Needle Configuration Research Articles

Identification of spread after deliberate intraneural injection in five mammalian species

IntroductionThis research endeavors to investigate the phenomenon of intraneural spread across distinct locations: subcircumneurium, extrafascicular intraneural, intrafascicular intraneural, and intraperineurium after deliberate intraneural injections across five mammalian species. The study...

Optimized needle configuration for operational seed (ONCOSEED) efficiency and deployment for prostate seed implants

Due to anatomical changes between pre-planning and implantation, there exists a need for tools that can streamline the adjustment of needle and seed configurations in low dose rate brachytherapy for prostate cancer. Specifically, upon taking a second ultrasound on the day of treatment, the distribution of seeds and needles will differ drastically from the original plan. Clinics that employ this method must then spend time and resources to generate a workflow to manipulate the original configuration to the new configuration. ONCOSEED extracts data from VariSeed treatment plans, calculating a labor score (LScore) to optimize adjustments to needle configurations. A case study of three simulated VariSeed treatment plans was used to compare the ONCOSEED software to the manual method of generating a workflow. In the same method that was used at the authors’ clinic, several assistants annotated by hand the original plan to convert it to the new plan. The time taken to do so was recorded and compared to the runtime of the software when generating a workflow for the same plan. Results showed that ONCOSEED was on average 28 times faster than generating a workflow by hand. ONCOSEED enhances the efficiency of seed replacement in LDR brachytherapy, promoting the adoption of adaptive brachytherapy practices.

Influence of Syringe Needle Configuration on Micro Particle Generation During Penetration

Influence of Syringe Needle Configuration on Micro Particle Generation During Penetration

Integrating the Rate of Moisture Loss into Needle Retention Testing to Improve the Selection of Balsam Fir (Abies balsamea) for Use as Christmas Trees

A study was conducted to identify balsam fir (Abies balsamea) for use in Christmas tree breeding programs in Northeastern North America. A total of sixty-four phenotypically good trees were identified from a provincial clonal seed orchard in New Brunswick, a multi-aged natural seed production area in Nova Scotia, and an operational plantation in Quebec, Canada. Trees were selected for good growth and form, numbers, and vigour of internodal branches, acceptable crown taper, needle colour, age class, branch angle, needle configuration, and freedom from insects and diseases or deformities, all traits deemed desirable in a Christmas tree. Three branches from each tree were collected at two harvest dates each year, one early and one late during the normal harvesting season in 2020, 2021, and 2022. Qualitative assessments of colour and branch pliability were performed weekly in conjunction with needle loss rub tests. A quantitative assessment of moisture loss was conducted weekly by measuring branch weights. The combination of qualitative and quantitative assessments was used to identify 7 of the 64 trees for which one or more tested branches consistently remained green and pliable, retained the majority of their needles, and lost moisture at a significantly reduced rate in all six testing periods. Grafts of the seven ‘Select’ trees are currently being integrated into seed orchards in the three participating provinces. These second-generation seed orchards are part of breeding programs designed to develop Christmas trees that will perform well under warm fall conditions, an outcome of climate change. The results from this study combined with the progeny testing of the ‘Select’ trees will be used to test for the heritability of needle retention, a key trait for the next generation of Christmas trees in the Northeast.

A Novel Biopsy Needle with Double Concave-Curved Cutting Edges

BackgroundVacuum-assisted biopsy is a minimally invasive sampling technique that relies on rotational cutting as a major tissue retrieving method. A precise diagnosis of the disease requires large, uncrushed samples, which are impacted by the cutting force of the biopsy needle. ObjectivesThis study proposes a novel needle design with double-concave-curved cutting edges, which is more suited for rotational needle cutting. We aimed to optimize the design so that large, undamaged samples could be extracted with minimal cutting force. Materials and MethodsFive-factor experiments were designed using the Taguchi method. Experiments involving rotational needle insertion and tissue sampling were conducted to examine the effects of these variables on the cutting force and sampling quality, respectively. The relationship between the cutting force and sampling quality was analyzed. ResultsFor needle insertion, the optimal design within the design space demonstrated a marked improvement in cutting force from 1.2107 to 0.1888 N. Furthermore, the optimized double concave-curved needle outperformed the blunt needle under the same needle speeds, showing a 24.4% reduction in cutting force (0.1888 vs. 0.2496 N). Increasing rotation-translation ratio or insertion speed would allow for extracting a larger sample (increased up to 21.95% in weight and 17.21% in total length) but may also increase the rotation speed, resulting in sample fragmentation. To simultaneously improve sampling quality and cutting force, a higher K value, larger rotation-translation ratio, and slower insertion speed are suggested. Based on the conditions examined in this study, the optimal needle configuration should include a sharpened cutting edge with a K value of 0.2, a rotation-translation ratio of 8, and an insertion speed of 1 mm/s.

