Displaying publications 1 - 20 of 37 in total

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  1. Three-dimensional anatomical accuracy of cranial models created by rapid prototyping techniques validated using a neuronavigation station
    Waran V, Devaraj P, Hari Chandran T, Muthusamy KA, Rathinam AK, Balakrishnan YK, et al.
    J Clin Neurosci, 2012 Apr;19(4):574-7.
    PMID: 22305869 DOI: 10.1016/j.jocn.2011.07.031
    In neurosurgery and ear, nose and throat surgery the application of computerised navigation systems for guiding operations has been expanding rapidly. However, suitable models to train surgeons in using navigation systems are not yet available. We have developed a technique using an industrial, rapid prototyping process from which accurate spatial models of the cranium, its contents and pathology can be reproduced for teaching. We were able to register, validate and navigate using these models with common available navigation systems such as the Medtronic StealthStation S7®.
    Matched MeSH terms: Models, Anatomic*
  2. New head models extracted from thermal infrared (IR) images for dosimetry computations
    Gasmelseed A
    Comput Methods Biomech Biomed Engin, 2011 Jul;14(7):665-71.
    PMID: 21480080 DOI: 10.1080/10255842.2011.563738
    In electromagnetic dosimetry, anatomical human models are commonly obtained by segmentation of magnetic resonance imaging or computed tomography scans. In this paper, a human head model extracted from thermal infrared images is examined in terms of its applicability to specific absorption rate (SAR) calculations. Since thermal scans are two-dimensional (2D) representation of surface temperature, this allows researchers to overcome the extensive computational demand associated with 3D simulation. The numerical calculations are performed using the finite-difference time-domain method with mesh sizes of 2 mm at 900 MHz plane wave irradiation. The power density of the incident plane wave is assumed to be 10 W/m(2). Computations were compared with a realistic anatomical head model. The results show that although there were marked differences in the local SAR distribution in the various tissues in the two models, the 1 g peak SAR values are approximately similar in the two models.
    Matched MeSH terms: Models, Anatomic*
  3. Experimental investigation of the flow of bile in patient specific cystic duct models
    Al-Atabi M, Chin SB, Luo XY
    J Biomech Eng, 2010 Apr;132(4):041003.
    PMID: 20387966 DOI: 10.1115/1.4001043
    Three-dimensional scaled-up transparent models of three human cystic ducts were prepared on the basis of anatomical specimens. The measurement of pressure drop across the cystic duct models and visualization of the flow structures within these ducts were performed at conditions replicating the physiological state. The flow visualization study confirmed the laminar nature of the flow of bile inside the cystic duct and values of pressure drop coefficient (Cp) decreased as the Reynolds number (Re) increased. The three tested models showed comparable behavior for the curve of Reynolds number versus the pressure drop coefficient. The results show that the tested cystic ducts have both increased pressure drop and complicated flow structures when compared with straight conduits. High resistance in a cystic duct may indicate that the gallbladder has to exert large force in expelling bile to the cystic duct. For patients with diseased gallbladder, and even in healthy persons, gallbladder is known to stiffen with age and it may lose its compliance or flexibility. A high resistance cystic duct coupled with a stiffened gallbladder may result in prolonged stasis of bile in the gallbladder, which is assumed to encourage the formation of gallstones.
