Rasterstereography Radiation-free technology for spine and pelvis analysis fter more than 20 years of research in Europe, the technology of body surface mea- surement by rasterstereography, combined with biomechanical modelling techniques, has produced a device for the fast, radiation-free evaluation and analysis of the spine and pelvis. This German device is used by universities and research clinics. It has also been utilized in, primarily private, chiropractic, orthopedic and dental clinics for diagnostics and for specifi c and interdisciplinary therapies. With the fi rst units produced for commercial use in 1996, this technology is now in its fourth generation. Four hundred and ninety units have been produced commercially and most of these are used in Germany. The high accuracy of this technology, used on scoliosis patients, was clinically confi rmed by Drerup et al (1997) and compared with customary thorax radiographs by Hackenberg et al (2003). A ORIGIN AND SCIENTIFIC FOUNDATION OF THIS TECHNOLOGY The aspects of spinal deformity that have been researched extensively at many universities and research centres are the shape of the back, shape analysis of the body surface and techniques of body surface measurements. The objective driving this research in its early days – around 1980 – was to develop tech- nologies and devices that would be complementary to radiology for the evaluation and moni- toring of patients suffering from idiopathic scoliosis. The need for frequent follow-up evalua- tions during therapy, and the necessity to greatly reduce the overall radiation load during the duration of the therapy, were strong motivators to develop accurate and reliable devices. Among many research centres, the Institute for Experimental Biomechanics and the Uni- versity Orthopedic Clinic at the University of Münster in Germany continuously develop a large body of research in this area. Research papers have been – and still are – produced by many of their professors, researchers and doctoral students. AN OPTICAL SYSTEM FOR SPINAL AND PELVIS ANALYSIS One of the ways to meet the objective of developing a radiation-free, fast, contactless and reliable device to complement X-ray measurement systems is to use the combination of 3-D-shape measurements and biomechanical modelling to reconstruct and display the spine structure and calculate the key spinal and pelvic parameters. (Figures 1 and 2, page 46) Jean-Pierre Gibeault, PEng, is the founder and CEO of Biome- trix Medica. He graduated from Queen’s University with a degree in electrical engineering and has been involved in scientific instru- mentation throughout his career. Headquartered in Canada, his companies deliver medical products and equipment in the Americas and Scandinavia. 32 • CANADIAN CHIROPRACTOR |FEBRUARY 2008 CAPTURING AND MEASURING THE DORSAL PROFILE (BACK SHAPE) White Light Raster Line Triangulation (WLRT) enables the scanning of objects in 3-D by projecting raster lines on their surfaces and by capturing these lines under a known and fixed angle with a camera. (Figure 3) Based on triangulation algorithms, spatial co-ordinates of all raster points are calculated, resulting in a dense point cloud of randomly distributed points describing the measured surface. These data points are transformed to a regular grid by using interpolation, which will simplify further calculations. In this way the system captures and analyzes a body shape, statically or dynamically. Rasterstereography excels by its high precision – error margin ≤ 0.1mm – and allows a radiation-free representation of the profile. The speed of the measurement is fast at 0.04 sec- onds and the total dorsal surface is registered simultaneously. The recognition of the anatomical structure through the automatic identifi cation of ana- tomical landmarks on the body surface provides the basis for a reconstruction of the 3-D profi le of the dorsal surface. MATHEMATICAL CONSTRUCTION AND DISPLAY OF THE SPINE STRUCTURE The aim of capturing, measuring and analyzing the dorsal surface – back shape – is to obtain information about the 3-D shape of the vertebral column. It is well documented that the vertebral rotation is correlated to the surface rotation and this allows us to establish the relationship between the back shape and the shape of the spinal midline. In our case, the surface rotation is measured by the angle of the surface normal, or www.canadianchiropractor.ca feature
Chiropractic + Naturopathic Doctor March 20008: Page 32