Spectroscopic investigation of atmospheric pressure ‘micro-plasma needle’

Plasma-based sterilization at atmospheric pressure in plasma needle configuration is a recently developing technique that has numerous applications in heat-sensitive materials and enhances biosensor properties. In this study, the capacitively coupled He–O2/Ar and He–N2/Ar mixtures [Formula: see text]-plasma at atmospheric pressure is characterized to find out the optimum condition of plasma-based sterilization for plasma needle. Trace rare gas actinometry based on optical emission spectroscopy has been used to estimate the [O] and [N] atomic densities as a function of discharge parameters i.e., applied pulsing voltage, gases concentration and different flow rates. Ar-1line Ar[Formula: see text] at 750 nm, N-I line [Formula: see text] at 746.8 nm and O-I line [Formula: see text] at 844.6 nm is used to determine the atomic densities of oxygen [O] and nitrogen [N]. Using the Boltzmann plot, the rotational temperature of He–N2/Ar and He–O2/Ar was calculated from the rotational levels of the “first negative system” (FNS) [Formula: see text]. The temperature of the gas increases as the pulsed DC power increases, but it drops as the gas flow rate in the mixture increases. The actinometric results show that both densities increase with applied pulsing voltage and molecular concentration of oxygen and nitrogen. Moreover, it is also observed that emission intensity ratios ([Formula: see text] and [Formula: see text]) also increase with an increase in applied pulsing voltage but they decrease with an increase in flow rate. Based on these results, it is suggested that the optimum conditions, in terms of [O] and [N] atomic densities, for plasma-based sterilization in needle configuration are 4% oxygen and nitrogen concentration at 4 kV applied pulsing voltage and 100[Formula: see text]SCCM flow rate.

Needle Configuration and Application in Cosmetic and Medical Tattooing.

Needles, machines, and techniques used for professional cosmetic and medical tattooing have reached a high level of sophistication. Best utensils are combined with operator's insight - the key to best results. Nowadays, a broad range of different tattoo needles serving different purposes are available. The chapter reviews round, flat, triangular, magnum, nano, polished, textured needles, etc. and their coding and preferred use in practice. The chapter is intended to be the vade mecum for practitioners in the field, the newcomer as well as the experienced, in private setting as well as in hospital.

Digital holographic study of corona wind-assisted evaporation of hydrocarbon from a microliter well

The present study aims to understand the evaporation dynamics of heavy hydrocarbon liquid (cyclohexane) from a circular well cavity under the influence of corona wind. The study explores the effect of corona wind on the modification of vapor phase transport and the evaporation rate from the circular well. Particle image velocimetry is used to characterize the velocity field of the corona wind generated by a needle and plate configuration. Digital holography interferometry is used to decipher the mole fraction distribution of the vapor cloud. Circular well cavities of radius 2.0, 2.5, and 4 mm are studied. The effect of corona wind on the evaporation of different sized well cavities increases with an increase in actuation voltage. The side wall of the cavities influences the distribution of the vapor cloud due to the interaction with the incoming corona wind. More than ten times enhancement of evaporation is observed at 10 kV excitation voltage setting of the corona wind generator. The corona jet-assisted evaporation can be very useful in thin-film evaporative cooling due to its simplicity in design and superior performance.

Combined Whole Prostate Dose Escalation With Focal Gross Disease Boost Using 169Yb-Based Rotating Shield Brachytherapy

