Biomedical subjects

A J Naftel

Publications and source records attributed to A J Naftel.

4 recordsLinked to original sources

PubMed2004

Stereo-assisted landmark detection for the analysis of changes in 3-D facial shape.

In this paper, a semi-automated approach to 3-D landmark digitization of the face is described which uses a combination of active shape model-driven feature detection and stereophotogrammetric analysis. The study aims to assess whether the proposed method is capable of detecting statistically significant changes in facial soft tissue shape due to mandibular repositioning in a cross-sectional patient sample. A hybrid stereophotogrammetric and structured-light imaging system is used for acquiring 3-D face models in the first instance. A landmark-based statistical analysis of facial shape change is then carried out using procrustes registration, principal component analysis and thin plate spline warping on the 2-D facial midline profiles and automatically digitized 3-D landmarks. The proposed method is validated both statistically and visually by characterizing shape changes induced by mandibular repositioning in a heterogeneous cross-sample of 20 orthodontic patients. It is shown that the method is capable of distinguishing between changes in facial morphology due to simulated surgical correction and changes due to other factors such as growth and normal variation within the patient sample. The study shows that the proposed method may be useful for auditing outcomes of clinical treatment or surgical intervention which result in changes to facial soft tissue morphology.

Adolescent↗

PubMed2001

Studying the epidemiology of attention-deficit hyperactivity disorder: screening method and pilot results.

OBJECTIVE: As part of a larger epidemiologic study of risk factors for attention-deficit hyperactivity disorder (ADHD), this pilot study combined parent and teacher information to estimate ADHD prevalence among elementary school children in a North Carolina county. The methods developed for this study and the pitfalls we encountered illustrate the challenges involved in conducting population-based studies of ADHD. METHODS: We employed 2-stage screening using DSM-IV criteria. Teachers completed behaviour-rating scales for all children. We then administered a structured telephone interview to parents of potential cases. We screened 362 of 424 (85%) children in grades 1 to 5 in 4 schools. RESULTS: According to parent reports, 43 children (12%) had previously been diagnosed with ADHD by a health professional. Thirty-four children (9%) were taking ADHD medication. Forty-six children (12.7%) met study case criteria for ADHD, based on combined teacher and parent reports. Of the 46 cases, 18 (39%) had not been previously identified. Eight previously diagnosed children, however, did not meet case criteria. After we adjusted for nonresponse, the estimated prevalence was 16% (95%CI, 12% to 20%). CONCLUSIONS: These data suggest that the DSM-IV prevalence of ADHD has been substantially underestimated, although the true prevalence in this population may be less than the 16% estimated here. Population-based studies of ADHD are feasible and may provide important information about practice and treatment patterns in community settings, as well as a broader understanding of the etiology and life course of this common disorder.

Attention Deficit Disorder with Hyperactivity↗

PubMed1999

Differences in cephalometric reference values between five centres: relevance to the Eurocleft Study.

Cephalometric data from five different geographical areas (Oslo, Manchester, London, Nijmegen, and Michigan) were compared. The angles SNA, SNB, and ANB were taken from published tables in the form of mean, standard deviation (SD) and number in the sample, divided up by age and sex. Angles SNA and SNB were significantly different among centres on univariate analysis. The Oslo data showed 23 instances in which they differed significantly from the other data, London 16, Manchester 11, Nijmegen 11, and Michigan 7. Multivariate analysis using Penrose distances were Oslo (2.04), Manchester (1.39), London (0.93), Nijmegen (0.80), and Michigan (0.66). The sums of the Mahalanobis distances were Nijmegen (3.60), Oslo (3.10), London (2.80), Manchester (2.25), and Michigan (1.49). As these results probably reflect racial and genetic differences, these must be taken into account when international comparisons are being made, as in the Eurocleft study.

Age Factors↗

PubMed1992

Bodymap: an image processing system for the measurement of body surface profiles encountered in skin expansion surgery.

A personal computer based image processing system for the mapping and subsequent analysis of local areas of the human body requiring no more than 180 degrees of vision is described. The operations of image capture and data extraction are undertaken in real time and photogrammetric reconstruction takes typically a further 30 s. Accuracy of the system has been assessed by photogrammetrically reconstructing 37 points whose coordinates had been precisely established by traditional survey techniques. An average discrepancy between surveyed and reconstructed positions of 0.485 mm was obtained; this level of accuracy compares highly favourably with results achieved using alternative methods and which do not have the level of automation inherent in the described system. The system has been developed specifically to provide quantitative values for parameters of particular interest in skin expansion surgery: consequently the post-reconstruction facilities available in this initial system are surface area and enclosed volume calculations and shaded surface display. Further development work currently in progress is also briefly discussed.

Body Surface Area↗