Accuracy and precision of the three-dimensional assessment of the facial surface using a 3-D laser scanner

Abstract

Three-dimensional (3-D) recording of the surface of the human body or anatomical areas has gained importance in many medical specialties. Thus, it is important to determine scanner precision and accuracy in defined medical applications and to establish standards for the recording procedure. Here we evaluated the precision and accuracy of 3-D assessment of the facial area with the Minolta Vivid 910 3D Laser Scanner. We also investigated the influence of factors related to the recording procedure and the processing of scanner data on final results. These factors include lighting, alignment of scanner and object, the examiner, and the software used to convert measurements into virtual images. To assess scanner accuracy, we compared scanner data to those obtained by manual measurements on a dummy. Less than 7% of all results with the scanner method were outside a range of error of 2 mm when compared to corresponding reference measurements. Accuracy, thus, proved to be good enough to satisfy requirements for numerous clinical applications. Moreover, the experiments completed with the dummy yielded valuable information for optimizing recording parameters for best results. Thus, under defined conditions, precision and accuracy of surface models of the human face recorded with the Minolta Vivid 910 3D Scanner presumably can also be enhanced. Future studies will involve verification of our findings using test persons. The current findings indicate that the Minolta Vivid 910 3D Scanner might be used with benefit in medicine when recording the 3-D surface structures of the face.

Evaluation of Precision and Accuracy Assessment of Different 3-D Surface Imaging Systems for Biomedical Purposes

“…The ideal scanner should feature both: high accuracy and precision. Studies evaluating scanners in medicine have mostly investigated one special anatomical area with a particular scanner and found accuracy and precision of the 3-D devices reasonable enough to recommend them for clinical application without investigating if the specific scanning systems or maybe a different device is best suited for the anatomical region of interest [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. Our study, testing various scanners based on different technologies on three different kinds of complex surfaces for the first time, is able to corroborate these findings.…”

“…The sheep skulls have been chosen as research object because manual distance measurements between well-established anatomical landmarks has been approved and validated in our previous study [20]. With human subjects, reliable measurements exploring limitations in accuracy and precision of the systems would have hardly been possible, given a substantial amount of variables that cannot be standardized, such as skin translucency, reflectivity, colour or artifacts caused by movement [13][14][15][16][17][18]. So far, a number of publications used single scanners for anthropometric measurements or clinical studies of individual body regions [21][22][23][24][25][26].…”

“…When comparing scanner results with an established reference method (e.g. manual measurements), distinction has to be made between accuracy and precision and should be considered independently [13][14][15]. The term accuracy describes how close results come in numerical terms to the reference method; precision gives the amount of variation or "scattering" of the results around a given reference.…”

“…Therefore, the sheep skull values should be taken as examples of a rough sensor performance overview achieved under normal clinical conditions by an experienced medical staff and not as the real precision or accuracy values documented by the manufacturer. According to our previous studies which showed that landmark positioning on 3-D models are sufficiently precise and accurate, resulting in observer independent, reproducible measurements [3, 13-15, 20, 25] by also analysing the influence of various experimental conditions (as lighting and number of scanners, alignment of laser stripe light and number of scanner shots, angle of recording, position of the region of interest during acquisition, premarking of anatomical landmarks) on the precision and accuracy of 3-D measurements [13][14][15], the presented study abstains from further intraand inter-observer variability analysis regarding measurement precision and accuracy. Furthermore, as manual measurements are currently still applied in all day clinical routine as the standard reference method, the presented study used these manual measurements as the reference method for precision and accuracy assessments.…”

“…In the medical field, the established technology met new challenges: different anatomical regions of the human body feature structures of varying complexity. Therefore, standardization and validation studies of 3-D surface assessment were performed for different anatomical regions in previous studies [12][13][14][15], but comparison of different scanning systems for varying anatomical complexity are still lacking and limits characterization of medical application fields for specific 3-D scanning systems [16][17][18]. The fragmentary nature of the existing evidence and the fact that so far scanners have been tested mostly in small clinical series rather than in systematic and standardized studies, hinder assessment and further clinical dissemination [19].…”