This case report evaluated the utilization of MR-guided ablation for a refractory painful slow-flow vascular malformation in the plantar aspect of the left foot in a 6-year-old male patient. Initially, MR-guided laser ablation was performed followed by MR-guided cryoablation 5 years later. Procedures were performed under general anesthesia using a 1.5-T Philips MRI system with real-time MRI guidance and monitoring. Pain outcomes were assessed using patient-reported improvement. The lesion diameter was 3.7 cm in the longest axis. The patient achieved sustained pain relief for 5 years after the initial laser ablation then MR-guided cryoablation which has given him 6 years of relief so far. No major complications occurred.

Microwave ablation (MWA) guided by magnetic resonance imaging (MRI) is an effective approach for minimally invasive tumor treatment, combining MRI's soft tissue image contrast and temperature mapping capabilities with the ablative power of microwave energy. However, MRI-guided MWA faces a significant challenge with image noise generated by electromagnetic (EM) interference, which degrades image quality and limits real-time monitoring accuracy. As an initial step to address this problem, we introduce a novel noise characterization method for MRI-guided MWA using EM modeling and simulation. Empirically acquired noise data from controlled phantom experiments was used to develop a theoretical framework for simulating interactions between MRI components and the MWA device. The simulations included key system components: the RF transmit coil, receiver coil, phantom, and MWA probe, and produced a signal-noise map that closely matched the experimental data, effectively replicating observed noise patterns. To demonstrate the use of these simulations for practical applications, we evaluated a simple filter circuit for its effectiveness in reducing noise and validated simulation results through benchwork, which showed significant improvements. The results suggest that this approach provides valuable insights into the underlying noise mechanisms and can inform potential strategies for noise mitigation, offering a practical tool for optimizing MRI-guided MWA and enhancing the efficacy of interventional MRI procedures.

Purpose To evaluate the preliminary technical development, safety, and feasibility of dynamic contrast-enhanced MR lymphangiography (DCE-MRL) performed with nodal and/or dermal injection of gadopiclenol. Materials and Methods This institutional review board-approved retrospective study included consecutive patients referred to the complex lymphatic disorders clinic who underwent DCE-MRL at 1.5 T with gadopiclenol administered via inguinal nodal and/or interstitial transpedal injection. Technical performance, safety, and feasibility for imaging peripheral and central conducting lymphatic anatomy, flow, and drainage were assessed. Results A total of 23 patients (12 female) underwent DCE-MRL with gadopiclenol. Contrast material was administered via inguinal lymph nodes in all patients (23 of 23, 100%) and via interstitial transpedal injection in one patient (one of 23, 4.3%). No serious or nonserious adverse events were observed (0 of 23). Evaluation of central conducting lymphatic anatomy, flow, and drainage into the central venous system was feasible in all patients (23 of 23), and evaluation of lower extremity superficial lymphatic anatomy was feasible in one patient. Signal contrast increased with flip angle up to approximately 35° at 1.5 T, supporting protocol optimization. Preliminary results suggest a near-optimal flip angle of 35° at 1.5 T, a higher flip angle than when using other gadolinium-based contrast agents. Conclusion Dynamic gadopiclenol-enhanced nodal and pedal MR lymphangiography was safe and feasible for imaging peripheral and central conducting lymphatic anatomy. Keywords: Lymphangiography, MR-Angiography, Lymphatic, MR-Dynamic Contrast Enhanced, MR-Contrast Agent Supplemental material is available for this article. © RSNA, 2026.

