Magnetic Resonance-guided Focused Ultrasound Research Articles

Using the Tissue Impulse Response Function to Streamline Fractionated MRgFUS-Induced Hyperthermia

Background/Objectives: Combining radiation therapy with mild hyperthermia, especially via magnetic resonance-guided focused ultrasound (MRgFUS), holds promise for enhancing tumor control and alleviating symptoms in cancer patients. However, current clinical applications of MRgFUS focus primarily on ablative treatments, and using MRI guidance for each radiation session increases treatment costs and logistical demands. This study aimed to test a streamlined workflow for repeated hyperthermia treatments that reduces the need for continuous MRI monitoring, using an approach based on impulse response function (Green’s function) to optimize acoustic power settings in advance. Methods: We implemented the Green’s function approach in a perfused, tissue-mimicking phantom, conducting 30 experiments to simulate hyperthermia delivery via MRgFUS. Pre-calculated acoustic power settings were applied to maintain a stable hyperthermia target without the need for real-time feedback control from MRI thermometry. Additionally, a retrospective analysis of patient thermometry data from MRgFUS sonications was performed to assess feasibility in clinical contexts. Results: Our experiments demonstrated consistent, stable hyperthermia (+7 °C) for 15 min across varying perfusion rates, outperforming conventional closed-loop MRI feedback methods in maintaining temperature stability. The retrospective analysis confirmed that this method is noise-robust and clinically applicable. Conclusions: This off-line approach to hyperthermia control could simplify the integration of MRgFUS hyperthermia in cancer treatment, reducing costs and logistical barriers. These findings suggest that our method may enable the broader adoption of hyperthermia in radiation therapy, supporting its role as a viable adjuvant treatment in oncology.

Long-term outcomes and re-intervention rates in women undergoing mri-guided focused ultrasound (mrgfus) for uterine fibroids: a 7-year follow-up study.

To assess the long-term outcomes of MR-guided focused ultrasound (MRgFUS) for treating uterine fibroids, focusing on re-intervention rates, pregnancy outcomes, and the onset of menopause over a 7-year follow-up period. We conducted a historical cohort study of 99 women with symptomatic uterine fibroids who underwent MRgFUS between 2013 and 2020 at a single tertiary medical center. Data collection included patient demographics, treatment details, and follow-up interviews. Re-intervention rates were evaluated using Kaplan-Meier curves and Cox regression analysis to identify predictors of further treatments, with a specific focus on age-related differences. Over a median follow-up of 6.1years, 33.1% of women required re-intervention for persistent fibroid symptoms. The median patient's age was 43years old. Women aged ≤ 43years had significantly higher re-intervention rates than those aged 44 + years (47.5% vs. 16.7%, p = 0.005). Multivariable Cox regression identified age as the sole significant predictor of re-intervention (HR44+vs. <43 0.303 95% CI 0.128-0.714, p = 0.006). Sixteen women conceived after MRgFUS, resulting in 21 pregnancies, with 72.2% live births and a spontaneous miscarriage rate of 22.2%. The mean age of menopause was 51.4years, similar to global averages. MRgFUS is a practical, noninvasive option for treating symptomatic uterine fibroids. Older women show lower re-intervention rates. Pregnancies post-MRgFUS are possible, and the procedure does not appear to affect the onset of menopause. Age remains a crucial predictor for further re-intervention.

Magnetic Resonance-Guided Focused Ultrasound Thalamotomy in a Prospective Cohort of 52 Patients with Parkinson's Disease: A Possible Critical Role of Age and Lesion Volume for Predicting Tremor Relapse.

