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182 || AWSAR Awarded Popular Science Stories - 2019
are occurring inside the body without cutting it. Also, looking at these images I can see how the heat is getting distributed and I can control it by varying power that is given to HIFU transducer for creating burns.
The results obtained from methods developed are shown in the figures below. The three methods developed in our lab track different acoustic parameters and thereby trace the evolution of hotspot. In order to compare with the ground reality the liver sample on which the heating was done using HIFU is cut at the end of the experiment. A snapshot of it can be seen below. The methods have shown good repeatability and till date 17 experiments have been successfully conducted on ex-vivo liver samples.
The success on the ex-vivo motivates us to move one step ahead and conduct the experiment on small animals. However, we do not have the ethical approvals for it as of now thus this is the permissible
level, which we could go to
test the algorithm. The major
challenge is to make these
algorithms fast. In order to do
that we need to use graphical
processing unit and lower level
language to implement it. The
major limitation of the work is
that the maps obtained are
qualitative not the absolute
temperature maps. They
need to be calibrated to make
them quantitative in terms of
temperature.
The results demonstrate that the sensitivity of each of the three methods is very different. Either, these or a non-trivial combination of these methods can be used to construct more robust maps that can track spatial and temporal evolution
of the hotspot with better precision and accuracy.
The feedback can also be used along with some machine-learning techniques to control the RF power amplifier that provides input signal to the HIFU transducer. This will reduce human intervention and possible human errors. Thus, the entire system can be automatized. The transducer that was used in our experiments is a single-element focused HIFU transducer. However, in reality a variable focus HIFU transducer is required. It can be done using a collection of HIFU transducers and applying delays to each of the single element HIFU transducer to focus at a particular location. Thus, the research that we have done so far is a baby step towards realizing a fully functional HIFU treatment device that in future
The sound is very sensitive to temperature. Also, when we heat the medium or target it,
it undergoes changes. These changes affect the ultrasound wave propagation. If we are able to capture the reflected ultrasound the signature of the temperature is present
in the reflected ultrasound. This information can be in the form of change in speed of sound, change in attenuation of sound, change in the statistical distribution of scatterers that are present in the medium.