Objective. The use of Feraheme (ferumoxytol) as a contrast agent in MR-guided focused ultrasound (MRgFUS) tumor ablations could enhance treatment safety and efficacy by improving vascular visualization through strong T1 and T2 shortening effects. However, Feraheme impact on MR thermometry and tissue heating is unclear. This study evaluates the feasibility of incorporating Feraheme into MRgFUS by assessing its impact on MR imaging contrast, MR thermometry, and thermal response in tissue-mimicking phantoms.Approach. Tissue-mimicking phantoms with 0 (baseline), 0.25, and 0.5 mM Feraheme concentrations were prepared using a validated recipe. Acoustic attenuation was measured with a commercial diagnostic ultrasound scanner. MR imaging at 1.5 T was performed to assess gradient-recalled-echo (GRE)-based thermometry signal-to-noise-ratio (SNR), relaxation rates, and relaxivities. MRgFUS system integrated with 1.5 T MRI was used to perform multiple sonications in the phantoms. Temperature elevations and focal heating areas were quantified from proton resonance frequency (PRF) shift thermometry. Experiments were repeated three times over the period of eight-weeks. Separately, temperature-dependent nuclear magnetic resonance (NMR) spectroscopy was performed at 3.0 T in saline-diluted Feraheme phantoms (0, 0.25, 0.5, and 1.0 mM) to assess the influence of Feraheme concentration on PRF coefficients used in MR thermometry.Main results. Phantoms showed nuclear relaxation times (T1: 1178.1 ± 77.8,T2: 103.21 ± 2.45 ms) and attenuation coefficients (0.34-0.36 dB cm-1MHz-1) within expected biological tissue ranges. Relaxivities demonstrated a strong linear dependence on Feraheme concentration (r1: 17.5 ± 0.2,r2: 209.2 ± 2.6 s-1mM-1). Relative to baseline (0 mM) phantom, the SNR of GRE-based thermometry increased by 12.6% at 0.25 mM and decreased by 27.1% at 0.5 mM. Sonications in Feraheme-containing phantoms resulted in statistically higher temperature elevations (p < 0.001) although no statistically significant difference was observed between 0.25 and 0.5 mM. All NMR measurements demonstrated stable, linear PRF temperature dependence (R2= 0.996-0.999), with PRF coefficients (between -0.0074 and -0.0082 ppm °C-1). The resulting thermometry bias was small and predictable (+0.67 and +1.73 per 20 °C at 3.0 T for 0.25 and 0.5 mM).Significance. These findings demonstrate that MR thermometry remains feasible at moderate Feraheme concentrations and support its potential use to enhance visualization of critical vasculature near targeted tissues during MRgFUS.

BACKGROUND:Accurate modeling of the vocal tract requires faithful representation of both soft tissue and bony structures, particularly the teeth and mandible, which directly shape the oral airway and influence speech acoustics. Conventional MRI-based vocal tract models typically exclude teeth due to the inability of standard MRI sequences to image short-T2 tissues, while computed tomography (CT), though effective for bone, involves ionizing radiation and is unsuitable for many speech research applications. OBJECTIVES:To evaluate zero echo time (ZTE) MRI as a radiation-free method for imaging dental and mandibular structures relevant to vocal tract modeling, and to assess the geometric and acoustic consequences of incorporating ZTE-derived teeth into MRI-based vocal tract models. METHODS:Twenty-five participants underwent upper-airway ultra-low-dose CT and MRI, including ZTE-MRI and conventional gradient-echo (GRE) acquisitions. Dental structures were segmented from ZTE-MRI and CT and fused with GRE-derived vocal tract airways to construct hybrid ZTE+GRE-MRI and hybrid CT+GRE-MRI models. For three professional voice users, vocal tract area functions were computed for GRE-only and hybrid models and analyzed using a transmission-line model-based acoustic simulation to estimate vocal tract transfer functions for sustained vowel /a/. RESULTS:ZTE-MRI provided clear visualization of teeth and mandibular structures with pseudo-CT-like contrast. In cases with dental hardware (eg, fillings, implants, and bridges), ZTE-MRI showed localized signal nulling, while CT exhibited more extensive streaking artifacts. Hybrid ZTE+GRE models closely matched CT-based models (area differences ∼1.7-2.3%), whereas GRE-only models overestimated anterior oral cavity airspace (up to ∼16-17%). These geometric differences translated to measurable shifts in acoustic output, particularly in higher-order formant frequencies. CONCLUSIONS:ZTE-MRI enables anatomically complete vocal tract modeling, including supporting radiation-free visualization of dental structures. ZTE-derived teeth produce geometric and acoustic effects comparable to those derived from CT, addressing a key limitation of conventional MRI-based speech modeling and offering a practical alternative for speech and voice research, particularly in populations where radiation exposure is undesirable.

