Laser Based Spatial Spine Curve Determination in Scoliosis Primož POREDOŠ* 1 , Dušan ČELAN 2 , Janez MOŽINA 1 , Matija JEZERŠEK 1 1 University of Ljubljana, Faculty of Mechanical Engineering, Ljubljana, Slovenia; 2 University Medical Centre Maribor, Maribor, Slovenia http://dx.doi.org/10.15221/14.115 Abstract We present the development of a novel method for the automatic determination of a spatial spine curve based on the measured 3D shape of the human back (automatic curve) with the 3D laser profilometer. The measuring system is based on a line laser triangulation, its measuring range at the distance of 1 m is 300×700×500 mm, the measurement takes about 10 seconds and the single point measurement accuracy is 0.1 mm. The method allows us to compare an automatically determined spatial spine curve with a spatial curve, determined by the physician (reference curve) with the method of root mean square deviation (RMSD) in the frontal and sagittal plane. To validate the method both automatic and reference curve were compared on one subject in three different upright postures with arms in positions: 1. arms released beside the body, 2. upper arm in the horizontal position and forearm in vertical position upwards, 3. arms vertically at full stretch upwards. The results showed that the repeatability of the presented method for all three postures in the frontal and sagittal planes was 0.9 mm and 0.2 mm, respectively, thus allowing to assess a valid quantitative analysis of spine curve course on the surface of the human back regardless of the human upright posture. Keywords: Laser profilometry, 3D, back shape analysis, scoliosis, spatial spine curve, repeatability 1. Introduction Laser measuring systems are becoming more and more widespread in industry and medicine. Especially in medicine, the occurrence of advanced therapies increases the need for non-contact, mobile, robust, accurate, effective and non-invasive measuring systems, which present minimal level of psychophysical stress for the patient [1, 2]. This kind of metrology promises a possible avoidance of using invasive radiographic imaging methods, such as magnetic resonance imaging (MRI) and radiography (X-rays, CT). Currently, in modern medical practice there are often used numerous invasive and demanding psychophysical diagnostics [3-5]. As a result of the aforementioned disadvantages, we present a method that has a possibility of non-contact, accurate, quick and non-invasive 3D image acquisition of the human torsos with developed scoliosis as well as evaluation of the patient's body posture with the custom designed software. Incorrect posture is one of the reasons for a number of pathological conditions, for example scoliosis [6]. It is an abnormal 3D curvature of the vertebral column, manifested by elemental deformities in the three main anatomical planes: lateral curvature in frontal, anteroposterior deviation in sagittal, and vertebral axial rotation in the transverse plane [7, 8]. During human evolution the upright posture required adjustments of the spine, which is why the so-called double “S” shaped sagittal curvatures have developed. An anatomical expression of the curvatures is just one of the measures for a correct body posture in clinical assessment [9]. Physicians often try to determine the expression of the curvatures, which is often prone to subjective judgment of the particular physician. In addition to clinical assessments it is also important to quantitatively assess the curvatures using one of the imaging methods. For instance, radiographic imaging method is most accurate though, but it is known to be harmful to patients due to its cumulative effect of ionizing radiation [10]. Moreover, the MRI imaging method despite its accuracy is known to be expensive and hardly available [11]. Consequently, much efforts have been focused on alternative measuring methods for the spine curvatures assessment. A vast number of torso surface measurement methods are used in clinical assessment, most commonly mechanical methods such as the DeBrunner kyphometer [12], “Flexicurve ruler” [13], Gravity goniometer or inclinometer [14] and Myrin inclinometer [15], and optical imaging methods such as raster stereography [16], Moiré topography [17] and laser triangulation [7]. The latter method, which was used in the research presented in this paper, presents a completely non-invasive way of 2D and 3D acquisition of the patient’s back and further analysis of the 3D surface of the body. Thus, we propose a new, noninvasive and quick method for the automatic spatial determination of the spine curve of thoracic and lumbar spine based on the 3D shape measurement of the human torsos with developed scoliosis. Special emphasis in this paper is placed firstly on validation of the presented method by manual determination of the spine curve, and secondly on repeatability assessment of three different human upright postures * primoz.poredos@fs.uni-lj.si; +386 1 4771 170; http://lab.fs.uni-lj.si/kolt 5th International Conference on 3D Body Scanning Technologies, Lugano, Switzerland, 21-22 October 2014 - 115 -