Magnetic Resonance Imaging Guidance Research Articles

P-85. Impact of Magnetic Resonance Imaging on Re-Amputation Rates in Diabetic Foot Osteomyelitis

Abstract Background Diabetic foot infections constitute 20% of hospital admissions and result in 80% of amputations annually. It is noteworthy that diabetes is more prevalent among U.S. veterans compared to the general population due to age, exposure to environmental factors during service, and mental health conditions which can contribute to unhealthy behaviors and increased risk of diabetes. Magnetic resonance imaging (MRI) is considered the imaging modality of choice for evaluating diabetic foot osteomyelitis given its higher sensitivity. A staging MRI, may decrease subsequent amputation rates in diabetics with osteomyelitis.Table 1:Patient characteristics and comorbiditiesMRI=magnetic resonance imaging, MI=myocardial infarction, CHF=congestive heart failure, PVD=peripheral vascular disease, CVD=cardiovascular disease, DM=diabetes mellitus, COPD=chronic obstructive pulmonary disease, PUD=peptic ulcer disease, HIV=human immunodeficiency virus Methods A retrospective chart review was conducted to analyze the risk of re-amputation in patients with diabetic foot osteomyelitis hospitalized between 2005 and 2022. Patients with and without MRI guided treatment were compared. The primary outcome was the rate of re-amputation at specific time intervals: 30-day, 60-day, 180-day, and 365-day. Charlson Comorbidity Index scores were calculated for all patients, and a multivariable logistic regression was used to calculate odds ratios and confidence intervals. Veterans were included if they had a diabetic foot infection complicated by osteomyelitis, and requiring amputation. Patients were excluded if they had an initial above-the-knee amputation (AKA) or below-the-knee amputation (BKA), since these are generally definitive treatment for osteomyelitis.Table 2:Treatment CharacteristicsMRI=magnetic resonance imaging, MSSA=methicillin susceptible Staphylococcus aureus, MRSA=methicillin resistant Staphylococcus aureus Results There were 1,463 patients based on ICD-10 codes, of which 475 patients underwent amputation. MRI guided therapy occurred in 106 patients. Multivariable logistic regression analysis revealed a 10-fold decrease in the odds of re-amputation within 30 days (OR=0.1; CI 0.01-0.72), a 3-fold decrease within 60 days (OR=0.32; CI 0.13-0.83), and a 2-fold decrease within the 180-day and 365-day (OR=0.51; CI 0.28-0.94 and OR=0.52; CI 0.3-0.9, respectively) intervals when MRI guidance was utilized.Table 3:Bivariate analysis of re-amputationsMRI=magnetic resonance imaging Conclusion These findings suggest that incorporating a pre-amputation MRI into the diagnostic and treatment approach for osteomyelitis associated with diabetic foot infections may reduce the risk for subsequent amputations.Table 4:Multivariable analysis of re-amputationsMRI= magnetic resonance imaging Disclosures All Authors: No reported disclosures

Hierarchically Engineered Self-Adaptive Nanoplatform Guided Intuitive and Precision Interventions for Deep-Seated Glioblastoma.

Glioblastoma multiforme (GBM), particularly the deep-seated tumor where surgical removal is not feasible, poses great challenges for clinical treatments due to complicated biological barriers and the risk of damaging healthy brain tissue. Here, we hierarchically engineer a self-adaptive nanoplatform (SAN) that overcomes delivery barriers by dynamically adjusting its structure, surface charge, particle size, and targeting moieties to precisely distinguish between tumor and parenchyma cells. We further devise a SAN-guided intuitive and precision intervention (SGIPi) strategy which obviates the need for sophisticated facilities, skilled operations, and real-time magnetic resonance imaging (MRI) guidance required by current MRI-guided laser or ultrasound interventions. In a preclinical intracranial GBM mouse model, SGIPi-based photodynamic therapy effectively impedes GBM progression with high tumor specificity and significantly extends overall survival. Moreover, the SGIPi potentiates chemotherapy while minimizing adverse effects; it eradicates intracranial GBM lesions in 100% cases solely through Temozolomide chemotherapy. This SGIPi strategy holds potential to improve the clinical management of GBM, with the possibility of extending survival rates and even achieving complete remission, and may inspire research focus from expensive and complex hardware development to simpler, delivery-based GBM interventions.

