• 2/7/2007
  • Wilmington, DE
  • Kelly Bothum
  • DelawareOnline (www.delawareonline.com)

To the untrained eye, the image on Denise Mahoney’s computer screen might look like a geometry problem gone awry.

It’s a CT scan of a patient with cancer in his head and neck. More than a dozen lines of different colors crisscross the screen. The intersection of these lines cuts the skull into geometric shapes of varying sizes and angles.

But to Mahoney’s skilled eyes, the picture makes plenty of sense. Each line represents a radiation beam. When administered to the patient over a series of treatments, these beams will attack the tumors in the patient’s head and neck while sparing sensitive areas like the eyes and mouth glands.

For a dosimetrist like Mahoney, whose job is to figure out the best way to administer radiation treatments to a cancer patient, there’s a delicate dance between killing cancer cells and protecting nearby organs and tissues. Because of the expertise of a dosimetrist, patients can fight their cancer while preserving as much quality of life as possible.

In the multidisciplinary world of cancer care, dosimetrists play crucial roles on oncology teams. Their job is like that of a radiation pharmacist. Relying on a prescription from a radiation oncologist, dosimetrists develop an individual plan of radiation treatment for a cancer patient. They use special software as well as MRI, CT and PET scans to map out specially measured radiation doses.

Unlike oncologists, who care for patients, or radiation therapists, who administer treatment over many days, dosimetrists never meet the people whose lives they’re working to save. But that doesn’t keep them from being committed to helping them.

“With dosimetry, I still am involved in their care, but now I see I’m helping them without having that relationship,” said Mahoney, 53, a dosimetrist with Christiana Care Health System.

Mahoney first worked as an X-ray technician and later as a radiation therapist for 16 years before moving to dosimetry. Although she liked working with cancer patients, she fretted about becoming too attached to them during their treatments

In 1989 when Mahoney began her career as a dosimetrist, she was the only one employed in the health system. The computer she used to draw up radiation plans used reel-to-reel tapes and took up the length of a wall.

Nearly two decades later, Christiana Care employs a team of seven dosimetrists who use highly technical programs that provide precise points of radiation treatment. They view 3-D — or in some cases 4-D — images of the patient’s body when drawing up intricate radiation treatment plans. Mahoney said the differences in her job from when she started to today almost make it seem like a different career entirely.

“The technology is changing almost every day,” said Mahoney, who works out of Christiana Care’s radiation facility on Silverside Road in Brandywine Hundred. “But it’s not only the technology, it’s the cure rate, too. We can help more people than we could before.”

Christiana Care treats a total of about 40 patients a day at its four radiation sites, plus about 100 patients at the Helen F. Graham Cancer Center, said William Holden, administrative director of radiation oncology for the center. Most patients come for many treatments, usually lasting six to eight weeks, depending on the type of cancer and radiation prescribed. Dosimetrists have developed radiation plans for cancers affecting all parts of the body, including the brain, lungs, breasts and even fingers.

Newer technologies, including targeted radiation which directs larger doses of radiation to a tumor, also are changing how dosimetrists do their job, Holden said. These changes benefit patients by providing them with more precise treatment and fewer side effects, he added.

Mahoney doesn’t mind the behind-the-scenes nature of her job. Knowing that patients benefit from the treatment plans she helps develop is enough reward.