OBJECTIVE: To assess the reliability of computed tomography (CT) numbers, also known as Hounsfield-units (HU) in the differentiation and identification of forensically relevant materials and to provide instructions to improve the reproducibility of HU measurements in daily forensic practice. MATERIALS AND METHODS: We scanned a phantom containing non-organic materials (glass, rocks and metals) on three different CT scanners with standardized parameters. The t-test was used to assess the influence of the scanner, the size and shape of different types of regions-of-interest (ROI), the composition and shape of the object, and the reader performance on HU measurements. Intra-class correlation coefficient was used to assess intra- and inter-reader reliability. RESULTS: HU values did not change significantly as a function of ROI-shape or -size (p>0.05). Intra-reader reliability reached ICC values >0.929 (p<0.001). Inter-reader reliability was also excellent with an ICC of 0.994 (p<0.001). Four of seven objects yielded significantly different CT numbers at different levels within the object (p<0.05). In 6/7 objects the HU changed significantly from CT scanner to CT scanner (p<0.05). CONCLUSION: Reproducible CT number measurements can be achieved through correct ROI-placement and repeat measurements within the object of interest. However, HU may differ from CT-scanner to CT-scanner. In order to obtain comparable CT numbers we suggest that a dedicated Forensic Reference Phantom be developed.
OBJECTIVE: To assess the reliability of computed tomography (CT) numbers, also known as Hounsfield-units (HU) in the differentiation and identification of forensically relevant materials and to provide instructions to improve the reproducibility of HU measurements in daily forensic practice. MATERIALS AND METHODS: We scanned a phantom containing non-organic materials (glass, rocks and metals) on three different CT scanners with standardized parameters. The t-test was used to assess the influence of the scanner, the size and shape of different types of regions-of-interest (ROI), the composition and shape of the object, and the reader performance on HU measurements. Intra-class correlation coefficient was used to assess intra- and inter-reader reliability. RESULTS: HU values did not change significantly as a function of ROI-shape or -size (p>0.05). Intra-reader reliability reached ICC values >0.929 (p<0.001). Inter-reader reliability was also excellent with an ICC of 0.994 (p<0.001). Four of seven objects yielded significantly different CT numbers at different levels within the object (p<0.05). In 6/7 objects the HU changed significantly from CT scanner to CT scanner (p<0.05). CONCLUSION: Reproducible CT number measurements can be achieved through correct ROI-placement and repeat measurements within the object of interest. However, HU may differ from CT-scanner to CT-scanner. In order to obtain comparable CT numbers we suggest that a dedicated Forensic Reference Phantom be developed.
Authors: Nicole Berger; Lars C Ebert; Garyfalia Ampanozi; Patricia M Flach; Dominic Gascho; Michael J Thali; Thomas D Ruder Journal: Forensic Sci Med Pathol Date: 2015-01-08 Impact factor: 2.007
Authors: Thomas D Ruder; Yannick Thali; Stephan A Bolliger; Sandra Somaini-Mathier; Michael J Thali; Gary M Hatch; Sebastian T Schindera Journal: Forensic Sci Med Pathol Date: 2012-12-21 Impact factor: 2.007
Authors: Josef M Kutschy; Garyfalia Ampanozi; Nicole Berger; Thomas D Ruder; Michael J Thali; Lars C Ebert Journal: Forensic Sci Med Pathol Date: 2014-08-13 Impact factor: 2.007
Authors: Lars C Ebert; Jakob Heimer; Wolf Schweitzer; Till Sieberth; Anja Leipner; Michael Thali; Garyfalia Ampanozi Journal: Forensic Sci Med Pathol Date: 2017-08-18 Impact factor: 2.007
Authors: Desirée H J L M Koopmanschap; Alireza R Bayat; Bela Kubat; Henri M de Bakker; Mathias W M Prokop; Willemijn M Klein Journal: Forensic Sci Med Pathol Date: 2016-04-27 Impact factor: 2.007