MR Imaging-Guided Focused Ultrasound for Breast Tumors.

Breast tumors remain a complex and prevalent health burden impacting millions of individuals worldwide. Challenges in treatment arise from the invasive nature of traditional surgery and, in malignancies, the complexity of treating metastatic disease. The development of noninvasive treatment alternatives is critical for improving patient outcomes and quality of life. This review aims to explore the advancements and applications of focused ultrasound (FUS) technology over the past 2 decades. FUS offers a promising noninvasive, nonionizing intervention strategy in breast tumors including primary breast cancer, fibroadenomas, and metastatic breast cancer.

Magnetic Resonance-Guided Focused Ultrasound Surgery for Gynecologic Indications.

Magnetic resonance-guided focused ultrasound surgery (MRgFUS) appears to be an effective and safe treatment for uterine fibroids and adenomyosis, particularly in women who wish to preserve fertility. In abdominal wall endometriosis and painful recurrent gynecologic malignancies, MRgFUS can relieve pain, but more research is needed. There is no widespread reimbursement due to the lack of large prospective or randomized controlled trials comparing MRgFUS with standard therapy.

MR-guided Focused Ultrasound Focal Therapy for Prostate Cancer.

Prostate cancer (PCa) is a prevalent malignancy in men, and the management of localized disease has evolved significantly in recent years. Focal therapy, wherein the biopsy confirmed site of tumor with margins is treated leaving the remaining gland intact, has emerged as a promising strategy for treating localized clinically significant PCa, minimizing side effects associated with radical therapies. We present the technical aspects, a summary of the most relevant evidence to date on the performance and safety of this technique, and the characteristic MR imaging findings during treatment, in the early posttreatment period and in the long term.

MR-guided Focused Ultrasound Thalamotomy for Chronic Pain.

MR-guided focused ultrasound (FUS) represents a promising alternative for patients with chronic neuropathic who have failed medical management and other treatment options. Early single-center experience with chronic neuropathic pain and trigeminal neuralgia has demonstrated favorable long-term outcomes. Excellent safety profile with low risk of motor and sensory complications and so far anecdotal permanent neurologic deficits make FUS a powerful tool to treat patients who are otherwise hopeless. Neuromodulation may be the most influential factor driving outcomes and studies devised to detect neuroplasticity will be critical to guide such therapies.

The Use of Focused Ultrasound Ablation for Movement Disorders.

Focused ultrasound ablation achieves selective thermal lesioning of the thalamic and basal ganglia targets using real-time MR imaging guidance. It is US Food and Drug Administration-approved to treat essential tremor and Parkinson's disease tremor, fluctuations, and dyskinesias. Patients often seek focused ultrasound treatment because symptom relief is immediate, and hardware implantation is not required. This review summarizes the current and potential future application of focused ultrasound ablation to treat movement disorders. We also discuss the ongoing research optimizing the technique of focused ultrasound ablation to improve long-term efficacy and minimize the risk of side effects.

MR Imaging-Guided Focused Ultrasound-Clinical Applications in Managing Malignant Gliomas.

Malignant gliomas (MGs) are the most common primary brain tumors in adults. Despite recent advances in understanding the biology and potential therapeutic vulnerabilities of MGs, treatment options remain limited as the delivery of drugs is often impeded by the blood-brain barrier (BBB), and safe, complete surgical resection may not always be possible, especially for deep-seated tumors. In this review, the authors highlight emerging applications for MR imaging-guided focused ultrasound (MRgFUS) as a noninvasive treatment modality for MGs. Specifically, the authors discuss MRgFUS's potential role in direct tumor cell killing, opening the BBB, and modulating antitumor immunity.

MR-guided Focused Ultrasound for Musculoskeletal Applications.

MR-guided focused ultrasound (MRgFUS) has a wide range of musculoskeletal applications. Some indications are well validated, specifically the treatment of painful osseous metastases and osteoid osteoma. Others are only beginning to be studied, such as the treatment of painful facet, sacroiliac, and knee joints. MRgFUS of soft tissue lesions also shows promise, particularly in patients whom alternative modalities are not feasible or may result in significant morbidity. Ongoing and future research will illuminate the full potential for MRgFUS in the treatment of musculoskeletal conditions.

Future Directions of MR-guided Focused Ultrasound.