Anemia, defined as a decrease in blood hemoglobin concentration, can be diagnosed noninvasively using CT imaging, typically as an incidental finding, by measuring the attenuation level of blood in major vessels. Dual-energy CT (DECT) and photon-counting-detector CT (PCD-CT) enable reconstruction of virtual monochromatic images (VMI), allowing selection of optimal x-ray energy and accurate measurement of CT number in a wide population to optimize hemoglobin detection in routine clinical practice. However, existing literature primarily focuses on empirical patient studies and retrospective validation of the technique, and therefore, there has been a lack of quantitative analysis on the performance of this technique to detect anemia and the impact of many physical factors such as noise, energy, and optimal thresholds. This study presents a comprehensive analysis of the fundamental physics model, the impact of measurement uncertainty, and the influence of energy-dependent noise on the performance of VMI-based anemia detection. Optimal energies and corresponding best possible performances were quantified by area under the receiver operative characteristic (ROC) curve. The optimal thresholds for the best achievable sensitivity/specificity were determined for two typical noise models in VMI and different severities of anemia.

Precise and accurate staging of rectal cancer is critical for formulating an appropriate treatment plan, including determining the necessity for neoadjuvant therapy and establishing an adequate surgical approach. MRI is the gold standard for locoregional tumor staging, also playing a central role for patients selected for watchful waiting surveillance after total neoadjuvant therapy. Nevertheless, challenges exist from acquisition to interpretation of rectal MRI examinations and, despite societal guidelines, practices vary across institutions. In this paper, we review the optimal technique for acquisition of diagnostic quality rectal MRI and address its existing challenges and unmet needs, encompassing both acquisition and image interpretation.

Objective: Osteoarthritis of the knee is a common cause of pain, functional disability, and reduced quality of life in the elderly. Despite its prevalence, there are limited currently available noninvasive treatment options. MRI-guided focused ultrasound (MRgFUS) is a noninvasive thermal ablation method which is used in a spectrum of musculoskeletal conditions. It is FDA approved for the treatment of painful bone metastases and osteoid osteoma and has been considered for the treatment of other painful conditions such as osteoarthritis. The purpose of this case report is to describe the use of MRgFUS for the treatment of osteoarthritic knee pain in an active 72-year-old male.Method: The patient suffered significant limitations due to lateral knee pain with jogging and walking down the stairs. MRgFUS ablation treatment was performed to the lateral knee, targeting the periosteum in the patients’ area of pain.Results: Following treatment, the patient experienced considerable reduction in his activity limiting symptoms with a duration of at least 6 months.Conclusions: It is important for radiologists to be aware of MRgFUS as an innovative ablation modality. Similar pain reduction was observed in two small series of MRgFUS treatment of knee pain from Japan. MRgFUS appears promising as a safe, noninvasive treatment option for temporary relief of knee pain. This may be particularly valuable for patients who are unwilling or unable to undergo total knee arthroplasty. Future study is needed to assess the efficacy and safety of this treatment in a larger population.

Minimally invasive needle-based interventions are commonly used in cancer diagnosis and treatment, including procedures, such as biopsy, brachytherapy, and microwave ablation. Although MR-guided needle placement offers several distinct advantages, such as high-resolution target visualization and accurate device tracking, one of the primary limitations that affect its widespread adoption is the ergonomic constraints of the closed-bore MRI environment, requiring the patients to be frequently moved in and out to perform the needle-based procedures. This paper introduces a low-profile, body-mounted, MR-guided robot designed to address this limitation by streamlining the operation workflow and enabling accurate needle placement within the MRI scanner. The robot employs piezoelectric linear actuators and stacked Cartesian XY stages to precisely control the position and orientation of a needle guide. A kinematic model and control framework was developed to facilitate accurate targeting. Additionally, clinical workflow for the liver interventions was developed to demonstrate the robot’s capability to replicate existing procedures. The proposed system was validated in benchtop environment and 3T MRI scanner to quantify the system performance. Experimental validations conducted in free space demonstrated a position accuracy of 2.38 ± 0.94 mm and orientation error of 1.40 ± 2.89°. Additional tests to confirm MR-conditionality and MR-guided phantom placements were carried out to assess the system’s performance and safety in MRI suite, yielding a position error of 2.01 ± 0.77 mm and an orientation error of 1.57 ± 1.31°. The presented robot shows exceptional compatibility with a wide range of patients and bore sizes while maintaining clinically significant accuracy. Future work will focus on the validations in dynamic liver environments.

