Part I - Adult skeletal age estimation using CT scans of cadavers: Revision of the fourth rib methods

Objective: CT scans have become a standard part of autopsy procedures in large medical-legal facilities, and forensic anthropologists are increasingly asked to contribute their knowledge of skeletal anatomy to volume-rendered images (VRIs) generated from CT scans. However, it is not clear if the age estimation methods created using skeletal remains can be reliably applied to VRIs. This study, along with the other two in this series, examines the applicability of three commonly used sites for adult skeletal age estimation on VRIs generated from CT scans of cadavers. Part I focuses on the fourth rib. Materials and methods: CT scans of 420 cadavers from the Victorian Institute of Forensic Medicine were selected (age range 20-79 years). Siemens syngo.via software was used to view the DICOM images and create the VRIs. The Iscan et al. and Hartnett fourth rib methods of age estimation were used to create a revised method for VRIs. Results and conclusion: Several features described by both Iscan et al. and Hartnett could be observed on the VRIs; however, features such as porosity inside the sternal rib and bone weight could not be assessed. A revised fourth rib method for use on VRIs was created. Significantly more individuals were placed in the correct age phase using the revised method compared to the Iscan et al. and Hartnett methods, and overall the revised method had significantly improved inaccuracy and bias scores. The revised method is reliable and should be tested on other populations using different software.