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PURPOSE: This study aimed to compare the immune responses induced by microwave ablation (MWA), radiofrequency ablation (RFA), and cryoablation (CRYO) in hepatocellular carcinoma (HCC) and identify differences in immune responses and the timing of immune changes. MATERIALS AND METHODS: A bilateral subcutaneous model was established in C57 mice, and the successfully modeled mice were divided into the microwave (n = 15), radiofrequency (n = 15), CRYO (n = 15), control (n = 9), and blank groups (n = 3). Mice in the control group were dissected before ablation, whereas mice in the three ablation groups underwent ultrasound-guided ablation of one axillary tumor. Three mice were sacrificed and dissected at 1-4 weeks after ablation. After tissue processing, flow cytometry was used to detect the levels of CD8 + T and regulatory T (Treg) cells in the tissue, and western blotting was used to assess the level of programmed cell death ligand 1 (PD-L1) protein in the tumor tissue. RESULTS: The pattern of immune changes after the three types of ablation was consistent, with immune changes occurring at 3-4 weeks. CRYO induced the most significant increase in the percentage of CD8 + T cells. There were no significant differences in the levels of Treg cells and the level of PD-L1 protein among the three types of ablation (p > 0.05), but the decline in Treg cells and PD-L1 protein level caused by CRYO was the most pronounced. CONCLUSION: In the HCC mouse model, the immune changes following the three types of ablation were consistent, with immune changes occurring at 3-4 weeks. Among them, CRYO elicited the strongest adaptive immune response, and RFA outperformed MWA.

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BACKGROUND: A necessary precondition for a successful microwave hyperthermia (HT) treatment delivered by phased arrays is the ability of the HT applicator to selectively raise the temperature of the entire tumor volume. SAR-based treatment plan (HTP) optimization methods exploit the correlation between specific absorption rate (SAR) and temperature increase in order to determine the set of steering parameters for optimal focusing, while allowing for lower model complexity. Several cost functions have been suggested in the past for this optimization problem. However, their correlation with high and homogeneous tumor temperatures remains sub-optimal in many cases. Previously, we proposed the hot-to-cold spot quotient (HCQ) as a novel cost function for SAR-based HTP optimization and showed its potential to address these issues. MATERIALS AND METHODS: In this work, we validate the HCQ on a standard ESHO patient repository within single and multi-frequency contexts. We verify its correlation with clinical SAR and temperature indexes, and compare it to HTPs obtained using a commonly accepted cost-function for SAR-based HTP (hot-spot to target quotient, HTQ). RESULTS AND DISCUSSION: The results show that low HCQ values produce better SAR (TC50, TC75) and temperature metrics (T50, T90) than HTQ in most patient models and frequency settings. For the deep-seated tumors, the correlation between the clinical indicators and 1/HCQ is more favorable than the correlation exhibited by 1/HTQ. CONCLUSION: The validation confirms the ability of HCQ to promote target coverage and hot-spot suppression in SAR-based HTP optimization, resulting in higher SAR and temperature indexes for deep-seated tumors.

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PURPOSE: To evaluate the overall survival (OS), local progression-free survival (PFS) and prognostic factors of patients with colorectal cancer liver metastases (CRLM) undergoing microwave ablation (MWA). METHOD: A total of 132 patients were retrospectively enrolled who had been treated between 2010 and 2018. For the evaluation of survival rates, all patients were divided according to their indications (curative n = 57 and debulking (patients with additional non-target extrahepatic metastases) n = 75). In total, 257 ablations were evaluated for prognostic factors: number of liver metastases, primary tumor origin (PTO), diameter and volume of metastases, duration and energy of ablation. RESULTS: The OS was 32.1 months with 93.2% of patients free from recurrence at 28.3 months (median follow-up time). The one- year and three-year OS were 82.72% and 41.66%, respectively. The OS and recurrence-free survival of the curative group were statistically significantly higher than the debulking group (p < .001). Statistically significant prognostic factors for OS included the location of the primary tumor (p < .038) and the number of metastases (all p < .017). Metastasis diameter and volume and ablation duration and energy had no significant correlation with survival (p > .05). CONCLUSIONS: Satisfactory OS and local tumor PFS can be achieved in patients with CRLM using MWA with the number of metastases and the location of the primary tumor influencing the outcome of patients. The metastasis's size and the duration and energy used for ablation were not of significant prognostic value.

