The geometrical precision of virtual bone models derived from clinical computed tomography data for forensic anthropology

Colman, Kerri L.; Dobbe, Johannes G. G.; Stull, Kyra E.; Oostra, Roelof‐Jan; Rijn, Rick R. van; Merwe, Alie E. van der; Boer, Hans H. de; Streekstra, Geert J.

doi:10.1007/s00414-017-1548-z

Cited by 42 publications

(31 citation statements)

References 34 publications

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“…No validation study exists to date for virtual measurements of the calcaneus compared to measurements on the dry bone. We do not however anticipate the error to exceed the acceptable threshold of 2mm that was reported for other skeletal elements [47][48].…”

Section: Discussioncontrasting

confidence: 54%

“…One could argue that measurements taken on virtual models, as in our case, may introduce an error in the study as they are generally considered less reliable compared to measurements on the dry bone. Recent validation studies on the cranium/long bones [47] and pelvis [48] suggest that the measurement error on virtual bones does not exceed 2mm, which implies high reliability. No validation study exists to date for virtual measurements of the calcaneus compared to measurements on the dry bone.…”

Section: Discussionmentioning

confidence: 99%

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Sex estimation in a contemporary Turkish population based on CT scans of the calcaneus

Ekizoğlu¹,

İnci

Palabıyık

et al. 2017

Forensic Science International

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Building a reliable biological profile from decomposed remains depends heavily on the accurate estimation of sex. A variety of methods based on every single skeletal element have been developed over the years for different populations employing both osteological and virtual methods. The latter seem to be a reasonable alternative in countries lacking osteological reference collections. The current study used 3D virtual models of calcanei from CT scans of living adults to develop a sex estimation method for contemporary Turkish. Four hundred and twenty eight calcanei CT scans were analysed. The sample was divided in two subsamples: an original (N=348) and a validation sample (N=80) with similar distribution of males and females. Nine classical measurements were taken using the 3D models of the calcanei and two different statistical methods (Discriminant function analysis and Binary logistic regression) were used. Classification accuracy ranged from 82% to 98% for the validation sample and it was consistently high using any of the two methods. Sex bias seems to be lower for most of the logistic regression equations compared to the discriminant functions. These results, however, need further testing to be verified. Based on the results of this study we recommend the use of both methods for sex estimation from the measurements of the calcaneus bone in a Turkish population.

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Section: Discussioncontrasting

confidence: 54%

Section: Discussionmentioning

confidence: 99%

Sex estimation in a contemporary Turkish population based on CT scans of the calcaneus

Ekizoğlu¹,

İnci

Palabıyık

et al. 2017

Forensic Science International

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“…Using different scanner types and software packages for volume data acquisition might have induced artefactual variance in the superimposed Landmark Dataset 1; we did not account for this, as a previous study found only minor effects of scanner type on the geometry of derived polygon surfaces (Colman et al. ). If there was artefactual variance caused by CT scanning and volume reconstruction, this would be incorporated in the factor ‘specimen’ in the permanova .…”

Section: Methodsmentioning

confidence: 99%

“…Voxel size has had a considerable effect on measurements and the effect of the segmentation method seemed to increase with voxel size (Christiansen, 2016). Scanner type and imaging conditions have affected the geometry of surfaces generated from CT scans, although the effects have been small compared with the variance introduced by manual segmentation (Colman et al 2017). All the factors influencing the segmentation results and the geometry of a CT-derived surface potentially contribute to measurement error in landmark data obtained from such surfaces.…”

Section: Introductionmentioning

confidence: 99%

Measurement error in μCT‐based three‐dimensional geometric morphometrics introduced by surface generation and landmark data acquisition

