Coagulation Volume Research Articles

Percutaneous microwave ablation vs radiofrequency ablation in the treatment of hepatocellular carcinoma.

Hepatocellular cancer ranks fifth among cancers and is related to chronic viral hepatitis, alcohol abuse, steatohepatitis and liver autoimmunity. Surgical resection and orthotopic liver transplantation have curative potential, but fewer than 20% of patients are suitable candidates. Interventional treatments are offered to the vast majority of patients. Radiofrequency (RFA) and microwave ablation (MWA) are among the therapeutic modalities, with similar indications which include the presence of up to three lesions, smaller than 3 cm in size, and the absence of extrahepatic disease. The therapeutic effect of both methods relies on thermal injury, but MWA uses an electromagnetic field as opposed to electrical current used in RFA. Unlike MWA, the effect of RFA is partially limited by the heat-sink effect and increased impedance of the ablated tissue. Compared with RFA, MWA attains a more predictable ablation zone, permits simultaneous treatment of multiple lesions, and achieves larger coagulation volumes in a shorter procedural time. Major complications of both methods are comparable and infrequent (approximately 2%-3%), and they include haemorrhage, infection/abscess, visceral organ injury, liver failure, and pneumothorax. RFA may incur the additional complication of skin burns. Nevertheless, there is no compelling evidence for differences in clinical outcomes, including local recurrence rates and survival.

Evaluation of superparamagnetic iron oxide-polymer composite microcapsules for magnetic resonance-guided high-intensity focused ultrasound cancer surgery

BackgroundSuperparamagnetic poly (lactic-co-glycolic acid) (PLGA)-coated Fe3O4 microcapsules are receiving increased attention as potential diagnostic and therapeutic modalities in the field of oncology. In this study, PLGA-coated Fe3O4 microcapsules were combined with a magnetic resonance imaging-guided high-intensity focused ultrasound (MR-guided HIFU) platform, with the objective of investigating the effects of these composite microcapsules regarding MR-guided HIFU liver cancer surgery in vivo.MethodsPLGA-coated Fe3O4 microcapsules consisting of a liquid core and a PLGA-Fe3O4 shell were fabricated using a modified double emulsion evaporation method. Their acute biosafety was confirmed in vitro using MDA cells and in vivo using rabbits. To perform MR-guided HIFU surgery, the microcapsules were intravenously injected into a rabbit liver tumor model before MR-guided HIFU. T2-weighted images and MR signal intensity in normal liver parenchyma and tumor tissue were acquired before and after injection, to assess the MR imaging ability of the microcapsules. After MR-guided HIFU ablation tissue temperature mapping, the coagulative volume and histopathology of the tumor tissue were analyzed to investigate the ablation effects of MR-guided HIFUs.ResultsScanning and transmission electron microscopy showed that the microcapsules displayed a spherical morphology and a shell-core structure (mean diameter, 587 nm). The hysteresis curve displayed the typical superparamagnetic properties of the microcapsules, which are critical to their application in MR-guided HIFU surgery. In MR-guided HIFU surgery, these microcapsules functioned as an MRI contrast agent, induced significant hyperthermal enhancement (P < 0.05) and significantly enhanced the volume of coagulative necrosis (P < 0.05).ConclusionsThe administration of PLGA-coated Fe3O4 microcapsules is a potentially synergistic technique regarding the enhancement of MR-guided HIFU cancer surgery.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2407-14-800) contains supplementary material, which is available to authorized users.

A Comparative Study of Strychnos potatorum and Chemical Coagulants in the Treatment of Paint and Industrial Effluents: An Alternate Solution

This study was conducted to find a solution for the treatment of simulated industrial paint effluent using natural material, Strychnos potatorum, as a coagulant. The coagulation capacity was evaluated for a liter of effluent using standard jar test apparatus. The FTIR spectrum confirmed the existence of various functional groups in S. potatorum. The residence of proteins tied with coagulant treatment were determined and analyzed over SDS PAGE. The predominance of determining variables such as eluent type (water, NaCl, KCl), eluent concentration (1-5N), coagulant dosage (1-10 g), coagulant volume (20-100 mL), initial pH (5-11), and initial effluent concentration (3100, 4224, 5650, 6258, and 7693 mg/L named as sample number 1 to 5, respectively) were valued in terms of color, COD, and turbidity. The choicest outcome of the treatment was identified as, 2 g of S. potatorum, 3N NaCl as an eluent, 100 mL of coagulant volume, and the actual pH of the sample (7.2-7.8). It was found that the removal efficiency increased as the pollution load swelled. The results were matched with conventional coagulant alum. The amount of sludge formation was appreciably lower for natural coagulant. The results affirmed that the S. potatorum could act as an alternate solution for the paint effluent treatment.

