Author name: Chaya Chaimongkhol

Wongchadakul P., Datta A.K.and Rattanadecho P.“Tissue poromechanical deformation effects on steam pop likelihood in 3-D Radiofrequency Cardiac Ablation” Journal of Biological Engineering 2023, https://doi.org/10.1186/s13036-023-00365-5 Impact Factor: 6.248, Q1 Abstract Radiofrequency Cardiac Ablation (RFCA) is a common procedure that heats cardiac tissue to destroy abnormal signal pathways to eliminate arrhythmias. The complex multiphysics phenomena during this procedure need to be better understood to improve both procedure and device design. A deformable poromechanical model of cardiac tissue was developed that coupled joule heating from the electrode, heat transfer, and blood flow from normal perfusion and thermally driven natural convection, which mimics the real tissue structure more closely and provides more realistic results compared to previous models. The expansion of tissue from temperature rise reduces blood velocity, leading to increased tissue temperature, thus affecting steam pop occurrence. Detailed temperature velocity, and thermal expansion of the tissue provided a comprehensive picture of the process. Poromechanical expansion of the tissue from temperature rise reduces blood velocity, increasing tissue temperature. Tissue properties influence temperatures, with lower porosity increasing the temperatures slightly, due to lower velocities. Deeper electrode insertion raises temperature due to increased current flow. The results demonstrate that a 5% increase in porosity leads to a considerable 10% increase in maximum tissue temperature. These insights should greatly help in avoiding undesirable heating effects that can lead to steam pop and in designing improved electrodes.

Wongchadakul P., Ashim K D. and Rattanadecho P. “Natural convection effects on heat transfer in a porous tissue in 3-D radiofrequency cardiac ablation”International Journal of Heat and Mass Transfer Vol 204, 2023 (123832) Scopus, Q1 : Impact Factor 5.431 Abstract Radiofrequency Cardiac Ablation (RFCA) is a non-surgical procedure to destroy abnormal pathways caus- ing cardiac arrhythmias within the cardiac chamber. RF energy from electrodes contacting the cardiac tissue generates heat, raising tissue temperature and ablating it. Success of the procedure, as in avoiding complications like steam pops, requires its comprehensive mechanistic understanding. Using a 3-D porous media-based model of the cardiac tissue and surrounding chamber blood, with coupled fluid flow, heat transfer (including evaporation and thermally driven natural convection), and resistive heating, provided a more complete picture of the thermal ablation process. Circulation of blood due to buoyancy-driven natural convection reduces the non-uniformity of temperatures, by reducing temperatures initially in the target region but increasing them in the later stages, compared to when natural convection effects are not included. Thus, natural convection affects possible steam pop occurrence differently over the time for the procedure. The more complete picture of the RFCA procedure provided here by the detailed physics-based model can benefit with increased accuracy and thus reduced re-ablation (thus higher success rates), and reduced costs for catheter design and development.

Wongchadakul P., Rattanadecho P., and Wessapan T. “Simulation of Temperature Distribution in Different Human Skin Types Exposed to Laser Irradiation with Different Wavelengths andLaser Irradiation Intensities” Songklanakarin Journal of Science and Tenochlogy, vol 41 (3) pp.529-538 May-Jun 2019 Impact Factor 0.47 (Q3) Abstract In modern medical facilities, laser technology is becoming more important in aesthetic and medical applications. However, inappropriate laser irradiation can result in harmful effects such as thermal burn injury. This occurs because thermal response of the skin due to laser irradiation is not well understood. In this study, the thermal response of skin to laser radiation was investigated under the effects of wavelength, laser intensity, and incident time. The transient bioheat model was considered and solved numerically using the finite element method. This study demonstrated that the skin temperature distribution depends strongly on the wavelength, intensity, and skin color type. The amount of energy absorption is significantly higher in the shorter wavelength range and with increasing intensity. Further, a darker skin color results in higher laser absorption. The obtained values provide an indication of the limitations that must be considered during laser-induced thermotherapy.

