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Biomedical subjects

Tania S Douglas

Publications and source records attributed to Tania S Douglas.

7 recordsLinked to original sources
PubMed2006

Stereo image matching for facial feature measurement to aid in fetal alcohol syndrome screening.

The facial phenotype associated with fetal alcohol syndrome is identified through the measurement of facial distances and their comparison to population norms. As an alternative to time-consuming direct manual measurements, stereo photogrammetry has been used to obtain the required facial measurements from stereo digital photographs. While stereo photogrammetric measurement is faster, it requires manual marking of relevant facial landmarks on digital images. We present an algorithm that automatically finds matched feature points on the second of a pair of stereo images, after manual marking of the first. Standard image processing tools are used for preprocessing. Matching is based on a simple exhaustive search in an image window, with the sum of squared differences of the pixel intensities in the two images as the objective function. Eye measurements, namely palpebral fissure length, interpupillary distance, inner canthal distance and outer canthal distance, as well as distances that can be used to approximate the circularity of the upper lip, were obtained using the manual method of marking both images, and the method of automatic marking of the second image. Comparison revealed mean differences less than 1mm.

Anthropometry↗
PubMed2006

Multiple injuries diagnosed using full-body digital x-ray.

Missed injuries in patients with multiple trauma are primarily attributable to inadequate radiography. A case is presented that demonstrates the value of a full-body digital radiography system in diagnosing pathology in pediatric multiple trauma patients. Full-body imaging allowed the identification of a ruptured diaphragm, a pelvic fracture, and a femoral fracture on a single radiographic projection in the resuscitation room, facilitating immediate intervention.

Accidents, Traffic↗
PubMed2004

Image processing for craniofacial landmark identification and measurement: a review of photogrammetry and cephalometry.

Facial surface anthropometry and cephalometry have been used for many years for the diagnosis of malformations, surgical planning and evaluation, and growth studies. These disciplines rely on the identification of craniofacial landmarks. Methods for 3D reconstruction of landmarks have been introduced, as have image processing algorithms for the automation of landmark extraction. This paper reviews facial surface anthropometry and cephalometry with reference to the image processing algorithms that have been applied and their effectiveness.

Algorithms↗
PubMedDate not supplied

Role of depth in eye distance measurements: comparison of single and stereo-photogrammetry.

Photogrammetry has been used as an alternative to direct measurements to obtain facial distances for a variety of anthropometric applications. Taking measurements from photographs is less intrusive to subjects and reduces screening time, but measurements from single frontal photographs neglect depth information and may be inadequate for screening purposes. This study examined the role of depth in measurements of palpebral fissure length, interpupillary distance, inner canthal distance, and outer canthal distance using single- and stereo-photogrammetry; an operator selected landmarks on single and stereo digital photographs displayed on a computer monitor. Depth was not found to make a significant contribution to eye distances in an idealized system where the real-world coordinates of points on the eye were known from three-dimensional calibration of stereo photographs. However, the differences found between measurements taken from single frontal photographs and those from stereo-photogrammetry indicated that measurements from single photographs are prone to errors due to misalignment of the camera, the face, and the calibration instrument during image acquisition; if single photographs are to be used, the placement of these components should be carefully monitored.

Anthropometry↗
PubMedDate not supplied

Eye measurements in 7-year-old black South African children.

BACKGROUND: Ethnic variation often renders anthropometric reference values obtained in one population unsuitable for use in others. Fetal alcohol syndrome (FAS) diagnosis relies in part on the evaluation of certain anthropometric facial features. Measurements of these facial features in South African children have not been compared with measurements obtained in other populations. AIM: The study seeks to determine the suitability of reference values obtained in other populations for the diagnosis of the facial phenotype associated with FAS in South African children. PARTICIPANTS AND METHODS: Palpebral fissure length (PFL), interpupillary distance (IPD), inner canthal distance (ICD) and outer canthal distance (OCD) measured in a group of black South African children were obtained from digital photographs using stereophotogrammetry, and compared with measurements published for other populations. The study population comprised 17 7-year-old boys and 17 7-year-old girls. The precision and reliability of measurements were examined with reference to published data. RESULTS: Eye distance measurements in the study population do not consistently reflect those in any one other population for which such measurements have been published. CONCLUSION: Population-specific reference values of eye distance measurements should be established for South African children.

Anthropometry↗
PubMedDate not supplied

Digital radiographic measurement of the atlantodental interval in children.

The atlantodental interval (ADI) is assessed after trauma to the head and neck region to determine whether the transverse ligament of the atlas is intact. Atlantodental interval measurement from conventional screen-film radiographs is characterized by the need for magnification correction and by low reliability. Assessment of normal ADI values using digital radiography with computer-assisted measurement has not been reported. We compared with published values the digital radiographic measurements of ADI in children, examined the reliability of measurements, and examined the interaction between age, sex and ADI. Computer-assisted digital measurements of ADI in 101 children, aged 1 to 12 years, were obtained from lateral supine head-neutral radiographs. We found intraobserver reliability of 0.72 and 0.85, interobserver reliability of 0.50, a maximum ADI value of 3.5 mm, no effect of sex and age, and weak evidence for an interaction between sex and age. Computer-assisted digital ADI measurement provides higher intraobserver reliability than what has previously been reported, and interobserver reliability and a maximum ADI value similar to that found in the literature.

Axis, Cervical Vertebra↗