dosimetry Archives

29 Aug 2024

Cancer Treatment, Nuclear Medicine Versant Physics 0 comment

Celebrating the Achievements of Dr. Darrell R. Fisher: A Journey of Scientific Excellence

Earlier this year, the Columbia Chapter of Health Physics Society and the Georgian Health Physics Association nominated Dr. Darrell R. Fisher for the 2024 Distinguished Scientific Achievement Award of the Health Physics Society (HPS). Fisher is a nuclear medicine physicist with Versant Medical Physics and Radiation Safety. He received the Distinguished Scientific Achievement Award in July 2024, during the 16^th International Congress of the International Radiation Protection Association and 69^th HPS Annual Meeting in Orlando, Florida. The award recognized Dr. Fisher’s scientific contributions over a career spanning more than five decades in applied radiation safety sciences, including internal dosimetry, radiobiology, radiochemistry, and design and testing of radiopharmaceuticals and medical devices. His innovative research has led to numerous significant advancements in the applied radiation health sciences.

Discoveries in Chelation Therapy and Radiotoxicity

One of Dr. Fisher’s early discoveries was identifying the toxicity and congenital birth defect teratogenicity of the heavy-metal chelating agent CaNa₃DTPA compared to the non-toxic ZnNa₃DTPA. This research showed the importance of maintaining cellular zinc and manganese availability during critical growth periods to ensure uninterrupted cell division. His work was instrumental in enhancing the safety and effectiveness of emergency decorporation therapy for nuclear workers accidentally exposed to plutonium, neptunium, and americium. By establishing the safety of ZnNa₃DTPA, Dr. Fisher’s work paved the way for safe and effective treatments after actinide contamination events, significantly impacting emergency response protocols and worker safety in nuclear industry.

Advances in Applied Microdosimetry

Dr. Fisher performed the first microdosimetry calculations for plutonium-238 and plutonium-239 in beagle dog lung tissue specimens. His research disproved the “hot particle hypothesis” claimed by Thomas Cochran and Arthur Tamplin; Fisher showed that their hypothesis could not be supported by dosimetry or radiobiology. Fisher described the fundamental science underlying relative biological effectiveness (RBE) relationships between alpha-particle dose and two critical biological endpoints: cellular mutation and primary DNA damage. This work demonstrated that varying the specific activity and spatial geometry of plutonium microsphere sources could result in vastly different biological outcomes at constant absorbed dose. These findings were pivotal to better understanding radiation effects at the microscopic level, influencing safety standards, and advancing what would later become new cancer treatment approaches with alpha-emitting radionuclides.

Innovations in Cancer Treatment

Dr. Fisher was an early proponent of short-lived alpha emitters such as radium-223 and actinium-225 for cancer treatment. He performed the first cellular-level microdosimetry calculations for alpha-emitter-radiolabeled monoclonal antibodies used in cell-targeted radioimmunotherapy. His pioneering work in developing treatment-planning dosimetry for clinical radioimmunotherapy supported the high-dose treatment of relapsed lymphoma, leukemia, and multiple myeloma patients. In the laboratory, he helped to develop and test several innovative alpha-emitter complexing agents, including macrocyclic cages and nanoparticle delivery constructs for next-generation therapies.

Contributions to Uranium Toxicology

Dr. Fisher’s assessments of dosimetry and health effects from uranium intakes led to a modified biokinetic model for inhaled uranium hexafluoride compounds. His research provided crucial insights following the Sequoyah Fuels accident in Oklahoma, where workers were exposed to uranium hexafluoride. Dr. Fisher’s model improved the understanding of uranium’s behavior in the body, leading to better understanding of uranium toxicity.

Pioneering Work in Radionuclide-Polymer Composites

Dr. Fisher conceived, designed, patented, and tested novel radionuclide-polymer composites employing insoluble crystalline yttrium-90-phosphate microspheres administered in a thermo-reversible hydrogel delivery matrix. This innovation has enabled direct interstitial therapy of nonresectable solid tumors, providing new avenues for cancer treatment in both humans and veterinary animals. Precision radionuclide therapy by direct intra-tumoral injection maximizes therapeutic ratios, a key measure of treatment safety and efficacy. His work has enabled highly efficient delivery of radiation to tumors, minimizing damage to surrounding healthy organs and tissues and associated side-effects of radiation therapy.