An MRI-guided stereotactic neurosurgical robotic system for semi-enclosed head coils.

Magnetic resonance imaging (MRI) offers high-quality soft tissue imaging without radiation exposure, which allows stereotactic techniques to significantly improve outcomes in cranial surgeries, particularly in deep brain stimulation (DBS) procedures. However, conventional stereotactic neurosurgeries often rely on mechanical stereotactic head frames and preoperative imaging, leading to suboptimal results due to the invisibility and the contact with patient's head, which may cause additional harm. This paper presents a frameless, MRI-guided stereotactic neurosurgical robotic system. The robot features a seven-degree-of-freedom (7-DOF) remote center of motion, with five DOFs for preoperative trajectory alignment to the target lesion and two DOFs for defining the depth and twisting motion of the needle during insertion, thus to minimize tissue damage. The system employs interactive MRI guidance for real-time visualization of the puncture process, showing great potential in reducing surgery time, enhancing targeting accuracy, and improving safety. Experiments were conducted on the proposed system to evaluate signal-to-noise ratio (SNR) and geometric distortion. During the simultaneous operation and imaging, the system demonstrated less than 10.02% SNR attenuation and less than 0.1% geometric distortion, ensuring image usability. The free-space positioning accuracy of the system was evaluated using a laser tracker, revealing a tip position repeatability error within 0.3 ± 0.1mm.

Evaluating the Accuracy and Efficiency of Imaging Modalities in Guiding Ablation for Metastatic Spinal Column Tumors: A Systematic Review.

Spinal metastases are a frequent and serious complication in cancer patients, often causing severe pain, instability, and neurological deficits. Thermal ablation techniques such as radiofrequency ablation (RFA), microwave ablation (MWA), and cryoablation (CA) have emerged as minimally invasive treatments. These techniques rely on precise imaging guidance to effectively target lesions while minimizing complications. This systematic review aims to compare the efficacy of different imaging modalities-computed tomography (CT), magnetic resonance imaging (MRI), fluoroscopy, and mixed techniques-in guiding thermal ablation for spinal metastases, focusing on success rates and complications. A systematic literature search was conducted across PubMed, OVID, Google Scholar, and Web of Science databases, yielding 3733 studies. After screening, 51 studies met the eligibility criteria. Data on success rates, tumor recurrence, complications, and patient outcomes were extracted. Success was defined as no procedure-related mortality, tumor recurrence or expansion, or nerve injury. This systematic review followed PRISMA guidelines and was registered with PROSPERO (ID: CRD42024567174). CT-guided thermal ablation demonstrated high success rates, especially with RFA (75% complete success). Although less frequently employed, MRI guidance showed lower complication rates and improved soft-tissue contrast. Fluoroscopy-guided procedures were effective but had a higher incidence of nerve injury and incomplete tumor control. Mixed imaging techniques, such as CBCT-MRI fusion, showed potential for reducing complications and improving targeting accuracy. CT remains the most reliable imaging modality for guiding thermal ablation in spinal metastases, while MRI provides enhanced safety in complex cases. Fluoroscopy, although effective for real-time guidance, presents limitations in soft-tissue contrast. Mixed imaging techniques like CBCT-MRI fusion offer promising solutions by combining the advantages of both CT and MRI, warranting further exploration in future studies.

