Coupled Sub-aperture and Spatiotemporal Singular Value Decomposition Processing for Cardiac Photoacoustic Imaging In Vivo

In vivo cardiac photoacoustic imaging (PAI) done with delay-and-sum (DAS) beamforming is susceptible to lower image quality due to sidelobes, along with quasistatic and incoherent clutter. These artifacts impose constraints in the localization of the myocardial wall based on these images. Here, we report on combining photoacoustic sub-aperture processing (PSAP) and spatiotemporal singular value decomposition (STSVD) to address these issues. Sub-aperture beamformed images filtered using STSVD were utilized to derive a weighting matrix to reduce DAS clutter. The proposed method is termed as coupled PSAP and STSVD (PSAP+STSVD). PSAP+STSVD was compared against DAS, PSAP and STSVD using single wavelength PAI data collected from four healthy mice. Quantitative comparison was done using contrast ratio (CR) and generalized contrast to noise ratio (gCNR). PSAP+STSVD provided the highest CR (e.g. at diastolic phase, mean CR values for DAS, STSVD, PSAP and PSAP+STSVD were 8.78, 14.58, 18.04 and 25.88 dB) while STSVD had the highest gCNR (e.g. at diastolic phase, mean gCNR values for DAS, STSVD, PSAP and PSAP+STSVD were 0.53, 0.75, 0.56 and 0.71).