Smartphone-based Data Acquisition Method for Modelling 3D Printed Arm Casts

Abstract

In recent years, 3D printed arm casts can replace traditional arm casts to treat bones fractures. 3D printed arm cast modelling often uses professional 3D scanning systems to capture 3D data of the arm. These systems are very expensive and may not be available in many hospitals. In order to overcome this disadvantage, inexpensive methods should be developed. This paper introduces a new data collection method based on smartphones. The photos of an arm were taken with a smartphone camera using some special techniques that could facilitate the process of image processing and 3D modelling in Agisoft Metashape and CATIA. To validate the proposed method, the photogrammetric model was compared with the scanned model (obtained by a low cost scanner) in GOM Inspect. Besides, a fit check of real 3D printed arm casts attached on the volunteer's forearm was also performed. The test results indicate that the photogrammetric model could be used as raw data for 3D arm modelling.

Accuracy of Photogrammetric Models for 3D printed Wrist-hand Orthoses

“…This could be due to noise during the image processing process caused by long, dark hair on the arm. For both cases, the range of deviations on the forearms of this study are much smaller compare to our previous study which was from -2÷2.59 mm [1]. The average deviation in the forearm part of this study is -0.04 mm for the woman's case, much smaller compared to the case (the same feature of the hair on the arm) that we reported in our previous study, where an average deviation of 0.22 mm was found [14].…”

“…In order to create 3D models of arms, Agisoft Metashape 1.8 (Agisoft LLC, Russia) was used for image processing of 2D images in this study. In the image acquisition step, the volunteers' arms were captured using a 12megapixel (MP) smartphone camera (Samsung Galaxy S10 Plus), a plastic cylinder, a light-emitting diode (LED) and some special techniques as described in our previous study [1]. Some camera parameters used are 52 mm focal length, automatic aperture, ISO number and shutter speed.…”

“…Plaster casts (for centuries) or fiberglass casts (more recently) have been used to immobilize ill or injured limbs. Nowadays, three-dimensional (3D) printed casts can be used instead of the traditional ones which have some limitations such as being heavy, uncomfortable to wear, and not waterproof,... 3D printed orthoses are more expensive than the traditional ones, but they are waterproof, custom-fit, lightweight, diverse in colour, have high aesthetics, less itching, and are removable [1].…”

“…It is evident that expert 3D scanning systems can produce very good results, but they are still costly and need highly skilled workers to operate. Reconstructing a physical object's 3D model from its 2D images is now possible with photogrammetry [1,11]. Therefore, instead of expensive 3D scanning systems, smartphone cameras and certain techniques can be used to obtain 2D images of an arm, which can then be further processed to create a CAD model of the arm [1].…”

“…Reconstructing a physical object's 3D model from its 2D images is now possible with photogrammetry [1,11]. Therefore, instead of expensive 3D scanning systems, smartphone cameras and certain techniques can be used to obtain 2D images of an arm, which can then be further processed to create a CAD model of the arm [1]. According to this study, the proposed approach can create a photogrammetric forearm model that has recognized accuracy and could be used as input data for arm cast modeling.…”