Assessment of Holmium:YAG, Pulsed-Thulium:YAG and Thulium Fiber Lasers for Urinary Stone Ablation. In Vitro Study.

Objective: To evaluate the ablation speed (AS), laser efficiency and direct thermal lesions during urinary stone lithotripsy with the current available laser technologies: Holmium:YAG (Ho:YAG), pulsed-Thulium:YAG (p-Tm:YAG) and thulium fiber laser (TFL) in vitro using different laser settings. Materials and Methods: Ho:YAG, p-Tm:YAG, and TFL laser system were used in an in vitro ureteral model with a volume of 125 mm3 Begostone. The following parameters were tested across all laser devices: 0.6J/10 Hz (6 W), 0.6 J/20 Hz (12 W), 1.5 J/10 Hz (15 W), and 1.5 J/20 Hz (30 W), employing short pulse width for all lasers and long pulse width for Ho:YAG and p-Tm:YAG. Ten participants conducted the experimental setup during 3-minutes laser on time, combining the laser technology, settings, and pulse widths, with a total of 20 different combinations. The efficiency, AS and ureteral damage resulting from each intervention were analyzed. Results: p-Tm:YAG and TFL demonstrated significantly higher efficiency compared with Ho:YAG (0.049 ± 0.02 Δgr/KJ and 0.042 ± 0.01 Δgr/KJ vs 0.029 ± 0.01 Δgr/KJ; p < 0.05). In all laser sources, as the power increases, the AS also increases (p < 0.05). Furthermore, only at high-energy settings (1.5 J) higher frequency led to increase AS (p < 0.05). Both, p-Tm:YAG and TFL exhibited higher AS compared to Ho:YAG (0.64 ± 0.33 Δgr/s and 0.62 ± 0.31 Δgr/s vs 0.44 ± 0.22 Δgr/s; p < 0.05). Regarding ureteral injuries, as the power increases, there is a higher chance of ureteral damage (p = 0.031). No differences were observed between laser technologies (p = 0.828). Conclusions: Both, p-Tm:YAG and TFL exhibited superior performances during laser lithotripsy compared with Ho:YAG, as they demonstrated higher efficiency and ablation speed. Thermal damage did not appear to be associated with specific laser equipment, but higher grades of lesions are described by increasing power.

Experimental Study on the Process and Performance of Laser-Assisted Vascular Anastomosis Based on Response Surface Methodology.

The selection of an appropriate vascular anastomosis process has an important impact on the surgical treatment of coronary artery disease. In this paper, a laser-assisted vascular anastomosis process test was carried out based on the response surface experimental method, and the interaction of laser process parameters on the bursting pressure strength and thermal damage of the anastomotic incision was analyzed, and the relationship model between process parameters and anastomotic performance of the vascular incision tissues was established, and the optimal welding process parameters were obtained. The results show that the laser power has a significant effect on the bursting pressure strength of the anastomotic incision; the interaction of laser power and scanning speed has a substantial impact on the thermal damage of the anastomotic incision; and the anastomotic incision has the best comprehensive performance when the laser power is 6.2 W, the scanning speed is 206 mm/s, and the defocus is 2 mm.

Discrimination of slight thermal damage to hair for arson investigation.

To determine whether a suspect was in close contact with the fire source at a fire site through slight thermal damage to hair, a cone calorimeter was employed to simulate fire scene conditions as a standard radiant source. The research focused on analyzing the thermal behavior of black hair and delving into the morphological characteristics of hair exhibiting slight thermal damage. At temperatures exceeding 240 °C, the proteins within the hair began to degrade. This degradation, in conjunction with tension along the hair shaft resulting from water loss, led to the formation of microcracks that could be detected through scanning electron microscopy (SEM) but eluded observation with an optical microscope (OM). It is noteworthy that the initial slight thermal damage was regularly located at the hair shaft but not the hair tip, which should be the key parts when exanimating hairs without obvious thermal damage. Additionally, during very short exposure, the appearance of typical slight thermal damage on fire is probabilistic events. Along with the increase of temperature, the organic compounds in hair were thermally degraded into NH3, SCO and carbon CO2, resulting in the typical traces of discoloration, expansion, blistering, and cracking presented at hair shafts and tips. The probability of encountering both slight and obvious thermal damage on hair increased with rising temperatures. By observing the traces on the easily overlooked part of the hair shaft, the research established a method to analyze and discriminate the slight thermal damage to hair at fire scene, which provide valuable references for confirming arson suspects.