Wessapan, T., Rattanadecho, P. and Wongchadakul, P.”Effect of body position on natural convection within anterior of the human eye during exposure to electromagnetic fields” Numerical Heat Transfer; Part A: Applications, VolDOI:10.1080/10407782.2015.1109352, pp.1014-1028, 2016. Impact Factor: 2.96 (Q1) Abstract Heating is the main biological effect of the electromagnetic (EM) fields to human eye. This study intends to focus attention on the differences in the heat transfer characteristics of the human eye induced by EM fields in different body positions. The effect of three different body positions – sitting, supine, and prone – on natural convection of aqueous humor (AH) in the anterior chamber of the eye is systematically investigated. The specific absorption rate (SAR) value, fluid flow, and the temperature distribution in the eye during exposure to EM fields are obtained by numerical simulation of EM wave propagation. In this study, the frequencies of 900 and 1,800 MHz are chosen for the investigations. The heat transfer model used in this study is developed based on natural convection and porous media theories. The results show that the AH temperature inside the anterior chamber is the highest in the supine position at both frequencies. It is found that during exposure to EM fields, body position plays an important role on AH natural convection and the heat transfer process within the anterior chamber and its periphery in the front part of the eye. However, the body position has no significant effect on temperature distribution for the middle part of the eye. The obtained results provide information on the body position and thermal effects from EM fields exposure.

Bhargava D. Jiamjiroch K. and Rattanadecho P. “Microwave Imaging for Breast Cancer Detection- A Comprehensive review“ Engineered Science,vol 30, pp.1116 2024,DOI:10.30919/es1116 Scopus, Q1 : Impact Factor 16.6 Abstract The paper presents an extensive discussion on Microwave Imaging (MI) for breast cancer detection. Breast cancer has become a major cause of death among women worldwide, this makes the early detection of the cancerous tumor very essential in providing a rapid and effective treatment. Microwave Breast Imaging (MBI) is an emerging technique that is non-ionizing, non-invasive, safer and cheaper in comparison to the conventional techniques. It uses microwave radiation to generate an internal image of the breast, showing the tumor embedded in the breast layers. The paper begins by introducing the basic working principles of MBI and its types, anatomy of the breast, and the differences in the dielectric properties between normal and malignant tissues. Active type of MBI – tomography and radar-based imaging are mainly covered in this paper. The most important part of active microwave imaging, i.e. antennas used for scanning the breast are also discussed. Moreover, numerical, experimental as well as clinical studies performed over the years are highlighted. In the end, challenges in the current techniques and future prospective of MBI are presented. Overall, this review paper provides a comprehensive insight into the techniques used in MBI, and the state-of-the-art research in this field.

Preechaphonkul W. and Rattanadecho P. , “The effects of dielectric & thermal property functions on the thermal response during the focused microwave ablation treatment in the liver cancer model: numerical investigation“, Engineered Science, 2022, Scopus, Q1 : Impact Factor 2.436 Abstract Radiofrequency Cardiac Ablation (RFCA) is a common procedure that heats cardiac tissue to destroy abnormal signal pathways to eliminate arrhythmias. The complex multiphysics phenomena during this procedure need to be better understood to improve both procedure and device design. A deformable poromechanical model of cardiac tissue was developed that coupled joule heating from the electrode, heat transfer, and blood flow from normal perfusion and thermally driven natural convection, which mimics the real tissue structure more closely and provides more realistic results compared to previous models. The expansion of tissue from temperature rise reduces blood velocity, leading to increased tissue temperature, thus affecting steam pop occurrence. Detailed temperature velocity, and thermal expansion of the tissue provided a comprehensive picture of the process. Poromechanical expansion of the tissue from temperature rise reduces blood velocity, increasing tissue temperature. Tissue properties influence temperatures, with lower porosity increasing the temperatures slightly, due to lower velocities. Deeper electrode insertion raises temperature due to increased current flow. The results demonstrate that a 5% increase in porosity leads to a considerable 10% increase in maximum tissue temperature. These insights should greatly help in avoiding undesirable heating effects that can lead to steam pop and in designing improved electrodes.

