Space-time image reconstruction algorithm for diverse ultrasound transducer element distributions

The standard architecture of a medical ultrasound transducer is a linear phased array of piezoelectric elements in a compact, hand-held form. Acoustic energy not directly reflected back towards the transducer elements during a transmit-receive cycle amounts to lost information. An ultrasound imaging system currently in development seeks to maximize the collection of reflected signals with a large, flexible transducer array which conforms to contours of the subject's body, resulting in more directional look angles and an increase in received image data. However in this design, element distributions are irregular and an organized arrangement may no longer be maintained. This paper presents a versatile space-time image reconstruction algorithm designed for this system, operating in a step FMCW modality. Simulated images are included which demonstrate the algorithm's flexibility in application, and the effects of transducer aperture size and operating bandwidth on resolving capability.

1. INTRODUCTION

Medical ultrasound systems typically feature linear phased arrays within rigid, handheld transducers. Due to the relatively small contact area of these transducers, a significant portion of the echoes is not reflected back toward the array in a single scan, constituting lost imaging information. Though a full set of image data can be captured with manual rotation or translation of the transducer, a high level of operational skill is required to maximize its efficiency. A conformal transducer array-based imaging system is under development and intends to address this problem by wholly or partially wrapping around curved body surfaces to augment inward angular coverage, thereby increasing the amount of image data acquired in a single transmit-receive cycle. Its potential to provide high-quality 3D imagery while eliminating mechanical scanning may facilitate point-of-care and emergency diagnostic procedures [1], [2]. This imaging system may also be suitable for image-guided procedures such as biopsies, which are currently performed with active manual transducer repositioning.