    Matched MeSH terms: Models, Anatomic*
  4. Finite element analysis of idealised unit cell cancellous structure based on morphological indices of cancellous bone
    Kadir MR, Syahrom A, Ochsner A
    Med Biol Eng Comput, 2010 May;48(5):497-505.
    PMID: 20224954 DOI: 10.1007/s11517-010-0593-2
    Human bones can be categorised into one of two types--the compact cortical and the porous cancellous. Whilst the cortical is a solid structure macroscopically, the structure of cancellous bone is highly complex with plate-like and strut-like structures of various sizes and shapes depending on the anatomical site. Reconstructing the actual structure of cancellous bone for defect filling is highly unfeasible. However, the complex structure can be simplified into an idealised structure with similar properties. In this study, two idealised architectures were developed based on morphological indices of cancellous bone: the tetrakaidecahedral and the prismatic. The two architectures were further subdivided into two types of microstructure, the first consists of struts only and the second consists of a combination of plates and struts. The microstructures were transformed into finite element models and displacement boundary condition was applied to all four idealised cancellous models with periodic boundary conditions. Eight unit cells extracted from the actual cancellous bone obtained from micro-computed tomography were also analysed with the same boundary conditions. Young's modulus values were calculated and comparison was made between the idealised and real cancellous structures. Results showed that all models with a combination of plates and struts have higher rigidity compared to the one with struts only. Values of Young's modulus from eight unit cells of cancellous bone varied from 42 to 479 MPa with an average of 234 MPa. The prismatic architecture with plates and rods closely resemble the average stiffness of a unit cell of cancellous bone.
    Matched MeSH terms: Models, Anatomic*
  5. The utilization of cranial models created using rapid prototyping techniques in the development of models for navigation training
    Waran V, Pancharatnam D, Thambinayagam HC, Raman R, Rathinam AK, Balakrishnan YK, et al.
    J Neurol Surg A Cent Eur Neurosurg, 2014 Jan;75(1):12-5.
    PMID: 23315670 DOI: 10.1055/s-0032-1330960
    Navigation in neurosurgery has expanded rapidly; however, suitable models to train end users to use the myriad software and hardware that come with these systems are lacking. Utilizing three-dimensional (3D) industrial rapid prototyping processes, we have been able to create models using actual computed tomography (CT) data from patients with pathology and use these models to simulate a variety of commonly performed neurosurgical procedures with navigation systems.
    Matched MeSH terms: Models, Anatomic*
  6. Determining the Accuracy of the Mandibular Canal Region in 3D Biomodels Fabricated from CBCT Scanned Data: A Cadaveric Study
    Abd Fattah SYAS, Hariri F, Nambiar P, Abu Bakar Z, Abdul Rahman ZA
    Curr Med Imaging Rev, 2019;15(7):645-653.
    PMID: 32008512 DOI: 10.2174/1573405614666181012144745
    OBJECTIVE: To validate the accuracy of the mandibular canal region in 3D biomodel produced by using data obtained from Cone-Beam Computed Tomography (CBCT) of cadaveric mandibles.