Enhancing Patient Safety in Nuclear Medicine

Dr. Fisher helped develop and published practical methods for patient-specific dosimetry to characterize the severity of inadvertent radiopharmaceutical extravasations in diagnostic and therapeutic nuclear medicine. Fisher has specialized in medical internal radiation dosimetry, an essential element of managing patient safety and improving therapy outcomes.

Lifelong Commitment to Radiation Safety

Darrell Fisher’s journey in health physics began in 1973 as an undergraduate research assistant at the University of Utah’s Radiobiology Laboratory. His early research on extracting americium-241 from skeletal surfaces in live mice laid the foundation for his future contributions to radiation safety and radiobiology. Over the years, his work has led to significant advancements in understanding and mitigating the effects of radiation exposures in medical and occupational settings. His dedication to the field is evident in his continuous efforts to improve safety standards, develop innovative treatment methods, and educate future generations of health physicists.

The 2024 Distinguished Scientific Achievement Award recognizes Dr. Fisher’s commitment to scientific excellence and discovery for work that not only advances scientific knowledge but also improves patient care and radiation safety. His diverse contributions to the field of applied radiation safety sciences, in collaboration with highly respected research associates and colleagues worldwide, have been impactful. His innovative research, spanning over 50 years, has led to significant advancements in worker safety, dosimetry and microdosimetry, radionuclide therapy treatment planning, direct interstitial treatment of inoperable tumors, and patient safety in nuclear medicine.

18 Dec 2023

Large size motorized 3D water phantom system for dose distribution measurement of radiation therapy beams in real daily routine practice used as a part of quality control of radiation therapy.

Cancer Treatment, Dosimetry, Nuclear Medicine, Radiation Therapy, Uncategorized Versant Physics 0 comment

What’s Inside Matters Most: Internal Dosimetry

Medical physics has been an integral part of medicine and healthcare over the greater part of the last century. Applying physics theory, concepts, and methods, scientists have created patient imaging, measurement, and treatment techniques that revolutionized the medical world. One product of medical physics has been the evolving specialty called radiopharmaceutical dosimetry, the calculation of absorbed dose and optimization of radiation dose delivery in cancer treatment. Today, we address internal dosimetry, the subset of medical physics that aims to optimize treatment and protect the patient from any undesirable side effects.

What is internal dosimetry?

Dosimetry is the measurement of radiation energy imparted to body organs and tissues. Radionuclides emit beneficial ionizing radiation that is useful for both diagnostic imaging of various diseases as well as for cancer treatment. Thus, medical internal dosimetry is the assessment of internal radiation dose from incorporated radionuclides associated with such life-saving radiopharmaceuticals.¹ Radiation dose is the amount of energy imparted by radiations emitted during disintegration of radioactive atoms that constitute part of the radiopharmaceutical chemistry. Dose to organs of the body is quantified per unit mass (or weight) irradiated tissue. Dosimetry provides the fundamental quantities needed for several important purposes, including record-keeping, radiation protection decision-making, risk assessment, and cancer-treatment planning.² The purpose and objective is to optimize medical benefit while minimizing potential radiation damage to body cells, tissues, and organs.

Dosimetry is a complex physical and biological science. Internal dosimetry provides critical information needed to better understand the biological mechanisms governing radionuclide uptake, translocation, and excretion from the body. The radiation dose imparted depends on the type, amount, and distribution of radionuclides, as well as specific nuclear properties, such as energy emitted.

Internal dosimetry differs from “external” dosimetry, which deals with the radiation dose from sources outside the body. Devices such as dosimeters measure external dosimetry directly, while internal dosimetry relies on indirect methods of radioactivity inside the patient using bioassay and imaging measurements.³ Bioassay is the measurement of the activity or concentration of radionuclides in biological samples. Samples can include urine specimens, feces, blood, or breath. Imaging techniques, such as whole-body counters or gamma cameras, can detect the radiation emitted by the radionuclides inside the body. This helps to provide information on their location and quantity.¹

When is internal dosimetry used in healthcare?

