Tissue Ablation Research Articles

Towards Formulation of Highly Acidic Active Ingredients: Development of Clinically Effective Concentrated Trichloroacetic Acid Gel for Wart Management.

Common warts are benign skin lesions caused by the human papillomavirus. Although they are usually not harmful, they can cause pain, depending on their location. While many modalities are available for treatment of warts, none is a gold standard, and many are not affordable and/or have suboptimal outcomes. Trichloroacetic acid (TCA) is a chemical tissue-destroying agent used as a highly concentrated solution for wart management. While available and efficient, it is difficult to handle as the solution spreads to tissue surrounding the wart causing pain and burning. Hence, we developed a new polymer-based gel of high TCA content (100% w/v). Gels were formed successfully as hydroxyethyl cellulose (HEC) and chitosan were used to impart viscosity and bioadhesion. Formulae of different concentrations were tested for their physical properties, and the optimal formulation was selected for clinical evaluation. A combination of 3% HEC and 2% chitosan provided optimal viscosity and limited water content and have acceptable stability. The efficacy and safety of the biweekly application of TCA gel were evaluated in 30 patients. The clinical study revealed gel's efficacy and tolerability; half of the patients showed a complete cure, and 90% showed improvement within 6weeks. Only 10-12% of the patients reported side effects. In summary, transforming TCA solution into a gel enabled its application and handling in a practical manner by physicians and patients alike, while maintaining its efficacy as a tissue-destroying agent. Moreover, it is economic and easy to apply, rendering it a promising formulation for similar conditions requiring controlled tissue ablation.

Intraluminal endoscopic complex approach in the treatment of a patient with adenoma of the major duodenal papilla, choledocholithiasis and stricture of the terminal common bile duct

Introduction. Adenomas of the major duodenal papilla are benign neoplasms, but due to their high tendency to malignancy, they must be removed. At present, minimally invasive methods of operations are increasingly being considered as an alternative to surgical interventions, while cases of a combination of a neoplasm of the major duodenal papilla with choledocholithiasis and bile duct strictures are of particular difficulty in endoscopic treatment. Clinical case. A 62-year-old patient underwent complex endoscopic treatment at the Vishnevsky National Research Medical Center for Surgery about adenoma of the major duodenal papilla type IV, extending to the walls of the duodenum and the terminal section of the common bile duct, in combination with choledocholithiasis and cicatricial stricture of the common bile duct. Results. The patient successfully applied a complex approach of minimally invasive treatment in the amount of endoscopic lithoextraction, fragmentary removal of adenoma of the major duodenal papilla with intraductal high-frequency electrosurgical ablation of residual adenomatous tissue and subsequent staged biliary stenting for cicatricial stricture of the common bile duct, as well as stenting of the main pancreatic duct to prevent post-manipulation pancreatitis. Discussion. An integrated approach in the treatment of a patient with adenoma of the major duodenal papilla IV, choledocholithiasis and stricture of the common bile duct, made it possible to achieve clinical success in the absence of complications and the need for long-term rehabilitation.

How to perform Purkinje tissue ablation for the treatment of idiopathic VF

How to perform Purkinje tissue ablation for the treatment of idiopathic VF

Restoration Integrity in Primary Teeth Prepared Using Erbium/Yttrium-Aluminum-Garnet Laser: A Randomized Split-Mouth Clinical Study.

The most frequently used and universally accepted technique for removing caries is mechanical ablation of decayed tissues by rotating drills. New minimally invasive strategies, such as the use of lasers to perform highly controlled tissue ablation, have been introduced in dental practice. The aim of this study was to assess and compare treatment with a 2940 nm erbium/yttrium-aluminum-garnet (Er:YAG) laser versus a conventional rotary treatment during cavity preparation in children with regard to restoration integrity. In a randomized, controlled, blinded trial using a split-mouth design, 40 (9-12-year-old) children with 80 carious primary molars were included. The cavity in one quadrant was randomized to be treated conventionally using a bur, while the cavity in the other quadrant was prepared using an Er:YAG laser. At the one-year follow-up, clinical examinations were conducted to assess the integrity of the restorations according to the Ryge criteria. The data were analyzed using SPSS version 22 (IBM Inc., Chicago, IL, USA). The average age of the participants was 9.4 ± 1.29 years. Males accounted for 51.4% of the participants. The Ryge criteria showed clinical success of restorations, and there was no discernible difference between the conventional and laser intervention techniques. Over one year, no statistically significant differences in the clinical integrity based on the Ryge criteria were found following class I cavity preparation in primary teeth with either procedure.

