Coagulation Zone Research Articles

Ex vivo vaporization performance study of human prostate tissue using in-house designed thulium fiber laser

Introduction: Laser technologies including thulium, Holmium: Yttrium aluminum garnet (Ho: YAG), Potassium-titanyl-phosphate and diode laser have been explored in recent years for the treatment of benign prostatic hyperplasia. These thermal modalities impart their effect through ablative and coagulative mechanisms of action. Although Ho: YAG laser is a gold standard clinical tool in urology, its properties are not sufficient for cutting or coagulation of prostatic tissue. Thulium: YAG laser is a promising alternative laser but with limitations. The recent technological advancements in thulium fiber laser (TFL) provide various advantages along with a compact system for urosurgical applications. This paper depicts the work done in initial validation of an in-house designed TFL in ex vivo vaporization and vaporesection of human prostatic tissue. Comparison of its ablation rate and coagulation zone was done with the existing laser systems. Methods: An in-house designed TFL having maximum continuous wave (CW) power level of 70 W at 1.94 mm optical wavelength had been used for the ex vivo experiment on human prostatic tissue. The rate of tissue vaporization and zone of thermal coagulation were assessed. Results: The in-house made (CSIR-CGCRI, Kolkata, India) CW TFL used at power of 60 W at 1.94 mm was capable of providing tissue vaporization rate of 0.13–0.45 g/min with a thermal coagulation zone of 100 mm. Conclusions: In our study, the TFL was efficient in vaporization, vaporesection, and coagulation of the prostatic tissue under controlled circumstances. Compared to the existing laser systems, the TFL could be a new alternative in Endourology.

Computer Simulations of Dual-Antenna Microwave Ablation and Comparison to Experimental Measurements

Single-antenna microwave ablation (MWA) is mainly used to treat small tumors less than 3 cm in diameter. To obtain a larger coagulation zone in a single ablation, a dual-antenna ablation approach was proposed. A three-dimensional finite element method (FEM) simulation model of parallel dual-antennas was developed. Ex vivo experiments at 50 W for 8 min were performed to verify the model. Both the temperature changes in tissue and the size of the coagulation zone were recorded. The effects of dual-antenna spacing, heating power, and blood perfusion on the coagulation zone were analyzed. Fifteen experiments were carried out. The errors between the mean measurements and simulated results at the set temperature points were 1.08 °C, 0.95 °C, and 2.1 °C, respectively. For the same conditions, the blood perfusion of 1.0, 1.5, and 3.0 kg/(m3·s) can result in a reduction in the coagulation volume by 18.4%, 25.4%, and 42.5%. As the spacing increased, the coagulation zone of each antenna started to fuse together later and the resulting integral coagulation zone became larger. Dual-antenna MWA is expected to be used for the treatment of tumors larger than 5 cm in diameter.

Tissue thermal effect during lithotripsy and tissue ablation in endourology: a systematic review of experimental studies comparing Holmium and Thulium lasers.

We looked into the Thulium: yttrium-aluminum-garnet (TM:YAG), Thulium Fibre laser (TFL) and Holmium: yttrium-aluminum-garnet (Ho:YAG) thermal laser tissue effect during lithotripsy and tissue ablation. We performed a PubMed, Scopus, EMBASE, and Cochrane Central Register of Controlled Trials (CENTRAL) search. During lithotripsy, the Ho:YAG generated temperatures from 24 to 68.7°C at powers < 20W, the Tm:YAG from 43.7°C at 30W to 68°C at powers < 20W, and the TFL from 33 to 40.46°C. During ablation, the Ho:YAG and continuous wave (cw) Tm:YAG tissue incision depths ranged from 0.08 to 2.26mm, and from 0.28 to 3.22mm. The Ho:YAG and Tm:YAG vaporization areas ranged from 0.044 to 0.078 mm2 and from 0.050 to 0.078 mm3 and their coagulation zones were 0.075 mm2 and 0.125 mm3 respectively. Ho:YAG and Tm:YAG laser damage zones ranged from 0.093 to 2.6 mm3 and from 0.207 to 0.98 mm3 respectively. The TFL incision depth ranged from 0.04 to 5.7mm. The cw and SuperPulsed (SP) vaporization volumes ranged from 8 to 28.2 mm3/s and from 4 to 11 mm3/s. TFL coagulation depth and coagulation zone ranged from zero to 1.1mm, 2.2 to 5.1 mm3 in SP mode and from 7.7 to 18.1 mm3 in cw mode. During lithotripsy all lasers caused similar temperature changes and had a safe temperature profile at < 40W. During tissue ablation, Ho:YAG has a deeper incision depth, while cwTm:YAG and cwTFL have broader coagulation and total laser areas.

