Coil Placement Research Articles

Optimizing distal and proximal splenic artery embolization with patient-specific computational fluid dynamics

Splenic artery embolization (SAE) has become a favored alternative to splenectomy, offering a less invasive intervention for injured spleens while preserving spleen function. However, our understanding of the role that hemodynamics plays during embolization remains limited. In this study, we utilized patient-specific computational fluid dynamics (CFD) simulations to study distal and proximal embolization strategies commonly used in SAE. Detailed 3D computer models were constructed considering the descending aorta, various major visceral arteries, and the iliac arteries. Subsequently, the blood flow and pressure associated with different coil placement locations in proximal embolization were studied considering the collateral vessels. Coil induced variations in pressure fields were quantified and compared to baseline. The coil induced flow stagnation was also quantified with particle residence time. Distal embolization was modeled with Lagrangian particle tracking and the effect of particle size, release location, and timing on embolization outcome was studied. Our findings highlight the crucial role of collateral vessels in maintaining blood supply to the spleen following proximal embolization. It was demonstrated that coil location can affect distal pressure and that strategic coil placement guided by patient-specific CFD simulations can further reduce this pressure as desired. Additionally, the results point to the critical roles that particle size, release timing, and location play in distal embolization. Our study provides an early attempt to use patient-specific computer modeling for optimizing embolization strategies and ultimately improving patient outcomes during SAE procedures.

Power enhancement of vibration energy harvesters by way of magnetic flux gradient analysis of electromagnetic induction

This study proposes strategies to enhance the conversion of mechanical energy to electrical energy in cylindrical electromagnetic induction-type vibration energy harvesters (VEH) using disc or ring-shaped magnets and ring-shaped coils. The rationale behind these strategies has been substantiated by an analysis of magnetic flux gradients based on simulations. In particular, the utilization of a repulsive magnet pair and a yoke has been proposed to maximize the magnetic flux gradient at the coil winding position by manipulating the magnetic flux path. Simulation results confirm that the use of a yoke can produce a nearly 5.8-fold increase in power consumption at the external load. Additionally, the study demonstrates that the positioning and thickness settings of the coil are critical for improving the electrical output based on the spatial distribution of the magnetic flux gradient. Within the same magnet topology, points where power generation is not feasible due to a zero magnetic flux gradient are identified, besides a nearly 5.3-fold increase in observed power generation depending on coil placement. Given the structural feasibility of VEH implementation, a design for a moving magnet VEH utilizing ring magnets with a yoke enclosure is proposed, demonstrating that it can generate power at nearly 85% of the level attributed to using disc magnets.

Real-time estimation of the optimal coil placement in transcranial magnetic stimulation using multi-task deep learning

Transcranial magnetic stimulation (TMS) has emerged as a promising neuromodulation technique with both therapeutic and diagnostic applications. As accurate coil placement is known to be essential for focal stimulation, computational models have been established to help find the optimal coil positioning by maximizing electric fields at the cortical target. While these numerical simulations provide realistic and subject-specific field distributions, they are computationally demanding, precluding their use in real-time applications. In this paper, we developed a novel multi-task deep neural network which simultaneously predicts the optimal coil placement for a given cortical target as well as the associated TMS-induced electric field. Trained on large amounts of preceding numerical optimizations, the Attention U-Net-based neural surrogate provided accurate coil optimizations in only 35 ms, a fraction of time compared to the state-of-the-art numerical framework. The mean errors on the position estimates were below 2 mm, i.e., smaller than previously reported manual coil positioning errors. The predicted electric fields were also highly correlated (r> 0.97) with their numerical references. In addition to healthy subjects, we validated our approach also in glioblastoma patients. We first statistically underlined the importance of using realistic heterogeneous tumor conductivities instead of simply adopting values from the surrounding healthy tissue. Second, applying the trained neural surrogate to tumor patients yielded similar accurate positioning and electric field estimates as in healthy subjects. Our findings provide a promising framework for future real-time electric field-optimized TMS applications.

A comprehensive numerical approach to coil placement in cerebral aneurysms: mathematical modeling and in silico occlusion classification.