MR-guided focused ultrasound (MRgFUS) allows for the incisionless treatment of intracranial lesions in an outpatient setting. While this is currently approved for the surgical treatment of essential tremor and Parkinson's disease, advancements in imaging and ultrasound technology are allowing for the expansion of treatment indications to other intracranial diseases. In addition, these advancements are also making MRgFUS treatments easier, safer, and more efficacious.

Magnetic Resonance-Guided Laser Interstitial Thermal Therapy in the Management of Hypothalamic Hamartomas: A Systematic Review and Meta-Analysis.

OBJECTIVE: Magnetic resonance-guided laser interstitial thermal therapy (MRg-LITT) is a promising new technique to ablate epileptic foci in patients with hypothalamic hamartoma (HH). We aim to systematically synthesize all available evidence and determine the effectiveness of MRg-LITT in reducing seizures in patients with HH. METHODS: We systematically searched MEDLINE (PubMed), Embase (Ovid), Scopus, and Google Scholar for all relevant articles. We used Open[Meta]Analyst to pool the number of seizure-free patients after MRg-LITT treatment in a random-effects model. Risk ratios were calculated, and subgroups were analyzed. Comprehensive meta-analysis was used to assess publication bias via funnel plots, Egger's regression test, and Begg's correlation test. This review complies with the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines. RESULTS: After screening the titles, abstracts, and full texts, we included 17 articles in our meta-analysis, which revealed a 77.1% rate of seizure freedom (95% confidence interval 0.696-0.837, P<0.001), with moderate heterogeneity (I2=49.46%). Subgroup analysis by study design and sensitivity analyses excluding 1 study at a time did not impact the results substantially, and we found no evidence of publication bias. Adverse effects included electrolyte imbalances, weight gain, and transient neurologic disturbances. CONCLUSIONS: MRg-LITT might be a feasible and effective technique for ablation of epileptic foci, leading to seizure freedom in a large proportion of patients with HH. However, there is a paucity of literature on the topic, and prospective clinical trials with larger number of participants comparing MRg-LITT to open surgery are needed.

MRI-guided transrectal prostate laser ablation for benign prostatic hypertrophy: a retrospective cohort study.

PURPOSE: To investigate whether MRI-guided transrectal laser ablation is safe and effective for the treatment of lower urinary tract symptoms caused by BPH. MATERIALS AND METHODS: This single-center retrospective cohort study evaluated men who underwent MRI-guided transrectal laser ablation for BPH between February 2017 and July 2021. Age, prostate-specific antigen, prostate volume, prior surgical BPH treatments if any, International Prostate Symptom Score (IPSS) and Sexual Health Inventory of Men (SHIM) were collected. The primary outcome measures assessed were change in IPSS and SHIM 6, 12 and 24 months after laser ablation and adverse events. RESULTS: Fifty-two patients were included, having completed at least one follow-up survey. The mean patient age was 62.9 ± 5.7 years, and mean prostate volume was 80.2 ± 39.2 cc. Eighteen patients (34.6%) had received a prior BPH treatment. The IPSS scores dropped an average of 16.7 ± 7.0 (p < 0.001), 16.9 ± 7.5 (p < 0.001) and 17.1 ± 7.2 (p < 0.001) points from baseline at 6, 12 and 24 months, respectively. There was no statistically significant difference in IPSS score drop between patients who had received a prior BPH procedure and those who had not (p = 0.628). The SHIM scores showed a statistically insignificant increase at all time points. Nineteen patients (36.5%) reported a complication. There were 12 grade II complications (23%) and seven grade I complications (13.5%). There were no grade III or higher complications. CONCLUSION: Transrectal MRI-guided focal laser ablation is safe and effective for the treatment of lower urinary tract symptoms caused by BPH, with a significant improvement in symptom severity after 2 years.

Intraprocedural Diffusion-weighted Imaging for Predicting Ablation Zone during MRI-guided Focused Ultrasound of Prostate Cancer.

