Size Of Ablation Zone Research Articles

The Influence of Preablation Embolization Particle Size on the Size of the Microwave Ablation Zone in a Porcine Orthotopic Renal Tumor Model

PurposeTo combine arterial embolization with different embolic agents, followed by microwave ablation (MWA) in a porcine renal tumor (RT), to evaluate the ideal setting to produce the largest change in the size of the ablation zones (AZs). Materials and MethodsIn a transgenic porcine kidney, 32 sites were inoculation with 28 orthotopic RT produced. Experimental groups (23 tumors) underwent angiography with intra-arterial embolization using various embolic materials (calibrated particles from 40 to 1,200 μm and ethiodized oil) to achieve vascular stasis of the RT. MWA using a standard protocol (3 minutes at 65 W) was subsequently performed for all tumors. Next, a gross and histologic ex vivo analysis of the AZ was performed. ResultsControl group AZ volume without prior embolization was 5.24 cm3 (SD ± 0.55). AZs after embolization with 40 μm, 100 μm, 300–500 μm, 900–1,200 μm particles were significantly larger than those with MWA alone (mean, 15.39 cm3 [SD ± 4.54]; P = .002; 11.07 cm3 [SD ± 1.39]; P = .001; 8.68 cm3 [SD ± 0.77]; P = .001; and 9.90 cm3 [SD ± 1.62]; P = .002, respectively). Liquid embolic ethiodized oil emulsion did not create a significant increase in the AZ (5.92 cm3 [SD ± 1.43 cm3]; P = .492). ConclusionsPre-MWA arterial embolization in a porcine RT model produced a statistically significant increase in the AZ when compared with MWA alone. Using smaller particle size embolic material with distal embolization at the tumor arterioles (50–150 μm) produced the largest, almost 3-fold increase in AZ volume.

Assessment of thermochromic phantoms for characterizing microwave ablation devices.

Thermochromic gel phantoms provide a controlled medium for visual assessment of thermal ablation device performance. However, there are limited studies reporting on the comparative assessment of ablation profiles assessed in thermochromic gel phantoms against those in ex vivo tissue. The objective of this study was to compare microwave ablation zones in a thermochromic tissue-mimicking gel phantom and ex vivo bovine liver and to report on measurements of the temperature-dependent dielectric and thermal properties of the phantom. Thermochromic polyacrylamide phantoms were fabricated following a previously reported protocol. Phantom samples were heated to temperatures in the range of 20°C-90°C in a temperature-controlled water bath, and colorimetric analysis of images of the phantom taken after heating was used to develop a calibration between color changes and the temperature to which the phantom was heated. Using a custom, 2.45GHz water-cooled microwave ablation antenna, ablations were performed in fresh ex vivo liver and phantoms using 65W applied for 5min or 10min (n=3 samples in each medium for each power/time combination). Broadband (500MHz-6GHz) temperature-dependent dielectric and thermal properties of the phantom were measured over the temperature range of 22°C-100°C. Colorimetric analysis showed that the sharp change in gel phantom color commences at a temperature of 57°C. Short and long axes of the ablation zone in the phantom (as assessed by the 57°C isotherm) for 65W, 5min ablations were aligned with the extents of the ablation zone observed in ex vivo bovine liver. However, for the 65W, 10min setting, ablations in the phantom were on average 23.7% smaller in the short axis and 7.4 % smaller in the long axis than those observed in ex vivo liver. Measurements of the temperature-dependent relative permittivity, thermal conductivity, and volumetric heat capacity of the phantom largely followed similar trends to published values for ex vivo liver tissue. Thermochromic tissue-mimicking phantoms provides a controlled, and reproducible medium for comparative assessment of microwave ablation devices and energy delivery settings. However, ablation zone size and shapes in the thermochromic phantom do not accurately represent ablation sizes and shapes observed in ex vivoliver tissue for high energy delivery treatments (65W, 10min). One cause for this limitation is the difference in temperature-dependent thermal and dielectric properties of the thermochromic phantom compared to ex vivobovine liver tissue, as reported in the present study.

Safety and efficacy of a novel transbronchial radiofrequency ablation system for lung tumours: One year follow-up from the first multi-centre large-scale clinical trial (BRONC-RFII).

