A Method to Quantify Supine to Prone Thoracoabdominal Deformation and Organ Migration in a Set of Healthy Young Adults.

Medical image data used for the development of computational human body models are often retrospectively acquired, and researchers are unlikely to encounter scans of healthy individuals in specific postures. We prospectively acquired scans in both prone and supine postures from 22 healthy young adults; M:F 1:1, with age, height, and weight of 28.8±7.0 years, 173.0±7.8 cm, and 70.6±10.9 kg. While prone, subjects’ arms were superior to the head and supported by a foam insert at axilla. Breath held, T1-weighted MRI scans were acquired using a Siemen’s Skyra 3T with an in-plane resolution of 1.56 mm (TR: 4.10 ms, TE: 1.23 ms, thickness: 2 mm, matrix: 256x256, FOV: 400 mm). Gross thoraco-abdominal compression was considered as the change in perpendicular distance in the transverse plane measured from the anterior margin of L4/L5 to the table (for prone) or exterior body surface (for supine). Gross thoraco-abdominal, liver and spleen compression were found to be 8.5% (71.6±12.9 mm prone vs. 78.7±12.4 mm supine; p=0.0013), 17.7% (110.4±4.1 mm prone vs. 134.8±2.6 mm supine; p<0.0001), and 3.5% (53.8±1.9 mm prone vs. 57.3±2.9 mm supine) respectively. Gender and spleen compression differences were not noted. The liver and spleen migrated on average 8.3 mm posteriorly, 11.4 mm rightward, 15.1 mm superiorly and 4.1 mm anteriorly, 6.1 mm rightward, 1.7 mm superiorly respectively. The data obtained from this set may be of use in computational biomechanics, surgical simulation, and medical device design.

CT based three-dimensional measurement of orbit and eye anthropometry.

PURPOSE: To measure eye and orbit anthropometric variation within the normal population by using CT images and to determine the effects of age and sex on eye and orbit anthropometry. Quantification of eye and orbit anthropometric variation within the normal population and between persons of different age and sex is important in the prediction and prevention of eye injury. METHODS: A systematic method was developed to align head CT images three dimensionally and to measure ocular and orbital parameters in 39 subjects. Twenty-four measurements were collected along the orbital rim, to quantify the orbital aperture. Protrusions of the brow and the eye were measured, along with relative distances, to describe location of the eye within the orbit. RESULTS: The orbit widened with age, and significant relations were identified between orbital aperture and eye location measurements, both of which varied significantly between the sexes. CONCLUSIONS: The comprehensive set of measurements collected in this study provides three-dimensional information on orbit geometry, as well as placement of the eye within the orbit. These measurements and the methodology used will contribute to the development of finite element models of the orbit and eye for computational modeling purposes and may be useful in the design of eye protection equipment.

Mesh development for a finite element model of the carotid artery.

A technique for developing a structured, hexahedral and quadrilateral mesh for use in finite element analyses of the carotid artery is presented. The model is reconstructed from 270 Computed Tomography (CT) images (slice thickness 0.625mm) of a 57 year old male subject and extends from the arch of the aorta to the base of the jaw. The structured mesh was generated using an unstructured, automatically generated tetrahedral mesh of the intimal surface of the carotid artery and its branches. A parametric meshing software package was used to create the structured mesh, facilitating mesh density studies. The change in volume and surface area introduced when converting the mesh from tetrahedral to hexahedral elements (+1.5% change in volume, -1.4% change in surface area) is small in comparison to estimated error introduced in the segmentation process. The technique introduced will benefit finite element and fluid dynamic studies of the carotid artery investigating mechanically induced pathology at both physiologic loading rates (i.e., atherosclerotic plaque formation) and high strain rates (i.e., blunt trauma).