TMOD-27. RECURRENT GLIOBLASTOMA AFTER LASER ABLATION OF THE PRIMARY TUMOR IN A PRECLINICAL ORTHOTOPIC MODEL EXHIBIT INCREASED GENETIC SIGNATURES OF CELL CYCLE AND CELL MOTILITY

Abstract Image-guided laser interstitial thermal therapy (LITT) is a minimally invasive tumor cytoreductive treatment for recurrent gliomas and tumors in eloquent loci. We have adapted this technique to develop an image-guided glioblastoma (GBM) ablation model, its recurrence and have tested the efficacy of imaging biomarkers in evaluating tumor ablation and recurrence. The cytopathology and molecular signatures of the primary and recurrent tumors were compared. Immune-compromised female rats were implanted with U251N tumor cells in one brain hemisphere (n=20). Tumor growth was monitored using magnetic resonance imaging (MRI). When tumors reached about 4 mm in diameter, they were ablated using a clinical LITT system (Visualase®), under MRI guidance. Five other rats implanted with U251N tumors were used as unablated controls. MRI data were acquired at 24 h post-LITT, and at 2 and 4 weeks. Rats were sacrificed for histopathology at 2 and 4 weeks, and brain sections stained for hematoxylin and eosin, human major histocompatibility complex, Ki67, a cell proliferation marker and sex determining region Y)-box 2 (SOX2), a stem cell transcription factor. An additional cohort of rats with primary (n=4) and post-LITT recurrent (n=4) U251N tumors were used for analysis of their molecular composition using RNA-Seq approach. In the treated groups, MRI showed little tumor tissue at 24 h, evidence of recurrence at 2 weeks and significant tumor tissue at 4 weeks. Tumor DCE-MRI parameters showed elevated intra-tumoral vascular permeability (i.e., Ktrans) values at pre-LITT imaging, that shifted to peri-ablation periphery at 24 h. A trend of progressive decrease in Ktrans was seen until 1-week post-ablation. Increasing Ktrans values at 2 weeks and after 4 weeks coincided with tumor recurrence. RNA-Seq data showed that cell cycle, cellular movement and inflammatory disease genes were the most differentially expressed genes in the recurrent tumors suggesting increased infiltration may primarily underlie treatment resistance.

Magnetic resonance imaging-guided single-fraction preoperative radiotherapy for early-stage breast cancer (the RICE trial): feasibility study

BackgroundOver the past decade, the adoption of screening programs, digital mammography, and magnetic resonance imaging (MRI) has increased early-stage breast cancer diagnosis rates. Mortality rates have decreased due to early detection and improved treatments, including personalized therapies. Accelerated partial-breast irradiation (APBI) is emerging as a convenient and effective treatment for some patients, with studies exploring its preoperative use. Preoperative APBI, especially with MRI guidance, offers improved tumor targeting and potentially reduced side effects. Magnetic Resonance Imaging-Guided Single-Fraction Pre-Operative Radiotherapy for Early-Stage Breast Cancer (RICE trial) aims to assess the feasibility and efficacy of MRI-guided single-dose radiotherapy (RT) for early-stage breast cancer.MethodsThe RICE study is a prospective, single-arm study evaluating single-fraction preoperative, APBI treatment for patients with early-stage breast cancer using a magnetic resonance imaging linear accelerator (MRI linac). Eligible patients enrolled in this study will have a core biopsy to confirm estrogen receptor-positive and HER2-negative sub-type. RT planning will use a planning computed tomography (CT) co-registered with a MRI with the patient in either the supine or prone position. For the diagnostic workup, [18F] fluorodeoxyglucose positron emission tomography/CT ([18F] FDG PET/CT) and [18F] fluoroestradiol positron emission tomography/CT ([18F] FES PET/CT) will be performed prior to treatment. Thirty patients will receive a single ablative RT dose of 21 Gray to the tumor. Pre-treatment and post-treatment MRI scans will be acquired at baseline and 5 weeks post-RT respectively. Breast-conserving surgery will be scheduled for 6 weeks after APBI treatment using the MRI linac.The primary study endpoint is the successful administration of a single fraction of preoperative breast RT under the guidance of an MRI linac. Secondary endpoints include evaluating the utility of MRI, [18F] FDG PET/CT, and [18F] FES PET/CT as a non-invasive method for assessing treatment response in patients undergoing single-fraction preoperative APBI.ConclusionThe RICE trial represents a significant step in breast cancer treatment, offering insights that could lead to treatment protocols with minimized RT appointments and enhanced patient outcomes.Trial registrationThis trial is registered with the Australian New Zealand Clinical Trials Registry (ANZCTR). Registered 31st of May 2021. Registration number: ACTRN12621000659808.