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PURPOSE: To develop and validate a three-dimensional (3-D) computer model based on accurate geometry of an irrigated cardiac radiofrequency (RF) ablation catheter with microwave radiometry capability, and to test catheter performance. METHODS: A computer model was developed based on CAD geometry of a RF cardiac ablation catheter prototype to simulate electromagnetic heating, heat transfer, and computational fluid dynamics (blood flow, open irrigation, and natural convection). Parametric studies were performed; blood flow velocity (0-25 cm/s) and irrigation flow (0-40 ml/min) varied, both with perpendicular (PE) and parallel (PA) catheter orientations relative to tissue. Tissue Agar phantom studies were performed under similar conditions, and temperature maps were recorded via infrared camera. Computer model simulations were performed with constant voltage and with voltage adjusted to achieve maximum tissue temperatures of 95-105 °C. RESULTS: Model predicted thermal lesion width at 5 W power was 5.8-6.4 mm (PE)/6.5-6.6 mm (PA), and lesion depth was 4.0-4.3 mm (PE)/4.0-4.1 mm (PA). Compared to phantom studies, the mean errors of the computer model were as follows: 6.2 °C(PE)/4.3 °C (PA) for maximum gel temperature, 0.7 mm (10.9%) (PE)/0.1 mm (0.8%) (PA) for lesion width, and 0.3 mm (7.7%)(PE)/0.7 mm (19.1%) (PA) for lesion depth. For temperature-controlled ablation, model predicted thermal lesion width was 7-9.2 mm (PE)/8.6-9.2 mm (PA), and lesion depth was 4.3-5.5 mm (PE)/3.4-5.4 mm (PA). CONCLUSIONS: Computer models were able to reproduce device performance and to enable device evaluation under varying conditions. Temperature controlled ablation of irrigated catheters enables optimal tissue temperatures independent of patient-specific conditions such as blood flow.

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Background: Accurate lesion visualization after microwave ablation (MWA) remains a challenge. Computed tomography perfusion (CTP) has been proposed to improve visualization, but it was shown that different perfusion-models delivered different results on the same data set.Purpose: Comparison of different perfusion algorithms and identification of the algorithm enables for the best imaging of lesion after hepatic MWA.Materials and methods: 10 MWA with consecutive CTP were performed in healthy pigs. Parameter-maps were generated using a single-input-dual-compartment-model with Patlak's algorithm (PM), a dual-input-maximum-slope-model (DIMS), a dual-input-one-compartment-model (DIOC), a single-(SIDC) and dual-input-deconvolution-model (DIDC). Parameter-maps for hepatic arterial (AF) and portal venous blood flow (PF), mean transit time, hepatic blood volume (HBV) and capillary permeability were compared regarding the values of the normal liver tissue (NLT), lesion, contrast- and signal-to-noise ratios (SNR, CNR) and inter- and intrarater-reliability using the intraclass correlation coefficient, Bland-Altman plots and linear regression.Results: Perfusion values differed between algorithms with especially large fluctuations for the DIOC. A reliable differentiation of lesion margin appears feasible with parameter-maps of PF and HBV for most algorithms, except for the DIOC due to large fluctuations in PF. All algorithms allowed for a demarcation of the central necrotic zone based on hepatic AF and HBV. The DIDC showed the highest CNR and the best inter- and intrarater reliability.Conclusion: The DIDC appears to be the most feasible model to visualize margins and necrosis zones after microwave ablation, but due to high computational demand, a single input deconvolution algorithm might be preferable in clinical practice.