Radiofrequency ablation (RFA) is an emerging treatment of lung cancer, yet it is accompanied by certain safety concerns and operational limitations. This first multi-centre, large-scale clinical trial aimed to investigate the technical performance, efficacy and safety of an innovative transbronchial RFA system for lung tumours. The study enrolled patients with malignant lung tumours who underwent transbronchial RFA using an automatic saline microperfusion system between January 2021 and December 2021 across 16 medical centres. The primary endpoint was the complete ablation rate. The performance and safety of the technique, along with the 1-year survival rates, were evaluated. This study included 126 patients (age range: 23-85 years) with 130 lung tumours (mean size: 18.77 × 14.15 mm) who had undergone 153 transbronchial RFA sessions, with a technique success rate of 99.35% and an average ablation zone size of 32.47 mm. At the 12-month follow-up, the complete ablation rate and intrapulmonary progression-free survival rates were 90.48% and 88.89%, respectively. The results of patients with ground-glass nodules (GGNs) were superior to those of the patients with solid nodules (12-month complete ablation rates: solid vs. pure GGN vs. mixed GGN: 82.14% vs. 100% vs. 96.08%, p = 0.007). No device defects were reported. Complications such as pneumothorax, haemoptysis, pleural effusion, pulmonary infection and pleural pain were observed in 3.97%, 6.35%, 8.73%, 11.11% and 10.32% of patients, respectively. Two subjects died during the follow-up period. Transbronchial RFA utilizing an automatic saline microperfusion system is a viable, safe and efficacious approach for the treatment for lung tumours, particularly for patients with GGNs.

Assessment of thermochromic phantoms for characterizing microwave ablation devices.

Thermochromic gel phantoms provide a controlled medium for visual assessment of thermal ablation device performance. However, there are limited studies reporting on the comparative assessment of ablation profiles assessed in thermochromic gel phantoms against those in ex vivo tissue. The objective of this study was to compare microwave ablation zones in a thermochromic tissue mimicking gel phantom and ex vivo bovine liver, and to report on measurements of the temperature dependent dielectric and thermal properties of the phantom. Thermochromic polyacrylamide phantoms were fabricated following a previously reported protocol. Phantom samples were heated to temperatures in the range of 20 - 90 °C in a temperature-controlled water bath, and colorimetric analysis of images of the phantom taken after heating were used to develop a calibration between color changes and temperature to which the phantom was heated. Using a custom, 2.45 GHz water-cooled microwave ablation antenna, ablations were performed in fresh ex vivo liver and phantoms using 65 W applied for 5 min or 10 min ( n = 3 samples in each medium for each power/time combination). Broadband (500 MHz - 6 GHz) temperature-dependent dielectric and thermal properties of the phantom were measured over the temperature range 22 - 100 °C. Colorimetric analysis showed that the sharp change in gel phantom color commences at a temperature of 57 °C. Short and long axes of the ablation zone in the phantom (as assessed by the 57 °C isotherm) for 65 W, 5 min ablations were aligned with extents of the ablation zone observed in ex vivo bovine liver. However, for the 65 W, 10 min setting, ablations in the phantom were on average 23.7% smaller in short axis and 7.4 % smaller in long axis than those observed in ex vivo liver. Measurements of the temperature dependent relative permittivity, thermal conductivity, and volumetric heat capacity of the phantom largely followed similar trends to published values for ex vivo liver tissue. Thermochromic tissue mimicking phantoms provide a controlled, and reproducible medium for comparative assessment of microwave ablation devices and energy delivery settings, though ablation zone size and shapes may not accurately represent ablation sizes and shapes observed in ex vivo liver tissue under similar conditions.

