Improved distinct bone segmentation in upper-body CT through multi-resolution networks.

PURPOSE: Automated distinct bone segmentation from CT scans is widely used in planning and navigation workflows. U-Net variants are known to provide excellent results in supervised semantic segmentation. However, in distinct bone segmentation from upper-body CTs a large field of view and a computationally taxing 3D architecture are required. This leads to low-resolution results lacking detail or localisation errors due to missing spatial context when using high-resolution inputs. METHODS: We propose to solve this problem by using end-to-end trainable segmentation networks that combine several 3D U-Nets working at different resolutions. Our approach, which extends and generalizes HookNet and MRN, captures spatial information at a lower resolution and skips the encoded information to the target network, which operates on smaller high-resolution inputs. We evaluated our proposed architecture against single-resolution networks and performed an ablation study on information concatenation and the number of context networks. RESULTS: Our proposed best network achieves a median DSC of 0.86 taken over all 125 segmented bone classes and reduces the confusion among similar-looking bones in different locations. These results outperform our previously published 3D U-Net baseline results on the task and distinct bone segmentation results reported by other groups. CONCLUSION: The presented multi-resolution 3D U-Nets address current shortcomings in bone segmentation from upper-body CT scans by allowing for capturing a larger field of view while avoiding the cubic growth of the input pixels and intermediate computations that quickly outgrow the computational capacities in 3D. The approach thus improves the accuracy and efficiency of distinct bone segmentation from upper-body CT.

Influence of size and shape of the auricular surfaces on subchondral bone density distribution in the sacroiliac joint.

The sacroiliac auricular surface has a variable morphology and size. The impact of such variations on subchondral mineralization distribution has not been investigated. Sixty-nine datasets were subjected to CT-osteoabsorptiometry for the qualitative visualization of chronic loading conditions of the subchondral bone plate using color-mapped densitograms based on Hounsfield Units in CT. Auricular surface morphologies were classified into three types based on posterior angle size: Type 1: >160°, Type 2: 130-160° and Type 3: <130°. Auricular surface size was categorized based on the mean value (15.4 cm2 ) separating the group into 'small' and 'large' joint surfaces. Subchondral bone density patterns were qualitatively classified into four color patterns: two marginal patterns (M1 and M2) and two non-marginal patterns (N1 and N2) and each iliac and sacral surface was subsequently categorized. 'Marginal' meant that 60-70% of the surface was less mineralized compared with the highly dense regions and vice versa for the 'non-marginal' patterns. M1 had anterior border mineralization and M2 had mineralization scattered around the borders. N1 had mineralization spread over the whole superior region, N2 had mineralization spread over the superior and anterior regions. Auricular surface area averaged 15.4 ± 3.6 cm2 , with a tendency for males to have larger joint surfaces. Type 2 was the most common (75%) and type 3 the least common morphology (9%). M1 was the most common pattern (62% of surfaces) by sex (males 60%, females 64%) with the anterior border as the densest region in all three morphologies. Sacra have a majority of surfaces with patterns from the marginal group (98%). Ilia have mineralization concentrated at the anterior border (patterns M1 and N2 combined: 83%). Load distribution differences related to auricular surface morphology seems to have little effect on long-term stress-related bone adaptation visualized with CT-osteoabsorptiometry. Higher iliac side mineralization was observed in larger joint surfaces and age-related morphomechanical size alterations were seen in males.

Auricular surface morphology and surface area does not influence subchondral bone density distribution in the dysfunctional sacroiliac joint.