Magnetic resonance-guided focused ultrasound (MRgFUS) thalamotomy of ventral intermediate (Vim) nucleus is useful to treat drug-resistant tremor-dominant Parkinson's disease (TdPD), but tremor relapse may occur. Predictors of relapse have been poorly investigated so far. The aim of this study is to evaluate the role of clinico-demographic, procedural, and neuroradiological variables in determining clinical response, relapse, and adverse events (AEs) in TdPD after MRgFUS Vim-thalamotomy. Fifty-two TdPD patients who consecutively underwent unilateral MRgFUS Vim-thalamotomy were prospectively evaluated at baseline and after 24 hours, 1 month, 6 months, and 12 months using MDS-UPDRS-III in off and on medication conditions. AEs were collected at each evaluation. Lesion volume was calculated at 24-hour magnetic resonance imaging (MRI). Patients with tremor improvement <30% in off medication were considered nonresponders (when detected after 24 hours) or relapsers (if detected from 1-month visit onward). All patients showed tremor improvement >30% at 24 hours. Tremor relapse occurred in 12 patients (23%), exclusively during the first month after thalamotomy. Relapse was associated with younger age (P = 0.030) and smaller lesion volume (P = 0.030). At 1 month, 22 patients (42%) had AEs; at 6 and 12 months, AEs persisted in 19% and 6% of cases. AEs at 6 months were associated with larger lesions (P = 0.018). All AEs were mild. MRgFUS Vim-thalamotomy is effective in treating tremor in TdPD. Relapse is associated with younger age and smaller lesion volume, but larger lesions make AEs more likely to persist. We suggest that a lesion volume between 145 and 220 mm3 on T1-weighted MRI may be the therapeutic window that ensures tremor control without long-lasting AEs. © 2025 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

MRI-guided focused ultrasound for treating Parkinson’s disease with human mesenchymal stem cells

Parkinson’s disease (PD) is a progressive disorder that affects the nervous system and causes regions of the brain to deteriorate. In this study, we investigated the effects of MR-guided focused ultrasound (MRgFUS) for the delivery of human mesenchymal stem cells (MSCs) on the 6-hydroxydopamine (6-HODA)-induced PD rat model. MRgFUS-induced blood-brain barrier (BBB) permeability modulation was conducted using an acoustic controller with the targets at the striatum (ST) and SN. Human MSCs were injected immediately before sonication. Here, we show that we can deliver human MSCs into Parkinsonian rats through MRgFUS-induced BBB modulation using an acoustic controller. Stem cells were identified in the sonicated brain regions using surface markers, indicating the feasibility of MSC delivery via MRgFUS. MSCs + FUS treatment significantly improved the behavioural outcomes compared with control, FUS alone, and MSCs alone groups (p < 0.05). In the quantification analysis of the TH stain, a significant reservation of dopamine neurons was seen in the MSCs + FUS group as compared with the MSCs group (ST: p = 0.03; SN: p = 0.0005). Mesenchymal stem cell therapy may be a viable treatment option for neurodegenerative diseases such as Parkinson’s. Transcranial MRgFUS serves as an efficacious and safe method for targeted and minimally invasive stem cell homing.

Therapeutic manipulation and bypass of the blood-brain barrier: powerful tools in glioma treatment.

The blood-brain barrier (BBB) remains an obstacle for delivery of chemotherapeutic agents to gliomas. High grade and recurrent gliomas continue to portend a poor prognosis. Multiple methods of bypassing or manipulating the BBB have been explored, including hyperosmolar therapy, convection-enhanced delivery (CED), laser-guided interstitial thermal therapy (LITT), and Magnetic Resonance Guided Focused Ultrasound (MRgFUS) to enhance delivery of chemotherapeutic agents to glial neoplasms. Here, we review these techniques, currently ongoing clinical trials to disrupt or bypass the BBB in gliomas, and the results of completed trials.

MRgFUS disconnection surgery for hypothalamic hamartoma-related epilepsy: case report and literature review.

Drug-resistant epilepsy (DRE) secondary to hypothalamic hamartoma (HH) often requires surgical resection or stereotactic radiosurgery, which frequently fail to provide satisfactory outcomes and are associated with severe side effects. Magnetic resonance-guided focused ultrasound (MRgFUS) may represent a minimally invasive surgical approach to HH by offering precise thermal ablation of sub-millimetric brain targets while sparing surrounding structures. We present the case of a 19-year-old man with HH-associated DRE, who was successfully treated with MRgFUS. The procedure resulted in effective ablation of the hypothalamic interface of the HH, disconnecting the epileptogenic lesion from the surrounding brain tissue. We also reviewed the literature on MRgFUS for DRE. The patient experienced a complete resolution of seizures and significant improvements in social and occupational functioning over an 18-month follow-up period. No neurological, cognitive, or endocrinological adverse effects were observed. Our case report and literature review suggest that MRgFUS may achieve adequate seizure control in DRE associated with HH without adverse effects. While MRgFUS shows promise for other forms of DRE, data remain preliminary, and some safety concerns persist. Further studies with long-term follow-up are warranted to better support the use of MRgFUS in DRE.

Innovative Approaches to Brain Cancer: The Use of Magnetic Resonance-guided Focused Ultrasound in Glioma Therapy.

