Flexible array ultrasound transducer for imaging of spine

Abstract

Freehand 3D ultrasound provides a reliable and radiation-free assessment of spinal deformity. However, limitations remain in the freehand 3D ultrasound operator dependence on manual scanning, loss of contact with the back of the subject during scanning in regions of large concavity in scoliosis patients, inability to fit between tight gaps between the brace and a subject's back, and lack of dynamic monitoring when changing the posture of patients. This study proposes a solution to the problems by using a flexible array ultrasound transducer to fit between tight gaps and complex body surfaces of patients. Where dynamic monitoring of spine curvature must be performed by a 2D flexible array covering the whole spine of the subject, the feasibility was first tested using 1D flexible array. Studying the feasibility of a 1D array in spinal deformity assessment would inspire and provide a foundation for the assessment method of using a 2D flexible array to investigate spinal deformities. Through investigations of the image generation method of a flexible array in different shapes and the measurement accuracy of spinous process locations, an inspired method of the shortest time-of-flight filtering method was developed to improve the accuracy of locating the bony features of the vertebra. A pure ultrasound method has also been investigated to measure the transducer shape of the flexible array by placing the transducer close to a flat scattering surface. The pure ultrasound method could reduce the need for extra components on the array for measuring its shape and curvature. Finally, a novel design of a flexible laser-generated ultrasound transducer array is proposed in this study to overcome the limitations of pitch size and inter-element spacing of piezoelectric flexible-array ultrasound transducers.