The subchondral lamella of the sacroiliac auricular surface is morphologically inconsistent. Its morpho-mechanical relationship with dysfunction (SIJD) remains unstudied. Here, the iliac and sacral subchondral bone mineralization is compared between morphological subtypes and in large and small surfaces, in SIJD joints and controls. CT datasets from 29 patients with bilateral or unilateral SIJD were subjected to CT-osteoabsorptiometry. Surface areas and posterior angles were calculated and surfaces were classified by size: small (<15 cm3 ) and large (≥15 cm3 ), and morphological types: 1 (>160°), 2 (130°-160°), and 3 (<130°). Mineralization patterns were identified: two marginal (M1 and M2) and two non-marginal (N1 and N2). Each sacral and iliac surface was subsequently classified. Dysfunctional cohort area averaged 15.0 ± 2.4 cm2 (males 16.2 ± 2.5 cm2 , females 13.7 ± 1.6 cm2 ). No age correlations with surface area were found nor mean Hounsfield Unit differences when comparing sizes, sexes or morphology-type. Controls and dysfunctional cohort comparison revealed differences in female sacra (p = 0.02) and small sacra (p = 0.03). There was low-conformity in marginal and non-marginal patterns, 26% for contralateral non-dysfunctional joints, and 46% for dysfunctional joints. The majority of painful joints was of type 2 morphology (59%), equally distributed between small (49%) and large joints (51%). Larger joints had the highest frequency of dysfunctional joints (72%). Auricular surface morphology seems to have little impact on pain-related subchondral lamella adaptation in SIJD. Larger joints may be predisposed to the onset of pain due to the weakening of the extracapsular structures. Dysfunctional joints reflect common conformity patterns of sacral-apex mineralization with corresponding superior corner iliac mineralization.

Improved distinct bone segmentation from upper-body CT using binary-prediction-enhanced multi-class inference.

PURPOSE: Automated distinct bone segmentation has many applications in planning and navigation tasks. 3D U-Nets have previously been used to segment distinct bones in the upper body, but their performance is not yet optimal. Their most substantial source of error lies not in confusing one bone for another, but in confusing background with bone-tissue. METHODS: In this work, we propose binary-prediction-enhanced multi-class (BEM) inference, which takes into account an additional binary background/bone-tissue prediction, to improve the multi-class distinct bone segmentation. We evaluate the method using different ways of obtaining the binary prediction, contrasting a two-stage approach to four networks with two segmentation heads. We perform our experiments on two datasets: An in-house dataset comprising 16 upper-body CT scans with voxelwise labelling into 126 distinct classes, and a public dataset containing 50 synthetic CT scans, with 41 different classes. RESULTS: The most successful network with two segmentation heads achieves a class-median Dice coefficient of 0.85 on cross-validation with the upper-body CT dataset. These results outperform both our previously published 3D U-Net baseline with standard inference, and previously reported results from other groups. On the synthetic dataset, we also obtain improved results when using BEM-inference. CONCLUSION: Using a binary bone-tissue/background prediction as guidance during inference improves distinct bone segmentation from upper-body CT scans and from the synthetic dataset. The results are robust to multiple ways of obtaining the bone-tissue segmentation and hold for the two-stage approach as well as for networks with two segmentation heads.

The human masseter muscle revisited: First description of its coronoid part.

INTRODUCTION: The masseter muscle is considered to be bilayered, consisting of a superficial and a deep part. However, a few historical texts mention the possible existence of a third layer as well, but they are extremely inconsistent as to its position. Here we performed an anatomical study to clarify the presence and morphological characteristics of a distinct third layer of the masseter muscle. MATERIALS AND METHODS: We dissected 12 formaldehyde-fixed human cadaver heads, analysed CTs of 16 fresh cadavers, evaluated MR data from one living subject and examined histological sections using methyl methacrylate embedding of one formaldehyde-preserved head. RESULTS: An anatomically distinct, deep third layer of the masseter muscle was consistently demonstrated, running from the medial surface of the zygomatic process of the temporal bone to the root and posterior margin of the coronoid process. Ours is the first detailed description of this part of the masseter muscle. CONCLUSIONS: To facilitate discussion of this newly described part of the masseter, we recommend the name M. masseter pars coronoidea (coronoid part of the masseter) as a further reference. The arrangement of its muscle fibers suggest it being involved in stabilising the mandible by elevating and retracting the coronoid process.

Subchondral Bone Changes Following Sacroiliac Joint Arthrodesis - A Morpho-mechanical Assessment of Surgical Treatment of the Painful Joint.