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Purpose: This study assessed the efficacy and safety of computed tomography (CT)-guided percutaneous thermal ablation for hepatocellular carcinoma adjacent to the second porta hepatis.Methods: From January 2011 to June 2018, 59 consecutive patients (51 men and 8 women aged 29-85 years) with 65 tumors (mean maximum tumor diameter: 20.5 ± 1.2 mm; range: 5-50 cm) adjacent to the second porta hepatis underwent percutaneous CT-guided thermal ablation. The complete ablation rate, local progression-free survival (LPFS), progression-free survival (PFS), prognostic factors for local progression, and safety of this technique were assessed.Results: No more than three sessions were performed to complete a patient's treatment. Technical success was achieved for all tumors. In the median follow-up of 18.5 months, local tumor progression occurred in 32.2% (19/59) of patients, while tumor progression occurred in 71.2% (42/59). The median LPFS was 37.4 months. The 1-, 2-, and 3-year LPFS rates were 86.2%, 66.5%, and 66.5%, respectively. The median PFS was 11.0 months. The 1-, 2-, and 3-year PFS rates were 47.9%, 27.0%, and 20.2%, respectively. The tumor size (P = .007) and distance between the tumor and inferior vena cava (P = 0.018) were the independent prognostic factors for local tumor progression.Conclusion: We showed that CT-guided percutaneous microwave ablation and radiofrequency ablation are effective and safe treatments for tumors adjacent to the second porta hepatis, particularly in patients with lesions less than 3 cm and a distance between the tumor and inferior vena cava of more than 5 mm.

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Percutaneous ablation is an increasingly applied technique for the treatment of localized renal tumors, especially for elderly or co-morbid patients, where co-morbidities increase the risk of traditional nephrectomy. Ablative techniques are technically suited for the treatment of tumors generally not exceeding 4 cm, which has been set as general consensus cutoff and is described as the upper threshold of T1a kidney tumors. This threshold cutoff is being challenged, but with still limited evidence. Percutaneous ablation techniques for the treatment of renal cell carcinoma (RCC) include radiofrequency ablation, cryoablation, laser or microwave ablation; the main advantage of all these techniques over surgery is less invasiveness, lower complication rates and better patient tolerability. Currently, international guidelines recommend percutaneous ablation either as intervention for frail patients or as a first line tool, provided that the tumor can be radically ablated. The purpose of this article is to describe the basic concepts of percutaneous ablation in the treatment of RCC. Controversies concerning techniques and products and the need for patient-centered tailored approaches during selection among the different techniques available will be discussed.

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PURPOSE: Pancreatic cancer is a challenging malignancy with low treatment option and poor life expectancy. Thermal ablation techniques were proposed as alternative treatment options, especially in advanced stages and for unfit-for-surgery patients. This systematic review describes the thermal ablative techniques -i.e., Laser (LA), Radiofrequency (RFA), Microwave (MWA) Ablation, High-Intensity Focused Ultrasound (HIFU) and cryoablation- available for pancreatic cancer treatment. Additionally, an analysis of the efficacy, complication rate and overall survival for each technique is conducted. MATERIAL AND METHODS: This review collects the ex vivo, preclinical and clinical studies presenting the use of thermal techniques in the pancreatic cancer treatment, searched up to March 2018 in PubMed and Medline. Abstracts, letters-to-the-editor, expert opinions, reviews and non-English language manuscripts were excluded. RESULTS: Sixty-five papers were included. For the ex vivo and preclinical studies, there are: 12 records for LA, 8 for RFA, 0 for MWA, 6 for HIFU, 1 for cryoablation and 3 for hybrid techniques. For clinical studies, 1 paper for LA, 14 for RFA, 1 for MWA, 17 for HIFU, 1 for cryoablation and 1 for hybrid techniques. CONCLUSIONS: Important technological advances are presented in ex vivo and preclinical studies, as the real-time thermometry, nanotechnology and hybrid techniques to enhance the thermal outcome. Conversely, a lack of standardization in the clinical employment of the procedures emerged, leading to contrasting results on the safety and feasibility of some analyzed techniques. Uniform conclusions on the safety and feasibility of these techniques for pancreatic cancer will require further structured investigation.