Microwave ablation of the lung: Comparison of 19G with 14G and 16G microwave antennas in ex vivo porcine lung.

Percutaneous image-guided thermal ablation has an increasing role in the treatment of primary and metastatic lung tumors. Although microwave ablation (MWA) has emerged advantageous as a new ablation technology, more research is needed to improve it. This study aims to investigate the ablation zone of three microwave antennas in ex vivo porcine lung. In the ex vivo standard model and porcine lung model, MWA was performed in three power output settings (50 W, 60 W, and 70 W) for 3, 6, 9, and 12 min using three microwave antennas, with outer diameter of 1.03 mm (19G), 1.6 mm (16G), and 2.0 mm (14G). A total of 108 and 216 sessions were performed (3 or 6 sessions per time setting with the 14G, 16G, and 19G microwave antennas). After the MWA was complete, we evaluated the shape and extent of the coagulation zone and measured the maximum long-axis (along the needle axis; length [L]) and maximum short-axis (perpendicular to the needle; diameter [D]) of the ablation zones using a ruler; subsequently, the sphericity index (L/D) was calculated. The sphericity index can be simplified as long-axis/short-axis. In the ex vivo standard model study, the long- and short-axis diameters and sphericity indices were not statistically different between the 14G, 16G, and 19G groups. In the ex vivo porcine lung study, the long- and short-axis diameters did not differ statistically between the 14G, 16G, and 19G groups (P < 0.05 each). The sphericity index for the 19G microwave antenna was higher than the sphericity indices for the 14G and 16G microwave antennas (P < 0.05); however, the index for the 14G microwave antenna was not statistically different than that for the 16G microwave antenna (P > 0.05). The ablation zone of the 19G antenna was the same as those of the 14G and 16G antennas in vitro. Thus, the 19G antenna may reduce the incidence of complications in lung tumor ablation.

Comparison of two radiofrequency-based hemostatic devices: saline-linked bipolar vs. cooled-electrode monopolar

Purpose To characterize the coagulation zones created by two radiofrequency (RF)-based hemostatic devices: one comprised an internally cooled monopolar electrode and the other comprised externally irrigated bipolar electrodes (saline-linked). Materials and methods RF-induced coagulation zones were created on ex vivo and in vivo porcine models. Computer modeling was used to determine the RF power distribution in the saline-linked device. Results Both external (irrigation) and internal cooling effectively prevented tissue sticking. Under ex vivo conditions in ‘painting’ application mode, coagulation depth increased with the applied power: 2.8 − 5.6 mm with the 3-mm monopolar electrode, 1.6 − 6.0 mm with the 5-mm monopolar electrode and 0.6 − 3.2 mm with the saline-linked bipolar electrodes. Under in vivo conditions and using spot applications, the 3-mm monopolar electrode created coagulation zones of similar depth to the saline-linked bipolar electrodes (around 3 mm), while the 5-mm monopolar electrode created deeper coagulations (4.5 − 6 mm) with less incidence of popping. The presence of saline around the saline-linked bipolar electrodes meant that a significant percentage of RF power (50 − 80%) was dissipated by heating in the saline layer. Coagulation zones were histologically similar for all the tested devices. Conclusions Both external (irrigation) and internal cooling in hemostatic RF devices effectively prevent tissue sticking and create similar coagulation zones from a histological point of view. Overall, saline-linked bipolar electrodes tend to create shallower coagulations than those created with an internally cooled monopolar electrode.

