Three-dimensional assessment of vascular cooling effects on hepatic microwave ablation in a standardized ex vivo model.

The aim of this study was a three-dimensional analysis of vascular cooling effects on microwave ablation (MWA) in an ex vivo porcine model. A glass tube, placed in parallel to the microwave antenna at distances of 2.5, 5.0 and 10.0 mm (A-V distance), simulated a natural liver vessel. Seven flow rates (0, 1, 2, 5, 10, 100, 500 ml/min) were evaluated. Ablations were segmented into 2 mm slices for a 3D-reconstruction. A qualitative and quantitative analysis was performed. 126 experiments were carried out. Cooling effects occurred in all test series with flow rates ≥ 2 ml/min in the ablation periphery. These cooling effects had no impact on the total ablation volume (p > 0.05) but led to changes in ablation shape at A-V distances of 5.0 mm and 10.0 mm. Contrary, at a A-V distance of 2.5 mm only flow rates of ≥ 10 ml/min led to relevant cooling effects in the ablation centre. These cooling effects influenced the ablation shape, whereas the total ablation volume was reduced only at a maximal flow rate of 500 ml/min (p = 0.002). Relevant cooling effects exist in MWA. They mainly depend on the distance of the vessel to the ablation centre.

Perivascular vital cells in the ablation center after multibipolar radiofrequency ablation in an in vivo porcine model.

Multibipolar radiofrequency ablation (RFA) is an advanced ablation technique for early stage hepatocellular carcinoma and liver metastases. Vessel cooling in multibipolar RFA has not been systematically investigated. The objective of this study was to evaluate the presence of perivascular vital cells within the ablation zone after multibipolar RFA. Multibipolar RFA were performed in domestic pigs in vivo. Three internally cooled bipolar RFA applicators were used simultaneously. Three experimental settings were planned: (1) inter-applicator-distance: 15 mm; (2) inter-applicator-distance: 20 mm; (3) inter-applicator-distance: 20 mm with hepatic inflow occlusion (Pringle maneuver). A vitality staining was used to analyze liver cell vitality around all vessels in the ablation center with a diameter > 0.5 mm histologically. 771 vessels were identified. No vital tissue was seen around 423 out of 429 vessels (98.6%) situated within the central white zone. Vital cells could be observed around major hepatic vessels situated adjacent to the ablation center. Vessel diameter (> 3.0 mm; p < 0.05) and low vessel-to-ablation-center distance (< 0.2 mm; p < 0.05) were identified as risk factors for incomplete ablation adjacent to hepatic vessels. The vast majority of vessels, which were localized in the clinically relevant white zone, showed no vital perivascular cells, regardless of vessel diameter and vessel type. However, there was a risk of incomplete ablation around major hepatic vessels situated directly within the ablation center. A Pringle maneuver could avoid incomplete ablations.

Influence of interapplicator distance on multibipolar radiofrequency ablation during physiological and interrupted liver perfusion in an in vivo porcine model.

Radiofrequency ablation (RFA) is a curative treatment option for early stage hepatocellular carcinoma (HCC). Vascular inflow occlusion to the liver (Pringle manoeuvre) and multibipolar RFA (mbRFA) represent possibilities to generate large ablations. This study evaluated the impact of different interapplicator distances and a Pringle manoeuvre on ablation area and geometry of mbRFA. 24 mbRFA were planned in porcine livers in vivo. Test series with continuous blood flow had an interapplicator distance of 20 mm and 15 mm, respectively. For a Pringle manoeuvre, interapplicator distance was predefined at 20 mm. After liver dissection, ablation area and geometry were analysed macroscopically and histologically. Confluent and homogenous ablations could be achieved with a Pringle manoeuvre and an interapplicator distance of 15 mm with sustained hepatic blood flow. Ablation geometry was inhomogeneous with an applicator distance of 20 mm with physiological liver perfusion. A Pringle manoeuvre led to a fourfold increase in ablation area in comparison to sustained hepatic blood flow (p < 0.001). Interapplicator distance affects ablation geometry of mbRFA. Strict adherence to the planned applicator distance is advisable under continuous blood flow. The application of a Pringle manoeuvre should be considered when compliance with the interapplicator distance cannot be guaranteed.

Inter- and Intrareader Agreement of NI-RADS in the Interpretation of Surveillance Contrast-Enhanced CT after Treatment of Oral Cavity and Oropharyngeal Squamous Cell Carcinoma.

