OBJECTIVE: Percutaneous thermal ablation is an effective treatment for primary and metastatic liver tumors and is a recommended local therapy for early-stage hepatocellular carcinoma (HCC). Reported evidence shows an increase in the ablation zone volume over the first 24-h post-liver ablation. This report compares ablation zone volumes immediately at the completion (T = 0) of 26 microwave ablations of liver tumors to 24-h post-procedure (T = 24) volumes.
METHODS: 20 patients, 13 (65%) males, underwent a total of 26 hepatic microwave ablations (MWA) under ultrasound guidance. Contrast-enhanced CT (CECT) or MRI was performed immediately and another CECT 24 h post operatively. Evaluation of the ablation zone and comparison of the two post-operative scans were done using BioTrace software. The expansion of ablation zones on post-op CECTs was matched point by point per direction. The distance between each 2 points was measured and grouped by distance. The incidence of each specific distance was then converted into a percentage, first for each case separately, then for all cases altogether. Data were tested by a matched paired one-sided t test.
RESULTS: The median lesion diameter was 1.5 cm (range 0.5-3.3) with 16 (62%) HCC cases and 9 hepatic metastases (4 neuroendocrine carcinoma, 4 colorectal carcinomas, 1 breast carcinoma, 1 pancreatic cancer). The data show a consistent volume expansion greater than 30% (p = 7.7e-5) 24-h post-ablation, where the median expansion is 57%. Distances between T = 0 and T = 24 equal to 3-7 mm occur in over 35% of the cases.
CONCLUSIONS: The ablation zone expansion at 24-h post-op was not uniform. The final ablation zone is difficult to predict at the time of the procedure. The awareness of the ablation zone expansion is important when treating near-critical structures, managing the heat sink effect, and preserving liver parenchyma.

UNASSIGNED: Microwave ablation (MWA) is a standard percutaneous local therapy for hepatocellular carcinoma (HCC). Next-generation MWA is reported to create a more spherical ablation zone than radiofrequency ablation (RFA). We compared the ablation zone and aspect ratio of two 2.45 GHz MWA ablation probes; Emprint® (13G) and Mimapro® (17G). We compared the ablation zone to the applied energy after MWA in patients with hepatocellular carcinoma (HCC). Furthermore, we investigated local recurrence.
UNASSIGNED: We included 20 patients with HCC, with an average tumour diameter of 33.2 ± 12.2 mm, who underwent MWA using Emprint®, and 9 patients who underwent MWA using Mimapro® with an average tumour diameter of 31.1 ± 10.5 mm. Both groups underwent the same ablation protocol using the same power settings. The images obtained after MWA showed the treatment ablation zone and aspect ratio, which were measured and compared using three-dimensional image analysis software.
UNASSIGNED: The aspect ratios in the Emprint® and Mimapro® groups were 0.786 ± 0.105 and 0.808 ± 0.122, respectively, with no significant difference (p = 0.604). The ablation time was significantly shorter in the Mimapro® group than in the Emprint® group, and there was no significant difference in the frequency of popping or the ablation volume. There were no significant differences in local recurrence between the two groups.
UNASSIGNED: There was no significant difference in the aspect ratios of the ablation diameter, and the ablation zone was almost spherical in both cases. Mimapro® at 17G was less invasive than Emprint® at 13G.

Thermal ablation offers a minimally invasive alternative in the treatment of hepatic tumours. Several types of ablation are utilised with different methods and indications. However, to this day, ablation size remains limited due to the formation of a central non-conductive boundary layer. In thermal ablation, this boundary layer is formed by carbonisation. Our goal was to prevent or delay carbonisation, and subsequently increase ablation size. We used bovine liver to compare ablation diameter and volume, created by a stand-alone laser applicator, with those created when utilising a spacer between laser applicator and hepatic tissue. Two spacer variants were developed: one with a closed circulation of cooling fluid and one with an open circulation into hepatic tissue. We found that the presence of a spacer significantly increased ablation volume up to 75.3 cm3, an increase of a factor of 3.19 (closed spacer) and 3.02 (open spacer) when compared to the stand-alone applicator. Statistical significance between spacer variants was also present, with the closed spacer producing a significantly larger ablation volume (p < 0.001, MDiff = 3.053, 95% CI[1.612, 4.493]) and diameter (p < 0.001, MDiff = 4.467, 95% CI[2.648, 6.285]) than the open spacer. We conclude that the presence of a spacer has the potential to increase ablation size.