Patient-Specific Prediction of Immediate Phase Lung Microwave Ablation Zone Size

PurposeTo investigate the effect of patient and tumor-specific characteristics on the size of immediate phase lung microwave ablation (MWA) zone and establish a prediction model. Materials and MethodsThis institutional review board (IRB)–approved, Health Insurance Portability and Accountability Act (HIPAA)–compliant cohort included 164 lesions from 99 patients who underwent computed tomography (CT)–guided lung MWA, and the 2-dimensional elliptical ground-glass opacity ablation zone was measured. Duration, maximum temperature, tumor depth, presence of emphysema, history of ipsilateral lung ablation, surgery, and radiotherapy were recorded. K-fold cross validation with k = 5 and Least Absolute Shrinkage and Selection Operator were used to build prediction models for the major and minor axes and area of the ablation zone. ResultsThe median of immediate phase ablation duration was 2 minutes (interquartile range, 1.5–4.25 minutes) with 65 W of power for all ablations. The mean major and minor axes and area of ablation zone were 3.1 cm (SD ± 0.6), 2.0 cm (SD ± 0.5), and 5.1 cm2 (SD ± 2.1), respectively. The major and minor axes and area of immediate phase ablation zone dimensions were significantly associated with duration (P < .001, P < .001, and P < .001, respectively), maximum temperature (P < .001, P < .001, and P < .001, respectively), tumor depth (P = .387, P < .001, and P < .001, respectively), history of ipsilateral lung ablation (P = .008, P = .286, and P = .076, respectively), and lung radiotherapy (P = .001, P = .042, and P = .015, respectively). The prediction model showed R2 values for major and minor axes and area of the ablation zone to be 0.50, 0.45, and 0.53, respectively. ConclusionsDuration of ablation, maximum temperature, tumor depth, history of ipsilateral lung ablation, surgery, and radiotherapy were significantly associated with the ablation zone dimensions and size and can be used to build the prediction model to approximate the immediate phase lung MWA zone.

Factors Impacting Microwave Ablation Zone Sizes: A Retrospective Analysis.

Evaluation of the influence of intrinsic and extrinsic conditions on ablation zone volumes (AZV) after microwave ablation (MWA). Retrospective analysis of 38 MWAs of therapy-naïve liver tumours performed with the NeuWave PR probe. Ablations were performed either in the 'standard mode' (65 W, 10 min) or in the 'surgical mode' (95 W, 1 min, then 65 W, 10 min). AZV measurements were obtained from contrast-enhanced computed tomography immediately post-ablation. AZVs in the 'standard mode' were smaller than predicted by the manufacturer (length 3.6 ± 0.6 cm, 23% below 4.7 cm; width 2.7 ± 0.6, 23% below 3.5 cm). Ablation zone past the tip was limited to 6 mm in 28/32 ablations. Differences in AZV between the 'surgical mode' and 'standard mode' were not significant (15.6 ± 7.8 mL vs. 13.9 ± 8.8 mL, p = 0.6). AZVs were significantly larger in case of hepatocellular carcinomas (HCCs) (n = 19) compared to metastasis (n = 19; 17.8 ± 9.9 mL vs. 10.1 ± 5.1 mL, p = 0.01) and in non-perivascular tumour location (n = 14) compared to perivascular location (n = 24, 18.7 ± 10.4 mL vs. 11.7 ± 6.1 mL, p = 0.012), with both factors remaining significant in two-way analysis of variance (HCC vs. metastasis: p = 0.02; perivascular vs. non-perivascular tumour location: p = 0.044). Larger AZVs can be expected in cases of HCCs compared with metastases and in non-perivascular locations. Using the 'surgical mode' does not increase AZV significantly.

Prospective Margin Estimates Predict Local Tumor Progression Following Microwave Ablation of Small Renal Masses.

To evaluate the relationship between prospectively generated ablative margin estimates and local tumor progression (LTP) among patients undergoing microwave ablation (MWA) of small renal masses (SRMs). Between 2017 and 2020, patients who underwent MWA for SRM were retrospectively identified. During each procedure, segmented kidney and tumor shapes were coregistered with intraprocedural helical CT images obtained after microwave antenna placement. Predicted ablation zone shape and size were then overlaid onto the resultant model, and a model-to-model distance algorithm was employed to calculate multiple ablative margin estimates. LTP was modeled as a function of each margin estimate by hazard regression. Models were evaluated using hazard ratios and Akaike information criterion. Receiver operating characteristic curve area under the curve was also estimated using Harrell's and Uno's C indices (HI and UI, respectively). One hundred and twenty-eight patients were evaluated (median age 72.1years). Mean tumor diameter was 2.4 ± 0.9cm. LTP was observed in nine (7%) patients. Analysis showed that decreased estimated margin size as measured by first quartile (Q1; 25th percentile), maximum, and average ablative margin metrics was significantly associated with risk of LTP. For every one millimeter increase in Q1, maximum, and mean ablative margin, the hazard of LTP increased 67% (HR: 1.67; 95% CI = 1.25-2.20, UI = 0.93, HI = 0.77), 32% (HR: 1.32; 95% CI 1.09-1.60; UI = 0.93; HI = 0.76), and 48% (HR: 1.48; 95% CI 1.18-1.85; UI = 0.83; HI = 0.75), respectively. Prospectively generated ablative margin estimates can be used to predict the risk of local tumor progression following microwave ablation of small renal masses. LEVEL OF EVIDENCE 3: Retrospective cohort study.