Cryoneedle artifacts are frequently observed in MRI-guided cryoablations, and may obscure visualization of critical anatomy and compromise needle placement accuracy. This work experimentally investigated the contributing factors of these artifacts to identify effective mitigation strategies. Ex vivo porcine tissue with inserted cryoneedles was imaged on a 1.5-Tesla MRI. Fast spin echo (FSE) and spoiled gradient echo (GRE) sequences with echo times from 1.04 to 60 ms and specific absorption rates (SARs) from 0.01 to 2.1 W/kg were used. During MRI, cryoneedle temperatures were monitored using fiber-optic sensors. Configurations with one to three cryoneedles oriented at 0-degree or 45-degree angles to the patient table were investigated. The body coil was used for transmit/receive, both with and without an additional receive-only surface loop coil. Artifact width and intensity were measured for analysis. Cryoneedle artifact widths were unrelated to echo time for both FSE (p = 0.6) and GRE (p = 0.3) and were smaller in GRE than in FSE images (p << 0.05). Artifact widths correlated with cryoneedle temperature elevations (r2 = 0.969, p << 0.05) but were not correlated with SAR (GRE: p = 0.3; FSE: p = 0.5). The artifact intensity with the cryoneedle oriented at 0 degrees increased with a greater number of cryoneedles in the tissue (p = 0.006), and when the surface loop coil was used (p = 0.008). Clinically observed cryoneedle artifacts compromising treatment efficacy can be indicative of tissue radiofrequency heating risk, and effectively mitigated by either using GRE-based sequences or adjusting coil/cryoneedle configurations.

PURPOSE:To investigate thermal injury risks from either radiofrequency (RF)-heating or excessive cooling by high-pressure gas supply lines (HPGSL) during MRI-guided cryoablations, and to identify clinically viable safety precautions. MATERIALS AND METHODS:Ex vivo experiments were performed on a 1.5 Tesla MRI scanner utilizing an MRI conditional cryoablation system. A cryoneedle was inserted into a porcine tissue specimen with an HPGSL routed out of the scanner along the tissue surface and either connected to or disconnected from the ablation system. Experiments were performed with varied layers of operating room (OR) towels or a 2.5 cm thick foam pad between the HPGSL and tissue. Fiber-optic sensors were used to measure temperatures on the HPGSL surface, cryoneedle, and tissue surface during MRI at different specific absorption rates (SAR) or during active freezing. RESULTS:During MRI, tissue surface temperatures nearest the HPGSL increased by up to 40.7 ± 6.9 °C. Tissue temperature increases were reduced to less than 0.1°C as thicker insulation with OR towels or the foam pad were added between the HPGSL and tissue. Disconnecting the HPGSL reduced tissue heating near the HPGSL by 47 %. Tissue heating decreased linearly with decreased SAR. During freezing, the HPGSL cooled to 53.3 ± 1.2 °C below room temperature of 20.9°C. With the foam pad added, the tissue surface cooled to 1.2 ± 0.2 °C below room temperature. CONCLUSION:During MRI-guided cryoablations the HPGSL poses significant patient risks of RF-burns or frostbite, which can be mitigated by ensuring adequate distance between the HPGSL and tissue using insulating materials.

