Intracerebral hemorrhage (ICH) is a type of hemorrhagic stroke that causes nearly 3 million deaths annually worldwide. Recent clinical trials have indicated minimally invasive surgery (MIS) can improve functional outcomes in patients with lobar ICH. However, despite these promising results challenges persist, namely, tool dexterity and visualization. Previous research has been developing a platform for MR-guided ICH evacuation using a concentric tube robot (CTR), and in this study we present the first-ever in vivo ICH evacuation with an MR-guided CTR. The CTR is a three degree of freedom (DoF) robot mounted to a 4-DoF stereotactic frame. The robot has two non-metallic concentric tubes that are pneumatically actuated. Detailed in this paper are our experimental in vivo workflow, a novel clot production method to be used in ex vivo and in vivo ICH models, and the evacuation outcomes.

The HEALthy Brain and Childhood Development (HBCD) Study is an ongoing longitudinal initiative to understand population-level brain maturation; however, large-scale studies must overcome site-related variance and preserve biologically relevant signal. In addition to diffusion-weighted magnetic resonance imaging images, the HBCD dataset offers analysis-ready derivatives for scientists to conduct their analysis, including scalar diffusion tensor (DTI) metrics in a predetermined set of bundles. The purpose of this study is to characterize HBCD-specific site effects in diffusion MRI data, which have not been systematically reported. In this work, we investigate the sensitivity of HBCD bundle metrics to scanner model-related variance and address these variations with ComBat-GAM harmonization within the current HBCD data release 1.1 across six scanner models. Following ComBat-GAM, we observe zero statistically significant differences between the distributions from any scanner model following FDR correction and reduce Cohen's f effect sizes across all metrics. Our work underscores the importance of rigorous harmonization efforts in large-scale studies, and we encourage future investigations of HBCD data to control for these effects.

Intracerebral hemorrhage (ICH) is a severe type of hemorrhagic stroke that causes nearly 3 million deaths annually. Recent studies have indicated minimally invasive surgery (MIS) can improve functional outcomes in patients with lobar ICH. However, despite these promising results, challenges persist, including tool dexterity and visualization. Our group has been developing a concentric tube robot (CTR) for MR-guided ICH evacuation to address these concerns. We have demonstrated feasibility in prior ex vivo studies. However, to improve clot evacuation, better control strategies, such as closed-loop evacuation control, are needed. In this short paper, we present a modeling strategy for hybrid pneumatic-hydraulic closed-loop evacuation control that is suitable for use in the MR-environment, which requires long pneumatic (for vacuum canister regulation) and hydraulic (for hematoma evacuation) transmission lines. The control strategy is evaluated in a bench-top setting using our CTR and evacuation system. The CTR is used to evacuate an artificial hematoma at volumetric flow rates ranging from 2.5 cm3min to 10 cm3min. Notably, prior to steady-state, the system exhibits a mean evacuation volumetric flow rate error of 0.533 cm3min and a steady-state mean error of 0.229 cm3min.

PURPOSE:To improve single-shot spiral MR-Acoustic Radiation Force Imaging (MR-ARFI)'s robustness to dynamic phase errors and evaluate it in non-human primates (NHPs) with a low-f-number transducer. METHODS:A single-shot spiral MR-ARFI pulse sequence with 2 mm in-plane resolution and alternating displacement phase contrast was implemented to visualize the focus generated by a 128-element ultrasound transducer in the NHP brain. A model-based displacement map calculation was implemented to remove dynamic phase errors. MR-ARFI scans were acquired at pressure levels above and below FDA mechanical index (MI) limits, and reconstructed displacement maps were compared to maps generated by a 3D EPI MR-ARFI scan and a spiral MR-ARFI scan with blocked ultrasound triggering. RESULTS:The proposed sequence and processing detected focal tissue displacements of 160 nm at a transcranial mechanical index of 0.96, which the 3D EPI could not detect, and with 9.7 × $$ \times $$ -improved precision. The model-based reconstruction suppressed background phase errors and maximized precision. Alternating contrast yielded displacement maps with 4.9 × $$ \times $$ -improved precision compared to blocked contrast. CONCLUSION:Single-shot spiral MR-ARFI can provide robust focus visualization in MR-guided ultrasound in the brain at MI levels well below the FDA limit.

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.

