Journal of Pure and Applied Ultrasonics

Madhusudan Roy ¹, Supratic Chakraborty ¹

Affiliations
1 Microelectronics Division, Saha Institute of Nuclear Physics, 1/AF Bidhan Nagar, Kolkata-700064, IN

Abstract

An anomaly in ultrasound attenuation of agarose hydrogel studied over a temperature range of 283 K to 311 K, is observed. Anomalous ultrasound attenuation occurs at ~290 K. A theoretical model has been worked out to explain the anomaly. A differential scanning calorimetry (DSC) study shows an endothermic peak at ~290 K, indicating phase transition when scanned over a temperature range of 282 to 330 K at different heating rates. The investigation helps identify the range of temperature over which a gelatin/agar-based phantom may be used in mimicking tissues. This effect may also be explored in temperature imaging.

Keywords

Ultrasound Attenuation, Agarose, Imonification, Pulse Echo, Time of Flight.

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Ratan K. Saha ¹, Subhajit Karmakar ¹, Madhusudan Roy ¹

Affiliations
1 Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700064, W.B., IN

Abstract

This study aims to investigate the role of red blood cell (RBC) concentration on photoacoustics (PAs). The time dependent PA signals from a collection of RBCs were simulated using a recently developed theoretical model. This model assumes each RBC as a fluid sphere and the PA signals from many cells are generated by adding the contributions from the individual cells. A Monte Carlo technique was implemented to generate the random locations of RBCs within a 2D simulation volume (200×200 μm²) mimicking a tissue realization. The PA signals were simulated for the 355 and 532 nm irradiating optical radiations. Our simulation results demonstrated that PA signal amplitude increased monotonically with RBC concentration for both input radiations and exhibited similar trends with those of experiments. The experiments were conducted with porcine RBCs suspended in saline water. A Nd:YAG laser system was used to provide the desired radiation and the detection of acoustic signals were made by a needle hydrophone. Good agreement between theoretical and experimental results confirms the validity of the theoretical model.

Keywords

Red Blood Cells, Photoacoustics, 2D Simulation.

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Anik Kumar Chakravorty ¹, Subhasree Mukherjee ¹, Kuntal Ghosh ², Ratan Kumar Saha ², Madhusudan Roy ³, Suparna Mazumdar ²

Affiliations
1 Pailan College of Management & Technology, West Bengal University of Technology, Kolkata-69, IN
2 Microelectronics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-64, IN
3 Department of Radiology, Chittaranjan National Cancer Institute, Kolkata-26, IN

Abstract

Texture analysis based on spatial gray-level dependence (SGLD) matrix computation was carried out over the input ultrasound images of livers to extract features, namely, maximum probability, uniformity, entropy, element difference moment of order 2, inverse element difference moment of order 2, homogeneity, correlation and contrast. In this work thirty ultrasound scan images of human normal livers as identified by the physician were collected from hospital. From each image portion of the liver, five sub-images were suitably cropped and taken as an input image for analysis. Finally, an unsupervised neural network learning technique viz. Self Organising Map (SOM) was used to classify normal liver parenchyma.

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Supratic Chakraborty ¹, Madhusudan Roy ¹

Affiliations
1 Microelectronics Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata-700064, IN

Abstract

This article deals with a feasibility of imaging the temperature of a specimen of interest in a noninvasive manner by ultrasound technique. A suitable working formula has been deduced to establish as to how ultrasound attenuation of a thermally bad and viscous material changes with the temperature. An experiment on the variation of ultrasound attenuation with the temperature was carried out. Agar hydrogel, a phantom material, mimics acoustic properties of soft tissues e.g. speed and attenuation has been taken as the sample for the proposed experiment. Temperature dependence of ultrasonic attenuation of agar phantom has been suggested as a noninvasive technique for temperature imaging. The attenuation of a tissue mimicking phantom, agar was estimated over a range of temperature of 293 to 316 K for three different agar densities (2%, 3% and 4% by weight). The variation of attenuation with temperature has been found to be a monotonic one in the above range and the curve can be used as a temperature calibration for agar in this temperature range. The concept may be applicable to all the real tissues to measure any temperature rise under in vivo condition during ablation or microwave thermotherapy provided the temperature dependence of ultrasound attenuation of the tissues are known before hand. PACS No: 43.90.+v, 43.58,+z, 05.70.-a, 43.80.-n.

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