Biomedical subjects

T M Barker

Publications and source records attributed to T M Barker.

15 recordsLinked to original sources

PubMed2002

Neural networks in cardiac electrophysiological signal classification.

The aim of this work was to develop a method by which intra-cardiac electrograms could be classified. A new algorithm for training this particular network has been established and applied to the task of finding the onset times of intra-cardiac electrograms. The algorithm is based on adding a choice function to the combination function of each neuron. The choice function enables the network to consider delays in each of its synapses. The gradient of error is then calculated with respect to the weights and delays. A synaptic delay-based artificial neural network was implemented using MATLAB and used to detect the onset times of the atrial, His and ventricular electrograms from the His catheter recordings. Results from a subset of a clinical, 12-channel electrophysiology study demonstrated the ability of the network to successfully identify peak potentials and onset times. Errors in detection of onset times were in the range of 1-2 ms. This method, which does not utilise traditional windowing and/or thresholding operations, can be effectively used to detect temporal patterns in a range of electrophysiological and biological signals.

Algorithms↗

PubMed2001

Impact data for the investigation of injuries in inflatable rescue boats (IRBS).

Inflatable Rescue Boats (IRBs) are arguably the most important rescue tools utilised by Australian Surf Lifesavers. The crews in the IRB are continuously battling the fierce element that is the ocean. This force of nature takes its toll on man and machine. Initial impact data for this unique situation has been gathered as part of a biomechanical study investigating the increasing frequency of injuries to surf lifesavers whilst using an IRB. This paper outlines the scope of the research topic and concentrates on the data gathering equipment and an analysis of this unique data set. This initial testing has revealed impact acceleration peaks up to and exceeding 400 m/s2 (40 g) for a period of about 20 ms. These values were a result of an impact with waves of moderate size (approximately 1 m). It was therefore concluded that the impact is of a significant nature and further work should be performed to determine more concise ride characteristics for the IRB. From that it is hoped that methods will be discovered to lessen the impact on the crew with the aim of decreasing the injury rate.

Acceleration↗

PubMed2000

Custom cranioplasty using stereolithography and acrylic.

Numerous methods of cranioplasty have been described. Customization and prefabrication have been reported to reduce operating time and improve cosmesis. An original technique for the manufacture of customized cranioplastic implants has been developed and tested in 30 patients.Thirty patients requiring cranioplasties were selected. Data acquired from computed tomography (CT) were used to manufacture exact plastic replicas (biomodels) of craniotomy defects and master cranioplastic implants using the rapid prototyping technology of stereolithography (SL). The three-dimensional (3D) imaging techniques of mirroring and interpolation were used to extrapolate on existing anatomy to design the master implants. The master implants were hand finished to fit the defect in the corresponding cranial biomodel exactly and were then used to create a cavity mould. The mould was used to cast thermally polymerised custom acrylic implants. The surgeons reported that the customized implants reduced operating time, afforded excellent cosmesis and were cost effective. The patients reported that the opportunity to see the biomodel and implant preoperatively improved their understanding of the procedure. Two complications were noted, one infection and one implant required significant trimming. The simultaneous manufacture of the master implant (male) and biomodel (female) components from SL allowed custom accurate implants to be manufactured. Disadvantages identified were the time required for computer manipulations of the CT data (up to 2 h), difficulty in assessing the accuracy of the computer generated master as a 3D rendering, the potential for SL parts to warp, manufacturing time (minimum 2 days) and the cost of approximately $1300 US per case ($1000 for the SL biomodel and $300 for the acrylic casting).

Humans↗

PubMed1999

Spinal biomodeling.

STUDY DESIGN: A prospective trial of stereolithographic biomodeling in complex spinal surgery. OBJECTIVES: To investigate the use of stereolithographic biomodeling as an aid to complex spinal surgery. SUMMARY OF BACKGROUND DATA: Of the array of imaging methods available to assist the spinal surgeon, no single method provides a complete overview of the anatomy, although three-dimensional imaging has been shown to have advantages. METHODS: Stereolithographic biomodeling is a new technology that allows data from three-dimensional computed tomographic scans to be used to generate exact plastic replicas of anatomic structures. Five patients with complex deformities were selected: two children with congenital deformities, a patient with an osteoblastoma, a patient with basilar invagination caused by osteogenesis imperfecta, and a patient with a failed lumbar fusion. Computed tomographic scanning was performed and stereolithographic biomodels generated. The stereolithographic biomodels were used for patient education, operative planning, and surgical navigation. RESULTS: The surgeons reported that biomodeling was useful in complex spinal surgery and was an effective technology. Stereolithographic biomodels were found to be particularly useful in morphologic assessment, in the planning and rehearsal of surgery, for intraoperative navigation, and for informing patients about surgical procedures. CONCLUSIONS: Stereolithographic biomodeling allows imaging data to be displayed in a physical form. This intuitive medium may improve data display and allows surgical simulation on a proxy of the surgical site. Draw-backs of the technology were a minimum 24 hours' manufacturing time and the cost.

