Image-guided microwave ablation of hepatocellular carcinoma (≤5.0 cm): is MR guidance more effective than CT guidance?
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Abstract Background Given their widespread availability and relatively low cost, percutaneous thermal ablation is commonly performed under the guidance of computed tomography (CT) or ultrasound (US). However, such imaging modalities may be restricted due to insufficient image contrast and limited tumor visibility, which results in imperfect intraoperative treatment or an increased risk of damage to critical anatomical structures. Currently, magnetic resonance (MR) guidance has been proven to be a possible solution to overcome the above shortcomings, as it provides more reliable visualization of the target tumor and allows for multiplanar capabilities, making it the modality of choice. Unfortunately, MR-guided ablation is limited to specialized centers, and the cost is relatively high. Is ablation therapy under MR guidance better than that under CT guidance? This study retrospectively compared the efficacy of CT-guided and MR-guided microwave ablation (MWA) for the treatment of hepatocellular carcinoma (HCC ≤ 5.0 cm). Methods In this retrospective study, 47 patients and 54 patients received MWA under the guidance of CT and MR, respectively. The inclusion criteria were a single HCC ≤ 5.0 cm or a maximum of three. The local tumor progression (LTP), overall survival (OS), prognostic factors for local progression, and safety of this technique were assessed. Results All procedures were technically successful. The complication rates of the two groups were remarkably different with respect to incidences of liver abscess and pleural effusion ( P < 0.05). The mean LTP was 44.264 months in the CT-guided group versus 47.745 months in the MR-guided group of HCC ( P = 0.629, log-rank test). The mean OS was 56.772 months in the patients who underwent the CT-guided procedure versus 58.123 months in those who underwent the MR-guided procedure ( P = 0.630, log-rank test). Multivariate Cox regression analysis further illustrated that tumor diameter (< 3 cm) and the number of lesions (single) were important factors affecting LTP and OS. Conclusions Both CT-guided and MR-guided MWA are comparable therapies for the treatment of HCC (< 5 cm), and there was no difference in survival between the two groups. However, MR-guided MWA could reduce the incidence of complications.Keywords:
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(1) Background: Percutaneous microwave ablation (MWA) is an accepted treatment of non-operative liver cancer. This study compares the ablation zones of four commercially available 2.45 GHz MWA systems (Emprint, Eco, Neuwave, and Solero) in an ex vivo porcine liver model. (2) Methods: Ex vivo porcine livers (n = 85) were obtained. Two ablation time setting protocols were evaluated, the manufacturer’s recommended maximum time and a 3 min time, performed at the manufacturer-recommended maximum power setting. A total of 236 ablation samples were created with 32 (13.6%) samples rejected. A total of 204 samples were included in the statistical analysis. (3) Results: For single-probe protocols, Emprint achieved ablation zones with the largest SAD. Significant differences were found in all comparisons for the 3 min time setting and for all comparisons at the 10 min time setting except versus Neuwave LK15 and Eco. Emprint produced ablation zones that were also significantly more spherical (highest SI) than the single-probe ablations from all other manufacturers. No statistical differences were found for ablation shape or SAD between the single-probe protocols for Emprint and the three-probe protocols for Neuwave. (4) Conclusions: The new Emprint HP system achieved large and spherical ablation zones relative to other 2.45 GHz MWA systems.
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Objectives To compare sizes and shapes of ablation zones resulting from hydrochloric acid infusion radiofrequency ablation (HRFA) and microwave ablation (MWA), using normal saline infusion radiofrequency ablation (NSRFA) as a control, at a variety of matched power settings and ablation durations, in an ex vivo bovine liver model.Methods A total of 90 ablation procedures were performed, using each of three modalities: NSRFA, HRFA, and MWA. For each modality, five ablation procedures were performed for each combination of power (80 W, 100 W, or 120 W) and duration (5, 10, 20, 30, 45, or 60 min). The size of ablation zones were compared using ANOVA, the Kruskal-Wallis test, or generalized linear regression.Results For ablation durations up to 30 min, mean transverse diameter (TD) after HRFA and MWA did not differ significantly (β = 0.13, p = .20). For ablation durations greater than 30 min, mean TD was significantly larger after HRFA than after MWA (β = 1.657, p < .001). The largest TD (9.46 cm) resulted from HRFA performed with 100 W power for 60 min.Conclusions Compared to MWA, monopolar HRFA with power settings of 80 W–120 W and durations of less than 30 min showed no significant difference. When duration of more than 30 min, HRFA created larger ablation zones than MWA.