Endovascular coil embolization is one of the primary treatment techniques for cerebral aneurysms. Although it is a well-established and minimally invasive method, it bears the risk of suboptimal coil placement which can lead to incomplete occlusion of the aneurysm possibly causing recurrence. One of the key features of coils is that they have an imprinted natural shape supporting the fixation within the aneurysm. For the spatial discretization, our mathematical coil model is based on the discrete elastic rod model which results in a dimension-reduced 1D system of differential equations. We include bending and twisting responses to account for the coils natural curvature and allow for the placement of several coils having different material parameters. Collisions between coil segments and the aneurysm wall are handled by an efficient contact algorithm that relies on an octree based collision detection. In time, we use a standard symplectic semi-implicit Euler time stepping method. Our model can be easily incorporated into blood flow simulations of embolized aneurysms. In order to differentiate optimal from suboptimal placements, we employ a suitable in silico Raymond-Roy-type occlusion classification and measure the local packing density in the aneurysm at its neck, wall region and core. We investigate the impact of uncertainties in the coil parameters and embolization procedure. To this end, we vary the position and the angle of insertion of the micro-catheter, and approximate the local packing density distributions by evaluating sample statistics.

Induction heating simulation for aircraft RTM toolings

Aircraft CFRP parts as sharklets are produced in resin transfer molding (RTM) tooling. The parts need to be heated up homogenously over the whole area with a constant temperature. The complex shape and accessibility of the tooling make it hard to introduce a common heating system. In addition, the heat must be transferred through the Invar metal tooling structure onto the CFRP. Infrared lamp, air fan and microwave heating are concepts in development. Electrical heating layer mats and cages are laborious in applying. Induction has the advantage of contact-less, efficient, and fast heating. Induction heating was tested for the structural bonding of CFRP frames and stringers showing high bonding strengths. To apply this technology for the RTM tooling, the placement and distance of the induction coils is important. Simulation can help to find the right adjustments and power needed for induction heating. With the program COMSOL the surface and the coils are modeled, and the numerically structured net is divided in small tetrahedron and quadratic sub elements. Since there is no magnetic streamline in the middle of the coil-section, a symmetric halving of the structure is applied as a boundary condition. The temperature-time development and the distance of the coils are simulated in 2D and 3D. Due to the material properties of the magnetic flux concentrator (MFC), higher flux concentration of the magnetic field occurred only in 2D. The results are validated by experiments and are in good agreement.

USING ARTIFICIAL NEURAL NETWORKS TO IMPROVE THE EFFICIENCY OF TRANSFORMERS USED IN WIRELESS POWER TRANSMISSION SYSTEMS FOR DIFFERENT COIL POSITIONS

This study uses magnetic resonance-based coupling theory to study the various placements of transmitter and receiver coils in wireless power transfer (WPT) systems. Various coil placements are examined to show where high efficiency can be achieved within the air gap. Basic characteristics such as self-inductance, mutual inductance, and coupling coefficient were calculated. Artificial neural networks (ANNs) in WPT are a powerful technique for predicting performance characteristics. Using ANNs provides an excellent method for streamlining the design process and reducing time-consuming calculations. To quickly determine and optimize coil design, this study compares recent research on ANN applications in WPT and the performance of different types of ANNs in WPT systems. An artificial neural network (ANN) was trained to predict the magnetic properties of a wireless power transfer (WPT) device. Appropriate cost functions have been implemented to train the ANN properly. It was shown that the trained ANN can effectively reproduce the data obtained by the finite element method (FEM). The results show an effective power transmission at different coil placements, with decreased efficiency observed after a certain distance. These data will help determine the proposed WPT system's air gap and angular limits.

