Comparison of Ablation Area and Change in Functional Liver Reserve after Radiofrequency Ablation for Hepatocellular Carcinoma Using the arfa® and VIVA® Systems

Radiofrequency ablation (RFA) is recommended in Japan for patients with hepatocellular carcinomas (HCCs) one to three in number and ≤3 cm in size. The arfa® and VIVA® RFA systems are widely used for patients with HCC and this retrospective observational study aims to compare their performances. The study included 365 patients with HCCs one to three in number and ≤3 cm in size who underwent RFA using the arfa® system (arfa® group) or the VIVA® system (VIVA® group). The total bilirubin (T-Bil) level after RFA was higher in the arfa® group than in the VIVA® group. With a 3-cm electrode needle, the longest diameter (Dmax) and the shortest diameter were analyzed and found to be greater in the arfa® group than in the VIVA® group. Furthermore, Dmax with the 2.5-cm electrode needle was greater in the arfa® group than in the VIVA® group. Statistically significant differences in the ablation area and in the T-Bil value after RFA were observed between the groups; however, these differences are not considered clinical problems because the difference in the ablation area was only slight and the Child–Pugh score was the same between the groups. Thus, hepatologists can use either of the RFA systems based on their preference.

Surface elevation and ice thickness data between 2012 and 2020 at the ablation area of Artesonraju Glacier, Cordillera Blanca, Perú

We present a representative set of data of interpreted ice thickness and ice surface elevation of the ablation area of the Artesonraju glacier between 2012 and 2020. The ice thickness was obtained by means of Ground Penetrating Radar (GPR), while the surface elevation was by means of automated total stations and mass balance stakes. The results from GPR data show a maximum depth of 235 ± 18 m and a decreasing mean depth ranging from 134 ± 18 m in 2013 to 110 ± 18 m in 2020. Additionally, we estimate a mean ice thickness change rate of −4.2 ± 3.2 m yr−1 between 2014 and 2020 with GPR data alone, which is in agreement with the elevation change in the same period. The latter was estimated with the more accurate surface elevation data, yielding a change rate of −3.2 ± 0.2 m yr−1, and hence, confirming a negative glacier mass balance. The data set can be valuable for further analysis when combined with other data types, and as input for glacier dynamics modeling, ice volume estimations, and GLOF (glacial lake outburst flood) risk assessment. The complete dataset is available at https://doi.org/10.5281/zenodo.5571081 (Oberreuter et al, 2021).

Seasonal Surface Change of Urumqi Glacier No. 1, Eastern Tien Shan, China, Revealed by Repeated High-Resolution UAV Photogrammetry

The seasonal surface changes of glaciers in Tien Shan have seen little prior investigation despite the increase in geodetic studies of multi-year changes. In this study, we analyzed the potential of an Unmanned Aerial Vehicle (UAV) to analyze seasonal surface change processes of the Urumqi Glacier No. 1 in eastern Tien Shan. We carried out UAV surveys at the beginning and the end of the ablation period in 2018. The high-precision evolution of surface elevation, geodetic mass changes, surface velocity, and terminus change in the surveyed ablation area were correspondingly derived in combination with ground measurements, including stake/snow-pit observation and GPS measurement. The derived mean elevation change in the surveyed ablation area was −1.64 m, corresponding to the geodetic mass balance of approximately −1.39 m w.e. during the ablation period in 2018. The mean surface velocity was 3.3 m/yr and characterized by the spatial change of the velocity, which was less in the East Branch than in the West Branch. The UAV survey results were a little less than those from the ground measurements, and the correlation coefficient was 0.88 for the surface elevation change and 0.87 for surface displacement. The relative error of the glacier terminus change was 4.5% for the East Branch and 6.2% for the West Branch. These results show that UAV photogrammetry is ideal for assessing seasonal glacier surface changes and has a potential application in the monitoring of detailed glacier changes.

