Portable Tracked Ultrasound System to Monitor Spinal Curvature

Abstract

ntroduction: Adolescent idiopathic scoliosis (AIS) is the most frequent spinal deformation. It is assessed by frequent x-ray imaging, exposing patients to frequent radiation, increasing the risk of cancer. Tracked ultrasound imaging produce a three-dimensional visual of the spine without risk. We proposed using an optically tracked handheld USB Interson ultrasound probe, which is much less expensive than the current standard ultrasounds.
 Methods: A practical setup was developed for scoliosis monitoring. Reference markers were on the patient’s shoulder and the wall to account for patient motion, and simulate the plane of the x-ray detector to allow future comparisons. The optical tracker tracked the markers and ultrasound probe. This was compared to the electromagnetically tracked non-portable Ultrasonix ultrasound. Scanning captured the thoracic and lumbar regions. A three-dimensional image was composited by stacking a series of two-dimensional ultrasound slices in their tracked physical positions. To compare the two-ultrasound setups and ensure the ease of identification, a novice attempted to manually identify transverse processes. These were compared to see if all transverse processes scanned could be marked from both ultrasound setups. Two clinical experts then confirmed the markings were anatomically correct.
 Results and Conclusions: In all scans 100% of the transverse processes scanned (n = 51) were identified in Interson and Ultrasonix images. Curvatures measured using the Ultrasonix method have been previously validated to curvature measurements from x-ray images. Thus the 100% correspondence of the Interson and Ultrasonix setups indicates this inexpensive method is a promising tool to reduce radiation exposure during scoliosis monitoring.