Gliomas are a wide group of common brain tumors, with the most aggressive type being glioblastoma multiforme (GBM), with a 5-year survival rate of less than 5% and a median survival time of approximately 12-14 months. The standard treatment of GBM includes surgical excision, radiotherapy, and chemotherapy with temozolomide (TMZ). However, tumor recurrence and progression are common. Therefore, more effective treatment for GBM should be found. One of the main obstacles to the treatment of GBM and other gliomas is the blood-brain barrier (BBB), which impedes the penetration of antitumor chemotherapeutic agents into glioblastoma cells. Nowadays, one of the most promising novel methods for glioma treatment is Magnetic Resonance-guided Focused Ultrasound (MRgFUS). Low-intensity FUS causes the BBB to open transiently, which allows better drug delivery to the brain tissue. Under magnetic resonance guidance, ultrasound waves can be precisely directed to the tumor area to prevent side effects in healthy tissues. Through the open BBB, we can deliver targeted chemotherapeutics, anti-tumor agents, immunotherapy, and gene therapy directly to gliomas. Other strategies for MRgFUS include radiosensitization, sonodynamic therapy, histotripsy, and thermal ablation. FUS can also be used to monitor the treatment and progression of gliomas using blood-based liquid biopsy. All these methods are still under preclinical or clinical trials and are described in this review to summarize current knowledge and ongoing trials.

Diffusion-weighted imaging as a non-gadolinium alternative for immediate assessing nonperfused area of adenomyosis after magnetic resonance-guided focused ultrasound (MRgFUS) ablation: a potential technique but with slightly overestimate.

It is a technical challenge to monitor ablation outcome during magnetic resonance-guided focused ultrasound (MRgFUS) treatment using non-gadolinium technique. The study aimed to investigate the value of diffusion-weighted imaging (DWI) for immediately assessing nonperfused area of adenomyosis after MRgFUS treatment. We retrospectively included patients with adenomyosis who underwent MRgFUS ablation and underwent both DWI (b=800 sec/mm2) and contrast-enhanced (CE) magnetic resonance (MR) imaging within 15 minutes after treatment. Two blinded observers independently reviewed the DWI scan of the ablated necrotic lesions and measured their area in the central slice of DWI and CE imaging. Consistency and differences in the assessment result were compared. A total of 48 women with adenomyosis (mean age 39.6±4.9 years) were analyzed. Abnormal signals were observed in all 48 adenomyosis lesions on DWI images and could be categorized into 3 types: large area of central low-signal with complete (type 1) or incomplete (type 2) high-signal ring, or inhomogeneous high-signal areas without a ring sign (type 3). Intra- and interobserver intraclass correlation coefficients (ICCs) were 0.84 and 0.80, respectively, for categorizing the DWI signal types (both P<0.001). The DWI abnormal signals and nonperfused areas were essentially corresponding. ICCs were ranged from 0.85 to 0.91 for area measurements using DWI vs. CE MR imaging (all P<0.001). The area of necrotic lesions measured using DWI images was larger than that using CE images (17.17±7.79 vs. 15.41±7.36 cm2, P<0.001). DWI can serve as a non-gadolinium technique for the initial evaluation of nonperfused area of adenomyosis after MRgFUS ablation. However, it is also important to note that DWI may slightly overestimate the nonperfused area.

Cognitive impacts of unilateral MR-guided focused ultrasound thalamotomy: a meta-analysis and a call for systematic neuropsychological assessment.

Pharmacoresistant tremors, often seen in Parkinson disease and essential tremor, significantly impair patient quality of life. Although deep brain stimulation has been effective, its invasive nature limits its applicability. MR-guided focused ultrasound (MRgFUS) thalamotomy offers a noninvasive alternative, but its cognitive impacts are not fully understood. This meta-analysis aimed to evaluate the cognitive and emotional effects of unilateral MRgFUS thalamotomy in patients with pharmacoresistant tremors. Adhering to PRISMA guidelines, a comprehensive literature search was conducted across PubMed, Web of Science, and the Cochrane Library. Studies were included if they involved unilateral MRgFUS thalamotomy and assessed cognitive functions pre- and postprocedure. The primary outcomes were changes in cognitive functions and emotional states postthalamotomy. Of 90 identified articles, 5 met the inclusion criteria, encompassing 112 patients (74 essential tremor, 38 Parkinson disease). The analysis revealed no significant deterioration in cognitive domains or emotional states postprocedure. Statistical heterogeneity among studies was small for cognitive outcomes but moderate for emotional states. Unilateral MRgFUS thalamotomy appears to be a safe procedure with respect to cognitive and emotional outcomes in patients with pharmacoresistant tremors. However, the small number of studies and the short-term nature of assessments necessitate caution. Further research, especially on long-term cognitive effects and in the context of bilateral procedures, is essential for a comprehensive understanding of MRgFUS thalamotomy's neuropsychological impact. Systematic review registration no.: CRD42023491757 (www.crd.york.ac.uk/prospero).