LIFU for major depressive disorder - Targeting the neural networks of depression

LIFU for major depressive disorder - Targeting the neural networks of depression Tiago Costa, Assistant Professor at the Department of Microelectronics, Delft University of Technology, discusses opportunities surrounding low-intensity focused ultrasound in the treatment of major depressive disorder in a minimally invasive manner. Major depressive disorder (MDD) is a prevalent and debilitating mental health condition affecting millions worldwide. While various treatment options exist, including medication and psychotherapy, a significant proportion of individuals with MDD do not achieve full remission or experience adverse side effects from existing treatments. Consequently, there is a need for innovative and effective therapeutic approaches to address this complex disorder. One emerging and promising area of research is the use of low-intensity focused ultrasound (LIFU) to treat major depressive disorder. LIFU is a non-invasive technique that utilises ultrasound waves at lower intensities compared to high-intensity focused ultrasound (HIFU), which is used for the thermal ablation of tissue. By focusing these ultrasound waves on specific brain regions, LIFU has shown potential in modulating neural activity and potentially alleviating depressive symptoms.

Combined Photorefractive Keratectomy and Corneal Cross-Linking for Keratoconus and Ectasia: The Athens Protocol.

Customized photorefractive keratectomy with minimal tissue ablation combined with corneal cross-linking seems to be a long-term safe and effective strategy for anatomical and visual management of keratoconus, postsurgical ectasia, and other ectasia management. Multiple published studies, many with long-term follow-up, have supported the Athens Protocol and its various forms as a means to manage corneal ectatic disorders, which not only stabilize corneal shapes but also improve functional vision.

Real-Time and Delayed Imaging of Tissue and Effects of Prostate Tissue Ablation.

Prostate ablation is increasingly being utilized for the management of localized prostate cancer. There are several energy modalities with varying mechanism of actions which are currently used for prostate ablation. Prostate ablations, whether focal or whole gland, are performed under ultrasound and/or MRI guidance for appropriate treatment plan execution and monitoring. A familiarity with different intraoperative imaging findings and expected tissue response to these ablative modalities is paramount. In this review, we discuss the intraoperative, early, and delayed imaging findings in prostate from the effects of prostate ablation. The monitoring of ablation both during and after the therapy became increasingly important due to the precise targeting of the target tissue. Recent findings suggest that real-time imaging techniques such as MRI or ultrasound can provide anatomical and functional information, allowing for precise ablation of the targeted tissue and increasing the effectiveness and precision of prostate cancer treatment. While intraprocedural imaging findings are variable, the follow-up imaging demonstrates similar findings across various energy modalities. MRI and ultrasound are two of the frequently used imaging techniques for intraoperative monitoring and temperature mapping of important surrounding structures. Follow-up imaging can provide valuable information about ablated tissue, including the success of the ablation, presence of residual cancer or recurrence after the ablation. It is critical and helpful to understand the imaging findings during the procedure and at different follow-up time periods to evaluate the procedure and its outcome.

Tissue Ablation Using Irreversible Electrolytic Electroporation with Reduced Voltage

Thermal tissue ablation may damage surrounding healthy tissue and cause pain. In this study, tissue ablation with the sequential application of electrical energy-inducing irreversible electroporation (IRE) and electrolysis (EL) (IRE + EL = IREEL) was investigated. An IREEL device was designed to control five output pulse parameters: voltage level (VL), pulse width (PW), pulse interval (PI), pulse number (PN), and pulse tail time (PTT). IREEL experiments were conducted on vegetable tissue. The results indicated that by increasing the VL and PTT, the ablation area increased, whereas the impedance was reduced significantly. Almost no ablation area was observed when only EL or IRE at 500 V and 1000 V, respectively, were applied. The ablation area observed with IRE alone at 1500 V was defined as 100%. In the case of IREEL at 500 V and 1000 V, ablation was induced even with the use of micro-second level PTT, and ablation areas of 91% and 186% were achieved, respectively. For IREEL at a voltage of 1500 V, the ablation area expanded to 209% and the maximum temperature was 48.7 °C, whereas the temperature did not exceed 30 °C under other conditions. A change in pH was also observed in an agar-gel phantom experiment which was conducted to examine and confirm whether IREEL induced electrolysis. IREEL was able induce ablation at low voltages owing to the synergistic effect of applying IRE and EL sequentially. Moreover, the ablation areas at high voltages could be increased compared to the areas observed when IRE and EL were applied independently.