Gel Phantom Study with High-Intensity Focused Ultrasound: Influence of Metallic Stent Containing Either Air or Fluid

We aimed to investigate whether a cylindrical structure containing either air or fluid and with or without a metallic stent affects the volume and density of cavitation produced by high-intensity focused ultrasound via a gel phantom study. Sixteen tissue-mimicking phantoms based on a polyacrylamide gel mixed with bovine serum albumin with a cylindrical hole 1 cm in diameter and 7.5 cm in length were divided into four groups of four phantoms with air in the holes (group 1), four phantoms with fluid in the holes (group 2), four phantoms with air-containing metallic stents (group 3) and four phantoms with fluid-containing metallic stents (group 4). A pulsed high-intensity focused ultrasound beam (50% duty cycle, 40-Hz pulse repetition frequency) at 75 W of acoustic power was directed perpendicularly to the longitudinal axis of the hole, with its focus at the posterior wall of the hole. The size of the cavitation on the x-, y-, and z-axes was measured, and the volumes of cavitation and coagulation were calculated using the formula for the volume of an elliptical cone. The density of cavitation was measured in the tissue phantom anterior to the hole with a 1 × 1-cm square region of interest. For statistical analysis, the Kruskal–Wallis test and Mann–Whitney U-test were used. The phantoms with air-containing holes (groups 1 and 3) developed larger and denser cavitations anterior to the focus, without unnecessary coagulation posterior to the focus, compared with the phantoms with fluid-containing holes (groups 2 and 4), regardless of the presence of stents. All of the axes and volumes of the anterior cavitations were significantly larger than those of the posterior cavitations in groups 1 and 3 (all p-values <0.05). The results of this study might be applied to maximize cavitation to enhance drug delivery into tumors.

Effects of Different Coagulants on Sweet Sorghum Juice Clarification

Sweet sorghum is a potential complementary crop for ethanol production in Brazil, United States and India. Since, phenols are playing inhibitory role in the process of ethanol production from extracted juice from sweet sorghum stalks, it's removal from juice is necessary for better ethanol yield. The aim of this research was to evaluate the use of magnesium oxide and calcium hydroxide as coagulant agents in different pH levels in the juice treatment. The experiment was arranged in a split-plot statistical design. Main treatments corresponded to the different coagulants and secondary treatments were the pH levels (6.0 and 7.0). Analysis of coagulant volume, juice pH, settling rate and sludge volume were performed during the decantation process. Clarified juice was analyzed as Brix, pH, ashes, phenolic compounds and starch. The use of magnesium oxide resulted in lower sludge volume, phenolic compounds and ashes. The use of calcium hydroxide decreased starch content, whereas clarification at pH 7.0 promoted higher sludge volume. Treating juice with magnesium oxide improved decantation dynamics of the process and clarified juice quality.

Cactus opuntia (ficus-indica): an eco-friendly alternative coagulant in the treatment of paint effluent

In this study, the potentiality of Cactus opuntia (ficus-indica), as a coagulant for the treatment of simulated industrial water-based paint wastewater in terms of colour, chemical oxygen demand (COD) and turbidity was investigated. The coagulation ability was assessed for 1 L of effluent using the standard jar test apparatus by varying the operational variables like eluent type (water, NaCl and BaCl2), eluent concentration (1–5 N), coagulant dosage (1–6 g), coagulant volume (20–100 mL), initial pH (5–11) and initial effluent concentration (3100, 4224, 5650, 6258 and 7693 mg/L named as sample number 1–5, respectively). The results were maximum when 100 mL of 3 g of C. opuntia, eluted using 3 N NaCl was used as a coagulant to treat a litre of effluent. The favourable pH to run the treatment was confirmed as the actual pH of the sample (7.2–7.8). It was found that the removal efficiency increased as the pollution load swelled. The FTIR study revealed the presence of various functional groups, which are responsible for the coagulation process. The obtained results were compared with conventional coagulant ferric chloride. The results acknowledged that Cactus opuntia (ficus-indica) a natural, eco-friendly coagulant, could be a strong alternative to the conventional coagulant in the treatment of water-based paint wastewater.