Internal dosimetry mainly benefits patients who receive radionuclide therapy, a treatment that involves administering radioactively labeled proteins, such as monoclonal antibodies, to target specific types of cancer.³ It also helps to evaluate and account for unique patient variations in biodistribution—the way that different subjects respond to treatment. Internal dose assessments analyze radionuclide behavior in both normal (healthy) organs, as well as tumors. For example, imaging measurements provide physicists with important information to determine tumor uptake, retention, and clearance. In doing so, administered activity can be tailored according to patient health status, age, size, sex, and basal metabolic rates.

How does internal dosimetry produce useful data?

The main challenge of internal dosimetry is to track and follow the uptake, redistribution, metabolism, and clearance of the administered radiopharmaceutical inside the body over extended time periods after administration.⁴ Tracking sometimes involves mathematical modeling to describe the absorption, distribution, metabolization, and excretion of radionuclides by the body. Biokinetic models may be developed from the study of population groups, knowledge of radionuclide behavior in different organs, and the unique chemistry of each radiopharmaceutical. Biokinetic models incorporate mathematical compartments representing a particular organ or a tissue, and descriptions of the transfer rates that reflect the movement of radionuclides from one body compartment to another.¹

Summary

Internal dosimetry is an important tool for radiation protection, especially in the fields of nuclear medicine, occupational health, and environmental monitoring. Dosimetry helps to customize or personalize nuclear medicine in cancer patients. In a broader sense, internal dosimetry is also applied to occupational and environmental health to prevent or reduce the exposure to radionuclides, by providing information on the sources, pathways, and levels of intake, and by suggesting appropriate measures, such as respiratory protection, contamination control, or dose limits. Internal dosimetry can also help to verify the adequacy of workplace controls, to demonstrate regulatory compliance, and to provide medical and legal evidence in case of accidental or intentional exposure.

Special software tools have been developed for the clinical nuclear medicine setting to facilitate medical imaging and calculate internal doses.

QDOSE^®Multi-purpose Voxel Dosimetry (Personalized Dosimetry in Molecular Radiotherapy) is a complete, one-stop solution software for all internal dosimetry needs with multiple parallel workflows. With USFDA 510(k) clearance granted in August 2023, QDOSE^®has proven its quality and compliance. To learn more, visit our QDOSE^®webpage or schedule a meeting with our team.

Sources

Sudprasert W, Belyakov OV, Tashiro S. Biological and internal dosimetry for radiation medicine: current status and future perspectives. J Radiat Res. 2022;63(2):247-254. doi:10.1093/jrr/rrab119
Bartlett R, Bolch W, Brill AB, et al. MIRD Primer 2022: A Complete Guide to Radiopharmaceutical Dosimetry. Society of Nuclear Medicine & Molecular Imaging; 2022.
Chapter 7 External and Internal Dosimetry. Accessed November 15, 2023. https://www.nrc.gov/docs/ML1121/ML11210B523.pdf
What is Internal Dosimetry – Definition. Radiation Dosimetry. Published December 14, 2019. Accessed November 16, 2023. https://www.radiation-dosimetry.org/what-is-internal-dosimetry-definition/

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06 Oct 2021

Odyssey Personnel Dosimetry module dashboard

ALARA, Odyssey Software, Personnel Dosimetry Versant Physics 0 comment

Odyssey “How To” Series: Personnel Dosimetry Module

Join us for an interview with our Odyssey Implementation Analyst Katelyn Waters, where we discuss how to carry out certain functions of the Personnel Dosimetry module and answer some of your frequently asked questions.

Odyssey is a radiation safety software suite designed to help RSOs, EHS managers, and Radiation Safety Specialists manage affordable and efficient programs.

