Spherical Head Research Articles

Elliptical heads result in increased glenohumeral translation along with micro-motion of the glenoid component during axial rotation in total shoulder arthroplasty

IntroductionElliptical-shaped humeral head prostheses have recently been proposed to reflect a more anatomic shoulder replacement. However, its subsequent effect on micro-motion of the glenoid component is still not understood.Materials and methodsSix fresh-frozen, cadaveric shoulders (mean age: 62.7 ± 9.2 years) were used for the study. Each specimen underwent total shoulder arthroplasty using an anatomic stemless implant. At 15°, 30°, 45° and 60° of glenohumeral abduction, 50° of internal and external rotations in the axial plane were alternatingly applied to the humerus with both an elliptical and spherical humeral head design. Glenohumeral translation was assessed by means of a 3-dimensional digitizer. Micro-motion of the glenoid component was evaluated using four high-resolution differential variable reluctance transducer strain gauges, placed at the anterior, posterior, superior, and inferior aspect of the glenoid component.ResultsThe elliptical head design showed significantly more micro-motion in total and at the superior aspect of glenoid component during external rotation at 15° (total: P = 0.004; superior: P = 0.004) and 30° (total: P = 0.045; superior: P = 0.033) of abduction when compared to the spherical design. However, during internal rotation, elliptical and spherical heads showed similar amounts of micro-motion at the glenoid component at all tested abduction angles. When looking at glenohumeral translation, elliptical and spherical heads showed similar anteroposterior and superoinferior translation as well as compound motion during external rotation at all tested abduction angles. During internal rotation, the elliptical design resulted in significantly more anteroposterior translation and compound motion at all abduction angles when compared to the spherical design (P < 0.05).ConclusionIn the setting of total shoulder arthroplasty, the elliptical head design demonstrated greater glenohumeral translation and micro-motion at the glenoid component during axial rotation when compared to the spherical design, potentially increasing the risk for glenoid loosening in the long term.Level of evidenceControlled Laboratory Study

DUNEuro-A software toolbox for forward modeling in bioelectromagnetism.

Accurate and efficient source analysis in electro- and magnetoencephalography using sophisticated realistic head geometries requires advanced numerical approaches. This paper presents DUNEuro, a free and open-source C++ software toolbox for the numerical computation of forward solutions in bioelectromagnetism. Building upon the DUNE framework, it provides implementations of modern fitted and unfitted finite element methods to efficiently solve the forward problems of electro- and magnetoencephalography. The user can choose between a variety of different source models that are implemented. The software’s aim is to provide interfaces that are extendable and easy-to-use. In order to enable a closer integration into existing analysis pipelines, interfaces to Python and MATLAB are provided. The practical use is demonstrated by a source analysis example of somatosensory evoked potentials using a realistic six-compartment head model. Detailed installation instructions and example scripts using spherical and realistic head models are appended.

Comparing the electric fields of transcranial electric and magnetic perturbation

Significance. Noninvasive brain stimulation (NIBS) by quasistatic electromagnetic means is presently comprised of two methods: magnetic induction methods (transcranial magnetic perturbation or TMP) and electrical contact methods (transcranial electric perturbation or TEP). Both methods couple to neuronal systems by means of the electric fields they produce. Both methods are necessarily accompanied by a scalp electric field which is of greater magnitude than anywhere within the brain. A scalp electric field of sufficient magnitude may produce deleterious effects including peripheral nerve stimulation and heating which consequently limit the spatial and temporal characteristics of the brain electric field. Presently the electromagnetic NIBS literature has produced an accurate but non-generalized understanding of the differences between the TEP and TMP methods. Objective. The aim of this work is to contribute a generalized understanding of the differences between the two methods which may open doors to novel TEP or TMP methods and translating advances, when possible, between the two methods. Approach. This article employs a three shell spherical conductor head model to calculate general analytical results showing the relationship between the spatial scale of the brain electric fields and: (1) the scalp-to-brain mean-squared electric field ratio for the two methods and (2) TEP-to-TMP scalp mean-squared electric field ratio for similar electric fields at depth. Main results. The most general result given is an asymptotic limit to the TEP-to-TMP ratio of scalp mean-squared electric fields for similar electric fields at depth. Specific example calculations for these ratios are also given for typical TEP electrode and TMP coil configurations. While TMP has favorable mean-squared electric field ratios compared to TEP this advantage comes at an energetic cost which is briefly elucidated in this work.