The influence of the nonsolvent intrusion through the casting film bottom surface on the macrovoid formation

The influence of nonsolvent intrusion through the casting film bottom surface on macrovoid formation in the immersion precipitation phase inversion process was investigated using two kinds of substrates, i.e., glass plate as a representation of dense plate and non-woven fabrics as a representation of porous materials. The results show that the cross-sectional structure of the membranes prepared on the glass plate varied with the casting film thickness which determined whether the nonsolvent could intrude through the casting film bottom surface. Macrovoids formed because of nonsolvent intrusion through the bottom surface when the casting film thickness range was between 150 and 250μm. The non-woven fabrics supported membrane M100-n-0 possessed macrovoids at the bottom while M100-g-0 whose substrate was a glass plate showed integrated sponge-like structure though they were prepared under the same conditions, which suggested the nonsolvent intrusion through the pores of the non-woven fabrics induced the macrovoid formation. To obtain non-woven fabrics supported membranes with pressure resistance, solvent N-methyl pyrrolidone (NMP) was added into the coagulation bath to reduce the mass transfer rate of solvent and nonsolvent through the pores, and then suppress the macrovoids. A compaction test was carried out to investigate the pressure resistance of the membranes. With the increase of solvent content in the coagulation bath, the quantity and volume of the macrovoids were reduced, hence the pressure resistance of the membranes increased.

MP62-05 MAGNETIC RESONANCE IMAGING (MRI)-GUIDED TRANSURETHRAL ULTRASOUND ABLATION OF PROSTATE CANCER: PRELIMINARY OUTCOMES OF A PHASE I CLINICAL TRIAL

You have accessJournal of UrologyProstate Cancer: Localized VII1 Apr 2014MP62-05 MAGNETIC RESONANCE IMAGING (MRI)-GUIDED TRANSURETHRAL ULTRASOUND ABLATION OF PROSTATE CANCER: PRELIMINARY OUTCOMES OF A PHASE I CLINICAL TRIAL Michele Billia, Mathieu Burtnyk, Timur Kuru, Sascha Pahernik, Matthias Roethke, Heinz-Peter Schlemmer, Cesare Romagnoli, and Joseph Chin Michele BilliaMichele Billia More articles by this author , Mathieu BurtnykMathieu Burtnyk More articles by this author , Timur KuruTimur Kuru More articles by this author , Sascha PahernikSascha Pahernik More articles by this author , Matthias RoethkeMatthias Roethke More articles by this author , Heinz-Peter SchlemmerHeinz-Peter Schlemmer More articles by this author , Cesare RomagnoliCesare Romagnoli More articles by this author , and Joseph ChinJoseph Chin More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2014.02.1962AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES MRI-guided transurethral ultrasound ablation (TULSA) is a new minimally-invasive technology for treatment of localized prostate cancer (PCa), aiming to provide good local disease control with a low side-effect profile. This modality consists of a transurethral device emitting planar ultrasound and generating a continuous and precise volume of thermal coagulation shaped to conform to the prostate, using real-time MRI monitoring and active temperature feedback control. A prospective, multi-center phase I clinical trial was initiated in March 2013 with the aim to determine safety and feasibility of MRI-guided TULSA, and to assess initial efficacy for localized PCa treatment. METHODS Patients with low-risk PCa: cT1c-T2a, N0, M0; PSA≤10ng/ml; GS≤6 are enrolled. Under general anesthesia, suprapubic catheter (SPC) is inserted and left in for 2 weeks. The TULSA device (PAD-105, Profound Medical Inc.) is inserted manually over a Nitinol guidewire and positioned precisely in the prostatic urethra with MRI guidance (3-Tesla unit). Treatment planning is performed under MRI prostate visualization, with therapeutic intent of conservative whole-gland ablation. Treatment is delivered under continuous MR thermometry feedback control, and patients recover with an outpatient protocol. Primary study endpoints are safety and feasibility, with follow-up to 12 months. Complete clinical monitoring is 5 years, including serial PSA, TRUS biopsy and QoL questionnaires (IPSS, IIEF, bowel domain of UCLA-PCI-SF). RESULTS To-date, 17 patients have been treated with no intraoperative complications. Median treatment time was 29 (24 – 61) min and prostate volume 45 (34 – 95) cc. Spatial control of thermal ablation was within ±1.5 mm and contrast-enhanced MRI confirmed the resulting non-perfused volume. Clavien II complications included urinary tract infections (4), and epididymitis (1). Clavien I complications included hematuria (3), and acute urinary retention after SPC removal (2) resolving after SPC re-insertion. At 1 month, median PSA reduced by 87% (60 – 99%) to 0.7 ng/ml (0.1 – 3.3 ng/ml), with the nadir expected by 6 months. Normal micturition returned after SPC removal, with no significant change in QoL at 3 months. CONCLUSIONS MRI-guidance enables accurate planning and real-time dosimetry and control of the thermal ablation volume. Initial results indicate that MRI-guided TULSA is safe and clinically feasible with a well-tolerated, low side effect profile. © 2014FiguresReferencesRelatedDetailsCited byBurtnyk M, Hill T, Cadieux-Pitre H and Welch I (2018) Magnetic Resonance Image Guided Transurethral Ultrasound Prostate Ablation: A Preclinical Safety and Feasibility Study with 28-Day FollowupJournal of Urology, VOL. 193, NO. 5, (1669-1675), Online publication date: 1-May-2015. Volume 191Issue 4SApril 2014Page: e718-e719 Advertisement Copyright & Permissions© 2014MetricsAuthor Information Michele Billia More articles by this author Mathieu Burtnyk More articles by this author Timur Kuru More articles by this author Sascha Pahernik More articles by this author Matthias Roethke More articles by this author Heinz-Peter Schlemmer More articles by this author Cesare Romagnoli More articles by this author Joseph Chin More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Monopolar Radiofrequency Ablation Using a Dual-Switching System and a Separable Clustered Electrode: Evaluation of theIn VivoEfficiency

