According to SSM Health, nuclear medicine allows physicians to visualize the body on both the molecular and cellular levels. It involves tracking small amounts of radioactive materials as they work through the bloodstream.
Chief of Nuclear Medicine and Molecular Imaging and program director of the University of Wisconsin Nuclear Medicine Residency Dr. Steve Cho said the first patient was treated for thyroid cancer using radioactive iodine around 1940. In the past 10 years, nuclear medicine and molecular imaging have really taken off, leading to new developments in cancer treatments.
There are two main types of imaging in nuclear medicine — anatomic and functional. An example of anatomic imaging is a computerized tomography scan, which shows the shape or size. Functional imaging, such as a positron emission tomography scan, shows functionality within the area.
PET imaging uses fludeoxyglucose, which can tell what organs and tumors use glucose, a type of sugar, as a fuel, Cho said. It’s a common way to image cancer to determine whether it’s present or not. It’s especially important for determining if a tumor is cancerous or benign.
Theranostics, a field within nuclear medicine, is when radiopharmaceuticals are injected into the vein to bind to the cancer cells, Cho said. In terms of diagnostics, this shows whether the tissue is a live or dead mass. Treatment consists of a modified version of that radiopharmaceutical which targets the cancer cells internally. After targeting the cell, the treatment gets enveloped by the cancerous cells.
UW assistant professor of pharmacy and Radiopharmaceutical Production Facility Manager Scott Knishka said theranostics is different from radiation oncology because it can precisely target the cancer from within the body. Radiation oncology, while precise enough to target certain parts of the body, must be administered from outside the body. This has negative side effects, such as hair loss and redness in the area. By injecting the radiopharmaceuticals internally, patient harm is reduced.
Red blood cells are the rate-limiting factor that determines the dosage size for each patient, Knishka said. Since the body can only produce so many red blood cells in a limited time, it’s important to give the correct dosage.
Knishka said one of the major concerns is how the treatment sometimes goes into the salivary glands. This causes dry mouth and difficulty swallowing, speaking and eating.
“In the future, these theranostics that we’re talking about [are] going to explode,” Knishka said. “They are exploding right now and getting new and different types of isotopes to attach that have different types of radiation that’s much more lethal is going to be the future.”
Most current treatments focus on using beta radiation, which is when electrons shoot out to deliver the radiation, Knishka said. New research is looking into alpha radiation, which is as small as a helium atom’s nucleus — 1.67824 femtometers, according to the University of Stuttgart. While it doesn’t go as far as beta radiation, it’s much more lethal, so fewer doses are needed.
Many people are wary of radiopharmaceuticals and radiation therapy because of how dangerous it can be and the unfamiliarity it holds. To combat these worries, Cho said they take precautions when using nuclear imaging.
“We try to minimize how frequently they need to get [exposed], but we try to balance the medical need versus getting an excessive number of scans,” Cho said. “A vast number of these treatments are outpatient, despite being a higher dose.”
Radiation safety is physicians’ priority and they have a division that works on educating patients and doctors in safe practices, Cho said.
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The amount of radioactivity is pretty low during scans. Cho said the chemicals used for PET scans are in such low doses that they clear out of the body within 10 hours. To decrease the amount of time in the body, Cho said he encourages patients to hydrate and urinate regularly after the treatment.
Cho said his biggest concern is the accessibility of these drugs. The supply chain and logistics of delivering the medicine are complicated. One of the steps is a Food and Drug Administration clearance for production. This even decreased abundance for a while, reducing patient accessibility.
This booming industry is not prepared for the bandwidth physicians need to provide. Currently, only two facilities in Wisconsin — Northstar and SHINE — are able to produce and deliver these drugs, Cho said.
Another big barrier is the shelf-life of these drugs. Since the drugs have a short lifespan of about six days, it’s crucial that delivery and use happen quickly. If the drug is unusable, proper disposal techniques need to be taken. The drugs also require proper storage to slow decay time, Cho said.
Knishka and Cho both work with students in the UW pharmacy program and encourage anyone to get involved. Nuclear medicine is not a well-known field, but it’s growing and innovative for patient care. There’s a large need for young, bright people to get into this field, Cho said.
“It’s an exciting field with a lot of new opportunities that are coming about right now and it’s an exciting time to be a part of it,” Knishka said.
