A work by the Neurology Department of Clínica Universidad de Navarra has verified that an innovative way of processing magnetic resonance images makes it possible to optimize the follow-up of patients undergoing high-intensity focused ultrasound (HIFU) for essential tremor or Parkinson's disease.
The study, published in the journal "Radiology", concludes that this strategy significantly increases the ability to see the small brain lesion generated in a controlled manner during the procedure, even months after the intervention.
The research focuses on the so-called T1/T2 ratio, an analysis method that mathematically combines two magnetic resonance sequences already available in clinical practice. The image obtained defines the treated region more precisely and provides the specialist with additional information to assess clinical progress and decide on the follow-up plan.
The researcher from the Neurology Department of the Clinic and person responsible for the work, Dr. Carlos Sánchez-Catasus, emphasizes that these data take on special importance in long-term check-ups. "When a patient treated with HIFU returned to present tremor, the doctor needed to know whether the lesion generated during the treatment had been small, whether it was correctly located or whether a biological recovery process had taken place. With this new image we can better assess what has happened and have more information to decide the next steps", he states.
HIFU is based on high-intensity ultrasound that is concentrated with great precision at a specific point in the brain to produce a small therapeutic lesion without opening the skull. In this technique, indicated for certain patients with essential tremor or Parkinson's disease, the patient remains awake inside the magnetic resonance equipment, which makes it possible to monitor the procedure in real time and verify its effects continuously. Clínica Universidad de Navarra incorporated this technology in 2019.
After the intervention, follow-up with magnetic resonance imaging makes it possible to observe how the therapeutic lesion evolves. However, over the months, the T2 sequence used routinely loses its ability to clearly and in detail delimit that area.
The T1/T2 ratio generates, instead, a sharper image of the chronic lesion. To evaluate its performance, the team retrospectively analyzed the MRIs of 54 patients who underwent thalamotomy with HIFU between January 2019 and November 2023. All of them had high-resolution brain magnetic resonance images prior to treatment and at six months.
The data showed that the contrast of the lesions was practically double with the T1/T2 ratio compared with conventional T2 images (36.3% versus 19.2%). This improvement in visualization makes it easier to accurately trace the treated region and provides relevant information to guide clinical decisions during follow-up.
"The T1/T2 is calculated from images that are already obtained routinely, which facilitates its implementation without the need to develop new imaging systems or resort to expensive experimental technologies," says Sánchez-Catasus.