ObjectiveTo determine the in vivo efficiency of monopolar radiofrequency ablation (RFA) using a dual-switching (DS) system and a separable clustered (SC) electrode to create coagulation in swine liver.Materials and MethodsThirty-three ablation zones were created in nine pigs using a DS system and an SC electrode in the switching monopolar mode. The pigs were divided into two groups for two experiments: 1) preliminary experiments (n = 3) to identify the optimal inter-electrode distances (IEDs) for dual-switching monopolar (DSM)-RFA, and 2) main experiments (n = 6) to compare the in vivo efficiency of DSM-RFA with that of a single-switching monopolar (SSM)-RFA. RF energy was alternatively applied to one of the three electrodes (SSM-RFA) or concurrently applied to a pair of electrodes (DSM-RFA) for 12 minutes in in vivo porcine livers. The delivered RFA energy and the shapes and dimensions of the coagulation areas were compared between the two groups.ResultsNo pig died during RFA. The ideal IEDs for creating round or oval coagulation area using the DSM-RFA were 2.0 and 2.5 cm. DSM-RFA allowed more efficient RF energy delivery than SSM-RFA at the given time (23.0 ± 4.0 kcal vs. 16.92 ± 2.0 kcal, respectively; p = 0.0005). DSM-RFA created a significantly larger coagulation volume than SSM-RFA (40.4 ± 16.4 cm3 vs. 20.8 ± 10.7 cm3; p < 0.001). Both groups showed similar circularity of the ablation zones (p = 0.29).ConclusionDual-switching monopolar-radiofrequency ablation using an SC electrode is feasible and can create larger ablation zones than SSM-RFA as it allows more RF energy delivery at a given time.

