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Radiological Physics Center Ensures Strength, Applicability of Clinical Trial Results

Conquest - Summer 2010

By Mary Brolley

If clinical trials are the best hope for advancing cancer treatment and saving or extending lives, then the stronger the clinical trial, the more grounded the hope.

These nearly transparent "heads" are
anthropomorphic phantoms that stand in
for the real thing to help Geoffrey Ibbott, Ph.D.,
and his team check the calibration of radiation
machines used in collaboration with clinical

Day after day, from all over the United States and the world, boxes of precious cargo arrive at the unassuming Radiological Physics Center (RPC) in the Department of
Radiation Physics on the outskirts of the country’s largest medical center.

Inside the boxes are tiny opaque pellets called thermoluminescent dosimeters (TLDs) that measure a dose of radiation. Some of the TLDs are encased in anthropomorphic phantoms, back from an important mission: to gauge not only whether radiation machines used in cooperative clinical trials have been correctly calibrated, but also whether the participating institution can deliver a dose distribution as intended.

The 30 employees of the RPC — who include medical physicists and technologists, dosimetrists, computer systems analysts, graduate students, administrative support staff and visiting experts — know that their work affects patients far beyond their home base at MD Anderson.

Their efforts and expertise have, in fact, helped ensure the strength and applicability of clinical trial results for more than four decades, affecting patients all over the country and the world.

Impressive power demands strict monitoring

Since 1968, the National Cancer Institute has trusted the RPC to make sure the institutions that participate — or wish to participate — in clinical trials have the necessary radiation therapy equipment, personnel and procedures.

The long-running grant acknowledges the impressive power of radiation therapy techniques and the need to measure radiation output with corresponding precision
to ensure patient safety.

Monitoring the machines at so many locations may seem a daunting task, but Geoffrey Ibbott, Ph.D., professor in the Department of Radiation Physics, and his team have several ways of accomplishing it. Their first line of duty involves sending out hundreds of boxes of TLDs a month.

The institutions position the TLDs under their radiation therapy machines, perform a set of prescribed tests, then pack them up and send them back. Once returned to
Ibbott’s team, they’re tested to see if the output falls within accepted parameters.

If problems are found, the RPC has other ways of figuring out what’s wrong, Ibbott says. “We do onsite dosimetry reviews. We visit about 30 institutions a year. And we do record reviews for quality assurance.”

Because the goal is to help an institution resolve the problem, RPC staffers act as detectives to figure out why the machine isn’t calibrated correctly.

Between 1970 and 1980, the compliance rate for beam calibration among these institutions increased from about 70% to 90%. But as techniques have become more and more complex, discrepancies in other components of the treatment are more prevalent.

Mastery honed by research, experience

How do they keep up with the constantly evolving techniques to evaluate them?

“We read journals. We stay abreast of clinical activities, and we collaborate with the 10 or 11 groups that conduct clinical trials. We all stay up to date — we have to,” Ibbott says. “By monitoring in a number of ways and by knowing the processes inside and out, we try to avoid big problems that might occur because of an accumulation of small errors.”

Beyond the benefit to clinical trials, Ibbott knows that RPC employees help safeguard the treatment of all patients who receive radiation therapy as part of their
cancer treatment.

“It’s a lot of responsibility, and we’re very aware of it,” Ibbott says. “We spend a lot of time making sure we find errors and correct them.”

By the Numbers

These data give an idea of the scope of expert support provided by the Radiological Physics Center:

  • Centers monitored worldwide: 1,768
  • Centers monitored in the United States: 1,590
  • Beams measured each year: approximately 13,000
  • Years MD Anderson has held the grant: 42
  • Physicists in MD Anderson’s RPC: 6
  • Centers visited each year on average: 30 (since 2005)
  • Clinical trials in which MD Anderson’s RPC has been involved: 70 (since 2005)
  • Miles to the most distant center: 11,200 to Perth, Australia
  • Anthropomorphic phantoms mailed last year: 425

© 2015 The University of Texas MD Anderson Cancer Center