Biomedical subjects

K Santosh

Publications and source records attributed to K Santosh.

4 recordsLinked to original sources

PubMed1995

Tissue characterization of arteries with 4 MHz ultrasound.

Reflections of 4 MHz ultrasound pulses from 60 sites on 15 human aorta specimens were analysed using the plane-wave Born approximation (PWBA) inverse scattering method. The recovered high-resolution acoustic impedance profile for each site was correlated with an analysis (by microscope) of sections taken from that site. The shape of the impedance profile was found to be sensitive to the pathology of the tissue at each site. The severity of the various conditions could be gauged from the recovered impedance profiles. Some of the insonifications were done on aorta specimens that were shielded from the ultrasound transducer by a human tissue specimen about 1.25 cm thick in order to study the effects of intervening tissue. We found that it was possible to compensate for the distortion due to the frequency dependent attenuation of the intervening tissue. We conclude that ultrasound imaging, with the reflections analysed by means of PWBA inverse scattering provides a promising non-invasive tissue characterization modality.

Aorta↗

PubMed1990

In vivo biomicroscopy with ultrasound 2.

In the first article of this series it was shown that the use of inverse scattering theory to analyse ultrasound reflections could provide high resolution images of the acoustic impedance profile of the retina. Unlike the retina, most tissue structures of interest, like small tumours and arterial plaque deposits, are shielded from view by intervening layers of tissue of appreciable acoustic impedance and attenuation. By analysing a one-dimensional model for a plaque deposit on the wall of a carotid artery embedded in a 5 cm thick layer of tissue, we demonstrate that a relatively high quality image can be recovered when compensation for the attenuation of the intervening tissue is made. We observe that because of the dearth of low frequency power in the recovered signal of ultrasound transducers, it is important that the field of view imaged is not taken to be too large. We compare the exact iterative distorted wave Born approximation inverse scattering method with the approximate but computationally faster plane wave Born approximation method and find that they give images of comparable quality for this model.

Acoustics↗

PubMed1987

In vivo biomicroscopy with ultrasound.

We propose the use of inverse scattering theory methods to analyse high frequency ultrasound reflection data to provide high resolution images of living tissue. Conventional ultrasound imaging uses the pulse-echo method which can only resolve structures which are large compared to the wavelength of the ultrasound. Inverse scattering analysis, on the other hand, can image details as small as a quarter wavelength. This makes possible a significant improvement in resolution and has many potential applications in the detection and study of disease. We report here results obtained using this method to produce images of the retina, where we were able to resolve details as small as 50 micron in a 300 micron layer.

Acoustics↗

PubMed1980

Computed tomography with microwaves.

Computed tomographic images were generated using collimated microwaves of frequency 10.5 GHz instead of x rays. In the authors' laboratory version of a rotate-translate scanner, the beam is fixed and a phantom is moved between source and detector, the apparatus being suspended in a tank of fluid to provide impedance matching between phantom, source, and receiver. Phantoms consisting of test tubes of water, cylinders of wood, and animal tissues show spatial resolutions of about 2 cm. It is planned to apply the technique first to mammographic examination, which can best utilize the large difference in microwave absorption between fatty and nonfatty tissues.

Computers↗