Magnetic Resonance Imaging Guidance for Percutaneous Needle Intervention

Magnetic resonance imaging (MRI) is one of the guiding modalities used for percutaneous needle insertion during interventional procedures. MRI guidance has several advantages, including multiplanar imaging capability, superior soft tissue contrast resolution, and the absence of ionizing radiation. When performing MRI-guided procedures, it is important to understand the suitable MRI systems, instruments, and imaging sequences for intervention. Furthermore, needle artifact characteristics must be fully understood to ensure safe and accurate needle insertion. In this article, we present the fundamental knowledge as regards the use of MRI guidance for percutaneous needle insertion and review its usefulness in representative interventional procedures, such as biopsy and tumor ablation.

Neuroimaging Applications for the Delivery and Monitoring of Gene Therapy for Central Nervous System Diseases.

Neurological disease due to single-gene defects represents a targetable entity for adeno-associated virus (AAV)-mediated gene therapy. The delivery of AAV-mediated gene therapy to the brain is challenging, owing to the presence of the blood-brain barrier. Techniques in gene transfer, such as convection-enhanced intraparenchymal delivery and image-guided delivery to the cerebrospinal fluid spaces of the brain, have led the field into highly accurate delivery techniques, which provide correction of genetic defects in specific brain regions or more broadly. These techniques commonly use magnetic resonance imaging (MRI), computed tomography, and fluoroscopic guidance. Even more, the neuroimaging changes evaluated by MRI, MR spectroscopy, diffusion tensor imaging, and functional MRI can serve as important biomarkers of therapy effect and overall disease progression. Here, we discuss the role of neuroimaging in delivering AAV vectors and monitoring the effect of gene therapy.

Novel ultrathin ferrous sulfide nanosheets: Towards replacing black phosphorus in anticancer nanotheranostics

Biodegradable two-dimensional nanomaterials could be a significant breakthrough in the field of oncology nanotheranostic agents, which are rapidly emerging as promising candidates for tumor theranostic applications. Herein, a novel biodegradable ferrous sulfide nanosheet (FeS NS) is developed. Compared to the traditional photothermal material, black phosphorus nanosheet (BP NS), FeS demonstrates superior degradability and enhanced photothermal performance, and making it ideal for efficient photothermal therapy (PTT) of tumors. In the acidic tumor microenvironment, FeS degrades and releases H2S, which inhibits mitochondrial respiration and ATP production. This process leads to a reduction in heat shock protein expression, lowering the resistance of tumor cells to photothermal stimulation, and improving the efficacy of PTT. The released Fe2+ exhibits efficient peroxidase activity, triggering ferroptosis in tumor cells. Furthermore, due to its superparamagnetic nature, FeS NSs could accumulate at the tumor site and provide a strong magnetic resonance imaging (MRI) signal for imaging-guided tumor therapy. Overall, as a promising alternative to BP, the FeS NSs are a potentially innovative nanotheranostic agent of tumors, offering a synergistic approach to ferroptosis−PTT with MRI guidance.

Development of an algorithm for proton dose calculation in magnetic fields.

The advantages of proton therapy can be further enhanced with online magnetic resonance imaging (MRI) guidance. One of the challenges in the realization of MRI-guided proton therapy (MRPT) is accurately calculating the radiation dose in the presence of magnetic fields. This study aims to develop an efficient and accurate proton dose calculation algorithm adapted to the presence of magnetic fields. An analytical-numerical radiation dose calculation algorithm, Proton and Ion Dose Engine (PRIDE), was developed. The algorithm combines the pencil beam algorithm (PBA) with a novel iterative voxel-based ray-tracing algorithm. The new ray-tracing method uses fewer assumptions and ensures broader applicability for proton beam trajectory prediction in magnetic fields, and has been compared to Wolf's method and Schellhammer's method. The accuracy of PRIDE algorithm was validated on three phantoms and two practical plans (one single-field water plan and one prostate tumor plan) in different magnetic field strengths up to 3.0 T. The validation was performed by comparing the results against the Monte Carlo (MC) simulations, using the global gamma index criteria of 2%/2mm and 3%/3mm with a 10% threshold. PRIDE showed good agreement with MC in homogeneous and slab heterogeneous phantom, achieving gamma passing rates (%GPs) above 99% for 2%/2mm criteria when magnetic field strength is not greater than 1.5 T. Although the agreement decreased for scenarios involving high proton energy (240 MeV) and strong magnetic field (3.0 T), the 2%/2mm %GPs still remained above 98%. In lateral heterogeneous phantom, the accuracy of PRIDE decreased due to the PBA's limitation. For the two practical plans in different magnetic fields, %GPs exceeded 98% and 99% for 2%/2mm and 3%/3mm criteria, respectively. PRIDE can perform efficient and accurate proton dose calculation in magnetic fields up to 3.0 T, and is expected to work as a useful tool for proton dose calculation in MRPT.