Feasibility of balloon-based endobiliary radiofrequency ablation under cholangioscopy guidance in a swine model

Although endobiliary radiofrequency ablation (RFA) has demonstrated considerable potential for the treatment of biliary strictures, conventional catheter RFA has several limitations. This study aimed to evaluate the feasibility of a novel cholangioscopy (CS)-guided balloon-based RFA procedure in vivo using a swine model. CS-guided balloon-RFA was performed under endoscopic retrograde cholangiography guidance at target temperatures of 60 ℃ or 70 ℃, which were maintained for 60 s. We evaluated the technical feasibility, adverse events, and histological effects associated with the procedure. Twelve sites were ablated in seven miniature pigs. The CS-guided balloon-RFA procedure was technically successful in all cases without any hindrance. Mucosal changes could be detected during RFA, and the ablation area was identified on CS. Necropsy was performed in four pigs on the same day as the procedure: the tissue samples showed coagulative necrosis, and the entire internal circumference of the bile duct was uniformly ablated. The mean lengths of the ablation area in the samples ablated at 60 °C and 70 °C were 20.64 and 22.18 mm, respectively, while the mean depths were 3.46 and 5.07 mm, respectively. The other three pigs were reared and euthanized and autopsied 35 days after the procedure. The site to be ablated had replaced the granulation tissue and fibrotic changes. No adverse events were observed in any case. CS-guided balloon-RFA appears to be a promising option for treating biliary strictures. This preliminary study could pave the way for the evaluation of this procedure in future human clinical trials.

Development of a thermal model for irreversible electroporation: an approach to estimate and optimize the IRE protocols

Purpose Irreversible electroporation (IRE) is an emerging technique that has drawn attention in the field of cancer treatment. IRE uses non-thermal electric pulses to induce death of cancerous cells. However, recent studies have shown that the application of this technique may result in heating of the tissue. There is still room for improving its efficiency and defining better treatment protocols. This study investigates the optimal IRE protocols that avoiding the thermal damage during the IRE treatment. Methods Electrode and pulse parameter are investigated. Finite element models are created to evaluate the ablation area and the temperature changes in the tissue. The model is validated experimentally in bovine liver tissue, while the parameters were optimized using response surface method (RSM). Results From analysis of variance, the parameter of electrode distance and input voltage has significant effect to the temperature rise in the IRE treatment of bovine liver (P = 0.020 and P = 0.003 respectively). Meanwhile, only the input voltage significantly affects the ablation area (P < 0.001). The optimal result from RSM showed that for maximum ablation area 250.82mm2 with no thermal damage, the IRE protocol consisted of an active electrode length of 10 mm, a distance between electrodes of 10 mm, and the delivery of 50 pulses of 41.21 µs and 3000 V. Conclusions The approach presented in this study allows the optimization of the IRE protocols. An optimal IRE protocol that maximizes the ablation area was successfully calculated which can be applied with no risk of thermal damage to the tissue.

Spatio-Temporal Changes of Mass Balance in the Ablation Area of the Muz Taw Glacier, Sawir Mountains, from Multi-Temporal Terrestrial Geodetic Surveys

The glaciers in the Sawir Mountains are an important freshwater resource, and glaciers have been experiencing a continuing retreat over the past few decades. However, studies on detailed glacier mass changes are currently sparse. Here, we present the high-precision evolution of annual surface elevation and geodetic mass changes in the ablation area of the Muz Taw Glacier (Sawir Mountains, China) over the latest three consecutive mass-balance years (2017–2020) based on multi-temporal terrestrial geodetic surveys. Our results revealed clearly surface lowering and negative geodetic mass changes, and the spatial changing patterns were generally similar for the three periods with the most negative surface lowering (approximately −5.0 to −4.0 m a−1) around the glacier terminus. The gradient of altitudinal elevation changes was commonly steep at the low elevations and gentle in the upper-elevation parts, and reduced surface lowering was observed at the glacier terminus. Resulting emergence velocities ranged from 0.11 to 0.86 m a−1 with pronounced spatial variability, which was mainly controlled by surface slope, ice thickness, and the movement of tributary glaciers. Meanwhile, emergence velocities slightly compensated the surface ablation at the ablation area with a proportion of 14.9%, and dynamic thickening had small contributions to glacier surface evolution. Limited annual precipitation and glacier accumulation may result in these weak contributions. Higher-resolution surveys at the seasonal and monthly scales are required to get insight into the mass balance processes and their mechanism.

