Effects of Element Directivity in Linear-Array Photoacoustic Imaging - Biomedical Engineering & Biotechnology

Photoacoustic  imaging  (PAI)  is  an  emerging  medical  imaging  modality  with  a  steady  growth  in  both  pre-clinical  and  clinical  applications. In linear-array PAI, beamformers play a significant role in the image reconstruction procedure. Generally, beamformers assume  a  point-  like  model  for  the  elements  of  the  array,  and  the  elements  are  assumed  to  be  omnidirectional.  In  this  study,  we  investigated  the  effects  of  receiver  element  directivity  on  the  Photoacoustic  (PA)  image  formation  procedure  where  delay-and-sum  (DAS)  and  delay-multiply-and-sum  (DMAS)  algorithms  have  been  used  as  beamformers.  The  proposed  method  is  evaluated  experimentally  (wire  phantom  and  ex  vivo  imaging).  It  has  been  shown  that  the  contribution  of  the  directivity  of  the  transducer elements  improves  the  PA  image  quality.  The  results  show  that  using  the  directivity,  the  sidelobes  of  the  formed  image  (wire  phantom) by DAS are attenuated about 20 %, compared to when directivity is not used. Moreover, signal-to-noise ratio achieved by DAS and DMAS is improved by about 12.5 % and 11.3 %, respectively.

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