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INTRODUCTION: Several techniques can be used to treat intravesical chemohyperthermia (ChHT). We compared radiofrequency-induced hyperthermia (RF-HT) with conductive hyperthermia (C-HT) for their ability to induce bladder wall temperatures of >40.5 °C, the target temperature for ChHT. MATERIALS AND METHODS: Fresh porcine bladders (n = 12) were placed in a temperature-controlled saline bath to simulate body temperature and circulation. HT was induced with RF-HT (43 °C) or C-HT (inflow temperature 44 and 46 °C) using a custom-made device. In two additional bladders, we varied intravesical solution and volume. Temperatures were recorded with a three-way catheter containing three mucosal and two urethral thermocouples (TCs) and a 915 MHz RF antenna, and with external TCs in the bladder wall at three different levels and three different locations. RESULTS: Target temperature (40.5 °C) was reached in the submucosa at all locations by both techniques. In the detrusor, target temperature was reached by RF-HT at the bladder neck and side wall. C-HT46 reached significantly higher submucosal temperatures at the side wall. The bladder dome seemed best heated by C-HT, although a high inflow temperature (46 vs. 44 °C) was required (ns). Intravesical saline resulted in higher temperatures than sterile water for RF-HT. A volume of 100 mL resulted in higher bladder dome temperatures for RF-HT, and higher bladder neck with lower dome temperatures for C-HT. CONCLUSION: Our results indicate a slightly superior heating capacity for RF-HT compared to C-HT, whereas for the bladder dome, the reverse seems true. Comparative studies are warranted to evaluate whether HT efficacy differs between both techniques, with emphasis on tumor location.

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PURPOSE: Comparison between different thermal ablation systems for thyroid nodules regarding their different procedural characteristics such as treatment-time, number of shots and energy transmission in the context of their clinical performance such as complication rate and volume reduction after three months. METHODS: A total of 60 patients with 65 nodules underwent thermal ablation of thyroid nodules with either microwave ablation (MWA) (9 male, 15 female and mean age 57 ± 13 years) or radiofrequency ablation (RFA) (12 male, 24 female and mean age 54 ± 12 years). RESULTS: Mean initial volume (MWA: 23.90 ± 17.35 ml; RFA: 29.44 ± 30.09 ml), energy transmission (MWA: 13.56 ± 10.17 kJ; RFA: 15.12 ± 13.45 kJ), energy transmission per ml (MWA: 0.85 ± 1.01 kJ/ml; RFA: 0.65 ± 0.32 kJ/ml), power (MWA: 22.69 ± 12.32 J/s; RFA: 20.97 ± 7.86 J/s) and duration of ablation (MWA: 618 ± 304 s; RFA: 695 ± 463 s) were not statistically different (p > .05). MWA required significantly less shots (MWA: 3 ± 1; RFA: 6 ± 3) than RFA (p < .05). At three-months follow-up a significant mean nodular volume reduction of 53.54 ± 15.40% after MWA and 51.21 ± 16.58% after RFA (p < .05) was measured. However, mean nodular volume reduction was not significantly different between both systems (p > .05). One patient treated by MWA reported a transient Horner's syndrome, which recovered without any further treatment. Major complications such as nodule rupture, infection or persisting nerve injuries did not occur. CONCLUSION: Both systems are suitable to treat thyroid nodules and show no significant difference in the duration of application, energy transmission and volume reduction. However, MWA requires less shots to treat the whole nodule.