<h3>Purpose/Objective(s)</h3> To assess the capability of ¹⁹²Ir-based high-dose-rate brachytherapy (HDR-BT) versus ¹⁶⁹Yb-based rotating shield brachytherapy (RSBT) for simultaneous whole prostate dose escalation with focal boost to dominant intraprostatic lesions (DILs) in a treatment planning study. <h3>Materials/Methods</h3> Twenty-six patients were considered. For each patient, 27 DILs were programmatically generated at locations sampled over a grid of 27 sectors within the planning target volume with a range of volumes sampled from a gaussian probability density function with a mean of 2.4 ± 0.66 cm³, based on the literature. For HDR-BT there were 20-24 clinically placed needles which were supplemented by up to two additional needle positions placed within the DIL at dosimetrically beneficial positions, resulting in a total of 21-26 total needles used. For RSBT a total of 20 needles were used for all patient cases and the needle configuration was not changed based on DIL case. Prescription dose was 20.5 Gy with HDR-BT dose scaled such that 90% of the PTV received 110% of the prescription dose. RSBT dose was scaled to a maximum PTV D_90% while matching the urethra D_10% of HDR-BT. The maximum focal boost dose was defined by normal tissue constraints. <h3>Results</h3> A separate treatment plan was generated for each DIL for each patient, for both RSBT and HDR-BT, a total of 702 unique DIL treatment plans with 26 reference plans. For all combinations of patient and DIL cases, whole prostate dose escalation was 22.6 ± 0.0 Gy (average ± standard deviation) for HDR-BT and 29.9 ± 0.2 Gy for RSBT. The DIL D_90% for HDR-BT was 37.9 ± 4.8 Gy and RSBT DIL D_90% was 60.9 ± 7.2 Gy. The relative difference in dose escalation between whole prostate and focal boost for HDR-BT was 72.7% ± 24.1% and was 102.8% ± 24.3% for RSBT. <h3>Conclusion</h3> Compared to conventional HDR-BT, ¹⁶⁹Yb-based RSBT can provide a relative increase in dose escalation to the whole prostate of 32.6% ± 1.0% with a simultaneous focal gross disease boost of 35.8% ± 11.8%. Without altering the number or positioning of implanted needles, RSBT can achieve simultaneous dose escalation and focal boost for a variety of clinically relevant DIL volumes and locations.

Investigating the Effect of Encapsulation Processing Parameters on the Viability of Therapeutic Viruses in Electrospraying.

The ability of viruses to introduce genetic material into cells can be usefully exploited in a variety of therapies and also vaccination. Encapsulating viruses to limit inactivation by the immune system before reaching the desired target and allowing for controlled release is a promising strategy of delivery. Conventional encapsulation methods, however, can significantly reduce infectivity. The aim of this study was to investigate electrospraying as an alternative encapsulation technique. Two commonly used therapeutic viruses, adenovirus (Ad) and modified vaccinia Ankara (MVA), were selected. First, solutions containing the viruses were electrosprayed in a single needle configuration at increasing voltages to examine the impact of the electric field. Second, the effect of exposing the viruses to pure organic solvents was investigated and compared to that occurring during coaxial electrospraying. Infectivity was determined by measuring the luminescence produced from lysed A549 cells after incubation with treated virus. Neither Ad nor MVA exhibited any significant loss in infectivity when electrosprayed within the range of electrospraying parameters relevant for encapsulation. A significant decrease in infectivity was only observed when MVA was electrosprayed at the highest voltage, 24 kV, and when MVA and Ad were exposed to selected pure organic solvents. Thus, it was concluded that electrospraying would be a viable method for virus encapsulation.

Atmospheric Plasma Supported by TiO2 Catalyst for Decolourisation of Reactive Orange 16 Dye in Water.

PurposeEvery advanced oxidation process (AOP) has its limitations in water purification. Novel designs with simultaneous application of different AOPs can offer better solutions for cleaner water.MethodsWe have comparatively studied two advanced oxidation processes (AOPs) on decolourisation of Reactive Orange 16 (RO 16) azo dye pollutant from water: gas plasma treatment by low power atmospheric pressure plasma using novel plasma needle configuration, and semiconductor heterogeneous photocatalysis using titanium dioxide (TiO2) nanopowders. Additionally, simultaneous application of two advanced oxidation processes on azo dye decolourisation was studied.ResultsIt was found that plasma treatment is very efficient system for the dye removal even for low flow rates (1 slm) of the Ar as feed gas. The presence of 10% of O2 in Ar flow intensified dye oxidation process and shortened required time for total decolourisation. When plasma and catalyst were simultaneously applied, TiO2 was activated with a few Watts plasma source as well as 300 W UV lamp source. The synergic effect of two AOPs was more pronounced for higher feed gas flow rates, resulting in improved decolourisation efficiency.ConclusionPlasma needle can efficiently remove Reactive Orange 16 azo dye from water with a power consumption of only few Watts. With the addition of TiO2 the removal efficiency is significantly improved.Graphic

Is There An Effect On The Development Of Postdural Puncture Headache Of Dural Punction Made With The Spinal Needle In Three Different Orientations During Spinal Anaesthesia Applied To Pregnant Patients?

