Multiview spatial compounding using lens-based photoacoustic imaging system

Abstract

Recently, an acoustic lens has been proposed for volumetric focusing as an alternative to conventional reconstruction algorithms in Photoacoustic (PA) Imaging. Acoustic lens can significantly reduce computational complexity and facilitate the implementation of real-time and cost-effective systems. However, due to the fixed focal length of the lens, the Point Spread Function (PSF) of the imaging system varies spatially. Furthermore, the PSF is asymmetric, with the lateral resolution being lower than the axial resolution. For many medical applications, such as in vivo thyroid, breast and small animal imaging, multiple views of the target tissue at varying angles are possible. This can be exploited to reduce the asymmetry and spatial variation of system the PSF with simple spatial compounding. In this article, we present a formulation and experimental evaluation of this technique. PSF improvement in terms of resolution and Signal to Noise Ratio (SNR) with the proposed spatial compounding is evaluated through simulation. Overall image quality improvement is demonstrated with experiments on phantom and ex vivo tissue. When multiple views are not possible, an alternative residual refocusing algorithm is proposed. The performances of these two methods, both separately and in conjunction, are compared and their practical implications are discussed.

Photoacoustic imaging in percutaneous radiofrequency ablation: device guidance and ablation visualization

“…This can be rectified to a large extent by using spatial compounding of B-mode images obtained by steering the beam at different angles. However, in this study, we prefer to use a B-mode image without spatial compounding for the ease of combined PA and US imaging [43]. In all the experiments the RFA tines (not the trocar) were coated to improve absorption.…”

Tomographic imaging with an ultrasound and LED-based photoacoustic system

“…Multi-angle spatial compounding has been used to form tomographic PA and US images [25]. As shown in the configuration (Fig.…”

“…[10,23] developed a multi-view Hilbert transform for the circular scanning configuration using a linear array and showed resolution improvement with this approach. Imaging quality improvement based on resolution, signal to noise ratio (SNR) and contrast was also studied for linear array-based tomographic imaging [24,25]. The above-mentioned advantages are associated with tomographic imaging with the long axis of the transducer array rotating around the target, where all the angular views are imaging the same plane and the focusing of the transducer is advantageous to eliminate out-of-plane artifacts.…”

Tomographic Ultrasound and LED-Based Photoacoustic System for Preclinical Imaging

“…For speckle reduction and to improve the contrast of the US image, Bayesian mean filtering using an open source software was used [13]. To form tomographic images, the B-scan images from both US and PA imaging were rotated to the acquired angle and spatially compounded using a custom developed MATLAB program [14].…”