Biomedical subjects

T S Douglas

Publications and source records attributed to T S Douglas.

8 recordsLinked to original sources

PubMed2006

Causes and distribution of facial fractures in a group of South African children and the value of computed tomography in their assessment.

The cases of 107 paediatric patients aged 0-12 years were retrospectively reviewed. The patients presented with facial trauma and both plain radiographs and computed tomography (CT) scans had been ordered. Sixty-five per cent of facial fractures were missed in radiography, but revealed on CT; fractures of the maxilla, the zygoma and the orbit were most frequently missed in radiography. Pedestrian motor vehicle accidents were the most frequent cause of facial fractures (37%), followed by passenger motor vehicle accidents (22%). In contrast with other studies reporting the mandible as the most frequent facial fracture site, the most common fracture sites in this study, in descending order of frequency, were the orbit, the frontal bone and the maxilla.

Accidental Falls↗

PubMed2004

Three-dimensional point localisation in low-dose X-ray images using stereo-photogrammetry.

A stereo-photogrammetric method for three-dimensional reconstruction of points in low-dose digital X-ray images obtained using a scanner with similar imaging geometry to that of computed tomography scan projection radiography, was analysed. A calibration frame containing 25 radio-opaque markers with known three-dimensional locations was scanned, and the accuracy of reconstruction of the marker positions under varying control point configurations and separation angles was assessed. Errors of less than 1 mm were obtained when nine test points were reconstructed, with 16, 11 and 7 control points at a 90 degrees separation angle, and with 16 and 11 control points at 75 degrees and 60 degrees separation angles. The optimum reconstruction, with a resultant error of 0.68 mm, was found to occur at a separation angle of 90 degrees, with the largest number of control points (16) used to calculate the parameters of the transformation. Extrapolation in the scanning direction beyond the space defined by the control points gave errors of less than 2 mm. This method should be suitable for three-dimensional point reconstruction in applications such as cephalometry, brachytherapy planning and assessment of spinal shape.

Humans↗

PubMed2003

Eye feature extraction for diagnosing the facial phenotype associated with fetal alcohol syndrome.

Victims of fetal alcohol syndrome (FAS) exhibit a unique facial phenotype that is emphasised in diagnosis. Among the characteristic facial features, several occurring in the region of the orbits can be evaluated quantitatively using distance measurements. An algorithm is described for automatic extraction and measurement of eye features from stereo photographs. The algorithm was applied to photographs of 46 six-seven-year-old children. The approach relies on peak and valley maps and integral projection functions, to locate the eyes and extract the iris, and genetic algorithms to fit cubic splines to the upper and lower eyelids. Measurements obtained automatically using this algorithm were compared with measurements obtained manually from the photographs. Mean absolute differences between automatic and manual measurements were less than 1 mm for palpebral fissure length (PFL) and interpupillary distance (IPD). Absolute differences were less than 1 mm for 80.4% of PFLs and 100% of IPDs. Inner canthal distance and outer canthal distance did not compare favourably with manual measurements.

Algorithms↗

PubMed2002

Ultrasound image matching using genetic algorithms.

Image compounding reduces the artifacts inherent in ultrasound imaging, but accurate matching of images for compounding depends on their accurate placement in the compound image plane. A method is presented to reduce displacement errors during compounding of ultrasound B-scans of a normal human shank. A genetic algorithm was used to place matching B-scans in the compound image. The method was tested on a phantom and was shown to reduce, but not eliminate, mismatches due to the displacement of B-scans from their original position in the compound image plane. The results can be extended to applications in lower-limb prosthetics, where ultrasound imaging can be used to visualise the internal geometry of amputees' residual limbs.

Algorithms↗

PubMed2002

A stereo-photogrammetric method to measure the facial dysmorphology of children in the diagnosis of fetal alcohol syndrome.