Background and objectivesPostdural punction headache (PDPH) is a well-known and common complication of spinal anesthesia. The relationship between spinal needle size, configuration and perforation characteristics of the spinal needle and non-essential leak continues to be controversial.MethodsThis prospective-randomized study included 300 patients aged 18–45 years who underwent cesarean section under spinal anesthesia. Spinal anesthesia was performed using a 26G Quincke spinal needle in the L3-4, or L4-5 range in the sitting position. Spinal anesthesia was performed with spinal needle sharp tip opening in the Group 1 patients, right or left laterally in Group 2 and caudal in Group 3, transducing the dural fibers transversely to the subarachnoid area, and directing the free opening of the needle to the spine. The patients were visited in the clinic where they were hospitalized at the 24th and 48th hours postoperatively, and phoned on the 3rd and 5th days after discharge, being questioned for PDPH.ResultsIt was observed that 64% of patients with PDPH developed within the first 24 hrs, 24% between 24 and 48 hrs and 48–72 hrs in 12%. The incidence of PDPH was 14% in Group 1, 8% in Group 2 and 3% in Group 3. This difference between the groups was statistically significant (p: 0.019). The incidence of PDPH was lower in Group 3 than in Group 1 and Group 2.ConclusionWe suggest that when spinal anesthesia is applied in the obstetric patient group if needle opening faces caudal this method will reduce the frequency of PDPH.

Prediction of optimal needle configuration in the first fraction of cervix brachytherapy.

Background and purposeApplying needles in the first brachytherapy (BT) fraction for patients with locally advanced cervical cancer allows for more dose conformality and OAR sparing, but is more challenging than in subsequent fractions, as pre-implant imaging with applicator in situ is lacking. We investigate whether a needle simulation, a fixed needle configuration or a multidisciplinary discussion-based configuration can predict more accurately which applicator needle positions are best suited for use in the first BT fraction.Materials and methodsFor 20 patients we retrospectively determined the “reference” needle configuration (RC) for the first BT fraction using magnetic resonance imaging (MRI) scans with applicator in situ. We simulated a pre-MRI needle configuration (PC) using the MRI made in the fourth week of external beam radiotherapy (EBRT) without applicator in situ. We generated a fixed needle configuration (FC) from the most common RC needles. Using Dice’s similarity coefficient (DSC) we compared each of these needle configurations, including the clinically applied “multidisciplinary consensus” needle configuration (MC), with RC. We considered two scenarios: allowing up to ten needles (scenario 1), and limiting the needle number (scenario 2). The analysis was repeated omitting two mid-ventral needles previously determined as non-essential to treatment planning.ResultsFor both scenarios, the median DSC for PC and FC was higher than for MC (scenario1:DSCPC = 0,78; DSCFC = 0,75; DSCMC = 0,57; scenario 2:DSCPC = 0,74; DSCFC = 0,73; DSCMC = 0,59), while omitting mid-ventral needles resulted in no statistically significant differences in DSC.ConclusionsThe PC or FC method are at least as accurate as the MC, with the FC preferred for efficiency.

Individualized and inverse optimized needle configuration for combined intracavitary-interstitial brachytherapy in locally advanced cervical cancer.

The aim of this study is to address the limitation of combined intracavitary-interstitial (IC/IS) brachytherapy (BT) in locally advanced cervical cancer using standardized applicators and to determine the optimal dose distribution in patients with challenging tumors, innovative methods of customizing and optimizing the IS needle configuration for combined IC/IS BT are proposed and investigated. A software module that could customize the IS needle configuration and subsequently generate the digital model of guiding template for three-dimensional printing was developed and integrated into our in-house treatment planning system for BT. The inverse optimization method based on the technique of mixed-integer linear programming was introduced to determine the needle tracks out of a candidate pool and dwell times at corresponding locations to best meet dose objectives. A treatment planning study was conducted to evaluate the feasibility and performance of the proposed methods. The workflow for combined IC/IS BT with customized and inverse optimized IS needle configuration was presented. Dosimetric results of the treatment planning study showed that sufficient target coverage could be obtained with the customized IS needle configuration for challenging cases. The proposed dose-based optimization method for IS needle configuration was feasible and effective. Improved target coverage and organ-at-risk sparing were achieved using the inverse planning method. Using the proposed methods of customizing and optimizing the IS needle configuration, the limitation in the standardized design of combined IC/IS applicators can be addressed, and sufficient target coverage is obtained in cervical cancer patients with unfavorable tumor topography and/or extra lateral expansion.