Development of an ultrasound-guided radiofrequency ablation technique in the equine cadaveric distal limb: histological findings and potential for treating chronic lameness.

Introduction: Radiofrequency (RF) relieves chronic pain in humans, but it is unexplored in horses affected by chronic lameness. This study aims to describe the technique and the histological effects of ultrasound (US)-guided radiofrequency ablation (RFA) of palmar digital nerves (PDNs) in horse's fetlock and pastern, ex vivo. Methods: After assessing the US anatomy of lateral and medial PDNs in fetlock and pastern in vivo (n = 10 horses; 20 forelimbs), US-guided RFA was performed on these sites in cadaveric forelimbs (n = 10) applying four different settings with increasing invasiveness (n = 40 total treatments): 60°C, 6 min (GROUP LOW); 70°C, 4 min (GROUP MEDIUM); 90°C, 2 min (GROUP HIGH); 80°C, 8 min (GROUP VERY HIGH). Needle-tip-to-nerve proximity was assessed with US and methylene blue, injected through the port of the RF needle. Nerves were collected for microscopical assessment. Results: Transverse palmaro-lateral and palmaro-medial US images of fetlock and pastern detected PDNs consistently, close to the palmar digital artery. With in-plane US technique, RFA was performed at target in 31/40 cases, with significantly higher number of failures in fetlock (p = 0.008). PDNs histology identified thermal injury/coagulation with axonal degeneration and collagen homogenation. Nuclear smearing of arterial leyomyocytes was also observed. Nerve coagulation was significantly associated with treatment (p = 0.03) and needle-tip-to-nerve proximity (US distance: p = 0.009; blue distance: p = 0.04). Discussion: The PDNs were easily visualized and reached with the RF needle by US in-plane-guided technique. RFA produced axonal thermal damage and intensity-related coagulation effectiveness. To ensure effective nerve coagulation, it is crucial that the needle is accurately positioned in close proximity to the target nerve. Based on the histopathological findings, HIGH and VERY HIGH RFA treatments might be worth of being tested in vivo in clinical studies aimed at treating chronic lameness of the distal forelimb in horses.

Steady-state versus burst lasing techniques for thulium fiber laser.

OBJECTIVE: To evaluate the stone ablation rate and direct thermal damage from thulium fiber laser (TFL) lithotripsy using continuous (C) and burst (B) lasing techniques on an in vitro ureteral model. METHODS: The TFL Drive (Coloplast, Humlebaek, Denmark) was used in an in vitro saline-submerged ureteral model. Ten participants, including five junior and five experienced urologists, conducted the experimental setup with 7 different settings comparing two lasing techniques: steady-state lasing (0.5 J/10 Hz = 5W for 300 s and 0.5 J/20 Hz = 10W for 150 s) and burst, intermittent 5 s on/off lasing (0.5 J/20 Hz, 0.5 J/30 Hz, 0.5 J/60 Hz, 0.1 J/200 Hz, and 0.05 J/400 Hz) with a target cumulative energy of 1500 J using cubic 125 mm3 phantom BegoStonesTM. Ureteral damage was graded 1-3 based on the severity of burns and holes observed on the surface of the ureteral model. RESULTS: The were no significant differences in stone ablation mass neither between C and B lasing techniques, nor between expertise levels. At C lasing technique had only mild ureteral lesions with no significant differences between expertise levels (p: 0.97) or laser settings (p: 0.71). At B lasing technique, different types of thermal lesions were found with no expertise (p: 0.11) or setting (p: 0.83) differences. However, B laser setting had higher grade direct thermal lesions than C (p: 0.048). CONCLUSION: Regarding efficacy, C and B lasing techniques achieve comparable stone ablation rates. Safety-wise, B lasing mode showed higher grade of direct thermal lesions. These results should be further investigated to verify which of the lasing mode is the safest in vivo. Until then and unless proven otherwise, a C mode with low frequency should be recommended to avoid ureteral wall lesions.

