Midsagittal Research Articles

Risk factors for progression of nucleus pulposus degeneration in the lumbar intervertebral disc: A retrospective analysis using the disc signal intensity index.

Degenerative disc changes are associated with low back pain and negatively impact quality of life. Disc degeneration process usually starts with nucleus pulposus change. There is uncertainty about the risk factors associated with the progression of disc nucleus degeneration due to the lack of an objective evaluation method. Pfirrmann grade, which assesses the morphological characteristics of a disc on T2-weighted MRI images on a scale of 1 to 5, is one of the most frequently used assessment systems. This method inherently has a degree of subjectivity that may lead to inaccurate and inconsistent grading. A recent study introduced the disc signal intensity index (DSI2) for quantitative assessment of nucleus pulposus degeneration with promising results in identifying of risk factors for progression of disc degeneration. The aim of this study was to investigate the risk factors for the progression of nucleus pulpous degeneration in the lumbar vertebral disc on longitudinal MRI data using DSI2. Retrospective longitudinal study PATIENT SAMPLE: Patients with lumbar MRIs at least three years apart and did not undergo the lumbar spine surgery between both time points were included. Potential contributing factors were collected that included age, biological sex, race, body mass index (BMI), current smoking status, alcohol consumption, history of previous lumbar decompression surgery, and comorbidities such as congestive heart failure (CHF), myocardial infarction, diabetes mellitus, chronic obstructive pulmonary disease, hypertension, and rheumatoid arthritis. Disc nucleus degeneration was assessed using the DSI2 and Pfirrmann grade on T2- weighted MRI. The DSI2 values are based on the mean signal of disc spaces within a circular region of interest (ROI), which was adjusted by the signal intensity of cerebrospinal fluid (CSF) on the midsagittal plane. Three ROIs were set per disc (anterior 1/3, middle, posterior 1/3), and the mean values of all three measurements from L1/2 to L5/S1 disc space were utilized. Discs with complete collapse and no space for ROI selection were excluded. The difference in DSI2 scores between these two time points were compared. Multivariate linear mixed regression analysis was conducted to determine the factors associated with disc degenerative changes. A total of 325 patients and 1439 discs were included in the final analysis. 173 patients (53.2%) were female and the median age of all patients was 60.1 years. The mean (SD) DSI2 score was 0.177 (0.074) for thefirst MRI and 0.184 (0.081) for the second MRI. The Pfirrmann grading for the first MRI timepoint were as follows: 23 discs (1.42%) were Grade 1, 377 discs (23.2%) were Grade 2, 583 discs (35.9%) were Grade 3, 456 discs (28.1%) were Grade 4, and 186 discs (11.5%) were Grade 5. Multivariable linear mixed regression analysis demonstrated that older age (p=0.030) and the presence of congestive heart failure (p<0.001) were significant risk factors for disc nucleus degenerative progression. The present study demonstrated that age and congestive heart failure were risk factors for progression of disc nucleus degeneration. These insights may aid in identifying patients at risk for degenerative lumbar conditions and guide further studies about preventive measures. The DSI2 method offers a promising alternative evaluation method for future disc research.

Comparative analysis of morphologival parameters in isolated and fused L5 spondylolysis patients on the basis of CT features