Intravascular Sono-Ablation for In-Stent Restenosis Relief: Transducer Development and the In-Vitro Demonstration.

This study aimed to propose a new clinical modality for the relief of in-stent restenosis (ISR) using focused ultrasound (FUS) ablation. In the first research stage, a miniaturized FUS device was developed for the sonification of the remaining plaque after stenting, known as one of the causes of ISR. This study presents a miniaturized (<2.8 mm) intravascular FUS transducer for ISR treatment. The performance of the transducer was predicted through a structural-acoustic simulation, followed by fabrication of the prototype device. Using the prototype FUS transducer, we demonstrated tissue ablation with bio-tissues over metallic stents, mimicking in-stent tissue ablation. Next, we conducted a safety test by detecting the existence of thermal damage to the arterial tissue upon sonication with a controlled dose. The prototype device successfully delivered sufficient acoustic intensity (> 30 W/cm2) to a bio tissue (chicken breast) through a metallic stent. The ablation volume was approximately 3.9×7.8×2.6 mm3. Furthermore, 1.5 min sonication was sufficient to obtain an ablating depth of approximately 1.0 mm, not thermally damaging the underlying artery vessel. Conclusion: We demonstrated in-stent tissue sonoablation, suggesting it could be as a future ISR treatment modality. Significance: Comprehensive test results provide a key understanding of FUS applications using metallic stents. Furthermore, the developed device can be used for sonoablation of the remaining plaque, providing a novel approach to the treatment of ISR.

The Use of Focused Ultrasound Beams with Shocks to Suppress Diffusion Effects in Volumetric Thermal Ablation of Biological Tissue

The article presents the results of numerical simulation of an experiment on irradiatingex vivobovine liver sample by the therapeutic array of the MR-HIFU clinical system (Sonalleve V1 3.0T, Profound Medical Corp., Canada). Continuous quasi-linear and pulsed shock-wave exposures with the same time-averaged power are compared. Volumetric thermal lesions were generated by moving the focus of the array in its focal plane along discrete trajectories consisting of two or four concentric circles with a maximum radius of 4 mm. The effect of using the criteria for controlling the thermal dose during treatment and ending the sonication on the shape, volume, and exposure time of generating thermal lesion were analyzed. The acoustic field in tissue was calculated using the Westervelt equation; the temperature field was simulated with the inhomogeneous heat conduction equation; and the lesion boundary was determined according to the thermal dose threshold. In the quasi-linear mode corresponding to the clinical one, thermal diffusion leads to elongation of the lesion by a factor of 2–3 along the beam axis compared to the transverse dimension of the trajectory. The use of pulsed shock-wave exposures with switching off the inner circles of the trajectory as they reach the threshold value of the thermal dose makes it possible to significantly suppress the thermal diffusion effects in the axial direction of the beam and obtain localized thermal lesion of a given shape with a thermal ablation rate comparable to the clinical case.

A miniature fiber optic ablation probe manufactured via ultrafast laser inscription and selective chemical etching

Picosecond laser ablation has recently emerged as a minimally invasive alternative to conventional surgical resection of early tumors, offering high precision and limited thermal damage to surrounding tissue. Potential clinical application routes include deployment through the working channels of endoscopes or needle bores, which require the delivery of ultrashort high energy pulses through flexible optical fibers with focusing optics at the distal end. The manufacture of distal end optical systems for fiber ablation is challenging, inhibiting translation toward clinical applications. Here, we present a miniature fiber-coupled ablation probe developed using ultrafast laser inscription and chemical etching, employing a hollow-core fiber for pulse delivery. Its design, fabrication, and characterization are detailed, along with a feasibility demonstration for the ablation of stainless steel and chicken tissue.