Minimizing Invasiveness in Neurosurgical Osteotomies: A Comparative Histomorphometric Study of Piezoelectric Craniotomy versus High-Speed Drill.

BACKGROUND: Piezoelectric bone cutting has gained popularity in neurosurgical osteotomies due to perceived lower trauma compared to rotary instruments. However, histological confirmation of its decreased aggressiveness is lacking, hindering conclusive proof. This study compares the bony and neuro-meningeal invasiveness of piezoelectric craniotomy with high-speed drill techniques. METHODS: Histological data from 21 sheep undergoing piezoelectric craniotomy and 19 sheep subjected to high-speed electric drill craniotomy were compared. Piezoelectric craniotomy utilized a 0.35 mm micro saw titanium nitride coated. Outcome parameters included the detection of the "smear layer," average osteoblast count per high-power field, and residual bone matrix for bony invasiveness assessment. Parameters for meningeal and brain parenchymal invasiveness included pachymeningeal and leptomeningeal injury, gliosis, and histiocytic infiltration. Statistical significance was determined at P < 0.05. RESULTS: Results showed the Piezo group had fewer frequent smear layers (P <0.001), higher residual bone matrix (P < 0.05), and greater osteoblast counts per high-power field (P < 0.05). Additionally, the Piezo group exhibited lower rates of leptomeningeal injury, cerebral gliosis, and histiocytic infiltration (P < 0.05). CONCLUSIONS: Piezoelectric craniotomy preserves residual osteoblast viability and leptomeningeal integrity while demonstrating lower rates of thermally induced gliosis and histiocytic infiltration compared to high-speed drills. This suggests the piezoelectric osteotome's minimal invasiveness in bone, meningeal, and brain tissue.

Optimization of photothermal therapy conditions through diffusion analysis based on the initial injection radius of AuNPs.

Anticancer treatment is performed in various ways, and photothermal therapy (PTT) is gaining traction from a noninvasive treatment perspective. PTT is a treatment technique based on the photothermal effect that kills tumors by increasing their temperature. In this study, gold nanoparticles (AuNPs), which are photothermal agents, were used in numerical simulations to determine the PTT effect by considering diffusion induced changes in the distribution area of the AuNPs. The treatment effect was confirmed by varying the initial injection radius of AuNPs represented by the injection volume, the elapsed time after injection of AuNPs, and the laser intensity. The degree of maintenance of the apoptotic temperature band in the tumor was quantitatively analyzed by the apoptotic variable. Ultimately, if the initial injection radius of AuNPs is 0.7 mm or less, the optimal time to start treatment is 240 min after injection, and for 1.0 and 1.2 mm, it is optimal to start treatment when the elapsed time after injection is 90 and 30 min, respectively. This study identified the optimal treatment conditions for dosage of AuNPs and treatment start time in PTT using AuNPs, which will serve as a reference point for future PTT studies.

Finite element simulation and experimental validation of thermal damage to isolated porcine skin tissue by femtosecond laser welding.

The welding effect of the laser on skin tissue is reduced by thermal damage to skin tissue, and greater thermal damage to skin tissue caused by the laser is prevented by predicting thermal damage. In this paper, a finite element model is established for the temperature field of skin tissue scanned by a femtosecond laser to obtain the influence of laser process parameters and scanning path on the thermal damage parameters of skin tissue and the thermal damage area, and verified experimentally. The results show that the established finite element model is accurate and can accurately reflect the temperature distribution during the process of femtosecond laser welding of porcine skin tissues; used to predict the thermal damage parameters of the skin tissues and the thermal damage area; and provide guidance for the study of the femtosecond laser welding of the skin tissues process to obtain the optimal process parameters.

Comparative evaluation of thermal impact of 980nm diode laser on soft tissue using irrigation and non-irrigation systems: A histomorphometric study.

