Impact of 3D surface scanning protocols on the Os coxae digital data: Implications for sex and age-at-death assessment

Abstract

The 3D imaging technologies became of paramount importance for example in disciplines such as forensic anthropology and bioarchaeology where they are being used more and more frequently.There is a number of new possibilities that they offer, for instance an easier and faster sharing of data among institutions, a possibility of permanent documentation, or new opportunities of data analysis. An important requirement, however, is whether the data obtained from different scanning devices are comparable and whether the possible varying outputs could affect further analyses, such as estimation of the biological profile. Therefore, we aimed to investigate two important questions:(1) whether 3D models acquired by two different scanning technologies (structured light and laser) are comparable and (2) whether the scanning equipment has an effect on the anthropological analyses, such as age-at-death estimation and sex assessment.3D models of ossa coxa (n=29) were acquired by laser (NextEngine) and structured light (HP 3D Structured Light Scanner PRO 2) scanners. Resulting 3D models from both scanners were subjected to age-at-death analyses (via quantitative method of Stoyanova et al., 2017) and sex analyses (via Diagnose Sexuelle Probabiliste 2 of Brůžek et al., 2017). Furthermore, high quality scans of small sample (n=5) of pubic symphyseal surface with RedLux Profiler device were acquired as reference surfaces to which the outputs from both scanners were compared. Small deviations between surfaces were more evident in more rugged surfaces (in areas of depression and protrusion). Even though small differences from the reference surfaces were found they did not have significant effect on age and sex estimates. It never resulted in opposite sex assignment and no significant differences were observed between age estimates (with the exception of TPS/BE model).

Forensic age estimation: comparison and validation of the Iscan method in 3D reconstructions using a surface scanner in a Spanish population

“…Several factors may account for this inter-observer variation: firstly, the important morphological variety that exists in any age range; secondly, because the traits analysed at each phase undergo extremely diverse changes according to the physiological process of skeletal ageing (typically, these characteristics overlap and feature in more than one phase, since the categories are not discrete and watertight, but rather a continuum in transition [ 25 ]); and finally, because interpersonal differences in the perception of morphological traits and the interpretation of phase descriptions should be considered [ 20 , 21 ]. Faced with a similar phenomenon, Mullins et al [ 60 ] and Koterova et al [ 49 ] stated that significant inter-observer differences do not necessarily have to affect the estimates or the applicability of the data, especially when high degrees of concordance and percentages of agreement are obtained in all the estimates. It should also be noted that this is the first study to apply the Iscan method in 3D reconstructions obtained using a structured light surface scanner in a Spanish population.…”

“…In addition, this system has been used for several years now to determine sex or age in a biological profile, comparing different models and technologies to maximize their results. Thus, 3D models provide additional opportunities for data analysis using new variables, such as surface areas, volumes, contours, surface relief, and semi-landmarks [ 48 , 49 ]. However, its application in the creation of 3D images of ribs has not been described to date.…”

The Application of Forensic Imaging to Sex Estimation: Focus on Skull and Pelvic Structures

“…Despite the fact that relevant studies [57][58][59] on 3D surface scanning of skulls do not reflect its specific application to sex estimation, its strong metric analysis ability and high reproducibility advocate a high potential of this method to serve as an optional method for sex estimation based on skull structure when the complex CT imaging facility is not available. Other evidence [40,60,61] demonstrates the feasibility of using 3D surface imaging in sex estimation based on the pelvic structure, with high accuracy when employing CNN in the non-metric examination. At the current stage, only the reliability of the 3D surface scanning method in the metric analysis is promising due to the lack of reported accuracy.…”

“…To examine the accuracy of 3D surface scanning combined with CT imaging trained and tested CNN models, the same research group [41] used a handheld 3D surface scanner to scan 105 real pelvises and the accuracy of 3D surface scanning combined with CT imaging (focusing on VP, DP and GSN) trained and validated CNN models; the results obtained satisfactory accuracies above 95% on the VP and DP images compared to the GSN with 73.3% [60]. Two surface scanning devices, the laser scanner NextEngine 3D Ultra HD and the HP 3D Structured Light Scanner PRO S2 were used on os coxae to estimate the sex via DSP; although the structured light technology seemed to be more accurate than the laser technology due to it captures slightly more detail, there was not a significant effect on the estimate of the sex under optimal scanning settings [61]. A subsample of 39 pelvises was 3D surface scanned to compare observations with dry bone and CT data in the previously mentioned non-metric and metric study [40]; the 3D surface scan and CT comparison yielded a higher agreement than the 3D surface scan and dry bone comparison and CT and dry bone comparison.…”