BACKGROUND AND PURPOSE: The Neck Imaging Reporting and Data System was introduced to assess the probability of recurrence in surveillance imaging after treatment of head and neck cancer. This study investigated inter- and intrareader agreement in interpreting contrast-enhanced CT after treatment of oral cavity and oropharyngeal squamous cell carcinoma. MATERIALS AND METHODS: This retrospective study analyzed CT datasets of 101 patients. Four radiologists provided the Neck Imaging Reporting and Data System reports for the primary site and neck (cervical lymph nodes). The Kendall's coefficient of concordance (W), Fleiss κ (κF), the Kendall's rank correlation coefficient (τB), and weighted κ statistics (κw) were calculated to assess inter- and intrareader agreement. RESULTS: Overall, interreader agreement was strong or moderate for both the primary site (W = 0.74, κF = 0.48) and the neck (W = 0.80, κF = 0.50), depending on the statistics applied. Interreader agreement was higher in patients with proved recurrence at the primary site (W = 0.96 versus 0.56, κF = 0.65 versus 0.30) or in the neck (W = 0.78 versus 0.56, κF = 0.41 versus 0.29). Intrareader agreement was moderate to strong or almost perfect at the primary site (range τB = 0.67-0.82, κw = 0.85-0.96) and strong or almost perfect in the neck (range τB = 0.76-0.86, κw = 0.89-0.95). CONCLUSIONS: The Neck Imaging Reporting and Data System used for surveillance contrast-enhanced CT after treatment of oral cavity and oropharyngeal squamous cell carcinoma provides acceptable score reproducibility with limitations in patients with posttherapeutic changes but no cancer recurrence.

Influence of pelvic volume on surgical outcome after low anterior resection for rectal cancer.

BACKGROUND: Low anterior resection (LAR) for rectal cancer is a potentially challenging operation due to limited space in the pelvis. CT pelvimetry allows to quantify pelvic space, so that its relationship with outcome after LAR may be assessed. Studies investigating this, however, yielded conflicting results. We hypothesized that a small pelvis is associated with a higher rate of incomplete mesorectal excision, anastomotic leakages, and increased rate of urinary dysfunction in patients operated for rectal cancer. METHODS: In a single-center retrospective analysis, we studied 74 patients that underwent LAR for rectal cancer with primary anastomosis. Thin-layered multi-slice CT datasets were used for slice by slice depiction of the inner pelvic surface, and the inner pelvic volume was automatically compounded. The primary outcome was quality of total mesorectal excision (TME; Mercury grading); secondary outcomes were anastomotic leakage and urinary dysfunction with regard to pelvic dimensions. Univariate analyses and multiple logistic regression analyses were performed for the primary and the secondary outcomes. RESULTS: Shorter obstetric conjugate diameters were associated with a higher probability of a worse TME quality (110.8 ± 10.2 vs. 105.0 ± 8.6 mm; OR 0.85; 95% CI 0.73-0.99; p = 0.038). Short interspinous distance showed a trend towards an increased risk for deteriorated TME quality (OR 0.88; 95% CI 0.76-1.0; p = 0.06). Anastomotic leakage was associated with anemia (OR 2.77; 95% CI 1.0-7.7; p = 0.047). Association between pelvic diameters or pelvic volume and anastomotic leakage or urinary dysfunction was not observed. Perioperative blood transfusions were administered more often in patients with postoperative urinary dysfunction (OR 17.67; 95% CI 2.44-127.7; p = 0.004). CONCLUSION: Shorter obstetric conjugate diameter might be a risk factor for incompleteness of total mesorectal excision. Anastomotic leakage seems to be influenced more by clinical factors such as anemia rather than pelvic dimensions. Further studies have to prove the influence of pelvic diameter on local recurrence of rectal cancer after LAR.

[Space-occupying lesion in the maxillary sinus]. / Eine Raumforderung im Sinus maxillaris.

During the preoperative diagnostics of an 80-year-old male patient prior to a planned endarterectomy, an unclear space-occupying lesion was detected in the right nasopharyngeal cavity. It proved to be a dense soft tissue space-occupying lesion of the right maxillary sinus. The histological investigations revealed a partially necrotically decomposed malignant tumor below normal respiratory mucosa free from dysplasia. This case demonstrates the difficulties in differential diagnostics, particularly involving (aberrant) expression of cytokeratin.

Pig specific vascular anatomy allows acute infrarenal aortic occlusion without hind limb ischemia and stepwise occlusion without clinical signs.

