Comparison of in vivo vs. frozen vs. Thiel cadaver specimens in visualisation of anatomical structures of the ankle on proton density Magnetic Resonance Imaging (MRI) through a visual grading analysis (VGA) study

The magnetization transfer ratio of the post-mortem canine intervertebral disk is positively correlated to Pfirrmann grading on high field 3.0T MRI: a pilot study

Objective

Intervertebral disk (IVD) degeneration usually occurs earlier in chondrodystrophic dog breeds than in other breeds. Spinal cord compression secondary to IVD degeneration is the most common cause of myelopathy in these dogs. Standard magnetic resonance imaging (MRI) sequences permit the identification of IVD degeneration and its consequences on adjacent neurological structures. In human medicine, quantitative MRI sequences, such as magnetization transfer ratio (MTR) sequences, are developed and used to detect early IVD degeneration. This prospective randomized post-mortem comparative study aimed to evaluate the correlation between a qualitative Pfirrmann MRI grading and the MTR values of the IVD in chondrodystrophic dogs.

Materials and methods

Vertebral columns of eight canine cadavers were frozen and thawed prior to imaging with T2-weighted and MTR sequences using a 3.0 T high-field MRI. These sequences were reviewed by two observers. A Spearman correlation coefficient was calculated in order to compare the MTR values with the Pfirrmann grade. Pearson correlation coefficients were calculated to evaluate the inter-observer agreement of the delineation of the region of interest (ROI) around the NP and the MTR values. A Wilcoxon-Mann-Whitney test was used to conclude on the significance of the correlation between the MTR values and the Pfirrmann grades.

Results

There were 138 intervertebral disks analyzed: 29/138 (21.0%) IVD were grade I, 74/138 (53.6%) grade II, and 35/138 (25.4%) grade III. No grades IV and V were present in this study. Inter-observer agreement for delineation of IVD ROI was fair (r = 0.54) but inter-observer agreement of mean MTR value within the ROI was very good (r = 0.89). Mean MTR values were 16.459% (10.0305-21.0950%) for grade I, 18.888% (10.0750-27.2400%) for grade II, and 22.813% (12.5700-31.7600%) for grade III. The mean MTR value was significantly different between each Pfirrmann grade: between grades I and II (p < 0.005), grades II and III (p < 0.05), and grades I and III (p < 0.005). There was a significant moderate positive correlation between Pfirrmann grading and mean MTR values (r = 0.516).

Conclusion

The magnetization transfer ratio seems to be an objective method to detect early intervertebral disk degeneration via quantitative analysis.

The advantages of utilizing different ultrasound imaging techniques on joints of human cadavers in the teaching of anatomy - A scoping review

BACKGROUND

A common approach to define sonoanatomy is a reciprocal exchange of macroscopic and microscopic information in ultrasound imaging. High-resolution ultrasound has been long established and is crucial as an inexpensive and adaptable tool, not just in clinical settings but also while teaching anatomy. Early application of ultrasonography provides medical students with a couple of benefits: they acquire an improved understanding of anatomy and learn how to use it.

METHODS

A comprehensive literature review has been carried out, with relevant studies discovered in the following databases: MEDLINE, EMBASE, CENTRAL, BIOSIS Previews and Web of Science Core Collection. Gray literature was also considered in two different ways: (1) Regarding grey literature databases: National Gray Literature Collection. (2) For PhD theses and dissertations, the databases EThOS and Open Access Theses and Dissertations were screened for relevant studies by combining the keywords used in the search string. The reference lists of all relevant papers were scanned. Search process was performed on January 3rd, 2023. The search string was developed with the aid of and finally checked by a professional librarian. Only ultrasound studies on human cadavers were included, not animals or phantoms. If the studied subject was a joint, the article was included. Only B-Mode ultrasound was included, whereas Elastosonography, Doppler sonography and quantitative approaches including among others sound speed, backscatter attenuation were excluded. Intravascular, intraosseous, intraarticular, and three-dimensional or four-dimensional ultrasonography were also eliminated from the analysis. All appropriate information comprising articles, PhD theses, dissertations and chapters in textbooks were considered. There were solely English and German studies covered. There was no additional restriction on the publishing year. The included studies' general characteristics and ultrasound techniques were taken from them and examined. Using VOS viewer, a keyword analysis was also carried out.

RESULTS

142 of the 8899 results that were returned by the search satisfied the requirements. With a quarter of the included studies, the knee joint was the most extensively studied joint, followed by the elbow joint (10.6%) and the shoulder joint (9.2%). The methodological analysis includes 125 studies. Both the sample size and the ultrasonographer's qualifications were diverse. The probe position and the ultrasound method were precisely documented so that a reader could duplicate them in about three-quarters of the included studies (72.8%).

CONCLUSION

The current study, in our perspective, is the first scoping review to screen ultrasound studies on human cadaver joints. A heterogeneous field was shown by the methodological investigation. We suggest using a uniform method for conducting and presenting ultrasound examinations in future studies.

