Contactless head posture measurement

Abstract

In this paper we describe new advanced contactless method for the precise posture head measurement using digital cameras. Objective was to develop a technique for measurement of the native position of the head in 3D space. The technique was supposed to determine differences between anatomical coordinate system and physical coordinate system. Similar technique has not been developed up to this time such that it could be widely and easily used in neurological clinical practice although it could have an important use in this field because there are a lot of neurological disorders that affect postural alignment position of head. The frontal photograph is used to evaluate the coronal head tilt (inclination). A digital camera is situated on a (tripod) special stand so that its position corresponds to the physical horizontal. The anatomical horizontal can be defined by the following ways: If the measured subject does not suffer from an eye disorder that affects position of eyes, the connecting line between eye pupils can then be considered as anatomical horizontal. These points are designated by white rounded marks. The same method is used for evaluating the tilt in sagittal plane (flexion) using a profile photograph. The flexion value is measured relatively as the inclination of the connecting line between tragus and exterior eye corner. The circumvolution extent (rotation) of the head is evaluated from the difference between tragus coordinates in the left-profile and right-profile image. These images are captured at the same time using two cameras and the cameras are situated on the same optical axis which is parallel with the frontal plane of subject. This is achieved by attaching specially designed devices on stand. These devices allow the cameras to be set on the same axis using laser beam. The whole configuration is placed on an axis designated on the floor, or on the special mat. There was experimentally checked that the accuracy of this method in order of tenths of degrees and therefore this method satisfies the general physicians’ requirements for the accuracy of the measurement about 1-2°.

Later, another method is introduced. It studies the use of two digital video cameras and searches new possibilities. In the end, a marker-less method is proposed and further works are expected.