Kira Grogg, PhD, with the NeuroPET CT machine
Kira Grogg, PhD, with the NeuroPET CT machine used to track proton beam therapy treatments in cancer patients

Kira Grogg, PhD, started her research career working on one of the most ambitious and well-known research projects ever conceived—the Large Hadron Collider (LHC) in Geneva, Switzerland.

The world’s most powerful particle accelerator, the LHC consists of a 27-kilometer ring of superconducting magnets that are designed to accelerate protons and ions to a rate approaching the speed of light.

At the LHC, Grogg was part of the team that helped discover the Higgs Boson particle—the so-called “God particle” that had been employed in theoretical physics for years, but remained an unproven entity until 2013.

Taking part in this highly prominent project was rewarding, but Grogg, who was one of thousands of scientists involved in the study, wanted a more hands-on role in her work.

The solution was to transition from large-scale high-energy physics to a more specialized area of medical physics at Massachusetts General Hospital.

“In medical physics I can have a bigger role on any given project,” Grogg explains. “I do miss the dramatic nature of working on the LHC, but the analyses in high energy physics became so specific and narrow that I started to feel too disconnected from the real world.”

In 2011, Grogg came to Mass General, where she is now part of a team working on ways to verify the accuracy and precision of proton beam therapy treatments for cancer patients.

Mass General, which operates the Francis H. Burr Proton Beam Therapy Center, is one of only 20 institutions in the United States to offer proton therapy, a highly specialized treatment for brain, prostate, pediatric cancer and other cancers with clearly defined tumors.

The treatment works by bombarding the tumor with a stream of high-speed protons that kill the tumor cells. Proton beam therapy is designed to target only the affected area, thus reducing collateral damage to the tissue surrounding the tumor. The tricky part is making sure that the protons hit their mark.

The protons are only effective when they hit the tumor at certain target points and at a certain power level. As the proton beam travels into the body on its way to the tumor, it has to pass through bone, skin and muscle, all of which can affect the speed and direction of the beam. Treatment teams can do a pretty good job of calculating the dosage and pathway needed to target the tumor by using a series of complex mathematical simulations, but there is always some uncertainty in the process.

Individual tissues and bone density vary between individuals, and if patients lose or gain weight in between treatments, the position of the tumor can change enough to affect the treatment. Thus, it is not easy to confirm that the proton beam hit the target as intended and the damage to surrounding tissue has been minimized.

Grogg and her colleagues hope to use complementary imaging techniques to make the proton treatments more precise. Using positron emission tomography (PET) scans, she is working to devise a methodology for measuring the impact of each treatment by studying the short-lived radioactive byproducts that result from the beam hitting the tumor. She explains that sending a high-speed beam of protons into the body creates short-lived radioactive isotopes as a byproduct.

By using a PET machine to scan a patient immediately after treatment, it may be possible to gauge the effectiveness of the treatment by charting the distribution and volume of the positron-emitting radioactive isotopes that result from impact. “We want to make sure that we are putting the protons exactly where they are supposed to be,” she explains. “The PET scan can approximate where the dose went. It’s not a direct measurement of the dose, but if we see [positron] activity at the tumor site, we know some protons made it.”

“Our challenge now is to validate our results and to figure out how we can integrate the feedback from PET images into the calculations for treatment. This must be tested if we are to improve the accuracy and effectiveness of this therapy.”

Grogg admits that coming to Mass General was a bit of an adjustment after working on a larger-than-life project such as the Hadron Collider, but says she has since found her niche.

“I felt a bit like I was starting over as a grad student when I began my postdoc at Mass General, because so much of the material was new to me. However, I feel like I progressed much faster than I would have if I hadn’t gone through a PhD in particle physics first.

“Many of my former fellow grad students have gone into the tech world, or finance, but I’m happy I found an opportunity to continue doing academic research.”

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