Numerical study of the influence of water evaporation on radiofrequency ablation

BackgroundRadiofrequency ablation is a promising minimal invasive treatment for tumor. However, water loss due to evaporation has been a major issue blocking further RF energy transmission and correspondently eliminating the therapeutic outcome of the treatment.MethodA 2D symmetric cylindrical mathematical model coupling the transport of the electrical current, heat, and the evaporation process in the tissue, has been developed to simulate the treatment process and investigate the influence of the excessive evaporation of the water on the treatment.ResultsOur results show that the largest specific absorption rate (Q SAR ) occurs at the edge of the circular surface of the electrode. When excessive evaporation takes place, the water dehydration rate in this region is the highest, and after a certain time, the dehydrated tissue blocks the electrical energy transmission in the radial direction. It is found that there is an interval as long as 65 s between the beginning of the evaporation and the increase of the tissue impedance. The model is further used to investigate whether purposely terminating the treatment for a while allowing diffusion of the liquid water into the evaporated region would help. Results show it has no obvious improvement enlarging the treatment volume. Treatment with the cooled-tip electrode is also studied. It is found that the cooling conditions of the inside agent greatly affect the water loss pattern. When the convection coefficient of the cooling agent increases, excessive evaporation will start from near the central axis of the tissue cylinder instead of the edge of the electrode, and the coagulation volume obviously enlarges before a sudden increase of the impedance. It is also found that a higher convection coefficient will extend the treatment time. Though the sudden increase of the tissue impedance could be delayed by a larger convection coefficient; the rate of the impedance increase is also more dramatic compared to the case with smaller convection coefficient.ConclusionThe mathematical model simulates the water evaporation and diffusion during radiofrequency ablation and may be used for better clinical design of radiofrequency equipment and treatment protocol planning.

Optimisation of the coagulation zone for thermal ablation procedures: A theoretical approach with considerations for practical use

Purpose: This paper outlines a theoretical approach for optimisation of the coagulation zone for thermal ablation procedures and considerations for its practical application. Methods: The theoretical approach is outlined in the Cartesian coordinate system. Considerations for practical application are implemented. The optimised coagulation zone is defined as the bare coverage of tumour mass plus a safety margin. The eccentricity of coagulation centre (ECC) is defined as the distance between the coagulation centre and the tumour centre. The direction of the applicator shaft is determined based on the x-axis direction. The tumour centre and coagulation centre are defined within the x/y-plane. The distance between coagulation margin (applicator tip) and tumour margin is called parallel offset (PAO). Results: For spherical coagulation shapes, a linear relationship exists between optimised coagulation diameter and ECC. An exponential relationship exists between optimised coagulation volume and ECC. A complex relationship was found between PAO and determinants of ECC, which are ex and ey. PAO is an extremely important parameter, which allows for determination of the optimal applicator tip position in relation to the tumour margin. It can be calculated in such a manner that the optimised coagulation zone is minimised by neutralising dislocation of the coagulation centre in applicator shaft direction. The latter can be realised by withdrawing or further inserting the applicator shaft. Conclusions: The presented concept can be used to optimise the extent of the coagulation zone for thermal ablation procedures after positioning of the applicator. Its inherent advantage is the simple adjustment of the applicator shaft, which obviates the need for a repuncture.

Bipolar Radiofrequency Ablation: Development of a New Expandable Device

To test the performance of an expandable bipolar probe as a simple technical solution for extending the coagulation volume. On the basis of a commercially available monopolar radiofrequency (RF) probe (LeVeen), an expandable bipolar RF probe was developed by integrating a second electrode into the probe shaft. The influence of length on the second electrode, and the distance between both electrodes and generator output was investigated by performing ten ablations for each condition on a freshly excised bovine liver. Macroscopically quantified coagulation volumes, lesion shape characteristics, and procedure durations were recorded. Results of the prototype featuring the optimal configuration were compared to the original LeVeen probe and commonly used bipolar RF probe (CelonLabPower). Extension of the shaft electrode length, increasing distance between the shaft electrode and the tip electrode, and reduction of generator output resulted in increasing coagulation volumes. The coagulation volumes the prototype generated were significantly smaller and more elliptically shaped than the monopolar probe (9.4 ± 1.5 cm(3) vs. 12.1 ± 1.6 cm(3)), but were larger than the commercially available bipolar RF probe (vs. 7.3 ± 0.5). The procedure duration of the prototype was comparable to the monopolar probe (467 ± 31 s vs. 464 ± 17 s) and shorter than the bipolar probe (vs. 2009 ± 444 s). In comparison to the commercially available bipolar system, the developed prototype exhibited favorable results. The first benchmark testing of the developed bipolar prototype had promising results. However, further optimization of the applicator design and ablation protocol is needed to enlarge the achievable coagulation volume.