Background and objectiveThe classification of lumbar spondylolysis varies, and there is currently no clear consensus on a standardized system. This study examines the morphological characteristics and parameter differences of the L5 vertebra in patients with isolated versus fused spondylolysis using CT measurements. It also proposes a preliminary classification system based on the separation distance at the fracture site and explores its clinical significance.MethodsA total of 117 young male patients with L5 spondylolysis related to high-intensity physical activity were enrolled. Patients with a pars interarticularis separation distance ≥ 2 mm were classified into the isolated group (Group A, 66 patients), while those with a separation distance < 1 mm were classified into the fused group (Group B, 51 patients).Additionally, 117 patients without spondylolysis but experiencing lower back pain were included as the control group (group C). Multislice spiral computed tomography (MSCT) was used to measure the morphological parameters of the L5 vertebra in all three groups, including the sagittal pedicle height (SPH), transverse pedicle width (TPW), transverse pedicle vertical length (TPVL), pedicle screw trajectory length (PSTL), pedicle angle of attack (PAA), frontal vertebral body height (FVH), posterior vertebral body height (PVH), sagittal midline intervertebral space height (SMISH), horizontal vertebral body angle (HVA), and vertical vertebral body angle (VVA). Differences in the morphological imaging parameters of the L5 vertebrae and pedicles among the three groups were compared.ResultsThere were no significant differences in age, height, weight, body mass index (BMI), or Pfirrmann grade among the three groups. No significant differences were observed in any of the pedicle parameters between the left and right sides within the groups. Group A showed significantly greater TPVL and PSTL values compared to Group B, while TPW and PAA were significantly lower. No significant difference in SPH was observed between Group A and Group B. When compared to Group C, Group A exhibited significant differences in SPH, TPW, TPVL, and PSTL, but not in PAA. Group B, compared to Group C, demonstrated significant differences in SPH and PAA, but no significant differences were observed in TPW, TPVL, or PSTL. Significant differences were also found in FVH, HVA, and VVA between Group A and Group B, with Group A showing a smaller PVH. No significant difference in SMISH was observed between the two groups. Compared to Group C, Group A showed significant differences in PVH, HVA, and VVA, but no significant differences were found in FVH or SMISH. In Group B, significant differences were noted in FVH and HVA compared to Group C, but no differences were observed in PVH, SMISH, or VVA.ConclusionDifferences in the sagittal morphological parameters of the pedicles and vertebral bodies can be observed between the two types of spondylolysis patients. In the isolated spondylolysis pattern, the pedicles exhibit a "thin, long, and contracted" morphology, while the vertebral bodies present a "stuffed bun" shape, both anteriorly, posteriorly, and superiorly. In contrast, the fused type is characterized by "short, thick, and expanded" pedicles, with the vertebral bodies showing a "less pronounced stuffed bun" shape in the anterior–posterior direction. These morphological differences indicate that spondylolysis separation may involve adaptive stress-induced bone remodeling. Surgeons must pay special attention when choosing surgical techniques, as isolated spondylolysis may present a tendency toward slippage. Caution is advised in performing isolated pars repair surgeries, especially during the placement of pedicle screws, where special attention must be given to the length and direction of the screws to avoid additional damage.

Exploring the Link Between Adjacent Lateral Incisor Morphology and Unilateral Maxillary Canine Impaction: A Cone-Beam Computed Tomography Study.

The maxillary canine plays a pivotal role in dental aesthetics, occlusion, and function because of its strategic anatomical positioning. However, the eruption of maxillary canines is a complex process that often leads to impaction. The anatomical and morphological characteristics of adjacent teeth, particularly the maxillary lateral incisors (MLIs), are believed to influence the eruption of maxillary canines. This study aimed to investigate the association between the morphology of MLI and unilateral impacted maxillary canines (IMCs) while also identifying potential predictors of such impactions. This retrospective study analyzedcone-beam computed tomography (CBCT) scans of 40 patients with unilateralIMC conducted between January 2020 and December 2023. Patients were selected based on the inclusion criteria that required intact MLIs adjacent to both impacted and non-impacted canines. CBCT imaging was performed using standardized protocols to assess crown dimensions, root length, angulation, and spatial relationships of the lateral incisors. The measurements were recorded independently by two calibrated observers. Statistical analyses included independent t-testsand multivariate logistic regression, with significance set at p < 0.05. Significant differences were observed in the morphological parameters of the MLI between the impacted and non-impacted sides. Root length and full length were significantly smaller on the impacted side (p < 0.05), whereas mesiodistal (MD) dimensions showed no significant difference. Labiolingual (LL) dimensions and angular measurements revealed significant variations, with mesially inclined and labially displaced roots on the impacted side. Sex differences were noted, with females exhibiting smaller root lengths and buccolingual (BL) dimensions than males. Multivariate logistic regression identified sex, root length, MD width, and angulation with the mid-sagittal plane (MSP) as significant predictors of IMC. Unilateral IMC weresignificantly associated with smaller root lengths, LL dimensions, and mesially inclined roots of MLI.

