Biomedical subjects

W R Fright

Publications and source records attributed to W R Fright.

14 recordsLinked to original sources

PubMed2004

Use of hand-held laser scanning in the assessment of facial swelling: a preliminary study.

A new generation lightweight, hand-held, laser surface scanner (FastSCAN) was validated and clinically evaluated for the assessment of postoperative facial swelling. The potential sources of error-scanner error, registration error, and repositioning and movement error were established for laser scans of a mannequin head and seven volunteers. For the mannequin head the mean (S.D.) volume of the simulated swelling was 12.5 (0.5) cm3. The measurement error was therefore about 4%, and reflected the error in scanned data and in surface registration. Among the volunteers, repositioning of the head introduced additional errors of up to 7.6 cm3 (mean 1.8 cm3), illustrating the additional influence of variable positions. We then scanned 20 patients (9 women and 11 men, age range 18-26) before and 2 days after, third molar removal. The external, facial soft tissue volume changes were calculated for both left and right sides (range 0.2-64.3 cm3). The main source of inaccuracy was again variability of position. Despite this, the FastSCAN proved to be a simple, accurate, and non-invasive method of measuring postoperative changes in volume in the external, soft tissues of the face. Minimising variability in position by using more precise positioning techniques will increase the accuracy of this technique and is a focus for future work.

Adolescent↗

PubMed1997

Surface interpolation with radial basis functions for medical imaging.

Radial basis functions are presented as a practical solution to the problem of interpolating incomplete surfaces derived from three-dimensional (3-D) medical graphics. The specific application considered is the design of cranial implants for the repair of defects, usually holes, in the skull. Radial basis functions impose few restrictions on the geometry of the interpolation centers and are suited to problems where the interpolation centers do not form a regular grid. However, their high computational requirements have previously limited their use to problems where the number of interpolation centers is small (< 300). Recently developed fast evaluation techniques have overcome these limitations and made radial basis interpolation a practical approach for larger data sets. In this paper radial basis functions are fitted to depth-maps of the skull's surface, obtained from X-ray computed tomography (CT) data using ray-tracing techniques. They are used to smoothly interpolate the surface of the skull across defect regions. The resulting mathematical description of the skull's surface can be evaluated at any desired resolution to be rendered on a graphics workstation or to generate instructions for operating a computer numerically controlled (CNC) mill.

Algorithms↗

PubMed1997

Three-dimensional analysis techniques--Part 1: Three-dimensional soft-tissue analysis of 24 adult cleft palate patients following Le Fort I maxillary advancement: a preliminary report.

The three-dimensional, facial soft-tissue changes of 24 patients with various cleft types following transpalatal Le Fort I osteotomy were measured using laser scanning techniques, radial measurements, and a color millimetric scale. There was a varying degree of midface retrusion in the different cleft groups, and a very similar pattern of retrusion over the nasal complex. Each group of patients showed a varying degree of relapse postsurgically, but there was a failure in all the cleft groups to correct the lack of nasal projection.

Adolescent↗

PubMed1997

Three-dimensional analysis techniques--Part 2: Laser scanning: a quantitative three-dimensional soft-tissue analysis using a color-coding system.

New methods for measuring and averaging three-dimensional soft-tissue morphology and change from laser scans using a color millimetric scale are described. The techniques were employed to measure facial differences between a group of Class I skeletal males and females. The surgical change in one patient following bimaxillary surgery is also illustrated. The combination of the laser scanning technique and the new color coding system probed to be a simple, noninvasive, effective, and easily interpreted method for measuring three-dimensional soft-tissue differences and change across the facial complex.

Adolescent↗

PubMed1997

Three-dimensional analysis techniques--Part 3: Color-coded system for three-dimensional measurement of bone and ratio of soft tissue to bone: the analysis.

A new color-coded method of illustrating three-dimensional changes in the bone and the ratio of soft tissue to bone movement is described. The technique is illustrated by superimposing preoperative and 1-year postoperative CT scans of three patients following bimaxillary surgery. The method has proved to be a very simple, effective, and readily interpreted method of quantifying both bone and the ratio of movement of the overlying soft tissues across the face following surgery.