Correlations between B-mode ultrasound image texture features and tissue temperatures in hyperthermia.

PurposeThe noninvasive monitoring of mild hyperthermia or thermal ablation is important to guarantee therapeutic safety and efficacy. The potential of ultrasound B-mode image texture features in monitoring temperature or coagulation zones studied in this article.Materials and methodsThe experiments carried out on eighteen in vitro porcine liver samples heated from 20°C to 60°C in the water bath. The ultrasound radiofrequency signal at different temperature collected to reconstruct B-mode ultrasound images. The texture features based on gray level histogram (GLH), gray level co-occurrence matrix (GLCM), and gray level-gradient co-occurrence matrix (GGCM) extracted, respectively. Accordingly, we analyze the correlations between these texture features and temperature based on the experiment results.ResultsThe results showed that five texture feature parameters closely related to temperature, including mean gray scale of GLH, homogeneity of GLCM, hybrid entropy, inverse difference moment, and correlation of GGCM. Some of these feature parameters have correlation coefficients larger than 0.9 within the temperature range of 20°C to 60°C.ConclusionsThe above-mentioned five feature parameters expected to apply for noninvasive monitoring of MH or TA.

Thulium Fiber Laser Behavior on Tissue During Upper- and Lower-Tract Endourology.

To present the latest evidence on thulium fiber laser (TFL) effects on tissue, during lithotripsy and ablation, emphasizing on generated temperatures, thermal damage thresholds, incision depths, areas of coagulation, and laser damage. Lasers are frequently utilized during endoscopic treatment of different urological conditions. The holmium:yttrium-aluminum-garnet (Ho:YAG) is most frequently used for various types of stones and soft tissue. The TFL has been recently introduced, offering several advantages. However, its activity on tissue during upper and lower tract endourology is poorly understood. At equivalent power settings, TFL and Ho:YAG generate similar temperature changes during lithotripsy. TFL has a shallow incision depth during tissue ablation. Compared to SP TFL, (cw) TFL results in a broader coagulation zone, whereas SP TFL gives of Ho:YAG-similar incision, and (cw) TFL offers a quick, precise cut with more carbonization.

The Effect of Trimetazidine on Diathermy-related Thermic Injury of the Rat Liver.

Owing to new oncotherapy modalities, the importance of an R0 resection decreased in the last decade; however, liver metastasis of colorectal cancer significantly decreases survival. Furthermore, to prevent cardiovascular disease, more and more patients are treated with anti-ischemic drugs, which may influence oncologic treatments in such patients. This study aimed to examine the effect of Trimetazidine on liver surface injury after spray diathermy. We performed standard liver resections with resection-margin spray coagulation in 36 rats on both liver lobes. In all procedures, a Pringle maneuver was performed on the right lobe, while on the left lobe, no vessel occlusion was applied. Half of the animals were on Trimetazidine therapy. In 12 animals, histologic samples were taken immediately after operation, while 12 animals were terminated 1 week later, and the remaining 12 animals 3 weeks later. After standard HE staining, histologic analysis was performed. When diathermy was used, a coagulation zone appeared. Destruction was slightly wider in case of Trimetazidine therapy (745.75 vs. 680.04 μm). In cases of 1-week-surviving animals, a necrotic zone was observed under the coagulated tissue, and a fibrotic zone appeared after 3 weeks. In TMZ medicated animals, the destruction zone was significantly thinner (645.08 vs. 893.76 μm; p<0.001) and the necrosis zone showed the same difference (2,430.05 vs. 3,238.45 μm; p<0.001). Administration of Trimetazidine can reduce the extent of thermic necrosis. Furthermore, a great effort should be applied to achieve R0 resection in patients on anti-ischemic therapy.