Automatic virtual reduction of unilateral zygomatic fractures based on ICP algorithm: A preliminary study.

To establish an automatic reduction method for unilateral zygomatic fractures based on Iterative Closes Point (ICP) algorithm. 60 patients with unilateral type B zygomatic fractures were included. After acquiring CT images, zygomatic fragments were segmented using self-developed software MICSys. Mid-Sagittal-Plane (MSP) was manually defined using anatomical skull landmarks. Surface of zygoma on the healthy side was then "mirrored" according to MSP. Referring to mirror image, the fragments were reduced by both automatic and manual methods. In automatic group, fragments were registered onto mirror images by ICP algorithm in MICSys. In manual group, an experienced maxillofacial surgeon translated and rotated fragments until coincided with mirror images. Operating time of each group was recorded. RMSE between reduced fragment and mirror image was calculated to evaluate accuracy. Operating time and accuracy between the two groups were compared using T-test. Virtual bone reduction was conducted for all 60 patients by the two methods. Operating time of automatic group and manual group were 3.06 ± 1.93 s and 65.45 ± 32.19 s, with significant difference (P < 0.0001). RMSE of automatic group and manual group were 1.94 ± 0.59 mm and 2.33 ± 0.57 mm, with significant difference (P < 0.0001). Automatic reduction method based on ICP Algorithm for unilateral zygomatic fractures was initially established and clinically acceptable.

Freehand Placement of a Transiliac-Transsacral Screw for Fixation of Posterior Pelvic Ring Injuries.

There are many advantages to stabilize the posterior pelvic ring injuries with a transiliac-transsacral (TITS) screw percutaneously. To identify the correct entry point and insert a guidewire accurately for a TITS screw, we propose a method of specifying the optimal entry point, and introduce a technique of enabling freehand placement of a guidewire with fluoroscopic guidance. In this retrospective study, 116 patients who underwent pelvic CT scans and pelvic lateral radiographs at our institution from January 2020 to April 2022 were enrolled. The optimal entry point for a TITS screw was formulated in the strict mid-sagittal CT plane, and then transferred to the pelvic lateral radiograph relying on the sacral cortexes which were easily visible even in the poor fluoroscopy. The relative position of this point to other anatomical markers was checked to confirm its feasibility as an entry point. With the method to locate the entry point, 18 patients suffered the posterior pelvic ring injuries were treated with TITS screws through hammering a reverse Kirschner wire (K-wire) to insert a guidewire assisted by a canula, followed by the validation of the screw placement accuracy. The transferred point in radiograph was consistently beneath the sacral alar slope, and located posteroinferior to the iliac cortical density (ICD) and anterosuperior to the sacral nerve root tunnel in all 116 patients. In clinical practice, 18 TITS screws were successfully placed in 18 patients without cortex violation. The average operative time for each screw was 20.11 ± 6.29 min, with an average of 14.11 ± 6.81 fluoroscopic shots per screw. At the 3-month follow-up, fracture healing was confirmed in all patients. The average Majeed score was 89.61 ± 6.90 at the final follow-up. It's feasible to identify an entry point for a TITS screw based on the sacral cortexes, and hammering a reverse K-wire assisted by a percutaneous kyphoplasty (PKP) canula is a safe and practical technique for guidewire insertion.

Microstructural Degeneration of the Corpus Callosum in Parkinson's Disease with Unilateral Onset: A Free-Water Imaging Study.