Radiographic evaluation of humeral head reconstruction with stemmed and stemless spherical implants compared with stemless elliptical head implants.

BackgroundThe purpose of this study was to compare the accuracy of anatomic reconstruction of three different humeral head designs after anatomic total shoulder arthroplasty.MethodsPostoperative radiographs of 117 patients who underwent anatomic total shoulder arthroplasty with three different implant designs (stemmed spherical, stemless spherical, and stemless elliptical) were analyzed for landmarks that represented the prearthritic state and final implant position. We assessed the change in center of rotati7on and humeral head height on the anteroposterior view and the percentage of prosthesis overhang on the axillary lateral view. A modified anatomic reconstruction index, a compound score that rated each of the 3 parameters from 0 to 2, was created to determine the overall accuracy of the reconstruction.ResultsExcellent modified anatomic reconstruction index scores (5 or 6 points) were achieved by 68.1% of the cases in the stemless elliptical group compared with 33.3% of the cases in the stemless spherical group and by 28.3% of the cases in the stemmed spherical group (P = .001).The mean difference in restoration of humeral head height (P < .001) and percentage of prosthesis overhang (P < .001) was superior for the stemless elliptical group compared with the two other spherical head groups. There was no difference between groups for the shift in center of rotation (P = .060).ConclusionsIn this radiographic investigation comparing three different humeral head designs with respect to anatomic restoration parameters, the stemless elliptical implant more closely restored the geometry of the prearthritic humeral head as assessed by humeral head height, prosthesis overhang, and a compound reconstruction score.

Effect of skull thickness and conductivity on current propagation for noninvasively injected currents

Objective. When currents are injected into the scalp, e.g. during transcranial current stimulation, the resulting currents generated in the brain are substantially affected by the changes in conductivity and geometry of intermediate tissue. In this work, we introduce the concept of ‘skull-transparent’ currents, for which the changing conductivity does not significantly alter the field while propagating through the head. Approach. We establish transfer functions relating scalp currents to head potentials in accepted simplified models of the head, and find approximations for which skull-transparency holds. The current fields resulting from specified current patterns are calculated in multiple head models, including MRI heads and compared with homogeneous heads to characterize the transparency. Experimental validation is performed by measuring the current field in head phantoms. Main results. The main theoretical result is derived from observing that at high spatial frequencies, in the transfer function relating currents injected into the scalp to potential generated inside the head, the conductivity terms form a multiplicative factor and do not otherwise influence the transfer function. This observation is utilized to design injected current waveforms that maintain nearly identical focusing patterns independently of the changes in skull conductivity and thickness for a wide range of conductivity and thickness values in an idealized spherical head model as well as in a realistic MRI-based head model. Experimental measurements of the current field in an agar-based head phantom confirm the transparency of these patterns. Significance. Our results suggest the possibility that well-chosen patterns of current injection result in precise focusing inside the brain even without a priori knowledge of exact conductivities of intermediate layers.

Control of Uniflagellar Soft Robots at Low Reynolds Number Using Buckling Instability

Abstract In this paper, we analyze the inverse dynamics and control of a bacteria-inspired uniflagellar robot in a fluid medium at low Reynolds number. Inspired by the mechanism behind the locomotion of flagellated bacteria, we consider a robot comprising a flagellum—a flexible helical filament—connected to a spherical head. The flagellum rotates about the head at a controlled angular velocity and generates a propulsive force that moves the robot forward. When the angular velocity exceeds a threshold value, the hydrodynamic force exerted by the fluid can cause the soft flagellum to buckle, characterized by a dramatic change in its shape. In this computational study, a fluid–structure interaction model that combines Discrete Elastic Rods algorithm with Lighthill's Slender Body Theory is employed to simulate the locomotion and deformation of the robot. We demonstrate that the robot can follow a prescribed path in three-dimensional space by exploiting buckling of the flagellum. The control scheme involves only a single (binary) scalar input—the angular velocity of the flagellum. By triggering the buckling instability at the right moment, the robot can follow the path in three-dimensional space. We also show that the complexity of the dynamics of the helical filament can be captured using a deep neural network, from which we identify the input–output functional relationship between the control input and the trajectory of the robot. Furthermore, our study underscores the potential role of buckling in the locomotion of natural bacteria.

