In this study, we evaluated the accuracy, precision, and feasibility of three different 3D-photography systems. Facial 3D photography has reached a high level of accuracy and reproducibility, even with portable devices (17, 18). The results showed that the Artec Space Spider system had the lowest RMSE and the smallest MSD among the three systems tested. This is consistent with previous studies that have also found the Artec system to have high accuracy and reliability (8, 19). The Bellus3D Dental Pro application had the highest deviation from the ground truth model (MSD = 0.46 mm), which is in line with some previous studies that have reported limitations with this system (20). However, it should be noted that other studies have reported good accuracy with the Bellus3D system and they also stated that this system may provide 3D models of the face with clinically acceptable precision and reliable tools for planning surgical procedures (21, 22). Clinical studies indicate that a discrepancy in MSD of up to 2 mm for 3D facial photography is clinically acceptable (23–25). Differences in the study designs, alignment algorithm, and sample characteristics could account for the divergent findings between studies (11, 26, 27). By collecting all datasets of a test person at the same time, an influence on the part of the test person, such as weight gain or loss, hormonal, or time-of-day influences, could be excluded. However, the influence on the part of the test person by minimal mimic movements and breathing were included in the investigation. The influence of minimal movement during data collection could potentially explain the observed deviations in the measurements of the nostrils. These subtle facial movements can affect the positioning and shape of the nostrils, leading to slight differences in the recorded parameters. In comparison to investigations on static models such as a doll’s head (24, 28), this type of data collection corresponds more realistically to clinical examination conditions. Our study also found good interrater and intrarater reliability for all three parameters and for all three 3D-photography systems. This is consistent with previous studies using the same analysis algorithm (29).
Since the algorithm tries to achieve the smallest possible distance between the surface meshes during superimposition, it is possible that anatomical misclassifications occur. This source of error cannot be detected and mathematically represented using the global parameters RMSE, MSD, and HD. This problem with the use of the ICP algorithm was also shown in the study by Marliere et al. (27). Only the color-coded surface distance map provided visual information about the anatomical mapping and allowed additional verification of the anatomical correctness of the superimpositions. Our results show that the color-coded surface distance map is conclusive with the parameters RMSE, MSD, and HD.
It is worth noting that there are several factors that can affect the accuracy of 3D-photography systems, including lighting conditions, camera resolution, and surface texture of the object being scanned (18, 30). Therefore, it is important to consider these factors when choosing a 3D-photography system for a specific application. The results of our study indicate that different 3D-photography systems have varying suitability for specific clinical applications. For applications requiring the highest precision and accuracy, such as studying post-surgery facial swelling or volume changes after filler application, the Artec Space Spider system was found to be suitable. Despite its high acquisition costs (approximately €20,000), this portable device offers excellent precision. However, the ongoing costs for the annual software updates of approximately €2,000 should not be overlooked. Another aspect of the Artec Space Spider camera that must be taken into consideration is that despite its high precision and accuracy, its application is not exclusive to the medical field. This has the effect that the data are often processed in another program and thus further software licenses are necessary.
On the other hand, the Planmeca ProFace® system is particularly well-suited for soft tissue analysis or simulation in orthognathic patients. Its integration with the existing cone beam device allows for fast acquisition and easy overlay with cone beam images taken simultaneously. This makes it convenient for orthognathic surgery planning and assessment. When purchasing a new cone beam device for clinics with a high number of orthognathic surgical cases, it is worth the additional investment of approximately €4,000 for the ProFace® option. No additional software is required for the processing of the data.
For a more affordable (€40 per month) and mobile option, the Bellus3D application shows promise in everyday clinical use. It provides a simple, objective, and reproducible evaluation of soft tissue changes in terms of shape, volume, and symmetry. This makes it useful for individual planning and documentation in procedures like septorhinoplasty, mandibular reconstruction, orthognathic adjustment, and progress monitoring in cleft lip and palate patients. However, despite the detailed accuracy of the systems, the problem of simulating exact structural post-operative changes remains. The respective artificial intelligence models are still in testing phases and seem to play a central role in the future application (31, 32). When discussing the cost-effectiveness of these 3D-photography systems it is important to analyze not only the initial purchase price but also factors like software maintenance, storage, and potential long-term value in medical or dental applications.
In conclusion, our study adds to the growing body of literature on the accuracy and reliability of 3D-photography systems. While the Artec Space Spider system showed the best accuracy in our study, it is important to consider the specific requirements of a given application when choosing a 3D-photography system. Future research should continue to explore the potential of 3D-photography systems for various clinical and research applications.
Limitations
There are several limitations to this study that should be acknowledged. First, the sample size may appear relatively small, which could limit the generalizability of our results. A sample size calculation was performed before recruiting subjects. The estimated effect size was 1.33 with an α-error probability of t = 0.05, power: 0.95. The result of the minimum number of cases was eight. This shows that the selected number of cases with sufficiently good power can prove the results. Second, we only evaluated the use of 3D photography in the context of the anatomical region of the nose and did not assess its applicability in other areas of plastic and reconstructive surgery. Further we attempted to control for factors such as lighting and patient positioning, there may be other confounding factors such as the alignment algorithm that we did not account for that could affect the mathematical results of the accuracy and precision measurements. Likewise, the alignment algorithm in MeshLab. When both meshes are not of equal size, it can result in areas that cannot be properly matched or assigned. This problem is particularly evident in the marginal regions, which are not yet in the area of most interest.
Finally, the Bellus 3D Dental Pro application ceased being available for purchase since December 1st, 2021 but the reason for discontinuation of the product remains unclear. As an alternative for Bellus3D Dental Pro, the literature discusses several mobile and app solutions, including Capture, Heges, and Scandy, which utilize monoscopic photogrammetry and LiDAR technology (33). It is evident that keeping abreast of app-based solutions can be challenging, given that such solutions are often initiated by start-ups with vague survival timelines.