Background: Motor symptom laterality is an important clinical feature of PD that not only manifests as lateral limb dysfunction but also affects the nonmotor symptoms and the prognosis in PD patients. Previous studies suggested that the compensatory mechanisms in the dominant hemisphere of the brain may be an underlying explanation. The corpus callosum (CC) is the largest fiber connecting the two hemispheres of the brain. Considering the CC as the pointcut may help elucidate the mechanisms underlying how motor symptom laterality affects nonmotor symptoms and prognosis in PD patients. Purpose: To explore microstructural degeneration of the CC in PD patients with unilateral motor symptom onset and evaluate its relationship with motor and nonmotor performance. Methods: In this study, 201 right-handed PD patients with unilateral motor symptom onset (91 patients with left-onset [LPD] and 110 with right-onset [RPD]) and 100 right-handed healthy controls (HC) were included. A bitensor model of diffusion tensor imaging was applied to analyze free water (FW) as well as fractional anisotropy (FAT) and mean diffusivity (MDT) of the tissue compartment after correcting FW. These provide noninvasive in vivo measures of white matter integrity and pathological processes including atrophy, edema, and neuroinflammation. The CC was divided into halves along the median sagittal line, and each half was manually divided into five functional segments. A total of 10 subregions were obtained and numbered in sequence. The laterality index was calculated to quantify the asymmetry of the CC and its segments. A general linear model was used to compare among groups, and partial correlation analysis was performed to explore the relationships between the diffusion parameters of CC subregions and clinical manifestations. Results: Compared with HC, FW and FAT of the bilateral CC were decreased in the LPD group, whereas MDT in the right hemisphere was increased. In the LPD group, FAT of all CC subregions except for subregions 1, 3, and 6 was significantly lower than HC, and MDT in the anterior and posterior segments of the CC (CC subregions 1, 5-7, and 10) was significantly higher than HC. In the RPD group, FAT of subregion 7 was significantly decreased and MDT was increased than HC. Laterality index analysis of the CC indicated significant interhemispheric FAT asymmetry in the anterior and middle in the RPD group, with a more significant reduction in the right CC. Moreover, degeneration of the CC and its subregions was related to motor and nonmotor symptoms in PD. Conclusions: More extensive CC damage was observed in the LPD group than in the RPD group. Additional, asymmetrical damage was observed in the anterior and middle segments of the CC in the RPD group, suggesting that differences in callosal degeneration patterns may be a potential mechanism underlying how asymmetrical motor symptoms affect the nonmotor symptoms and prognosis in PD.

Variant of the Mathematical Theory of Non-Thin Multilayer Nonlinearly Elastic Plates of Symmetric Structures

A new version of the mathematical theory of non-thin multilayer nonlinearly elastic Kauderer plates of symmetric structures has been constructed. The components of the stress-strain state (SSS) and boundary conditions on the side surface of the plate are considered functions of three spatial coordinates. The variant is based on the development of components of the SSS of the plate along the transverse coordinate with the help of combinations of Legendre polynomials within each layer. The three-dimensional physically nonlinear boundary value problem for a multilayer non-thin plate is reduced to a two-dimensional one using the three-dimensional equations of the theory of elasticity and Reissner's variational principle. The main dependencies are obtained. Derived systems of high-order differential equations of equilibrium with partial derivatives and boundary conditions containing nonlinear terms from the SSS. The conjugation conditions at the boundary of adjacent layers (rigid connection) are exactly fulfilled for displacements, transverse tangential and normal stresses. The boundary conditions for stresses on the horizontal faces of the plate are also exactly fulfilled. The system of high-order differential equations of equilibrium is transformed into two systems that independently describe skew-symmetric and symmetric deformation relative to the median plane of the plate. In turn, each of these systems is transformed into differential equations that describe vortex boundary effects and equations that describe an internal SSS with a potential boundary layer-type boundary effect. The solution of systems of high-order equations by the developed method is reduced to the solution of second-order differential equations (Poisson and Helmholtz equations). General solutions of the system of differential equilibrium equations are obtained. The validity and accuracy of the variant of the mathematical theory is confirmed by comparisons with exact solutions of bending problems for linearly elastic plates with different mechanical and geometrical parameters. The newly constructed variant of the theory and the developed method provide a real opportunity to solve boundary problems in a spatial formulation with high accuracy for multilayer platens under various loads and boundary conditions on the lateral surface.