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Objectives The aim of this study was to compare the differences between the ablation region and hyperechoic zones in microwave and radio frequency ablation of different tissues. Methods Microwave and radio frequency ablation were performed on fresh porcine muscle and liver with different power levels for 90 seconds. These 2 ablation methods were then performed on rabbit liver in vivo using 20 W for 60 seconds. The volumes of the ablation and hyperechoic zones were compared following different ablation methods. Results The ablation zones were significantly greater than the hyperechoic zones ( P < .05) with the same power and duration when using 2 ablation methods. The differences of the ablation and hyperechoic zones between muscle and liver tissues were significantly different ( P < .05). The difference values of the ablation and hyperechoic zones were also significantly different ( P < .05) using 2 ablation methods. Conclusions The hyperechoic zone may have underestimated the extent of ablation using a specified ablation time. In the same tissue, the hyperechoic zone could more accurately estimate the ablation zones using microwave ablation.
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To retrospectively compare and evaluate ablation zone volume and its reduction from baseline to 1 month follow-up post-percutaneous microwave ablation (MWA) between healthy and cirrhotic liver parenchyma.Institutional database research identified 84 patients (118 hepatic tumors) who underwent percutaneous MWA with the same system. Caudal-right lobe ratio was applied to distinguish cirrhotic (n = 51) and healthy (n = 67) group; ITK-SNAP software was used to quantify ablation zone volume. Long (LAD) and short 1 (SAD-1) and 2 (SAD-2) axis, tumor size diameter (mm) and volume (cm³) of the ablation zones were evaluated for each treated lesion in both groups at baseline (immediately post-ablation) and at 1 month follow-up.There was no significant difference comparing ablation zone volumes at baseline (healthy group: mean ablation volume 14.84 cm³ vs cirrhotic group: mean ablation volume 17.85 cm³, p = 0.31) and 1 month post-ablation (healthy group: mean ablation volume 9.15 cm³ vs cirrhotic group: mean ablation volume 11.58 cm³, p = 0.24). When both "healthy" and "cirrhotic" liver group were evaluated independently, there was a significant difference of ablation volumes reduction (p-value < 0.001) from baseline to 1 month follow-up. When both groups were compared based on reduction (35.12-38.34%) there was no significant difference in ablation zone volumes (p-value = 0.77).Percutaneous MWA results in ablation zones of a comparable volume in both healthy and cirrhotic liver parenchyma. Both cirrhotic and healthy liver parenchyma experience a similar significant reduction of ablation zone volume at 1 month post-therapy.This study evaluates and compares the volume of the ablation zone after MWA between healthy and cirrhotic liver parenchyma from baseline to 1 month follow-up and attempts to identify potential differences. It is the first study to demonstrate significant shrinkage of ablation volumes in healthy livers as compared to cirrhotic livers after 4 weeks of follow-up. The results of this study can help us understand the effect of MWA when applied in different backgrounds of liver parenchyma, which could lead to different treatment planning.
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Microwave thermal ablation is under consideration as a minimally invasive modality to treat 10–20 mm benign adrenal adenomas, while preserving normally functioning adjacent adrenal tissue, and returning the gland to a normally functioning status that is under normal regulation. In contrast to applications for tumor ablation, where devices have been developed with the objective of maximizing the size of the ablation zone for treating large tumors, a challenge for adrenal ablation is to minimize thermal damage to non-targeted adrenal tissue and thereby preserve adrenal function. Here, we investigate methods for creating small spherical ablation zones of volumes in the range 0.5–4 cm3 for the treatment of benign adrenal adenomas using water-loaded microwave monopole antennas operating at 2.45 GHz and 5.8 GHz. Coupled electromagnetic and bioheat transfer simulations and experiments in ex vivo tissue were employed to investigate the effect of frequency, applied power, ablation duration, and coolant temperature on the length and width of the ablation zone. Experimental results showed that small spherical ablation zones with diameters in the range of 7.4–17.6 mm can be obtained by adjusting the applied power and ablation duration. Multi-way ANOVA analysis of the experimentally-measured ablation zone dimensions demonstrated that frequency of operation and ablation duration are the primary parameters for controlling the ablation zone length and width, respectively. Additionally, it was demonstrated that the coolant temperature provides another effective parameter for controlling the ablation zone length without affecting the ablation zone width. Our study demonstrates the feasibility of creating small spherical microwave ablation zones suitable for targeting benign adrenal adenomas.
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Microwave thermal ablation is under investigation for minimally invasive treatments. In the cases of small targets, such as adrenal glands, microwave thermal ablation is a valuable alternative to the traditional and more invasive treatments (e.g. surgical procedures, pharmaceutical therapies). In this work, ablation treatments are carried out on ex-vivo liver samples using a custom developed microwave ablation applicator for ablation of small targets. Ablation zones achieved with different treatment settings are analysed. The power and time settings suitable to achieve a small and well controlled ablation zone, are evaluated. Moreover, the temperature increase in different regions of the area under treatment is assessed.
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