Enhancing precision in vascular embolization: evaluating the effectiveness of the intentional early detachment technique with detachable coils in complex cases

BackgroundThis study aimed to assess the effectiveness and versatility of an intentional early detachment technique with detachable coils in addressing challenging vascular embolization scenarios. This novel approach aims to provide an alternative method for achieving precise coil placement when standard methods of detachable coil placement are ineffective owing to vascular anatomy or limited available equipment.Materials and methodsThis retrospective study included 11 patients (nine males and two females; median age, 77 years) who underwent embolization procedures between October 2021 and December 2023 using the intentional early detachment technique through 1.6-Fr or 1.3-Fr microcatheters. In this technique, detachable coils were intentionally detached within the microcatheter and placed through saline flushing. The technique’s technical success, complications, and clinical success were evaluated.ResultsThe technique was applied in three distinct scenarios: tortuous vascular anatomy (four cases), inadequate system backup (three cases), and 1.3-Fr microcatheter use (four cases). The technical and clinical success rates were 100%. No complications were observed, and no cases of coil migration or malpositioning.ConclusionThe intentional early detachment technique is valuable for interventional radiologists and offers a solution for challenging vascular embolization scenarios. Its application is limited to specific circumstances; however, it can significantly enhance coil placement in complex cases, thereby contributing to improved patient care.Graphical

Verification of neuronavigated TMS accuracy using structured-light 3D scans

Objective. To investigate the reliability and accuracy of the manual three-point co-registration in neuronavigated transcranial magnetic stimulation (TMS). The effect of the error in landmark pointing on the coil placement and on the induced electric and magnetic fields was examined. Approach. The position of the TMS coil on the head was recorded by the neuronavigation system and by 3D scanning for ten healthy participants. The differences in the coil locations and orientations and the theoretical error values for electric and magnetic fields between the neuronavigated and 3D scanned coil positions were calculated. In addition, the sensitivity of the coil location on landmark accuracy was calculated. Main results. The measured distances between the neuronavigated and 3D scanned coil locations were on average 10.2 mm, ranging from 3.1 to 18.7 mm. The error in angles were on average from two to three degrees. The coil misplacement caused on average a 29% relative error in the electric field with a range from 9% to 51%. In the magnetic field, the same error was on average 33%, ranging from 10% to 58%. The misplacement of landmark points could cause a 1.8-fold error for the coil location. Significance. TMS neuronavigation with three landmark points can cause a significant error in the coil position, hampering research using highly accurate electric field calculations. Including 3D scanning to the process provides an efficient method to achieve a more accurate coil position.

Preoperative coil localization for spinal surgery is accurate, safe and effective: a single-centre initial experience.

This is a retrospective, descriptive study of consecutive patients undergoing novel preoperative pushable coil localization for spinal surgery, in order to evaluate its feasibility, safety and accuracy. Consecutive patients who underwent pre-operative coil marking for spinal surgery at our institution from May 2018 to July 2021 were included. Data were collected for coil placement, accuracy, complications and fluoroscopy usage. Patient demographic and relevant perioperative and procedural data were also collected. A total of 34 patients were identified of which 32 (94%) had complete data and imaging at last clinical follow up, with a mean duration of 13.9 months. There were no incorrect level surgeries performed. There were no coil-related complications found in our cohort. Preoperative coil placement is an accurate, safe and well-tolerated method for level localization in spinal surgeries.

Endobronchial coil lung volume reduction performed on patients with emphysema dominant COPD: Long term follow-up results.