OBJECTIVE: To evaluate the effect of Hashimoto\'s thyroiditis (HT) on the extent of ablation zone in ultrasound (US)-guided radiofrequency ablation (RFA) for early stages of papillary thyroid microcarcinoma (PTMC).
METHODS: We selected 772 patients with 797 PTMCs who underwent with RFA from August 2017 to August 2020. They were subdivided into two groups as follows: (i) 216 patients (224 PTMCs) with HT in the \'HT + PTMC\' group and (ii) 556 patients (573 PTMCs) with healthy thyroid in the \'PTMC\' group. We assessed the extent (maximum diameter and volume) of the ablation zone by contrast-enhanced ultrasound (CEUS) immediately, one day, and 1 week following RFA.
RESULTS: The ablation zone of the \'HT + PTMC\' group was smaller than that of the \'PTMC\' group at 1 week of RFA (maximum diameter: 14.6 ± 3.1 mm vs. 15.2 ± 3.2 mm and volume: 0.932 ± 0.498 mL vs. 1.028 ± 0.540 mL, respectively, p < .05). However, there were no differences before, immediately, and one day post-RFA (p > .05). Life-threatening complications did not develop in any of the patients.
CONCLUSIONS: RFA-treated PTMCs were smaller in size in patients with HT than in those with a healthy thyroid at 1 week of RFA. However, the exact mechanism underlying this phenomenon and its clinical significance warrant further investigation.

To explore the differences in ablation zone between liver cirrhosis and normal liver background and investigate the effect of hepatic blood flow on ablation zone of RFA.
Between 2017 and 2019, 203 patients who had liver malignancies and underwent percutaneous RFA with Celon bipolar electrodes enrolled into this study. There were 90 patients had liver cirrhosis and 113 patients had normal liver background. They were 63 females and 140 males with average age of 59.0 ± 10.9 years old. Contrast-enhanced CT/MRI was used to evaluate the ablation zone in one month after RFA. The hepatic flow measurements on CDFI and CEUS were performed before RFA. Correlations between ablation zone versus hepatic flow were assessed using multiple linear regression analysis.
The average ablation zone in cirrhotic liver was significantly larger than those in normal liver background with 3 cm tip of RF electrodes (length 3.5 ± 0.5 vs 3.1 ± 0.4 cm, p = 0.001; width 2.6 ± 0.3 vs 2.2 ± 0.3 cm, p < 0.001; thickness 2.5 ± 0.3 vs 2.0 ± 0.2 cm, p < 0.001). The similar result was found with three 4 cm tip of RF electrodes (width 3.6 ± 0.5 vs 3.1 ± 0.5 cm, p = 0.019; thickness 3.3 ± 0.5 vs 2.7 ± 0.5 cm, p = 0.002). The multiple linear regression analysis showed arrive time of hepatic vein and portal vein was statistically associated with ablation zone with 3 cm electrodes (p < 0.001, p = 0.001), but explained part of the variance (Adjusted R2=0.294, adjusted R2=0.212).
The ablation zones of RFA with multi-bipolar electrodes in liver cirrhosis were significantly larger than those in normal liver background, being up to 6 mm in thickness. The hepatic flow parameters partly contributed to the ablation zone.

In this study, a microwave-induced ablation zone (thermal lesion) monitoring method based on ultrasound echo decorrelation imaging was proposed. A total of 15 cases of ex vivo porcine liver microwave ablation (MWA) experiments were carried out. Ultrasound radiofrequency (RF) signals at different times during MWA were acquired using a commercial clinical ultrasound scanner with a 7.5-MHz linear-array transducer. Instantaneous and cumulative echo decorrelation images of two adjacent frames of RF data were calculated. Polynomial approximation images were obtained on the basis of the thresholded cumulative echo decorrelation images. Experimental results showed that the instantaneous echo decorrelation images outperformed conventional B-mode images in monitoring microwave-induced thermal lesions. Using gross pathology measurements as the reference standard, the estimation of thermal lesions using the polynomial approximation images yielded an average accuracy of 88.60%. We concluded that instantaneous ultrasound echo decorrelation imaging is capable of monitoring the change of thermal lesions during MWA, and cumulative ultrasound echo decorrelation imaging and polynomial approximation imaging are feasible for quantitatively depicting thermal lesions.