State of Practice on Transcranial MR-Guided Focused Ultrasound: A Report from the ASNR Standards and Guidelines Committee and ACR Commission on Neuroradiology Workgroup.

Transcranial focused ultrasound (FUS) is a versatile, MR-guided, incisionless intervention with diagnostic and therapeutic applications for neurologic and psychiatric diseases. It is currently FDA-approved as a thermoablative treatment of essential tremor and Parkinson disease. However, other applications of FUS including BBB opening for diagnostic and therapeutic applications, sonodynamic therapy, histotripsy, and low-intensity focused ultrasound neuromodulation are all in clinical trials. While FUS targeting for essential tremor and Parkinson disease has classically relied on an indirect, landmark-based approach, development of novel, advanced MR imaging techniques such as DTI tractography and fast gray matter acquisition T1 inversion recovery has the potential to improve individualized targeting and thus potentially enhance treatment response, decrease treatment times, and avoid adverse effects. As the technology advances and the number of clinical applications increases, the role of the neuroradiologist on a multidisciplinary team will be essential in pairing advanced structural and functional imaging to further this image-guided procedure via a precision medicine approach. This multi-institutional report, written by an experienced team of neuroradiologists, neurosurgeons, and neurologists, summarizes current practices, the use of advanced imaging techniques for transcranial MR-guided high-intensity FUS, recommendations for clinical implementation, and emerging clinical indications.

Magnetic resonance-guided focused ultrasound in dystonia: a scoping review.

Magnetic resonance guided focused ultrasound (MRgFUS) is a non-invasive therapeutic technique that utilizes focused ultrasound waves to generate heat at specific tissue targets within the brain. This emerging technology holds promise for its precision and potential benefits in comparison to traditional surgical interventions. This investigation involves a scoping review, summarizing insights from various studies that explore the advantages, limitations, and outcomes associated with MRgFUS in the treatment of dystonia. This scoping review was conducted using the Preferred Reporting Items for Systematic reviews and Meta-analysis Extension for Scoping Reviews (PRISMA-ScR) guidelines. Data available on MRgFUS use in the management of different types of dystonia were extracted. There is limited data available (n = 11). In the surveyed literature, MRgFUS has consistently shown clinical benefit in patients with dystonia. It is an emerging avenue of treatment and has its challenges. This scoping review highlighted the early but encouraging applications of MRgFUS in dystonia management. While data was limited, existing studies consistently demonstrated positive clinical outcomes. The non-invasive and precise nature of MRgFUS positions it as a promising avenue for further research, despite the challenges associated with its emergent status. This review sets the stage for future inquiries, emphasizing its potential as a valuable tool in dystonia treatment.

Intraprocedural Three-Dimensional Imaging Registration Optimizes Magnetic Resonance Imaging-Guided Focused Ultrasound and Facilitates Novel Applications.

Transcranial magnetic resonance-guided focused ultrasound (MRgFUS) has revolutionized ablative treatment of essential tremor in recent years. However, limitations in precision targeting may account for suboptimal efficacy and significant side effects. We describe a simple intraprocedural three-dimensional image-guided lesion shaping technique that can improve overall outcomes of MRgFUS for essential tremor and facilitate expansion to novel indications. A retrospective review of 84 consecutive MRgFUS procedures performed at Pennsylvania Hospital was performed. Comparison of patient demographics, treatment parameters, and clinical outcomes before and after implementation of this protocol was conducted. Further application of this technique in pallidotomy treatments and ablative disconnection of hypothalamic hamartoma are described. After implementation, the median of total number of sonications (7 vs 9, P = .001), number of therapeutic sonications (3 vs 4, P < .0001), and interval time between the first and last sonication (46:10 vs 68:53 minutes, P = .0004) were significantly reduced. Patients expressed greater satisfaction of treatment (94.1% vs 82.4%, P = .018), greater global impression of change (CGI) (7 vs 6, P = .033), and reduced median number of side effects at 6 months (0 vs 1, P = .026). We also successfully implemented this protocol for novel indications. Intraprocedural lesion shaping for MRgFUS is a simple and versatile imaging protocol augmentation that improves ablation precision and can improve treatment efficacy and broader neurological application.