Non-parallellism of needles in electroporation: 3D computational model and experimental analysis

PurposeIn electrochemotherapy, flexible electrodes, composed by an array of needles, are applied to human tissues to treat large surface tumors. The positioning of the needles in the tissue depends on the surface curvature. The parallel needle case is preferred, as their relative inclinations strongly affect the actual distribution of electric field. Nevertheless, in some case, small inclinations are unavoidable. The purpose of this paper is to study the electric field distribution for non-parallel needles.Design/methodology/approachThe effect of electrode position is evaluated systematically by means of numerical models and experiments on phantoms for two different angles (5° and 30°) and compared with the case of parallel needles. Potato model was used as phantom, as this tissue becomes dark after few hours from electroporation. The electroporation degree was gauged from the color changings on the potatoes.FindingsThe distribution of electric field in different needle configuration is found by means of finite element analysis (FEA) and experiments on potatoes. The electric field level of inclined needles was compared with parallel needle case. In particular, the electric field distribution in the case of inclined needles could be very different with respect to the one in the case of parallel needles. The degree of enhancement for different inclinations is visualized by potato color intensity. The FEA suggested that the needle parallelism has to be maintained as possible as if the tips are closer to each other, the electric field intensity could be different with respect to the one in the case of parallel needles.Originality/valueThis paper analyzes the effect of inclined electrodes considering also the non-linearity of tissues.

Electrical Treeing in Cable Insulation under Different HVDC Operational Conditions

Electrical treeing (ET) can irreversibly deteriorate the insulation of polymeric power cables leading to a complete failure. This paper presents the results of an experimental investigation into the effects of unipolar and polarity reversing DC voltages on electrical tree (ET) and partial discharge (PD) behavior within high voltage direct current (HVDC) cross linked polyethylene (XLPE) cable insulation. A double needle configuration was adopted to produce non-uniform electric fields within the insulation samples, potentially leading to electrical trees. The development of trees was monitored through an optical method and the associated partial discharge signals were measured through an electrical detection technique, simultaneously. The analysis of the results shows reasonable relation between the formation of ETs and the type of the applied voltages. The polarity reversing attribute of the test voltages has a pronounced effect on formation and growth of electrical trees. This implicates an interaction between the space charges that accumulate within polymeric materials and the operational polarity reversing electric fields, which causes insulation degradation. Therefore, study of influencing HVDC operational parameters on insulation degradations can contribute to improvements in cable design and advancement in insulation diagnostic strategies applicable in HVDC systems leading to more effective asset management.

Electric field distribution and initial jet motion induced by spinneret configuration for molecular orientation in electrospun fibers

Understanding the molecular orientation of electrospun fibers is a key challenge for tailoring fiber properties. The studies of electric field distribution, and the motion of the initial portion of the polymer jet, are of interest for clarifying molecular orientation in fibers during electrospinning. In this work, we study the impact of electric field distribution and the initial jet motion induced by two kinds of spinneret configurations, referred to as a needle configuration and a hole configuration, on molecular orientation in electrospun PEO fibers. Using FE-SEM, FTIR and WAXD techniques, the fiber diameter and molecular orientation of the fibers prepared with the needle electrospinning system and the hole electrospinning system are characterized. To explore jet stretching and chain orientation during the spinning process, electric field simulation and high-speed photography are performed to obtain the electric field characteristics and to measure the initial jet velocities for the needle and the hole systems. Our results reveal the higher electric field strength around the spinneret and the larger initial jet velocities, which depend on the spinneret configuration, result in the higher degree of molecular orientation in fibers.

A fast inverse treatment planning strategy facilitating optimized catheter selection in image-guided high-dose-rate interstitial gynecologic brachytherapy.

Interstitial high-dose rate (HDR) brachytherapy is an important therapeutic strategy for the treatment of locally advanced gynecologic (GYN) cancers. The outcome of this therapy is determined by the quality of dose distribution achieved. This paper focuses on a novel yet simple heuristic for catheter selection for GYN HDR brachytherapy and their comparison against state of the art optimization strategies. The proposed technique is intended to act as a decision-supporting tool to select a favorable needle configuration. The presented heuristic for catheter optimization is based on a shrinkage-type algorithm (SACO). It is compared against state of the art planning in a retrospective study of 20 patients who previously received image-guided interstitial HDR brachytherapy using a Syed Neblett template. From those plans, template orientation and position are estimated via a rigid registration of the template with the actual catheter trajectories. All potential straight trajectories intersecting the contoured clinical target volume (CTV) are considered for catheter optimization. Retrospectively generated plans and clinical plans are compared with respect to dosimetric performance and optimization time. All plans were generated with one single run of the optimizer lasting 0.6-97.4 s. Compared to manual optimization, SACO yields a statistically significant (P ≤ 0.05) improved target coverage while at the same time fulfilling all dosimetric constraints for organs at risk (OARs). Comparing inverse planning strategies, dosimetric evaluation for SACO and "hybrid inverse planning and optimization" (HIPO), as gold standard, shows no statistically significant difference (P > 0.05). However, SACO provides the potential to reduce the number of used catheters without compromising plan quality. The proposed heuristic for needle selection provides fast catheter selection with optimization times suited for intraoperative treatment planning. Compared to manual optimization, the proposed methodology results in fewer catheters without a clinically significant loss in plan quality. The proposed approach can be used as a decision support tool that guides the user to find the ideal number and configuration of catheters.

