University of Ljubljana, Faculty of Mechanical Engineering, Aškerčeva 6, Ljubljana 1000, Slovenia.
Biomed Eng Online. 2013 Sep 26;12:96. doi: 10.1186/1475-925X-12-96.
Knowing the orientation of the head is important in many fields, including medicine. Many methods and measuring systems exist, but usually they use different markers or sensors attached to the subject's head for head orientation determination. In certain applications these attachments may represent a burden or a distraction to the subject under study which may have an unfavourable impact on the measurement. We propose a non-contact optical method for head-to-trunk orientation measurement that does not require any attachments to the subject under study.
An innovative handheld 3D apparatus has been developed for non-invasive and fast 3D shape measurements. It is based on the triangulation principle in combination with fringe projection. The shape of the subject's upper trunk and head is reconstructed from a single image using the Fourier transform profilometry method. Two shape measurements are required to determine the head-to-trunk orientation angles: one in the reference (neutral) position and the other one in the position of interest. The algorithm for the head-to-trunk orientation angle extraction is based on the separate alignment of the shape of the subject's upper trunk and head against the corresponding shape in the reference pose. Single factor analysis of variance (ANOVA) was used for statistical characterisation of the method precision.
The method and the 3D apparatus were verified in-vitro using a mannequin and a reference orientation tracker. The uncertainty of the calculated orientation was 2°. During the in-vivo test with a human subject diagnosed with cervical dystonia (aged 60), the repeatability of the measurements was 3°. In-vitro and in-vivo comparison was done on the basis of an experiment with the mannequin and a healthy male (aged 29). These results show that only the difference between flexion/extension measured angles was statistically significant. The differences between means were less than 1° for all ranges.
The new non-contact method enables the compensation of the movement of the measuring instrument or the subject's body as a whole, is non-invasive, requires little additional equipment and causes little stress for the subject and operator. We find that it is appropriate for measurements of the head orientation with respect to the trunk for the characterization of the cervical dystonia.
在许多领域，包括医学领域，了解头部的朝向都很重要。目前有许多方法和测量系统，但它们通常使用不同的标记或传感器来确定头部的朝向。在某些应用中，这些附件可能会给被试者带来负担或干扰，从而对测量结果产生不利影响。我们提出了一种非接触式光学方法，用于测量头部与躯干的相对位置，该方法不需要在被试者身上附加任何附件。
我们开发了一种创新的手持式 3D 仪器，用于进行非侵入式和快速的 3D 形状测量。它基于三角测量原理，结合了条纹投影技术。傅里叶变换轮廓术方法用于从单个图像重建被试者上躯干和头部的形状。为了确定头部与躯干的相对位置角度，需要进行两次形状测量：一次在参考（中立）位置，另一次在感兴趣的位置。头部与躯干相对位置角度的提取算法基于单独对齐被试者上躯干和头部的形状与参考姿势中的相应形状。采用单因素方差分析（ANOVA）对方法的精度进行统计学描述。
我们使用人体模型和参考方向跟踪器对该方法和 3D 仪器进行了体外验证。计算得到的方向不确定度为 2°。在对一名患有颈性肌张力障碍（60 岁）的人类被试者进行的体内测试中，测量的重复性为 3°。在基于人体模型和一名健康男性（29 岁）的实验进行的体外和体内比较中，仅在测量的屈伸角度之间存在统计学意义上的差异。所有范围内的平均值差异均小于 1°。
新的非接触式方法能够补偿测量仪器或被试者身体的整体运动，具有非侵入性、所需附加设备少且对被试者和操作者的压力小等优点。我们发现，该方法适用于颈性肌张力障碍的头部相对于躯干的位置测量。