KB 00:10: Welcome to Part 1 of our Odyssey how-to series, where we highlight some frequently asked questions about the cloud-based radiation safety software suite and its application in real-world radiation safety programs. Over the next 12 weeks, we’ll be addressing each of Odyssey’s modules, and breaking them down to give a better idea of how they work. My name is KB, and today I’m joined by Odyssey Implementation Analyst Katelyn Waters to discuss the Personnel Dosimetry Module. Thanks for joining me, Katelyn!

Katelyn 00:37: Thanks KB, I’m happy to be here and hopefully we can help answer some of the frequently asked questions that we get for the Personnel Dosimetry module in Odyssey.

KB 00:46: So, the personnel dosimetry module is a key feature of the Odyssey platform. It features customizable widgets and reporting tools that help RSOs and EHS professionals managing a badge program do so in a very efficient way. But how exactly is dosimetry data made available in the module?

Katelyn 01:05: That’s an excellent question, and one of the first that we get whenever we are doing different demonstrations of the software. So, personnel dosimetry does support data from any vendor, but it is primarily designed for Mirion and Landauer. So what it actually does is the software uses a login to either AMP for Mirion or MyLDR for Landauer to view and import that dosimetry information into your account. And so this import happens automatically, we set it up to be daily for Mirion and monthly for Landauer, and so everything’s going to be automatically pulled into the software for you.

KB 01:43: If I have multiple dosimetry accounts can I use this module to manage them?

Katelyn 01:48: Yeah, absolutely. So, it is designed to help aid in the management of multiple accounts. So, whether those accounts are all through one vendor, being Mirion or Landauer, or if they’re from both vendors, this is very beneficial for managing those. You can change the dashboard, that’s what we’re currently looking at here for the module, and this dashboard is a quick at a glance view of your dosimetry account. And you can change what account you’re looking at from this first dropdown menu here that I’m hovering over currently, and you can also change it to look at specific locations or subaccounts, and that’s from the second dropdown menu here.

Additionally, we also have something called a Common Wearer Profile, and what that does is it’s going to combine dosimetry information from more than one account. So if you have a wearer that has a badge from both vendors, or maybe they have two badges that are under different locations or subaccounts, you can combine that information into one profile to make viewing that dosimetry history a lot easier for that wearer.

KB 02:50: So, if I wanted to add or remove any of those multiple badges on my account, can I do so from within Odyssey?

Katelyn 02:57: Yeah, great question. So, the actual addition or editing of any of the badges for wearers for your program will still take place in your vendor portal, whether that’s Mirion, Landauer, or another party. So this particular module is designed to give you some additional features that aren’t available in those vendor portals. Some of those features include ALARA reporting, easy form 5 access, different alerts and reminders, shipping, different management for some of those high-level activities that you’re going to need to do for your program.

KB 03:31: I see. What about this dashboard? Is it possible to change any of the information that’s displayed here?

Katelyn 03:38: Yes. I definitely recommend that when you start utilizing this module in the software that’s something you do right away because it makes it very beneficial for you, and you can do that by selecting this gear icon here, it’s going to take us to show us all of the settings. So each of these boxes we refer to as a widget, and each widget has its own settings for what you want to view on your dashboard. A good example here is the Recently Viewed widget in the top right-hand corner. I have what I want to see available for selection with these checkboxes, I have some drop-down menus for the number of things that I want to see here for the Read activity widget I can choose the time period… so depending on what it is they each have their own settings for these particular widgets, and that way you can really make it for what you need to see for your program.

In addition to that, you can also click and drag things to more prominently display them. So, if I want to have this graph of Read Activity–these are doses that are coming in each day–I can put this at the very top so I can see that a more prominent position. You can also hide things if they aren’t useful to your program. So, say you don’t want this recently viewed widget, I can select the eye icon and hide that and if I were to save these settings it would remove that from my dashboard. So, it’s very customizable.

KB 04:59: You mentioned read activity. Is there a place that I can see who hasn’t read their badge?

