BACKGROUND:Errors may occur during regional anaesthesia whilst searching for nerves, needle tips, and test doses. Poor visual search impacts on decision making, clinical intervention, and patient safety. METHODS:We conducted a randomised single-blind study in a single university hospital. Twenty trainees and two consultants examined the paired B-mode and fused B-mode and elastography video recordings of 24 interscalene and 24 femoral blocks conducted on two soft embalmed cadavers. Perineural injection was randomised equally to 0.25, 0.5, and 1.0 ml volumes. Tissue displacement perceived on both imaging modalities was defined as 'target' or 'distractor'. Our primary objective was to test the anaesthetists' perception of the number and proportion of targets and distractors on B-mode and fused elastography videos collected during femoral and sciatic nerve block on soft embalmed cadavers. Our secondary objectives were to determine the differences between novices and experts, and between test-dose volumes, and to measure the area and brightness of spread and strain patterns. RESULTS:All anaesthetists recognised perineural spread using 0.25 ml volumes. Distractor patterns were recognised in 133 (12%) of B-mode and in 403 (38%) of fused B-mode and elastography patterns; P<0.001. With elastography, novice recognition improved from 12 to 37% (P<0.001), and consultant recognition increased from 24 to 53%; P<0.001. Distractor recognition improved from 8 to 31% using 0.25 ml volumes (P<0.001), and from 15 to 45% using 1 ml volumes (P<0.001). CONCLUSIONS:Visual search improved with fusion elastography, increased volume, and consultants. A need exists to investigate image search strategies.

Breast cancer is the commonest cancer in women in the UK, accounting for 30% of all new cancers in women, with an estimated 49,500 new cases in 2010(1). With the widespread negative publicity around over-diagnosis and over-treatment of low risk breast cancers, interest in the application of non-invasive treatments such as magnetic resonance imaging (MRI) guided high intensity focused ultrasound (HIFU) has increased. Development has begun of novel US transducers and platforms specifically designed for use with breast lesions, so as to improve the range of breast lesions that can be safely treated. However, before such transducers can be evaluated in patients in clinical trials, there is a need to establish their efficacy. A particular issue is the accuracy of temperature monitoring of FUS with MRI in the breast, since the presence of large amounts of surrounding fat can hinder temperature measurement. An appropriate anatomical model that imposes similar physical constraints to the breast and that responds to FUS in the same way would be extremely advantageous. The aim of this feasibility study is to explore the use of Thiel embalmed cadaveric tissue for these purposes. We report here the early results of laboratory-based experiments sonicating dissected breast samples from a Thiel embalmed soft human cadaver with high body mass index (BMI). A specially developed MRI compatible chamber and sample holder was developed to secure the sample and ensure reproducible sonications at the transducer focus. The efficacy of sonication was first studied with chicken breast and porcine tissue. The experiments were then repeated with the dissected fatty breast tissue samples from the soft-embalmed human cadavers. The sonicated Thiel breast tissue was examined histopathologically, which confirmed the absence of any discrete lesion. To investigate further, fresh chicken breast tissue was embalmed and the embalmed tissue was sonicated with the same parameters. The results confirmed the inability to produce a discrete lesion in any of the Thiel embalmed samples.

Despite widespread use of ultrasound imaging to guide needle placement, the incidence of transient and permanent nerve damage as a complication of regional anaesthesia has not changed over the last decade. In view of the controversy surrounding intraneural injection there is a need to understand the structural changes caused by subepineural and subperineural needle penetration. Clinical ultrasound machines do not provide adequate anatomical resolution, and anaesthetists have difficulty judging the precise location of the needle tip relative to the epineurium. We studied the suitability of micro-ultrasound imaging (which offers anatomical resolution better than 100 μm) as a tool for viewing neural anatomy and deformation caused by needle insertion. The primary objective was to assess micro-ultrasound imaging as a method to view fascicles within nerves resected from fresh and soft-embalmed cadavers. Secondary objectives were to observe any disruption of the neural anatomy caused by anaesthetic needle penetration, and to assess the integrity of fresh and Thiel method soft-embalmed nerves, after handling and during needle insertion using ultrasound images and histology. We imaged nine nerves from the left and right sides of fresh and soft-embalmed cadavers. A regional block needle was inserted into three median nerves. We identified fascicles > 0.4 mm in width using micro-ultrasound. Subepineural needle placement was associated with denting, rotation and elastic deformation of fascicles, whereas subperineural needle insertion split fascicles permanently.