Adult↗

PubMed1999

Effect of metal surface topography on mechanical bonding at simulated total hip stem-cement interfaces.

Bonding and loosening mechanisms between bone cement and joint prostheses have not been well identified. In this study, the effects of simulated hip stem surface topography on the interfacial shear strength were examined. Six different surface topographies were used. They were described by several surface characterization parameters that may directly relate to the interfacial bonding strength: average surface roughness R(a), root mean square slope R(Deltaq), correlation length beta, and fluid retention index R(ri). The shear strengths between Palacos E bone cement and stainless steel rods were measured using an Instron materials testing machine. We found that cement can "flow" into the surface microtopography and establish good contact with the metal surface. The results show that the interfacial strength increases monotonically with the increase of R(Deltaq) instead of with R(a). The relationship between interfacial strength and surface parameters shows that a metal stem with an isotropic surface texture, higher R(Deltaq), and greater R(ri) gives a higher interfacial strength.

Biocompatible Materials↗

PubMed1999

Stereolithographic biomodelling in cranio-maxillofacial surgery: a prospective trial.

Stereolithographic (SL) biomodelling is a new technology that allows three-dimensional (3-D) computed tomography (CT) data to be used to manufacture solid plastic replicas of anatomical structures (biomodels). A prospective trial with the objective of assessing the utility of biomodelling in complex surgery has been performed. Forty-five patients with craniofacial, maxillofacial, skull base cervical spinal pathology were selected. 3-D CT or MR scanning was performed and the data of interest were edited and converted into a form acceptable to the rapid prototyping technology SL. The data were used to guide a laser to selectively polymerize photosensitive resin to manufacture biomodels. The biomodels were used by surgeons for patient education, diagnosis and operative planning. An assessment protocol was used to test the hypothesis that 'biomodels in addition to standard imaging had greater utility in the surgery performed than the standard imaging alone'. Biomodels significantly improved operative planning (images 44.09%, images with biomodel 82.21%, P < .01) and diagnosis (images 65.63%, images with biomodel 95.23%, P < .01). Biomodels were found to improve measurement accuracy significantly (image measurement error 44.14%, biomodel measurement error 7.91%, P < .05). Surgeons estimated that the use of biomodels reduced operating time by a mean of 17.63% and were cost effective at a mean price of $1031 AUS. Patients found the biomodels to be helpful for informed consent (images 63.53%, biomodels 88.54%, P < .001). Biomodelling is an intuitive, user-friendly technology that facilitated diagnosis and operative planning. Biomodels allowed surgeons to rehearse procedures readily and improved communication between colleagues and patients.

Cephalometry↗

PubMed1999

Discriminant analysis of human kinematic data: application to human lumbar spinal motion.

A study was undertaken to determine the applicability of a multivariate discriminant technique in order to analyse human kinematic data, specifically lumbar motion during forward flexion. This method was used in an attempt to allow comparison of time-series data (three joint angles and three linear displacements) between groups of subjects. Results obtained from ten healthy subjects performing simulated abnormal styles of forward flexion indicate the feasibility and potential utility of this method in a clinical environment. Further investigations will be undertaken on clinical subjects to discriminate more effectively between healthy and pathological movements.

Adolescent↗

PubMed1998

Stereolithographic (SL) biomodelling in craniofacial surgery.

BACKGROUND: Stereolithographic (SL) biomodelling allows 3D CT to be used to generate solid plastic replicas of anatomical structures (biomodels). Case reports in the literature suggest that such biomodels may have a use in craniofacial surgery but no large series or assessment of utility has been reported. A prospective trial to assess the utility of biomodelling in craniofacial surgery has been performed. METHODS: Forty patients with complex craniofacial abnormalities were selected and 3D CT scanning performed. The data of interest was used to guide a laser to selectively polymerise photosensitive resin to manufacture SL biomodels. The biomodels were used for patient education, diagnosis and operative planning. An assessment protocol was designed to test the hypothesis that biomodels in addition to standard imaging had greater utility in the surgery performed than the standard imaging alone. RESULTS: Anecdotally surgeons found biomodelling useful in 40 complex craniofacial operations. The formal assessment of the first 10 cases suggested biomodels improved operative planning (image 76%, image with biomodel 97%, P < 0.01) and diagnosis (image 82.5%, image with biomodel 99.25%, P < 0.01). Surgeons estimated that the use of biomodels had reduced operating time by a mean of 16% and were cost effective at a mean price of $1100 AUS. CONCLUSION: Biomodelling was reported as an intuitive, user-friendly technology that facilitated diagnosis, operative planning and communication between colleagues and patients. Limitations of the technology were manufacturing time and cost.

Attitude of Health Personnel↗

PubMed1997

Calculation of multi-segment rigid body joint dynamics using MATLAB.