Mesoporous Polydopamine Nanotherapeutics for MRI-Guided Cancer Photothermal and Anti-Inflammatory Therapy.

As a burgeoning cancer treatment modality, photothermal therapy (PTT) has shown robust anti-tumor effects. However, it still faces numerous challenges, such as triggering an inflammatory response and potentially increasing the risk of cancer recurrence. To address these concerns, integration of PTT with anti-inflammatory therapies presents a promising approach to enhance the efficacy of cancer treatment and meanwhile reduce the risk of recurrence. In this study, Gd3+ was first chelated with dopamine to create Gd-DA chelates, and then the mesoporous dopamine nanoparticles MX@Arg-Gd-MPDA (MAGM NPs) were synthesized by combining arginine (Arg) and the anti-inflammatory medication meloxicam (MX). The photothermal properties of MAGM NPs were then defined and examined; the in vivo MRI imaging effect, as well as MAGM NPs' anti-cancer and anti-inflammatory efficiency, were tested in a mouse model of breast cancer. The incorporation of Arg doping into MAGM NPs was intended to boost its photothermal conversion efficiency and reactive oxygen species (ROS) scavenging ability. Additionally, synergizing with the anti-inflammatory agent meloxicam (MX) within the nanoparticles aimed to enhance the anti-inflammatory effect following photothermal therapy. Furthermore, gadolinium ions (Gd3+) were chelated into the nanostructure to enable precise T1-T2 dual-mode magnetic resonance imaging (MRI) of the intratumor accumulation profile. This imaging capability was leveraged to guide the implementation of photothermal therapy. Animal experiments demonstrated that MAGM NPs exerted a notable anticancer effect in a 4T1 breast cancer mouse model, under the precise guidance of MRI.

Comparison of treatment results between microvascular decompression and gamma knife radiosurgery in primary trigeminal neuralgia.

This study aims to analyze and evaluate the comparative clinical outcomes associated with microvascular decompression (MVD) and gamma knife radiosurgery (GKRS), focusing on pain relief, pain recurrence, and complications encountered in the treatment of trigeminal neuralgia (TN). Among 155 surgical procedures performed for TN (90 GKRS, and 65 MVD) between March 1997 and December 2020, the exclusion criteria encompassed prior surgical interventions, the presence of other pathological conditions such as tumors, vascular diseases, and multiple sclerosis, as well as patients who were lost to follow-up. Ultimately, 101 patients received their initial treatment for primary TN (47 GKRS, and 54 MVD) and were followed up for more than 1 year. The MVD procedures utilized the suboccipital retrosigmoid sinus approach, whereas GKRS was conducted with MR imaging guidance, employing a single 4mm isocenter, with median GKRS doses of 80 Gy. We retrospectively analyzed patient characteristics, including sites of divisions, distributions of pain, and clinical outcomes. The assessment of outcomes was performed utilizing the Barrow Neurological Institute Pain Intensity Score and the Visual Analog Scale (VAS), with evaluations taking place preoperatively and after 1, 3, 6 and 12 months. Postoperative VAS scores for patients undergoing either MVD or GKRS demonstrated a significant improvement when compared with their preoperative counterparts. The reduction in postoperative VAS scores within the MVD group was significantly more substantial than that observed in patients who underwent GKRS at the initial postoperative evaluations (P = .037). The maintenance of pain relief after MVD proved significantly superior to that following GKRS (P < .01). Both MVD and GKRS present as safe and efficacious therapeutic options for individuals diagnosed with primary TN, though MVD displayed superior initial outcomes in terms of pain relief and its maintenance. However, for older patients or those with medical contraindications to invasive procedures, GKRS emerges as a viable and less invasive alternative for initial treatment in cases of primary TN.