Katelyn 05:06: Yeah, so we have a query data section which I can actually go to and show you here. And this section allows you to do some really in-depth searches on your dosimetry data. You can choose to select what you want to search for, so with your example, I would go and search for different personnel, and ones that don’t have a badge reading. And then I come down to this section where it says Include or Exclude and I can choose things that I want to either include in my search or exclude from my search. And for us today, I’ll go ahead and add in an inclusion statement to include people for the current account that we’re looking at, just as an example, and then I can exclude people who have readings and we will only be left with those who do not, so I’ll go ahead and exclude people who have a reading for this year by putting in the date of January 1^st.

So we can hit this play button here and it’s going to then search through all of your dosimetry records and give you the corresponding data for your filters. Once it does so, you have a table result at the bottom. And so, the format of this data is a little odd due to the fact that we’re looking at primarily, or not primarily, exclusively demo data. So you can see the employee IDs are very long. But this is what the format of that table would look like for you, just have your own dosimetry data displayed in it.

And these are linked to other areas of the software. So for these wearers, I can actually select them to go to their profiles, and in addition, we have a list of contact information here that if you were to select this mail icon for it would actually put all of these people into a mailing list for you so you can easily communicate with them. So if we do want to reach out to this group and say hey, you need to please read your badge for 2021, you can do so by this easy feature there.

KB 07:02: Well that seems pretty easy to do. Is there any way for me to receive notification of individuals with high doses?

Katelyn 07:10: Absolutely. So that is actually one of my favorite features that we have added into the Personnel Dosimetry module and it exists in this reporting section. So I’ll go ahead and select that and we’ll take a look at that.

The reporting section has a tab called ALARA. The module has the ability to add in different custom ALARA thresholds. For this particular demo dosimetry account, we have two thresholds added in. I’ve added in an ALARA 1 and an ALARA 2. These are both quarterly thresholds but you can also have them trigger on a single dose, they can be monthly, quarterly, or annually. So, you have a variety of options there. They can also be scoped to particular badge regions that a badge is assigned to. Since these are quarterly thresholds, this next filter of the period gives me the option to choose a quarterly time period but that will change depending on your threshold. And if I do put in last quarter as an example and select run report, what that’s going to do is give me a table of results of individuals that have surpassed that threshold for the chosen time period. So we have these three demo people who have surpassed the ALARA 1 Threshold, and then one person additionally also surpassed the ALARA 2, so this table is really nice because if they did surpass other thresholds it will let you know that. So if you only want to follow up on the higher of the two you absolutely can do that.

It will tell you the time period that we’re covering currently, and then the cumulative dose for that time period, and then the stage that you’re at in the process. So this will allow you to email each of these individual wearers either notification that they went over this dose threshold or a questionnaire – that form that they actually get sent is completely customizable – and the wearer will receive that via email. Once they do, they will open and view that, if they have any questions they can fill that out, it requires a signature and dates it for them automatically, and then that gets sent back to Odyssey. Once it does get sent back, this pie chart progresses and shows you where this process is. So it will change to being yellow for “waiting for RSO response.” So if you’re an RSO, a radiation safety representative, you can come in here, review that questionnaire, and the responses, and sign off on that to complete the process.

And to get back to your initial question about alerts for these items, throughout this entire process you’re going to be receiving in-software alerts which can optionally be email alerts as well. So when a wearer initially goes over the threshold, any of these thresholds you have set up, you’re going to get an alert that looks like a post-it note like one of these. And then when they fill it out they also will trigger an alert and it’ll let you know they have it filled out so that way you can come in and review that as soon as possible. And so you’re always going to be notified of each stage of the process there as this progresses.

KB 10:07: Well that all sounds great! Thanks, Katelyn, for helping us address some frequently asked questions about Odyssey’s Personnel Dosimetry module. Join both of us next week for part 2 where we’re going to be talking about the inventory tracking module and its ability to assist with tracking radioactive materials in your radiation safety program.

Katelyn 10:26: Thanks, KB.

Schedule an in-depth demo with our Odyssey team to discuss how the software can assist you with your radiation safety management needs, or visit our website to learn more about Odyssey’s radiation safety modules.

Tag: dosimetry