OBJECTIVE: In a porcine, aortic graft model we found 5 animals to develop and survive unnoticed, complete infrarenal aortic occlusion and 2 pigs with an acute occlusion but rather unspecific clinical symptoms. We investigated the pigs' vascular system to classify the anatomic capabilities to compensate for an acute abdominal aortic occlusion. DESIGN OF STUDY: Retrospective analysis of CT scans and clinical data to specify unexpected results in a case series of infrarenal occlusion in a porcine model. SETTING: Collaborative study of experimental and clinical departments. SUBJECTS: Fifteen healthy female minipigs. INTERVENTIONS: All pigs underwent an infrarenal aortic graft intervention. Anesthesia and perioperative management of the animals were preformed along the standard operating procedures of the local Department of Experimental Medicine. All animals received perioperative antibiotics, ASS, and carprofen for postoperative analgesia. Arterial pressure, heart rate, body temperature, and diuresis were monitored during surgery and therapeutic interventions. MAIN OUTCOME MEASURES: Contrast media based computed tomography (CT) with total body scans were performed at 1, 4, 10, 12 weeks after surgery. Comparable scans of cardiovascular healthy subjects (humans and pigs) and patients with a Leriche's syndrome were analyzed. RESULTS: Neither acute (within the first 12 h after surgery) nor stepwise total aortic occlusion show unmistakable clinical signs. In pigs, the epigastric artery (EGA) - which is in connection with suprarenal lumbal arteries, subclavian and external iliac artery - is highly developed associated to the high number of mammary glands of about 7 on one side. In humans, the ratio of aortic to EGA-diameter is 1 : 0.15. In minipigs we found a ratio of 1 : 0.43 which changed during aortic occlusion resulting in a ratio of 1 : 0.58. Pigs with a slowly developing occlusion demonstrated an enlargement of the ureteric artery of about 210% completing a sufficient collateral system. CONCLUSION: While in the human Leriche's syndrome months are needed to enlarge the EGAs for a partial collateral support of an infrarenal aortic occlusion the pig's EGA is a naturally sufficient collateral system capable to cover immediately for an acute infrarenal aortic occlusion. Further collateral enlargement even provides a permanent, sufficient hind limb perfusion in pigs. As the sufficient collateral system probably reduce pressure and shear rates in the infrarenal aortic segment after cross clamping, pigs might have a higher predisposition to produce early thrombosis related graft occlusions tan humans.

Ventral recumbency is crucial for fast and safe orotracheal intubation in laboratory swine.

The aim of this study was to find the fastest, easiest and safest method of achieving orotracheal intubation for general anaesthesia in laboratory pigs. Twenty-one Yorkshire x Landrace crossbreed male castrated pigs (32.9 +/- 4.8 kg) were investigated. Dorsal and ventral recumbency are the alternatives most frequently described for animal positioning during intubation procedures. Based on standardized induction of general anaesthesia using pentobarbital and remifentanil, the dorsoventral and ventrodorsal positions were compared with regard to the time needed, changes in oxygenation and circulatory response. Positioning was found to be crucial for fast orotracheal intubation. The time required for safe intubation is significantly shorter with the ventrodorsal position (17.3 s) in comparison with the dorsoventral position (58.4 s; P < 0.001). Hypoxia did not occur in either group. A significant drop in systolic blood pressure was observed in both groups. Diastolic and mean arterial pressures were not influenced by intubation. A significant increase in heart rate was observed in pigs intubated in ventral recumbency, but not after intubation in the dorsal position. Preoxygenation before intubation is vitally important for preventing hypoxia. With regard to clinical practice, the haemodynamic changes observed in this investigation do not appear to be relevant, as the mean arterial pressure was not altered and heart rates only increased moderately. It may be concluded that the ventrodorsal position can be recommended for orotracheal intubation in pigs as the first choice for providing a smooth and fast airway.

[Ultrasound contrast agents for liver diagnostics]. / Ultraschallkontrastmittel in der Leberdiagnostik.

Ultrasound contrast agents have achieved a high level of acceptance in diagnostics of liver tumors. Contrast-enhanced ultrasound can, on the one hand, be used for detection of liver tumors, e.g., during the search for metastases in tumor staging, and, on the other hand, for tumor characterization. The dispersion behavior of the ultrasound contrast agent plays a decisive role in the characterization and the enhancement patterns correspond to a large extent to those already known from contrast-enhanced computed tomography. Contrast-enhanced ultrasound can also be employed for monitoring ablative tumor therapies, visualization of vessels difficult to depict, and measurement of the so-called liver transit time.