Bipolar radiofrequency ablation lesion areas and confluence: An exvivo study and technical report.

Radiofrequency ablation (RFA) has been used for nearly 100 years, treating an array of medical conditions including chronic pain. Radiofrequency (RF) energy depolarizes and repolarizes tissues adjacent to a probe producing heat and causing direct thermal injury. When positioned adjacent to neural structures, it leads to neural tissue injury and cell death interrupting pain signaling with the ultimate goal of providing lasting pain relief. Today, RFA is commonly used to treat cervical, thoracic, and lumbar zygapophyseal joints, sacroiliac joint, and more recently large peripheral joint-mediated pain. There are several applications of RFA systems, including bipolar, conventional thermal, cooled, protruding, and pulsed. As yet, no study has determined the best technical practice for bipolar RFA. This exvivo study examines RFA lesion midpoint (LMP) area and lesion confluence comparing three different commonly used gauge (g) probes (18-g, 20-g, and 22-g) with 10-mm active tips at various interprobe distances (IPD) to guide best technical practices for its clinical application. Bipolar RFA lesions were generated in preservative-free chicken breast specimens using three different gauge probes (18-g, 20-g, and 22-g) with 10-mm active tips at various IPD (6, 8, 10, 12, 14, 16, and 18 mm). RF was applied for 105 s (15-s ramp time) at 80°C for each lesion at both room and human physiological temperature. The specimen tissues were dissected through the lesion to obtain a length, width, and depth, which were used to calculate the LMP area (mm2 ). The LMP areas of each thermal ablation were investigated using visualization and descriptive analysis. The Kruskal-Wallis test was performed to compare LMP areas between the two temperature groups and the three different gauge probe subgroups at the various IPDs. Of the 36 RF lesions (14: 18-g, 12: 20-g, and 10: 22-g) performed, 24 demonstrated lesion confluence. The average time to reach 80°C was 16-17 s; therefore, the average time of RF-energy delivery (at goal temperature) was 88-89 s despite varying needle size or IPD. Comparing the 25 and 37°C groups, 18-g probes produced mean LMP areas of 73.7 and 79.2 mm2 , respectively; 20-g probes produced mean LMP areas of 66 and 66.8 mm2 , respectively; 22-g probes produced mean LMP areas of 56.6 and 59.7 mm2 , respectively. There was no statistical evidence to state a difference regarding LMP area between temperature groups; however, the 18-g probes produced consistently larger LMP areas in the 37°C compared to 25°C specimen groups at each IPD. Lesion confluence was lost for 18-g, 20-g, and 22-g probes at IPD of 14, 12, and 10 mm, respectively, in both 25 and 37°C groups. LMP area was similar between 6 and 8 mm IPD in all of the three-gauge groups; however, there was a significant drop in LMP area from 8 mm IPD to 10 mm and greater. The 18-g, 20-g, and 22-g probes all demonstrated a sharp decline in LMP area when increasing the IPD from 8 to 10 mm. This exvivo technical study evaluated bipolar RFA LMP areas and lesion confluence, and determined the recommended IPD of 18-g, 20-g, and 22-g probes to be less than 12, 10, and 8 mm, respectively, for best clinical practice. Placing bipolar probes at an IPD greater than 14, 12, and 10 mm, respectively, risks the loss of lesion confluence and failure to produce a clinically significant treatment response due to lack of nerve capture. In clinical practice, the use of injectate may produce larger lesions than demonstrated in this study. Additionally, invivo factors may impact ablation zone size and ablation patterns. As there are a paucity of studies comparing various RFA applications and conventional RFA needles are least expensive, it is possible that bipolar conventional RFA is more cost-effective than other techniques.

A Predictive and an Optimization Mathematical Model for Device Design in Cardiac Pulsed Field Ablation Using Design of Experiments.

Cardiac catheter ablation (CCA) is a common method used to correct cardiac arrhythmia. Pulsed Field Ablation (PFA) is a recently-adapted CCA technology whose ablation is dependent on electrode and waveform parameters (factors). In this work, the use of the Design of Experiments (DoE) methodology is investigated for the design and optimization of a PFA device. The effects of the four factors (input voltage, electrode spacing, electrode width, and on-time) and their interactions are analyzed. An empirical model is formed to predict and optimize the ablation size responses. Based on the ranges tested, the significant factors were the input voltage, the electrode spacing, and the on time, which is in line with the literature. Two-factor interactions were found to be significant and need to be considered in the model. The resulting empirical model was found to predict ablation sizes with less than 2.1% error in the measured area and was used for optimization. The findings and the strong predictive model developed highlight that the DoE approach can be used to help determine PFA device design, to optimize for certain ablation zone sizes, and to help inform device design to tackle specific cardiac arrhythmias.