Background: Diode laser is one of the most captivating technologies in dental practice. In periodontics, when used at appropriate settings, it possesses the best properties for selective surgical and nonsurgical procedures such as subgingival calculus removal without a thermal change of the root surface, and also provides tissue surface sterilization. However, lasers always produce a certain amount of thermal damage to the soft tissues. Therefore, this study aimed to comparatively evaluate the thermal impact of 980-nm diode laser incisions, when used with irrigation versus nonirrigation systems. Materials and Methods: The study was conducted on 24 gingival tissue samples obtained from the goat's mandible and maxilla. The samples were divided into two groups of 12 samples each, and laser incisions were given in 4 power settings, using 980-nm diode laser in super short pulse mode, with and without saline irrigation. Martius Scarlet Blue staining technique was used to prepare the histological slides. Then, slides were examined under a research microscope (Olympus CX 21), and the pictures of the slides were taken by mounting the camera onto the microscope mobile mount. The microscopic images hence obtained were analyzed for the depth and width of the incisions, area of carbonization, necrosis, and reversible damage, using the Digimizer image analysis software. Results: The results of this study demonstrated that the mean incision depth was higher (592.49 ± 180.97, P < 0.05), with less carbonization (25.52 ± 29.21, P = 0.00) and less necrosis (311.63 ± 156.441, P < 0.05) in the laser incisions with irrigation, as compared to the laser incisions given without irrigation system. Conclusion: Within the limitations of this study, it can be concluded that using an irrigation system causes less collateral damage while maintaining the incising efficiency of the diode laser. Further studies with a higher sample size, controlled irrigation systems, and incision techniques are needed to evaluate the efficiency of diode lasers for the clinical explanation of the results.

A new model of electrosurgical tissue damage for neurosurgery simulation.

BACKGROUND: Bipolar hemostasis electrocoagulation is a fundamental procedure in neurosurgery. A precise electrocoagulation model is essential to enable realistic visual feedback in virtual neurosurgical simulation. However, existing models lack an accurate description of the heat damage and irreversible tissue deformation caused by electrocoagulation, thus diminishing the visual realism. This work focuses on the electrocoagulation model for neurosurgery simulation. METHOD: In this paper, a position-based dynamics (PBD) model with a bioheat transfer and damage prediction (BHTDP) method is developed for simulating the deformation of brain tissue caused by electrocoagulation. The presented BTHDP method uses the Arrhenius equation to predict thermal damage of brain tissue. A deformation model with energy and thermal damage constraints is developed to characterize soft tissue deformation during heat absorption before and after thermal injury. Visual effect of damaged brain tissue is re-rendered. RESULT: To evaluate the accuracy of the proposed method, numerical simulations were conducted and compared with commercial finite element software. The maximum normalized error of the proposed model for predicting midpoint temperature is 10.3 % and the maximum error for predicting the thermal damage is 5.4 %. The contraction effects of heat-exposed anisotropic tissues are also simulated. The results indicate that the presented electrocoagulation model provides stable and realistic visual effects, making it applicable for simulating the electrocoagulation process in virtual neurosurgery.

Analysis of physical and mechanical behaviors and microscopic mineral characteristics of thermally damaged granite.

Temperature's influence on the physical and mechanical properties of rocks is a crucial concern for the rational design of deep rock engineering structures and the assurance of their long-term stability. To systematically comprehend the impact of the evolution of mineral composition and micro characteristics on the physical and mechanical behavior of thermally damaged granite, we observed the microscopic structural defects inside the rocks with a polarizing microscope and revealed the thermal damage mechanism of granite from a microscopic perspective by combining ultrasound detection and XRD phase characteristic analysis. The results show that the physical properties of the specimens changed significantly at three characteristic temperature points: 400 °C, 800 °C, and 1000 °C. Under high temperature conditions, the diffraction intensity of all minerals in granite, except for quartz, generally decreased, and stable minerals decomposed. Albite and potash feldspar decomposed to form anorthoclase, thereby reducing the structural stability of the rock material. In addition, the peak width of various minerals decreased to varying degrees with increasing temperature. The increase in mineral volume further damaged the internal structure of the rock material while promoting the transformation from grain boundary to intergranular cracks and from intragranular cracks to transgranular cracks, ultimately forming a interconnected crack network. Thermal damage significantly reduced the longitudinal wave velocity, uniaxial compressive strength, and elastic modulus of the specimens, while the stress-strain curve relationship indicated that the specimens underwent two opposite processes of transformation from brittleness to ductility and then from ductility to brittleness. The thermal damage threshold of granite in this study was 600 °C.