In diagnosing a child with fetal alcohol syndrome (FAS), anthropometric measurements of the face are conventionally performed by highly trained dysmorphologists using a hand-held ruler. This renders the screening of large populations of children for the facial features characteristic of FAS very time-consuming and costly. This study proposes a new, cost-effective, and non-intrusive method to measure in three dimensions the facial dysmorphology of children using stereo-photogrammetry. The face of each child is photographed in a control frame simultaneously by a pair of high-resolution digital cameras mounted 1.04 m from the child and 0.26 m apart. Software has been developed to calibrate the images and to compute the three-dimensional object-space coordinates of any point on the face from a measurement of the point on each of the images. The palpebral fissure lengths, inner canthal-, and interpupillary distances of 44 subjects were measured in this manner independently by two investigators and compared with measurements obtained by clinical specialists in the conventional manner. There was found to be no statistically significant difference between palpebral fissure lengths determined using the two techniques (paired Student's t-test p-values are 0.29 and 0.18, respectively). It has also been demonstrated that facial measurements can be performed with greater consistency from a pair of stereo photographs than direct measurements from live subjects.

Anthropometry↗

PubMed1998

Automatic segmentation of magnetic resonance images of the trans-femoral residual limb.

An automatic algorithm for the extraction of the skin and bone boundaries from axial magnetic resonance images of the residual limb of trans-femoral amputees is presented. The method makes use of K-means clustering and mathematical morphology. Statistical analysis of the results indicates that the computer-generated boundaries compare favourably to those drawn by human observers. The boundaries may be used in biomechanical modelling of the interaction between the residual limb and the prosthetic socket. The limb/socket interface determines the quality of prosthetic fit, therefore knowledge of this interface is important for the improvement of socket design in order to achieve patient comfort and mobility.

Adipose Tissue↗

PubMed1998

Evaluation of preoperative patient education and computer-assisted patient instruction.

Health care practitioners believe that patient education enhances patients' compliance with treatment, their medical outcomes, and their quality of life. This study evaluated an existing method of noncomputerized structured preoperative education delivered by a nurse specialist and implemented and evaluated a computer-assisted instruction (CAI) tool for nonsurgical patients in the Vanderbilt Orthopaedic Spine Service. These patient education modalities were assessed with regard to the patient health concepts measured in the Short Form-36 Health Survey and, in addition, for preoperative education, with regard to the length of patient hospital stay. Preoperative education improved patient perceptions of vitality and mental health, increased length of stay for discectomy patients, and had no effect on length of stay for other surgical procedures. CAI improved patient perceptions of bodily pain.

Computer-Assisted Instruction↗

PubMed1993

Experimental modes of Caryospora bigenetica (Apicomplexa: Eimeriidae) infection in swine and the effects of temperature and salinity on parasite infectivity in porcine tissue.

Four crossbred pigs (Sus scrofa) were inoculated orally with Caryospora bigenetica oocysts derived from snake and mouse feces, and with C. bigenetica infected mouse tissue. One pig also was given i.m. injections of methylprednisolone acetate. All four pigs displayed clinical signs including erythema, edema, and lethargy. Caryocysts were observed histologically in numerous tissues including ear, tongue, jowl, shoulder, loin, intercostal, ham, hock, and feet. The four pigs each were butchered into six commercial cuts: shoulder, loin, side, ham, hock, and feet. Raw 10 g samples from each cut were bioassayed by pepsin digestion and s.c. inoculation into 12 Swiss-Webster mice (Mus musculus) and 12 cotton rats (Sigmodon hispidus). Seventeen of 24 mice and cotton rats exhibited clinical signs and C. bigenetica tissue infections. Remaining portions of the six commercial cuts were temperature or saline treated, and 10 g samples were bioassayed in 16 mice and 12 cotton rats. No clinical sign or tissue infection was observed in these animals. Our study presents evidence that swine can be infected with C. bigenetica by ingesting oocysts present in snake feces or mouse feces (following inoculation of mice with snake-derived oocysts) or by ingesting C. bigenetica infected rodent tissue, that endogenously produced C. bigenetica oocysts are not excreted in the feces of swine, and that C. bigenetica in pork can be rendered noninfective by freezing at -20 degrees C (-4 degrees F) for 21 days, frying at 84 degrees C (183 degrees F) for 17 min, microwaving at 88 degrees C (190 degrees F) for 17 min, grilling at 82 degrees C (180 degrees F) for 48 min, baking at 95 degrees C (203 degrees F) for 230 min, boiling at 100 degrees C (212 degrees F) for 60 min, or by curing at 4 degrees C (39 degrees F) for 20 days.

Animals↗