Reply to letter to the editor: “The iPad/iPhone 3D photography app—a promising device, but how about its accuracy?”

We are happy to find your readers showed interest in our previous work entitled “Three-dimensional facial scanner in the hands of patients: validation of a novel application on iPad/iPhone for three-dimensional imaging” and left some valuable comments about it in a letter (1,2). By writing this response letter, the authors would like to thank them for their interest and discuss some important points they raised in their letter.

Firstly, in the letter, Fan et al. kindly suggested using 3D images as the gold standard. Admittedly, a number of 3D imaging systems have been validated to have good accuracy, and direct measurement using caliper is time-consuming. However, measuring on a virtual model generated by a 3D imaging system is always an indirect method. The authors believe that the gold standard should be the measurement directly taken on subjects in the real world to avoid any possible distortion during imaging, and this is what many investigators did in their studies (3-5). Involuntary movement and soft tissue deformation are two major concerns in direct measurement. To address these problems, we recently consider the possibility of doing direct measurement on mannequin heads.

Secondly, Vectra H2 is now available as the new generation of portable 3D imaging system. Accuracy study using Vectra H2 is necessary to make sure the new device is qualified in different patient populations. It is good advice to compare our novel imaging system with this new commercial device.

Thirdly, the validation study aimed to test the accuracy of this novel imaging system in the entire face (1). There were two standards in choosing parameters. In the first place, they should be commonly-used parameters that cover the periorbital region, nasal region, and orolabial region; secondly, the parameters should include horizontal distances, vertical distances, and sagittal distances. Fan et al. put a good point that the novel system should undergo a more detailed validation study in the periorbital region (2). Further study using more specific periorbital landmarks will be conducted in the future.

3D imaging and stereophotography-based anthropometric measurements are important for the clinical practice of many departments. Improving the accuracy and portability of 3D scanners should always be a goal for researchers in this field. Hopefully, 3D imaging technology will continue to advance in the future.

Acknowledgments

Funding: This study was supported by National Key R&D Program of China (No. 2020YFE0201600) and Medical Science and Health Technology Innovation Project (No. 2021-I2M-1-003).

Footnote

Provenance and Peer Review: This article was commissioned by the editorial office, Annals of Translational Medicine. The article did not undergo external peer review.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://atm.amegroups.com/article/view/10.21037/atm-22-1324/coif). The authors have no conflicts of interest to declare.

Ethical Statement:The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Chong Y, Liu X, Shi M, et al. Three-dimensional facial scanner in the hands of patients: validation of a novel application on iPad/iPhone for three-dimensional imaging. Ann Transl Med 2021;9:1115. [Crossref] [PubMed]
2. Fan W, Rokohl AC, Guo Y, et al. The iPad/iPhone 3D photography app—a promising device, but how about its accuracy? Ann Transl Med 2022;10:649.
3. Weinberg SM, Naidoo S, Govier DP, et al. Anthropometric precision and accuracy of digital three-dimensional photogrammetry: comparing the Genex and 3dMD imaging systems with one another and with direct anthropometry. J Craniofac Surg 2006;17:477-83. [Crossref] [PubMed]
4. Dindaroğlu F, Kutlu P, Duran GS, et al. Accuracy and reliability of 3D stereophotogrammetry: A comparison to direct anthropometry and 2D photogrammetry. Angle Orthod 2016;86:487-94. [Crossref] [PubMed]
5. Othman SA, Saffai L, Wan Hassan WN. Validity and reproducibility of the 3D VECTRA photogrammetric surface imaging system for the maxillofacial anthropometric measurement on cleft patients. Clin Oral Investig 2020;24:2853-66. [Crossref] [PubMed]