Rasterstereography: Radiation - Free Technology for the Analysis of the Spine and Pelvis
by Jean Pierre Gibeault, P: eng.
RECENTLY IN THE LITERATURE: In a recent study, researchers demonstrated an excellent correlation between X-ray measurements and measurements made with rasterstereography (Schulte 2008). Schulte, et al., produced rasterstereographs and compared them to digitized A-P radiographs of the same 16 patients with idiopathic scoliosis. In this longitudinal study design, with a mean follow-up period of 8 years (range 3 to 10 yrs.), lateral vertebral deviation and vertebral rotation were measured between C7 and L4. This study design mimics actual clinical environments and, therefore, provides invaluable data to the clinician. During the 10 year time frame, Cobb angle measurements increased on average by 13 degrees. The study showed an excellent correlation between rasterstereographic and radiographic progression. The mean difference between rasterstereographs and radiographs was 3.21 mm for lateral vertebral deviation and 2.45 degrees for vertebral rotation. In conclusion, using the parameters of lateral vertebral deviation and vertebral rotation, rasterstereography accurately refl ects the radiograph measured progression of idiopathic scoliosis during the long-term follow-up. The authors do comment that the parameters used are not directly comparable with the Cobb angle. However, they recommend a rasterstereographic examination every 3 to 6 months and a radiographic examination every 12 to 18 months, provided that rasterstereography does not show rapid deterioration of the scoliosis. If this result is reproducible, patients and practitioners alike will want to change the way conditions, such as scoliosis and other global postural distortions are managed. Further studies confi rming the high accuracy of this technology can be found on both normal populations (Hackenberg 2003), as well as those with rotational scoliosis (Drerup 1997). With respect to these studies, it is reasonable to say, rasterstereographs can signifi - cantly reduce the amount of X-rays needed, without sacrifi cing clinical data. In fact, the sophistication of rasterstereography today affords the practitioner a cornucopia of postural information, well beyond what is possible with plain fi lm projections alone. Of course, X-rays do provide unique information about bone and soft-tissue that cannot be gleaned from any other source and, because of this, I believe that both will be a necessary part of chiropractic practice in the future. The Diers Formetric produces the rasterstereographs using an optical light scanner and computer software which automatically fi nds anatomical landmarks without markers or user placement. Thousands of images are taken over an adjustable time frame, which provides information for the quantifi cation of sway patterns, breathing tendencies, weight distribution, and a 3-D computer generated representation of the spine and pelvis. Although not as breakthrough, rasterstereography equipment available in the United States also offers range of motion analysis, cervical spine imaging, and a dynamic forceplate which can invert, dorsifl ex, plantarfl ex and elevate one foot at a time. This is particularly useful when assessing the effects of an orthotic or shoe lift on pelvic and spinal alignment. Rasterstereography is not new; Stokes and Moreland utilized the same technology twenty years ago (Stokes, et al., 1987) when they evaluated for changes in rib hump in seated, standing and forward bending postures.