BACKGROUND We evaluated the physical properties and functional alignment of the soft-embalmed Thiel cadaver as follows: by assessing tissue visibility; by measuring its acoustic, mechanical and elastic properties; by evaluating its durability in response to repeated injection; and by aligning images with humans. METHODS In four soft-embalmed Thiel cadavers, we conducted three independent studies. We assessed the following factors: (i) soft tissue visibility in a single cadaver for 28 weeks after embalming; (ii) the displacement of tissues in response to 1 and 5 ml interscalene and femoral nerve blocks in a single cadaver; and (iii) the stiffness of nerves and perineural tissue in two cadavers. We aligned our findings with ultrasound images from three patients and one volunteer. Durability was qualified by assessing B-mode images from repetitive injections during supervised training. RESULTS There was no difference in visibility of nerves between 2 and 28 weeks after embalming {geometric mean ratio 1.13 [95% confidence interval (CI): 0.75-1.68], P=1.0}. Mean tissue displacement was similar for cadaver femoral and interscalene blocks [geometric mean ratio 1.02 (95% CI: 0.59-1.78), P=0.86], and for 1 and 5 ml injection volumes [geometric mean ratio 0.84 (95% CI: 0.70-1.01), P=0.19]. Cadavers had higher intraneural than extraneural stiffness [Young's modulus; geometric mean ratio 3.05 (95% CI: 2.98-3.12), P<0.001] and minimal distortion of anatomy when conducting 934 left-sided interscalene blocks on the same cadaver throughout a 10 day period. CONCLUSIONS The soft-embalmed Thiel cadaver is a highly durable simulator that has excellent physical and functional properties that allow repeated injection for intensive ultrasound-guided regional anaesthesia training.

BACKGROUND:The incidence of intraneural injection during trainee anaesthetist ultrasound guided nerve block varies between 16% in experts and up to 35% in trainees. We hypothesized that elastography, an ultrasound-based technology that presents colour images of tissue strain, had the potential to improve trainee diagnosis of intraneural injection during UGRA, when integrated with B-Mode ultrasound onto a single image.METHODS:We recorded 40 median nerve blocks randomly allocated to 0.25 ml, 0.5 ml, 1 ml volumes to five sites, on both arms of two soft embalmed cadavers, using a dedicated B-Mode ultrasound and elastography transducer. We wrote software to fuse elastogram and B-Mode videos, then asked 20 trainee anaesthetists whether injection was intraneural or extraneural when seeing B-Mode videos, adjacent B-Mode and elastogram videos, fusion elastography videos or repeated B-Mode ultrasound videos.RESULTS:Fusion elastography improved the diagnosis of intraneural injection compared with B-Mode ultrasound, Diagnostic Odds Ratio (DOR) (95%CI) 21.7 (14.5 - 33.3) vs DOR 7.4 (5.2 - 10.6), P < 0.001. Compared with extraneural injection, intraneural injection was identified on fusion elastography as a distinct, brighter translucent image, geometric ratio 0.33 (95%CI: 0.16 - 0.49) P < 0.001. Fusion elastography was associated with greater trainee diagnostic confidence, OR (95%CI) 1.89 (1.69 - 2.11), P < 0.001, and an improvement in reliability, Kappa 0.60 (0.55 - 0.66).CONCLUSIONS:Fusion elastography improved the accuracy, reliability and confidence of trainee anaesthetist diagnosis of intraneural injection.

