T1/T2-weighted ratio imaging via MRI-guided focused ultrasound (MRgFUS) improves the lesion normalized contrast of chronic brain lesions, according to research published on 16 December in Radiology.
A team led by doctoral candidate Begoña Andikoetxea from the Clínica Universidad de Navarra in Pamplona, Spain, reported that T1/T2-weighted ratio imaging substantially improved chronic lesion contrast versus T2-weighted imaging. It also reduced interobserver variability and measurement error.
“These findings support the utility of T1/T2-weighted ratio imaging as a valuable tool for assessing [MRgFUS imaged] chronic lesions, with potential applications in clinical practice and research,” the Andikoetxea team wrote.
MRgFUS thalamotomy can treat tremor disorders in patients with either essential tremor or tremor-dominant Parkinson's disease. T2-weighted imaging is typically used to evaluate thalamic lesions identified by MRgFUS. However, T2-weighted imaging has variable lesion visibility during follow-up in some patients. This is due to lesions showing low contrast or becoming undetectable, the researchers wrote.
Definition of regions for lesion normalized contrast calculation on T2-weighted images. (A) Axial T2-weighted image at the 6-month follow-up shows the lesion (outlined in red) in a patient who underwent left-sided MRI-guided focused ultrasound thalamotomy. (B) The corresponding baseline T2-weighted image with a cylindrical reference region (red circle, 16-mm diameter, matching the lesion section number and centered at the lesion centroid) used to measure normal tissue intensity. The same regions were used for lesion normalized contrast calculation on T1/T2-weighted ratio images.RSNA
T1/T2-weighted ratio imaging stems from the mathematical division of T1-weighted by T2-weighted images with additional preprocessing. This approach aims to improve contrast in myelin-rich brain structures, which can help evaluate tissue integrity and microstructural changes in neurodegenerative diseases.
Andikoetxea and colleagues studied whether T1/T2-weighted ratio imaging improves the lesion-normalized contrast of chronic MRgFUS thalamotomy lesions. They compared the results with those of T2-weighted imaging.
The retrospective study included 54 patients, including 27 with essential tremor and 27 with tremor-dominant Parkinson's disease.
T1/T2-weighted ratio images led to higher lesion normalized contrast, including for patients with tremor recurrence.
Comparison between T1/T2-weighted ratio images, T2-weighted images | |||
Measure | T2-weighted images | T1/T2-weighted ratio images | p-value |
Lesion normalized contrast | 19.2% | 36.3% | < 0.001 |
Normalized contrast for patients with tremor recurrence | 25.3% | 45.2% | 0.03 |
Between-evaluator agreement | 0.81 | 0.94 | < 0.05 |
The researchers noted that the improvement in between-evaluator agreement is a critical finding that suggests lower variability.
“This improvement facilitates the more accurate detection of insufficient lesioning and supports informed clinical and surgical decisions, such as re-treatment in patients with tremor recurrence, especially those with low-visibility T2-weighted lesion,” they wrote.
Further analysis showed a positive correlation between lesion overlap with the ventrolateral posterior ventral thalamic nucleus -- the part of the brain that receives information for pain, temperature, and touch -- and tremor relief for both imaging modalities.
The study authors called for future studies to explore the use of T1/T2-weighted imaging against that of other advanced MRI modalities to further improve chronic lesion assessment.
Read the full study here.
![Examples of ultrasound findings and techniques. (A) Images in a 39-year-old male patient with a mass in the left thigh. The mass is heterogeneous on the B-mode US image (compared with the patient in D) and showed increased microvascularity (superb microvascular imaging [SMI]) and shear-wave elastography (SWE) values. Undifferentiated pleomorphic sarcoma was diagnosed at biopsy (with pleomorphic rhabdomyosarcoma in surgical specimen). (B) Images in an 18-year-old male patient with a mass in the left leg. The mass is hypoechoic on the B-mode image, with no other findings suggestive of malignancy. The lesion is in contact with the cortex of the tibia, which is slightly irregular. CT revealed a doubtful anteromedial tibial erosion. The microvascular study demonstrated high vascularization, suggestive of malignancy. Periosteal Ewing sarcoma was diagnosed with both histologic and immunohistochemical confirmation. (C) Images in a 69-year-old female patient with a lump growing on the outside of the left leg. Multiple SWE examinations were performed (please note the high values obtained in the measurements, whereas the color map highlights the stiffness relative to adjacent tissues). SMI showed areas of increased vascularization to target for sampling. Undifferentiated spindle cell sarcoma was diagnosed at biopsy, with residual leiomyosarcoma in the surgical specimen after neoadjuvant therapy. (D) Images in a 56-year-old female patient with a mass in the right thigh. The mass is heterogeneous at both B-mode ultrasound (similar to patient A) and MRI (coronal T2-weighted spectral attenuated inversion recovery [SPAIR]; T1-weighted pre-contrast and postcontrast imaging), which even shows uptake after the administration of paramagnetic contrast material, which is traditionally suggestive of malignancy. Low values at SMI and elastography are suggestive of benignity. Spindle cell lipoma was diagnosed at biopsy, with atypical spindle cell lipomatous tumor in the surgical specimen.](https://img.auntminnieeurope.com/mindful/smg/workspaces/default/uploads/2026/08/images-radiol250278fig2.APCFLSvX6p.jpg?auto=format%2Ccompress&fit=crop&h=100&q=70&w=100)
![Examples of ultrasound findings and techniques. (A) Images in a 39-year-old male patient with a mass in the left thigh. The mass is heterogeneous on the B-mode US image (compared with the patient in D) and showed increased microvascularity (superb microvascular imaging [SMI]) and shear-wave elastography (SWE) values. Undifferentiated pleomorphic sarcoma was diagnosed at biopsy (with pleomorphic rhabdomyosarcoma in surgical specimen). (B) Images in an 18-year-old male patient with a mass in the left leg. The mass is hypoechoic on the B-mode image, with no other findings suggestive of malignancy. The lesion is in contact with the cortex of the tibia, which is slightly irregular. CT revealed a doubtful anteromedial tibial erosion. The microvascular study demonstrated high vascularization, suggestive of malignancy. Periosteal Ewing sarcoma was diagnosed with both histologic and immunohistochemical confirmation. (C) Images in a 69-year-old female patient with a lump growing on the outside of the left leg. Multiple SWE examinations were performed (please note the high values obtained in the measurements, whereas the color map highlights the stiffness relative to adjacent tissues). SMI showed areas of increased vascularization to target for sampling. Undifferentiated spindle cell sarcoma was diagnosed at biopsy, with residual leiomyosarcoma in the surgical specimen after neoadjuvant therapy. (D) Images in a 56-year-old female patient with a mass in the right thigh. The mass is heterogeneous at both B-mode ultrasound (similar to patient A) and MRI (coronal T2-weighted spectral attenuated inversion recovery [SPAIR]; T1-weighted pre-contrast and postcontrast imaging), which even shows uptake after the administration of paramagnetic contrast material, which is traditionally suggestive of malignancy. Low values at SMI and elastography are suggestive of benignity. Spindle cell lipoma was diagnosed at biopsy, with atypical spindle cell lipomatous tumor in the surgical specimen.](https://img.auntminnieeurope.com/mindful/smg/workspaces/default/uploads/2026/08/images-radiol250278fig2.APCFLSvX6p.jpg?auto=format%2Ccompress&dpr=2&fit=crop&h=167&q=70&w=250)