Morphometric characterization and temporal temperature measurements during hepatic microwave ablation in swine.

Heat-induced destruction of cancer cells via microwave ablation (MWA) is emerging as a viable treatment of primary and metastatic liver cancer. Prediction of the impacted zone where cell death occurs, especially in the presence of vasculature, is challenging but may be achieved via biophysical modeling. To advance and characterize thermal MWA for focal cancer treatment, an in vivo method and experimental dataset were created for assessment of biophysical models designed to dynamically predict ablation zone parameters, given the delivery device, power, location, and proximity to vessels. MWA zone size, shape, and temperature were characterized and monitored in the absence of perfusion in ex vivo liver and a tissue-mimicking thermochromic phantom (TMTCP) at two power settings. Temperature was monitored over time using implanted thermocouples with their locations defined by CT. TMTCPs were used to identify the location of the ablation zone relative to the probe. In 6 swine, contrast-enhanced CTs were additionally acquired to visualize vasculature and absence of perfusion along with corresponding post-mortem gross pathology. Bench studies demonstrated average ablation zone sizes of 4.13±1.56cm2 and 8.51±3.92cm2, solidity of 0.96±0.06 and 0.99±0.01, ablations centered 3.75cm and 3.5cm proximal to the probe tip, and temperatures of 50 ºC at 14.5±13.4s and 2.5±2.1s for 40W and 90W ablations, respectively. In vivo imaging showed average volumes of 9.8±4.8cm3 and 33.2±28.4cm3 and 3D solidity of 0.87±0.02 and 0.75±0.15, and gross pathology showed a hemorrhagic halo area of 3.1±1.2cm2 and 9.1±3.0cm2 for 40W and 90W ablations, respectfully. Temperatures reached 50ºC at 19.5±9.2s and 13.0±8.3s for 40W and 90W ablations, respectively. MWA results are challenging to predict and are more variable than manufacturer-provided and bench predictions due to vascular stasis, heat-induced tissue changes, and probe operating conditions. Accurate prediction of MWA zones and temperature in vivo requires comprehensive thermal validation sets.

Radiofrequency Ablation of Unifocal Papillary Thyroid Microcarcinoma With BRAF V600E Mutation.

To date there is no study on the feasibility of radiofrequency ablation (RFA) for papillary thyroid microcarcinomas (PTMCs) with BRAF V600E mutation. This study was designed to evaluate the efficiency, safety, and prognosis of ultrasound (US)-guided percutaneous RFA for unifocal PTMCs with BRAF V600E mutation. Sixty patients with 60 unifocal BRAF V600E mutation-positive PTMCs who received US-guided RFA between January 2020 and December 2021 were retrospectively analyzed. The mean maximum PTMC tumor diameter was 5.8 ± 1.7 mm (range, 2.5-10.0 mm). All PTMCs were pathologically confirmed by fine needle aspiration or core needle biopsy, and BRAF V600E mutation was confirmed to be positive by real-time fluorescent quantitative polymerase chain reaction. Contrast-enhanced ultrasound (CEUS) was performed immediately after RFA to evaluate whether PTMCs were extendedly ablated. Ultrasound was performed 1, 3, 6, and 12 months after RFA and every 6 months thereafter to evaluate the changes in the ablation zone, local recurrence, and cervical lymph node metastasis (LNM). The complications were recorded and evaluated. Extended ablation was achieved in all enrolled patients. The ablation zone sizes increased immediately after RFA compared with those of tumors before treatment. One month later, the ablation zone sizes were smaller than immediately after RFA. At the last follow-up assessment, 42 nodules (70.0%) completely disappeared and the ablation zones of 18 nodules (30.0%) showed fissure-like changes. No local recurrence or cervical LNM was detected. Voice change (1.7%) was the only major complication. RFA is effective and safe in treating unifocal PTMCs with BRAF V600E mutation, especially when surgery is not feasible or refused by patients who are unwilling to continue active surveillance.