Precision cooling radiofrequency ablation under tumor boundary temperature control

Radiofrequency ablation (RFA) represents a convenient, minimally invasive, and cost-effective approach for the treatment of small liver cancers measuring less than 3 cm in diameter. Nonetheless, the existing RFA techniques encounter challenges in precisely controlling the extent of ablation and the risk of overheating, which can lead to damage on the surrounding tissues. The ability to control the ablation area also plays a crucial role in the success of RFA procedures. To address these issues, we introduce a novel method that utilizes tumor boundary temperature monitoring to achieve precise control over the RFA process. Through the utilization of COMSOL Multiphysics simulation software, the proposed method was verified by comprehensive simulation and modeling and its efficacy in achieving regional control was testified. Subsequently, ex vivo experiments were conducted employing a custom-designed cooling RFA instrument. The experimental results demonstrated that the RFA controlled by boundary temperature yielded an ablation area with a diameter approaching 30 mm. In comparison to the standard spherical solidification zone (characterized by both the ellipticity and regularity indices of 1), the cooling RFA discoloration zone, under boundary temperature control, exhibited a maximum deviation of 7% in the ellipticity index and 17% in the regularity index. The average ellipticity index was determined to be 0.96, while the average regularity index was 0.86. Collectively, these findings underscore the capability of the proposed temperature-controlled cooling RFA method to attain precise control over the ablation area, contributing to comprehensive ablation of tumor tissue within the target region.

Information Quality Analysis of YouTube Videos on HIFU for Prostate Cancer: How much is too much?

Prostate adenocarcinoma is the most diagnosed cancer among men [1]. This highly prevalent disease in the localized stage is often tackled with either whole gland treatment (radical prostatectomy or radiation) vs. active surveillance [2-4]. However, in recent times there has been a push towards focal therapy with goals of eradicating significant cancer within the prostate while preserving genitourinary function [5,6]. Trans-rectal High-Intensity Focused Ultrasound (HIFU) ablation of prostate tissue) HIFU for prostate cancer, recently approved by the FDA offers patients and providers another treatment option to consider in management of this disease [7]. Thus, it is imperative that information that patients peruse be reliable and of good quality.

Histotripsy induces apoptosis and reduces hypoxia in a neuroblastoma xenograft model

Background Neuroblastoma (NB) is the most common extracranial solid tumor of childhood, and high-risk disease is resistant to intensive treatment. Histotripsy is a focused ultrasound therapy under development for tissue ablation via bubble activity. The goal of this study was to assess outcomes of histotripsy ablation in a xenograft model of high-risk NB. Methods Female NCr nude mice received NGP-luciferase cells intrarenally. Under ultrasound image guidance, histotripsy pulses were applied over a distance of 4–6 mm within the tumors. Bioluminescence indicative of tumor viability was quantified before, immediately after, and 24 h after histotripsy exposure. Tumors were immunostained to assess apoptosis (TUNEL), endothelium (endomucin), pericytes (αSMA), hypoxia (pimonidazole), vascular endothelial growth factor A (VEGFA), and platelet-derived growth factor-B (PDGF-B). The apoptotic cytokine TNFα and its downstream effector cleaved caspase-3 (c-casp-3) were assessed with SDS-PAGE. Results Histotripsy induced a 50% reduction in bioluminescence compared to untreated controls, with an absence of nuclei in the treatment core surrounded by a dense rim of TUNEL-positive cells. Tumor regions not targeted by histotripsy also showed an increase in TUNEL staining density. Increased apoptosis in histotripsy samples was consistent with increases in TNFα and c-casp-3 relative to controls. Treated tumors exhibited a decrease in hypoxia, VEGF, PDGF-B, and pericyte coverage of vasculature compared to control samples. Further, increases in vasodilation were found in histotripsy-treated specimens. Conclusions In addition to ablative effects, histotripsy was found to drive tumor apoptosis through intrinsic pathways, altering blood vessel architecture, and reducing hypoxia.

Evaluation of Different Registration Algorithms to Reduce Motion Artifacts in CT-Thermography (CTT).

