Cranial interlandmark distances from CT bone models of 330 living persons
Description
Simmons-Ehrhardt et al. [12] reported averaged cranial measurements, derived from 3D bone models of CT scans collected from 303 living subjects in the U.S.A. The CT database comprised both sexes and three ancestry groups, African female (n=62), African male (n=48), Asian female (n=48), Asian male (n=47), European female (n=50), European male (n=48). ILDs were compared to populations in the Forensic Data Bank [18] representing similar demographic groups and each subject was classified using Fordisc 3 [19, 20]. Data in the Forensic Data Bank were collected by various contributors using traditional measurements on dry skulls. Standard craniometric definitions were used to make most measurements, but three were adjusted slightly from their original definition for caliper measurements [18] to accommodate collection between landmarks in the CT modality. Maxillofrontale (MfL/R), as defined by White [21], was selected over dacryon to estimate orbital breadth (OBB) due to the inability to see dacryon on many CT scans. Orbital height (OBH) was measured by placing one landmark at approximately the midpoint of the superior orbital border (MsorL/R) and a second landmark on the inferior orbital border (IorL/R), approximating a line perpendicular to orbital breadth (OBB). Traditional caliper-derived measurements such as maximum cranial breadth (XCB) were collected by locating and adjusting the positions of left and right euryon (Eu) in the orthogonal views of the CT slices as well as the 3D model to estimate the most lateral points of the skull. After landmark placement, all distances were calculated by Mimics as the 3D distance between the two specified landmarks. [12] T. Simmons-Ehrhardt, C. Ehrhardt, K. Monson, Evaluation of the suitability of cranial measurements obtained from surface-rendered CT scans of living people for estimating sex and ancestry, J Forensic Radiol Imag 19 (2019) 100338. doi:10.1016/j.jofri.2019.100338. [18] P.H. Moore-Jansen, S.D. Ousley, R.L. Jantz, Data collection procedures for forensic skeletal material, Forensic Anthropology Center, Department of Anthropology, University of Tennessee, Knoxville 1994. [19] R. Jantz, S.D. Ousley, FORDISC 3.0: Computerized Forensic Discriminant Functions, The University of Tennessee, Knoxville, 2005. [20] S.D. Ousley, R.L. Jantz, Fordisc 3 and statistical methods for estimating sex and ancestry, in: D.C. Dirkmaat (Ed.), A Companion to Forensic Anthropology, Wiley-Blackwell, Chichester, 2012, pp. 349-367. [21] T.D. White, P.A. Folkens, Human Osteology, 2nd ed., Academic Press, San Diego, 2000.
Files
Steps to reproduce
Adult CT scans were collected between 2003-2009 by GE Global Research for use as a reference database for ReFace. Collection and intended use of these anonymized data were approved by the institutional research boards of the partner institutions, and each subject signed an informed consent agreement. The CT scans were acquired from multiple institutions and were collected under a variety of scanning protocols, with slice thicknesses ranging from 0.98 mm to 6.00 mm, slice increments ranging from 0.10 mm to 5.00 mm, pixel size ranging from 0.449 mm to 0.586 mm, and three X-Y image resolutions [5]. Mimics v.11.1 and v.12.0 software (Materialise, Ann Arbor, MI) was used to convert CT scans to separate 3D bone and skin models. Bone was segmented from soft tissue using a threshold value of 226 Hounsfield units. Segmentation masks were edited prior to 3D reconstruction to remove large dental artifacts and vertebrae to allow better access to craniometric landmarks. The simulation module of Mimics was used to place landmarks on the digital 3D skulls [12]. [5] C.L. Parks, A.H. Richard, K.L. Monson, Preliminary assessment of facial soft tissue thickness utilizing three-dimensional computed tomography models of living individuals, Forensic Sci. Int. 237 (2014) 146.e1-146.e10. doi:10.1016/j.forsciint.2013.12.043. [12] T. Simmons-Ehrhardt, C. Ehrhardt, K. Monson, Evaluation of the suitability of cranial measurements obtained from surface-rendered CT scans of living people for estimating sex and ancestry, J Forensic Radiol Imag 19 (2019) 100338. doi:10.1016/j.jofri.2019.100338.