Lymphatic flow and anatomy can be challenging to study, owing to variable lymphatic anatomy in patients with diverse primary or secondary lymphatic pathologic conditions and the fact that lymphatic imaging is rarely performed in healthy individuals. The primary components of the lymphatic system outside the head and neck are the peripheral, retroperitoneal, mesenteric, hepatic, and pulmonary lymphatic systems and the thoracic duct. Multiple techniques have been developed for imaging components of the lymphatic system over the past century, with trade-offs in spatial, temporal, and contrast resolution; invasiveness; exposure to ionizing radiation; and the ability to obtain information on dynamic lymphatic flow. More recently, dynamic contrast-enhanced (DCE) MR lymphangiography (MRL) has emerged as a valuable tool for imaging both lymphatic flow and anatomy in a variety of congenital and acquired primary or secondary lymphatic disorders. The authors provide a brief overview of lymphatic physiology, anatomy, and imaging techniques. Next, an overview of DCE MRL and the development of an MRL practice and workflow in a hybrid interventional MRI suite incorporating cart-based in-room US is provided, with an emphasis on multidisciplinary collaboration. The spectrum of congenital and acquired lymphatic disorders encountered early in an MRL practice is provided, with emphasis on the diversity of imaging findings and how DCE MRL can aid in diagnosis and treatment of these patients. Methods such as DCE MRL for assessing the hepatic and mesenteric lymphatic systems and emerging technologies that may further expand DCE MRL use such as three-dimensional printing are introduced. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Purpose: To evaluate the feasibility of intraoperative neurophysiological monitoring (IONM) during magnetic resonance (MR) imaging-guided ablations and identify strategies to reduce IONM electrode radiofrequency (RF) heating during MR imaging. Materials and Methods: Ex vivo experiments with a porcine tissue phantom simulating a typical high RF heating risk IONM setup during an MR imaging-guided ablation procedure on the shoulder were performed using a 1.5-T scanner. Mutual interference between MR imaging and IONM was evaluated. To assess RF heating risks, 4 pairs of IONM electrodes were inserted into the phantom at regions corresponding to the shoulders, midarm, and wrist. MR imaging of the "shoulder" was performed at 3 different specific absorption rates (SARs) with electrode wires positioned in various geometric configurations. Different combinations of electrode connections to the IONM system were investigated. Temperatures of each electrode were recorded using fiber-optic sensors. Results: Simultaneous IONM readout and MR imaging resulted in distortion of the IONM signal, but interleaving MR imaging and IONM without moving electrodes was feasible. During MR imaging, temperature elevations greater than 60 degrees C at the electrode insertion sites were observed. Temperature reductions were achieved by routing electrode wires along the scanner central axis, reducing the wire length within the scanner bore, or lowering the SAR of the imaging sequence. Altering the electrode connection with the IONM system did not result in consistent changes in RF heating. Conclusions: With electrodes in the scanner bore, interleaving IONM and MR imaging is desired to avoid signal interference, and several strategies identified herein can reduce risk of electrode RF heating during MR imaging-guided ablation.

Motor-evoked potential (MEP) monitoring is an electrophysiologic technique useful for testing peripheral motor nerve integrity during cryoablation cases with risk of nerve injury. Previously, neuromonitoring within the magnetic resonance imaging (MRI) suite for cryoablation has not been performed as magnetic needles are used which could cause magnetic field interactions with neuromonitoring leads. We present the first report of a patient who underwent MEP monitoring during MRI-guided cryoablation of a vascular malformation adjacent to the brachial plexus. We demonstrate that MEPs may be safely and accurately performed by interleaving MRI and MEPs during treatment, reducing the risk of postprocedural complications.

MR-guided microwave ablation (MWA) has proven effective in treating hepatocellular carcinoma (HCC) with small-sized tumors, but the state-of-the-art technique suffers from sub-optimal workflow due to the limited accuracy provided by the manual needle insertions. This paper presents a compact body-mounted MR-conditional robot that can operate in closed-bore MR scanners for accurate needle guidance. The robotic platform consists of two stacked Cartesian XY stages, each with two degrees of freedom, that facilitate needle insertion pose control. The robot is actuated using 3D-printed pneumatic turbines with MR-conditional bevel gear transmission systems. Pneumatic valves and control mechatronics are located inside the MRI control room and are connected to the robot with pneumatic transmission lines and optical fibers. Free-space experiments indicated robot-assisted needle insertion error of 2.6 ± 1.3 mm at an insertion depth of 80 mm. The MR-guided phantom studies were conducted to verify the MR-conditionality and targeting performance of the robot. Future work will focus on the system optimization and validations in animal trials.

