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T1/T2-weighted Ratio to Improve MRI-guided Focused Ultrasound-induced Chronic Lesion Contrast in Patients with Tremor
Begoña Garate Andikoetxea1,2, Goizane Serna Requejo1, Lain H Gonzalez-Quarante3
1Department of Neurology, Clínica Universidad de Navarra, Universidad de Navarra, Av. de Pío XII, 36, 31008 Pamplona, Navarra, Spain.
Abstract:
Background T2-weighted MRI is the standard for visualizing MRI-guided focused ultrasound (MRgFUS) thalamotomy lesions in essential tremor (ET) and tremor-dominant Parkinson disease (TDPD); however, chronic lesion visibility is often variable, including low-contrast or undetectable lesions, complicating long-term assessment, especially in patients with tremor recurrence. Purpose To determine whether T1/T2-weighted ratio imaging improves the lesion normalized contrast (NC) of chronic MRgFUS thalamotomy-induced lesions compared with T2-weighted imaging. Materials and Methods This retrospective study included patients with ET or TDPD who underwent MRgFUS thalamotomy (January 2019 to November 2023). Lesion NC was quantified on T1/T2-weighted ratio and T2-weighted images at the 6-month follow-up. Between-modality NC comparisons used paired t tests. Similar analyses in patients with tremor recurrence used the Wilcoxon signed rank test. Between-evaluator agreement for lesion segmentation was assessed by comparing the average intraclass correlation coefficients (ICCs) via bootstrapping (95% CI for the difference). Spearman-skipped correlation analysis was performed to assess whether lesion overlap with the ventrolateral posterior ventral thalamic nucleus (VLpv) correlated with tremor relief from baseline to the 6-month follow-up. Results A total of 54 patients were included, 27 with ET and 27 with TDPD (mean age, 71.3 years ± 9.2 [SD]; 32 male patients). Lesion NC was higher for T1/T2-weighted ratio images (mean, 36.3% ± 18.2) than for T2-weighted images (mean, 19.2% ± 8.9) (P < .001). Similar results were found in patients with tremor recurrence (median NC at T1/T2-weighted ratio imaging, 45.2% [IQR, 14%-64%]; median NC at T2-weighted imaging, 25.3% [IQR, 9%-31%]). T1/T2-weighted ratio imaging had higher between-evaluator agreement (ICC = 0.94) than T2-weighted imaging (ICC = 0.81; 95% CI for the difference: 0.01, 0.32). Lesion VLpv overlap was positively correlated with tremor relief in patients with ET (T2-weighted imaging: ρ = 0.47 [95% CI: 0.10, 0.74]; T1/T2-weighted ratio: ρ = 0.53 [95% CI: 0.13, 0.76]) and TDPD (T2-weighted imaging: ρ = 0.42 [95% CI: 0.08, 0.67]; T1/T2-weighted imaging ratio: ρ = 0.48 [95% CI: 0.17, 0.66]). Conclusion T1/T2-weighted ratio imaging substantially improved chronic lesion NC compared with T2-weighted imaging, reducing interobserver variability and measurement error. © RSNA, 2025 Supplemental material is available for this article.
Insights
T1/T2-weighted ratio imaging significantly enhances MRI lesion contrast for MRI-guided focused ultrasound thalamotomy in essential tremor and Parkinson disease patients. This improved visualization aids long-term assessment and reduces measurement errors.
Area of Science:
- Neurology
- Radiology
- Medical Imaging
Background:
- T2-weighted MRI is standard for visualizing MRI-guided focused ultrasound (MRgFUS) thalamotomy lesions.
- Chronic lesion visibility can be variable, complicating long-term assessment, especially with tremor recurrence.
Purpose of the Study:
- To evaluate if T1/T2-weighted ratio imaging improves normalized contrast (NC) of chronic MRgFUS thalamotomy lesions compared to T2-weighted imaging.
Main Methods:
- Retrospective study of 54 patients (ET/TDPD) undergoing MRgFUS thalamotomy.
- Lesion NC quantified at 6-month follow-up using T1/T2 ratio and T2-weighted images.
- Inter-evaluator agreement and correlation with tremor relief assessed.
Main Results:
- T1/T2-weighted ratio imaging showed significantly higher lesion NC (36.3%) than T2-weighted imaging (19.2%) (P < .001).
- Improved NC and higher inter-evaluator agreement (ICC=0.94 vs 0.81) observed with T1/T2 ratio imaging.
- Lesion overlap with VLpv correlated with tremor relief for both imaging techniques.
Conclusions:
- T1/T2-weighted ratio imaging substantially improves chronic lesion NC after MRgFUS thalamotomy.
- This technique reduces interobserver variability and measurement error in lesion assessment.
- Enhanced lesion visualization aids long-term follow-up and outcome evaluation in ET and TDPD patients.
