Contents lists available at ScienceDirect Journal of Forensic Radiology and Imaging journal homepage: www.elsevier.com/locate/jofri Part I – Adult skeletal age estimation using CT scans of cadavers: Revision of the fourth rib methods Catherine E Merritt Centre for Anatomy and Human Identification, University of Dundee, Dundee DD1 5EH, UK ARTICLE INFO Keywords: Forensic anthropology Adult skeletal age estimation Fourth rib CT scans Volume-rendered images İşcan et al. methods Hartnett method ABSTRACT 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 İşcan 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 İşcan 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 İşcan 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. 1. Introduction Biological and forensic anthropologists routinely rely upon the İşcan et al. fourth rib approach as one of a suite of methods used to estimate age at death from adult skeletal remains [1,2]. İşcan and colleagues based their method on McCormick's observation of age- related costal cartilage ossification [3]. They developed an eight- phase system focused on age-related changes to the sternal rib ends of fourth ribs using a sample of 93 males between the ages of 17 and 90 years, and 86 females between the ages of 14 and 90 years, all of American-European ancestry [4,5]. Their method has been widely tested and is generally accepted as a reliable, replicable, uni-modal indicator for estimating age [6–10], although population differences have been noted [11–13]. In 2010, two revisions of the methods were published. Hartnett revised the İşcan et al. methods by combining the male and female specific approaches and reducing the number of phases from eight to seven by truncating the younger phases [14], and this method has been found to be reliable for modern populations [10]. Verzeletti and colleagues revised the methods by creating a three-component system based on the sternal surface, anterior and posterior walls, and superior and inferior edges [15]. However, most biological and forensic anthropologists still rely on the original İşcan et al. methods [1,2]. With the increased use of CT scanners both in research and forensic facilities, biological and forensic anthropologists are being asked to apply their knowledge of skeletal anatomy to 3D volume-rendered images (VRIs) of skeletons generated from CT scans. CT scans are used by researchers to create biological profiles of mummies, and skeletons are being scanned both for research and recording purposes prior to repatriation to maintain digital records of specimens. Large forensic facilities around the world use CT scans as part of their standard au- topsy procedures, and forensic anthropologists aid with the identifica- tion of unidentified individuals by providing biological profiles of partially skeletonized, mummified, or even fleshed individuals to help match them to missing persons databases. Therefore, testing the com- monly used age estimation methods developed by biological and for- ensic anthropologists for use on skeletal remains on VRIs is important in order to establish whether the age-related features observed on skeletal https://doi.org/10.1016/j.jofri.2018.08.003 Received 12 January 2018; Received in revised form 11 August 2018; Accepted 13 August 2018 E-mail address: catherine.merritt@mail.utoronto.ca. Journal of Forensic Radiology and Imaging 14 (2018) 39–49 Available online 25 August 2018 2212-4780/ © 2018 Elsevier Ltd. All rights reserved. T