Relative Effects of Various Factors on Ice Ball Formation and Ablation Zone Size During Ultrasound-Guided Percutaneous Cryoneurolysis: A Laboratory Investigation to Inform Clinical Practice and Future Research.

Ultrasound-guided percutaneous cryoneurolysis provides analgesia using cold temperatures to reversibly ablate peripheral nerves. Cryoneurolysis probes pass a gas through a small internal annulus, rapidly lowering the pressure and temperature, forming an ice ball to envelope the target nerve. Analgesia is compromised if a nerve is inadequately frozen, and laboratory studies suggest that pain may be paradoxically induced with a magnitude and duration in proportion with the incomplete ablation. We therefore investigated the relative effects of various factors that may contribute to the size of the ice ball and the effective cryoneurolysis zone. A cryoprobe was inserted into a piece of meat, a gas was passed through for 2min, and the resulting ice ball width (cross-section) and length (axis parallel to the probe) were measured using ultrasound, with the temperature evaluated in nine concentric locations concurrently. The factor with the greatest influence on ice ball size was probe gauge: in all probe types, a change from 18 to 14 increased ice ball width, length, and volume by up to 70%, 113%, and 512% respectively, with minimum internal temperature decreasing as much as from -5 to -32°C. In contrast, alternating the type of meat (chicken, beef, pork) and the shape of the probe tip (straight, coudé) affected ice ball dimensions to a negligible degree. The ice ball dimensions and the zone of adequate temperature drop were not always correlated, and, even within a visualized ice ball, the temperature was often inadequate to induce Wallerian degeneration. Percutaneous probe design can significantly influence the effective cryoneurolysis zone; visualizing a nerve fully encompassed in an ice ball does not guarantee adequate treatment to induce the desired Wallerian degeneration because ice forms at temperatures between 0 and -20°C, whereas only temperatures below -20°C induce Wallerian degeneration. The correlation between temperatures in isolated pieces of meat and perfused human tissue remains unknown, and further research to evaluate these findings in situ appears highly warranted.

Device safety assessment of bronchoscopic microwave ablation of normal swine peripheral lung using robotic-assisted bronchoscopy

Introduction The aim of this study was to assess the safety of bronchoscopic microwave ablation (MWA) of peripheral lung parenchyma using the NEUWAVE™ FLEX Microwave Ablation System, and robotic-assisted bronchoscopy (RAB) using the MONARCH™ Platform in a swine model. Methods Computed tomography (CT)-guided RAB MWA was performed in the peripheral lung parenchyma of 17 Yorkshire swine (40–50 kg) and procedural adverse events (AEs) documented. The acute group (day 0, n = 5) received 4 MWAs at 100 W for 1, 3, 5, and 10 min in 4 different lung lobes. Subacute and chronic groups (days 3 and 30, n = 6 each) received one MWA (100 W, 10 min) per animal. Results The study was completed without major procedural complications. No postprocedural AEs including death, pneumothorax, bronchopleural fistula, hemothorax, or pleural effusions were observed. No gross or histological findings suggestive of thromboembolism were found in any organ. One 3-Day and one 30-Day swine exhibited coughing that required no medication (minor AEs), and one 30-Day animal required antibiotic medication (major AE) for a suspected lower respiratory tract infection that subsided after two weeks. CT-based volumetric estimates of ablation zones in the acute group increased in an ablation time-dependent (1–10 min) manner, whereas macroscopy-based estimates showed an increasing trend in ablation zone size. Conclusion The NEUWAVE FLEX and MONARCH devices were safely used to perform single or multiple RAB MWAs. The preclinical procedural safety profile of RAB MWA supports clinical research of both devices to investigate efficacy in select patients with oligometastatic disease or primary NSCLC.

Vertebral Body Bone Ablation with and without a Saline-Infused System in a Porcine Model

The purpose of this study was to evaluate the effect of bone radiofrequency (RF) ablation in the spine with and without controlled saline infusion. RF ablation with and without controlled saline infusion was performed in the vertebral bodies of 2 swine with real-time temperature and impedance recordings. Histology and magnetic resonance (MR) imaging results were reviewed to evaluate the ablation zone size, breach of spinal canal, and damage to the spinal cord and nerves. There was no difference in maximum and mean temperatures between controlled saline and noninfusion groups. The impedance and power output were not significantly different between the groups. MR imaging and histopathology demonstrated ablation zones confined within the vertebral bodies. Ablation zone size correlated on MR imaging and histopathology by groups. No ablation effect, breach of posterior cortex, spinal cord injury, or nerve or ganglion injury was observed at any level using MR imaging or histology. Controlled saline infusion does not appear to impact bone RF ablation and, specifically, does not increase the ablation zone size.