Application of biophantomes to evaluate the thermal effects of laser radiation with wavelengths of 970 nm and 1560 nm under different exposure modes

Laser interstitial hyperthermia is an actively developing direction in intracerebral tumor surgery. The paper presents thermal effects in polyacrylamide biophantoms with bovine albumin and citrated blood under laser irradiation at 970 nm and 1560 nm. For laser irradiation, a surgical two-wave apparatus manufactured by IRE Polis was used. The phantom was irradiated through a quartz optical fiber 400 µm in diameter with an end exit. The result of irradiation of the phantom was its coagulation zone, which was visualized with a FLUM-LL fluorescent organoscope. Thermometry was carried out with a FLIRONE PRO for IOS thermal imager and a T-8 digital thermograph based on a laptop with thermal sensors placed in a phantom. The use of irradiation with a power of not more than 2 W in the coagulation mode, with a total energy dose of up to 120 J, made it possible to achieve a smooth rise in temperature to 88.0 °C. The dimensions of the coagulation zone under irradiation with a wave of 1560 nm were always larger than under irradiation with a wave of 970 nm, although the difference was not statistically significant (p=0,41). Thus, the average coagulation spot area for 970 nm radiation was 43.2 (39.3 – 47.1) mm 2 , and for 1560 nm – 99.4 (56.5-141.3) mm 2 . With total irradiation with two waves, the coagulation zone was larger if the radiation power of 1560 nm prevailed. When irradiated with a wave of 970 nm, the coagulation zone partially propagates posteriorly from the tip of the optical fiber, and 1560 nm coagulates the phantom anteriorly. The results obtained are of practical importance for laser hyperthermia of intracerebral tumors.

Temperature control and intermittent time-set protocol optimization for minimizing tissue carbonization in microwave ablation

Purpose The charring tissue formation in the ablated lesion during the microwave ablation (MWA) of tumors would induce various unwanted inflammatory responses. This paper aimed to deliver appropriate thermal dose for effective ablations while preventing tissue carbonization by optimizing the treatment protocol during MWA with the set combinations of temperature control and pulsed microwave energy delivery. Material and methods The thermal phase transition of ex vivo porcine liver tissues were recorded by differential scanning calorimetry (DSC) to determine the temperature threshold during microwave output control. MWA was performed by an in-house built system with the ease of microwave output parameter adjustment and real-time temperature monitoring. The effects of continuous and pulsed microwave deliveries as well as various intermittent time-set of MWA were evaluated by measuring the dimensions of the coagulation zone and the carbonization zone. Results The DSC scans demonstrated that the ex vivo porcine liver tissues have been in a state of endothermic heat during the heating process, where the maximum absorbed heat occurred at the temperature of 105 °C ± 5 °C. The temperature control during MWA resulted in effective coagulative necrosis while preventing tissue carbonization, after setting 100 °C as the upper threshold temperature and 60 °C as the lower threshold. Both the numerical simulation and ex vivo experiments have shown that, upon the optimization of the time-set parameters in the periodic intermittent pulsed microwave output, the tissue carbonization was significantly diminished. Conclusion This study developed a straight-forward anti-carbonization strategy in MWA by modulating the pulsing mode and intermittent time. The programmed protocols of intermittent pulsing MWA have demonstrated its potentials toward future expansion of MWA technology in clinical application.

Numerical study on the effect of bifurcation vessel parameters on microwave ablation of lung tissue

ABSTRACT Background: In order to study the effect of bifurcation vessels parameters on the temperature field and coagulation zone of microwave ablation on lung tissue. Methods: The finite element method was used to establish the simulation model. The angle of bifurcation vessel model was 60°. The position of the antenna and the main blood vessel are parallel, and the distance between them was 5, 10 and 15 mm, respectively. Temperature field distribution was obtained at 2450 MHz, 50 W and 300 s. The blood flow velocity was set to 0.1 and 0.2 m/s. Results: The results showed when the antenna was 5 mm away from the bifurcation vessel and the velocity was 0.1 m/s, the position of x = 8.4 mm achieved the complete necrosis at 220 s, while the fraction of necrotic tissue at the symmetry point x = 1.6 mm was 0.2 at 300 s. For the distance was 10 mm and the velocity was 0.1 m/s, the fraction of necrotic tissue at x = 3 mm that near the bifurcation vessel was 0.53 and was 0.69 at the symmetry point x = 17 mm. When the antenna is 15 mm away from the vessel, the fraction of necrotic tissue of symmetrical points on both sides of the antenna obtained after ablation were the same. Conclusions: The distance between the antenna and the bifurcation vessel over 15 mm, the blood flow has no effect on the coagulation zone. Besides, the distance between bifurcation vessel and antenna possesses a greater influence on the temperature distribution and coagulation zone than the blood flow velocity.

