In this paper we present a method to visualize the pressure field of an ultrasound beam in a single shot of the CCD and
to image the shear wave propagation based on acousto-optic laser speckle contrast analysis. The contrast images show
features in the near field, far field and central region of the ultrasound beam and the pressure profile fits with that
measured with a hydrophone. The shear wave propagation was acquired by changing the imaging delay time after the
ultrasound burst. This method can be used to study the shear wave properties of common tissue phantoms to guide
experiments on tissue.
We present a dual-wavelength endoscopic laser speckle contrast system including illumination with polarization
maintaining fibres and imaging using a leached fibre image guide. This system has a frame rate of 10 Hz and can
rapidly monitor changes in blood flow in vivo, including due to the heart beat, using the contrast values of the speckle
images recorded with 1 ms exposure time. In addition the mean intensities can record the respiration period and can indicate changes in tissue oxygenation. This system was tested during an occlusion to a human finger and is being applied in endoscopy.
There are several challenges when fibre image guides (FIG) are used for endoscopic speckle acquisition: cross talk
between fibre cores, FIG fixed pattern noise, the small probe diameter and low sensitivity and resolution due to the
decreased number of speckles and their low transmission through the FIG. In this paper, an endoscopic laser speckle
contrast analysis system (ELASCA) based on a leached fibre image guide (LFIG) is presented. Different methods of
acquiring LASCA images through LFIGs were investigated including the effect of changing the number of speckles per
fibre, defocusing the FIG image onto the CCD and processing speckle images with masks and Butterworth filters to deal
with the LFIG fixed pattern and noise from the cladding. The experimental results based on a phantom consisting of
intralipid suspension pumped at varying speed showed that this system could detect speed changes and that in the case of
multiple speckles per fibre the Nyquist frequency criterion need not be applied since the speckle may be transferred
through the fibres to some extent. In contrast to the previously reported ELASCA results, this system can both give a
map of the observed area and the temporal change in flow. An additional benefit is the small size of the LFIG, which is
compatible with current endoscopic instrument channels and may allow additional surgical applications.