Dynamic Contrast-Enhanced MR Imaging Evaluation of Perfusional Changes and Ablation Zone Size after Combination Embolization and Ablation Therapy

PurposeThe objectives of this study were to assess the utility of dynamic contrast-enhanced magnetic resonance (MR) imaging in quantifying parenchymal perfusional changes after embolization and to characterize the association between pharmacokinetic (PK) parameters and final microwave ablation volume. Materials and MethodsPK parameters from dynamic contrast-enhanced MR imaging were used to quantify perfusional changes in the liver after transarterial embolization of the right or left lobe in a swine liver model (n = 5). Each animal subject subsequently underwent microwave ablation (60 W for 5 minutes) of the embolized and nonembolized liver lobes. Changes in PK parameters from dynamic contrast-enhanced MR imaging were correlated with their respective final microwave ablation volumes in each liver lobe. ResultsMicrowave ablation volumes of embolized liver lobes were significantly larger than those of nonembolized liver lobes (28.0 mL ± 6.2 vs 15.1 mL ± 5.2, P < .001). PK perfusion parameters were significantly lower in embolized liver lobes than in nonembolized liver lobes (Ktrans = 0.69 min−1 ± 0.15 vs 1.52 min−1 ± 0.37, P < .001; kep = 0.69 min−1 ± 0.19 vs 1.54 min−1 ± 0.42, P < .001). There was a moderate but significant correlation between normalized kep and ablation volume, with each unit increase in normalized kep corresponding to a 9.8-mL decrease in ablation volume (P = .035). ConclusionsPK-derived parameters from dynamic contrast-enhanced MR imaging can be used to quantify perfusional changes after transarterial embolization and are directly inversely correlated with final ablation volume.

Feasibility and Safety of Single-Probe Cryoablation with Liquid Nitrogen: An Initial Experience in 24 Various Tumor Lesions.

Percutaneous cryoablation with liquid nitrogen is a new technique being used in the treatment of some malignant tumors. Our objective was to assess its feasibility in the ablation of tumor lesions of various sizes and locations. This retrospective, monocentric study included all consecutive patients who underwent percutaneous cryoablation with liquid nitrogen between December 2019 and March 2021. Cryoablation was performed using 10G or 13G cryoprobes. The ablation volume was measured on post-treatment CT or MRI. 22 patients (24 lesions) were included, 16 of whom were men (73%), while median age was 66 years. The lesions were located in the bone (42%), kidney (29%), soft tissue (17%), lung (8%), or liver (4%). It was feasible in all tumor locations and produced median ablation zones 25 mm in width and 35 mm in length, with a 23 min median freezing time. Freezing duration was correlated with the ice volume (p Spearman = 0.02), but not with the ablation volume (p = 0.11). The average difference between the ablation zone and ice ball sizes were -6.4 mm in width and -7.7 mm in length. Both ice and ablation volumes were larger when using the 10G probe as compared to when the 13G was used. No complications were reported. We showed that this technique was safe and feasible in all organs tested. The freezing duration was correlated with the ice ball size, but not with the ablation zone.

Safety of CT-Guided Microwave Ablation of Subcardiac Liver Tumors.

The purpose of this study was to investigate the safety of CT-guided microwave ablation (MWA) of subcardiac hepatic tumors. This retrospective study included 19 patients (11 males and 8 females, age: 64.0years (IQR: 58.3, 71.0) who underwent CT-guided MWA of 22 subcardiac tumors from January 2016 through December 2020. The subcardiac tumors consisted of 6 hepatocellular carcinomas and 16 metastases. Hydrodissection or other thermal protection technique was not used during the ablation. Subcardiac ablation was defined as the ablation zone extended ≤ 0.5cm from myocardium or coronary artery. The safety of MWA of subcardiac tumors was evaluated based on procedural and post-procedural complications and intra-procedural ECG changes. Local tumor progression (LTP) was also analyzed and correlated with tumor and ablation zone sizes. The primary efficacy rate was 100%. The median follow-up was 20.5months (IQR: 6.0, 29.8). There was no 30-day mortality. One grade 3 complication occurred (severe shoulder and chest pain), and there were 19 events of grade 1 or 2 complications. No instances of cardiac complications or significant procedural ECG changes were observed. There were 22 events of grade 1 and 2 laboratory toxicity and 1 event of grade 3 elevated bilirubin. The LTP was 13.6% at 1year and 22.7% at 2years. There was no significant correlation between LTP and tumor or ablation zone sizes. CT-guided MWA of subcardiac hepatic tumors is safe, and MWA should be considered as an option for managing subcardiac tumors. LTP rates for MWA of subcardiac tumors may be inferior to ablation of tumors in common location. Cohort Study.

