Are different photogrammetry applications on smartphones sufficiently reliable?

This study aimed to compare the accuracy of Qlone, Magiscan, and 3dMD with that of direct anthropometry (DA).

The study involved 41 patients. Sixteen facial landmarks, including six individual and five paired points, were marked on each participant's face. Subsequently, 18 linear measurements were assessed using a 3dMD device (multicamera photogrammetry), Qlone, Magiscan smartphone applications (single-camera photogrammetry), and DA. The Qlone and Magiscan images were calibrated using a reference point 10 mm from the nasion during DA to ensure a 1:1 correspondence.

Concerning the precision of the digital methods compared to DA, the mean intraclass correlation coefficient values of 3dMD, Qlone and Magiscan were 0.989, 0.980 and 0.982, respectively. Compared with DA, 3dMD achieved excellent trueness with the lowest average absolute differences in the measurements (highest value = 0.95 ± 0.62 mm). The highest values for Qlone and Magiscan were 1.51 ± 1.11 mm and 2.14 ± 1.69 mm, respectively. According to the number of parameters, the ranking of unreliable values (> 2 mm) was Magiscan (n = 46), Qlone (n = 35), and then, 3dMD (n = 4). Furthermore, reliability (less than 1 mm) was the highest for 3dMD (n = 517), followed by Magiscan (n = 457), and then, Qlone (n = 415).

The 3dMD achieved excellent trueness with the lowest average absolute differences in the measurements. Based on statistical analysis, the trueness values of Magiscan and Qlone were close to that of 3dMD. To apply these smartphone applications clinically, more studies are necessary.