Purpose To compare diffusion-weighted imaging (DWI) with thermal dosimetry as a noncontrast method to predict ablation margins in individuals with prostate cancer treated with MRI-guided focused ultrasound (MRgFUS) ablation. Materials and Methods This secondary analysis of a prospective trial (ClinicalTrials.gov no. NCT01657942) included 17 participants (mean age, 64 years ± 6 [SD]; all male) who were treated for prostate cancer using MRgFUS in whom DWI was performed immediately after treatment. Ablation contours from computed thermal dosimetry and DWI as drawn by two blinded radiologists were compared against the reference standard of ablation assessment, posttreatment contrast-enhanced nonperfused volume (NPV) contours. The ability of each method to predict the ablation zone was analyzed quantitively using Dice similarity coefficients (DSCs) and mean Hausdorff distances (mHDs). Results DWI revealed a hyperintense rim at the margin of the ablation zone. While DWI accurately helped predict treatment margins, thermal dose contours underestimated the extent of the ablation zone compared with the T1-weighted NPV imaging reference standard. Quantitatively, contour assessment between methods showed that DWI-drawn contours matched postcontrast NPV contours (mean DSC = 0.84 ± 0.05 for DWI, mHD = 0.27 mm ± 0.13) better than the thermal dose contours did (mean DSC = 0.64 ± 0.12, mHD = 1.53 mm ± 1.20) (P < .001). Conclusion This study demonstrates that DWI, which can visualize the ablation zone directly, is a promising noncontrast method that is robust to treatment-related bulk motion compared with thermal dosimetry and correlates better than thermal dosimetry with the reference standard T1-weighted NPV. Keywords: Interventional-Body, Ultrasound-High-Intensity Focused (HIFU), Genital/Reproductive, Prostate, Oncology, Imaging Sequences, MRI-guided Focused Ultrasound, MR Thermometry, Diffusionweighted Imaging, Prostate Cancer ClinicalTrials.gov Identifier no. NCT01657942 Supplemental material is available for this article. © RSNA, 2024.

Transperineal versus Transrectal MRI/TRUS fusion-guided prostate biopsy in a large, ethnically diverse, and multiracial cohort.

PURPOSE: To compare transperineal (TP) vs transrectal (TR) magnetic resonance imaging (MRI) and transrectal ultrasound (TRUS) fusion-guided prostate biopsy (PBx) in a large, ethnically diverse and multiracial cohort. MATERIALS AND METHODS: Consecutive patients who underwent multiparametric (mp) MRI followed by TP or TR TRUS-fusion guided PBx, were identified from a prospective database (IRB #HS-13-00663). All patients underwent mpMRI followed by 12-14 core systematic PBx. A minimum of two additional target-biopsy cores were taken per PIRADS≥3 lesion. The endpoint was the detection of clinically significant prostate cancer (CSPCa; Grade Group, GG≥2). Statistical significance was defined as p<0.05. RESULTS: A total of 1491 patients met inclusion criteria, with 480 undergoing TP and 1011 TR PBx. Overall, 11% of patients were Asians, 5% African Americans, 14% Hispanic, 14% Others, and 56% White, similar between TP and TR (p=0.4). For PIRADS 3-5, the TP PBx CSPCa detection was significantly higher (61% vs 54%, p=0.03) than TR PBx, but not for PIRADS 1-2 (13% vs 13%, p=1.0). After adjusting for confounders on multivariable analysis, Black race, but not the PBx approach (TP vs TR), was an independent predictor of CSPCa detection. The median maximum cancer core length (11 vs 8mm; p<0.001) and percent (80% vs 60%; p<0.001) were greater for TP PBx even after adjusting for confounders. CONCLUSIONS: In a large and diverse cohort, Black race, but not the biopsy approach, was an independent predictor for CSPCa detection. TP and TR PBx yielded similar CSPCa detection rates; however the TP PBx was histologically more informative.

MRI-guided in-bore biopsy of the prostate - defining the optimal number of cores needed.