BACKGROUND: Sacroiliac joint arthrodesis is an ultima ratio treatment option for sacroiliac joint dysfunction. Fusion drastically reduces sacroiliac joint movement providing long-lasting pain-relief associated with tension-relief to the innervated sacroiliac joint structures involved in force closure. OBJECTIVES: To display the bone mineralization distribution patterns of the subchondral bone plate in 3 distinct regions (superior, anterior, and inferior) of the sacral and iliac counterparts of the sacroiliac joint pre- and post-sacroiliac joint arthrodesis and compare patterns of sacroiliac joint dysfunction post-sacroiliac joint fusion with sacroiliac joint dysfunction pre- arthrodesis patterns and those from healthy controls. STUDY DESIGN: An observational study. SETTING: The research took place at the University of Basel, Switzerland, where the specific image analysis program (Analyze, v7.4, Biomedical Imaging Resources, Mayo Foundation, Rochester, NY, USA) was made available. METHODS: Mineralization densitograms of 18 sacroiliac joint dysfunction patients pre- and post-sacroiliac joint arthrodesis (>= 6, >= 12, and >= 24 months post-surgery) were obtained using computed tomography osteoabsorptiometry. For each patient, pre- vs. post-surgery statistical comparisons were undertaken, using the Hounsfield unit values derived from the subchondral mineralization of superior, anterior, and inferior regions on the iliac and sacral auricular surfaces. Post-operative values were also compared to those from a healthy control cohort (n = 39). RESULTS: In the pre-operative cohort at all 3 follow-up times, the superior iliac region showed significantly higher Hounsfield unit values than the corresponding sacral region (P < 0.01). Mineralization comparisons were similar for the sacrum and ilium in the anterior and inferior regions at all follow-up points (P > 0.5) with no surgery-related changes. Sacral density increased significantly in the post-operative state; not observed on the ilium. Post-operative sacroiliac joints showed a significantly increased mineralization in the superior sacrum after >= 6 months (P < 0.05), not replicated after >= 12 nor >= 24 months. Further comparison of post-operative scans versus healthy controls revealed significantly increased mineralization in the superior sacral region at (>=) 6, 12, and 24 months (P < 0.01), likely related to bone grafting, and in the anterior and inferior regions in post-operative scans at >= 12 and >= 24 months follow-up (P < 0.05). LIMITATIONS: The given study is limited in sample size. Post-operative computed tomography scans had screws which may have left artifacts or partial volume effects on the surfaces. Healthy controls were different patients to the sacroiliac joint dysfunction and post-operative cohorts. Both cohorts were age-matched but this comparison did not take into account potential population differences. Size differences in the regions may have also been an influencing factor of the results as the regions were based on the size and shape of the articular surface. CONCLUSIONS: Sacroiliac joint arthrodesis results in an increased morpho-mechanical conformity in the anterior and inferior sacrum and reflects variable morpho-mechanical density patterns compared to the healthy state due to permanent alterations in the kinematics of the posterior pelvis.

Subchondral bone strength of the sacroiliac joint-a combined approach using computed tomography osteoabsorptiometry (CT-OAM) imaging and biomechanical validation.

Bone mineral density distribution patterns at the sacroiliac joint (SIJ) may reflect long-term adaptation patterns to the loading the joint endures. This study aims to display bone mineralisation patterns of the articular SIJ subchondral lamella using computed tomography (CT) osteoabsorptiometry and mechanical indenting, to determine whether a relationship exists between mineralisation and mechanical strength. Twenty hemipelves were CT-scanned before osteoabsorptiometry densitograms were derived. Each articular side of eleven SIJs was mechanically indented following a 10-mm grid scheme. The sacral surface displayed lower Hounsfield unit (HU) values (≤ 700 HU) than the iliac side (> 700 HU). The apex, superior corner and borders yielded the highest HU scores (> 700 HU). Penetration strength was significantly higher on the iliac side (p < 0.04). Mineral density correlated positively with penetration strength of the subchondral bone layer (p < 0.05). No correlations were found between the HU values, nor between penetration strength of corresponding sides of the same SIJ in the majority of cases (p > 0.05). The iliac subchondral lamella is mechanically denser than the sacral aspect. The non-correlation between density and bone strength of articulating sides indicates biomechanical non-conformity. Loading throughout the SIJ may follow a complex distribution pattern involving the surrounding soft tissues, suspending the sacrum between the ilia.