    METHODS: Six hemi-mandible samples were scanned using the i-CAT CBCT system. The scanned data was transferred to the OsiriX software for measurement protocol and subsequently into Mimics software to fabricate customized cutting jigs and 3D biomodels based on rapid prototyping technology. The hemi-mandibles were segmented into 5 dentoalveolar blocks using the customized jigs. Digital calliper was used to measure six distances surrounding the mandibular canal on each section. The same distances were measured on the corresponding cross-sectional OsiriX images and the 3D biomodels of each dentoalveolar block.

    RESULTS: Statistically no significant difference was found when measurements from OsiriX images and 3D biomodels were compared to the "gold standard" -direct digital calliper measurement of the cadaveric dentoalveolar blocks. Moreover, the mean value difference of the various measurements between the different study components was also minimal.

    CONCLUSION: Various distances surrounding the mandibular canal from 3D biomodels produced from the CBCT scanned data was similar to that of direct digital calliper measurements of the cadaveric specimens.

    Matched MeSH terms: Models, Anatomic
  7. A preliminary study of using active vision guided robotic arm for bone drilling in a developing country
    Abdullah MZ, Awang MS, Tan YC, Abdullah JM
    J Neurol Surg A Cent Eur Neurosurg, 2014 Mar;75(2):155-7.
    PMID: 23636911 DOI: 10.1055/s-0032-1330954
    The study assesses the capability and accuracy of a robotic arm to perform burr holes.
    Matched MeSH terms: Models, Anatomic
  8. A low-cost phantom for simple routine testing of single photon emission computed tomography (SPECT) cameras
    Ng AH, Ng KH, Dharmendra H, Perkins AC
    Appl Radiat Isot, 2009 Oct;67(10):1864-8.
    PMID: 19049851 DOI: 10.1016/j.apradiso.2008.10.010
    A simple sphere test phantom has been developed for routine performance testing of SPECT systems in situations where expensive commercial phantoms may not be available. The phantom was based on a design with six universal syringe hubs set in the frame to support a circular array of six glass blown spheres of different sizes. The frame was then placed into a water-filled CT abdomen phantom and scanned with a triple head camera system (Philips IRIX, USA). Comparison was made with a commercially available phantom (Deluxe Jaszczak phantom). Whereas the commercial phantom demonstrates cold spot resolution, an important advantage of the sphere test phantom was that hot spot resolution could be easily measured using almost half (370MBq) of the activity recommended for use in the commercial phantom. Results showed that the contrast increased non-linearly with sphere volume and radionuclide concentration. The phantom was found to be suitable as an inexpensive option for daily performance tests.
    Matched MeSH terms: Models, Anatomic
  9. Monte Carlo-based patient internal dosimetry in fluoroscopy-guided interventional procedures: A review
    Fum WKS, Wong JHD, Tan LK
    Phys Med, 2021 Apr;84:228-240.
    PMID: 33849785 DOI: 10.1016/j.ejmp.2021.03.004
    PURPOSE: This systematic review aims to understand the dose estimation approaches and their major challenges. Specifically, we focused on state-of-the-art Monte Carlo (MC) methods in fluoroscopy-guided interventional procedures.

    METHODS: All relevant studies were identified through keyword searches in electronic databases from inception until September 2020. The searched publications were reviewed, categorised and analysed based on their respective methodology.

    RESULTS: Hundred and one publications were identified which utilised existing MC-based applications/programs or customised MC simulations. Two outstanding challenges were identified that contribute to uncertainties in the virtual simulation reconstruction. The first challenge involves the use of anatomical models to represent individuals. Currently, phantom libraries best balance the needs of clinical practicality with those of specificity. However, mismatches of anatomical variations including body size and organ shape can create significant discrepancies in dose estimations. The second challenge is that the exact positioning of the patient relative to the beam is generally unknown. Most dose prediction models assume the patient is located centrally on the examination couch, which can lead to significant errors.

    CONCLUSION: The continuing rise of computing power suggests a near future where MC methods become practical for routine clinical dosimetry. Dynamic, deformable phantoms help to improve patient specificity, but at present are only limited to adjustment of gross body volume. Dynamic internal organ displacement or reshaping is likely the next logical frontier. Image-based alignment is probably the most promising solution to enable this, but it must be automated to be clinically practical.

    Matched MeSH terms: Models, Anatomic
  10. Evaluation of workshop for training house-officers and medical officers on medical emergencies using simulation for workplace preparedness
    Thiruselvi Subramaniam, Ann Jee Tan
    International e-Journal of Science, Medicine & Education, 2017;11(1):33-38.
    MyJurnal
    Background: House-officers and medical officers are at
    the forefront during medical emergencies in the ward
    and casualty which impose cognitive, communication,
    social and system challenges and yet, training in this
    area is commonly lacking. A workshop was conducted
    using simulation to provide training on some acute
    medical emergencies like cord prolapse, post- partum
    haemorrhage with collapse, poly-trauma and acute
    exacerbation of asthma.

    Objective: To determine the effectiveness of simulation
    in developing competency in managing selected clinical
    emergencies.

    Methodology: There were 22 participants consisting
    of house-officers, junior medical officers and nursing
    clinical instructors. Only doctors were included in
    the study. Four medical emergencies were chosen viz.:
    Cord prolapse; post- partum haemorrhage with collapse;
    poly-trauma and acute exacerbation of asthma. The
    simulated sessions were conducted using high fidelity
    manikins and simulated patients. Simulated patients
    were trained and moulage was applied accordingly. The
    skills stations were on airway equipment and techniques
    of application, latest cardiac life support algorithm and
    hands on chest compression using manikins.

    Results: A 5 point Likert scale used to rate the
    sessions. The skills station had 65% (n=13) rating as
    excellent and 35% (n=7) good. The skills simulation
    was rated excellent by 75% (n=15) and good by 25%
    (n=5) of participants. Verbal feedback was that it was
    very refreshing, informative, and helpful in terms of
    improving their skills.