Bhargava D. , Leeprechanon N. Rattanadecho P. and Wessapan T., “Specific Absorption Rate and Temperature Elevation in the Human Head Due to Overexposure to Mobile Phone Radiation with Different Usage Patterns”, International Journal of Heat and Mass Transfer, Vol 130, pp. 1178-1188, 2019: Impact Factor 4.94 (Q1) Abstract Accidental overexposure to non-standard mobile phone radiation can occur in many situations. The overpower limit of mobile phone radiation interacts with the human body which could result in an adverse effect on human health. It is envisaged that the severity of the physiological effect can take place with small temperature increase in the delicate organs or tissues such as eyes, brain, skin, etc. However, the resulting thermo-physiological response of the body tissues to overpower limit of mobile phone radiation is still not well implemented. The aim of this study is to analyze the effect of overexposure of mobile phone radiation on the specific absorption rate (SAR) and temperature increase in three-dimensional heterogeneous human head models. The study focuses attention on the differences in the electromagnetic (EM) absorption characteristics with higher power level among different usage pattern. The effect of three different usage patterns – voice calling, video calling, and texting- on SAR and temperature distributions in different types of head tissues is systematically investigated. This paper also investigates the effects of different user ages, radiated powers, and gap distances between mobile phone and human heads, on SAR and temperature distributions. Results obtained from this analysis considering the safety guidelines show a high impact of mobile phone radiation in the voice calling position. Hence, comparisons of the absorption of mobile phone radiation are calculated between an adult and a 7-year-old child head model, for the voice calling position at different gap distances. In addition, the results indicate that child head always has a higher absorption rate of mobile phone radiation than the adult head. The rate of absorption in tissue increases as the distance between mobile phone and head decreases and the radiated power increases, depending on their dielectric and thermal properties. The obtained results can be helpful in determining exposure limits for the power output of the mobile phone, and the distance a user should maintain from the mobile phone in thermo-physiological aspects.  

Wessapan, T. and Rattanadecho, P. “Temperature Induced in Human Organs due to Near-Field and Far-Field Electromagnetic Exposure Effects“. International Journal of Heat and Mass Transfer, Vol 119, pp. 65-76, 2018: Impact Factor 4.94 (Q1) Abstract The main biological effect from exposure to electromagnetic (EM) radiation is a temperature rise in the human body and its sensitive organs, which results from absorbing electromagnetic field (EMF) power. EM near-field and far-field sources, which have different operating frequencies and exposure distances, result in different EMF distribution patterns and EMF power absorptions by the human body. Actually, the severity of the physiological effect can occur with small temperature increases in the sensitive organs. However, the EM absorption characteristics and the temperature increase distribution resulting from different field radiation patterns from EM sources are not well established. To adequately explain the biological effects that are associated with the EMF energy absorption, a systematic study of different EMF distribution patterns and how they interact with body tissue is needed. This study considers the computationally determined specific absorption rate (SAR) and the heat transfer in a heterogeneous human torso model with internal organs exposed to near-field and far-field EM radiations at different frequencies. The electric field, SAR, and the temperature distributions in various organs during exposure to EMFs are obtained through the numerical simulation of EM wave propagation and an unsteady bioheat transfer model. The findings indicate that the field radiation pattern and the operating frequency of an EM source significantly influence the electric field, the SAR, and the temperature distribution in each organ. Moreover, the tissue’s dielectric properties also affect the temperature distribution patterns within the body tissue. These findings enable researchers to more accurately determine the exposure limits for the power output of wireless transmitters, and the distance that they should remain from the humans.