et al. 2019

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Computed‐tomography‐derived (CT‐derived) polymesh surfaces are widely used in geometric morphometric studies. This approach is inevitably associated with decisions on scanning parameters, resolution, and segmentation strategies. Although the underlying processing steps have been shown to potentially contribute artefactual variance to three‐dimensional landmark coordinates, their effects on measurement error have rarely been assessed systematically in CT‐based geometric morphometric studies. The present study systematically assessed artefactual variance in landmark data introduced by the use of different voxel sizes, segmentation strategies, surface simplification degrees, and by inter‐ and intra‐observer differences, and compared their magnitude to true biological variation. Multiple CT‐derived surface variants of the anuran (Amphibia: Anura) pectoral girdle were generated by systematic changes in the factors that potentially influence the surface geometries. Twenty‐four landmarks were repeatedly acquired by different observers. The contribution of all factors to the total variance in the landmark data was assessed using random‐factor nested permanovas. Selected sets of Euclidean distances between landmark sets served further to compare the variance among factor levels. Landmark precision was assessed by landmark standard deviation and compared among observers and days. Results showed that all factors, except for voxel size, significantly contributed to measurement error in at least some of the analyses performed. In total, 6.75% of the variance in landmark data that mimicked a realistic biological study was caused by measurement error. In this landmark dataset, intra‐observer error was the major source of artefactual variance followed by inter‐observer error; the factor segmentation contributed < 1% and slight surface simplification had no significant effect. Inter‐observer error clearly exceeded intra‐observer error in a different landmark dataset acquired by six partly inexperienced observers. The results suggest that intra‐observer error can potentially be reduced by including a training period prior to the actual landmark acquisition task and by acquiring landmarks in as few sessions as possible. Additionally, the application of moderate and careful surface simplification and, potentially, also the use of case‐specific optimal combinations of automatic local thresholding algorithms and parameters for segmentation can help reduce intra‐observer error. If landmark data are to be acquired by several observers, it is important to ensure that all observers are consistent in landmark identification. Despite the significant amount of artefactual variance, we have shown that landmark data acquired from microCT‐derived surfaces are precise enough to study the shape of anuran pectoral girdles. Yet, a systematic assessment of measurement error is advisable for all geometric morphometric studies.

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“…Data acquired from a clinical radiological setting is actually a more accurate representation of the current population than most body donation programs since it is less affected by secular trends and age bias. Furthermore, reconstructions that are based on the CT scan data can provide a precise three-dimensional (3D) model that represents the original skeletal element [23]. However, in order for CT scans to be a feasible alternative to traditional skeletal collections, the morphological traits indicating sex also need to be accurately portrayed in the 3D reconstructions and their associated sex estimation scores need to correspond to the scores recorded on the dry skeletal element.…”

Section: Introductionmentioning

confidence: 99%

The accuracy of 3D virtual bone models of the pelvis for morphological sex estimation

et al. 2019

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It is currently unknown whether morphological sex estimation traits are accurately portrayed on virtual bone models, and this hampers the use of virtual bone models as an alternative source of contemporary skeletal reference data. This study determines whether commonly used morphological sex estimation traits can be accurately scored on virtual 3D pelvic bone elements. Twenty-seven intact cadavers from the body donation program of the Amsterdam UMC, University of Amsterdam, were CT scanned; this data was used to produce virtual bone models. Thereafter, the dry bones were obtained. Three traits by Klales (2012) and five traits from the Workshop of European Anthropologists (WEA) (1980) were scored on the virtual bone models and their dry skeletal counterparts. Intra- and inter-observer agreement and the agreement between the scores for each virtual bone model-dry bone pair were calculated using weighted Cohen’s kappa (K). For all Klales (2012) traits, intra- and inter-observer agreement was substantial to almost perfect for the virtual- and dry bones (K = 0.62–0.90). The agreement in scores in the virtual-dry bone pairs ranged from moderate to almost perfect (K = 0.58–0.82). For the WEA (1980) traits, intra-observer agreement was substantial to almost perfect (K = 0.64–0.91), but results were less unambiguous for inter-observer agreement (K = 0.24–0.88). Comparison of the scores between the virtual bone models and the dry bones yielded kappa values of 0.42–0.87. On one hand, clinical CT data is a promising source for contemporary forensic anthropological reference data, but the interchangeability of forensic anthropological methods between virtual bone models and dry skeletal elements needs to be tested further.

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The geometrical precision of virtual bone models derived from clinical computed tomography data for forensic anthropology

Cited by 42 publications

References 34 publications

Sex estimation in a contemporary Turkish population based on CT scans of the calcaneus

Sex estimation in a contemporary Turkish population based on CT scans of the calcaneus

Measurement error in μCT‐based three‐dimensional geometric morphometrics introduced by surface generation and landmark data acquisition

The accuracy of 3D virtual bone models of the pelvis for morphological sex estimation

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