Fixed and preserved tissues have been massively used in the development of biomedical equipment and instrumentation. Not only the tissue morphology, but also its mechanical properties need to be considered in the fixation and preservation procedures since mechanical properties have significant influence on the design and performance of such instruments. Understanding the effects of storage and preservation conditions on the mechanical properties of soft tissue has both clinical and experimental significance. To this end, we aimed to study the effects of tissue preservation (by 10% formalin and Thiel fluids) on the elastic properties of five different kinds of fresh tissues from pig and chicken; specifically fat, liver, muscle, tendon and cartilage. The tissue elasticity was measured intensively and strictly within a controlled timeline of 6 months by quantitative optical coherence elastography (OCE) system. Our findings suggest that the elasticity change of tissues in the formalin solution has an ascending trend, but that of Thiel remains almost constant, providing a more real texture and properties.

Introduction: Thiel soft-embalmed human cadavers are increasingly being used as a model to train surgeons and anesthetists because they look and feel like patients. However, there is a need to validate quantitatively the tissue properties of this model. Thus, the main objective of this study was to measure the elasticity of tissue in the Thiel soft-embalmed cadaver, using results in the literature for human volunteers for comparison. Materials and methods: Two independent ultrasound-trained operators measured the elasticity (Youngs modulus), E, of the thyroid, parotid and submandibular glands, the gastrocnemius and masseter muscles and the supraspinatus tendon in six Thiel soft-embalmed human cadavers using quantitative shear wave elastography. Each measurement was repeated 10 times. The elasticity values of Thiel soft-embalmed human cadavers were compared with human values reported in the literature. The relationship between elasticity and gender, age at death and number of days after embalming was also investigated. Results: Elasticity data for the cadavers displayed similar patterns as in the literature for human volunteers. The results show a positive correlation between Young's modulus (YM) and time after embalming, but no correlation with cadaver age at death or gender. Conclusions: The stiffness of the Thiel embalmed soft cadaver was validated against historical human data, confirming the life-like quality of the cadavers. Our results indicate that shear wave elastography is a promising tool to evaluate the stiffness of Thiel embalmed soft cadavers. (c) 2015 Elsevier GmbH. All rights reserved.

Poster: ECR 2015 / C-2618 / Human Thiel cadaveric flow model for training aortic endovascular interventional techniques by: H. M. McLeod, A. Melzer, J. Robertson, R. Eisma, B. F. Cox, G. Houston ; Dundee/UK

The use of endourology training models is on the rise. Surgical practice is moving toward a more minimally invasive approach and deficits in surgical exposure by enforcement of the European Working Time Directive call for simulation models to be anatomically sound. Thiel-embalmed cadavers have been found to demonstrate efficacy in tissue quality, elasticity, and handling in addition to playing a role in teaching and training. This review summarizes the current status of the Thiel method and its role in urologic skills training.

Thiel embalming is recommended as an alternative to formalin‐based embalming because it preserves tissue elasticity, color, and flexibility in the long term, with low infection and toxicity risk. The degree to which Thiel embalming preserves elasticity has so far been assessed mainly by subjective scoring, with little quantitative verification. The aim of this study is to quantify the effect of Thiel embalming on the elastic properties of human ankle tendons and ligament. Biomechanical tensile tests were carried out on six Thiel‐embalmed samples each of the peroneus longus, peroneus brevis, and calcaneal tendons, and the calcaneofibular ligament, with strain rates of 0.25%s−1, 2%s−1, and 8%s−1. The stress−strain relationship was calculated from the force‐extension response with cross‐sectional area and gauge length. Young's modulus was determined from the stress−strain curve. The results showed that the tendon and ligament elasticity were lower after Thiel embalming than the literature values for fresh nonembalmed tendons and ligament. The biomechanical tensile test showed that the measured elasticity of Thiel‐embalmed tendons and ligaments increased with the strain rate. The Thiel embalming method is useful for preserving human ankle tendons and ligaments for anatomy and surgery teaching and research, but users need to be aware of its softening effects. The method retains the mechanical strain rate effect on tendons and ligament. Clin. Anat. 28:917–924, 2015. © 2015 Wiley Periodicals, Inc.

