Understanding Human Tissue Properties

Introduction

Seventy percent of human body is made up of water, including the vessels (1). The principal objective of this experiment was mimicking human tissues and understanding its properties better which included acoustic and thermal properties (2).

Part 1: Agar Phantom Fabrication

The phantoms replicate the human tissues and this replication process is often very useful and practical because the characteristics of phantoms are same as the human tissues (3). The use of the phantoms can be in several biomedical research applications, which includes cancer related photothermal therapy (4). This first experiment had an objective of presenting methods to fabricate phantom simulating the thermal and optical properties of a range of human tissues (3). Firstly, the procedure was carried out with the use of degassed water and agar as follows.

1. For the agar, a container was prepared and in the centre of the tank, a hotplate was positioned.

2. The accuracy of the water proportion to agar is very important. The ratio for this experiment had been agar of 2 g to degassed water of 100 ml.

3. In a beaker, the degassed water was poured and in a microwave it was heated till the proper temperature was reached.

4. Then, to the degassed water, the agar was added and heated for 20 minutes in a temperature of 95 °C.

5. Lastly, the mixture, at the room temperature was cooled and refrigerated overnight.

Part 2: Thermal Property Measurement

This experiment has shown the heat transfer through the agar. In doing this, a planar heat source with its thin layer have had its placing first between layers 2 and 3. In measuring the sample with the temperature inside it and recording the changing of it through time, a fine diameter between layers 2 and 3 was placed at a 10.8 cm distance from the agar’s top. At the room temperature, minimizing the temperature difference was started between the room and the phantom and isolating the exchange of energy in ensuring its accuracy.

In Figure 2, after the insertion of the thermocouple in a 1 cm distant first hole from the source of heat, and is made level and straight with the heat centre, the fitted curve was obtained being smoothed with the use of Matlab in enabling its study, and have shown over time, the change in temperature. The y axis represents the temperature and x axis the time in seconds.

Figure 2 has shown a smoothed diagram that illustrated the changing of temperature over time.

Figure 3 have shown the fitted curve that had resulted following the insertion of the thermocouple in the 2 cm distant second hole from the source.

The procedure of the experiment has been shown below.

1. Preparation of the phantom sample

a. Procedures to create materials which are tissue mimicking have been followed along with the incorporation of the planar source in the TMM.

b. The placement of agar platform on the heat source in cylinders.

With the use of hole of 0.08 mm drilled in the insulation, the alignment of the thermocouple’s sensor was done in making it level and straight with the centre of the source of heat.

2. Initialization of device

a. The device had been put to operation with the use of appropriate connections.

b. The power supply had not been turned on till the preparation of the sample for the experiment.

3. Key steps before the start

What was done has been described below for ensuring the correct distance between the spot and the top of the mimic in the place of the wire insertion.

a. Adjustment done with the phantom for avoiding the heat loss.

b. Perpendicular cutting was done with the top of the sample and had been flat alongside its sample.

c. The unbroken heating surface with its attachment had been with no spots lacking attachment between the two surfaces.

d. On the top, there was repetition of the same procedure for the mimic’s second part.

4.Measuring increase of temperature and to fit the non-linear curve

a. For running properly, the labview was opened and inputted with the details in order to run properly. The measurement’s entire duration on the front panel was set to 600 sec. The procedure, during the experiment, was halted at 300 sec at the time of making the measurement. In case the experiment had taken the whole of 600 sec, there would have been decrease of the graph due to the agar’s capacity.

b. Labview simultaneously started alongside the experiment. The power supply had been 0.1 A and 40 V.

c. At the termination of the procedure, the power was immediately turned off.

Summary

The experiment identified the agar’s thermal properties being measured as close to the human body’s soft tissues. The simulation that uses agar led to the comprehension in relation to the rate of the heat movements through human tissues.

Part 3: Acoustic Property Measurement

This experiment has delved into the investigation of human body with its acoustic properties and with the use of the presence of an agar phantom. The conclusion of the experiment and way it is conducted is stated below. Firstly, the agar’s acoustic properties were measured in this experiment with the use of one transducer, operating as both an ultrasound receiver and an ultrasound generator. The transducer generated the ultrasound wave, travelling to the steel board and returning to the receiver. The time taken by the signal as received from the transducer was recorded and denoting it as dt. Additionally, it was important; throughout the process that distance remained unchanged and monitoring was done to thickness of the phantom. This step had the primary goal of understanding the velocity of the ultrasound in the water (µŵ) that is obtainable with the use of a formula given below.

νŵ = 2D/dt

Distance between the steel board and the transducer (m) is denoted by d, which was (10.8* x 10-2) and the measure of the travel time, dt was (144*x 10-6). In the second step of the experiment, the placing of the phantom was between the two transducers in the middle, where h denoted the transducer’s thickness. The top of the phantom reflecting the signal was reflected by the initial echo and the border between the bottom of the phantom and the steel board was reflected by the signal where it matched the second echo.

The formula shown below was used in calculating the phantom’s velocity (νρ).

The water’s acoustic impedance and agar sample had been subject to calculation with the use of an equation given below.

Z = ρ x ν

There was an acoustic impedance of water, differing from the agar that solicited to be more careful with the sound velocities in the agar and in the water. The formula shown below was used for the calculation of acoustic attenuation in dB/cm.

Summary

The phantom’s acoustic properties were examined by this experiment having the identical density as living tissues.

Conclusion

The experiments conducted had attempted in mimicking the human tissues and in understanding a few of its properties that includes the acoustic and thermal ones. An agar phantom was fabricated by the first experiment. The thermal properties of the phantom were measured by the second experiment. The phantom’s acoustic properties were measured by the third experiment resembling the human tissues. For the avoidance of the human tissues, the experiments had been entirely conducted on agar phantoms mimicking biological tissue properties.

Dig deeper into Christian Leadership in Diverse Societies with our selection of articles.

References

Jaime RAO, Basto RLQ, Lamien B, Orlande HRB, Eibner S, Fudym O. Fabrication methods of phantoms simulating optical and thermal properties. Vol. 59, Procedia Engineering. 2013. p. 30–6.

Yu DU, Shrestha BL, Baik OD. Thermal conductivity, specific heat, thermal diffusivity, and emissivity of stored canola seeds with their temperature and moisture content. J Food Eng. 2015;165:156–65.