Newly Modified Posterior Axilla Maneuver: Tilt and Kristeller Procedure

Shoulder dystocia is a rare but severe complication of vaginal delivery with possibly serious consequences. Certain risk factors are associated with shoulder dystocia, but a general forecasting model is lacking. We present a Case report using a newly modified Posterior Axilla Maneuver technique that saved a 5.140 g (11 lbs. 5 oz.) newborn from shoulder dystocia. The child was born with Apgar 7/9, pH 7.17. Currently, there are no signs of any long-term sequelae. Our procedure comprised the following steps: 1. First, we pulled the posterior shoulder downwards - in the direction and to the outer surface of the perineum. 2. Then we pulled the posterior shoulder backward - toward the maternal spine - when it was already outside the perineum and finished extracting the posterior shoulder. 3. By completing the first two steps, a Tilt of the shoulder girdle was reached in the midsagittal plane, resulting in a backward slope for the shoulder girdle so that the anterior shoulder touched the symphysis slightly from the back in a skewed manner, freeing it from the initial impacted position. 4. We applied the Kristeller procedure only after dislodging the anterior shoulder from its initial impacted position. 5. We also applied the McRoberts Maneuver at the end of the process to increase the diameter of the birth canal.

Levator Veli Palatini Muscle Ratio Is a Clinically Significant Anatomic Predictor for Velopharyngeal Surgical Need.

Velopharyngeal insufficiency (VPI) poses challenges for normal speech production, often necessitating surgical intervention. Determining optimal candidates for surgery remains complex and requires a nuanced understanding of underlying anatomic factors contributing to VPI. This study aimed to identify anatomic predictors that drive surgical recommendations for VPI. Prospective observational cohort study. Pediatric tertiary care hospital. Magnetic resonance imaging data were acquired from 150 children (aged 4-17) to identify anatomic predictors of VPI and surgical need. Fourteen velopharyngeal variables were measured in the oblique coronal and midsagittal imaging planes. Calculations included differences in levator veli palatini (LVP) muscle angles of origin, mean extravelar length, differences between left and right extravelar segments, the VP Needs ratio, and a newly developed LVP ratio. Multivariate logistic regression models with k-fold cross validation were utilized to identify anatomic profiles predictive of VPI and receiving a surgical recommendation. The models demonstrated high accuracy, sensitivity, and specificity. Among anatomic variables, the LVP ratio emerged as the strongest determinant of surgical need (β = 11.256, p < .001). Notably, an increase in the LVP ratio of 0.10 is associated with a 3.08-fold increase in the likelihood of receiving a surgical recommendation. LVP ratios above 1.0 were significant for both VPI classification and surgical need. The LVP ratio significantly differentiates individuals with VPI and is predictive of surgical need for VPI management. Inclusion of the LVP ratio into clinical evaluations may refine patient stratification, enabling more precise surgical decision-making tailored to individual anatomic variations.

Application of CT radiomics in investigating the anatomical basis of chronic dacryocystitis

Objective:To explore the relevant anatomical factors in the pathogenesis of chronic dacryocystitis based on CT radiomics. Methods:A retrospective analysis was conducted on the general data and sinus CT materials of 85 patients with chronic dacryocystitis（case group） admitted to our department from December 2020 to December 2023, and 85 individuals undergoing physical examination（control group） during the same period. The differences in anatomical parameters between the two groups were compared to study the morphological characteristics of the nasolacrimal duct in patients with chronic dacryocystitis. Univariate and multivariate logistic regression analyses were used to explore the relevant anatomical factors in the pathogenesis of chronic dacryocystitis. Results:There were statistically significant differences（P<0.05） in the proportion of combined nasal septal deviation, the distance between the anterior and posterior ridges of the lacrimal fossa, the angle between the long axis of the nasolacrimal duct and the projection on the midsagittal plane, the maximum transverse diameter of the bony nasolacrimal duct, the maximum cross-sectional area of the bony nasolacrimal duct, and the thickness of the frontal process of the maxilla between the two groups. There were no statistically significant differences（P>0.05） in whether there was a combined high-position nasal septal deviation, whether there was a combined non-high-position nasal septal deviation, and whether there was a combined pneumatized middle turbinate. Multivariate analysis showed that nasal septal deviation, the distance between the anterior and posterior ridges of the lacrimal fossa, the angle between the long axis of the nasolacrimal duct and the projection on the midsagittal plane, and the maximum cross-sectional area of the bony nasolacrimal duct are independent anatomical factors affecting the pathogenesis of chronic dacryocystitis. Conclusion:Nasal septal deviation, a large distance between the anterior and posterior ridges of the lacrimal fossa, a large angle between the long axis of the nasolacrimal duct and the projection on the midsagittal plane, and a small maximum transverse diameter of the bony nasolacrimal duct are important anatomical bases for the pathogenesis of chronic dacryocystitis, providing a basis for an in-depth understanding of the disease occurrence.