CTNI-76. A PHASE 1/2 DOSE ESCALATION AND EXPANSION STUDY OF SONODYNAMIC THERAPY WITH SONALA-001 IN COMBINATION WITH NON-ABLATIVE MR-GUIDED FOCUSED ULTRASOUND IN SUBJECTS WITH PROGRESSIVE OR RECURRENT GLIOBLASTOMA

Abstract Recurrent glioblastoma (rGBM) is a lethal brain tumor with no effective standard of care option and an extremely poor prognosis (median survival 6 to 8 months after first recurrence). Sonodynamic therapy (SDT) is a non-invasive combination therapy that utilizes a drug, aminolevulinic acid HCL (SONALA-001, ALA), and a device, the Exablate 4000 Type 2.0 to deliver MR-guided focused ultrasound (MRgFUS). Preclinical studies have shown that SDT activates protoporphyrin IX (PpIX) to generate reactive oxygen species that lead to tumor cell death and improved survival in animal glioma models. A first-in-human Phase 0 trial (NCT04559685) indicated that ALA SDT was well-tolerated and not associated with off-target cellular or radiographic effects and provided direct evidence of reactive oxygen species formation and targeted tumor cell death in recurrent high-grade glioma (rHGG). SDT-202 is a Phase 1/2 multicenter, open-label, dose escalation and expansion study (NCT05370508) of iv SONALA-001 (ALA) in combination with MRgFUS for SDT in patients with progressive or recurrent GBM. Dose escalation will include an initial drug and energy dose escalation of ALA SDT utilizing an accelerated titration design with single subject cohorts for dose level cohorts 1 and 2, followed by cohort 3 with 3 + 3 design for additional dose escalation. SONALA-001 is administered 6 to 9 hours prior to MRgFUS treatment. Once the RP2D is determined, Phase 2 dose expansion will enroll approximately 36 additional subjects to assess safety and efficacy of repeated cycles of ALA SDT at the optimized RP2D. Endpoints of this study are safety evaluation, maximum tolerated dose (MTD), recommended Phase 2 dose (RP2D), and determination of pharmacokinetic (PK) parameters. The Phase 2 portion will further characterize safety of RP2D along with evaluation of efficacy with PFS6 (mRANO), ORR, CBR, DOR, DOCR, TTR, and OS. Preliminary PK and safety results will be presented.

CTNI-74. SONODYNAMIC THERAPY (SDT) USING INTRAVENOUS 5-AMINOLEVULINIC ACID WITH NON-ABLATIVE FOCUSED ULTRASOUND FOR THE TREATMENT OF DIFFUSE INTRINSIC PONTINE GLIOMAS IN PEDIATRICS: INITIAL SAFETY AND OUTCOMES THE MULTICENTER SDT-201 TRIAL

Abstract Diffuse intrinsic pontine glioma (DIPG) is the leading cause of mortality amongst pediatric neuro-oncologic diseases. Sonodynamic therapy with non-ablative MR-guided focused ultrasound (MRgFUS) is being investigated in multiple clinical trials. We describe safety outcomes and initial efficacy of SDT with 5-ALA for the treatment of pediatric patients with DIPG. Twelve patients with DIPG were treated from August 2022-April 2024 as part of a dose-escalation protocol with SDT in a multicenter Phase 1/2 clinical trial (NCT05123534). MRgFUS was combined with the prodrug SONALA-001 (5-ALA iv) to activate its metabolite, protoporphyrin IX, and thereby induce apoptosis within tumor cells. Treatment is delivered every 4 weeks for up to 12 treatments. Patient ages ranged from 3-23 years and 60% were male. Twelve patients underwent a total of 45 SDT treatments (range 2-9). When enrolled, median tumor volume was 1,337 cm3 (range, 310-2078 cm3) and duration since diagnosis was 5 months. SONALA-001 doses tested were 5 mg/kg and 10 mg/kg. Delivered ultrasonic acoustic energy ranged from 190-444 joules/cm3. After 6 months of median follow-up (range 2-18), 2 partial responses occurred, and 9 of 12 patients had stable or improved baseline symptoms (Lansky Status), including improved mobility and diplopia. One adverse clinical event included a small non-operative epidural hematoma secondary to a stereotactic frame pin. There have been no grade 3 or worse treatment-related adverse events or dose-limiting toxicities. Ten patients are alive a median of 11 months after diagnosis; 2 have deceased; 4 have discontinued treatment. Maximum percent tumor volume changes throughout treatment ranged from a -68% reduction to over 100% enlargement. Preliminary analysis of twelve pediatric patients treated with SDT for DIPG demonstrates acceptable safety outcomes and promising clinical results. Additional patient enrollment and longer follow-up times are required to determine efficacy.

