Locating an acoustic point source scattered by a skull phantom via time reversal matched filtering

Abstract

This paper examines the utilization of the time reversal matched filtering method to resolve the location of an acoustic point source beneath a skull phantom (variable thickness layer), without the removal of this layer. This acoustical process is examined experimentally in a water tank immersion system containing an acoustic source, a custom-made skull phantom, and a receiving transducer in a pitch-catch arrangement. The phantom is designed to approximately model the acoustic properties of an average human skull bone (minus the diploe layer), while the variable thickness of the phantom introduces a variable time delay to the acoustic wave, relative to its entry point on the phantom. This variable delay is measured and corrected for, and a matched filtering time reversed process is used to determine the location of the point source. The results of the experiment are examined for various positions of the acoustic source behind the phantom and compared to the reference cases with no phantom present. The average distance between these two cases is found to be 4.36 mm, and within the expected deviation in results due to not accounting for the effects of refraction.

Acoustical Imaging in Heterogeneous Environments

“…To all mentioned effects one should add an additional damping of ultrasound in the hairline. Numerous studies of ultrasound transcranial diagnostics [17][18][19][20][21][22] indicate that the MSP and TRA are possible methods of obtaining images of the brain structures, though there is problem of reference point.…”

“…The perspective possible approach is to use the same ultrasound methods of measuring different parameters of skull bone [27][28][29][30]. One can use as multielement array or scanning single transducer.…”

“…The role of these fluctuations is particularly significant in the underwater imaging. TRA can solve this problem only partly, because it does not require the knowledge of transfer functions as in matched filtering procedures, [30]. However, the "payback" for such possibility is the "spacing" of receiving and transmitting points that is impossible in many practical cases.…”

Experimental implementation of reverse time migration for nondestructive evaluation applications

“…Time reversal may be used to image linear scatterers through a series of time reversal experiments and complex processing, 19,20 or it may be used to directly image nonlinear scatterers (which are the sources of new frequency content). [21][22][23][24] However, the typical aim of time reversal is to localize sources, [25][26][27][28][29][30] whereas the aim of RTM is to directly image linear scatterers without the need for complex processing, or the requirement that the scatterers be nonlinear.…”

Lamb Waves and Adaptive Beamforming for Aberration Correction in Medical Ultrasound Imaging

“…The drawback of this method is its poor resolution. Another method is the time-reversal aberration correction introduced in [7,[23][24][25]. These methods usually require an invasive experimental setup for computation of the time reversed signals.…”