Comparison between pre-mortem and post-mortem cadaveric images for use with augmented reality headsets during dissection

PURPOSE

Medical training has undergone many transformations to incorporate diagnostic imaging along side anatomical education. Post-mortem computed tomography (CT) scanning of body donors prior to dissection has been proposed. However, it poses challenges secondary to the embalming process and other post-mortem physiological changes that significantly alter the imaging quality. The purposes of this study were to compare the accuracy of pathology identification on pre- and post-mortem CT scans of body donors and to assess the integration of those scans in a dissection-based course, where these images were overlaid onto body donors using augmented reality (AR).

METHODS

Participants in this study included 35 fourth year medical students, 5 radiology residents and 3 radiologists. A convergent, parallel mixed methods design was employed with quantitative measures that included statistical analyses of a double-blinded comparison of pathological lesions recognition, on both image sets, the group responses to a study participant survey and the login access data from imaging repository. The study also included qualitative analysis of post-elective structured interviews.

RESULTS

The double-blinded comparison revealed that staff radiologists can only identify, on post-mortem images, 54.8% of the pathologies that they were able to detect on the pre-mortem scans. Analyses of the surveys and login access data reveal that 60% of radiology residents and 56% of students preferred pre-mortem scans and used those scans more often than post-mortem scans (67 access vs 36, respectively). However, post-mortem scans were significantly preferred when used to overlay onto body donors using AR (p = 0.0047).

CONCLUSION

These results show that post-mortem imaging can be valuable alongside pre-mortem imaging, as they represent the most concordance between the anatomical structures and pathologies seen on the images and what is being dissected.

Current and potential use of fresh frozen cadaver in surgical training and anatomical education

As surgical procedures continue to be more complex, the need for more effective training in anatomy has increased. The study of anatomy plays a significant role in the understanding of the human body as well as in basic and advanced clinical training. Among the different cadaver models, fresh frozen cadavers (FFCs) are known for their realistic tissue quality. The purpose of this article was to review and summarize the preparation procedures for and reported cases involving FFCs. PubMed, Scopus, Medline, and Web of Science were searched for relevant studies. The preparation procedures were divided into five steps: washing, irrigation, freezing, defrosting, and arterial infusion. Not all steps were reported to be mandatory, but omitting one or more could result in a loss of quality. FFCs were reported to be used for various purposes: undergraduate education, general surgery training, vascular surgery training, minimal access surgery (laparoscopic surgery) training, and microsurgery training. In all categories, expert opinions and statistical analyses indicated successful outcomes. The reasons for high satisfaction with FFCs included realistic texture, capability of reenacting actual operations, and accuracy of anatomical locations. The results also revealed the importance and advantages of the dissection courses in surgical training. Since the direct comparison between cadaver models is insufficient, future studies regarding this topic are deemed necessary. In addition, it would be advantageous to develop methods to improve FFC quality, or ideas to optimize this model for certain purposes.

A Review and Case Study of 3D Imaging Modalities for Female Amniote Reproductive Anatomy

Recent advances in non-invasive imaging methods have revitalised the field of comparative anatomy, and reproductive anatomy has been no exception. The reproductive systems of female amniotes present specific challenges, namely their often internal "hidden" anatomy. Quantifying female reproductive systems is crucial to recognising reproductive pathologies, monitoring menstrual cycles, and understanding copulatory mechanics. Here we conduct a review of the application of non-invasive imaging techniques to female amniote reproductive anatomy. We introduce the commonly used imaging modalities of computed tomography (CT) and magnetic resonance imaging (MRI), highlighting their advantages and limitations when applied to female reproductive tissues, and make suggestions for future advances. We also include a case study of micro CT and MRI, along with their associated staining protocols, applied to cadavers of female adult stoats (Mustela erminea). In doing so, we will progress the discussion surrounding the imaging of female reproductive anatomy, whilst also impacting the fields of sexual selection research and comparative anatomy more broadly.

Anatomical position of the palmar/plantar nerves at the metacarpal/metatarsal distal level in horses: An in vivo study by means of ultrasonography

The neurovascular bundle of the equine distal cannon can dynamically vary with limb position, and this can affect the performance of low 4- or 6-point block. This study aims to identify and describe the anatomical position and variations of the lateral and medial palmar/plantar nerve at the metacarpal/metatarsal distal level in horses by ultrasonography. Eight mares underwent ultrasound examination on the lateral and medial palmar/plantar sides of the metacarpus/metatarsus. Images were obtained for measurements of the cross-sectional area of the nerve, distances between the nerve and the skin surface, branch of the suspensory ligament (SL), deep digital flexor tendon (DDFT) and superficial digital flexor tendon (SDFT) with limbs supported and elevated. The distance to the skin for forelimbs was higher on the lateral side when the limb was elevated (p < 0.001). The comparisons between supported and elevated limbs on the same side showed longer distances to the skin with the limb supported on the medial side (p < 0.001). Hindlimbs showed longer distances to the skin with the limb supported on the medial face (p = 0.027). The anatomical position of palmar/plantar nerves was similar between the lateral and medial sides of the limb, generally being in contact with the dorsal edge of DDFT. The strategy of elevating the limb during the injection of the low 4- or 6-point block can lead to a higher risk of puncture of the digital sheath.