Long-term clinical outcome of a novel bilateral capsulotomy with focused ultrasound in refractory obsessive-compulsive disorder treatment.

Magnetic resonance-guided focused ultrasound (MRgFUS) capsulotomy is a promising treatment for refractory obsessive-compulsive disorder (OCD); however, long-term clinical outcome studies are lacking. We aimed to investigate the long-term efficacy and safety of MRgFUS capsulotomy in patients with refractory OCD. Ten of the eleven patients who underwent MRgFUS capsulotomy for treatment-resistant OCD between 2013 and 2014 were included in this study. Clinical outcomes were assessed after 10 years of follow-up post-MRgFUS capsulotomy using tools such as neuropsychological test, the Frontal Systems Behavior Scale (FrSBe), and a locally developed MRgFUS-patient-centered outcomes questionnaire. After 10 years of follow-up, there was a mean improvement of 52.3% in the Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) score. Seven out of the ten participants responded fully (Y-BOCS reduction ≥35% + CGI-I 1 or 2) to the procedure, two of whom achieved remission (Y-BOCS score ≤12 and CGI-S 1 or 2). Obsessive-compulsive symptoms and overall functioning significantly reduced and improved, respectively (Y-BOCS = 20.7 after 2 years vs. 16.4 after 10 years, p = 0.012; Global Assessment of Functioning = 57.4 after 2 years vs. 69.0 after 10 years, p = 0.011). The patients experienced significantly improved frontal lobe-related functions (FrSBe Sum before 91.0 ± 17.6 vs. after 78.6 ± 17.7, p < 0.05). No adverse effects, including cases of suicide and neurological deficits, were reported. The majority of the respondents were generally satisfied with MRgFUS capsulotomy. MRgFUS capsulotomy is an effective and safe treatment option for the treatment of severe refractory OCD with sustained efficacy even after 10 years.

Technical Feasibility of Delineating the Thalamic Gustatory Tract Using Tractography.

Magnetic resonance-guided focused ultrasound (MRgFUS) has been increasingly performed in recent years as a minimally invasive treatment of essential tremor and tremor-dominant Parkinson disease. One of the side effects after treatment is dysgeusia. Some centers use tractography to facilitate the treatment planning. However, there have been no reports of identifying gustatory tracts so far. Our aim was to investigate the technical feasibility of isolating and visualizing the gustatory tracts, as well as to explore the relationship between the gustatory tract and the MRgFUS lesion using actual patient data. We used 20 randomly selected individuals from the Human Connectome Project database to perform tractography of the gustatory tracts. We defined region of interest as the dorsal region of the brainstem, Brodmann area 43 associated with taste perception, and a sphere with a 3-mm radius centered around the ventral intermediate nucleus in the anterior commissure-posterior commissure plane. We also examined the position of the gustatory tract in relation with other tracts, including the medial lemniscus, the pyramidal tract, and the dentatorubrothalamic tract. In addition, using the data of real patients with essential tremor, we investigated the distance between MRgFUS lesions and the gustatory tract and its association with the development of dysgeusia. We delineated a mean of 15 streamlines of the gustatory tracts per subject in each hemisphere. There was no statistical difference in the localization of the gustatory tracts between the left and right cerebral hemispheres. The gustatory tract was located anteromedial to the medial lemniscus and posteromedial to the dentatorubrothalamic tract in the anterior commissure-posterior commissure plane. The distance from the MRgFUS lesion to the gustatory tract was significantly shorter in the case where dysgeusia occurred compared with nondysgeusia cases (P-value: .0068). The thalamic gustatory tracts can be reliably visualized using tractography.

Treatment efficacy prediction of focused ultrasound therapies using multi-parametric magnetic resonance imaging.

