Novel Radiation-Free Assessment of Scoliosis and the Cobb Angle
Scoliosis and Curve Evaluation
Scoliosis is a medical term meaning an abnormal curvature of the spine. This disease may develop during childhood and causes the spine to curve to the left or right (Figure 1).
Figure 1. Scoliosis
The Problem: Radiation Exposure
The diagnosis of scoliosis in children and adolescents requires the use of full spinal x-rays on which the Cobb angle is measured.
The phrase full spinal x-rays means the child's entire spine is x-rayed while standing - from the first cervical vertebral in the neck (abbreviated C1) to the pelvic area or sacrum (S1).
Geometric calculations are used to determine the angle of the scoliotic curve. This angle is called the Cobb angle. The Cobb angle measurement is the 'gold standard' of scoliosis evaluation endorsed by the Scoliosis Research Society (SRS). Until recently, follow-up of adolescent scoliosis patients and particularly evaluation of the treatment prescribed (either bracing or surgery) relied heavily on full spinal x-rays on which the Cobb angle is measured.
Growing patients with scoliosis that are at risk for curve progression may be x-rayed up to 4-5 times per year for a total period of 3-5 years. The patient's curve progression is closely followed until the curve stops; called curve stabilization. In scoliotic patients that need to undergo corrective surgery, x-rays are obtained for an even longer time. This may amount to a significant dose of radiation.
The exposure to radiation in these patients takes place during a critical period of growth that may increase the risk of radiation. For this reason, adolescents with scoliosis are exposed to multiple diagnostic x-rays when the growing breast tissue, thyroid or other tissues may be highly sensitive to the cancerous effects of radiation. It is not surprising therefore that higher incidence of breast cancer (1), thyroid cancer and leukemia have been reported in scoliosis patients who undergo multiple full spinal x-rays (2).
Reducing Radiation Dose
One effective way to reduce radiation exposure in scoliotic patients is to obtain the spinal x-rays from the rear of the body (called PA or postero-anterior) instead of from the front (called AP or antero-posterior). This will reduce the risk of developing cancer from one-half to three-quarters (3).
Other recommendations to reduce the radiation dose include limiting the number of x-rays to one PA view, properly aiming the x-ray beam to the target (a process called collimation), shielding the patient with a lead apron (to the extent possible), and reducing repeat x-rays due to poor image quality.
Some investigators have proposed the use of a specially designed MRI for the purpose of scoliosis follow-up (4); however this technique may be too expensive.
Ortelius800® - A Radiation-Free Cobb Angle Measurement
Recently, a new non-invasive radiation-free three-dimensional (3-D) imaging system for the diagnosis and monitoring of scoliosis and other spinal deformities has been developed (Ortelius800®, Figure 2). This new device uses a low intensity electromagnetic field to record the positions in space of the patient's spinous processes. The spinous processes are the bony spinal projections that can be felt beneath the skin.
Figure 2. Ortelius800®
A sensor is attached to the examiner's finger. The low intensity electromagnetic field records the location of the patient's spinous processes as the examiner feels (palpates) the spine (Figure 3). The entire examination is completed in a matter of a few minutes and can be performed by a nurse, physiotherapist or the managing medical doctor.
Figure 3. Practitioner examines a patient?s spine using the Ortelius800® System.
As the spinal examination takes place, the recorded data is simultaneously displayed on the Ortelius® screen. Upon completion of the examination, the system instantaneously creates a graphical reconstruction of the spine, displaying the calculated angle of deformity (Cobb angle), difference in leg length (left/right), and additional data on the patient's body balance (Figure 4a-c).
AP x-ray of C1-S1 and Cobb angle measurements.
Cobb angle measurements obtained using the Ortelius800®.
Graphical reconstruction of the patient?s spine.
The image on the left is a PA view and the right side is a lateral (side) view.
Patient Follow-Up Using the Ortelius800®
Follow-up of scoliotic patients using the Ortelius800® provides the managing spine specialist with a radiation-free accurate Cobb angle measurement. Although there is still need to obtain an initial standing full spinal x-ray, the Ortelius800® can cut down the number of x-rays needed. Further, the system provides additional information about the body's balance and biomechanics of the spinal deformity in 3-D.
Ortelius800® has been approved by the US Food and Drug Administration (FDA) and has received the European CE certification.
1. Doody M, Lonstein JE, Stovall M, Hacker DG, Luckyanov N, Land CE. Breast cancer mortality after diagnostic radiography: findings from the U.S. Scoliosis Cohort Study. Spine 25:2052-63, 2000.
2. Rao, PS, Gregg EC. A revised estimate of the risk of carcinogenesis from x-rays to scoliosis patients. Invest Radiol 19:58-60, 1984.
3. Levy AR, Goldberg MS, Mayo NE, Hanely JA, Poitras B. Reducing the lifetime risk of cancer from spinal radiographs among people with adolescent idiopathic scoliosis. Spine 21:1540-48, 1996.
4. Schmitz A, Jaeger UE, Koening R, KandybaJ, Wagner UA, Giesecke J, Schmitt O. A new MRI technique for imaging scoliosis in the sagittal plane. Europ Spine J 114-7, 2001.