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PURPOSE: To determine the role of hepatic radiofrequency ablation (RFA) heating parameters and their activation of heat shock proteins (HSPs) in modulating distant tumor growth. METHODS AND MATERIALS: First, to study the effects of RFA dose on distant tumor growth, rats with subcutaneous R3230 adenocarcinoma (10 ± 1 mm) were assigned to 3 different hepatic RF doses (60 °C × 10 min, 70 °C × 5 min or 90 °C × 2 min) that induced identical sized ablation or sham (n = 6/arm). Post-RFA tumor growth rates, cellular proliferation (Ki-67) and microvascular density (MVD) were compared at 7d. Next, the effect of low and high power doses on local HSP70 expression and cellular infiltration (α-SMA + myofibroblasts and CD68 + macrophages), cytokine (IL-6) and growth factor (HGF and VEGF) expression was assessed. Finally, 60 °C × 10 min and 90 °C × 2 min RFA were combined with anti-HSP micellar quercetin (MicQ, 2 mg/ml). A total of 150 animals were used. RESULTS: Lower RF heating (70 °C × 5 min and 60 °C × 10 min) resulted in larger distant tumors at 7d (19.2 ± 0.8 mm for both) while higher RF heating (90 °C × 2) led to less distant tumor growth (16.7 ± 1.5 mm, p < .01 for both), though increased over sham (13.5 ± 0.5 mm, p < .01). Ki-67 and MVD correlated with tumor growth (p < .01 for all). Additionally, lower dose 60 °C × 10 min hepatic RFA had more periablational HSP70 compared to 90 °C × 2 min (rim: 1.106 ± 163 µm vs. 360 ± 18 µm, p < .001), with similar trends for periablational α-SMA, CD68 and CDC47 (p < .01 for all). Anti-HSP70 MicQ blocked distant tumor growth for lower dose (60 °C × 10: RF/MicQ 14.6 ± 0.4 mm vs. RF alone: 18.1 ± 0.4 mm, p < .01) and higher dose RFA (90 °C × 2 min: RF/MicQ 14.6 ± 0.5 mm vs. RF alone: 16.4 ± 0.7 mm, p < .01). CONCLUSION: Hepatic RF heating parameters alter periablational HSP70, which can influence and stimulate distant tumor growth. Modulation of RF heating parameters alone or in combination with adjuvant HSP inhibition can reduce unwanted, off-target systemic tumorigenic effects.

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OBJECTIVES: To prospectively evaluate the effectiveness of intra-articular application of pulsed radiofrequency (PRF) combined with viscosupplementation in patients with knee osteoarthritis suffering from chronic pain refractory to conservative therapies. METHODS: During a 30-month period, PRF combined with viscosupplementation was performed on 53 cases of knee osteoarthritis (45 patients, 8/45 with bilateral knee osteoarthritis). Pre-operational imaging included standard knee X-rays on anterior-posterior and lateral views used to evaluate patients according to the Kellgren-Lawrence classification. Pain, prior, one week/one, 6 and 12 months post were compared by means of a numeric visual scale (NVS) questionnaire. RESULTS: Mean pain score prior to PRF was 8.19 ± 1.4 NVS units. This score was reduced to a mean value of 2.47 ± 2.5 NVS units at 1 week after, 2.55 ± 2.6 at 1 month, 3.1 ± 2.8 at 6 months and 5.02 ± 3.09 at 12 months of follow-up (p < 0.01). Overall mobility improved in 47/53 (88.6%) patients. No complication was observed. CONCLUSIONS: Combining PRF with viscous supplementation is an effective and safe technique for palliative management of chronic pain in patients with knee osteoarthritis. Results seem to be reproducible and long lasting. There seems to be a need of repeating the session at 1 year.

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OBJECTIVES: Percutaneous ablation is an expanding, minimally invasive approach for small- to medium-sized renal masses. The purpose of this study is to review safety, and mid-term efficacy of percutaneous microwave ablation (MWA) for Renal Cell Carcinoma (RCC) treatment using a high power microwave system. METHODS AND MATERIALS: Institutional database research identified 50 consecutive patients with a single lesion resembling renal cell carcinoma in CT and MRI who underwent percutaneous microwave ablation using a high power microwave system. All patients underwent biopsy on the same session with ablation using an 18G semi-automatic soft tissue biopsy needle. Contrast-enhanced computed tomography or magnetic resonance imaging was used for post-ablation follow-up. Patient and tumour characteristics, microwave technique, complications and pattern of recurrence were evaluated. RESULTS: Mean patient age was 74 years (male-female: 31-19). Average lesion size was 3.1 cm (range 2.0-4.3 cm). Biopsy results report RCC (n = 48), inflammatory myofibroblastic tumour (n = 1), and non-diagnostic sample (n = 1). The 3-year overall survival was 95.8% (46/48). Two patients died during the 3-year follow-up period due to causes unrelated to the MW ablation and to the RCC. Minor complications including haematomas requiring nothing but observation occurred at 4% (2/50) of the cases. Local recurrence of 6.25% (3/48) was observed with 2/3 cases being re-treated achieving a total clinical success of 97.9% (47/48 lesions). CONCLUSIONS: Percutaneous microwave ablation of RCC using a high power microwave system is a safe and efficacious technique for the treatment of small- to medium-sized renal masses.

