Spinal deformity measurement using a low-density flexible array ultrasound transducer : a feasibility study with phantoms

Abstract

Spinal deformities assessment using 3D ultrasound scanning has limitations in fitting onto different back surface contour as well as fitting within the gaps between subject and their spinal brace during bracing assessments. The study proposed a flexible array ultrasound transducer to overcome these limitations. The results demonstrated the feasibility of spinal deformity assessments with a flexible ultrasound array when arranged in four shapes, namely Linear, Concave, Convex, and S-shaped. For comparisons of imaging performance on spinous process using the four shapes, Convex and S-shaped transducer showed a depth dependence and lateral location dependence of the lateral intensity distribution of spinous process, respectively. S-shaped transducer had the least accurate prediction of the location of spinous process, with measurement error of 4.8 ​± ​3.2 ​mm, it also showed poorer prediction on spinal curvature measurements. This is suggested to be due to the asymmetrical distortion to the spinous process due to the lateral location dependence of the image. However, the coronal curve prediction of spine phantom performed well with R-squared values of >0.97 in all transducer shapes. The results of this study paved the way for further investigation on the improvement of image quality and measurement accuracy under different shapes for the flexible array, mechanism of dynamic shape change during the scanning to fit different body contour, as well as extension from 1D to 2D flexible array.