The Validity and Reliability of TrueDepth Camera Embedded in the Phone for Foot Measurement

There are several laser or structured-light based foot scanners available on the market, which can be used to obtain accurate 3D foot models. Compared to those 3D scanning devices, TrueDepth cameras are portable, inexpensive and easy-to-use. However, the accuracy and reliability of their 3D foot scanning remain to be confirmed. This study aimed to verify the validity and reliability of structured light TrueDepth camera integrated into the mobile phone when it is used for foot measurement. Thirteen students without any kinds of foot abnormalities or foot diseases were recruited and their feet were measured by both Infoot 3D foot scanner and mobile phone with TrueDepth camera. Three parameters were measured including foot length, foot breadth and ball girth. Subsequently, the reliability and validity of the two methods were assessed by linear regression analyses, intraclass Correlation Coefficient and Bland-Altman analysis. The foot breadth and girth circumference measurements all showed high coefficients of determination (R2>0.8) between the two methods and three measurements indicated good to excellent agreements (ICCs>0.9), although the length measurement was reported without significant coefficients of determination. Further, findings from Bland-Altman analysis demonstrated that the measurements from the TrueDepth camera had good agreements with those from Infoot and they could be used interchangeably. However, with the reconstruction algorithm updating in the near future, we could foresee the promotion in foot length measurement when using the TrueDepth camera from the phone. The TrueDepth camera utilizing structured-light and the customized application for foot measurement has fast, accurate and low-cost features and it is a convenient and economical method to obtain the foot 3D model. It can be widely applied for medical purposes and customization.