Computed tomography (CT)-based Thermography (CTT) is currently being investigated as a non-invasive temperature monitoring method during ablation procedures. Since multiple CT scans with defined time intervals were acquired during this procedure, interscan motion artifacts can occur between the images, so registration is required. The aim of this study was to investigate different registration algorithms and their combinations for minimizing inter-scan motion artifacts during thermal ablation. Four CTT datasets were acquired using microwave ablation (MWA) of normal liver tissue performed in an in vivo porcine model. During each ablation, spectral CT volume scans were sequentially acquired. Based on initial reconstructions, rigid or elastic registration, or a combination of these, were carried out and rated by 15 radiologists. Friedman's test was used to compare rating results in reader assessments and revealed significant differences for the ablation probe movement rating only (p = 0.006; range, 5.3-6.6 points). Regarding this parameter, readers assessed rigid registration as inferior to other registrations. Quantitative analysis of ablation probe movement yielded a significantly decreased distance for combined registration as compared with unregistered data. In this study, registration was found to have the greatest influence on ablation probe movement, with connected registration being superior to only one registration process.

Microwave-Assisted Chemical Ablation (MA-CA): A Novel Microwave-Assisted Tissue Ablation Procedure—Preliminary Assessment of Efficiency

Microwave (MW) ablation is becoming a routine technology in the interventional radiology field. A new approach combining MW ablation and chemical ablation is developed in this paper. The rationale for the development of this Microwave-Assisted Chemical Ablation (MA-CA) technology was to improve the utility of thermal ablation as a minimally invasive treatment for cancer. The experimental conditions for ex vivo bovine liver samples were: A—100 W (120 s) with no addition of ethanol; B—100 W (30 s), wait (60 s) (no power), and 100 W (90 s) with no addition of ethanol; C—100 W (30 s), wait (60 s), 100 W (30 s), and 100 W (60 s) with the addition of 5 mL ethanol; and D—100 W (30 s), wait (60 s), 100 W (30 s), 0 W (30 s) with the addition of 2.5 mL ethanol, and 100 W (60 s) with the addition of 5 mL ethanol (12,000 Joules Total). The results showed that with the use of ethanol, the ablation zone was enlarged and revealed improved sphericity. This novel combination has greater advantages than either technology individually. The objective is to increase the precision and efficiency of MW ablation and to broaden the range of tissues and pathologies that can be treated using this new approach, and to validate the benefits that arise from combining the advantages of MW and chemical ablation in a relevant setting.

Safety and efficacy of intracavitary microwave ablation in hepatic gland tumours: Numerical and in vitro studies.

The microwave ablation (MWA) of large hepatic gland tumour using multiple trocars operated at 2.45/6 GHz frequencies has been analysed. The ablation region (in vitro) obtained using parallel and non-parallel insertion of multiple trocars into the tissue has been analysed and compared with the numerical studies. The present study has considered a typical triangular-shaped hepatic gland model for experimental and numerical analysis. COMSOL Multiphysics software with inbuilt bioheat transfer, electromagnetic waves, heat transfer in solids and fluids and laminar flow physics has been used to obtain the numerical results. Experimental analysis has been conducted on egg white using a market-available microwave ablation device. It has been found from the present study that MWA operated at 2.45/6 GHz with the non-parallel position of multiple trocars into the tissue leads to a considerable increase in the ablation region as compared to the parallel insertion of trocars. Hence, non-parallel insertion of trocars is suitable to treat irregular-shaped large cancerous tumours (>3 cm). The non-parallel simultaneous insertion of trocars can overcome the healthy tissue ablation issue as well as the problem associated with indentation. Further, reasonable accuracy (with the difference being nearly ±0.1 cm in ablation diameter) has been achieved in comparing the ablation region and temperature variation between experimental and numerical studies. The present study may create a new path in the ablation of large size tumours (>3 cm) with multiple trocars of all shapes by sparing the healthy tissue.