Fluid preinjection for microwave ablation in an ex vivo bovine liver model assessed with volumetry in an open MRI system

We aimed to detect possible differences in microwave ablation (MWA) volumes after different fluid preinjections using magnetic resonance imaging (MRI). MWA volumes were created in 50 cuboid ex vivo bovine liver specimens (five series: control [no injection], 10 mL water, 10 mL 0.9% NaCl, 10 mL 6% NaCl, and 10 mL 12% NaCl preinjections; n=10 for each series). The operating frequency (915 megahertz), ablation time (7 min), and energy supply (45 watts) were constant. Following MWA, two MR sequences were acquired, and MR volumetry was performed for each sequence. For both sequences, fluid preinjection did not lead to significant differences in MWA ablation volumes compared to the respective control group (sequence 1: mean MWA volumes ranged from 7.0±1.2 mm [water] to 7.8±1.3 mm [12% NaCl] vs. 7.3±2.1 mm in the control group; sequence 2: mean MWA volumes ranged from 4.9±1.4 mm [12% NaCl] to 5.5±1.9 mm [0.9% NaCl] vs. 4.7±1.6 mm in the control group). The ablation volumes visualized with the two sequences differed significantly in general (P < 0.001) and between the respective groups (control, P ≤ 0.001; water, P < 0.001; 0.9% NaCl, P < 0.001; 6% NaCl, P ≤ 0.001; 12% NaCl, P < 0.001). The volumes determined with sequence 1 were closer to the expected ablation volume of 8 mL compared to those determined with sequence 2. For the fluid qualities and concentrations assessed, there is no evidence that fluid preinjection results in larger coagulation volumes after MWA. Because ablation volumes determined by MRI vary with the sequence used, interventionalists should gain experience in how to interpret postinterventional imaging findings (with the MR scanner, sequences, and parameters used) to accurately estimate the outcome of the interventions they perform.

Impact on Hemostatic Parameters of Interrupting Sitting with Intermittent Activity

Excessive sitting has been associated with an elevated risk of vascular conditions, particularly venous thrombosis. Interrupting sitting time with intermittent physical activity can reduce venous stasis; however, impacts on other aspects of thrombogenesis are less understood. To examine the effects of interrupting sitting time on blood coagulation and blood volume parameters in sedentary, middle-age, overweight/obese adults (11 men and 8 women; age = 53.8 ± 4.9 yr, body mass index = 31.2 ± 4.1 kg · m(-2); mean ± SD). The randomized three-period, three-treatment acute crossover trial consisted of uninterrupted sitting and sitting interrupted by 2-min bouts of either light- or moderate-intensity treadmill walking every 20 min. In each trial condition, blood samples were collected at baseline before the consumption of a standardized meal (-2 h) and postintervention (5 h). Plasma fibrinogen increased from baseline with uninterrupted sitting (0.24 g · L(-2), 95% confidence interval = 0.13-0.34, P < 0.001). Light-intensity but not moderate-intensity activity breaks attenuated the increase by 0.17 g · L(-1) (95% confidence interval = 0.01-0.32, P < 0.05). There were no between-condition differences in prothrombin time, activated partial thromboplastin time, von Willebrand factor, D-dimer, or platelet count. Uninterrupted sitting reduced plasma volume and increased hematocrit, hemoglobin, and red blood cell count; effects attenuated by both light- and moderate-intensity breaks (P < 0.05). White blood cell count increased with uninterrupted sitting and further increased with moderate-intensity breaks. Mean platelet volume increased with moderate-intensity but not light-intensity breaks or uninterrupted sitting. Uninterrupted sitting increased fibrinogen and reduced plasma volume, with associated increases in hemoglobin and hematocrit. Activity breaks attenuated these responses, indicative of an ameliorating influence on the procoagulant effects of uninterrupted sitting.