Adult↗

PubMed1997

Three-dimensional analysis techniques--Part 4: Three-dimensional analysis of bone and soft tissue to bone ratio of movements in 24 cleft palate patients following Le Fort I osteotomy: a preliminary report.

The three-dimensional changes in the bone and the ratio of soft tissue to bone movement were investigated in a group of 24 cleft palate patients following Le Fort I osteotomy. CT scans were taken for each patient preoperatively and 1 year postoperatively. The scans were superimposed, radial measurements calculated, and the changes illustrated by two separate color scales. In all of the groups, there was a fairly consistent pattern of movement over the mandible. The soft tissues moved in a 1.25:1 ratio over the chin and canine regions, and reduced to 1:1 over the body. In the maxilla, there was a 1:1 movement in the midline increasing to 1.25:1 bilaterally over the alar bases for both the bilateral clefts and clefts of the secondary palate groups. In the unilateral cleft group, however, there was a greater degree of movement over the cleft than over the noncleft side.

Adolescent↗

PubMed1995

Apnoea detection: human performance and reliability of a computer algorithm.

We examined the consistency of apnoea recognition between three human experts. The hypothesis was that computer detection of apnoea could emulate human expert apnoea recognition. The aim was to detect apnoeas with the highest possible accuracy from a single breathing signal, by both human experts and computer. Three human experts independently examined recordings of breathing wave-form from overnight sleep studies from 10 infants aged 3-17 weeks. All apnoeas of 5 s or more were identified and reviewed. However, there still remained 10% disagreement. A computer apnoea detector was implemented. An algorithm analysed statistical properties of the signal to find breathing pauses. Optimal performance was 1% missed apnoeas (compared with the agreed apnoeas identified by the three experts) and 29% false detections. This computer algorithm reliably identified most apnoeas but did not replace the human expert.

Algorithms↗

PubMed1994

A three-dimensional soft tissue analysis of fifteen patients with Class II, Division 1 malocclusions after bimaxillary surgery.

A three-dimensional soft tissue study of the results of surgery in a group of 15 women with Class II, Division I malocclusions after orthognathic surgery was performed with laser scans. A group of 30 women with Class I malocclusions ages between 19 and 25 years were used as controls. Laser scans were taken before surgery, 3 months after surgery, and at least 1 year after retention. The skeletal 2 patients were shown to have a narrowing of the face over the maxillary complex, checks, the nose, as well as around the alar bases, the so called "adenoid facies." There was also the expected mandibular deficiency. The effects of the bimaxillary surgery were not simply confined to the maxilla and the mandible, with soft tissue changes extending as far as the outer canthi of the eyes. There was very little relapse in the group as a whole from the third month to 1 year after surgery. This technique has proved to be a simple noninvasive method of measuring three dimensionally. It has proven to be a very useful tool in auditing surgical outcome and measuring surgical relapse.

Adult↗

PubMed1993

A three-dimensional analysis of bone and soft tissue to bone ratio of movements in 17 Skeletal II patients following orthognathic surgery.

The three-dimensional changes in the bone and the ratio of soft tissue to bone movement were investigated in a group of 17 Skeletal II patients following orthognathic surgery. CT scans were taken for each patient pre-operatively and 1 year post-operatively. The scans were superimposed, radial measurements calculated, and the changes illustrated by two separate colour scales. There was a constant ratio of movement over the maxillae with the central part of the upper lip being moved in a 1:1 ratio, increasing to a 1.25:1 ratio over the canine regions and 1.5:1 ratio over the paranasal areas. In the mandible there was a constant ratio of 1.25:1 over the chin, mentalis, and canine regions bilaterally. The ratio reduced to 1:1 over the body of the mandible.

Adaptation, Physiological↗

PubMed1993

A multistage system to detect epileptiform activity in the EEG.

