Stereotactic body radiation therapy (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. Now, a first-of-its-kind 4D technology enables healthcare professionals to deliver safer, more precise radiotherapy treatment to patients with complex spine tumors.

Brainlab AG’s (Munich, Germany) ExacTrac Dynamic is a patient positioning and monitoring system that helps spine tumor specialists address the challenge of patient movement during SBRT. Recently, spine tumor specialists at the Brain and Spine Tumor Center at NYU Langone’s Perlmutter Cancer Center (New York, NY, USA) become the first institution in New York City to use ExacTrac Dynamic. 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.

The CE Marked 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.

“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.”

“If the patient moves, it tells us exactly how much they have moved - which we confirm by X-ray and thermal imaging,” added Dr. Silverman. “This precise monitoring is reassuring to both treating physicians and our patients.” 

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