Computed Tomography Evaluation of In Vivo Pulmonary Cryoablation Zone Sizes

PurposeTo evaluate ablation zone sizes in patients undergoing pulmonary tumor cryoablation with 14-gauge cryoablation probes. Materials and MethodsA single-center retrospective analysis of all consecutive patients who underwent cryoablation of pulmonary tumors with 1 or more 14-gauge probes (August 2017 to June 2020) was performed. Intraprocedural and 1–2-month postprocedural chest computed tomography (CT) scans were evaluated to characterize pulmonary lesions, ice balls, and ablation zones. Single-probe 14-gauge ablation zone volumes were compared with manufacturer reference isotherms and single- and 2-probe ablation zones from a prior investigation of 17-gauge probes. Overall survival and local recurrence–free survival were calculated to 3 years. ResultsForty-seven pulmonary malignancies in 42 patients (women, 50%; mean age, 75.2 years ± 11.5) underwent cryoablation with 1 (n = 35), 2 (n = 10), or 3 (n = 2) cryoablation probes. One- to 2-month follow-up CT images were available for 30 of the 42 patients. The mean cryoablation zone volumes at 1–2 months when 1 (n = 21), 2 (n = 8), and 3 (n = 1) probes were used were 5.0 cm3 ± 2.3, 37.5 cm3 ± 20.5, and 28.4 cm3, respectively. The mean single-probe follow-up ablation zone volume was larger than that previously reported for 17-gauge probes (3.0 cm3 ± 0.3) (P < .001) but smaller than manufacturer-reported isotherms (11.6 cm3 for −40 °C isotherm) and the 2-probe ablation zone volume with 17-gauge devices (12.9 cm3 ± 2.4) (for all, P < 001). The 3-year overall survival and local recurrence–free survival were 69% (95% confidence interval [CI], 53%–89%) and 87% (95% CI, 74%–100%), respectively. ConclusionsFourteen-gauge probes generate larger ablation volumes than those generated by 17-gauge probes. Manufacturer-reported isotherms are significantly larger than actual cryoablation zones. Cryoablation can attain low rates of local recurrence.

Abstract No. 543 Ablation volume effects following combined chemolipiodolization and microwave ablation of hepatocellular carcinoma

To evaluate the effects of chemolipiodol uptake on ablation zone size following combined chemolipiodolization and microwave ablation (MWA) of hepatocellular carcinoma (HCC). Prior studies have validated larger ablation zone sizes following transarterial embolization with particles, but there is limited data on ablation zone sizes following chemolipiodolization only.

Microwave Ablation of Liver, Kidney and Lung Lesions: One-Month Response and Manufacturer's Charts' Reliability in Clinical Practice.

Microwave ablation systems allow for performing tumoral destruction in oncology. The objective of this study was to assess the early response and reliability of the microwave ablation zone size at one month for liver, kidney and lung lesions, as compared to the manufacturer’s charts. Patients who underwent microwave ablation with the EmprintTM ablation system for liver, kidney and lung lesions between June 2016 and June 2018 were retrospectively reviewed. Local response and ablation zone size (major, L, and minor, l, axes) were evaluated on the one-month follow-up imaging. Results were compared to the manufacturers’ charts using the Bland–Altman analysis. Fifty-five patients (mean age 68 ± 11 years; 95 lesions) were included. The one-month complete response was 94%. Liver ablations showed a good agreement with subtle, smaller ablation zones (L: −2 ± 5.7 mm; l: −5.2 ± 5.6 mm). Kidney ablations showed a moderate agreement with larger ablations for L (L: 8.69 ± 7.94 mm; l: 0.36 ± 4.77 mm). Lung ablations showed a moderate agreement, with smaller ablations for l (L: −5.45 ± 4.5 mm; l: −9.32 ± 4.72 mm). With 94% of early complete responses, the system showed reliable ablations for liver lesions, but larger ablations for kidney lesions, and smaller for lung lesions.