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Xavier Magazine | August 18, 2018

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Life and Half-Life

Life and Half-Life
By France Griggs Sloat

In November 2007, Terry Toepker went to his doctor for a routine physical. Within minutes of diagnosing a heart fibrillation, the doctor packed him off to see a cardiologist, who ordered up two days of stress tests to check for a blocked artery. During the tests, Toepker was injected with 25 millicuries of Technetium-99, a radioactive isotope used so a gamma camera could take pictures of his heart. He was amazed—not only by the pictures but also by the fact that radioactive material was floating around in his heart. So the retired chairman of the physics department with a PhD in nuclear engineering did what any good physics professor with a PhD in nuclear engineering would do: He turned himself into an experiment. “I was radioactive,” he says. “Why not do something with it?”

After the second day’s test, he grabbed the Geiger meter from Xavier’s physics lab and held it to his chest, recording a Gamma ray reading that was off the charts—more than 20,000 counts per second. Knowing the physical half-life—the time it takes for half the atoms of a radioactive substance to dissipate—is 6.01 hours for Technetium, Toepker wondered how long it would take for the isotope to disappear from his body. So he set up a test. His experiment lasted 28 hours and took place on his kitchen table. Every two hours, he took a reading, placing the Geiger meter against his chest and writing down the results. After six hours, the readings had fallen, but by slightly more than half. Then the decline accelerated and by the end of the experiment, Toepker’s body had lost 98 percent of the isotope.

Using scientific formulas, he calculated his biological half-life was 5.43 hours. Combining that with the known natural half-life of the isotope of 6.01 hours, he concluded the actual half-life was 2.85 hours. Toepker wrote up his findings for a report—titled “Life and Half Life” and including a line graph—he’s submitting for publication in a science journal this winter. When asked why he did it, Toepker just shrugs. “It’s the whimsy of a physicist,” he says. “If you’ve got lemon, make lemonade.”

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