 1-, 5-, 10-, 15-year old ages), highlighting limitations for differently defined organ sizes, organ resolution vis-a-vis the thickness of thin-walled organs smaller than the voxel resolution, and energy dependence of the source radiation to penetrate the body to reach internal organs. Dr. Dewji and TAMU RED² researcher, Thomas Cuthbert, under a scientific collaboration with the National Cancer Institute’s Division of Cancer Epidemiology & Genetics Radiation Epidemiology Branch scientists, Dr. Choonsik Lee and Keith Griffin, sought to quantify why these fundamental differences were observed. Overall, it was observed that the 100 keV-5 MeV range of gammas in the cloud yielded comparable results between the two phantom generations (within 5%-20%). But what were so different about these two generations of phantom models that explained variations in results (rather than just take them at face value)?

STYLIZED PHANTOMS (LEFT) AND VOXEL PHANTOMS (RIGHT).

In their most recent publication, RED² and NCI investigated the guts of the details, literally. In their recently published investigation in the Journal of Physics in Medicine and Biology, “Stylized versus voxel phantoms: a juxtaposition of organ depth distributions,” simulations were conducted to quantify the organ depth distributions in each of the phantom models for adult and pediatric models, to determine the effect of organ depth distribution to the exterior surface of the body in 8 vector planes: antero-posterior, postero-anterior, left and right lateral, rotational, isotropic, cranial and caudal directions.

A COMPARISON OF ORGAN DEPTH DISTRIBUTIONS BETWEEN THE STYLIZED AND VOXEL PHANTOMS MODELS FOR THE 15-YEAR-OLD’S KIDNEYS. NOTICE THE ROLE OF THE STYLIZED PHANTOM POSTURE (THIGHS ATTACHED) COMPARED TO THE CT-BASED VOXEL MODEL.

The resultant organ depths for both series were plotted as distributions; available are 24 organs and 2 bone tissue distributions for each of 6 phantom ages and in each of the 8 directional geometries. Quantitative data descriptors (e.g. mean and median depths) were also tabulated. The entire dataset of organ depth distributions and their data descriptors were published quantifying all the distributions. As models of human phantoms continue to evolve, there is still utility in past generations of phantoms. If a simpler phantom model yields comparative results within an acceptance criteria for a specific end-use, then why do we need an overtly defined model? Each generation of phantom still has utility, and as voxel and newer generation hybrid phantoms become increasingly utilized beyond radiation protection applications for nuclear medicine (where high resolution physiology is essential), then clear quantification helps explain generational variations of computational models of radiation dose.

In essence: All models are wrong, some are useful… and more useful, if we are able to quantify our known unknowns.

RED² STUDENT RESEARCHER, THOMAS CUTHBERT, PRESENTING HIS RESULTS TO THE STATE OF TEXAS CHAPTER OF THE HEALTH PHYSICS SOCIETY.

Thomas Cuthbert graduated with his B.S. in Nuclear Engineering and minor in Radiological Health in Spring 2019 from TAMU and is currently pursuing his graduate studies in Medical Physics at UT Health – San Antonio.

Read the full details of his study here.

Professor Dewji joins American Nuclear Society delegation to Nuclear Energy Agency Workshop to discuss “Reasonableness” in radiation protection

On January 13-15, 2020, Dr. Shaheen A. Dewji of the Department of Nuclear Engineering at Texas A&M University joined the esteemed American Nuclear Society (ANS) delegation to discuss the concept of “reasonableness” in the radiation protection philosophy of “ALARA” (As Low as Reasonably Achievable) at a workshop held by the Organization for Economic Co-operation and Development (OECD) Nuclear Energy Agency (NEA) in Lisbon, Portugal. The objective of this workshop, entitled, “NEA Workshop on Optimization: Rethinking the Art of Reasonableness”, was to identify a regulatory and practical approach for assessing radiological protection circumstances, and for developing, with appropriate stakeholder participation, the best radiological protection choices under the prevailing circumstances.  Workshop participants came from a wide variety of perspectives regarding effects of radiation exposure, radiation protection regulation and the implementation of that regulation from a selected invited group of international scientific and policy subject matter experts.