Visualization of energy-based device-induced thermal tissue alterations using bimodal ex-vivo confocal microscopy with digital staining. A proof-of-concept study.

Ex-vivo confocal microscopy (EVCM) enables examination of tissue alterations immediately after treatment with energy-based devices (EBDs). This proof-of-concept study aimed to describe EBD-induced tissue effects in ex-vivo porcine skin after treatment with microneedle radiofrequency (MNRF) and ablative fractional CO2 -laser (AFL) using EVCM. Ex-vivo porcine skin was treated with MNRF and AFL. Three cryosections from each intervention were stained with acridine orange (AO) and scanned with EVCM. Reflectance confocal microscopy (RCM, 638nm) and fluorescence confocal microscopy (FCM, 488nm) images were captured and evaluated individually, after image fusion, and after digital hematoxylin and eosin (H&E) staining. Bimodal EVCM was able to visualize EBD-induced thermal alterations in porcine skin. In RCM mode, the full width and depth of the vertically aligned microscopic treatment zones (MTZs) were displayed with clear demarcation to surrounding intact skin. In FCM mode, the ablation of the epidermis after AFL was prominent in contrast with the almost intact epidermis observed in MNRF treated skin. In fusion mode, fluorescence signal from AO marked the surrounding coagulation zone (CZ) from both interventions, with enhanced discrimination between ablation and coagulation. Digitally H&E-stained images closely resembled conventional histopathology but proved superior in terms of visualization of the CZ. Bimodal EVCM with digital H&E-staining facilitates the identification and qualitative evaluation of thermal alterations induced by treatment with EBD. By providing high-resolution images comparable to standard histology, EVCM is a useful tool in the research and development of EBD to visualize and evaluate device-tissue interactions.

Ex Vivo Exposure to Soft Biological Tissues by the 2-μm All-Fiber Ultrafast Holmium Laser System

We present the results of ex vivo exposure by an ultrafast all-fiber Holmium laser system to porcine longissimus muscle tissues. A simple Ho-doped laser system generated ultrashort pulsed radiation with less than 1 ps pulse width and a repetition rate of 20 MHz at a central wavelength of 2.06 μm. Single-spot ex vivo experiments were performed at an average power of 0.3 W and different exposure times of 5, 30 and 60 s, varying the total applied energy in the range of 1.5–18 J. Evaluation of laser radiation exposure was performed according to the depth and diameter of coagulation zones, ablation craters and thermal damage zones during the morphological study. Exposure by ultrashort pulsed radiation with an average power of 0.3 W showed destructive changes in the muscle tissue after 5 s and nucleation of an ablative crater. The maximum ablation efficiency was about 28% at the ablation depth and diameter of 180 μm and 500 μm, respectively. The continuous-wave radiation impact at the same parameters resulted only in heating of the near-muscular tissue, without ablation and coagulation traces. Exposure to tissue with an average power at 0.3 W of ultrashort pulsed radiation led, within 30 and 60 s, to similar results as caused by 0.5 W of continuous-wave radiation, although with less carbonization formation.

Effects of water cooling on laser-induced thermal damage in rat hepatectomy.