Minimally invasive ultrasound-guided parotid gland biopsy in cadavers performed by rheumatologists.

Introduction: Surgical biopsy of minor salivary glands is routinely performed for the diagnosis of Sjögren syndrome. However, surgical biopsies of the minor labial glands may result in various complications in up to 6% of patients. On the other hand, adverse events following core needle biopsies of the parotid gland in non-rheumatological settings have been reported as very rare. Aim: The objective of this study was to assess the feasibility and determine the presence of parotid gland tissue in ultrasound-guided parotid gland biopsies performed by rheumatologists in cadavers. Material and method: Two senior rheumatologists obtained, under direct ultrasound visualization in in-plane technique, biopsies of 8 parotid glands from 4 different cadavers using a core biopsy needle. One biopsy per gland was taken. Results: All histological exams showed typical parotid gland tissue without any neuronal or vascular tissue. Conclusion: In conclusion, we demonstrated that minimally invasive, ultrasound-guided core needle biopsy of the parotid gland is a highly precise and easy method to obtain salivary gland tissue.Introduction: Surgical biopsy of minor salivary glands is routinely performed for the diagnosis of Sjögren syndrome. However, surgical biopsies of the minor labial glands may result in various complications in up to 6% of patients. On the other hand, adverse events following core needle biopsies of the parotid gland in non-rheumatological settings have been reported as very rare. Aim: The objective of this study was to assess the feasibility and determine the presence of parotid gland tissue in ultrasound-guided parotid gland biopsies performed by rheumatologists in cadavers. Material and method: Two senior rheumatologists obtained, under direct ultrasound visualization in in-plane technique, biopsies of 8 parotid glands from 4 different cadavers using a core biopsy needle. One biopsy per gland was taken. Results: All histological exams showed typical parotid gland tissue without any neuronal or vascular tissue. Conclusion: In conclusion, we demonstrated that minimally invasive, ultrasound-guided core needle biopsy of the parotid gland is a highly precise and easy method to obtain salivary gland tissue.

The adaption of the bony microstructure of the human glenoid cavity as a result of long-term biomechanical loading.

Structural arrangements of the bony microstructure of a joint through adaptational processes are thought to be determined by the biomechanical demands and its changes. Pursuing this theory of "form follows the biomechanical function", the load distribution of the glenoid cavity, as it is mirrored in its mineralization pattern, should link not only to its thickness distribution, but also will have an impact onto the trabecular network below. To prove and confirm this hypothesis, we analysed the mineral distribution in correlation to the subchondral bone plates thickness and the distribution of architectural parameters of the trabecular network below. Our findings clearly state an inhomogeneous but regular and reproducible mineral distribution pattern in respect to the biomechanical demands and a thickness of the subchondral bone plate which shows a significant correlation (78-93%). As for the trabecular network below, the distribution of the analysed parameters also revealed an inhomogeneous distribution with a regular pattern in correlation to the biomechanical impact. We found distinctive maxima of material distribution and stability (bone volume 79%, plate-like architecture 77%) situated below areas of high long-term load intake. With increasing depth, the trabecular network administers the expression of each structural parameter following the fact that the strain energy gets more and more evenly distributed and changes from a high degree of differentiation just beneath the SBP to a more equal distribution within the deeper areas. After all, the biomechanical situation of a joint directly influences the bony formation of the subchondral bone plate and the trabecular network below.

Osteoarthritis alters the patellar bones subchondral trabecular architecture.