Radiological protection decisions are informed by science, but are based on judgement as to what level of protection is “reasonably achievable”. The science of radiological protection continues to evolve and advance, but seems not likely to quickly and definitively resolve the issue of what level of exposure can cause harm. However, the need to take radiological protection decisions remains, and input is needed to help to assure that protection choices are reasonable. Taking a broad view of assessing and balancing responses to the risks associated with any particular prevailing circumstance in practice can be very difficult to achieve.

The ANS delegation included past, present, and future ANS Presidents, in addition to esteemed subject matter experts in radiation protection sciences, regulation, and policy.

ANS delegation with (left to right): Tony Brooks (Lead Scientist of Department of Energy Low Dose Program, University of Washington – Ret.); Mary Lou Dunzik-Gougar (Idaho State University; American Nuclear Society President-Elect); Paul Locke (John Hopkins University); Marilyn Kray (Exelon Corp.; American Nuclear Society President); Shaheen Dewji (Texas A&M University; American Nuclear Society Radiation Protection and Shielding Division); Alan Waltar (Former American Nuclear Society President, Pacific Northwest National Laboratory, Ret. and former NUEN Department Head at TAMU); Amir Bahadori (Kansas State University; American Nuclear Society Radiation Protection and Shielding Division).

Under the supervision of Dr. Dewji, a series of curated case studies evaluating the application and interpretation of “reasonableness” were presented on each of the topics developed by Texas A&M Nuclear Engineering Undergraduate Students with selected subject matter experts from the American Nuclear Society:

Case 1: Appropriate Radiological Risk-Based Limitations for a Geological Repository Jordan Hillis (with Rob Hayes, NCSU; Jim Conca, UFA Ventures, Inc.; Alan Waltar, PNNL-Ret.)

Case 2: Safe Drinking Water Regulations Andrea Macias, Estefany Martinez (with Dan Stout, TVA)

Case 3: Implications of Evacuation at Fukushima Megan Frisbey, Alex de Rochemont (with Alan Waltar, PNNL-Ret.)

Case 4: Zahn’s Corner Middle School Closure Wyatt Smither, Morgan Ho (with Craig Piercy and John Starkey, ANS)

The presentation was prepared by Dr. Dewji and delivered to the Workshop audience on behalf of the ANS delegation by President Marilyn Kray. The ANS delegation is continuing to advance the discussion of “reasonableness” in the USA in the purview of resurrection of the Department of Energy Low Dose Research Program, which has impacts in all areas of Nuclear Engineering (power, public health, emergency response, defence, medicine, risk communication).

The workshop was organized by the NEA’s Committee on Radiological Protection and Public Health (CRPPH) event was hosted by the Service de Radiologie, Institut Portugais and held at the Portuguese Institute of Oncology.

Also in attendance were esteemed leadership from the NEA, Director General, William Magwood, IV, and Head of the Division of Radiological Protection and Human Aspects of Nuclear Safety, Yeonhee Hah.

Dewji (left) and Magwood (right).

Dewji (left) and Hah (right).

RED² NSSPI student evaluates exposure rates for triage following fission product release events

Check out our latest publication in the Health Physics Journal co-authored by RED² and NSSPI Ph.D. student, Ethan Asano. In the event of a radiological incident, the release of fission products into the surrounding environment and the ensuing external contamination present a challenge for triage assessment by emergency response personnel. Reference exposure rate and skin dose rate calibration data for emergency response personnel are currently lacking for cases where receptors are externally contaminated with fission products.

Mathematical skin phantoms were created using surface area and height specifications from International Commission on Radiological Protection Publication 89. Simulations were conducted using Monte Carlo radiation transport code using newborn, 1-y-old, 5-y-old, 10-y-old, 15-y-old, and adult phantoms for 22 photon-emitting radionuclides. Exposure rate coefficient data were employed in a case study simulating the radionuclide inventory for a 17 × 17 Westinghouse pressurized water reactor, following three burn-up cycles.

The resulting data can be used as calibration standards for triage efforts in emergency response protocols resulting in populations with external contamination. This work was conducted under the support of the Centers for Disease Control and Prevention and in collaboration with Oak Ridge National Laboratory.

For further information on radiological emergency response for both members of the public and professionals, check out the CDC website.