A PC-based system has been developed to automatically detect epileptiform activity in sixteen-channel bipolar EEG's. The system consists of three stages: data collection, feature extraction, and event detection. The feature extractor employs a mimetic approach to detect candidate epileptiform transients on individual channels, while an expert system is used to detect focal and nonfocal multichannel epileptiform events. Considerable use of spatial and temporal contextual information present in the EEG aids both in the detection of epileptiform events and in the rejection of artifacts and background activity as events. Classification of events as definite or probable overcomes, to some extent, the problem of maintaining high detection rates while eliminating false detections. So far, the system has only been evaluated on development data but, although this does not provide a true measure of performance, the results are nevertheless impressive. Data from 11 patients, totaling 180 minutes of sixteen-channel bipolar EEG's, have been analyzed. A total of 45-71% (average 58%) of epileptiform events reported by the human expert in any EEG were detected as definite with no false detections (i.e., 100% selectivity) and 60-100% (average 80%) as either definite or probable but at the expense of up to nine false detections per hour. Importantly, the highest detection rates were achieved on EEG's containing little epileptiform activity and no false detections were made on normal EEG's.

Adolescent↗

PubMed1992

A three dimensional analysis of soft and hard tissue changes following bimaxillary orthognathic surgery in skeletal III patients.

The three dimensional changes in the bone and the ratio of soft tissue to bone movement were investigated in a group of 16 Skeletal III patients following orthognathic surgery. Computerised tomogram scans were taken for each patient pre-operatively and 1 year postoperatively. The scans were superimposed, radial measurements calculated, and the changes illustrated by two separate colour scales. There was no constant pattern of movement in the maxilla or mandible in these patients. However, following a Le Fort 1 osteotomy there was commonly a 1:1 ratio in the midline which increased to 1.25:1 at the alar bases and over the canine regions bilaterally. There was also a 1.25:1 ratio or greater over the chin and mentalis regions following mandibular set back.

Adult↗

PubMed1991

A microcomputer-based interactive cough sound analysis system.

The occurrence and nature of cough sounds, especially those occurring in asthma in young children, is of considerable interest to workers in paediatrics and general practice. To facilitate our research into the characteristics of such sounds, we have developed a microcomputer-based analysis system, which we call COFF. In this paper we discuss the design and implementation of the system, emphasising its user-friendly, interactive features, and the manner in which it efficiently manages the large amounts of data that research into sounds incurs. We illustrate the operation of the system with examples of spectrograms computed from cough sounds recorded simultaneously at the mouth and through the chest wall.

Asthma↗

PubMed1990

A low cost ECG central station for intensive care.

A electrocardiogram (ECG) central station has been developed for the Intensive Care Unit at Christchurch Hospital. The system allows the selection and display of four ECGs selected from seven bedside monitors in the Unit. It also provides for automatic display, hard copy and audio alarm of ECG from any monitor which has detected an alarm condition--irrespective of whether that channel was being displayed prior to alarm detection. The system comprises a control unit (based on an 8085 microprocessor) and a mobile ECG station (4-channel ECG monitor, ECG recorder and computer terminal). Over the three years since its installation, the central station has been used 24 hours a day by medical and nursing staff and has proven to be a valued and reliable instrument in an intensive care environment.

Electrocardiography↗

PubMed1989

Expert system approach to detection of epileptiform activity in the EEG.

An expert system for the automated detection of spikes and sharp waves in the EEG has been developed. The system consists of two distinct stages. The first is a feature extractor, written in the conventional procedural language Fortran, which uses parts of previously published spike-detection algorithms to produce a list of all spike-like occurrences in the EEG. The second stage, written in the production system language OPS5, reads the list and uses rules incorporating knowledge elicited from an electroencephalographer (EEGer) to confirm or exclude each of the possible spikes. Information such as the time of occurrence, polarity and channel relationship are used in this process. A summary of the detected epileptiform events is produced which is available to the EEGer in interpreting the EEG. The performance of the expert system is compared with an EEGer using a 320s segment from an EEG containing epileptiform activity. The system detected 19 events and missed seven (false negative) which the EEGer considered epileptiform. There were no false positive detections.

Biomedical Engineering↗