OVERTURE Phase 2 MRI Analysis Demonstrates Reduced Corpus Callosum Atrophy in Alzheimer's Disease

AbstractBackgroundRecent research by Da et al. (2023) has demonstrated that non‐invasive gamma sensory stimulation can reduce brain white matter atrophy and myelin content loss. The impact on the Corpus Callosum (CC), the brain's largest commissural white matter tract essential for hemispheric connectivity, remains unexplored. Diffusion Tensor Imaging (DTI) studies (Delvenne et al. 2023), have identified variations and alterations in the CC's tract bundles in Alzheimer's disease (AD). We conducted an analysis of CC changes in patients along the Alzheimer’s continuum targeting both the overall and regional structural alterations.MethodIn this study, we used neuroimaging data from the OVERTURE clinical trial (NCT03556280). Participants were randomized 2:1 (Active: Sham) to receive daily, 1‐hour, audio and visual stimulation at gamma frequency or sham stimulation for 6 months. Magnetic Resonance Imaging (MRI) assessments were performed at baseline, month 3, and month 6. T1w MRI images were processed using the Yuki module within the Automated Registration Toolbox (ART) (Ardekani et al., 2014) with CC segmentation in the midsagittal plane (MSP) and its five subregions (Hampel et al., 1998). The analysis was conducted on participants with valid data for the total MSP CC and its subregions (N=50). Using Bayesian linear mixed‐effects modeling, we examined the changes in the area of the total MSP CC and its subregions.ResultThe active group demonstrated preservation of the total CC area and its subregions after six months of treatment. Differences in percentage changes between active and sham groups were: Total CC area (2.28±0.87%, p&lt;.02), genu/rostrum (2.36±0.90%, p&lt;.02), anterior‐body (2.64±1.26%, p&lt;.04), mid‐body (2.79±1.18%, p&lt;.03), posterior‐body (2.87±1.41%, p&lt;.05) and splenium (1.58±0.73%, p&lt;.04). Significant differences between the two groups were also observed in total CC area, genu/rostrum, and splenium at month 3.ConclusionOVERTURE Phase 2 MRI outcomes demonstrate that six months of non‐invasive gamma sensory stimulation may reduce the progression of CC atrophy in individuals with mild‐moderate AD, potentially preserving the integrity of interhemispheric communication. We are currently conducting a phase 3 clinical trial titled HOPE (NCT05637801) to evaluate the efficacy and safety of Cognito’s medical device.

Ultrasound estimates of the epidural depth in the paramedian sagittal oblique and transverse median planes: the correlation between estimated and actual depth to the epidural space in children with scoliosis

IntroductionThe present study aimed to compare the correlation and agreement of epidural depth estimation using ultrasound in the paramedian sagittal oblique (PSO) versus the transverse median (TM) plane relative to...

The White Matter Fiber Tract Deforms Most in the Perpendicular Direction During In Vivo Volunteer Impacts.

White matter (WM) tract-related strains are increasingly used to quantify brain mechanical responses, but their dynamics in live human brains during invivo impact conditions remain largely unknown. Existing research primarily looked into the normal strain along the WM fiber tracts (i.e., tract-oriented normal strain), but it is rarely the case that the fiber tract only endures tract-oriented normal strain during impacts. In this study, we aim to extend the invivo measurement of WM fiber deformation by quantifying the normal strain perpendicular to the fiber tract (i.e., tract-perpendicular normal strain) and the shear strain along and perpendicular to the fiber tract (i.e., tract-oriented shear strain and tract-perpendicular shear strain, respectively). To achieve this, we combine the three-dimensional strain tensor from the tagged magnetic resonance imaging with the diffusion tensor imaging (DTI) from an open-access dataset, including 44 volunteer impacts under two head loading modes, i.e., neck rotations (N = 30) and neck extensions (N = 14). The strain tensor is rotated to the coordinate system with one axis aligned with DTI-revealed fiber orientation, and then four tract-related strain measures are calculated. The results show that tract-perpendicular normal strain peaks are the largest among the four strain types (p < 0.05, Friedman's test). The distribution of tract-related strains is affected by the head loading mode, of which laterally symmetric patterns with respect to the midsagittal plane are noted under neck extensions, but not under neck rotations. Our study presents a comprehensive invivo strain quantification toward a multifaceted understanding of WM dynamics. We find that the WM fiber tract deforms most in the perpendicular direction, illuminating new fundamentals of brain mechanics. The reported strain images can be used to evaluate the fidelity of computational head models, especially those intended to predict fiber deformation under noninjurious conditions.