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OBJECTIVES: To evaluate the clinical performance of a new microwave ablation (MWA) system with enabled constant spatial energy control (ECSEC) to achieve spherical ablation zones in the treatment of liver malignancies. MATERIALS AND METHODS: In this retrospective study, 56 hepatic tumours in 48 patients (23 men, 25 women; mean age: 59.6 years) were treated using a new high-frequency MWA-system with ECSEC. Parameters evaluated were technical success, technical efficacy, tumour diameter, tumour and ablation volume, complication rate, 90-day mortality, local tumour progression (LTP) at the 12-month follow-up, ablative margin and ablation zone sphericity. These parameters were compared using the Kruskal-Wallis test with the same parameters collected retrospectively from cohorts of patients treated with conventional high-frequency (HF) MWA (n = 20) or low-frequency (LF) MWA (n = 20). RESULTS: Technical success was achieved in all interventions. The technical efficacy was 100% (ECSEC) vs. 100% (LF-MWA) vs. 95% (HF-MWA). There were no intra-procedural deaths or major complications. Minor complications occurred in 3.57% (2/56), 0% (0/20) and 0% (0/20) of the patients, respectively. The one-year mortality rate was 16.1% (9/56), 15% (3/20) and 10% (2/20), respectively. The LTP was 3.57% (2/56), 5% (1/20) and 5% (1/20), respectively. The median deviation from ideal sphericity (1.0) was 0.135 (ECSEC) vs. 0.344 (LF-MWA) vs. 0.314 (HF-MWA) (p < 0.001). The absolute minimal ablative margin was 8.1 vs. 2.3 vs. 3.1 mm (p < 0.001). CONCLUSIONS: Microwave ablation of liver malignancies is a safe and efficient treatment independent of the system used. Hepatic MWA with ECSEC achieves significantly more spherical ablation zones and higher minimal ablative margins.

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OBJECTIVE: Computed tomography (CT)-guided radiofrequency ablation (RFA) results in a high radiation dose. This study aimed to assess low-dose CT protocols for guiding RFA and oncologic outcomes for the treatment of small renal cell carcinoma (RCC). MATERIALS AND METHODS: Between December 2011 and December 2014, CT-guided RFA was performed in 31 patients with 31 biopsy-proven RCCs (median, 2.1 cm). RFA included planning, targeting, monitoring and survey phases. The dose length product (DLP), CT dose index volume (CTDIvol), effective dose, number of scans, scan range, tube current and exposure time of RFA phases were compared. The 3-year recurrence-free survival rate was recorded. Nonparametric or parametric repeated-measures ANOVA with Dunn's or Tukey-Kramer multiple comparisons and Kaplan-Meier analysis were used for statistical analysis. RESULTS: The median total DLP, CTDIvol and effective dose of CT-guided RFA procedures per session were 1238.8 mGy (range 517.4-3391.7 mGy), 259.7 mGy (10.7-67.9 mGy) and 18.6 mSv (7.8-50.9 mSv), respectively. The median DLP, CTDIvol, effective dose, number of scans, tube current and exposure time during the targeting phase were higher than those during the other phases (p < 0.001). The scan range in the targeting phase was the same as that in the monitoring phase (p > 0.05) but smaller than those in the planning and survey phases (p < 0.001). The 3-year recurrence-free survival rate was 96.7%. CONCLUSIONS: Low-dose CT protocols for guiding RFA may reduce radiation dose without compromising oncologic outcomes. Reducing the number of scans during the targeting phase contributes to dose reduction.

