Short-lag spatial coherence imaging with multi-line transmission to improve needle visibility in ultrasound images

Abstract

Ultrasound Short Lag Spatial Coherence (SLSC) imaging exploits the spatial coherence (SC) of backscattered echoes to suppress acoustic clutter and to significantly improve image contrast, particularly in difficult-to-image patients. Multi-line transmission (MLT) imaging simultaneously transmits multiple beams to increase frame rates. We hypothesize that the combination of SLSC and MLT has the potential to enhance detectability of coherent structures within a tissue background. Sector images of a 14G biopsy needle inserted within ex vivo bovine meat were acquired after implementing single-line transmission (SLT) and MLT with 4, 6, 8 and 16 simultaneous beams. The SLSC algorithm was applied to the acquired data. Results show that MLT SLSC images have a visibly darker background than SLT SLSC images, which is caused by the rapid decorrelation of the SC at short lags with MLT. This decorrelation is caused by inter-beam crosstalk interferences and can be leveraged to enhance the coherence of highly reflective targets within a tissue background, causing an increase in needle contrast from about 25 dB with SLT to ∼44 dB with 16-MLT. These results support our hypothesis that the decorrelation caused by crosstalk improves visualization of highly coherent targets within tissue, with promising applications to biopsy needle localization.