The Transtemporal Isthmus Approach for Insular Glioma Surgery.

Maximal and safe removal of insular gliomas by a transinsular cortex approach is challenging. In this article, a new transtemporal isthmus approach to resect insular gliomas is presented. We retrospectively examined 53 patients with insular glioma who underwent resection through the temporal isthmus approach using magnetic resonance imaging and functional neuronavigation guidance and intraoperative electrophysiological monitoring. Extent of resection was determined using intraoperative magnetic resonance imaging. Fifty-three patients were included for analysis, 30 men and 23 women. The median (range) age was 45 (26-70) years. Tumor laterality was left in 22 patients and right in 31. All tumors involved at least zone III or IV (Berger-Sanai classification system), including zones I-IV were involved in 29 (54.7%) and zones III and IV in 17 (32.0%). Among the 37 low-grade gliomas, preoperative median (IQR) volume was 45.7 (31.8, 60.3) cm 3 , and gross total resection was achieved in 24 (64.9%). Among the 16 high-grade gliomas, preoperative median (IQR) volume was 45.3 (40.1, 54.0) cm 3 , and gross total resection was achieved in 14 (87.5%). The median (IQR) extent of resection of the whole group was 100% (89%-100%). The median (IQR) postoperative Karnofsky performance score 3 months after surgery was 90 (80-90). Mean temporal isthmus width was significantly higher in the affected side (involving tumor) than the contralateral one (21.6 vs 11.3 mm; 95% CI: 9.3 to 11.3, P < .01). Muscle strength was grade 4 or higher, and speech was nearly normal in all patients 3 months after surgery. Insular glioma surgery using the transtemporal isthmus approach can achieve safe and maximum resection. A widened temporal isthmus provides a surgical pathway for transisthmic resection of insular tumor.

Targeting Hydrogel for Intelligent Recognition and Spatiotemporal Control in Cell-Based Therapeutics.

Smart drug platforms based on spatiotemporally controlled release and integration of tumor imaging are expected to overcome the inefficiency and uncertainty of traditional theranostic modes. In this study, a composite consisting of a thermosensitive hydrogel (polyvinyl alcohol-carboxylic acid hydrogel (PCF)) and a multifunctional nanoparticle (Fe3O4@Au/Mn(Zn)-4-carboxyphenyl porphyrin/polydopamine (FAMxP))is developed to combine tumor immunogenic cell death (ICD)/immune checkpoint blockade (ICB) therapy under the guidance of magnetic resonance imaging (MRI) and fluorescence imaging (FI). It can not only further recognize the target cells through the folate receptor of tumor cells, but also produce thermal dissolution after exposure to near-infrared light to slowly release FAMxP in situ, thereby prolonging the treatment time and avoiding tumor recurrence. As FAMxP entered the tumor cells, it released FAMx in a pH-dependent manner. Chemodynamic, photothermal and photodynamic therapy can cause significant ICD in cancer cells. ICB can thus be further enhanced by injecting anti-programmed cell death ligand 1, improving the effectiveness of tumor treatment. The developed PCF-FAMxP composite hydrogel may represent an updated drug design approach with simple compositions for cooperative MRI/FI-guided targeted therapeutic pathways for tumors.

Harnessing the Power of Radiotherapy for Lung Cancer: A Narrative Review of the Evolving Role of Magnetic Resonance Imaging Guidance.