VIEWDEX 3.0-RECENT DEVELOPMENT OF A SOFTWARE APPLICATION FACILITATING ASSESSMENT OF IMAGE QUALITY AND OBSERVER PERFORMANCE

ViewDEX (Viewer for Digital Evaluation of X-ray Images) is an image viewer compatible with Digital Imaging and Communications in Medicine (DICOM) that has been especially designed to facilitate image perception and observer performance studies within medical imaging. The software was first released in 2004 and since then a continuous development has been ongoing. One of the major drawbacks of previous versions of ViewDEX has been that they have lacked functionality enabling the possibility to evaluate multiple images and/or image stacks simultaneously. This functionality is especially requested by researchers working with modalities, where an image acquisition can result in multiple image stacks (e.g. axial, coronal and sagittal reformations in computed tomography). In ViewDEX 3.0 this functionality has been added and it is now possible to perform image evaluations of multiple images and/or image stacks simultaneously, by using multiple monitors and/or multiple image canvases in monitors. Additionally, some of the previously available functionality has been updated and improved. This paper describes the recent developments of ViewDEX 3.0.

The Thiel cadaveric model for pelvic floor surgery: Best rated in transferable simulation-based training for postgraduate studies

OBJECTIVE

To determine whether the Thiel cadaveric model is better and more realistic than other surgical simulation techniques for learning pelvic floor and perineal surgical procedures according to the opinions of urogynecologists and surgeons participating in international postgraduate pelvic floor surgery courses using cadavers embalmed by the Thiel method.

STUDY DESIGN

An observational prospective study was performed in urogynecologists and surgeons attending international postgraduate pelvic floor and perineal surgery courses using cadavers embalmed by the Thiel method. A survey was completed by the participants after finishing the course. Based on the answers collected, we analyzed the differences, including in the satisfaction degree and teaching level for each surgical procedure, between different surgical simulation models that the participants had already used and the Thiel simulation method employed.

RESULTS

The students recognized that Thiel cadavers present more similarities to patients than other simulation methods. The Thiel cadaveric method was considered by most responders to be the best for the simulation of surgical procedures on the pelvic floor and perineum. Most of the surgeons surveyed recommended conducting these courses with Thiel cadavers for different colleagues in other specialties as a reliable simulation method for training for difficult surgical procedures.

CONCLUSIONS

Participants in the course on pelvic floor surgery in Thiel cadavers recognized that this is the most realistic model for surgical simulation and the best way to gain confidence, self-determination and precise surgical skills for performing pelvic floor and perineal surgery.

A noninvasive MRI based approach to estimate the mechanical properties of human knee ligaments

Characterization of the main tibiofemoral ligaments is an essential step in developing patient-specific computational models of the knee joint for personalized surgery pre-planning. Tensile tests are commonly performed in-vitro to characterize the mechanical stiffness and rupture force of the knee ligaments which makes the technique unsuitable for in-vivo application. The time required for the limited noninvasive approaches for properties estimation based on knee laxity remained the main obstacle in clinical implementation. Magnetic resonance imaging (MRI) technique can be a platform to noninvasively assess the knee ligaments. In this study the aim was to explore the potential role of quantitative MRI and dimensional properties, in characterizing the mechanical properties of the main tibiofemoral ligaments. After MR scanning of six cadaveric legs, all 24 main tibiofemoral bone-ligaments-bone specimens were tested in vitro. During the tensile test cross sectional area of the specimens was captured using ultrasound and force-displacement curve was extracted. Digital image correlation technique was implemented to check the strain behavior of the specimen and rupture region and to assure the fixation of ligament bony block during the test. The volume of the specimen was measured using manual segmentation data, and quantitative MR parameters as T₂^*, T_1ρ, and T₂ were calculated. Linear mixed statistical models for repeated measures were used to examine the association of MRI parameters and dimensional measurements with the mechanical properties (stiffness and rupture force). The results shows that while the mechanical properties were mostly correlated to the volume, inclusion of the MR parameters increased the correlation strength for stiffness (R² ≈ 0.48) and partial rupture force (R² = 0.53). Inclusion of ligament type in the statistical analysis enhanced the correlation of mechanical properties with MR parameters and volume as for stiffness (R² = 0.60) and partial rupture (R² = 0.57). In conclusion, this study revealed the potentials in using quantitative MR parameters, T_1ρ, T₂ and T₂^*, combined with specimen volume to estimate the essential mechanical properties of all main tibiofemoral ligaments required for subject-specific computational modeling of human knee joint.