    Conclusion: The simulated skills training for the junior
    doctors was very well received and maybe beneficial for
    work preparedness and in the long run address patient
    safety.
    Matched MeSH terms: Models, Anatomic
  11. Fulltext Comparison of various functionally graded femoral prostheses by finite element analysis
    Oshkour AA, Talebi H, Shirazi SF, Bayat M, Yau YH, Tarlochan F, et al.
    ScientificWorldJournal, 2014;2014:807621.
    PMID: 25302331 DOI: 10.1155/2014/807621
    This study is focused on finite element analysis of a model comprising femur into which a femoral component of a total hip replacement was implanted. The considered prosthesis is fabricated from a functionally graded material (FGM) comprising a layer of a titanium alloy bonded to a layer of hydroxyapatite. The elastic modulus of the FGM was adjusted in the radial, longitudinal, and longitudinal-radial directions by altering the volume fraction gradient exponent. Four cases were studied, involving two different methods of anchoring the prosthesis to the spongy bone and two cases of applied loading. The results revealed that the FG prostheses provoked more SED to the bone. The FG prostheses carried less stress, while more stress was induced to the bone and cement. Meanwhile, less shear interface stress was stimulated to the prosthesis-bone interface in the noncemented FG prostheses. The cement-bone interface carried more stress compared to the prosthesis-cement interface. Stair climbing induced more harmful effects to the implanted femur components compared to the normal walking by causing more stress. Therefore, stress shielding, developed stresses, and interface stresses in the THR components could be adjusted through the controlling stiffness of the FG prosthesis by managing volume fraction gradient exponent.
    Matched MeSH terms: Models, Anatomic*
  12. Endoscopic skull base training using 3D printed models with pre-existing pathology
    Narayanan V, Narayanan P, Rajagopalan R, Karuppiah R, Rahman ZA, Wormald PJ, et al.
    Eur Arch Otorhinolaryngol, 2015 Mar;272(3):753-7.
    PMID: 25294050 DOI: 10.1007/s00405-014-3300-3
    Endoscopic base of skull surgery has been growing in acceptance in the recent past due to improvements in visualisation and micro instrumentation as well as the surgical maturing of early endoscopic skull base practitioners. Unfortunately, these demanding procedures have a steep learning curve. A physical simulation that is able to reproduce the complex anatomy of the anterior skull base provides very useful means of learning the necessary skills in a safe and effective environment. This paper aims to assess the ease of learning endoscopic skull base exposure and drilling techniques using an anatomically accurate physical model with a pre-existing pathology (i.e., basilar invagination) created from actual patient data. Five models of a patient with platy-basia and basilar invagination were created from the original MRI and CT imaging data of a patient. The models were used as part of a training workshop for ENT surgeons with varying degrees of experience in endoscopic base of skull surgery, from trainees to experienced consultants. The surgeons were given a list of key steps to achieve in exposing and drilling the skull base using the simulation model. They were then asked to list the level of difficulty of learning these steps using the model. The participants found the models suitable for learning registration, navigation and skull base drilling techniques. All participants also found the deep structures to be accurately represented spatially as confirmed by the navigation system. These models allow structured simulation to be conducted in a workshop environment where surgeons and trainees can practice to perform complex procedures in a controlled fashion under the supervision of experts.
    Matched MeSH terms: Models, Anatomic*
  13. Fulltext Numerical investigation of the effect of stenosis geometry on the coronary diagnostic parameters
    Kamangar S, Kalimuthu G, Badruddin IA, Badarudin A, Ahmed NJ, Khan TM
    ScientificWorldJournal, 2014;2014:354946.
    PMID: 25258722 DOI: 10.1155/2014/354946