Purpose: Static field (B-0) inhomogeneities present a major challenge in high-field MRI. Multicoil shimming using independent, local, direct-current (DC) shim coils has emerged as a powerful and flexible technique to address this issue. However, many-turn DC coils can lead to significant mutual coupling with radiofrequency (RF) coils, causing transmit field (B-1(+)) distortions and signal-to-noise ratio degradation. Methods: We introduce an innovative RF-transparent DC coil that performs B-0 shimming while minimizing RF performance impact. The design incorporates float traps to maintain high RF impedance, allowing flexible placement relative to the RF coil without compromising signal-to-noise ratio or affecting B-1(+). We fabricated square-shaped DC coils with float traps for 3T MRI and compared them with conventional DC coils. To demonstrate high Delta B-0/Amp efficiency, we conducted a B-0 shimming experiment around a metal hip implant. Results: Bench tests and MRI experimental results demonstrated that the RF-transparent DC coil effectively minimized RF interference, preserved signal-to-noise ratio, and maintained B-1(+), even when placed near the RF receive coil. Additionally, the DC coil significantly improved B0 homogeneity near metal implants and substantially reduced image distortion. Conclusion: The RF-transparent DC coil offers a flexible, effective solution for managing B-0 inhomogeneities, paving the way for integrating multiturn DC coils in clinical MRI settings without extensive hardware modifications.

In image-guided interventions, fiducial markers are widely used for medical instrument tracking by attaching them to designated positions. However, due to the difficulty of precise marker placement, obtaining an accurate marker-to-object transformation remains technically challenging, particularly with customized markers or those with non-standard geometries. To accurately identify the transformation, this study introduces a novel calibration method achieved by sequentially touching a fixed tip with landmarks on the object. An inverse sample consensus filter was proposed to remove potential measurement outliers and improve the robustness of the calibration result. Validation through simulations and experiments under two tracking modalities demonstrated superior translational accuracy and improved robustness compared to conventional methods. Specifically, the experiment conducted under electromagnetic tracking system demonstrated a translational error of 0.61 ± 0.11 mm and a rotational error of 0.97 ± 0.18°. The experiment using magnetic resonance imaging system demonstrated a translational error of 0.60 mm and a rotational error of 2.81°. A use case with an intracerebral hemorrhage evacuation robot further verified the feasibility of integrating the calibration method into the image-guided workflow. The proposed method achieved sub-millimeter calibration accuracy across different scenarios, demonstrating its effectiveness and strong potential for diverse research and clinical applications.

Intracerebral hemorrhage is a type of hemorrhagic stroke that is caused by the rupture of a cerebral blood vessel. The recent Early Minimally Invasive Removal of Intracerebral Hemorrhage trial has confirmed that minimally invasive surgery (MIS) can improve functional outcomes in patients. Despite its benefits, there are several limitations imposed by the state-of-the-art MIS approaches such as poor device dexterity and limited intraoperative feedback. In this paper, we present the most recent development of an MR-guided concentric tube robot (CTR) for intracerebral hemorrhage evacuation. The contributions of this paper include (i) a method of clot fabrication in an ex vivo ovine sample using an endotracheal catheter equipped with a balloon, (ii) accuracy evaluations of our CTR using the curved portion within the ex vivo sample, and (iii) a comparative study between the straight-only evacuation and an evacuation using the curved portion of the CTR. We find a 30.2% improvement in evacuation efficacy can be obtained with the CTR-based evacuation compared to the straight-only evacuation.

Occipital nerve decompression is effective in reducing headache symptoms in select patients with migraine and occipital neuralgia. Eligibility for surgery relies on subjective symptoms and responses to nerve blocks and Onabotulinum toxin A (Botox) injections. No validated objective method exists for detecting occipital headache pathologies. The purpose of the study is to explore the potential of high-resolution Magnetic Resolution Imaging (MRI) in identifying greater occipital nerve (GON) pathologies in chronic headache patients. The MRI protocol included three sequences targeting fat-suppressed fluid-sensitive T2-weighted signals. Visualization of the GON involved generating 2-D image slices with sequential rotation to track the nerve course. Twelve patients underwent pre-surgical MRI assessment. MRI identified four main pathologies that were validated against intra-operative examination: GON entanglement by the occipital artery, increased nerve thickness and hyperintensity suggesting inflammation compared to the non-symptomatic contralateral side, early GON branching with rejoining at a distal point, and a connection between the GON and the lesser occipital nerve. MRI possesses the ability to visualize the GON and identify suspected trigger points associated with headache symptoms. This case series highlights MRI's potential to provide objective evidence of nerve pathology. Further research is warranted to establish MRI as a gold standard for diagnosing extracranial contributors in headaches.

