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A Meditation on Nuclear Medicine

A visit with Silvia Jurisson, Professor of Chemistry

By LuAnne Roth
Published: - Topics: chemistry nuclear pharmaceutical medicine
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Those of you who didn’t catch Professor Silvia Jurisson at her Saturday Morning Science lecture on March 4th can get a summary here, given by the lecturer herself. Jurisson’s research falls into the area of chemistry called radiopharmaceuticals—that is, pharmaceutical drugs with a radioactive atom attached for use in diagnostic and therapeutic procedures.

In order to contextualize the parameters of her research, Jurisson gives an abbreviated history of nuclear medicine—from the discovery of x-rays in 1895, and of radioactive particles the following year, to the period when scientists began successfully injecting radioactive compounds into a human’s circulatory system in the 1930s and ‘40s to diagnose and treat diseases from thyroid cancer and brain tumors to bone cancer and leukemia. Many of these techniques are still in use today. It is in this broad area that Jurisson’s research falls—exploring the use of radioisotopes for diagnosing disease in humans. For those of you who haven’t spoken the language of chemistry for years, radioisotopes are molecules that have been made radioactive (by adding a radioactive atom). And these little isotopes are crucial to nuclear medicine, both in diagnosing and in treating disease.

Jurisson described a whole range of isotopes that are employed in nuclear medicine. She has been focusing in particular on technetium-99m, which by 1953 had been proven effective in imaging brain tumors. Tc-99m, which resides in the middle of the Periodic Table of Elements, has a half-life of only 6 hours – an index of perishability that makes it difficult to work with, especially for hospitals remote from a nuclear reactor. Fortunately, in 1960 a generator system was developed: a small device about six inches tall and covered in lead that enables doctors to take freshly created Tc-99m from it as needed. This “portable nuclear reactor” will generate the short-lived isotope, which the hospital uses for a variety of diagnostic procedures, for a period of weeks.

Jurisson discusses several factors at play when creating radiopharmaceuticals. In order to design a drug that treats cancer, for instance, you want to use an element that appears naturally in the body—so that when the drug enters the body it will go directly to the designated areas. Unfortunately, most of the radioactive isotopes with good properties for imaging or therapy do not naturally occur in the body. Tc-99m is useful in this respect: it just enters the body, circulates in the bloodstream, and then exits in the urine. By building a molecule around Tc-99m that takes it to a specific part of the body, the doctors can send it where it needs to go. For example, with phosphonate groups attached it has proven invaluable in imaging cancer that has spread to the bone—and with better diagnostic ability than MRI or CT scans. Radioactive iodine when injected goes directly to the thyroid (which needs iodine) and irradiates the area. “This turns out to be our only true magic bullet,” Jurisson explains. “It is the only way so far to cure hyperthyroidism and thyroid cancer that has spread.”

Because Jurisson’s work is so multidisciplinary, she collaborates a great deal with other researchers at MU and other institutions. She has worked with Thomas Quinn, an MU biochemist, on a molecule that binds to melanoma receptors. She is also looking at a peptide called bombesin that seems to target the breast, prostate, and pancreas. If Tc-99m were attached to these, it could prove promising for the diagnosis and treatment of associated cancers.

Thanks to its nuclear reactor, a sizable group of radiopharmaceutical researchers call MU their home. But more are needed, Jurisson reports, to manage the needs of the future. To drum up interest in chemistry, she likes to participate in outreach programs such as MU’s Saturday Morning Science program—a series of free lectures aimed at any person (young or old) who has some curiosity about science.

In addition to her work in nuclear medicine that benefits the human body, one of Jurisson’s ongoing research projects involves trying to solve the problem of long-term storage of nuclear waste—the inevitable by-products of our nuclear era. She works specifically with another isotope of technetium (Tc-99) that has a 212,000-year half-life, a fact that causes many people to be concerned about it eventually seeping into the water supply. With the same isotope of Tc-99m used in cancer treatment, Jurisson has been investigating methods for detecting and separating this radiometal. If successful, this technique could help mediate one risk of nuclear energy production.