    The present study deals with the functional severity of a coronary artery stenosis assessed by the fractional flow reserve (FFR). The effects of different geometrical shapes of lesion on the diagnostic parameters are unknown. In this study, 3D computational simulation of blood flow in three different geometrical shapes of stenosis (triangular, elliptical, and trapezium) is considered in steady and transient conditions for 70% (moderate), 80% (intermediate), and 90% (severe) area stenosis (AS). For a given percentage AS, the variation of diagnostic parameters which are derived from pressure drop across the stenosis was found in three different geometrical shapes of stenosis and it was observed that FFR is higher in triangular shape and lower in trapezium shape. The pressure drop coefficient (CDP) was higher in trapezium shape and lower in triangular model whereas the LFC shows opposite trend. From the clinical perspective, the relationship between percentage AS and FFR is linear and inversely related in all the three models. A cut-off value of 0.75 for FFR was observed at 76.5% AS in trapezium model, 79.5% in elliptical model, and 82.7% AS for the triangular shaped model. The misinterpretation of the functional severity of the stenosis is in the region of 76.5%-82.7 % AS from different shapes of stenosis models.
    Matched MeSH terms: Models, Anatomic*
  14. Utility of multimaterial 3D printers in creating models with pathological entities to enhance the training experience of neurosurgeons
    Waran V, Narayanan V, Karuppiah R, Owen SL, Aziz T
    J. Neurosurg., 2014 Feb;120(2):489-92.
    PMID: 24321044 DOI: 10.3171/2013.11.JNS131066
    The advent of multimaterial 3D printers allows the creation of neurosurgical models of a more realistic nature, mimicking real tissues. The authors used the latest generation of 3D printer to create a model, with an inbuilt pathological entity, of varying consistency and density. Using this model the authors were able to take trainees through the basic steps, from navigation and planning of skin flap to performing initial steps in a craniotomy and simple tumor excision. As the technology advances, models of this nature may be able to supplement the training of neurosurgeons in a simulated operating theater environment, thus improving the training experience.
    Matched MeSH terms: Models, Anatomic*
  15. Model construction by students within an integrated medical curriculum
    Barling PM, Ramasamy P
    Clin Teach, 2011 Mar;8(1):37-42.
    PMID: 21324071 DOI: 10.1111/j.1743-498X.2010.00419.x
    This paper presents our experience of running a special study module (SSM) in the second semester of the first year of our 5-year medical programme, worth 10 per cent of that semester's assessment, in which each student constructs an individually selected model illustrating a specific aspect of the teaching course.
    Matched MeSH terms: Models, Anatomic*
  16. Fulltext Surface Reconstruction from Parallel Curves with Application to Parietal Bone Fracture Reconstruction
    Majeed A, Mt Piah AR, Ridzuan Yahya Z
    PLoS One, 2016;11(3):e0149921.
    PMID: 26967643 DOI: 10.1371/journal.pone.0149921
    Maxillofacial trauma are common, secondary to road traffic accident, sports injury, falls and require sophisticated radiological imaging to precisely diagnose. A direct surgical reconstruction is complex and require clinical expertise. Bio-modelling helps in reconstructing surface model from 2D contours. In this manuscript we have constructed the 3D surface using 2D Computerized Tomography (CT) scan contours. The fracture part of the cranial vault are reconstructed using GC1 rational cubic Ball curve with three free parameters, later the 2D contours are flipped into 3D with equidistant z component. The constructed surface is represented by contours blending interpolant. At the end of this manuscript a case report of parietal bone fracture is also illustrated by employing this method with a Graphical User Interface (GUI) illustration.
    Matched MeSH terms: Models, Anatomic*
  17. Finite element study of functionally graded porous femoral stems incorporating body-centered cubic structure
    Alkhatib SE, Tarlochan F, Mehboob H, Singh R, Kadirgama K, Harun WSBW
    Artif Organs, 2019 Jul;43(7):E152-E164.
    PMID: 30805945 DOI: 10.1111/aor.13444