Comparison of the roughness of concave cylindrical surfaces machined with spherical milling cutters and toroidal milling cutters

The paper aims to process the concave cylindrical surfaces. This proposes a comparison between the processing of concave cylindrical surfaces with toroidal milling and the processing of concave cylindrical surfaces with spherical milling. The variable process parameters are the cutting speed, the feed per tooth and the inclination angle between the tool axis and the normal to surface. After processing, the surface with the best roughness is tracked according to the regimes and the tool used. A number of 27 concave cylindrical surfaces machined with toroidal milling cutter and 27 concave cylindrical surfaces machined with spherical head milling are machined. The aim is to measure the arithmetic roughness Ra and the total roughness Rt, these being measured parallel and perpendicular to the direction of advance. In order to confirm the correctness of the measured values, microscopic images with the best surfaces will be captured.

A Qualitative Analysis of the Diameter of Long Positive Jet Streamer above Thundercloud in Uniform Atmosphere

A qualitative analysis of the diameter of the spherical head of a long positive Jet streamer above thundercloud is presented in this paper under uniform atmospheric condition for streamers of less than 7 km length. In this study, an attempt is made to replicate laboratory-based point electrode discharge model for jet streamers originating above the thunderclouds. In laboratory conditions, it is not possible to produce huge electrode potentials which could be the reason that the streamers generated under the controlled lab environment have diameter of the order of only a few centimeter and length of a few millimeter. On the other hand, the thunderclouds carry huge electrical charges, for example 50 C, which can produce huge electrical potentials of the order of several hundred MeV. Such huge potential can act as the potential of a point electrode which may be capable of producing very large and thicker streamers above the thunderclouds. So, a leader mechanism of streamer initiation is assumed in calculations as the tip of conducting leader channel can act as point electrode carrying huge cloud potential to generate large streamers. It is found in this study that as the streamer moves larger distance away from the electrode (leader tip), the diameter of the streamer head decreases. Higher the potential of the electrode (leader tip), thicker is the streamer and more slowly the diameter decreases. Also, it is also found in our calculations that for higher electrode (leader tip) potential lower is the altitude of initiation of streamers.

Influence of unfused cranial bones on magnetoencephalography signals in human infants

ObjectiveTo clarify the effects of unfused cranial bones on magnetoencephalography (MEG) signals during early development. MethodsIn a simulation study, we compared the MEG signals over a spherical head model with a circular hole mimicking the anterior fontanel to those over the same head model without the fontanel for different head and fontanel sizes with varying skull thickness and conductivity. ResultsThe fontanel had small effects according to three indices. The sum of differences in signal over a sensor array due to a fontanel, for example, was < 6% of the sum without the fontanel. However, the fontanel effects were extensive for dipole sources deep in the brain or outside the fontanel for larger fontanels. The effects were comparable in magnitude for tangential and radial sources. Skull thickness significantly increased the effect, while skull conductivity had minor effects. ConclusionMEG signal is weakly affected by a fontanel. However, the effects can be extensive and significant for radial sources, thicker skull and large fontanels. The fontanel effects can be intuitively explained by the concept of secondary sources at the fontanel wall. SignificanceThe minor influence of unfused cranial bones simplifies MEG analysis, but it should be considered for quantitative analysis.

A novel method for calibrating head models to account for variability in conductivity and its evaluation in a sphere model

The accuracy in electroencephalography (EEG) and combined EEG and magnetoencephalography (MEG) source reconstructions as well as in optimized transcranial electric stimulation (TES) depends on the conductive properties assigned to the head model, and most importantly on individual skull conductivity. In this study, we present an automatic pipeline to calibrate head models with respect to skull conductivity based on the reconstruction of the P20/N20 response using somatosensory evoked potentials and fields. In order to validate in a well-controlled setup without interplay with numerical errors, we evaluate the accuracy of this algorithm in a 4-layer spherical head model using realistic noise levels as well as dipole sources at different eccentricities with strengths and orientations related to somatosensory experiments. Our results show that the reference skull conductivity can be reliably reconstructed for sources resembling the generator of the P20/N20 response. In case of erroneous assumptions on scalp conductivity, the resulting skull conductivity parameter counterbalances this effect, so that EEG source reconstructions using the fitted skull conductivity parameter result in lower errors than when using the standard value. We propose an automatized procedure to calibrate head models which only relies on non-invasive modalities that are available in a standard MEG laboratory, measures under in vivo conditions and in the low frequency range of interest. Calibrated head modeling can improve EEG and combined EEG/MEG source analysis as well as optimized TES.