Chronic obstructive pulmonary disease (COPD) is a commonly seen, preventable, and treatable disease with permanent respiratory symptoms and air entrapment that is caused by particle exposure. In case of limited response to traditional treatment protocols, lung volume reduction may be performed in patients with emphysema dominant patterns. In this study, long term follow-up results of the patients who had been operated on by minimal invasive bronchoscopic lung volume reduction surgery by coil placement were reported. Records of the patients operated on by coil placement were retrospectively investigated, and pulmonary function test (PFT), echocardiography (ECHO), six-minute walking test (6MWT), tomography images, ventilation scintigraphy, and clinical summaries were evaluated. Out of 34 initial candidates, 18 patients were included in the study. Wilcoxon signed-rank test and Spearman's rho were utilized to compare interventions and follow-up testing. The average age of 18 patients was 62 (50-74) years, and except for one patient, all were males (n= 17). Fifteen patients were operated bilaterally, and the rest were unilaterally operated, with an average of 10 coils placed per coil placement. An average of 90 days was between bronchoscopic coil placement, with a follow-up duration of 45 days in between. Mean total follow-up duration was 794 (± 424) days. Pneumonia and pneumonitis were seen in 33% of patients within the first month. Mortality from respiratory causes was found to be 11%, while mortality from all causes was found to be 22%. Statistical difference was observed regarding 6MWT after bronchoscopic volume reduction when compared the initial preoperative values. However, this difference was later lost statistically at the second follow-up performed after the completion of both sides. A benefit in improved resting saturation was observed after the second procedure, which was not evident after unilateral intervention. However, similiar to 6MWT, this benefit was lost at the second follow-up, with resting saturation instead being effected negatively. No difference was observed in PFT results; however, a correlation was seen between FEV1 and walking distance. No specific correlation had been seen in the ECHO evaluation. Benefits regarding 6MWT and resting saturation were observed in patients undergoing minimal invasive bronchoscopic lung volume reduction surgery with coils. This benefit was evident in the short term but was lost as the follow-up duration increased. A relatively high morbidity and mortality rate was also present, further stating the risky nature of pulmonary intervention, even minimally invasive procedures, on patients with COPD.

EUS-guided thrombin injection and coil implantation for gastric varices: feasibility, safety, and outcomes

Gastric varices (GVs) are reported in up to 20% of patients with portal hypertension, and bleeding is often more severe and challenging than esophageal variceal bleeding. Data are limited on prophylaxis of GV bleeding or management in the acute setting, and different techniques are used. This study evaluated outcomes after EUS-guided placement of coils in combination with thrombin to manage GVs. We retrospectively reviewed all patients treated with combination EUS-guided therapy with coils and thrombin between October 2015 and February2020. Twenty patients underwent 33 procedures for GV therapy; 16 of 20 (80%) had type 1 isolated GVs and 4 patients had type 2 gastroesophageal varices. The median follow-up was 842 days (interquartile range [IQR], 483-961). Seventeen patients (85%) had underlying cirrhosis, the most common etiologies being alcohol-related liver disease and nonalcoholic steatohepatitis. The median Child-Pugh score was 6 (IQR, 5-7). In 11 patients (55%), the indication was secondary prophylaxis to prevent recurrent bleeding; in 2 of 20 patients (10%), the bleeding was acute. Technical success was achieved in 19 patients (95%). During follow-up, the obliteration of flow within the varices was achieved in 17 patients (85%). The 6-week survival rate was 100%, and 2 adverse events, recurrent bleeding at day 5 and at day 37, were reported; both recurrent bleeding events were successfully managed endoscopically. EUS-guided GV obliteration combining coil placement with thrombin, in our experience, was technically safe with good medium-term efficacy. A multicenter randomized controlled trial comparing different treatment strategies is desirable to understand options better.

Patients with a high defibrillation threshold: Approaches to management.

Implantable cardioverter-defibrillators (ICDs) have revolutionized the prognosis for patients at elevated risk of ventricular tachyarrhythmias. For safety, defibrillation should be effective with a minimum of 10 J below the device's maximum energy. While modern ICDs rarely deliver ineffective shocks in primary prevention, the surge in managing severe heart failure patients has led to an increased number of patients with high defibrillation thresholds (DFTs). This article elucidates the potential causes of high DFT, including clinical factors, lead and device placement, the presence of a Left Ventricular Assist Device (LVAD), prolonged ventricular arrhythmias, shock vectors, waveform tilt, medications, and manufacturer-specific options. We also detail management strategies, highlighting alternative shock coil placements, practical recommendations, and case studies from our institution. Our management algorithm suggests addressing preventable causes, re-evaluating coil positions, considering non-invasive system modifications, upgrading to a higher-capacity device, and adding extra coil(s).

Endoscopic ultrasound in portal hypertension: navigating venous hemodynamics and treatment efficacy.