Histological In Vivo Evaluation of Intense Pulsed Light Technology: Assessing the Safety on Oral Soft and Hard Tissues.

Intense pulsed light (IPL) is used for aesthetic and therapeutic purposes. According to recent literature, utilizing IPL may boost upregulation of anti-inflammatory cytokines, and downregulation of pro-inflammatory cytokines. Concerns have been raised about potential thermal damage to the soft and hard tissues in the oral cavity. Therefore, the aim of this study was to determine the safety of using IPL of various intensities in the tissues of the oral cavity. METHODS: Three adult pigs were included in the trial. The oral cavity was divided into four quadrants and projected with a wide range of IPL settings. Alveolar bone, buccal mucosa, and gingival tissue samples were taken immediately and after 24 h. In each animal, one quadrant of the jaw was left untreated and served as a control. All samples were processed and stained with H&E. RESULTS: Clinical examination showed no evidence of changes in the integrity of the examined tissues. Histological examination of the different tissues did not demonstrate significant thermal damage or changes in the characterization of the cells compared to the control tissues. CONCLUSIONS: The use of IPL in the oral cavity is safe and does not negatively affect the tissues.

Design and prediction of laser-induced damage threshold of CNT-PDMS optoacoustic transducer.

The optoacoustic transducer has emerged as a new candidate for medical ultrasound applications and attracts considerable attention. Optoacoustic diagnosis and treatment sometimes require high-intensity acoustic pressure, which is often accompanied by the problem of laser-induced damage. Addressing the laser-induced damage phenomenon from a theoretical perspective holds paramount importance. In this study, the theoretical model of laser-induced damage of the carbon nanotubes-polydimethylsiloxane (CNT-PDMS) composite optoacoustic transducer is established. It is found that this laser-induced damage belongs to thermal ablation damage. Furthermore, the correctness of this theory can be confirmed by experimental results. Most importantly, when the laser energy density is less than threshold value of laser energy density, the optoacoustic transducer can work stable for long time. These encouraging results demonstrate that this work can provide significant guidance for the exploration and utilization of optoacoustic transducers.

Thermal damage to the skin from 8.2 and 95 GHz microwave exposures in swine.

A study of burn thresholds from superficially penetrating radio-frequency (RF) energy at 8.2 and 95 GHz for swine skin was conducted. The study determined the thresholds for superficial, partial-thickness, and full-thickness burn severities after 5 seconds of exposure at power densities of 4-30 W/cm2and 2-15 W/cm2at 8.2 and 95 GHz, respectively. There were significant differences in he burn thresholds at the different severities between the two frequencies due to the large difference in energy penetration depths. Biopsies were collected from each burn site at 1, 24, 72, and 168 hr post exposure. Each sample was assessed by a burn pathologist against 20 histological factors to characterize the damage resulting from these RF overexposures. A one-dimensional, layered digital phantom that utilized realistic values for dielectric and thermal properties was used to explain some observed thresholds. The results of the heating and cooling response of the animal model and histology scores of each exposure are provided to enhance future efforts at simulation of RF overexposures and to establish damage thresholds.

Effect of high blood flow on heat distribution and ablation zone during microwave ablation-numerical approach.

Microwave ablation has become a viable alternative for cancer treatment for patients who cannot undergo surgery. During this procedure, a single-slot coaxial antenna is employed to effectively deliver microwave energy to the targeted tissue. The success of the treatment was measured by the amount of ablation zone created during the ablation procedure. The significantly large blood vessel placed near the antenna causes heat dissipation by convection around the blood vessel. The heat sink effect could result in insufficient ablation, raising the risk of local tumor recurrence. In this study, we investigated the heat loss due to large blood vessels and the relationship between blood velocity and temperature distribution. The hepatic artery, with a diameter of 4 mm and a height of 50 mm and two branches, is considered in the computational domain. The temperature profile, localized tissue contraction, and ablation zones were simulated for initial blood velocities 0.05, 0.1, and 0.16 m/s using the 3D Pennes bio-heat equation, temperature-time dependent model, and cell death model, respectively. Temperature-dependent blood velocity is modeled using the Navier-Stokes equation, and the fluid-solid interaction boundary is treated as a convective boundary. For discretization, we utilized H curl Ω elements for the wave propagation model, H 1 Ω elements for the Pennes bio-heat model, and H 1 Ω 3 × L 0 2 Ω elements for the Navier-Stokes equation, where Ω represents the computational domain. The simulated results show that blood vessels and blood velocity have a significant impact on temperature distribution, tissue contraction, and the volume of the ablation zone.