ORIGEN-ARP/SCALE 6.3 generated activity inventory for fission products of interest as a function of decay time postrelease following three 1-y burn-up cycles at 14,600 MWd MTU−1 for a 17  17 Westinghouse PWR.

 

RED² Professor, Dewji, receives NSF ADVANCE Scholars Program Award

Congratulations to RED² professor, Dr. Shaheen Dewji, for being selected for the National Science Foundation ADVANCE Scholars Program at Texas A&M University. The ADVANCE Scholars Program is a faculty mentoring program designed to promote and advance the success of tenure-track faculty who have been historically underrepresented at Texas A&M University and in higher education. This Program is anchored in our Aggie Core Values that continuously challenge us to embrace, value, and integrate diversity and inclusion as the roadmap to achieving academic and institutional excellence. As such, the ADVANCE Scholars Program is a key component of our efforts at Texas A&M University to support the recruitment, retention, and academic success of our faculty. Through systemic approaches to increasing their professional advancement, this Program contributes to the development of an exceptional and more diverse faculty.

Participants are afforded access to invaluable academic and professional development experiences to advance their careers as scholars. The Program focuses on cultivating opportunities for personal and professional growth by addressing issues that adversely affect satisfaction, effectiveness, and retention of historically underrepresented groups in higher education. Texas A&M University recognizes that creating a more equitable climate contributes to a positive environment for the students we serve, and the university as a whole.

 

RED² evaluates radiation risk to hotel workers handling contaminated linens from I-131 therapy patients

Check out our latest publication in the Health Physics Journal authored by RED² student, Chase Foreman, which evaluates the external radiation dose to hotel workers handling contaminated bed linens from I-131 therapy patients.

Patients administered I-131 as a part of medical therapy will frequently stay in a hotel during their isolation period to avoid exposing family members. However, dosimetric estimates to hotel workers handling potentially contaminated bed linens due to I-131 radionuclide therapy has not been considered.

In the scope of Foreman’s work, calculations of external dose rate coefficients were conducted for hotel housekeepers handling bed linens used by potentially contaminated by patients administered I-131. Detailed simulations consider both the tissue and material attenuation of radiation through the use of anthropomorphic phantoms, as well as considering the biokinetic body burden to determine the time-dependent excretion of I-131 from the patient’s body.

Foreman graduated with his B.S. in Nuclear Engineering and minor in Radiological Health in Spring 2019 from TAMU and is currently pursuing his DMP in Medical Physics at UT Health – San Antonio.

Dewji Joins Group to Argue for Renewal of DOE Low-Dose Radiation Research Program

Original article: https://nsspi.tamu.edu/dewji-joins-group-to-argue-for-renewal-of-doe-low-dose-radiation-research-program/

October 22, 2019 | By Kelley Ragusa

On September 24, 2019, NSSPI Faculty Fellow and Assistant Professor of Nuclear Engineering Dr. Shaheen Dewji participated in an event organized by the American Nuclear Society (ANS) in which experts were called on to discuss resurrecting the Department of Energy (DOE) low-dose radiation research program with congressional staffers. Dr. Dewji joined ANS Washington Representative Craig Piercy, John Starkey of ANS, Dr. David J. Brenner of Columbia University, and Dr. Antone L Brooks, research professor emeritus at Washington State University and one of the former lead scientists of the low-dose radiation research program from 1999-2008 to argue the importance of the program and call for its resurrection.

group photo

Mr. Starkey, Dr. Brenner, Dr. Dewji, Dr. Brooks, and Mr. Piercy in Washington, D.C. to support the resurrecting of the DOE low-dose radiation research program.

The ANS event also included a webinar open to ANS members titled, “Low-dose radiation: What is the science telling us?” The webinar was a discussion by the group of experts aimed at increasing awareness of the program through discussing the health benefits and highlighting low-dose research and development that the continuation of the program could make possible.

The DOE terminated the low-dose radiation research Program in 2016, but the program has continued to garner support not only from members of the scientific community, but also from politicians on both sides of the aisle. In May, the House Appropriations Committee approved a request by the DOE for $10M in funding to support the restart of the program. On October 18, a bipartisan group of Members of the House Science, Space, and Technology Committee, which included Representatives Bill Posey (R-FL), Dan Lipinski (D-IL), Randy Weber (R-TX), and Brian Babin (R-TX) introduced the “Low-Dose Radiation Research Act of 2019.” If approved by the full Congress, the funding would allow for new research in this area that could incorporate the scientific advances made since the suspension of the program.