Portal hypertension-related complications increase mortality in patients, irrespective of its etiology. Classically, endoscopic ultrasound (EUS) was used to assess the portal venous system and collaterals, considering size and hemodynamic parameters, which correlate with portal hypertension (PH) and related complications. Furthermore, therapeutic EUS guides treatment interventions, such as embolization of the gastric varices through coil placement and tissue adhesive injection, yielding encouraging clinical results. Recently, the direct measurement of portal pressure, emerging as an alternative to hepatic venous pressure gradient, has shown promise, and further research in this area is anticipated. In this review, we aimed to provide a detailed description of various possibilities for diagnosing vascular anatomy and hemodynamics in PH and actual knowledge on the EUS usefulness for PH vessel-related complications. Also, future promises for this field of endo-hepatology are discussed.

Identifying Locations for Transcranial Magnetic Stimulation Coil Placement For Deep Brain Structures

Stimulation of deep brain structures with transcranial magnetic stimulation (TMS) is the premier mode of non-invasive brain stimulation (NIBS). Currently, there is little support for the application of TMS in modulating deeper brain structures. This study validates the use of TMS for a set of 8 deep brain structures shown to alleviate symptoms of certain conditions when stimulated. 200 sets of T1-weighted and T2-weighted MRIs were processed using the SimNIBS headreco pipeline. Then, 200 TMS optimization simulations were run for each brain structure, which generated 200 3D coordinates for each structure representing the best TMS coil placement locations on the scalp for stimulation. This data was analyzed using K-means and agglomerative clustering methods to find the overall best coil placement locations. Overall, this study validates the use of TMS to stimulate these brain structures and finds the optimal parameters for stimulation.

In-vivo verified anatomically aware deep learning for real-time electric field simulation

Objective. Transcranial magnetic stimulation (TMS) has emerged as a prominent non-invasive technique for modulating brain function and treating mental disorders. By generating a high-precision magnetically evoked electric field (E-field) using a TMS coil, it enables targeted stimulation of specific brain regions. However, current computational methods employed for E-field simulations necessitate extensive preprocessing and simulation time, limiting their fast applications in the determining the optimal coil placement. Approach. We present an attentional deep learning network to simulate E-fields. This network takes individual magnetic resonance images and coil configurations as inputs, firstly transforming the images into explicit brain tissues and subsequently generating the local E-field distribution near the target brain region. Main results. Relative to the previous deep-learning simulation method, the presented method reduced the mean relative error in simulated E-field strength of gray matter by 21.1%, and increased the correlation between regional E-field strengths and corresponding electrophysiological responses by 35.0% when applied into another dataset. In-vivo TMS experiments further revealed that the optimal coil placements derived from presented method exhibit comparable stimulation performance on motor evoked potentials to those obtained using computational methods. The simplified preprocessing and increased simulation efficiency result in a significant reduction in the overall time cost of traditional TMS coil placement optimization, from several hours to mere minutes. Significance. The precision and efficiency of presented simulation method hold promise for its application in determining individualized coil placements in clinical practice, paving the way for personalized TMS treatments.

Abstract 088: Treatment of a Ruptured AVM with Inflow Aneurysms: Mixed approach using coil and liquid embolization

