Semi-automatic Measurement of Scoliotic Angle Using a Freehand 3-D Ultrasound System Scolioscan

Abstract

Ultrasound volume projection imaging (VPI), developed with free-hand 3-D ultrasound system, has been advanced to assess scoliosis, a medical condition defined as lateral spine curvature > 10°. Ultrasound VPI provides a coronal view of spine for manual measurement of spine curvature, achieving a performance comparable to the standard posteroanterior standing radiograph. However, the subjective manual measurements still restricted its wider applications in the diagnosis of scoliosis. In this study, we proposed a semi-automatic method to assess the spine curvature by using the polynomial curve fitting to the manual input curve points perceived on the spinous column profile in VPI images obtained from the Scolioscan, a freehand 3-D ultrasound system. The spine curvature angle was automatically calculated according to the inflection points on the curve. Totally 70 subjects (age: 15.9 ± 2.7 years) with different degrees of scoliosis were recruited to evaluate the performance of proposed semi-automatic measurement method. The curvatures obtained using the semi-automatic method had a signifi- cant correlation with those by the manual method (slope = 0.96, r = 0.9; p < 0.001). The proposed semi-automatic framework is capable of measuring the spine curvature based on the coronal images obtained with free-hand 3-D ultrasound system, expediting the application of Scolioscan in scoliosis diagnosis.