Quantification of Tissue Shrinkage and Dehydration Caused by Microwave Ablation: Experimental Study in Kidneys for the Estimation of Effective Coagulation Volume

PurposeTo quantify the extent of tissue shrinkage and dehydration caused by microwave (MW) ablation in kidneys for estimation of effective coagulation volume. Materials and MethodsMW ablations were carried out in ex vivo porcine kidneys. Six study groups were defined: groups 1A, 2A, and 3A for MW ablation (90 W for 5 min, 7.5 min, or 10 min), and groups 1B, 2B, and 3B for control (without MW ablation). Pre- and postinterventional volume analyses were performed. Effective coagulation volumes (original tissue included in coagulation) were determined. Postinterventional dehydration analyses were performed with calculation of mean mass fractions of water. ResultsMean deployed energies were 21.6 kJ ± 1.1 for group 1A, 29.9 kJ ± 1.0 for group 2A, and 42.1 kJ ± 0.5 kJ for group 3A, and were significantly different (P < .0001). Differences between pre- and postinterventional volumes were −3.8% ± 0.6 for group 1A, −5.6% ± 0.9 for group 2A, and −7.2% ± 0.4 for group 3A, and −1.1% ± 0.3 for group 1B, −1.8% ± 0.4 for group 2B, and −1.1% ± 0.4 for group 3B. Postinterventional volumes were significantly smaller than preinterventional volumes for all groups (P < .01). Underestimations of effective coagulation volume from visualized coagulation volume were 26.1% ± 3.5 for group 1A, 35.2% ± 11.2 for group 2A, and 42.1% ± 4.9 for group 3A, which were significantly different (P < .01). Mean mass fractions of water were 64.2% ± 1.4 for group 1A, 63.2% ± 1.7 for group 2A, and 62.6% ± 1.8% for group 3A, with significant differences versus corresponding control groups (P < .01). ConclusionsFor MW ablation in kidneys, underestimation of effective coagulation volume based on visualized coagulation volume is significantly greater with greater deployed energy. Therefore, local dehydration with tissue shrinkage is a potential contributor.

Hypertonic saline-enhanced radiofrequency versus chemoembolization sequential radiofrequency in the treatment of large hepatocellular carcinoma

Large hepatocellular carcinoma (HCC) appears to be a major obstacle for radiofrequency ablation (RFA); therefore, attempts to increase the volume of coagulation by injecting hypertonic saline before and/or during RFA have been made. Transarterial chemoembolization (TACE) combines the effect of targeted chemotherapy with ischemic necrosis and eliminates heat loss if combined with RFA. Our aim was to compare the efficacy of hypertonic saline-enhanced RFA versus TACE sequential RFA in the treatment of medium and large nodular HCC. This prospective study was carried out on 40 patients with 40 HCCs between 2008 and 2010 in the Tropical Medicine and Hepatology Department, Faculty of Medicine, Cairo University. They were divided into two groups (20 patients each): the first group received hypertonic saline-enhanced RFA (RFA+HS) and the second group underwent transarterial chemoembolization, followed by RFA (TACE+RFA). Triphasic computed tomography 1 month after the procedure showed that 17 (85%) patients in each group achieved complete ablation, whereas three (15%) in each group achieved partial ablation. In the RFA+HS group, 12/13 (92%) of medium HCC and 5/7 (71%) of large HCC were successfully ablated. In the TACE+RFA group, 8/8 (100%) medium HCC and 9/12 (75%) of large lesions were successfully ablated. The relation between success rate and lesion diameter was statistically significant only in RFA+HS group. After 6 months, 73.7% of patients in the RFA+HS group and 83.3% of patients in the TACE+RFA group showed maintained ablation (P=0.86). RFA+HS and TACE+RFA are safe and equally effective treatments for medium to large HCC.

Electronic Beam Steering Used with a Toroidal HIFU Transducer Substantially Increases the Coagulated Volume

Treatment with high-intensity focused ultrasound is well established but requires extended treatment time. A device composed of 256 elements arranged on a toroidal transducer was developed to increase the coagulated volume. When all the elements are working in phase for 40 s, a volume of 6–8 cm3 can be ablated. However, the mechanical juxtaposition of single lesions is still necessary for treating one tumor with a diameter of 2 cm. The objective of this study was to combine this toroidal transducer geometry with electronic beam steering to ablate tumors with adequate normal tissue margins and without any mechanical displacement of the high-intensity focused ultrasound device. In vitro tests demonstrated that the coagulated volume obtained from 130 s of total exposure has an average diameter of 41.4 ± 4.0 mm and an average length of 53.3 ± 6.1 mm. This single lesion can be used to treat various size of metastasis, located at depths in the liver ranging 5–45 mm.

