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.

Benchmarking Deep Learning Models for Tooth Structure Segmentation.

A wide range of deep learning (DL) architectures with varying depths are available, with developers usually choosing one or a few of them for their specific task in a nonsystematic way. Benchmarking (i.e., the systematic comparison of state-of-the art architectures on a specific task) may provide guidance in the model development process and may allow developers to make better decisions. However, comprehensive benchmarking has not been performed in dentistry yet. We aimed to benchmark a range of architecture designs for 1 specific, exemplary case: tooth structure segmentation on dental bitewing radiographs. We built 72 models for tooth structure (enamel, dentin, pulp, fillings, crowns) segmentation by combining 6 different DL network architectures (U-Net, U-Net++, Feature Pyramid Networks, LinkNet, Pyramid Scene Parsing Network, Mask Attention Network) with 12 encoders from 3 different encoder families (ResNet, VGG, DenseNet) of varying depth (e.g., VGG13, VGG16, VGG19). On each model design, 3 initialization strategies (ImageNet, CheXpert, random initialization) were applied, resulting overall into 216 trained models, which were trained up to 200 epochs with the Adam optimizer (learning rate = 0.0001) and a batch size of 32. Our data set consisted of 1,625 human-annotated dental bitewing radiographs. We used a 5-fold cross-validation scheme and quantified model performances primarily by the F1-score. Initialization with ImageNet or CheXpert weights significantly outperformed random initialization (P < 0.05). Deeper and more complex models did not necessarily perform better than less complex alternatives. VGG-based models were more robust across model configurations, while more complex models (e.g., from the ResNet family) achieved peak performances. In conclusion, initializing models with pretrained weights may be recommended when training models for dental radiographic analysis. Less complex model architectures may be competitive alternatives if computational resources and training time are restricting factors. Models developed and found superior on nondental data sets may not show this behavior for dental domain-specific tasks.

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.

[Acute vestibular syndrome in emergency departments : Clinical differentiation of peripheral and central vestibulopathy]. / Akutes vestibuläres Syndrom in der Notaufnahme : Klinische Differenzierung von peripherer vs. zentraler Vestibulopathie.

INTRODUCTION: The differentiation between central and peripheral vestibular disorders is difficult in some cases, especially during the clinical routine of an emergency department (ED) without otoneurological diagnostic equipment. This study evaluated the frequency of vestibular pseudoneuritis as distinguished from acute peripheral vestibular disorders in patients who were admitted to hospital with the suspicion of vestibular neuropathy (VN). METHODS: This retrospective study analyzed the results of anamnestic and clinical examinations of 315 patients admitted to the emergency department and the inpatient otoneurological examination results as well as the imaging of morphological alterations. In the ED, the clinical examination by a neurologist and an otorhinolaryngologist resulted in the characteristic signs of peripheral VN but no further evidence of a neurological disorder. Patients without signs of a peripheral vestibular disorder in the otoneurological diagnostics subsequently underwent cerebral magnetic resonance imaging scans (cMRI). RESULTS: Suspected isolated VN could be confirmed in 69% of the patients; however, in a further 29% of the patients neither the suspected isolated VN nor an ischemic pathology of the central nervous system as a cause of the vertigo could be confirmed. Additional cMRI scans revealed that 2% of patients suffered from an infarction of the mesencephalon, the pons, the medulla oblongata and the cerebellum. CONCLUSION: In rare cases central cerebral disorders mimic the pattern of a peripheral vestibular disorder. Despite thorough history taking, neurological and otolaryngological clinical examinations, it is not always possible to distinguish central and peripheral vestibular disorders of patients in emergency care suffering from acute vertigo. Video oculography-assisted caloric testing and the video head impulse test are recommended to confirm a peripheral VN. In cases without confirmation of suspected NV in otoneurological diagnostics, infarction of the mesencephalon, brain stem and cerebellum should be excluded by diffusion-weighted cMRI.

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.

Tissue reaction induced by implanted venous access ports in adult patients after infection of the implantation site.