Quantifying and characterising contemporary rockfall supply to a debris-covered glacier catchment

&lt;p&gt;Supraglacial debris extent and thickness is an important control on the ablation rate of a debris-covered glacier. Debris is supplied to the surface of a debris-covered glacier through several pathways with the primary source of this debris originating from rockfall in both the accumulation area, where debris is transported englacially downglacier, and the upper ablation area, where debris remains in the supraglacial environment while transported downglacier. Current quantification of debris supply to debris-covered glaciers is limited to headwall erosion rates determined through the dating of headwall derived supraglacial debris using &lt;sup&gt;10&lt;/sup&gt;Be concentrations, or estimations of these rates using a ratio of supraglacial debris flux to the headwall catchment area. To increase the knowledge of the contemporary short-term estimations of these processes, repeat LiDAR scans of debris-contributing slopes were acquired during a single ablation season in both July and September at Miage Glacier, Italy. An area of ~7.7 km&lt;sup&gt;2&lt;/sup&gt; comprising &gt; 1.8 billion 3D points was scanned per survey epoch, covering ~33% of the glacierised area of Miage Glacier. Sequential scans were co-registered using an iterative closest point adjustment algorithm within CloudCompare. Manual filtering was used to remove snow, artefacts, and the glacier surface from the raw point clouds. To ease processing, the rock walls were segmented both horizontally and vertically within the catchment. Change detection was carried out using the M3C2 algorithm at a projection scale of 0.3 m and point clouds representing areas of significant change within the segment were obtained using a distributed 95&lt;sup&gt;th&lt;/sup&gt; percentile confidence interval. The DBSCAN clustering algorithm was used to identify individual rockfall clusters, and the volume of each rockfall was calculated using both an iterative alpha-shapes approach. Finally, a bounding box approach was used to estimate the a, b and c axes and therefore shape of the individual rockfalls. Increasing the projection scale used within the M3C2 algorithm decreases the frequency of significant rockfalls found exponentially, and an iterative alpha shapes approach is the most computationally efficient volume estimation method. Our results show that the Miage Glacier catchment is dominated by small scale rockfall events, although at least one large-scale rockfall event is evident in the upper ablation area (validated by time-lapse imagery). This failure on a recently deglaciated area of rock wall highlights that slope response to glacial erosion can be rapid following periods of deglaciation.&lt;/p&gt;

Changes in the Ice-Front Position and Surface Elevation of Glaciar Pío XI, an Advancing Calving Glacier in the Southern Patagonia Icefield, From 2000–2018

Glaciar Pío XI has advanced and thickened over the past several decades in contrast to the generally retreating and thinning trends seen in other glaciers in the Southern Patagonia Icefield (SPI). To quantify recent changes in ice-front positions and glacier surface elevation over the ablation area of Glaciar Pío XI, we analyzed satellite data acquired from 2000 to 2018. Two major glacier termini, and most of the small outlet glaciers, showed advancing trends, including the largest advance (1,400 m), observed at the southern terminus during the study period. Surface elevation increased by 37.3 ± 0.4 m as a mean over the study area, and the rate of the increase accelerated by 135 ± 10% from Period 1 (2000–2007) to Period 2 (2007–2017/18). Elevation change during Period 1 was only slightly positive except for extraordinary thickening (∼20 m a−1) observed near the southern terminus and one of the outlet glacier fronts, whereas significant thickening (∼2.7 m a−1) occurred over the entire ablation area during Period 2. Satellite imagery showed an emergence of sedimentary mounds in front of the southern terminus, suggesting that reduction in frontal ablation and increasingly compressive flow regime are the main drivers of the recent rapid thickening and advance. Most likely, the influence of the sediment deposition on the southern terminus subsequently propagated to the northern terminus and upper reaches of the glacier. The rate of ice mass increase during the study period was 0.48 ± 0.03 Gt a−1, which corresponds to 4% of the total mass loss from the SPI from 2000 to 2015/16.

Continuous borehole optical televiewing reveals variable englacial debris concentrations at Khumbu Glacier, Nepal

Surface melting of High Mountain Asian debris-covered glaciers shapes the seasonal water supply to millions of people. This melt is strongly influenced by the spatially variable thickness of the supraglacial debris layer, which is itself partially controlled by englacial debris concentration and melt-out. Here, we present measurements of deep englacial debris concentrations from debris-covered Khumbu Glacier, Nepal, based on four borehole optical televiewer logs, each up to 150 m long. The mean borehole englacial debris content is ≤ 0.7% by volume in the glacier’s mid-to-upper ablation area, and increases to 6.4% by volume near the terminus. These concentrations are higher than those reported for other valley glaciers, although those measurements relate to discrete samples while our approach yields a continuous depth profile. The vertical distribution of englacial debris increases with depth, but is also highly variable, which will complicate predictions of future rates of surface melt and debris exhumation at such glaciers.