Coagulation of Oil in Water Using Sawdust and Bentonite and the Formation of a Floating Coagulated Material

AbstractThe coagulation of oil in water is potentially cost-effective for removing oil from water. A coagulant consisting of sawdust (79.6% by volume), bentonite (15.8% by volume), and calcium hydroxide (4.7% by volume) gives coagulation efficiency of ≥94% and coagulation time of ≤45 s. The resulting coagulated material (a semisolid) floats on water. Its oil (liquid) content, which decreases with a decreasing amount of oil originally present in the water, ranges from 69–81% by volume. This paper provides the first identification of multiple forms of oil in a coagulated material that is made from a single form of oil. The oil consists of strongly bonded oil (16% by volume, with relative dielectric constant 32) and weakly bonded oil (84% by volume, with the same relative dielectric constant of 2.0 as the original oil). The maximum and minimum volumes of oil per unit area that can be coagulated by 0.022 cm3/cm2 of coagulant volume per unit area are 0.116 and 0.052 cm3/cm2, respectively. Below the minimum ...

Can electroporation previous to radiofrequency hepatic ablation enlarge thermal lesion size? A feasibility study based on theoretical modelling and in vivo experiments

Purpose: The aim of this study was to assess the feasibility of a hybrid ablative technique based on applying electroporation (EP) pulses just before conducting radiofrequency ablation (RFA). The rationale was that the EP-induced reduction in blood perfusion could be sufficient to reduce the thermal sink effect and hence to increase the coagulation volume in comparison to that created exclusively by RFA.Materials and methods: A modelling study and in vivo experimental study were used. A Cool-tip RF applicator was used both for EP and RFA.Results: Overall, the results did not show any synergy effect from using the hybrid technique. Applying EP pulses prior to RFA did not increase the coagulation zone obtained and the lesions were almost identical. Additional computer simulations provided an explanation for this; the effect of reducing blood perfusion by thermal damage during RFA completely masks the effect of reducing blood perfusion by EP. This is because both thermal damage and EP affect the same zone, i.e. the tissue around the electrode.Conclusions: Our computer modelling and in vivo experimental findings suggest that the combination of EP and RFA with monopolar applicators does not provide an additional benefit over the use of RFA alone.

Comparison of Four Microwave Ablation Devices: An Experimental Study in ex Vivo Bovine Liver

To compare volume, sphericity, and short-axis diameter of the coagulation zone of four commercially available microwave ablation systems with three technical concepts in an ex vivo setting and to formulate mathematical models to predict these quantities. Two high-power systems (systems A and B), a system that enables simultaneous use of three antennas (system C), and a non-perfusion-cooled system that automatically adapts power and frequency (system D) were tested in ex vivo bovine livers (108 ablations). Coagulation volume, sphericity, and mean short-axis diameter were assessed, and mathematical functions were fitted for each system and assessed with the coefficient of determination (R(2)). Analysis of variance and Tukey post hoc tests were used for interdevice comparison after 5 and 10 minutes and after maximum recommended ablation time. Volume and short-axis diameter were determined by using a mathematical model for every system, with coefficients of determination of 0.75-0.98 and 0.70-0.97, respectively. Correlation for determination of sphericity was lower (R(2) = 0.01-0.68). Mean results with ablation performed according to manufacturer recommendations were as follows: Volume, sphericity, and short-axis diameter were 57.5 cm(3), 0.75, and 43.4 mm, respectively, for system A; 72.3 cm(3), 0.68, and 45.5 mm, respectively, for system B; 17.1 cm(3), 0.58, and 26.8 mm, respectively, for system C (one antenna); 76.5 cm(3), 0.89, and 50.6 mm, respectively, for system C (three antennas); and 56.0 cm(3), 0.64, and 40.9 mm, respectively, for system D. Systems A (mean volume, 52.4 cm(3) ± 4.5 [standard deviation]) and B (39.4 cm(3) ± 1.7) reach large ablation zones with 5-minute ablation. The largest ablation zone is obtained with systems B and C (three antennas) under maximum recommended ablation duration and with system A under short ablation time. The most spherical zone is obtained with system C (three antennas).