Magnetic resonance guided focused ultrasound (MRgFUS) is one of the most attractive emerging minimally invasive procedures for breast cancer, which induces localized hyperthermia, resulting in tumor cell death. Accurately assessing the post-ablation viability of all treated tumor tissue and surrounding margins immediately after MRgFUS thermal therapy residual tumor tissue is essential for evaluating treatment efficacy. While both thermal and vascular MRI-derived biomarkers are currently used to assess treatment efficacy, currently, no adequately accurate methods exist for the in vivo determination of tissue viability during treatment. The non-perfused volume (NPV) acquired three or more days following MRgFUS thermal ablation treatment is most correlated with the gold standard of histology. However, its delayed timing impedes real-time guidance for the treating clinician during the procedure. We present a robust deep-learning framework that leverages multiparametric MR imaging acquired during treatment to predict treatment efficacy. The network uses qualtitative T1, T2 weighted images and MR temperature image derived metrics to predict the three day post-ablation NPV. To validate the proposed approach, an ablation study was conducted on a dataset (N=6) of VX2 tumor model rabbits that had undergone MRgFUS ablation. Using a deep learning framework, we evaluated which of the acquired MRI inputs were most predictive of treatment efficacy as compared to the expert radiologist annotated 3 day post-treatment images.

Quantitative Tractography-Based Evaluations in Essential Tremor Patients after MRgFUS Thalamotomy.

Magnetic resonance-guided focused ultrasound (MRgFUS) targeting the thalamic ventral intermediate nucleus (VIM) is an innovative treatment for drug-refractory essential tremor (ET). The relationship between lesion characteristics, dentate-rubro-thalamic-tract (DRTT) involvement and clinical benefit remains unclear. To investigate whether clinical outcome is related to lesion volume and/or its overlap with the DRTT. To compare the reliability of probabilistic versus deterministic tractography in reconstructing the DRTT and improving VIM targeting. Forty ET patients who underwent MRgFUS thalamotomy between 2019 and 2022 were retrospectively analyzed. Clinical outcomes and adverse effects were recorded at 1/6/12 months after the procedure. The DRTT was generated using deterministic and probabilistic tractography on preoperative diffusion-tensor 3 T-images and location and volume of the lesion were calculated. Probabilistic tractography identified both decussating (d-DRTT) and non-decussating (nd-DRTT) components of the DRTT, whereas the deterministic approach only identified one component overlapping with the nd-DRTT. Despite the lesions predominantly intersecting the medial portion of the d-DRTT, with a significantly greater overlap in responder patients, we observed only a non-significant correlation between tremor improvement and increased d-DRTT-lesion overlap (r = 0.22, P = 0.20). The lesion volume demonstrated a significant positive correlation with clinical improvement at 1-day MRI (r = 0.42, P < 0.01). Variability in the reconstructed DRTT position relative to the lesion center of mass, even among good responders, suggests that this fiber bundle is unlikely to be considered the sole target for a successful MRgFUS thalamotomy in ET. Indirect individualized targeting allows for more precise and reproducible identification of actual treatment coordinates than the direct method.

Magnetic resonance–guided focused ultrasound thalamotomy for tremor

Magnetic resonance–guided focused ultrasound (MRgFUS) thalamotomy has emerged as an effective treatment for tremor, particularly in those patients who are excluded from deep brain stimulation. The authors illustrate an example of MRgFUS thalamotomy, targeting the ventralis intermedius nucleus, in a 78-year-old patient with tremor who had features of essential tremor and tremor-predominant Parkinson’s disease. Significant tremor improvement was seen during the procedure. The authors review step-by-step the preoperative considerations, Vim targeting, treatment, and outcomes for this evolving treatment modality. The video can be found here: https://stream.cadmore.media/r10.3171/2024.7.FOCVID249

Four-tract tractography: multiparametric direct targeting of the dentatorubrothalamic tract

This video article presents a case study of a 70-year-old male with medically refractory essential tremor treated with magnetic resonance–guided focused ultrasound (MRgFUS). Following an initial successful ablation of the right thalamus, the patient underwent left-sided thalamotomy. After two tractography-guided sonications, the authors observed a significant reduction in his right-hand tremor with no immediate side effects. Postprocedure evaluation revealed sustained tremor reduction with minimal side effects, showcasing bilateral MRgFUS as an effective, noninvasive option for essential tremor management. The video can be found here: https://stream.cadmore.media/r10.3171/2024.7.FOCVID2483