ifications. The approach starts by determining the amount of heat that a normal thyroid gland would generate, then the excess energy generated by the hyperactive thyroid of a nodule. This should give the incremental change in temperature distribution surrounding the tissue underneath the skin in order for the difference to be detectable at the skin’s surface. Not counting

Table 3. Comparison of various transducers/sensor types.

Table 4. Wien’s displacement law for a range of temperature values.

Figure 1. Planks radiation law plot near human body temperatures.

the impact of the blood flow, the model will be simple but limited in accuracy. That model considers only the conduction component of the heat transfer. The heating and cooling effects of blood flow in the capillaries of the skin were not considered. Helmy et al. [10] have simulated a simple model of 25 mm thickness of skin with an embedded 10 mm diameter hot nodule. This work is extended to include both the convection and radiation effects of the hot spot. The convection component is developed from the blood vessels, while the radiation is attributed to the IR sensor probe that is distant from the human skin surface. For our research we have designed a model with a 25 mm thick piece of skin and 30 mm × 30 mm square with an embedded 10 mm diameter hot module in ANSYS workbench. The properties for the skin are given to the cuboidal structure and the properties for the thyroid are given to the embedded sphere. The model is finally meshed for simulation with 19,767 nodes and 11,248 triangular surface meshes. Figure 2 depicts the cuboidal structure and the embedded circular gland.

At steady state, the heat lost to the external environment must balance the heat produced by the human body. The heat loss occurs by several heat transfer modes: radiation, evaporation, convection, and conduction. The environmental situations and metabolic conductions may govern the extent to which each node dominates. The human body must lose the excess heat it produces or a fever condition would result. An estimate of the temperature rise, which would occur in the body if no heat, is dissipated, and can be derived from the definition of the specific heat. The heat flux [11] , q is described by

,

where m is the mass, Dt is the temperature difference, and cp is the specific heat. We have considered varied specific heats for skin muscle and the thyroid gland. Results of computer simulation from finite elements are given in Figure 3. In this simulation the ambient surface temperature is assumed to be 25˚C and the model is simulated for both heat transfer and the heat flux by changing the temperatures of the embedded nodule. As determined from reference [3] the embedded energy within the nodule may present up to 3˚C temperature change, while keeping the normal temperature the surface of the body. Cooling off the neck in order to suppress the thermal noise may alter the starting temperature at the hot spot where the nodule is. Figures 3-5 give three different sets of temperature distribution, representing 34˚C, 37˚C, and 40˚C. Figure 3 gives a set of temperatures given at different times (separated by Dt).

Figure 2. (a) Structure of the cube; (b) Embedded thyroid gland.

Figure 3. Temperature plot at (a) 34˚C; (b) Sliced view at 34˚C; Heat flux plot at (c) 34˚C; (d) Sliced view 34˚C.

Figure 4. Temperature plot at (a) 37˚C; (b) Sliced view at 37˚C; Heat flux plot at (c) 37˚C; (d) Sliced view 37˚C.

Figure 5. Temperature plot at (a) 40˚C; (b) Sliced view at 40˚C; Heat flux plot at (c) 40˚C; (d) Sliced view 40˚C.

As preliminary estimate of the practicality of thermal sensing the thyroid gland through the skin of the neck, a rough test was devised and implemented. This involved testing the skin temperature on the neck over the thyroid gland of five subjects who had no known thyroid problems (control subjects). Figure 3 gives a typical set of temperature responses at 11 different positions on the neck surface. The five series give data at different times starting at t = 0, where the neck was cold down, for five sets of data separated by few minutes each. As it can be seen from the data, each subject’s thyroid lobes can be detected by a rise of temperature at the lobes, with lowered temperature detected in the center of the neck area, that correspond to the isthmus between the two thyroid lobes. This data verifies the localized temperature gradient on the neck. The data also shows that a temperature span of 1.5 - 2 degrees is evident on the skin surface in the area of the thyroid.

6. The Practical Model

The practical system made of eight IR probe connected with servomechanism that is controlled by a stepper motor was used for the data comparison. Figure 6 shows the practical model.

Figure 6. IR probe used for the practical model.

7. Results and Discussions

Figure 7 and Figure 8 show the gland nodule at different temperatures between 31˚C and 34˚C, and 34˚C to 38˚C. IR sensors have detected nodules with temperature distribution that overlap with the thyroid. Figure 7, Figure 9 shows the thyroid gland with a start of a nodule from the right side of the lobe. Figure 8 and Figure 10 shows for multiple cases with multiple nodule case for the same patients. However the thermography device system is a passive system, the institution has gone through the legal process to provide these data. IUPUI informed consent form for the Thyrothermography was taken, covering costs of participating, confidentiality, people to contact, and subject consent. An interdepartmental communication was also taken with IRB. These were the endocrinologist patients with case familiarity.

Practical Model Results

The patient’s carotid artery is detected by sensor S1, and two thyroid lobes are detected by sensors S3, S5 and S6. This results in apparent separation distance of approximately 4.5 - 5 cm on center. The temperature distribution within the lobes suggests a core heat source for each lobe, with no nodules.

The simulation results that were obtained by assuming a high temperature gland and its heat conduction and radiation parameters were in accordance with the practical results.

8. Conclusion and Future Work

The approaches followed here may be applied to various medical issues such as kidney stones, and nodular related cancers elsewhere. The computer simulation has shown the changes in temperature within the gland directed towards the skin’s surface. Heat transfer coefficients including conduction, convection, and radiation have added to the accuracy of the simulation, and assisted in the selection of the IR sensor that would be appropriate for the practical system. In some practical measurements, overlapping in temperature distribution from multiple nodules was clear, and this was attributed to the interference of each IR sensor on other sensors. In some cases, the nodule may be missed from the IR sensor data if the size of the nodule is comparable with the distance between the sensors. Future work should include a software process that guarantees scanning the regions around the gland. This process can be improved via a smart processing algorithm that processes data obtained from the scanned organ and analyzes the cancer tumors at various parts of the body. In the next phase, we

Figure 7. IR thermogram sequence of a patient. Hot spot shows up to 34.5 degrees after cooling off the neck.

Figure 8. 123I scan-toxic multinodular images. (a) LAO view; (b) RAO view; (c) ANT view at the left side, shows parts of the two gland lobes with 5 nodules around them, corresponding t thermal activities in contrast to relatively lower thermal corresponding.

Figure 9. IR thermo gram sequence of a patient. Hot spot shows up to 34.5 degrees after cooling off the neck.

Figure 10. 123I scan-toxic multinodular images. (a) LAO view; (b) RAO view; (c) ANT view at the left side (Figure 10(c)), shows parts of the two gland lobes with 5 nodules around them, corresponding to nodule thermal activity in contrast to relatively lower thermal surroundings.

are planning to develop an efficient IR sensing array of nano-sensors to acquire high-resolution scanning data. The parameters that effect the nano-sensing, such as noise due to ambient parameters, are reduced by placing the sensor array in a vacuum chamber along with liquid nitrogen coolant for maintaining a low-temperature sensor. The sensing apparatus will consist of a sensing array connected to a dedicated processor for initial processing of the data. The data will then be transmitted via WIFI to the host computer. In the future, we are planning to build a smart and integrated remote monitoring system to collect the data from the sensor system. Furthermore, this will be sent to a designated super computer electronically for additional analysis using complex algorithms and GPUs. These initiatives are reserved for future considerations. This will also be a new advancement in the wireless health field, thereby encouraging remote health monitoring systems.

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