BACKGROUND: Numerous studies have shown that magnetic resonance imaging (MRI)-targeted biopsy approaches are superior to traditional systematic transrectal ultrasound guided biopsy (TRUS-Bx). The optimal number of biopsy cores to be obtained per lesion identified on multiparametric MRI (mpMRI) images, however, remains a matter of debate. The aim of this study was to evaluate the incremental value of additional biopsy cores in an MRI-targeted "in-bore"-biopsy (MRI-Bx) setting. PATIENTS AND METHODS: Two hundred and forty-five patients, who underwent MRI-Bx between June 2014 and September 2021, were included in this retrospective single-center analysis. All lesions were biopsied with at least five biopsy cores and cumulative detection rates for any cancer (PCa) as well as detection rates of clinically significant cancers (csPCa) were calculated for each sequentially labeled biopsy core. The cumulative per-core detection rates are presented as whole numbers and as proportion of the maximum detection rate reached, when all biopsy cores were considered. CsPCa was defined as Gleason Score (GS) ≥ 7 (3 + 4). RESULTS: One hundred and thirty-two of 245 Patients (53.9%) were diagnosed with prostate cancer and csPCa was found in 64 (26.1%) patients. The first biopsy core revealed csPCa/ PCa in 76.6% (49/64)/ 81.8% (108/132) of cases. The second, third and fourth core found csPCa/ PCa not detected by previous cores in 10.9% (7/64)/ 8.3% (11/132), 7.8% (5/64)/ 5.3% (7/132) and 3.1% (2/64)/ 3% (4/132) of cases, respectively. Obtaining one or more cores beyond the fourth biopsy core resulted in an increase in detection rate of 1.6% (1/64)/ 1.5% (2/132). CONCLUSION: We found that obtaining five cores per lesion maximized detection rates. If, however, future research should establish a clear link between the incidence of serious complications and the number of biopsy cores obtained, a three-core biopsy might suffice as our results suggest that about 95% of all csPCa are detected by the first three cores.

Development and validation of a deep learning-based method for automatic measurement of uterus, fibroid, and ablated volume in MRI after MR-HIFU treatment of uterine fibroids.

INTRODUCTION: The non-perfused volume divided by total fibroid load (NPV/TFL) is a predictive outcome parameter for MRI-guided high-intensity focused ultrasound (MR-HIFU) treatments of uterine fibroids, which is related to long-term symptom relief. In current clinical practice, the MR-HIFU outcome parameters are typically determined by visual inspection, so an automated computer-aided method could facilitate objective outcome quantification. The objective of this study was to develop and evaluate a deep learning-based segmentation algorithm for volume measurements of the uterus, uterine fibroids, and NPVs in MRI in order to automatically quantify the NPV/TFL. MATERIALS AND METHODS: A segmentation pipeline was developed and evaluated using expert manual segmentations of MRI scans of 115 uterine fibroid patients, screened for and/or undergoing MR-HIFU treatment. The pipeline contained three separate neural networks, one per target structure. The first step in the pipeline was uterus segmentation from contrast-enhanced (CE)-T1w scans. This segmentation was subsequently used to remove non-uterus background tissue for NPV and fibroid segmentation. In the following step, NPVs were segmented from uterus-only CE-T1w scans. Finally, fibroids were segmented from uterus-only T2w scans. The segmentations were used to calculate the volume for each structure. Reliability and agreement between manual and automatic segmentations, volumes, and NPV/TFLs were assessed. RESULTS: For treatment scans, the Dice similarity coefficients (DSC) between the manually and automatically obtained segmentations were 0.90 (uterus), 0.84 (NPV) and 0.74 (fibroid). Intraclass correlation coefficients (ICC) were 1.00 [0.99, 1.00] (uterus), 0.99 [0.98, 1.00] (NPV) and 0.98 [0.95, 0.99] (fibroid) between manually and automatically derived volumes. For manually and automatically derived NPV/TFLs, the mean difference was 5% [-41%, 51%] (ICC: 0.66 [0.32, 0.85]). CONCLUSION: The algorithm presented in this study automatically calculates uterus volume, fibroid load, and NPVs, which could lead to more objective outcome quantification after MR-HIFU treatments of uterine fibroids in comparison to visual inspection. When robustness has been ascertained in a future study, this tool may eventually be employed in clinical practice to automatically measure the NPV/TFL after MR-HIFU procedures of uterine fibroids.

Electrophysiological Cardiovascular Magnetic Resonance (EP-CMR)-Guided Interventional Procedures: Challenges and Opportunities.