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OBJECTIVE: To evaluate the clinical efficacy/safety of CT-guided percutaneous microwave ablation for HCC in challenging locations using high-power microwave platforms. MATERIALS AND METHODS: A retrospective review was conducted in 26 patients with 36 HCC tumours in challenging locations (hepatic dome, subcapsular, close to the heart/diaphragm/hepatic hilum, exophytic) undergoing CT-guided percutaneous microwave ablation in a single centre since January 2011. Two different microwave platforms were used both operating at 2.45 GHz: AMICA and Acculis MWA System. Patient demographics including age, sex, tumour size and location, as well as technical details were recorded. Technical success, treatment response, patients survival and complication rate were evaluated. RESULTS: Treated tumours were located in the hepatic dome (n = 14), subcapsularly (n = 16), in proximity to the heart (n = 2) or liver hilum (n = 2), while two were exophytic tumours at segment VI (n = 2). Mean tumour diameter was 3.30 cm (range 1.4-5 cm). In 3/26 patients (diameter >4 cm), an additional session of DEB-TACE was performed due to tumour size. Technical success rate was 100%; complete response rate was recorded in 33/36 tumours (91.6%). According to Kaplan-Meier analysis, survival rate was 92.3% and 72.11% at 24- and 60-month follow-up, respectively. There were no major complications; two cases of minor pneumothorax and two cases of small subcapsular haematoma were resolved only with observation requiring no further treatment. CONCLUSION: CT-guided percutaneous microwave ablation for hepatocellular carcinoma tumours in challenging locations and up to 5 cm in diameter can be performed with high efficacy and safety rates.

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INTRODUCTION: Non-muscle invasive bladder cancer (NMIBC) is a highly recurrent disease with potential progression to muscle invasive disease despite the standard bladder instillations with mitomycin C (MMC) or Bacille Calmette-Guérin immunotherapy. Therefore, alternatives such as radiofrequency-induced chemohyperthermia (RF-CHT) with MMC are being investigated. The mechanism explaining the efficacy of RF-CHT is only partly understood. We examined whether RF-CHT results in higher MMC tissue concentrations as compared to cold MMC instillation. PATIENTS AND METHODS: Prior to a planned transurethral resection of bladder tumour (TURBT), patients with stage Ta NMIBC were allocated to either (1) cold MMC instillation or (2) RF-CHT. After MMC instillation, three biopsies were taken of both normal and tumour tissue. Biopsies were snap-frozen and MMC tissue concentrations were analysed using ultra-performance liquid chromatography. RESULTS: Eleven patients were included of which six received RF-CHT. Ten patients had TaG2-LG/HG papillary tumours at pathology. One patient in the RF-CHT group appeared to be free of malignancy and was excluded from the analysis as no tumour biopsies were available. The median MMC concentration in tumour tissue was higher in the RF-CHT group (median 665.00 ng/g vs. 63.75 ng/g, U = 51.0, p = 0.018). Moreover, in both techniques the MMC concentration was lower in normal tissue compared to tumour tissue. Tissue MMC concentration measurements varied substantially within, and between, different patients from the same group. CONCLUSION: Intravesical RF-CHT results in higher tumour MMC concentrations vs. cold MMC instillation which contributes to its superior efficacy.

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PURPOSE: The risk factors of pneumothorax after lung radiofrequency (RF) ablation are long known. The objective was to demonstrate that the visualisation of an aeric RF path after the needle withdrawal was predictive of pneumothorax occurrence and chest tube placement. MATERIALS AND METHODS: A total of 70 patients were retrospectively included in this study. For each patient, we determined the pneumothorax risk factors (age, gender, previous surgery, emphysema, lesion size, distance between pleura and lesion), visualisation of a RF track, length and thickness, presence of pneumothorax, volume, chest tube placement, duration of drainage and hospital stay. RESULTS: Among 70 patients included retrospectively, 26 needed a chest tube placement (37%). Considering the group with path visualisation (37 patients, group A) and the patients without path visualisation (group B), the 2 groups were comparable for pneumothorax risk factors. Considering the patients who needed a chest drain, the visualisation of the path was significatively more important (23 cases, 88.4%) (p< 10-3) than in the group without (8 patients, 31.8%). Multivariate analyses were significant in the three analyses after adjustments on the risk factors for the occurrence of pneumothorax. Incidence of drains was significantly more (p < 10-3) important in group A (23 drainages 62%) than in group B (4 drainages or 12%). The length and thickness of the tracks were not predictable of drain placement. CONCLUSIONS: Besides the well-known risk factors of severe pneumothorax after lung RFA, the simple visualisation of an aeric path just after the RF needle withdrawal is significantly associated with chest tube placement and can be considered as a risk factor as itself.