Retention strength of ball-attachment titanium post for removable partial denture or overdenture

Aim: To evaluate the retention of an endodontic titanium postwith a spherical head for removable partial denture or overdentureattachment according to surface treatment type. Methods: Sixtyhealthy single-rooted teeth, sectioned at the enamel/cementumjunction, were treated endodontically and steadily fixed in theembedding acrylic resin. The titanium posts were subdivided intofour groups: control, no surface treatment (Ctrl); posts with macroretentivegrooves (MR); air abrasion of the post surface (AB); andposts with macro-retentive grooves and air abrasion of the postsurface (MR+AB). The posts were luted in the root canal usingself-adhesive dual resin cement. Pull-out testing was performedusing a universal testing machine until complete detachment wasachieved. After pull-out testing, the metallic posts were examinedunder an optical microscope and the failures were classifiedbased on the cement distribution pattern on the extracted posts:0, no cement left on the post (cement/post failure); 1, postsurface partially covered by adhered cement (post/cement anddentin/cement mixed failure); 2, post surface completely coveredby cement (dentin/cement failure). The retention data wereanalyzed by one-way ANOVA, Bonferroni–Dunn test (p&lt;0.05)and Weibull analysis. Results: AB showed the highest retentionvalue (485.37±68.36), followed by MR+AB (355.80±118.47), MR(224.63±42.54) and Ctrl (113.12 ± 51.32). AB and MR showedthe highest Weibull moduli. Conclusions: The data indicatedthat air abrasion alone could significantly increase the retentionof titanium posts/attachments for use with overdentures orremovable partial denture.

Individual head models for estimating the TMS-induced electric field in rat brain

In transcranial magnetic stimulation (TMS), the initial cortical activation due to stimulation is determined by the state of the brain and the magnitude, waveform, and direction of the induced electric field (E-field) in the cortex. The E-field distribution depends on the conductivity geometry of the head. The effects of deviations from a spherically symmetric conductivity profile have been studied in detail in humans. In small mammals, such as rats, these effects are more pronounced due to their less spherical head, proportionally much thicker neck region, and overall much smaller size compared to the TMS coils. In this study, we describe a simple method for building individual realistically shaped head models for rats from high-resolution X-ray tomography images. We computed the TMS-induced E-field with the boundary element method and assessed the effect of head-model simplifications on the estimated E-field. The deviations from spherical symmetry have large, non-trivial effects on the E-field distribution: for some coil orientations, the strongest stimulation is in the brainstem even when the coil is over the motor cortex. With modelling prior to an experiment, such problematic coil orientations can be avoided for more accurate targeting.

Mechanical and thermal stress evaluation of PEEK prefabricated post with different head design in endodontically treated tooth: 3D-finite element analysis.

An endodontic post is required to retain and support the core restoration in case of insufficient remaining coronal dentin after root canal therapy. This study analyzed the biomechanical and thermal behavior of PEEK prefabricated post after choosing the head design that produces the least amount of stress on the core and remaining tooth structure. These results were compared with the most common commercially available prefabricated post, which is titanium and glass fiber post. Thus a CBCT scanning of a maxillary central incisor with its supporting structure was used to construct a 3D solid model of an endodontically treated teeth for finite element analysis (FEA). The restored tooth with the spherical head design of PEEK prefabricated post yielded a more benign stress distribution and repairable failure mode on the crown, luting cement, core, and dentin under both mechanical and thermal loads, followed by glass fiber post and titanium post respectively.

Rotational range of motion of elliptical and spherical heads in shoulder arthroplasty: a dynamic biomechanical evaluation

IntroductionElliptical shape humeral head prostheses have been proposed to reflect a more anatomic shoulder replacement. Its effect on the rotational range of motion (ROM) compared to a standard spherical head is still not understood. The purpose was to investigate if there would be a difference in rotational ROM when comparing elliptical and spherical prosthetic heads in a dynamic shoulder model. The authors hypothesized that the use of elliptical heads would result in significantly more rotational ROM compared to the spherical head design.Materials and methodsSix fresh-frozen, cadaveric shoulders were evaluated using a dynamic shoulder model. After being tested in the native condition, each specimen underwent 6 conditions in the hemiarthroplasty state: (1) matched-fit spherical head, (2) oversized spherical head, (3) undersized spherical head, (4) matched-fit elliptical head, (5) oversized elliptical head, and (6) undersized elliptical head. Following conversion to total shoulder arthroplasty (TSA), the 6 prior conditions were rerun. Each condition was tested at 0°, 30° and 60° of glenohumeral abduction. Rotational ROM was quantified using 3-dimensional tracking, while dynamically applying alternating forces for internal and external rotation via the rotator cuff tendons.ResultsElliptical and spherical prosthetic heads showed no significant difference in the degree of the total, internal, and external rotational ROM for both the hemiarthroplasty and TSA state. Conversion from hemiarthroplasty to TSA resulted in less degree of total rotational ROM for both head designs in all abduction positions, without reaching statistical significance. There was a significant decrease in total, internal, and external rotational ROM for both elliptical and spherical heads in every replacement condition, when comparing 0° to 30° and 60° of abduction (P < 0.05, respectively).ConclusionIn a dynamic shoulder model, elliptical and spherical prosthetic head designs showed no significant difference in the degree of the total, internal, and external rotational ROM in both the hemiarthroplasty and TSA state.Level of evidenceControlled laboratory study

