Limitations of T2 Imaging in Long-Term Follow Up
Despite its importance in follow up, T2-weighted MRI, the standard for visualizing MRgFUS thalamotomy lesions, has limitations in long-term assessment, becoming particularly critical to evaluate when there is a recurrence of symptoms.
Once the edema from the procedure resolves at around six months after treatment, the lesion tends to be difficult to see on the T2-weighted image. This makes it difficult, if not impossible, to correlate symptoms with the lesion location.
To address this loss of visibility, T1/T2-weighted ratio enhances contrast in the image by dividing the T1-weighted scan by the T2-weighted one.
In the study, Dr. Sanchez-Catasus and colleagues compared this method with T2-weighted imaging in 54 patients, including 27 with ET and 27 with TDPD.
Lesion normalized contrast was higher for T1/T2-weighted ratio images than for T2-weighted images. “We found similar results in patients with tremor recurrence,” Dr. Sanchez-Catasus said. “In addition, the T1/T2-weighted ratio imaging had higher between-evaluator agreement than T2-weighted imaging.”
These advantages may be especially valuable in patients with recurrent tremors, where lesion visibility is critical for reassessment.
Looking ahead, Dr. Sanchez-Catasus and colleagues plan to investigate whether the T1/T2-weighted ratio allows visualization of chronic lesions that are not visible in the T2 sequence. It will provide insights into tremor recurrence.
“Some studies show that at one year, approximately half of patients show no discernible signal abnormalities on the T2 sequence, which is the current standard for follow-up after MRgFUS,” Dr. Sanchez-Catasus said. “It is of great interest to reveal the lesion trace that standard T2 scans may miss, to obtain a quantitatively superior view of the ablation site.”
In patients with recurrent tremors, invisible T2 findings create uncertainty about whether recurrence reflects inadequate initial treatment, Dr. Sanchez-Catasus said. If the T1/T2-weighted ratio makes the invisible lesion “reappear,” it could finally confirm whether the targeting was correct.
“It would allow us to determine whether the disappeared lesion was simply too small or biologically soft, lacking the permanent architectural change necessary for long-term relief,” he said.