Microwave ablation (MWA) is a type of minimally invasive cancer therapy that uses heat to induce necrosis in solid tumours. Inter-and post-ablational size changes can influence the accuracy of control imaging, posing a risk of incomplete ablation. The present study aims to explore post-ablation 3D size dynamics in vivo using computed tomography (ct). ten MWA datasets obtained in nine healthy pigs were used. Lesions were subdivided along the z-axis with an additional planar subdivision into eight subsections. The volume of the subsections was analysed over different time points, subsequently colour-coded and three-dimensionally visualized. A locally weighted polynomial regression model (LoeSS) was applied to describe overall size changes, and Student's t-tests were used to assess statistical significance of size changes. The 3D analysis showed heterogeneous volume changes with multiple small changes at the lesion margins over all time points. the changes were pronounced at the upper and lower lesion edges and characterized by initially eccentric, opposite swelling, followed by shrinkage. In the middle parts of the lesion, we observed less dimensional variations over the different time points. LOESS revealed a hyperbolic pattern for the volumetric changes with an initially significant volume increase of 11.6% (111.6% of the original volume) over the first 32 minutes, followed by a continuous decrease to 96% of the original volume (p < 0.05). Microwave ablation (MWA) is a thermoablative procedure for the minimally invasive therapy of solid tumours, primarily in the lungs, kidneys and liver. It uses electromagnetic waves to induce local coagulation necrosis through heat 1-3. During the ablation procedure, high local temperatures of up to 120 °C can be achieved in the target tissue, not only causing protein denaturation but also for example evaporation of the water contained in the tissue and resulting in changes of dielectric and thermal properties as well as structural tissue changes 4-6. Overall, these structural changes can lead to dynamic alterations in lesion morphology and lesion size in the post-ablation period. Tissue shrinkage, primarily caused by dehydration, but also by tissue evaporation and carbonization, is an important change in the ablation area and ought to be considered in post-interventional imaging as it can cause a decrease in lesion volume of up to 30% and could therefore be of clinical relevance 7-9. Contrast-enhanced computed tomography (CECT) is often performed after MWA to determine the size and safety margin of the ablation area in order to ensure complete tumour ablation 10-13. CECT has been shown to allow identification of the central necrotic area of the ablated tissue, which displays little to no contrast medium uptake and thus appears hypodense compared to normal liver tissue (NLT) 14. Recent studies using CECT ex vivo or in vivo demonstrated the shrinkage of ablation zones in the first hours after MWA, but so far, no precise analysis of the dynamic size behaviour has been carried out ...

Background Microwave ablation (MWA) is a minimally invasive treatment option for solid tumors and belongs to the local ablative therapeutic techniques, based on thermal tissue coagulation. So far there are mainly ex vivo studies that describe tissue shrinkage during MWA. Purpose To characterize short-term volume changes of the ablated zone following hepatic MWA in an in vivo porcine liver model using contrast-enhanced computer tomography (CECT). Material and Methods We performed multiple hepatic MWA with constant energy parameters in healthy, narcotized and laparotomized domestic pigs. The volumes of the ablated areas were calculated from venous phase CT scans, immediately after the ablation and in short-term courses of up to 2 h after MWA. Results In total, 19 thermally ablated areas in 10 porcine livers could be analyzed (n = 6 with two volume measurements during the measurement period and n = 13 with three measurements). Both groups showed a statistically significant but heterogeneous volume reduction of up to 12% (median 6%) of the ablated zones in CECT scans during the measurement period (P < 0.001 [n = 13] and P = 0.042 [n = 6]). However, the dimension and dynamics of volume changes were heterogenous both absolutely and relatively. Conclusion We observed a significant short-term volume reduction of ablated liver tissue in vivo. This volume shrinkage must be considered in clinical practice for technically successful tumor treatment by MWA and therefore it should be further investigated in in vivo studies.

BackgroundRadiofrequency ablation (RFA) represents a treatment option for non-resectable liver malignancies. Larger ablations can be achieved with a temporary hepatic inflow occlusion (Pringle maneuver – PM). However, a PM can induce dehydration and carbonization of the target tissue. The objective of this study was to evaluate the impact of an intermittent PM on the ablation size.MethodsTwenty-five multipolar RFAs were performed in porcine livers ex vivo. A perfused glass tube was used to simulate a natural vessel. The following five test series (each n=5) were conducted: (1) continuous PM, (2–4) intermittent PM, and (5) no PM. Ablations were cut into half. Ablation area, minimal radius, and maximal radius were compared.ResultsNo change in complete ablation size could be measured between the test series (p>0.05). A small rim of native liver tissue was observed around the glass tube in the test series without PM. A significant increase of ablation area could be measured on the margin of the ablations with an intermittent PM, starting without hepatic inflow occlusion (p<0.05).ConclusionAn intermittent PM did not lead to smaller ablations compared to a continuous or no PM ex vivo. Furthermore, an intermittent PM can increase the ablation area when initial hepatic inflow is succeeded by a PM.

The Etruscan shrew (Suncus etruscus) is one of the smallest mammals on earth and is used in many fields of research, including physiology, behavioral science and neuroscience. However, establishing and maintaining a breeding colony of thisspecies in the laboratory can be challenging, as it requires specific husbandry conditions that greatly differ from those ofmore common laboratory species such as mice or rats. Over the past 15 y, we have successfully established a long-term thrivingcolony of 150 to 200 animals originating from 36 founders. The colony shows longer life expectancy and larger litter sizesthan wild conspecifics. Breeding occurs year-round, independent of seasons, and a breeding pair can regularly produce 2 to 6offspring with an average life expectancy of more than 3 y. The shrews are housed in glass or plastic enclosures on a specificsoil-sand-mixture bedding and are provided with hideouts and nesting material consisting of moss, wood, or bark. Due to their high basal metabolic rate, the shrews require food intake greater than their body weight per day, can hunt arthropodsas large as themselves, and cannot survive more than a few hours without food. Live feed such as crickets or mealworms is crucial and must be provided daily or, at the very least, every 2 d. Although our husbandry practices have constantly been adapted and refined, shrew husbandry remains challenging, and great care is necessary to meet the specific needs of this species. Here, we describe the establishment of a long-term stable colony of Etruscan shrews in a research animal facility and the specific husbandry requirements for animal wellbeing.

BACKGROUND: Animal liver is established as an ex vivo model for studies on hepatic microwave ablation (MWA). Macroscopically visible color changes in the ablation zone are used to assess cell destruction and confirm successful ablation ex vivo. OBJECTIVE: Macroscopy and histology of MWA zones regarding cell viability in ex vivo porcine livers were compared in this study. METHODS: Six MWA were performed in porcine livers post mortem. A 14-G antenna and microwave generator (928 MHz; 9.0 kJ) were used. MWA were cut at the maximum cross section in vertical alignment to the antenna. NADH-diaphorase staining determined cell vitality. Macroscopic and microscopic ablation zones were statistically analyzed. RESULTS: Histology showed two distinct ablation zones: central white zone (WZH) with no cell viability and peripheral red zone (RZH) with partial cell viability. However, the macroscopically visible WZM was significantly smaller than the microscopic WZH with an area difference of 43.1% (p < 0.05) and a radius difference of 21.2% (1.6 mm; p < 0.05). Macroscopy and histology showed a very high correlation for the complete lesion area (WZH/M+RZH/M; r = 0.9; p = 0.001). CONCLUSIONS:The avital central zone is significantly larger as the macroscopically visible WZ which is commonly used to assess successful ablation in MWA ex vivo studies. Irreversible cell destruction can be underestimated in macroscopic evaluation.