PurposeHigh‐powered lasers are commonly used for tissue resection in surgeries, including liver resection, medically known as hepatectomy; however, such lasers inevitably induce thermal damage that causes postoperative complications. This study aims to explore the effects of water cooling and different laser output modes on laser‐induced thermal damage during hepatectomy.MethodsTo avoid the influence of superposition, a 980‐nm diode laser was used for a single‐point hepatectomy. Eighteen Sprague–Dawley rats were used to explore the effects of water cooling and different laser output modes. A constant energy 10‐J laser was used to cut the liver tissue with a power of 10 W and time of 1 second. The rats were randomly divided into six groups. The first three groups were assigned as test subjects for different laser output modes. Group 1 was operated with a continuous laser output for a duration of 1 second. Groups 2 and 3 were operated with a pulsed laser output for a duration of 1 second and a pulse width of 0.5 and 0.25 seconds, respectively. Groups 4, 5, and 6 were assigned for the water cooling test. Water cooling was performed based on the parameters of the first three groups. Medical saline (0.9% NaCl) was used for water cooling. The main observation indicators were resection efficiency and thermal damage, including the area of the thermal damage zone. Resection efficiency is calculated by dividing the resection area by the total thermal damage area.ResultsIn the three water cooling groups, the area of the resection, carbonized, sub‐boiling coagulated, and total thermal damage zones were 0.0677, 0.00, 1.7293, and 2.2982 mm2 in Group 4; 0.0465, 0.00, 1.3205, and 1.8414 mm2 in Group 5; and 0.0565, 0.00, 1.4301, and 1.9650 mm2 in Group 6, respectively. Compared with the first three groups, the water cooling groups exhibited significantly reduced thermal damage areas of in the carbonized, sub‐boiling coagulated, and total thermal damage zones (p < 0.001 for all). In addition, there was no statistical difference in the resection area, vacuolated area, and resection efficiency. Furthermore, there was no statistical difference in the area of each thermal damage zone between the continuous and pulsed output groups. The resection efficiencies were 4.82%, 3.34%, 3.73%, 3.93%, 3.36%, and 3.01% in Groups 1 to 6, respectively. Moreover, there was no statistical difference (p > 0.05) in the resection efficiencies.ConclusionWater cooling can reduce the total laser‐induced thermal damage area and prevent tissue carbonization. Therefore, this cooling method can be used as a simple and safe strategy for controlling thermal damage during hepatectomy.

Ablative effect of the interstitial laser setting in the human placental model.

To assess the impact of laser power and time on interstitial ablation generated by neodymium-doped yttrium aluminium garnet (Nd:YAG) and diode laser in the human placental model. The experiment was carried out in a simulation model of interstitial laser ablation on ex-vivo placental tissue. One-hundred and forty-four pieces of fresh placentae were interstitially ablated with Nd:YAG or diode laser at various power (15, 20, 25, 30 W)-time (5, 10, 15 s) combinations. The ablation tissues were evaluated using both sonographic and histopathologic measurements. Laser generator, power, and time significantly affected the ablation size (p < 0.001). The coagulation zone continuously increased with extending time at the power of 15, 20, and 25 W. When adjusting to the power of 30 W, increased time from 10to 15 s did not induce the larger coagulation diameter. The maximal diameter was obtained at the laser power of 20 W for 15 s. The ablation from the diode laser was greater than that from Nd:YAG laser. The sonographic evaluation overestimated the ablation size by an average of 24%. Diode laser destroys greater tissue than Nd:YAG laser. Different power settings of interstitial laser ablation produce diverse patterns of correlation between laser time and coagulation size.

Review of Lasers and Energy-Based Devices for Skin Rejuvenation and Scar Treatment With Histologic Correlations.