Perceptual Evaluation of Mitigation Approaches of Impairments due to Spatial Undersampling in Binaural Rendering of Spherical Microphone Array Data

Spherical microphone arrays (SMAs) are widely used to capture spatial sound fields that can then be rendered in various ways as a virtual acoustic environment (VAE) including headphone-based binaural synthesis. Several practical limitations have a significant impact on the fidelity of the rendered VAE. The finite number of microphones of SMAs leads to spatial undersampling of the captured sound field, which, on the one hand, induces spatial aliasing artifacts and, on the other hand, limits the order of the spherical harmonics (SH) representation. Several approaches have been presented in the literature that aim to mitigate the perceptual impairments due to these limitations. In this article, we present a listening experiment evaluating the perceptual improvements of binaural rendering of undersampled SMA data that can be achieved using state-of-the-art mitigation approaches. In particular, we examined the Magnitude Least-Squares algorithm, the Bandwidth Extraction Algorithm for Microphone Arrays, Spherical Head Filters, SH Tapering, and a newly proposed equalization filter. In the experiment, subjects rated the perceived differences between a dummy head and the corresponding SMA auralization. We found that most mitigation approaches lead to significant perceptual improvements, even though audible differences to the reference remain.

Role of containment in late onset and early healed perthes-functional outcome

Role of surgical containment in late onset and healed Perthes is still controversial and ill defined. Untreated and partially treated Perthes disease can progress to osteoarthritis by the fourth decade. The main complication is femoral head deformation. Two important factors contributing to complication: 1. Extruded femoral head2. Deformed head leads to early onset of osteoarthritisThis study evaluates the clinical and radiological outcome of varus derotation osteotomy (VDRO) in late onset and early healed Perthes with extruded femoral head with remaining growth potential.Materials and Methods: 30 children (19 males and 11 females) falling in the group of 10-16 years, belonging to modified Elizabethtown classification Stage 4–healed stage / Waldenstrom’s stage 4- residual stage, radiologically – reossified, extruded, deformed femoral head are treated with open wedge VDRO, between 2009 and 2017 were included in this study. 21(70%) are between 10-14yrs, rest are 14 – 16yrs, mean age of osteotomy is 12.37yrs. All patients had limitation of abduction and internal rotation. 14 patients (46.67%) had pain at the hip and 26 patients (86.7%) had limp. Mean time between diagnosis and corrective surgery was 3 weeks.Results: The evaluation was done using caput index (CI) and epiphyseal quotient (EQ) radiologically, range of motion and Harris Hip Score for clinical outcome.Our minimum follow up was 3yrs and maximum follow up of 10years. We studied Radiological and clinical parameters on 3rd year follow up. All measurement was done on pre-op, post op x-rays at 3rd year follow up and also compared with the contralateral hip. We noted improvement in the clinical outcome and radiologically femoral head attained more spherical contour after containment. In our studies 21 children (70%) had good result with Spherical head and fully contained by acetabulum, 6 children (21%) had fair result with congruent head and acetabulum covering>4/5th of femoral head. Rest 3 children had poor result with clinically symptomatic and extruded deformed head. There was a significant change (P = 0.000) in CI among all the patients after surgery. The final EQ after 3 years of VDRO was 0.685 and was significant (P = 0.0000).Conclusion: In Healed perthes with extruded and deformed femoral head, containing with VDRO helps to achieve a spherical femoral head, thereby delaying the onset of osteoarthritis. Mould for a spherical femoral head is the acetabulum. Containg the head resumes its growth until achieving skeletal maturity. The remaining growth potential is utilized to mould the head into sphericity.