Assessing the Agreement Between Diffusion Tension Imaging (DTI) and T2-Weighted MRI Sequence for Biometry of the Fetal Corpus Callosum.

Little is known about the advantages of Diffusion Tensor Imaging (DTI) when evaluating the fetal corpus callosum (CC), a sensitive indicator for normal brain development. This study evaluates the contribution of DTI compared to T2-weighted imaging to assess fetal CC biometry. Data from the fetal MRI exams of singleton pregnancies between July 2017 and 2019 were retrospectively analyzed. Mid-sagittal sections were used to measure the CC biometry, and inter- and intra-observer agreements were assessed using the interclass correlation coefficient (ICC), targeting an ICC above 0.85. The results from 100 patients (mean gestational age, 32.24 weeks) indicated excellent inter-observer reliability for DTI (ICC = 0.904, 95% CI = 0.815-0.952) and moderate agreement for T2-weighted imaging (ICC = 0.719, 95% CI = 0.556-0.842). Intra-observer assessments showed excellent reliability for both DTI and T2-weighted imaging (ICC = 0.967, 95% CI = 0.933-0.984 and ICC = 0.942, 95% CI = 0.884-0.971, respectively). However, a comparison between DTI and T2-weighted images for CC biometry showed poor agreement (ICC = 0.290, 95% CI = 0.071-0.476). In conclusion, the study highlights a lack of agreement between DTI and T2-weighted imaging in fetal CC biometry, suggesting the need for further research to understand this discrepancy and the role of DTI in fetal health.

Numerical–Experimental Analysis to Optimize the Geometry of a Prosthetic Abutment

This paper aims to identify methods for optimizing the geometry of dental prosthesis preparation, through both an analytical study and a numerical investigation. Assuming a 10° inclined load with respect to the median sagittal plane, a double algorithm was developed that was capable of calculating the axial resistance area and the cusp resistance area (if present) of a prosthetic abutment as the main geometric parameters vary. In particular, a coupling model with a pseudo-elliptical base was proposed, which is better than the circular shape representing the real shape assumed by the abutment following the dental intervention. The model also allows the presence of a cusp. This model was first analyzed using FEA, also simulating the presence of coupling cement between the abutment and the crown, and then physically made with a 10:1 scale prototype. The convergence of the experimental results found with the numerical–theoretical studies is an indication of the validity of the proposed model. A key contribution of this research using the proposed algorithm allowed to demonstrate that a superior limit of 0.25 for the ratio (HR) between the heights of the cusp sulcus (h-hc) and the abutment (h) is required to achieve good stability of the coupling. The methodology developed in this study is applicable to a variety of teeth, making it versatile and highly adaptable for broader clinical applications.

New reference charts for fetal ultrasound corpus callosum length with emphasis on the third trimester