Assessment of thermal damage for plasmonic photothermal therapy of subsurface tumors.

Plasmonic photothermal therapy (PPTT) involves the use of nanoparticles and near-infrared radiation to attain a temperature above 50 °C within the tumor for its thermal damage. PPTT is largely explored for superficial tumors, and its potential to treat deeper subsurface tumors is dealt feebly, requiring the assessment of thermal damage for such tumors. In this paper, the extent of thermal damage is numerically analyzed for PPTT of invasive ductal carcinoma (IDC) situated at 3-9 mm depths. The developed numerical model is validated with suitable tissue-tumor mimicking phantoms. Tumor (IDC) embedded with gold nanorods (GNRs) is subjected to broadband near-infrared radiation. The effect of various GNRs concentrations and their spatial distributions [viz. uniform distribution, intravenous delivery (peripheral distribution) and intratumoral delivery (localized distribution)] are investigated for thermal damage for subsurface tumors situated at various depths. Results show that lower GNRs concentrations lead to more uniform internal heat generation, eventually resulting in uniform temperature rise. Also, the peripheral distribution of nanoparticles provides a more uniform spatial temperature rise within the tumor. Overall, it is concluded that PPTT has potential to induce thermal damage for subsurface tumors, at depths of upto 9 mm, by proper choice of nanoparticle distribution, dose/concentration and irradiation parameters based on the tumor location. Moreover, intravenous administration of nanoparticles seems a good choice for shallower tumors, while for deeper tumors, uniform distribution is required to attain the necessary thermal damage. In the future, the algorithm may be extended further, involving 3D patient-specific tumors and through mice model-based experiments.

Subminute thermal damage to cell types present in the skin.

INTRODUCTION: Psoriasis is characterized by an increase in the proliferation of keratinocytes and nerve fiber activity, contributing to the typical skin lesions. Pulsed Dye Laser (PDL) treatment is effective for the treatment of psoriatic lesions but its mechanism remains unclear. One hypothesis is that PDL causes thermal damage by the diffusion of heat to neighboring structures in lesional skin. There is limited information on the thermal sensitivity of these neighboring skin cells when exposed to hyperthermia for durations lasting less than a minute. Our study aimed to investigate the cell-specific responses to heat using sub-minute exposure times and moderate to ablative hyperthermia. MATERIALS AND METHODS: Cultured human endothelial cells, smooth muscle cells, neuronal cells, and keratinocytes were exposed to various time (2-20 sec) and temperature (45-70 °C) combinations. Cell viability was assessed by measuring intracellular ATP content 24 h after thermal exposure and this data was used to calculate fit parameters for the Arrhenius model and CEM43 calculations. RESULTS: Our results show significant differences in cell survival between cell types (p < 0.0001). Especially within the range of 50-60 °C, survival of neuronal cells and keratinocytes was significantly less than that of endothelial and smooth muscle cells. No statistically significant difference was found in the lethal dose (LT50) of thermal energy between neuronal cells and keratinocytes. However, CEM43 calculations showed significant differences between all four cell types. CONCLUSION: The results imply that there is a cell-type-dependent sensitivity to thermal damage which suggests that neuronal cells and keratinocytes are particularly susceptible to diffusing heat from laser treatment. Damage to these cells may aid in modulating the neuro-inflammatory pathways in psoriasis. These data provide insight into the potential mechanisms of PDL therapy for psoriasis and advance our understanding of how thermal effects may play a role in its effectiveness.

Effect of radius-dependent diffusion behavior of various gold nanoparticles on photothermal therapy.