Compared with computed tomography (CT), magnetic resonance imaging (MRI) traditionally plays a very limited role in lung cancer management, although there is plenty of room for improvement in the current CT-based workflow, for example, in structures such as the brachial plexus and chest wall invasion, which are difficult to visualize with CT alone. Furthermore, in the treatment of high-risk tumors such as ultracentral lung cancer, treatment-associated toxicity currently still outweighs its benefits. The advent of MR-Linac, an MRI-guided radiotherapy (RT) that combines MRI with a linear accelerator, could potentially address these limitations. Compared with CT-based technologies, MR-Linac could offer superior soft tissue visualization, daily adaptive capability, real-time target tracking, and an early assessment of treatment response. Clinically, it could be especially advantageous in the treatment of central/ultracentral lung cancer, early-stage lung cancer, and locally advanced lung cancer. Increasing demands for stereotactic body radiotherapy (SBRT) for lung cancer have led to MR-Linac adoption in some cancer centers. In this review, a broad overview of the latest research on imaging-guided radiotherapy (IGRT) with MR-Linac for lung cancer management is provided, and development pertaining to artificial intelligence is also highlighted. New avenues of research are also discussed.

Optimizing Glioma Resection Outcomes: A Systematic Review of Intraoperative Magnetic Resonance Imaging Guidance in Neurosurgery.

This systematic review evaluates the efficacy of intraoperative magnetic resonance imaging (iMRI) in enhancing glioma resection outcomes within neurosurgical procedures. Given the complexity and variability of gliomas, achieving precise and safe resections is challenging, necessitating the use of advanced imaging techniques like iMRI. This technology provides real-time, high-resolution insights during surgery, allowing for adaptations based on surgical dynamics and brain shifts. Our comprehensive search across multiple databases selected five significant studies that collectively demonstrate the beneficial impact of iMRI. These studies highlight its role in significantly improving the extent of tumor resection and suggest potential enhancements in both immediate and long-term patient outcomes. The findings indicate that iMRI facilitates more aggressive yet safe resections, particularly in high-risk glioma cases. However, the implementation of iMRI in clinical practice requires careful consideration of training, resource allocation, and the potential variability in outcomes due to study design heterogeneity. Future research should focus on randomized controlled trials to better understand the cost-effectiveness and long-term benefits of iMRI, promoting its wider adoption in neurosurgical settings.

Motion Accuracy of Pneumatic Stepper Motor-Driven Robotic System Developed for MRI-Guided High-Intensity Focused Ultrasound Treatment of Prostate Disease.

The latest advancement in high-intensity focused ultrasound (HIFU) treatment technology integrates magnetic resonance imaging (MRI) guidance for precise treatment of prostate disease. As conventional electromagnetic motors are not applicable for utilization within MRI scanners, we have developed a prototype robotic system driven by pneumatic stepper motors to control the movement of the HIFU transducer within an intrarectal probe during MRI-guided HIFU treatment procedures. These pneumatic stepper motors were constructed entirely from MRI-compatible plastic materials. Assessment of the robotic system's MRI compatibility was conducted utilizing a 3.0T MRI scanner, revealing no discernible MRI image distortion with a minor decrease in the signal-to-noise ratio (2.8%) during the motor operation. The robotic system enabled the transducer to move inside the probe with two degrees of freedom, allowing both linear and rotational motion. The positional accuracy of the transducer movement was assessed, yielding ±0.20 and ±0.22 mm accuracies in the forward and backward linear movements, respectively, and ±0.79° and ±0.74° accuracies in the clockwise and counterclockwise rotational motions, respectively. Emulation of authentic HIFU procedures involved creating a two-dimensional array of thermal lesions in a tissue-mimicking phantom, achieving positional accuracy within ±1 mm for the generated HIFU focal spots. The prototype robotic system incorporating pneumatic stepper motors fabricated entirely from MRI-compatible plastic materials has demonstrated the requisite positional accuracy necessary for effective HIFU treatment of prostate disease, indicating substantial promise for future clinical application.

