Areas of Research
In my work over the years, I’ve ended up wearing a number of different hats, sitting at the intersection of a number of different multidisciplinary fields: chemistry, biochemical engineering, experimental nuclear physics, and nuclear medicine. More recently, this has culminated in my research being currently focused on isotope production, where we transmute atoms of one element into a new, different element, through the use of nuclear reactions — in a very real sense, alchemy! This work has an emphasis on medical applications, and the development of new computation tools to aid in these efforts. These tasks are inspired by a desire to help solve some of the fundamental problems inherent to humanity, namely cancer and other serious disease. Bringing together these different disciplines allows for the development of next-generation, personalized approaches to medical imaging and cancer therapy.
Every year, approximately 17 million nuclear medicine procedures (both diagnostic and therapeutic) are performed in the U.S. alone. Most of the radionuclides currently used for these procedures are produced by low- and intermediate-energy accelerators, e.g., 11C, 18F, 68Ga, 82Rb, and 123I. These accelerators also produce non-medical radionuclides with commercial value, such as 22Na, 73As, 95mTc, and 109Cd. However, the production of radioisotopes for research, industry, and commercial purposes is in short supply. Consequently, through the research necessary to address such deficiencies, it is possible to expand this list of options to include, novel and emerging isotopes, as well as develop alternative pathways for production of established isotopes.
In particular, I specifically focus my work on:
- Production of novel medical isotopes
- Development of intense neutron source capabilities
- Radiochemical purification and separations
- Precision nuclear data measurements
Novel applications are being explored for several radionuclides whose production methodologies are not established, but their production requires accurate, high-fidelity cross section data. Candidate isotopes to meet these needs have been identified based on their chemical and radioactive decay properties, and I have been helping to lead a series of campaigns to perform targeted, high-priority measurements of thin-target cross sections and thick-target integral yields. These studies will serve to facilitate the production of clinically relevant quantities of medical radionuclides.
Currently, I’ve worked to produce, characterize, and use a variety of isotopes, notably 47Sc, 64/67Cu, 66/68Ga, 90Mo, 134Ce, and 161Tb, among others.
99mTc is currently far-and-away the most commonly used diagnostic imaging radionuclide, but diminishing stockpiles have made the search for alternative production pathways a pressing concern. Like 99mTc, many established radionuclides are currently produced in thermal and fast nuclear reactors, which have significant start-up costs and proliferation concerns involved in their commissioning, along with low-purity radionuclide yields.
I have been involved in the development of intense neutron source capabilities - a compact, high-flux DD-fusion neutron generator, and tunable monoenergetic neutron “beams” via Li(p,n) targets. These open up the possibility of high-purity alternative production pathways, which avoid the the co-production of unwanted activities via neutron capture in a reactor.
Following the production of any isotope, purification work must be done to separate the product from the irradiated target, and prepare it for clinical usage. I have worked with a number of radiochemical methods to isolate and purify a reaction product, including radio-HPLC, radio-TLC, solid-phase extraction, and cation-exchange extraction. More recent work has focused on radionuclide labeling via chelate-conjugated biomolecules, following purification, to help bio-targeting of medical radionuclides.
In cases where reaction data has not been experimentally measured, reaction modeling codes are used as predictive capabilities for estimation of this data. However, reaction modeling for charged particle beams remains largely untested, with estimated cross sections often incorrect by more than an order of magnitude, due to a paucity of well-characterized reaction data used for tuning these codes.
I work on producing well-characterized, precision reaction data measurements, using “variance minimization” techniques to reduce the systematic uncertainties which often plague such measurements. Well-characterized data is necessary for improving our reaction modeling capabilities, but also has numerous applications in science and engineering, including
- the design of next-generation nuclear reactors,
- improved radiation shielding design,
- increased efficiency in radionuclide production.