The purpose of this study is to investigate the potential of using ultrasound gel to mitigate the risks of skin burn at the insertion site during microwave ablation (MWA) using non-actively cooled applicators. Ex vivo experiments in porcine tissue were conducted using two identical MWA systems. Five MWA scenarios were tested at different applicator insertion depths with an ultrasound gel layer applied at the applicator insertion sites: 8 cm insertion depth with and without 4 cm thick gel, 10 cm insertion depth with and without 2 cm thick gel, and 12 cm insertion depth without gel (reference). In all experiments, temperature elevations at the applicator insertion site on the tissue surface were recorded using thermal sensors in all experiments during 10-min MWA. The application of ultrasound gel and increasing applicator insertion depths resulted in measurable reductions in temperature elevations at the applicator insertion sites. For an insertion depth of 8 cm, the temperature elevations were 39.9 ± 4.7°C and 23.2±6.5°C without and with gel, respectively (P < 0.001). For an insertion depth of 10 cm, the temperature elevations were 20.8 ± 1.5°C and 14.4 ± 1.5°C without and with gel, respectively (P < 0.001). The maximal temperature elevations corresponding to an 8 cm insertion depth with gel were comparable with those corresponding to a 10 cm insertion depth without gel. Similarly, the maximal temperature elevations (12.2 ± 1.8°C) corresponding to 12 cm insertion depth without gel were comparable to those corresponding to 10 cm insertion depth with gel. Applying ultrasound gel at the applicator insertion site can significantly reduce temperature elevations at the tissue surface during MWA procedures.

Purpose: To evaluate the safety and effectiveness of magnetic resonance (MR) imaging-guided cryoablation of prostate cancer metastatic lymph nodes (LNs). Materials and methods: Fifty-two patients with prostate cancer who underwent MR imaging-guided LN ablation from September 2013 to June 2022 were retrospectively reviewed. Of these, 6 patients were excluded because adequate ablation margins (3-5 mm) could not be achieved secondary to adjacent structures. The remaining 46 patients (mean age, 70 years [SD +/- 7]) underwent 55 MR imaging-guided cryoablation procedures of metastatic LNs (25 in the pelvic sidewall, 20 within the pelvic region, and 10 in the abdomen) with procedural intent of complete ablation. Locoregional tumor control (ie, technical success in the target LN) was evaluated on initial follow-up positron emission tomography (PET) scans at a mean of 4 months (SD +/- 2). Preablation and postablation prostate-specific antigen (PSA) levels were recorded. Imaging follow-up continued until a median of 27.5 months (range: 3-108 months). Results: Ninety-five percent (52/55) of treated LNs demonstrated no considerable activity on PET scans at initial follow-up at 4 months (SD +/- 2). PSA decreased to an undetectable level of <0.1 ng/mL after cryoablation in 14 of 46 (30.4%) patients with corresponding lack of activity in 13 of 46 (28.2%) patients on continued PET imaging follow-up. Only 6 of 55 (10.9%) patients had transient adverse events, which all resolved with no long-term sequelae. Conclusions: MR imaging-guided percutaneous cryoablation of metastatic LNs is a safe and technically effective technique for treating metastatic prostate cancer in LNs.

OBJECTIVE To evaluate the safety and tolerability of MRI-guided focused ultrasound (MRgFUS) for the treatment of facet joint mediated pain in human subjects who failed conventional treatment. Secondarily, to evaluate effectiveness of the procedure. SUBJECTS AND METHODS Consecutive patients who underwent MRgFUS at our institution were retrospectively identified. Chart review was performed to obtain relevant clinical and technical data. All patients had chronic low back pain and positive comparative medial branch blocks. RESULTS Twenty-six MRgFUS treatments in 20 patients were included. Mean sonication energy was 1436.6 Joules. The procedure was technically successful in all patients. 29.6% of patients experienced short-term worsening of low back pain immediately following the procedure, all by 1-4 points on a 0-10 scale. One patient (3.8%) reported temporary worsening of pre-existing radicular symptoms after the procedure. Of 21 patients with clinical follow up of at least 3 months available, 12 (57.1%) had >3 months pain relief, 2 (10%) had <3 months benefit, 6 (30%) reported no benefit, and 1 (5%) patient was lost to follow up. In patients who reported at least some benefit to prior conventional RF ablation, 8/10 (80%) benefitted from the MRgFUS procedure. CONCLUSION The current study demonstrates that MRI-guided focused ultrasound ablation of the lumbar facet joints is a safe and tolerable procedure in human subjects, and may provide another option for patients who fail RFA. Over half of all patients received significant durable pain relief, which jumped to 80% for patients who had at least some benefit from prior RF ablations.