A Novel Methodology for Bio-electrospraying Mesenchymal Stem Cells that Maintains Differentiation, Immunomodulatory and Pro-reparative Functions

Mesenchymal stem cells (MSCs) are an important cell source for tissue engineering (TE) and cell therapies for several reasons including ease of isolation from multiple tissues, uncomplicated ex vivo culture, ability to self-renew and differentiate into numerous cell types, MSC/immune cell interactions and pro-reparative properties. Current MSC therapies involve administration via intravenous (I.V.) injection. However, this can result in MSC entrapment and failure to target injured site. In TE, artificial 3D constructs are being investigated as strategies for direct delivery of MSCs to a target area. However, these constructs have numerous limitations including lack of cell infiltration, poor cell functionality and limited diffusion of nutrients and oxygen through the scaffolds. We are investigating the jetting methodology bio-electrospraying (BES) as an alternative strategy for MSCs delivery in vivo that may overcome obstacles associated with I.V. injections and scaffold transplantation. For BES in vivo, low voltages, stable jetting and a single needle configuration are highly desirable. A commercially available electrospray apparatus Spraybase® was used to electrospray mouse bone marrow-derived MSCs (mBMSCs) at low voltages (~ 3–6 kV) in vitro. Stable jetting conditions with a single needle at these low voltages were established by employing a ring-shape electrode for potential difference, specific culture medium and the use of high mBMSCs numbers to overcome viscosity difficulties. The viability and functionality of the mBMSCs following BES was determined by analysing expression of specific surface markers, multilineage differentiation, suppression of T- cell activation and pro-reparative capabilities. We show that mBMSCs post-BES functioned similarly to non-bio-electrospray (non-BES) control mBMSCs for all parameters examined. This methodology may subsequently enable targeted delivery of MSCs to an injury site in vivo and potentially avoid the complications associated with MSCs entrapment and the limitations associated with artificial scaffolds.

Effect of Twisted Fiber Anisotropy in Cardiac Tissue on Ablation with Pulsed Electric Fields.

BackgroundAblation of cardiac tissue with pulsed electric fields is a promising alternative to current thermal ablation methods, and it critically depends on the electric field distribution in the heart.MethodsWe developed a model that incorporates the twisted anisotropy of cardiac tissue and computed the electric field distribution in the tissue. We also performed experiments in rabbit ventricles to validate our model. We find that the model agrees well with the experimentally determined ablation volume if we assume that all tissue that is exposed to a field greater than 3 kV/cm is ablated. In our numerical analysis, we considered how tissue thickness, degree of anisotropy, and electrode configuration affect the geometry of the ablated volume. We considered two electrode configurations: two parallel needles inserted into the myocardium (“penetrating needles” configuration) and one circular electrode each on epi- and endocardium, opposing each other (“epi-endo” configuration).ResultsFor thick tissues (10 mm) and moderate anisotropy ratio (a = 2), we find that the geometry of the ablated volume is almost unaffected by twisted anisotropy, i.e. it is approximately translationally symmetric from epi- to endocardium, for both electrode configurations. Higher anisotropy ratio (a = 10) leads to substantial variation in ablation width across the wall; these variations were more pronounced for the penetrating needle configuration than for the epi-endo configuration.For thinner tissues (4 mm, typical for human atria) and higher anisotropy ratio (a = 10), the epi-endo configuration yielded approximately translationally symmetric ablation volumes, while the penetrating electrodes configuration was much more sensitive to fiber twist.ConclusionsThese results suggest that the epi-endo configuration will be reliable for ablation of atrial fibrillation, independently of fiber orientation, while the penetrating electrode configuration may experience problems when the fiber orientation is not consistent across the atrial wall.