Lasers and energy-based devices (EBD) are popular treatments for skin rejuvenation and resurfacing. Achieving desired outcomes and avoiding complications require understanding the effects of these devices at a histologic level. Currently, no comprehensive review summarizing the histologic effects of laser and energy-based treatments exists. To describe how lasers and EBD alter skin histology and improve the overall understanding of these devices. A PubMed search was conducted for studies with histologic analysis of fractional picosecond laser, fractional radiofrequency microneedling, nonablative lasers, and ablative lasers. Fractional picosecond lasers induce intraepidermal and/or dermal vacuoles from laser-induced optical breakdown. Fractional radiofrequency microneedling delivers thermal energy to the dermis while sparing the epidermis, making it safer for patients with darker skin phototypes. Fractional nonablative lasers induce conical zones of coagulation of the epidermis and upper dermis. Ablative lasers vaporize the stratum corneum down to the dermis. Traditional ablative lasers cause diffuse vaporization while fractional ablative lasers generate columns of tissue ablation. Lasers and EBD are effective for skin resurfacing and rejuvenation and have different mechanisms with disparate targets in the skin. Safe and effective use of devices requires understanding the histologic laser-tissue interaction.

Modeling and ex vivo experimental validation of liver tissue carbonization with laser ablation

ObjectiveThe purpose of this study was to model the process of liver tissue carbonization with laser ablation (LA). MethodsA dynamic heat source model was proposed and combined with the light distribution model as well as bioheat transfer model to predict the development of tissue carbonization with laser ablation (LA) using an ex vivo porcine liver tissue model. An ex vivo laser ablation experiment with porcine liver tissues using a custom-made 1064 nm bare fiber was then used to verify the simulation results at 3, 5, and 7 W laser administrations for 5 min. The spatiotemporal temperature distribution was monitored by measuring the temperature changes at three points close the fiber during LA. Both the experiment and simulation of the temperature, tissue carbonization zone, and ablation zone were then compared. ResultsFour stages were recognized in the development of liver tissue carbonization during LA. The growth of the carbonization zone along the fiber axial and radial directions were different in the four stages. The carbonization zone along the fiber axial direction (L2) grew in the four stages with a sharp increase in the initial period and a minor increase in Stage 4. However, the change in the carbonization zone along the fiber radial direction (D2) increased dramatically (Stage 1) to a long-time plateau (Stages 2 and 3) followed by a slow growth in Stage 4. An acceptable agreement between the computer simulation and ex vivo experiment in the temperature changes at the three points was found at all three testing laser administrations. A similar result was also obtained for the dimensions of coagulation zone and ablation zone between the computer simulation and ex vivo experiment (carbonization zone: 2.99± 0.10 vs. 2.78 mm2, 67.39± 0.09 vs. 63.53 mm2, and 90.53± 0.11 vs. 85.15 mm2; ablation zone: 68.95± 0.28 vs. 65.29 mm2, 182.11± 0.24 vs. 213.81 mm2, and 244.80± 0.06 vs. 251.79 mm2 at 3, 5, and 7 W, respectively). ConclusionThis study demonstrates that the proposed dynamic heat source model combined with the light distribution model as well as bioheat transfer model can predict the development of liver tissue carbonization with an acceptable accuracy. This study contributes to an improved understanding of the LA process in the treatment of liver tumors.

Preclinical evaluation of a clinical prototype transrectal diffuse optical tomography system for monitoring photothermal therapy of focal prostate cancer.

.Significance: Our work demonstrates in preclinical models that continuous-wave transrectal diffuse optical tomography (TRDOT) can be used to accurately monitor photothermal therapy (PTT) and, in particular, the progression of the photocoagulation boundary toward the rectum. When used in patients, this should prevent rectal damage during PTT, thereby achieving maximum treatment efficacy while ensuring safety, using a technology platform suitable for wide dissemination.Aim: We aim to validate that TRDOT measurements analyzed using a shape-based image-reconstruction algorithm (SBDOT) allow localization of the photocoagulation boundary during PTT within toward the rectum in the transverse plane.Approach: TRDOT measurements were performed in tissue-simulating phantoms, ex vivo tissues, and an in vivo canine prostate model. The accuracy and sensitivity of reconstructing the size and location of the coagulation zone were determined, based on changes in the tissue absorption and reduced scattering coefficients upon photocoagulation. The reconstruction also yields the native and coagulated tissue optical properties.Results: The TRDOT measurements and SBDOT reconstruction algorithm were confirmed to perform sufficiently well for clinical translation in PTT monitoring, recovering the location of the coagulation boundary within compared to the true value as determined by direct visualization postexcision and/or MRI.Conclusions: Implementing previously described TRDOT instrumentation and SBDOT image reconstruction in different tissue models confirms the potential for clinincal translation, including required refinements of the system and reconstruction algorithm.