PURPOSE:Prospective motion correction (PMC) with inductively-coupled wireless NMR markers has been shown to be an effective plug-and-play method for dealing with head motion at 7 Tesla [29,30]. However, technical challenges such as one-to-one identification of three wireless markers, generation of hyper-intense marker artifacts and low marker peak SNR in the navigators has limited the adoption of this technique. The goal of this work is to introduce solutions to overcome these issues and extend this technique to PMC for brain imaging at 3 Tesla. METHODS:PMC with 6 degrees of freedom (DOF) was implemented using a novel ∼8 ms, ultrashort echo time (UTE) navigator in concert with optimally chosen MnCl2 marker samples to minimize marker artifacts. Distinct head coil sensitivities were leveraged to enable identification and tracking of individual markers and a variable flip angle (VFA) scheme and real time filtering were used to boost marker SNR. PMC was performed in 3D T1 weighted brain imaging at 3 Tesla with voluntary head motions in adult volunteers. RESULTS:PMC with wireless markers improved image quality in 3D T1 weighted images in all subjects compared to non-motion corrected images for similar motions with no noticeable marker artifacts. Precision of motion tracking was found to be in the range of 0.01-0.06 mm/degrees. Navigator execution had minimal impact on sequence duration. CONCLUSIONS:Wireless NMR markers provide an accurate, calibration-free and economical option for 6 DOF PMC in brain imaging across field strengths. Challenges in this technique can be addressed by combining navigator design, sample selection and real time data processing strategies.

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.

Stereotactic neurosurgery is a well-established surgical technique for navigation and guidance during treatment of intracranial pathologies. Intracerebral hemorrhage (ICH) is an example of various neurosurgical conditions that can benefit from stereotactic neurosurgery. As a part of our ongoing work toward real-time MR-guided ICH evacuation, we aim to address an unmet clinical need for a skull-mounted frameless stereotactic aiming device that can be used with minimally invasive robotic systems for MR-guided interventions. In this paper, we present NICE-Aiming, a Neurosurgical, Interventional, Configurable device for Effective-Aiming in MR-guided robotic neurosurgical interventions. A kinematic model was developed and the system was used with a concentric tube robot (CTR) for ICH evacuation in (i) a skull phantom and (ii) in the first ever reported ex vivo CTR ICH evacuation using an ex vivo ovine head. The NICE-Aiming prototype provided a tip accuracy of 1.41±0.35 mm in free-space. In the MR-guided gel phantom experiment, the targeting accuracy was 2.07±0.42 mm and the residual hematoma volume was 12.87 mL (24.32% of the original volume). In the MR-guided ex vivo ovine head experiment, the targeting accuracy was 2.48±0.48 mm and the residual hematoma volume was 1.42 mL (25.08% of the original volume).

Magnetic resonance (MR) conditional actuators and encoders are the key components for MR-guided robotic systems. In this article, we present the modeling and control of our MR-safe pneumatic radial inflow motor and encoder. A comprehensive model is developed that considers the primary dynamic elements of the system, including: 1) motor dynamics, 2) pneumatic transmission line dynamics, and 3) valve dynamics. After model validation, we present a simplified third order model that facilitates design of a first order sliding mode controller (TO-SMC). Finally, the motor hardware is tested in a 7T MRI. No image distortion or artifacts were observed. We posit the MR-safe motor and dynamic model will lower the entry barriers for researchers interested in MR-guided robots and promote wider adoption of MR-guided robotic systems.

In this abstract we present initial feasibility results of a novel pneumatic sensor-based head motion detection and tracking system for MRI. The system comprises of head pad with a built in matrix of air pressure sensors, which replaces the standard head pad in an MRI scan and allows fast sequence agnostic tracking of head motions without the need for navigators, head markers or camera systems. Here, we show initial results for motion detection and head pose estimation in phantom studies using a motion model trained outside the scanner.

Objective: We aim to develop and evaluate an MR-conditional concentric tube robot for intracerebral hemorrhage (ICH) evacuation. Methods: We fabricated the concentric tube robot hardware with plastic tubes and customized pneumatic motors. The robot kinematic model was developed using a discretized piece-wise constant curvature (D-PCC) approach to account for variable curvature along the tube shape, and tube mechanics model was used to compensate torsional deflection of the inner tube. The MR-safe pneumatic motors were controlled using a variable gain PID algorithm. The robot hardware was validated in a series of bench-top and MRI experiments, and the robot's evacuation efficacy was tested in MR-guided phantom trials. Results: The pneumatic motor was able to achieve a rotational accuracy of 0.32°±0.30° with the proposed variable gain PID control algorithm. The kinematic model provided a positional accuracy of the tube tip of 1.39 $ \pm $ 0.54 mm. The robot was able to evacuate an initial 38.36 mL clot, leaving a residual hematoma of 8.14 mL after 5 minutes, well below the 15 mL guideline suggesting good post-ICH evacuation clinical outcomes. Conclusion: This robotic platform provides an effective method for MR-guided ICH evacuation. Significance: ICH evacuation is feasible under MRI guidance using a plastic concentric tube, indicating potential feasibility in future live animal studies.