While low-dose radiation research has many potential applications for health and safety, the importance of this work for nuclear security lies in the realm of emergency preparedness for and response to radiological or nuclear terrorism events.

“Emergency response guidance and regulation, especially in the purview of emergency preparedness and response, requires an accurate evaluation of the detrimental effects following radiological or nuclear terrorism events involving exposures to members of the public, first responders, or military personnel,” argued Dr. Dewji. Moreover, she stated, “The work proposed under a renewed low-dose program is foundational in evaluating radiation risk informing post-event decision making.”

This work could help decision makers evaluate whether shelter-in-place measures or evacuation is more appropriate. In addition, the impact of the work further informs the development of radiation countermeasures following radiological or nuclear events involving exposures from improvised nuclear devices or nuclear weapons, or uptakes from radiological dispersal devices of improvised nuclear device or nuclear weapons fallout.

Recording radiation: Graduate student enhances interpretability of radiation exposure data

September 6, 2019 | By Hannah Conrad

A radiation warning sign

Kalinowski’s developing computational model will give insight into the health and disease effects of extended, low doses of radiation | Image: IG_Royal/Stock-Getty Images Plus/Getty Images

Radiation is energy traversing space. Little particles shooting through the air that can be utilized as a means of curing cancer or could cause irreparable damage to a person’s health.

Autumn Kalinowski, a graduate student in the Department of Nuclear Engineering at Texas A&M University, is developing a computational model that converts raw data and radiation records from thermoluminescent dosimeter (TLD) badges into more readily useable values for epidemiological studies. As such, her model will produce information that can be utilized to investigate the epidemiological – health and disease – effects of radiation, especially low doses. This ongoing project is part of an internship with Oak Ridge Associated Universities in Oak Ridge, Tennessee.

RED² student, Autumn Kalinowski, is working on developing a model that can translate the raw database information into a format of values that can be more directly applied to epidemiological studies.

“Anyone who works in a nuclear field and is potentially exposed to radioisotopes, be it technicians, reactor operators or people who work in weapons fabrication or national labs, wears a TLD badge,” said Kalinowski.

These badges are scanned and read periodically throughout the year. The information is culminated annually and the total dose of radiation exposure for each individual is sent to Oak Ridge Associated Universities to be input into a massive database.

“This is so that we can go back and look at individuals and see their exposure over time to monitor it and make sure that it is falling within regulatory limits,” said Kalinowski.

Unfortunately, with how it is currently recorded and formatted, the data cannot be effectively applied to epidemiological studies – limiting how much insight and information can be gained regarding the health effects and disease development of prolonged exposure to low doses of radiation.

So, tackling this issue, Kalinowski is working on developing a model that can translate the raw database information into a format of values that can be more directly applied to epidemiological studies. This will not only be a key element in the advancement of nuclear research, but also stands to have a lasting impact on experts and engineers in the nuclear and medical industries at large. With access to real-world, interpretable data, researchers, industry leaders and others can track and investigate how radiation – especially at low levels – effects workers’ health and disease development over time.

As such, her model will also be a vital tool in better understanding radiation and how to keep workers safe in environments in which they are exposed to radioisotopes.

Having received her bachelor’s degree from the department, Kalinowski said that her experience as a nuclear engineering student at Texas A&M has helped her with her internship.

“The nuclear engineering program is really rigorous in terms of the amount of work that you do in your undergraduate and graduate degree. All the classes are super intense, and in order to do well in them, you have to have a strong, motivated work ethic and be willing to put the hours in to get it done,” said Kalinowski. “Learning how to work with tight deadlines and how to juggle priorities really helped prepare me for my internship and make sure I could get everything done while I was on site.”

Kalinowski was introduced to key movers and shakers at Oak Ridge Associated Universities by Dr. Shaheen Dewji, assistant professor in the nuclear engineering department.

“My advice is to talk to your professors and see if they know anyone that they can put you in contact with to start pursuing internships because this experience – that I’m very fortunate that Dr. Dewji helped me find – opened up a whole new world of options for me,” said Kalinowski.