New Way to Measure Brain Oxygen Levels in Patients

Radiotherapy typically follows a dosing and treatment plan based on clinical research to minimize the impact of the radiation on healthy tissues. However, since the effects of radiotherapy can only be evaluated after the treatment is delivered, it is difficult to predict the immediate effects on a patient or potential side effects that might develop at a later stage. So, even conventional doses administered to patients might potentially cause long-term side effects in some people.

“Cancer therapies produce extensive changes in the physiological and morphological properties of tissues, which are also dependent on the individual,” says Teemu Myllylä, associate professor, University of Oulu, Finland, who, along with Juha Nikkinen, PhD, chief physicist, Oulu University Hospital, Department of Oncology and Radiotherapy, is working to make cancer treatment patient-centric.

In a study published in the Journal of Biomedical Optics (JBO), the researchers report a method to measure and evaluate an individual’s biological response to radiotherapy in real-time. This method uses a functional near-infrared spectroscopy (fNIRS) device that employs infrared light to measure changes in the concentration of hemoglobin in the brain—an indicator of tissue oxygenation level.

This noninvasive technique is commonly used to study brain activity in response to different stimuli and cognitive tasks. However, in this case, the researchers employed it to measure changes in the concentration of hemoglobin in the brain, as the patients underwent whole-brain radiotherapy treatment.

“A fiber optics setup using multiwavelength fNIRS was combined with a medical linear accelerator to measure cerebral tissue oxygenation changes during the brain radiotherapy treatment, where the radiation dose is limited to the brain areas to avoid irradiating the eyes,” says Myllylä.

Since hemoglobin levels are a useful indicator of changes in blood volume, the use of fNIRS can provide insights into the effects of radiotherapy on blood circulation in the tissues. Using this noninvasive technique, researchers successfully measured tissue oxygenation levels in ten patients and observed instantaneous changes through multiple irradiations during their treatment.

“This is the first time human cerebral hemodynamics and cerebral tissue oxygenation changes have been measured during irradiation in clinical radiotherapy,” observes Myllylä. “The instantaneous measurement of tissue oxygenation levels during radiotherapy is especially helpful in cases of tumor hypoxia, which is when the oxygen levels in a tumor are low due to certain conditions. Such tumors are particularly resistant to radiotherapy. Our proposed method can be used to assess the efficacy of cancer treatment. This can eventually enable physicians tailor radiation doses to optimize treatment and improve outcomes for their patients,” he concludes.

The researchers plan to use their technique to study how individual patients respond to different doses of radiation therapy. This can greatly help advance the field of personalized cancer treatment.

- This press release was originally published on the International Society for Optics and Photonics website