Implantable long-term central venous port systems (CVPS) are widely used as a permanent means of accessing the vascular system for intravenous delivery of drugs, parenteral nutrition, blood transfusion, and blood sampling. These systems allow easy and repetitive puncture without causing much damage to the vessels. However, the body foreign surface of CVPS induces an inflammatory response with varying intensity (depending on the implant materials) that leads to formation of a fibrous tissue capsule around the implant. This study was designed to investigate the influence of bacterial infection on the tissue reaction induced by implanted CVPS in adult patients. 20 patients (9 women, 11 men, 58 ± 14 yrs of age) were included in this study. These patients received explantation of a polysulfone based CVPS (ChemoSite™, Covidien, Mansfield, USA) due to port related infections (patients with bacterial infections at the implantation site: group A, 5 men, 1 women) or to other reasons such as termination of treatment, thrombosis, or CVPS dysfunction (patients without bacterial infections, group B, 6 men, 8 women) 299.9 ± 261.2 days after CVPS implantation. A sample of the encapsulating tissue covering the CVPS together with surrounding tissue (at least 1 × 1 cm2) was placed in a small container with fixing agent, a buffered neutral 4% formalin solution (pH 7). Histological sections of the samples were prepared for light microscopic analysis after paraffin embedding. Sections of 3 µm were cut and stained with haematoxylin and eosin, Weigert's elastic stain, and Heidenhain's azan stain. There was no difference in thickness, collagen and elastin content, or cell and capillary density of the fibrous capsule between both groups. Due to the wound healing reaction involving angiogenesis and fibroblast activation cell density and number of capillaries in the capsule tissue of all patients showed a positive correlation (r = 0.45, p < 0.05). However, the study demonstrated that at the end of the foreign body reaction the artificial tissue layer which covers the CVPS after implantation due to foreign body reaction shows only low reactivity towards infections.

The effect of prone versus supine positioning of Goettingen minipigs on lung density as viewed by computed tomography.

Minipigs are frequently used for scientific research as they are easy to handle and the dimensions of their vascular system do not change after 20 months of age. Although surgical interventions under anaesthesia are often performed in the supine position the effects of this positioning on lung functionality in minipigs have not been systematically described. This study aimed to analyse the influence of supine positioning on the macrostructure of the lung and the pulmonary density by the use of computed tomography imaging in pre-adult Göttingen minipigs. Twelve pre-adult female minipigs were used in the study and lung density was investigated in both the prone and the supine positions. The time between the scans in prone and supine positions was less than 5 minutes (296 ± 6 sec). In the prone position lung density did not differ between the dorsal and ventral part of the lung (-641 ± 72 Hounsfield units [HU]). However in the supine position there was a ventrodorsal gradient of decreasing density (ventral part of the lung: -497 ± 106 HU, dorsal part of the lung: -723 ± 51 HU). The changes in lung density were not accompanied by changes in lung volume (829 ± 191 ml). These results suggest an influence of the body position on the ventilation/perfusion (V(A)/Q) matching of the lung which could possibly result in lowered lung oxygenation as well as in an increased heart activity in the supine position. Additionally, due to the steep course of the vena cava caudalis from the caval foramen in the diaphragm across to the heart (in contrast to the more shallow course in the prone position) the activity of the heart necessary to pump the venous blood to the right atrium has to be higher in the supine position than in the prone position. In pigs the capacity of the heart to increase frequency is limited due to a diastolic/systolic (D/S) ratio <1. Supine positioning may possibly increase their risk of cardiovascular complications.

A NiTi alloy-based cuff for external banding valvuloplasty: a six-week follow-up study in pigs.

OBJECTIVE: The study aimed to test a Nitinol(®)-based vein cuff model for external banding valvuloplasty. METHOD: In 12 adult minipigs, the vena jugularis externa was covered for 42 days by a cuff with an inner diameter adapted to the outer vein diameter in supine position. By changing from supine into prone position hypostatically vein dilation was induced to simulate varicose vein dilation. Cuff position and the inner diameter of the vein lumen under the cuff were examined by computer tomography scanning. Also, histological analysis of the vein wall within the cuff was performed. RESULTS: The preset tubular shape of the cuff and the cuff position did not change in both prone and supine position, but due to fibrosis the luminal vein diameter within the cuff was decreased (P < 0.01) already after 21 days. CONCLUSION: A foreign body response resulted in a fibrous capsule covering the cuff which might limit cuff functionality.