Photobiomodulation Therapy Mitigates Salivary Gland Damage Induced by Radioactive Iodine Ablation

(1) Background: Thyroid tissue ablation with radioactive iodine (RAI) has been successfully used in the treatment of differentiated thyroid cancers. However, as a side effect, RAI may induce salivary gland (SG) hypofunction, which has been alternatively managed with photobiomodulation therapy (PBMT). In our study, we assessed the effects of RAI on the SGs and further analyzed whether PBMT can minimize tissue damage. (2) Methods: Balb/c mice were allocated into three groups, as follows: RI, submitted to RAI orally; RIL, similar to RI, but with PBMT for SG hypofunction; and C, control group. The animals were euthanized on days 0, 10, and 90 after RAI. (3) Results: A decrease in tri-iodothyronine (T3) and thyroxine (T4) serum levels was observed both in the RI and RIL groups. In addition, a decrease in SG weight and morphological alterations were shown in the RI group throughout the experimental period, as well as a significant increase in total protein and peroxidase concentrations, and catalase activity. On day 90, the RI group presented less collagen and fewer sodium/iodine channels, with higher rates of cell apoptosis. Pertechnetate (Na99mTcO4) uptake was also affected in the RI group in all experimental times. Interestingly, although the RIL group also presented some alterations regarding these parameters, they were not statistically different from those of the C group on day 90. (4) Conclusions: Our results provide evidence that RAI induces harmful effects on the SGs, which can be successfully managed with PBMT.

A Stable and Compact Mid-IR at 6.45 μm Exceeding 6 mJ of Pulse Energy BaGa4Se7 Optical Parametric Oscillator

We experimentally demonstrate a stable and compact high pulse energy mid-infrared (MIR) 6.45 μm laser, which is produced by an optical parametric oscillator (OPO) based on the non-oxide BaGa4Se7 (BGSe) nonlinear crystal pumped by 1064 nm Nd:YAG laser oscillator. With optimizing the parameters of the OPO system, a record high idler energy of 6.76 mJ at 6.45 μm was obtained with 18.85 ns of pulse duration (FWHM) at the repetition rate of 10 Hz under 93.5 mJ of pump energy, corresponding to an optical-to-optical conversion efficiency up to 7.23% from 1064 nm to 6.45 μm. The experimental results were in close approximation with the theoretical calculations. To date, it is both the highest MIR pulse energy and the highest conversion efficiency at 6.45 μm for any 1 μm pumped OPOs. Further, excellent output energy stability is demonstrated, with an energy fluctuation of less than ±0.5% over 165 min. Such a laser is interesting for both scientific and medical applications, including, for instance, for trace gas analysis and tissue ablation.

Atrial myocardial substrate has a significant influence on local impedance data - clinical experience from high power short duration and standard radio frequency ablations

Abstract Funding Acknowledgements Type of funding sources: None. Background Local impedance is a new clinically used RF ablation parameter used to predict RF lesion creation. By now, data about the influence of atrial substrate on local impedance is still scarce. The aim of this study was to investigate local impedance data of different atrial tissues (healthy myocardium vs. Low Voltage areas) and the importance of local impedance drops during HPSD and standard RF ablation in atrial tissue. Methods A total of n=1319 clinical RF applications in n=51 clinical left atrial ablation procedures were analyzed regarding underlying RF ablation parameters (RF power, duration, contact force, global and local impedance data). 3D mapping data were used to differentiate RF ablations in low voltage areas (&amp;lt;=1.0mv) from those in healthy atrial myocardium (&amp;gt;1.0mV). Local and global impedance baseline values and drops, RF electrogram amplitude attenuation, as well as RF data were calculated and registered for statistical analysis. Results Local impedance drops were significantly higher during RF application in healthy myocardium when compared to low voltage areas (18,6 vs. 16,6 Ohm, p&amp;lt;0.01). Baseline local impedance was significantly higher in healthy atrial myocardium when compared to low voltage areas (105,4 vs. 99,1 Ohm, p&amp;lt;0.01). There was no significant difference in global impedance values between low voltage areas and healthy atrial myocardium (p=0.34). These findings were confirmed in HPSD (60W, 10s) as well as in standard (30-40W, 30-60s) RF applications. Impedance drops were significantly larger in HPSD when comapred to standard RF ablation (p&amp;lt;0.01). Detailed boxplot results are presented in the Figure. Conclusions Local impedance drop is a good predictor of RF lesion creation in HPSD as well standard RF ablations. Interestingly, different local impedance but not global impedance values were observed in healthy and low voltage areas. In clinical practice, local impedance may be a useful parameter to identify atrial substrate.