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OBJECTIVE: We evaluated long-term follow-up results of radiofrequency ablation of benign thyroid nodules to analyse the role of marginal vital tissue on nodule regrowth. MATERIALS AND METHODS: We reviewed the medical records of 54 patients who underwent radiofrequency ablation between June 2008 and November 2013 with pressure symptoms, and/or cosmetic problems. All patients were followed up at least 12 months on three occasions. To evaluate an early sign of regrowth, three types of nodule volumes (total volume, ablated volume and vital volume) were measured and calculated using ultrasonography. Regrowth was defined as a more than a 50% increase in the total volume and vital volume increase was defined as a more than 50% increase compared to the previously reported smallest volume on ultrasonography. RESULTS: The mean follow-up period was 39.4 ± 21.7 (range, 13-87) months. Vital volume increases occurred in 31 nodules (57.4%) and there was regrowth in 13 nodules (24.1%). The mean timing of the vital volume increase was 27.5 ± 18.5 months, and for regrowth it was 39.9 ± 17.5 months. Vital volume increase tended to precede regrowth. CONCLUSION: Vital volume increase tended to occur earlier than regrowth and might be an early sign of regrowth in following-up after the radiofrequency ablation of benign thyroid nodules.

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OBJECTIVES: The incidence of pneumothorax is 7 times higher after lung radiofrequency ablation (RFA) than after lung biopsy. The reasons for such a difference have never been objectified. The histopathologic changes in lung tissue are well-studied and established for RF in the ablation zone. However, it has not been previously described what the nature of thermal injury might be along the shaft of the RF electrode as it traverses through normal lung tissue to reach the ablation zone. The purpose of this study was to determine the changes occurring around the RF needle along the pathway between the ablated zone and the pleura. MATERIAL AND METHODS: In 3 anaesthetised and ventilated swine, 6 RFA procedures (right and left lungs) were performed using a 14-gauge unipolar multi-tined retractable 3 cm radiofrequency LeVeen probe with a coaxial introducer positioned under CT fluoroscopic guidance. In compliance with literature guidelines, we implemented a gradually increasing thermo-ablation protocol using a RF generator. Helical CT images were acquired pre- and post-RFA procedure to detect and evaluate pneumothorax. Four percutaneous 19-gauge lung biopsies were also performed on the fourth swine under CT guidance. Swine were sacrificed for lung ex vivo examinations, scanning electron microscopy (SEM) and pathological analysis. RESULTS: Three severe (over 50 ml) pneumothorax were detected after RFA. In each one of them, pathological examination revealed a fistulous tract between ablation zone and pleura. No fistulous tract was observed after biopsies. In the 3 cases of severe pneumothorax, the tract was wide open and clearly visible on post procedure CT images and SEM examinations. The RFA tract differed from the needle biopsy tract. The histological changes that are usually found in the ablated zone were observed in the RFA tract's wall and were related to thermal lesions. These modifications caused the creation of a coagulated pulmonary parenchyma rim between the thermo-ablation zone and the pleural space. The structural properties of the damage can explain why the RFA tract is remains patent after needle withdrawal. CONCLUSION: Our study demonstrates for the first time that the changes around the RF needle are the same as in the ablated zone. The damage could create fistulous tracts along the needle path between thermo-ablation zone and pleural space. These fistulas could certainly be responsible for severe pneumothorax that occurs in many patients treated with lung RFA.

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