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.

Low-dose computed tomography to detect body-packing in an animal model.

OBJECTIVE: To assess the possible extent of dose reduction for low-dose computed tomography (CT) in the detection of body-packing (ingested drug packets) as an alternative to plain radiographs in an animal model. MATERIALS AND METHODS: Twelve packets containing cocaine (purity >80%) were introduced into the intestine of an experimental animal (crossbred pig), which was then repeatedly examined by abdominal CT with stepwise dose reduction (tube voltage, 80 kV; tube current, 10-350 mA). Three blinded readers independently evaluated the CT datasets starting with the lowest tube current and noted the numbers of packets detected at the different tube currents used. In addition, 1 experienced reader determined the number of packets detectable on plain abdominal radiographs and ultrasound. RESULTS: The threshold for correct identification of all 12 drug packets was 100 mA for reader 1 and 125 mA for readers 2 and 3. Above these thresholds all 3 readers consistently identified all 12 packets. The effective dose of a low-dose CT scan with 125 mA (including scout view) was 1.0 mSv, which was below that of 2 conventional abdominal radiographs (1.2 mSv). The reader interpreting the conventional radiographs identified a total of 9 drug packets and detected 8 packets by abdominal ultrasound. CONCLUSIONS: Extensive dose reduction makes low-dose CT a valuable alternative imaging modality for the examination of suspected body-packers and might replace conventional abdominal radiographs as the first-line imaging modality.

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.

[Digital knowledge in the coat pocket -- hand-held personal digital assistants in radiology]. / Digitales Wissen in der Kitteltasche -- Taschencomputer (Handhelds) in der Radiologie.

The personal digital assistant (PDA) enables the independent access to large data in a pocket-sized format. The applications for hand-held computers are growing steadily and can support almost any kind of problem. An overview of the available hardware and software is provided and evaluated. Furthermore, the use of the PDA in the clinical daily routine is described. In view of the numerous software programs available in radiology, the range of software solutions for radiologists is presented. Despite the high acquisition cost, the PDA has already become the digital assistant for the radiologist. After a short time of getting used to the PDA, nobody wants to miss it at work or at home. New technical features and available software programs will continuously increase the integration of the PDA into the medical workflow in the near future.

[Clinical use of digital retrospective image fusion of CT, MRI, FDG-PET and SPECT -- fields of indications and results]. / Klinischer Einsatz der digitalen retrospektiven Bildfusion von CT, MRT, FDG-PET und SPECT -- Anwendungsgebiete und Ergebnisse.

PURPOSE: To evaluate the feasibility and the clinical benefits of retrospective digital image fusion (PET, SPECT, CT and MRI). MATERIALS AND METHODS: In a prospective study, a total of 273 image fusions were performed and evaluated. The underlying image acquisitions (CT, MRI, SPECT and PET) were performed in a way appropriate for the respective clinical question and anatomical region. Image fusion was executed with a software program developed during this study. The results of the image fusion procedure were evaluated in terms of technical feasibility, clinical objective, and therapeutic impact. RESULTS: The most frequent combinations of modalities were CT/PET (n = 156) and MRI/PET (n = 59), followed by MRI/SPECT (n = 28), CT/SPECT (n = 22) and CT/MRI (n = 8). The clinical questions included following regions (more than one region per case possible): neurocranium (n = 42), neck (n = 13), lung and mediastinum (n = 24), abdomen (n = 181), and pelvis (n = 65). In 92.6 % of all cases (n = 253), image fusion was technically successful. Image fusion was able to improve sensitivity and specificity of the single modality, or to add important diagnostic information. Image fusion was problematic in cases of different body positions between the two imaging modalities or different positions of mobile organs. In 37.9 % of the cases, image fusion added clinically relevant information compared to the single modality. CONCLUSION: For clinical questions concerning liver, pancreas, rectum, neck, or neurocranium, image fusion is a reliable method suitable for routine clinical application. Organ motion still limits its feasibility and routine use in other areas (e. g., thorax).