Methods of monitoring thermal ablation of soft tissue tumors - A comprehensive review.

Thermal ablation is a form of hyperthermia in which oncologic control can be achieved by briefly inducing elevated temperatures, typically in the range 50-80°C, within a target tissue. Ablation modalities include high intensity focused ultrasound, radiofrequency ablation, microwave ablation, and laser interstitial thermal therapy which are all capable of generating confined zones of tissue destruction, resulting in fewer complications than conventional cancer therapies. Oncologic control is contingent upon achieving predefined coagulation zones; therefore, intraoperative assessment of treatment progress is highly desirable. Consequently, there is a growing interest in the development of ablation monitoring modalities. The first section of this review presents the mechanism of action and common applications of the primary ablation modalities. The following section outlines the state-of-the-art in thermal dosimetry which includes interstitial thermal probes and radiologic imaging. Both the physical mechanism of measurement and clinical or pre-clinical performance are discussed for each ablation modality. Thermal dosimetry must be coupled with a thermal damage model as outlined in Section 4. These models estimate cell death based on temperature-time history and are inherently tissue specific. In the absence of a reliable thermal model, the utility of thermal monitoring is greatly reduced. The final section of this review paper covers technologies that have been developed to directly assess tissue conditions. These approaches include visualization of non-perfused tissue with contrast-enhanced imaging, assessment of tissue mechanical properties using ultrasound and magnetic resonance elastography, and finally interrogation of tissue optical properties with interstitial probes. In summary, monitoring thermal ablation is critical for consistent clinical success and many promising technologies are under development but an optimal solution has yet to achieve widespread adoption.

Effects of taurine and apocynin on the zone of stasis

BackgroundAmong the zones of coagulation, hyperemia and stasis that occur in the burned area, the most intense metabolic process and the highest sensitivity to recovery with treatment is the zone of stasis.This metabolic process is related to how well the tissues in the zone of stasis can cope with oxidative stress. If the tissues in the zone of stasis are saved, the burn area will potentially heal faster and with less scar. In this study, we examined the effects of taurine amino acids and apocynin molecules on saving the tissues in the burn zone of stasis. MethodsThe study was conducted with 48 rats. The burn zone of stasis was created according to the pattern previously described in the literature as comb burn model. In the 21-day study, biopsies were taken for histological examination on the 3rd, 7th and 21st days of the study. In addition, macroscopic photographic analysis was performed. Biopsies were taken for biochemical analysis on the 21st day. Histologically, inflammation, reepithelialization, and collagenization were evaluated, and the CD34 immunoreactivity was analysed. Biochemically, CAT, SOD, tGSH, TAS, TOS, MDA and PPC values were determined. ResultsIn the histological examination, on the 3rd, 7th and 21st days, inflammation was found to be reduced in the groups given taurine and apocynin on the 3rd day. On the 7th day, better reepithelialization and collagenization were observed in the group given taurine. Significant reepithelialization, collagenization and hair follicle development were observed in the groups given taurine and apocynin on the 21st day. In the biochemical analysis, the effects of apocynin on antioxidant enzymes were determined to be prominent. While we found no significant difference on the 3rd and 7th days in the photographic analysis, taurine and apocynin were observed to act synergistically on the 21st day and significantly reduced the burned areas. ConclusionOn the 3rd day, taurine and apocynin prevented inflammation, the effects of taurine in the zone of stasis in the early period (7th day) are more pronounced, the effect of apocynin on antioxidant enzymes is more pronounced. In the late period (21st day), taurine and apocynin were found to be more effective in saving the zone of stasis by creating a synergistic effect.