Smartphones for frugal three-dimensional scanning of the external ear with application to microtia⋆

Three-dimensional (3D) scanning, 3D modelling and 3D printing are disrupting healthcare with the potential to create personalised, automated and customised treatments that are superior to current approaches. One application of these technologies is the production of ear and facial prosthetics to restore aesthetics in the case of congenital defects, trauma and tumour resection. Several studies have recently investigated the potential of this approach to increase patient comfort and outcomes while decreasing labour time for prosthetists. One challenge with translating these new technologies to clinical use is the expensive cost of equipment and software and the additional training and skill required to use them. Recent studies have shown the potential for a scanning technique called photogrammetry to be used with smartphones in place of expensive industrial 3D scanners to acquire 3D craniofacial models of both adults1 and infants.2 Photogrammetry works by detecting common features within a series of photographs taken from different locations to compute the 3D spatial coordinates of each camera. Following this, patient's 3D surface anatomy can be calculated. Although previous studies demonstrate the ease and accessibility of scanning with smartphones, they have not quantitatively assessed the accuracy. In this short communication, we investigate the potential of low-cost devices for 3D scanning of the external ear, and provide a quantitative comparison against a metrology rated 3D scanner. It is hoped the photogrammetry approach to 3D scanning can be used to help children born with microtia, a congenital condition which affects the formation of the external ear.