Introduction Arteriovenous malformations(AVMs) are high‐flow vascular abnormalities characterized by direct communications between arteries and veins of various complexities. Cerebral AVMs may manifest with new‐onset seizures or intraparenchymal (IPH) or subarachnoid hemorrhages (SAH). Life‐threatening bleeds may occur from the AVM nidus or associated aneurysms. We report a patient with hemorrhage from a complex AVM that included a prominent nidus and large inflow aneurysms requiring several endovascular techniques for treatment. Methods N/A Results A 35 year old male patient newly arrived from the Philippines with a history of hypertension presented to the hospital after being found unresponsive at home with frothing from the mouth and incontinence. The patient regained consciousness in the ER, complaining of a posterior headache which he had been experiencing for a week. NIHSS of 0 was noted with no neurological deficits. CT‐head revealed extensive SAH in interhemispheric falx anterior to and outlining the entire corpus callosum with intraventricular extension. CT‐ angiogram demonstrated a prominent AVM with a well‐developed nidus situated to the left of midline about the posterior corpus callosum. Two large inflow aneurysms, felt to be the rupture site, projecting from the proximal left pericallosal artery were also demonstrated. An incidental ACA aneurysm was also noted. Cerebral angiography redemonstrated these findings as well as the drainage of the AVM primarily through the straight sinus. Graded as Spetzler Martin 4. Common femoral approach was used. An access catheter was passed into the left ICA. The pericallosal artery was accessed with a detachable tip microcatheter which was further advanced past the inflow aneurysms into the main pedicle feeding the AVM nidus. The inflow aneurysms were accessed and embolized with coils using a second microcatheter prior to AVM embolization. This sealed off access to the aneurysms and parent vessel against liquid agent backflow. Onyx‐18 was then injected into the main AVM pedicle under a blank roadmap. Extensive but partial filling of the AVM was noted anteriorly but full embolization of the posterior aspect of the nidus was not achieved. Finally coiling of the ACA aneurysm was performed after accessing the right ICA. An MRI with and without contrast was performed and an expected acute infarction in the left ACA territory was observed. A repeat angiogram was performed a week later revealing posterior cerebral artery and posterior choroidal branches feeding the posterior 1/3 of the AVM. Embolization of three posterior feeding pedicles was subsequently performed utilizing dilute NBCA. Because of coil impaction the proximal pericallosal inflow aneurysm required re‐treatment with further coil placement 8 months after initial treatment. The patient has regular angiograms to monitor the AVM, which appears stable without significant residual shunting. Conclusion Ruptured AVMs are fatal events requiring careful treatment to prevent further bleeding while preserving viable brain tissue. AVMs are fragile formations of vessels which can receive collaterals from multiple targets and often have associated high risk features like inflow aneurysms. Accordingly endovascular treatment may require a mixture of techniques to ensure adequate and safe embolization. Regular monitoring of these structures and adjacent vessels is required to prevent any poor outcomes.

Fast and accurate computational E-field dosimetry for group-level transcranial magnetic stimulation targeting

Transcranial magnetic stimulation (TMS) is used to study brain function and treat mental health disorders. During TMS, a coil placed on the scalp induces an E-field in the brain that modulates its activity. TMS is known to stimulate regions that are exposed to a large E-field. Clinical TMS protocols prescribe a coil placement based on scalp landmarks. There are inter-individual variations in brain anatomy that result in variations in the TMS-induced E-field at the targeted region and its outcome. These variations across individuals could in principle be minimized by developing a large database of head subjects and determining scalp landmarks that maximize E-field at the targeted brain region while minimizing its variation using computational methods. However, this approach requires repeated execution of a computational method to determine the E-field induced in the brain for a large number of subjects and coil placements. We developed a probabilistic matrix decomposition-based approach for rapidly evaluating the E-field induced during TMS for a large number of coil placements due to a pre-defined coil model. Our approach can determine the E-field induced in over 1 Million coil placements in 9.5 h, in contrast, to over 5 years using a brute-force approach. After the initial set-up stage, the E-field can be predicted over the whole brain within 2–3 ms and to 2% accuracy. We tested our approach in over 200 subjects and achieved an error of <2% in most and <3.5% in all subjects. We will present several examples of bench-marking analysis for our tool in terms of accuracy and speed. Furthermore, we will show the methods’ applicability for group-level optimization of coil placement for illustration purposes only. The software implementation link is provided in the appendix.

Navigating complexity: a comprehensive review of microcatheter shaping techniques in endovascular aneurysm embolization