    The mismatch between stiffness of the femoral dense stem and host bone causes complications to patients, such as aseptic loosening and bone resorption. Three-dimensional finite-element models of homogeneous porous (HGP) and functionally graded porous (FGP) stems incorporating body-centered cubic (BCC) structures are proposed in this article as an alternative to the dense stems. The relationship between the porosity and strut thickness of the BCC structure was developed to construct the finite-element models. Three levels of porosities (20%, 50%, and 80%) were modeled in HGP and FGP stems. The porosity of the stems was decreased distally according to the sigmoid function (n = 0.1, n = 1 and n = 10) with 3 grading exponents. The results showed that FGP stems transferred 120%-170% higher stresses to the femur (Gruen zone 7) as compared to the solid stem. Conversely, the stresses in HGP and FGP stems were 12%-34% lower than the dense stem. The highest micromotions (105-147 µm) were observed for stems of 80% overall porosity, and the lowest (42-46 µm) was for stems of 20% overall porosity. Finally, FGP stems with a grading exponent of n = 10 resulted in an 11%-28% reduction in micromotions.
    Matched MeSH terms: Models, Anatomic
  18. Fulltext Characterization of the Fat Channel for Intra-Body Communication at R-Band Frequencies
    Asan NB, Hassan E, Shah JVSRM, Noreland D, Blokhuis TJ, Wadbro E, et al.
    Sensors (Basel), 2018 Aug 21;18(9).
    PMID: 30134629 DOI: 10.3390/s18092752
    In this paper, we investigate the use of fat tissue as a communication channel between in-body, implanted devices at R-band frequencies (1.7⁻2.6 GHz). The proposed fat channel is based on an anatomical model of the human body. We propose a novel probe that is optimized to efficiently radiate the R-band frequencies into the fat tissue. We use our probe to evaluate the path loss of the fat channel by studying the channel transmission coefficient over the R-band frequencies. We conduct extensive simulation studies and validate our results by experimentation on phantom and ex-vivo porcine tissue, with good agreement between simulations and experiments. We demonstrate a performance comparison between the fat channel and similar waveguide structures. Our characterization of the fat channel reveals propagation path loss of ∼0.7 dB and ∼1.9 dB per cm for phantom and ex-vivo porcine tissue, respectively. These results demonstrate that fat tissue can be used as a communication channel for high data rate intra-body networks.
    Matched MeSH terms: Models, Anatomic
  19. Fulltext Complex pattern of a variant hepatic artery
    Hlaing KP, Othman F
    Singapore Med J, 2012 Sep;53(9):e186-8.
    PMID: 23023911
    Liver transplantation is the only solution for end-stage liver diseases. The common hepatic artery (CHA) arises from the coeliac trunk (CT), and the right (RHA) and left hepatic (LHA) arteries are its terminal branches. An abnormal arterial pattern would influence the surgical outcome. The anterior layer of the lesser omentum of a female cadaver was cleaned to identify the CHA, which was traced backwards for its origin and toward the porta hepatis for its terminal branches. In this case, the replaced RHA originated from the CT and ran posterior to the portal vein and the common bile duct. The replaced LHA arose from the left gastric artery. The CHA originated from the CT and branched out as the middle hepatic and gastroduodenal arteries. The replaced RHA and LHA with alteration in relation to the neighbouring structures is a complex and rare variant. Knowledge of this uncommon arterial anomaly is beneficial for hepatobiliary surgeons.
    Matched MeSH terms: Models, Anatomic
  20. The effects of metamaterial on electromagnetic fields absorption characteristics of human eye tissues
    Gasmelseed A, Yunus J
    Prog Biophys Mol Biol, 2014 Jan;114(1):8-12.
    PMID: 24239501 DOI: 10.1016/j.pbiomolbio.2013.10.004
    The interaction of a dipole antenna with a human eye model in the presence of a metamaterial is investigated in this paper. The finite difference time domain (FDTD) method with convolutional perfectly matched layer (CPML) formulation have been used. A three-dimensional anatomical model of the human eye with resolution of 1.25 mm × 1.25 mm × 1.25 mm was used in this study. The dipole antenna was driven by modulated Gaussian pulse and the numerical study is performed with dipole operating at 900 MHz. The analysis has been done by varying the size and value of electric permittivity of the metamaterial. By normalizing the peak SAR (1 g and 10 g) to 1 W for all examined cases, we observed how the SAR values are not affected by the different permittivity values with the size of the metamaterial kept fixed.
    Matched MeSH terms: Models, Anatomic
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