Cornerstone for MRI-compatible robots: A continuous pneumatic actuator with easy-to-connect prismatic/revolute and bidirectional encoder modules

The exceptional imaging capability of magnetic resonance imaging (MRI) enables the applications of robot-assisted surgery under MRI guidance. Essential to these robotic systems are the MRI-compatible robotic joint actuators. Among various actuation methods using MRI-compatible materials, pneumatic actuators are considered the most suitable for this application scenario due to their sterility, safety, and reliability. Yet, the current pneumatic actuators are either bulky, inefficient, or cannot achieve accurate bidirectional continuous motion. As a step forward, a novel high-performance continuous MRI-compatible pneumatic motor is proposed, along with quick-connect revolute/prismatic motion output modules and high accurate bidirectional encoder modules. The high performance of the pneumatic rotary and linear actuators are evaluated through experimental testing, where the rotary actuator can provide up to 2 Nm of output torque and over 28 W of output power, while the linear variant can deliver over 50 N of thrust, which surpass the SOTA competitors. Corresponding dynamic models are established and verified via experiments, with a maximum error of only 2.01%. Closed-loop control experiments demonstrate the high control precision and fast response frequency of the proposed pneumatic actuators, promoting the performance of joint actuators of various MRI-compatible surgical robots.

The impact of motion on onboard MRI-guided pencil beam scanned proton therapy treatments

Objective. Online magnetic resonance imaging (MRI) guidance could be especially beneficial for pencil beam scanned (PBS) proton therapy of tumours affected by respiratory motion. For the first time to our knowledge, we investigate the dosimetric impact of respiratory motion on MRI-guided proton therapy compared to the scenario without magnetic field. Approach. A previously developed analytical proton dose calculation algorithm accounting for perpendicular magnetic fields was extended to enable 4D dose calculations. For two geometrical phantoms and three liver and two lung patient cases, static treatment plans were optimised with and without magnetic field (0, 0.5 and 1.5 T). Furthermore, plans were optimised using gantry angle corrections (0.5 T +5° and 1.5 T +15°) to reproduce similar beam trajectories compared to the 0 T reference plans. The effect of motion was then considered using 4D dose calculations without any motion mitigation and simulating 8-times volumetric rescanning, with motion for the patient cases provided by 4DCT(MRI) data sets. Each 4D dose calculation was performed for different starting phases and the CTV dose coverage V 95% and homogeneity D 5%–D 95% were analysed. Main results. For the geometrical phantoms with rigid motion perpendicular to the beam and parallel to the magnetic field, a comparable dosimetric effect was observed independent of the magnetic field. Also for the five 4DCT(MRI) cases, the influence of motion was comparable for all magnetic field strengths with and without gantry angle correction. On average, the motion-induced decrease in CTV V 95% from the static plan was 17.0% and 18.9% for 1.5 T and 0.5 T, respectively, and 19.9% without magnetic field. Significance. For the first time, this study investigates the combined impact of magnetic fields and respiratory motion on MR-guided proton therapy. The comparable dosimetric effects irrespective of magnetic field strength indicate that the effects of motion for future MR-guided proton therapy may not be worse than for conventional PBS proton therapy.

Transcutaneous Ablation of Lung Tissue in a Porcine Model Using Magnetic-Resonance-Guided Focused Ultrasound (MRgFUS).

Focused ultrasound (FUS) is a minimally invasive treatment that utilizes high-energy ultrasound waves to thermally ablate tissue. Magnetic resonance imaging (MRI) guidance may be combined with FUS (MRgFUS) to increase its accuracy and has been proposed for lung tumor ablation/debulking. However, the lungs are predominantly filled with air, which attenuates the strength of the FUS beam. This investigation aimed to test the feasibility of a new approach using an intentional lung collapse to reduce the amount of air inside the lung and a controlled hydrothorax to create an acoustic window for transcutaneous MRgFUS lung ablation. Eleven pigs had one lung mechanically ventilated while the other lung underwent a controlled collapse and subsequent hydrothorax of that hemisphere. The MRgFUS lung ablations were then conducted via the intercostal space. All the animals recovered well and remained healthy in the week following the FUS treatment. The location and size of the ablations were confirmed one week post-treatment via MRI, necropsy, and histological analysis. The animals had almost no side effects and the skin burns were completely eliminated after the first two animal studies, following technique refinement. This study introduces a novel methodology of MRgFUS that can be used to treat deep lung parenchyma in a safe and viable manner.