Following the principles of "morphology reveals biomechanics," the cartilage-osseous interface and the trabecular network show defined adaptation in response to physiological loading. In the case of a compromised relationship, the ability to support the load diminishes and the onset of osteoarthritis (OA) may arise. To describe and quantify the changes within the subchondral bone plate (SBP) and trabecular architecture, 10 human OA patellae were investigated by CT and micro-CT. The results are presented in comparison to a previously published dataset of 10 non-OA patellae which were evaluated in the same manner. The analyzed OA samples showed no distinctive mineralization pattern in regards to the physiological biomechanics, but a highly irregular disseminated distribution. In addition, no regularity in bone distribution and architecture across the trabecular network was found. We observed a decrease of material as the bone volume and trabecular thickness/number were significantly reduced. In comparison to non-OA samples, greatest differences for all parameters were found within the first mm of trabecular bone. The differences decreased toward the fifth mm in a logarithmic manner. The interpretation of the logarithmic relation leads to the conclusion that the main impact of OA on bony structures is located beneath the SBP and lessens with depth. In addition to the clear difference in material with approximately 12% less bone volume in the first mm in OA patellae, the architectural arrangement is more rod-like and isotropic, accounting for an architectural decrease in stability and support. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:1982-1989, 2017.

Functional and Structural Details about the Fabella: What the Important Stabilizer Looks Like in the Central European Population.

The posterolateral corner of the knee accommodating the fabella complex is of importance in orthopaedic surgery. Unfortunately, there is a lack of data in literature for clinical routine. Therefore, we investigated the fabella's characteristics, biomechanical nature, and present histologic details. Of special interest were the fabella's occurrence and position, calcium concentration as long-term load intake indicator, and the histology. Within our analysis, fabellae were found in 30.0% of all datasets, located on the upper part of the posterolateral femoral condyle. The region of fabella contact on this condyle showed a significantly lower calcium concentration than its surroundings. Histologically, the fabella showed no articular cartilage but a clearly distinguishable fabellofibular ligament that consisted of two bundles: one, as already described in literature inserted at the fibular tip, and another part newly described on the top of the lateral meniscus. In its role of stabilizing the soft tissue structures of the posterolateral knee, the fabella seems to serve as suspension for the ligaments evolving from its base. Even though a joint formation of any kind is unlikely, the presence of a fabella needs to be kept in mind during knee examination and any surgical procedures.

Ultrathin-layer sodium dodecyl sulfate disc electrophoresis of proteins in the range from 10 to 220 kDa in homogeneous, low-concentrated polyacrylamide gels.

This study describes an ultrathin-layer sodium dodecyl sulfate (SDS) disc electrophoresis in polyacrylamide gels of a thickness of only 150 microm. By use of 2-amino-2-methyl-1,3-propanediol/glycine instead of traditional Tris/HCl buffer in the resolving phase of the gel, proteins with a wide range of molecular sizes (10 kDa to over 220 kDa) are separated in unusually low-concentrated gels (4%T, 3.3%C). 2-Amino-2-methyl-1,3-propanediol in the resolving part of the gel contributes to stabilization of the pH value at 8.8, while glycine improves destacking as well as separation of small proteins from the bulk of stacked SDS. This method combines both the advantages of conventional slab-gel electrophoresis and capillary gel electrophoresis. It is easy to apply and well suited for all further miniaturization attempts.

The so-called "testis-specific aldehyde dehydrogenase" corresponds to type 2 retinaldehyde dehydrogenase in the mouse.

The distribution pattern of "testis-specific aldehyde dehydrogenase" in mouse tissues was investigated. Because of the broad substrate specificity and the high degree of sequence identity of the large aldehyde dehydrogenase family a specific detection of single isoforms is not possible by histochemical means. Therefore, the technique of native isoelectric focusing was used. Thus, the expression of four to five banded "testis-specific aldehyde dehydrogenase" in the mouse testis was confirmed. However, the activity of this enzyme with the same pattern of multiplicity was found not only in the testis but also in the uterus and in embryonic tissues. At 9.5 and 10.5 days of embryonic development the enzyme activity was restricted to tissues of the embryonic trunk and absent in extracts from cranial tissues. The tissue distribution as well as substrate specificity and isoelectric points indicate that the "testis-specific aldehyde dehydrogenase" corresponds to mouse type 2 retinaldehyde dehydrogenase.