A bloom of the green worm Phyllodoce tuberculosa Kudenov, 1975 in a beach of the Southern Gulf of California, Mexico (Annelida, Errantia, Phyllodocidae)

ABSTRACT The massive presence of the green worm Phyllodoce tuberculosa Kudenov, 1975 on a beach of the southern Gulf of California (Mexico) is reported. It was found reaching densities of 48 ind/m2 during low tides, 4 days before the full moon and during the full moon of March 2020. The population comprised mainly gravid females, in a sex ratio of 1:100 (1 male per 100 females). Mature oocytes measure 110–120 μm in diameter. Mature spermatozoa have a nearly spherical head, with an elliptical nucleus, a cap-like acrosome and a long flagellum (ect-aquasperm type). This is the first finding of P. tuberculosa since its description in 1975.

Validation of SPH-FE Numerical Modeling of the Interaction between a High-Speed Water Jet and a PMMA Target by CEL Model and Experimental Study

Abstract In this paper, we present a numerical simulation of a round impacting jet using coupled Smoothed Particle Hydrodynamics (SPH) and Finite Element (FE) methods. Numerical results are compared with the results of another simulation carried out by the CEL (Coupled Eulerian-Lagrangian) method. A water jet with a spherical head was used at an initial speed of 570 m/s to impact a flat plate made of Polymethyl-Methacrylate (PMMA). To model the entire process, the SPH method was used to model the water jet and the FE method for the PMMA structure. The distribution of the pressure on the impact surface and the resulting deformation of the structure were discussed. A Numerical model was developed using ABAQUS/Explicit version 6.14. Results of the coupled SPH-FE simulation were further validated. It is demonstrated that the CEL method presents smoother curves compared to the SPH method. These comparisons serve not only to validate the numerical simulation but also to give guidance in formulating the SPH-FEM numerical model.

Research on the proportional-integral-derivative synchronous control method of the marine spherical isolation plug in the rotation process

The emergency pipeline repair technology is crucial to the maintenance and safety of pipelines under the emergency condition. In the offshore industry, the marine spherical isolation plug, a novel active plug device, is a significant emergency repair equipment of the hot tapping and line stop operation. In this article, the structure scheme and operation process of the marine spherical isolation plug are designed. A mathematic model is extracted from the proposed structure, and then the coordinates of the center of the spherical plug head is calculated using the D–H method. The displacements of the inserting hydraulic cylinder and the rotation hydraulic cylinder are investigated to provide the remote control data for the upper computer controller during the torsion process of the plug head. Moreover, a proportional-integral-derivative (PID) synchronous control method simulated by MATLAB is presented to reduce the rotation error of the plug head. To discuss the control strategy, a numerical model using ADAMS software is built. The results show that the error of the PID synchronous control method is more precise than that of the signal step-by-step control method; the number of steps of 90 is recommended in the actual operation. This article will provide theoretical guidance for the optimization design of the marine spherical isolation plug system.

EGSnrc/BEAMnrc-Based Monte Carlo Simulation of the Gamma Knife 4C versus MCNP Code in Homogeneous Media

Purpose: Gamma Knife is applied as a superseded tool for inaccessible lesions surgery delivering a single high dose to a well-defined target through 201 small beams. Monte Carlo simulations can be an appropriate supplementary tool to determine dosimetric parameters in small fields due to the related dosimetry hardships. Materials and Methods: EGSnrc/BEAMnrc Monte Carlo code was implemented to model Gamma Knife 4C. Single channel geometry comprising stationary and helmet collimators was simulated. A point source was considered as a cylindrical Cobalt source based on the simplified source channel mode. All of the 201 source channels were arranged in spherical coordinate by EGSnrc/DOSXYZnrc code to calculate dose profiles. The simulated profiles at the isocentre point in a spherical head phantom 160 mm in diameter along three axes for 4, 8, 14, and 18 mm field sizes were compared to those obtained by another work using MCNP code. Results: Based on the results, the BEAMnrc and MCNP dose profiles matched well apart from the 18 mm profiles along X and Y directions with the average gamma index of 1.36 and 1.18, respectively. BEAMnrc profiles for 14 and 18 mm field sizes along X and Y axes were entirely flat in plateau region, whereas MCNP profiles represented variations as well as round shape. Besides, considering the identical results, radioactive source can be modeled by a point source instead of cylindrical one. Conclusion: Thus, the EGSnrc/BEAMnrc code is recommended to simulate Gamma Knife machine as it is regarded as the most accurate computer program to simulate photon and electron interactions.