Local energy as a measure of back symmetry in scoliosis.

The Cobb angle has been the most commonly used method in measuring the severity of scoliosis and its progression. However, in recent years a number of researchers have chosen to monitor scoliosis by examining the severity of the surface deformity resulting from the scoliosis. Each of these approaches has been limited by errors introduced in manual location of landmarks. Scoliosis results in an asymmetry of the back. It would be very desirable to have a computer-based method of measuring this asymmetry. This paper investigates the use of wavelets and the concept of local energy to measure asymmetry associated with scoliosis. The local energy model uses wavelet theory to obtain information about shading and boundaries of objects in an image. Edges and sharp discontinuities are areas of high local energy in an image. Features such as scapular prominence, shoulder edges, waist creases and other anomalies that contribute to the scoliotic back asymmetry have high local energy. A preliminary study was completed to determine if this approach was applicable to measurement of back asymmetry. Two-dimensional local energy images were created from photographs of the backs of patients with scoliosis. The local energy was integrated across each image and a left-to right line of symmetry was calculated. This line of symmetry was then correlated with the scoliotic score developed by our group. This technique shows promise of providing an automatic method of measuring scoliosis progression.