Accuracy and reliability of facial soft tissue depth measurements using cone beam computer tomography

Fourie, Zacharias; Damstra, Janalt; Gerrits, Peter O.; Ren, Yijin

doi:10.1016/j.forsciint.2010.02.018

« Previous Next »Forensic Science International
Volume 199, Issue 1 , Pages 9-14, 15 June 2010

Accuracy and reliability of facial soft tissue depth measurements using cone beam computer tomography

Zacharias Fourie
- University Medical Center Groningen, University of Groningen, Department of Orthodontics, Hanzeplein 1, 9700 RB Groningen, The Netherlands
- Corresponding author at: University Medical Center Groningen, University of Groningen, Department of Orthodontics, Hanzeplein 1, P.O. Box 30001, 9700 RB Groningen, The Netherlands. Tel.: +31 50 361 0092; fax: +31 50 361 9712.
Janalt Damstra
- University Medical Center Groningen, University of Groningen, Department of Orthodontics, Hanzeplein 1, 9700 RB Groningen, The Netherlands
Peter O. Gerrits
- University Medical Center Groningen, University of Groningen, Department of Anatomy, Hanzeplein 1, 9700 RB Groningen, The Netherlands
Yijin Ren
- University Medical Center Groningen, University of Groningen, Department of Orthodontics, Hanzeplein 1, 9700 RB Groningen, The Netherlands

Received 20 September 2009; received in revised form 4 February 2010; accepted 15 February 2010. published online 17 March 2010.

Abstract

It is important to have accurate and reliable measurements of soft tissue thickness for specific landmarks of the face and scalp when producing a facial reconstruction. In the past several methods have been created to measure facial soft tissue thickness (FSTT) in cadavers and in the living. The conventional spiral CT is mostly used to determine the FSTT but is associated with high radiation doses. The cone beam CT (CBCT) is a relatively new computer tomography system that focuses on head and neck regions and has much lower radiation doses. The aim of this study is to determine the accuracy and reliability of CBCT scans to measure the soft tissue thicknesses of the face. Seven cadaver heads were used. Eleven soft tissue landmarks were identified on each head and a punch hole was made on each landmark using a dermal biopsy punch. The seven cadaver heads were scanned in the CBCT with 0.3 and 0.4mm resolution. The FSTT at the 11 different sites (soft tissue landmarks) were measured using SimPlant-ortho volumetric software. These measurements were compared to the physical measurements. Statistical analysis for the reliability was done by means of the interclass coefficient (ICC) and the accuracy by means of the absolute error (AE) and absolute percentage error (APE). The intra-observer (0.976–0.999) and inter-observer (0.982–0.997) correlations of the CBCT and physical measurements were very high. There was no clinical significant difference between the measurements made on the CBCT images and the physical measurements. Increasing the voxel size from 0.4 to 0.3mm resulted in a slight increase of accuracy. Cone beam CT images of the face using routine scanning protocols are reliable for measuring soft tissue thickness in the facial region and give a good representation of the facial soft tissues. For more accurate data collection the 0.3mm voxel size should be considered.