PURPOSE OF REVIEW: Cardiovascular magnetic resonance (CMR) imaging excels in providing detailed three-dimensional anatomical information together with excellent soft tissue contrast and has already become a valuable tool for diagnostic evaluation, electrophysiological procedure (EP) planning, and therapeutical stratification of atrial or ventricular rhythm disorders. CMR-based identification of ablation targets may significantly impact existing concepts of interventional electrophysiology. In order to exploit the inherent advantages of CMR imaging to the fullest, CMR-guided ablation procedures (EP-CMR) are justly considered the ultimate goal. RECENT FINDINGS: Electrophysiological cardiovascular magnetic resonance (EP-CMR) interventional procedures have more recently been introduced to the CMR armamentarium: in a single-center series of 30 patients, an EP-CMR guided ablation success of 93% has been reported, which is comparable to conventional ablation outcomes for typical atrial flutter and procedure and ablation time were also reported to be comparable. However, moving on from already established workflows for the ablation of typical atrial flutter in the interventional CMR environment to treatment of more complex ventricular arrhythmias calls for technical advances regarding development of catheters, sheaths and CMR-compatible defibrillator equipment. CMR imaging has already become an important diagnostic tool in the standard clinical assessment of cardiac arrhythmias. Previous studies have demonstrated the feasibility and safety of performing electrophysiological interventional procedures within the CMR environment and fully CMR-guided ablation of typical atrial flutter can be implemented as a routine procedure in experienced centers. Building upon established workflows, the market release of new, CMR-compatible interventional devices may finally enable targeting ventricular arrhythmias.

Clinical Outcomes of Benign Concordant MRI-Guided Breast Biopsies.

INTRODUCTION: MRI-guided biopsy is the standard of care for breast imaging findings seen only by MRI. Although a non-zero false-negative rate of MRI-guided breast biopsy has been reported by multiple studies, there are varied practice patterns for imaging follow-up after a benign concordant MRI guided biopsy. This study assessed the outcomes of benign concordant MRI-guided biopsies at a single institution. PATIENTS AND METHODS: This IRB-approved, retrospective study included patients with MRI-guided biopsies of breast lesions from November 1, 2014, to August 31, 2020. Only image-concordant breast lesions with benign histopathology and those follow up with MRI imaging or excision were included in the study. RESULTS: Out of 275 lesions in 216 patients that met the inclusion criteria, 274 lesions were followed with MRI (range, 5-79 months; average, 25.5 months) and showed benign or stable features upon follow-up. One out of 275 lesions (0.4%), a 6 mm focal nonmass enhancement, was ultimately found to represent malignancy after initial MRI-guided biopsy yielded fibrocystic changes. The lesion was stable at a 6-month follow-up MRI but increased in size at 18 months. Repeat biopsy by ultrasound guidance yielded invasive ductal carcinoma (IDC) and ductal carcinoma in situ (DCIS). CONCLUSION: Breast MRI-guided biopsy has a low false-negative rate. Our single malignancy from a total of 275 lesions gives a false negative rate of 0.4%. This data also supports a longer follow-up interval than the commonly performed 6-month follow-up, in order to assess for interval change.

SCOUT® Localization Using MRI Guidance: Initial Experience.

OBJECTIVE: The Food and Drug Administration approved the MRI-compatible wireless SCOUT localization system in April 2022. The purpose of this study was to evaluate feasibility of SCOUT localization under MRI guidance. We present our initial experience adopting MRI-guided SCOUT localization and compare it to MRI-guided wire localization. METHODS: Electronic medical records and imaging were retrospectively reviewed for all patients who underwent MRI-guided SCOUT or wire localization at our institution between October 2022 and July 2023. Statistical analysis was performed using 2-sample proportion and Wilcoxon rank-sum tests. RESULTS: There were 14 MRI-guided SCOUT and 23 MRI-guided wire localization cases during the study period. All SCOUTs were placed without complication and were considered to be in adequate proximity to the target. There was no significant difference in complication rate (P = .25) or days lapsed from MRI-detected abnormality to surgery (P = .82) between SCOUT and wire cases. SCOUT was placed at time of biopsy for 71% (10/14) of cases. 57% (8/14) of SCOUT cases were used for breast conservation surgery (BCS) compared to 100% (23/23) of wire cases (P <.01), with all 6 SCOUTs not used for BCS placed at time of biopsy. CONCLUSION: MRI-guided SCOUT localization is feasible and offers an alternative to MRI-guided wire localization, with no SCOUT complications reported. SCOUT placement at time of biopsy obviates the need for an additional procedure, but predicting appropriateness is challenging, with 60% (6/10) of SCOUTs placed at time of MRI-guided biopsy not used for subsequent localization surgery.