The Brain and Spine Tumor Center at NYU Langone’s Perlmutter Cancer Center has become the first institution in New York City to use ExacTrac Dynamic—a patient positioning and monitoring system that helps the spine tumor team address the challenge of patient movement during stereotactic body radiation therapy (SBRT). SBRT can be highly effective in treating certain types of spine metastases, such as those associated with primary melanoma or kidney cancers, which are typically less responsive to traditional external beam radiation therapy. However, even in the hands of the most experienced practitioners, the slightest patient movement during treatment—in the range of a millimeter—can expose the nearby spinal cord to high doses of radiation, in some cases leading to life-altering complications.
“Patients with spine tumors typically have motor and sensory issues, including pain,” explains Joshua S. Silverman, MD, PhD, associate professor in the Department of Radiation Oncology at NYU Grossman School of Medicine and director of spine radiosurgery. “Their discomfort can make them more susceptible to the small movements that present significant risk when they receive high-dose radiation therapy so close to the spinal cord and other organs.”
Real-Time Data Enhance Decision-Making
Before ExacTrac Dynamic, patient movement could only be identified once each dose had been delivered—there was no opportunity to pause treatment if higher-risk movement was observed. Once those movements were identified, it was too late to mitigate the effects of any off-target radiation delivery. If higher levels of radiation reached the spinal cord, this could limit the possibility of future treatment. ExacTrac Dynamic addresses those problems by providing continuous visualization of a patient’s position and potential movements in real time, enabling more accurate targeting of the radiation dose.
“If the patient moves, it tells us exactly how much they have moved—which we confirm by X-ray and thermal imaging,” Dr. Silverman explains. “This precise monitoring is reassuring to both treating physicians and our patients.”
A Trio of Technologies Informs Multidisciplinary Care
The system works through a combination of surface imaging technology, X-ray hardware, and a surface projector and camera. During treatment, light is projected onto the patient, creating a 3D picture of the patient’s anatomy. That image is compared with a CT scan of the patient, with notations marking where their position should be while the radiation beam is delivered. The system’s software analyzes the patient’s movements, displaying calculations that represent how much the patient has moved and the extent to which any movement deviates from a safe range.
“Dr. Silverman develops the treatment plan, which includes precisely how much movement can be tolerated based on radiation dosing and the delivery site,” explains medical physicist Martha J. Malin, PhD, assistant professor in the Department of Radiation Oncology, who is present at each treatment. “When the movement extends beyond that tolerance threshold, the system turns off the radiation so the patient can be repositioned.”
The application of ExacTrac Dynamic highlights the center’s patient-centered, multidisciplinary approach to care. “We all think of things in a slightly different way based on what we do and how we do it,” adds Ilya Laufer, MD, director of the Spine Tumor Program and member of the faculty in the Department of Neurosurgery at NYU Grossman School of Medicine. “When our expertise in medical physics, radiation oncology, and neurosurgery comes together, we can balance a patient’s clinical indications, radiographic assessment, and tumor targeting to deliver the safest, most efficacious treatment possible.”