Biomedical subjects

J De Guise

Publications and source records attributed to J De Guise.

4 recordsLinked to original sources

PubMed2005

Validation of new clinical quantitative analysis software applicable in spine orthopaedic studies.

The objective of this study was to evaluate an X-ray films analysis software, i.e. to estimate the reliability and validity of clinical measurements by means of this software. The authors first performed tests of precision and reproducibility of measures. The precision for dynamic modules was estimated at +/-2 degrees for the lumbar analysis and +/-3 degrees for the cervical one. Mean reproducibility coefficients calculated for postural modules are about 4 degrees for the angular parameters and 3 mm for the linear ones. We also evaluated clinical applicability of the software through its validity. Reference values calculated on a population of healthy subjects showed agreement with the literature. Then, when analysing postural X-ray films of severe scoliotic patients, we found that inter-observer reproducibility coefficients show a lower reliability of measurements; the main cause seems to be the low visibility of anatomic landmarks due to the quality of X-ray films and to the degree of deformity. This study allowed to better estimate the reliability and the usefulness of this tool, allowing for multicentric studies and exchanges.

Cervical Vertebrae↗

PubMed1998

[Morphometric characteristics of the scoliotic spine].

GOAL: Results from a morphometric investigation performed on a rare complete scoliotic specimen are presented. The aim of the study is to describe the vertebral body wedging. MATERIALS: The specimen used in the study presented a thoracic curve of 150 degrees Cobb angle with the apex at T8. The measures were made using 3D-computer graphics models. The wedging in the frontal and sagittal planes as well as the 3D wedging were measured. The height variation of the vertebral bodies was also measured. RESULTS: The wedging measures show that it increases progressively with the vertebral level to reach a maximum of 27 degrees at the apex. Perdriolle has found a linear relation between the vertebral body wedging and the Cobb angle. The relation predicts a wedging of 24 degrees for 150 degrees of Cobb angle. An inflection point was identified on the vertebral end plate on the convex side. These inflection points were described by Perdriolle as being on the concave side of the vertebra. CONCLUSION: Our measures follow the relation between the Cobb angle and the wedging of the vertebral body, even for very large Cobb angles. Furthermore, inflection points on the vertebral body were identified on the convex side as opposed to the concave side in the literature. This leads us to believe that the vertebral body wedging progressively affects the vertebral endplates.

Adult↗

PubMed1997

[Evaluation of peroperative measurement system in the follow-up of vertebral displacements].

A computer assisted surgery system has been developed to quantify the vertebral displacements induced by the Cotrel-Dubousset instrumentation and to visualize in 3-D the spine at different per-operative steps. This spinal surgery is realized to correct idiopathic scoliosis. Per-operative measurements are obtained by using a magnetic digitizer. Five points per thoracic vertebra and six points per lumbar vertebra are digitized. The method proposed estimates the location of the digitized points on a computer graphics 3-D model of vertebrae by a point-to-surface matching algorithm. The 3-D models are constructed before the surgery using multiplanar radiographic reconstruction technique (2 or 3 views) and geometric modeling methods. Computer tools permit the 3-D visualization of the spine peroperatively and the evaluation of clinical indices such as Cobb angles and vertebral rotations. The system includes 3 principal error sources: 2) reconstruction error; 2) digitizer error (digitizer precision) and 3) point-to-surface matching error. In order to validate the overall system, measurements have been simulated for 2 vertebrae and 2 digitizers of different precision, taking onto account the reconstruction error. For 5 and 6 digitized points per vertebra, the matching algorithm gives a RMS error of respectively 3.0 and 2.0 mm.

Biomechanical Phenomena↗

PubMed1991

Adipose tissue volume measured by magnetic resonance imaging and computerized tomography in rats.

The primary purpose of this study was to investigate the viability of magnetic resonance imaging (MRI) as a means of measuring the body composition of rodents. To do so we compared adipose tissue (AT) volumes measured by MRI with those obtained by X-ray computerized tomography (CT) in a group of rats (n = 17) varying in weight (465-815 g) and percent body fat (5.4-31.1%), with the latter determined by chemical analysis. For both MRI and CT, AT volumes (cm3) per transverse slice (3-mm thickness, 21-mm centers) were determined using a computer-based image analysis system that permitted detailed comparisons of both visceral and subcutaneous AT depots. Total AT volumes were calculated using a linear interpolation of AT areas obtained on consecutive slices. Correlation coefficients between MRI and CT for visceral [r = 0.98, standard error of estimate (SEE) = 6.8 cm3], subcutaneous (r = 0.98, SEE = 6.5 cm3), and total AT volumes (r = 0.99, SEE = 9.0 cm3) were highly significant (P less than 0.001). Both MRI- and CT-predicted AT mass (assuming fat density = 0.90 g/ml) correlated strongly with chemically extracted lipid (grams) values (r = 0.98, SEE 9.6 g and r = 0.99, SEE = 6.9 g, respectively). Post hoc Scheffé contrasts demonstrated that the mean AT and lipid mass values derived by the three methods were not significantly different (P = 0.01). No systematic differences were observed because the regression lines derived for either MRI or CT vs. chemical analysis were not significantly different from the identity line.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