A computational model of the human upper limb was developed utilizing a matrix calculation software package (MATLAB) and a public domain suite of subroutines [Robotics Toolbox (1)]. An easily configurable model of a rigid body, serially linked manipulator was established, avoiding the need for complex numerical equations to be formulated. A generalized model of the upper limb was used to study throwing action of individual subjects by incorporating body segment parameters and kinematic data. Estimates of joint moments were calculated for multiple time instances. This technique can be utilized and adapted for modelling any arbitrary serially linked manipulator system. Inverse and forward kinematics and kinetics can be calculated, enabling biomechanical simulations to be undertaken.

Biomechanical Phenomena↗

PubMed1997

Design of a Web interface for anatomical images.

Interactive documents for use with the World Wide Web have been developed for viewing multi-dimensional radiographic and visual images of human anatomy, derived from the Visible Human Project. Emphasis has been placed on user-controlled features and selections. The purpose was to develop an interface which was independent of host operating system and browser software which would allow viewing of information by multiple users. The interfaces were implemented using HyperText Markup Language (HTML) forms, C programming language and Perl scripting language. Images were pre-processed using ANALYZE and stored on a Web server in CompuServe GIF format. Viewing options were included in the document design, such as interactive thresholding and two-dimensional slice direction. The interface is an example of what may be achieved using the World Wide Web. Key applications envisaged for such software include education, research and accessing of information through internal databases and simultaneous sharing of images by remote computers by health personnel for diagnostic purposes.

Anatomy, Cross-Sectional↗

PubMed1996

Three-dimensional joint co-ordination strategies of the upper limb during functional activities.

A triaxial flexible electrogoniometer has been developed to measure the three-dimensional angular motion of the shoulder joint during simulated activities of daily living. The motion of the elbow, forearm and wrist were also recorded and angle-angle diagrams were mathematically analysed to provide quantitative parameters regarding the control and co-ordination of the joints of the normal and the arthritic upper limb. Two parameters (slope and movement area quotient) were derived and used in the interpretation of joint motion during different activities.

Activities of Daily Living↗

PubMed1995

Technical note: maxillofacial biomodelling--preliminary result.

A new technique of manufacturing three-dimensional (3D) hard tissue biomodels is described. The models, derived from computed tomography data, were constructed by a computer-controlled manufacturing device known as stereolithography apparatus (SLA). Selected cases of patients with facial deformities were presented to illustrate clinical applications of the SLA biomodelling. Physical demonstration of the bony internal anatomy in these patients promoted better conceptualization of the disease process, allowing optimal input into the management decision, pre-operative planning and choice of surgical technique with a consequent reduction in operating time and potential reduction in peri-operative morbidity. Limitations of the solid modelling technique include cost, a lengthy production time which renders it unsuitable for emergency cases, and radiation exposure of the patient. With wider use and further technological development, these drawbacks will be minimized. The 3D SLA biomodels may in future become an adjunct, not only to maxillofacial surgery, but also to other medical specialties.

Adult↗

PubMed1994

Maxillofacial biomodelling.

The authors report the clinical applications of biomodelling with the stereolithography apparatus, a computer-controlled manufacturing technique that builds anatomically accurate skeletal models from sectional radiological data. Reference to several individual cases demonstrates how pre-operative 3-D modelling can refine the accuracy of diagnostic information, facilitate preoperative planning and surgical technique, and reduce operating time.

Acrylic Resins↗

PubMed1994

Accuracy of stereolithographic models of human anatomy.

A study was undertaken to determine the dimensional accuracy of anatomical replicas derived from X-ray 3D computed tomography (CT) images and produced using the rapid prototyping technique of stereolithography (SLA). A dry bone skull and geometric phantom were scanned, and replicas were produced. Distance measurements were obtained to compare the original objects and the resulting replicas. Repeated measurements between anatomical landmarks were used for comparison of the original skull and replica. Results for the geometric phantom demonstrate a mean difference of +0.47 mm, representing an accuracy of 97.7-99.12%. Measurements of the skull produced a range of absolute differences (maximum +4.62 mm, minimum +0.1 mm, mean +0.85 mm). These results support the use of SLA models of human anatomical structures in such areas as pre-operative planning of complex surgical procedures. For applications where higher accuracy is required, improvements can be expected by utilizing smaller pixel resolution in the CT images. Stereolithographic models can now be confidently employed as accurate, three-dimensional replicas of complex, anatomical structures.

Humans↗

PubMed1993

Integration of 3-D medical imaging and rapid prototyping to create stereolithographic models.

This paper describes current research into the creation of solid models which replicate anatomical structures using rapid prototyping techniques. Stereolithography is particularly efficient in the production of highly-complex structures. This technique was applied to the fabrication of a plastic model of a human skull. A geometric definition of the object was obtained by transferring the three-dimensional medical image volume (x-ray CT) and processing the data on a computer graphics workstation. A 3-D biomedical visualisation software package (ANALYZETM) was used to perform segmentation of structures. A 3-D triangular-mesh representation of the selected structure was calculated and converted to a format suitable for processing and construction using stereolithography (SLA). Improvements in the quality of the anatomical model produced will result from improved data processing techniques. Future work is proposed to investigate the influence of imaging parameters and data processing techniques on the resultant plastic models.

Humans↗