The endovascular intervention technique has gained prominence in the treatment of intracranial aneurysms due to its minimal invasiveness and shorter recovery time. A critical step of the intervention is the shaping of the microcatheter, which ensures its accurate placement and stability within the aneurysm sac. This is vital for enhancing coil placement and minimizing the risk of catheter kickback during the coiling process. Currently, microcatheter shaping is primarily reliant on the operator's experience, who shapes them based on the curvature of the target vessel and aneurysm location, utilizing 3D rotational angiography or CT angiography. Some researchers have documented their experiences with conventional shaping methods. Additionally, some scholars have explored auxiliary techniques such as 3D printing and computer simulations to facilitate microcatheter shaping. However, the shaping of microcatheters can still pose challenges, especially in cases with complex anatomical structures or very small aneurysms, and even experienced operators may encounter difficulties, and there has been a lack of a holistic summary of microcatheter shaping techniques in the literature. In this article, we present a review of the literature from 1994 to 2023 on microcatheter shaping techniques in endovascular aneurysm embolization. Our review aims to present a thorough overview of the various experiences and techniques shared by researchers over the last 3 decades, provides an analysis of shaping methods, and serves as an invaluable resource for both novice and experienced practitioners, highlighting the significance of understanding and mastering this technique for successful endovascular intervention in intracranial aneurysms.

Percutaneous transvenous coil embolization (PTCE) for treatment of single extrahepatic portosystemic shunt in dogs

BackgroundThere is limited information regarding percutaneous transvenous coil embolization (PTCE) for single extrahepatic portosystemic shunt (PSS). This study aimed to describe the procedure and outcome of PTCE in dogs with a single extrahepatic PSS. Forty-two privately owned dogs were included in this study. All dogs were diagnosed with extrahepatic PSS by computed tomography (CT). Preoperative CT images were used to evaluate the diameter of the PSS for coil placement. A multipurpose balloon catheter was percutaneously inserted into the PSS via the jugular vein, and transvenous retrograde portography (TRP) and measurement of blood pressure in the PSS (pPSS) were performed during balloon inflation; one or more embolization coils were implanted via the catheter.ResultsIn most cases, preoperative median fasting and postprandial serum total bile acid (TBA) concentrations were high (fasting, 86.5 μmol/L [ 3.7–250.0 μmol/L]; postprandial, 165.5 μmol/L [ 1.5–565.0 μmol/L]). CT revealed that 30 dogs had left gastrophrenic shunt; eight had left gastroazygos shunt; and one each had left gastrocaval, splenocaval, splenophrenic, and left colocaval shunt. TRP revealed that intrahepatic portal vascularity was clearly detectable in all dogs. The median values of pPSS before and during the balloon occlusion were 4.8 mmHg [2.0–13.0 mmHg] and 8.6 mmHg [5.0–18.0 mmHg], respectively. The median number and diameter of coils used were 2 coils [1 – 5 coils] and 8.0 mm [4.0 – 12.0 mm], respectively. The median times of irradiation and PTCE were 9 min [4–26 min] and 40 min [23–75 min], respectively. The median fasting and postprandial TBAs significantly decreased to 8.2 μmol/L [0.3–45.1 μmol/L, n = 38, p = 0.0028] and 19.8 μmol/L [0.3–106.7 μmol/L, n = 38, p = 0.0018], respectively, approximately 1 month after PTCE. The clinical success rate of PTCE without requirement for a second surgery was 95.2% (40/42 dogs). During revision surgery, one dog underwent surgical ligation and, in another dog, an ameroid constrictor was placed.ConclusionsPTCE was clinically effective in treating single extrahepatic PSS in dogs. Preoperative CT and TRP prior to PTCE might be clinically valuable for choosing the size of embolization coils, deciding the appropriate location of coil implantation, and estimating the number of coils to be implanted. PTCE is a promising alternative to conventional surgical procedures for single extrahepatic PSS in dogs.

Reflecting the causes of variability of EEG responses elicited by cerebellar TMS

Recently, Fong et al. published EEG responses in cerebral cortex elicited by cerebellar TMS (cbTMS) (Fong et al., 2023), which differ from our recently identified cbTMS-EEG responses (Gassmann et al., 2022). Fong et al. argued that this discrepancy is due to coil placement unsuitable for eliciting cerebellar brain inhibition (CBI) in our study. However, we reliably elicited CBI in our subjects. Consequently, this leads to a compelling discussion on possible reasons for the observed discrepancies in cbTMS-evoked EEG responses. Reliably measuring cbTMS-evoked EEG responses could become an important neurophysiological tool to test effective cerebellum-to-cortex connectivity.