Among the various anti-cancer treatments, photothermal therapy (PTT) is gaining traction as it is a non-invasive treatment. PTT is a treatment technique involving the use of a laser to raise the temperature of the target tumor until it dies. In this study, the effects of PTT under various conditions of squamous cell carcinoma (SCC) occurring in the skin were numerically analyzed and optimized. Gold nanoparticles (AuNPs) with different radii were injected into the center of the SCC. Subsequently, the diffusion behavior of the AuNPs was analyzed to calculate the distribution area of the AuNPs that changed over time. Furthermore, at each elapsed time point after injection, the temperature distribution in the tissue was calculated, as treatment was performed using varying laser intensities. The diffusion coefficient of AuNPs was calculated using the Stokes-Einstein equation, and diffusion behavior of AuNPs in biological tissues was analyzed using the convection-diffusion equation. Additionally, temperature distribution was analyzed using the Pennes bioheat equation. The effect of PTT under each condition was quantitatively analyzed using apoptotic variables. As a result, As the radius of AuNPs increased, the optimal treatment start time was derived as 2 h, 8 h, 8 h, and 12 h, respectively, and the laser intensity at that time was derived as 0.44 W, 0.46 W, 0.42 W, and 0.42 W, respectively. The study findings will provide reference for the optimization of the efficacy of PTT.

Analysis of Optimal Treatment Starting Time for Photothermal Therapy Through Analysis of Diffusion Behavior of Gold Nanoparticles.

Introduction: Due to its distinct advantage of non-invasive application in treatment, photothermal therapy (PTT) is being studied by many researchers to reduce the need for surgical incisions. It is characterized by the injection of nanoparticles into biological tissue as photothermal agents (PTAs) which diffuse within the tissue. In this study, the diffusion behavior of various doses of gold nanoparticles (AuNPs) injected into tumor tissues is analyzed and the effectiveness of PTT at each elapsed time after injection is confirmed by numerical analysis. Methods: The diffusion behavior of AuNPs within biological tissues is assessed using the convection-diffusion equation, while the temperature distribution is determined using the Pennes bioheat transfer equation. In addition, the effect of the diffusion behavior of AuNPs on the effectiveness of PTT is quantitatively confirmed by analyzing the temperature distribution in the medium through the apoptotic variable. Numerical simulation parameters are selected with doses ranging from 100 to 400 µg/mL, elapsed time after injection from 1 min to 24 h, and laser power ranging from 0 to 1 W. Results: After evaluating PTT's efficacy in every situation, it was discovered that a dosage of 100-300 µg/mL produced the best therapeutic result, with the highest impact occurring 12 hours after injection. In contrast, when the dosage was 400 µg/mL, the highest therapeutic effect was achieved after 18 hours post-injection. Additionally, it was discovered that the ideal laser power at each injection dose was 0.22, 0.14, 0.12, and 0.12 W, respectively. Conclusion: The conditions required to achieve the optimal treatment effect at each dosage, presented here, are expected to accelerate the commercialization of PTT.

Numerical study of the induction of intratumoral apoptosis under microwave ablation by changing slot length of microwave coaxial antenna.

Recent advances in technology have led to an increase in the detection of previously undetected deep-located tumor tissue. As a result, the medical field is using a variety of methods to treat deep-located tumors, and minimally invasive treatment techniques are being explored. In this study, therapeutic effect of microwave ablation (MWA) on tumor generated inside liver tissue was analyzed through numerical analysis. The distribution of electromagnetic fields in biological tissues emitted by microwave coaxial antenna (MCA) was calculated through the wave equation, and the thermal behavior of the tissue was analyzed through the Pennes bioheat equation. Among various treatment conditions constituting MWA, tumor radius and the slot length inside the MCA were changed, and the resulting treatment effect was quantitatively confirmed through three apoptotic variables. As a result, each tumor radius has optimal power condition for MWA, 2.6W, 2.4W, and 3.0W respectively. This study confirmed optimal therapeutic conditions for MWA. Three apoptotic variables were used to quantitatively identify apoptotic temperature maintenance inside tumor tissue and thermal damage to surrounding normal tissue. The findings of this study are expected to serve as a standard for treatment based on actual MWA treatment.