Around 52,000 people are diagnosed with breast cancer each year in the UK. With the controversy around over diagnosis arising from the breast screening programme there is intense interest in the possibility of safe effective non-invasive treatment of cancers. As a non-invasive method of lumpectomy, focused ultrasound surgery (FUS) may offers reduced risk of infection, fewer complications and a shorter recovery time. It also allows more precise treatment as a result of real-time guidance by magnetic resonance (MR) or ultrasound. Even though specially designed FUS transducers for breast cancer treatment are now becoming available, transducer efficacy needs to be tested with a suitable preclinical model. A specific issue is the accuracy of temperature monitoring of FUS with MRI in the breast, since the presence of large amounts of surrounding fat can impair temperature measurement with the proton resonant frequency. An appropriate anatomical model that enforces comparable physical constraints to the breast and that responds to FUS in the same way would be extremely advantageous. The aim of this feasibility study is to explore the use of soft embalmed cadaveric breast tissue for these purposes. We report here the early results of MRI-guided FUS experiments sonicating dissected breast samples from a soft-embalmed human cadaver with a high body mass index (BMI).

Image-guided surgery is today considered to be of significant importance in neurosurgical applications. However, one of its major shortcomings is its reliance on preoperative image data, which does not account for brain deformations and displacements that occur during surgery. In this work, we propose to tackle this issue through the incorporation of an ultrasound device within the type of biopsy needles commonly used as an interventional tool to provide immediate feedback to neurosurgeons during surgical procedures. To identify the most appropriate path to access a targeted tissue site, single-element transducers that look either forward or sideways have been designed and fabricated. Micromolded 1-3 piezocomposites were adopted as the active materials for feasibility tests and epoxy lenses have been applied to focus the ultrasound beam. Electrical impedance analysis, pulse-echo testing, and wire phantom scanning have been carried out, demonstrating the functionality of the needle transducers at ~16 MHz. The capabilities of these transducers for intraoperative image guidance were demonstrated by imaging within soft-embalmed cadaveric human brain and fresh porcine brain.

The aim of this study was to compare Thiel-embalmed cadavers with formalin-embalmed cadavers and porcine models in the surgical simulation repair of a Zone II flexor tendon division. Nine participants were recruited to the study. The models were assessed using a five-point scale. Assessment was divided into tissue quality, surgical approach and identification of structures. Thiel cadavers rated consistently higher compared with the formalin and porcine models (mean 37 SD 2, 22 SD 6 and 23 SD 5, respectively). Thiel cadavers recorded an average tendon glide of 21 mm SD 5, formalin cadavers 2 mm SD 2 and the porcine model 6 mm SD 2. We have demonstrated the benefit of Thiel embalming, with flexibility of tissues allowing testing of the repair of a flexor tendon in a realistic anatomical model. Level of evidence: Level V.

Visibility of the needle tip and shaft is important during ultrasound-guided regional anaesthesia in order to prevent nerve trauma. Tip and shaft visibility is reduced when needles are inserted in-plane at wide angles and out-of-plane at narrow angles to the ultrasound probe. Although textured needles are more reflective than smooth needles, we hypothesised that poor visibility of the tip and shaft still remained using the above angle-probe combinations. In a single-blind study, we compared the visibility of a textured Tuohy needle, a textured single-shot needle and a conventional smooth-surfaced Tuohy needle when inserted into the biceps and deltoid muscles of a soft embalmed cadaver. One hundred and forty-four needles were block-randomised to in-plane and out-of-plane insertions at 30°, 45°, 60° and 75° to the ultrasound beam. Two blinded raters assessed needle tip visibility on video recordings of the insertions using a binary scale (0 = not visible, 1 = visible) and shaft visibility using a 5-point Likert scale. The median (IQR [range]) proportions of visible needle tips were 83% (67-83 [50-100]%) for the textured Tuohy, 75% (67-83 [33-83]%) for the textured single-shot needle and 33% (33-46 [0-50]%) for the smooth-surfaced Tuohy (p = 0.0007). Median (IQR [range]) needle shaft visibility was rated as 4.0 (3.5-4.7 [3.0-4.9]) for the textured Tuohy, 4.0 (3.8-4.5 [2.7-4.9]) for the textured single-shot needle and 3.0 (2.4-3.3 [2.3-3.5]) for the smooth-surfaced Tuohy (p = 0.015). Nevertheless, visibility was reduced at wide angles in-plane and narrow angles out-of-plane both for needle tips (p = 0.004) and shafts (p = 0.005).