Migraine Headaches (MH) are the 6th leading cause of years lived with disability worldwide, affect 15% of the US population, and are nearly twice as prevalent in veterans who have been deployed. Our study focuses on pathology of the greater occipital nerve (GON), which occurs with a high prevalence in individuals with a history of trauma (i.e. traffic accidents, explosions, falls). In our pilot MRI scans and operative experience, migraines associated with GON pathology displayed a pathologic thickening of the nerve validated intraoperatively. These results present MRI as a potential biomarker of headache pathologies of MH associated with GON pathology.

PURPOSE:Application of highly selective editing RF pulses provides a means of minimizing co-editing of contaminants in J-difference MRS (MEGA), but it causes reduction in editing yield. We examined the flip angles (FAs) of narrow-band editing pulses to maximize the lactate edited signal with minimal co-editing of threonine. METHODS:The effect of editing-pulse FA on the editing performance was examined, with numerical and phantom analyses, for bandwidths of 17.6-300 Hz in MEGA-PRESS editing of lactate at 3T. The FA and envelope of 46 ms Gaussian editing pulses were tailored to maximize the lactate edited signal at 1.3 ppm and minimize co-editing of threonine. The optimized editing-pulse FA MEGA scheme was tested in brain tumor patients. RESULTS:Simulation and phantom data indicated that the optimum FA of MEGA editing pulses is progressively larger than 180° as the editing-pulse bandwidth decreases. For 46 ms long 17.6 Hz bandwidth Gaussian pulses and other given sequence parameters, the lactate edited signal was maximum at the first and second editing-pulse FAs of 241° and 249°, respectively. The edit-on and difference-edited lactate peak areas of the optimized FA MEGA were greater by 43% and 25% compared to the 180°-FA MEGA, respectively. In-vivo data confirmed the simulation and phantom results. The lesions of the brain tumor patients showed elevated lactate and physiological levels of threonine. CONCLUSION:The lactate MEGA editing yield is significantly increased with editing-pulse FA much larger than 180° when the editing-pulse bandwidth is comparable to the lactate quartet frequency width.

Achieving submillimeter-resolution BOLD fMRI is a challenge since single-shot EPI suffers from long echo times, blurring, and image distortions, while multishot EPI suffers from motion- and respiration-induced shot-to-shot phase errors. In shuttered multishot EPI, data are acquired in each shot after exciting a set of interleaved “shutters” across the imaged slice. This enables high quality reconstructions from each shot, which in turn enables navigator-free shot-wise phase and motion corrections prior to reconstructing a full-FOV image. Herein we describe a full motion- and phase-correcting image reconstruction for dynamic shuttered EPI and validate it in head motion and BOLD fMRI experiments.

PURPOSE:To achieve high-resolution multishot echo-planar imaging (EPI) for functional MRI (fMRI) with reduced sensitivity to in-plane motion and between-shot phase variations. METHODS:Two-dimensional radiofrequency pulses were incorporated in a multishot EPI sequence at 7T which selectively excited a set of in-plane bands (shutters) in the phase encoding direction, which moved between shots to cover the entire slice. A phase- and motion-corrected reconstruction was implemented for the acquisition. Brain imaging experiments were performed with instructed motion to evaluate image quality for conventional multishot and shuttered EPI. Temporal stability was assessed in three subjects by quantifying temporal SNR (tSNR) and artifact levels, and fMRI activation experiments using visual stimulation were performed to assess the strength and distribution of activation, using both conventional multishot and shuttered EPI. RESULTS:In the instructed motion experiment, ghosting was lower in shuttered EPI images without or with corrections and image quality metrics were improved with motion correction. tSNR was improved by phase correction in both conventional multishot and shuttered EPI and the acquisitions had similar tSNR without and with phase correction. However, while phase correction was necessary to maximize tSNR in conventional multishot EPI, it also increased intermittent ghosting, but did not increase intermittent ghosting in shuttered EPI. Phase correction increased activation strength in both conventional multishot and shuttered EPI, but caused increased spurious activation outside the brain and in frontal brain regions in conventional multishot EPI. CONCLUSION:Shuttered EPI supports multishot segmented EPI acquisitions with lower sensitivity to artifacts from motion for high-resolution fMRI.

Actuators and encoders used in MR-guided robotic interventions are subject to strict requirements to ensure patient safety and MR imaging quality. In this paper, we present an open source computer aided design (CAD) of our MR-safe Pneumatic Radial Inflow Motor and Encoder (PRIME). PRIME is a parametrically designed motor that enables scalability based on torque and speed requirements for a wide range of MR-guided robotic procedures. The design consists of five primary modifiable parameters that define the entire motor geometry. All components of the motor are either 3D printed or available off-the-shelf. Quadrature encoding is achieved using a 3D printed housing and four fiber optic cables. Benchtop experiments were performed to validate the performance of the proposed design. To the best of our knowledge, this is the first open source MR-safe pneumatic motor and encoder in the field. We aim to share the design and manufacturing guidelines to lower the entry barriers for researchers interested in MR-guided robotics.