ObjectivesTo provide new prospective 2D ultrasound reference charts of fetal corpus callosum (CC) length on a large sample size with emphasis on the third trimester of pregnancy and to establish other standards of CC growth evaluation (external cranial occipitofrontal dimension (ECOFD) / CC length ratio and head circumference (HC) / CC length ratio) in a large population of healthy fetuses. MethodsA prospective observational study was conducted in a single expert center for fetal ultrasound between November 1st 2021 and June 30th 2022. CC measurement was performed in all fetuses examined between 17 weeks and 36+6 weeks. Image quality criteria for a strict mid-sagittal plane of the fetal brain and caliper position for CC measurement were defined prior to data collection and only high-quality measurements were included for analysis. Fetuses with inaccurate gestational ages and at high-risk of central nervous system anomalies were excluded. ResultsAmong 3591 CC measurements available, 3191 were included in this study. An accurate high-quality measurement was obtained in 92.8 % of cases. We established the third-degree polynomial model expressing the length of the corpus callosum as a function of Corpus callosum length in mm=0.00213x(GA in weeks)3 − 0.2538x(GA in weeks)2 + 10.5897xGA in weeks −108.8556 +/- SD (SD=0.0567xGA In weeks + 0.1054), with an R² adj of 0.94. ECOFD/CC and HC/CC ratios were stable throughout pregnancy at 2.7 ± 0.2 and 7.7 ± 0.6 respectively. ConclusionThese new reference charts were established using a uniform methodology of the highest quality in order to assess CC growth accurately and help clinicians correctly define a “short” CC. ECOFD/CC and HC/CC ratios may be used as additional markers of normal CC development in borderline cases.

Effects of spectral peaks and notches in head-related transfer function on median plane sound localization with dynamic binaural playback

Spectral peaks and notches in the head-related transfer function (HRTF) are considered pivotal for elevation perception in virtual auditory displays (VAD), especially during static binaural signal playback. However, studies on dynamic binaural signal playback in VAD have shown that the auditory system can still utilize dynamic cues for elevation localization, even when these high-frequency spectral components are missing, although this may compromise localization accuracy. This study investigated the effects of spectral peaks and notches in dynamic playback, examining how distorting these features and their contrasts at various levels (33%, 66%, and 100% removal) influenced elevation localization along different rotational axes (yaw and pitch rotation). The results revealed that at the same distortion level, the impact of these features on median plane localization decreased sequentially from spectral contrast, to peaks, to notches. At a distortion level of 33%, notch removal enabled dynamic playback results that were not significantly different from control conditions. As distortion levels increased to 66% and 100%, localization performance progressively deteriorated, including increased localization errors and up-down confusion with head yaw rotation as well as front-back and up-down confusion with head pitch rotation. Simultaneously, localization performance with head pitch rotation exhibited poorer performance compared to yaw rotation, particularly in cases involving peak removal and contrast compression. The experimental results further revealed that auditory elevation localization benefits from multiple localization cues generated by head movements, including dynamic spectral cues produced during large head rotations when all spectral cues are available or distorted at a level of 33%.

Cue for rear sound image localization in head-related transfer function below 4 kHz

It is known that notches and peaks at frequencies above 5 kHz in the head-related transfer function (HRTF) act as cues for median plane sound localization. However, it has also been shown that front-back discrimination of the direction of a sound image can be achieved even with only the components below 4 kHz. In the present study, we investigated the cues for rear sound image localization below 4 kHz. First, we analyzed the HRTFs for 118 ears (59 subjects) in the median plane and showed that the sound pressure around 1 kHz in the rear HRTF was larger than that in the front HRTF. This boosted band (hereinafter referred to as P0) coincided with Blauert’s directional band. Next, we proposed a hypothesis that can comprehensively explain the two types of cues that have been proposed in the past: spectral notches and peaks, and directional bands. In order to verify the effects of P0 for rear-direction localization, three preliminary psychoacoustic experiments were conducted. The results showed that eliminating P0 tends to increase localization errors at frequencies below 4 kHz. For wide-band signals, adding P0 to a previous parametric HRTF model (N1N2P1P2) tends to reduce the mean vertical localization error, and made the auditory source width approximately the same as that for the measured HRTF. These preliminary results support our hypothesis and imply that P0 acts as a cue for rear sound image localization.

Axial muscle‐fibre orientations in larval zebrafish

AbstractMost teleost fish propel themselves with lateral body waves powered by their axial muscles. These muscles also power suction feeding through rapid expansion of the mouth cavity. They consist of muscle segments (myomeres), separated by connective tissue sheets (myosepts). In adult teleosts, the fast axial muscle fibres follow pseudo‐helical trajectories, which are thought to distribute strain (relative fibre length change) approximately evenly across transverse sections during swimming, thereby optimizing power generation. To achieve strain equalization, a significant angle to the longitudinal axis on the frontal plane (azimuth) is necessary near the medial plane, increasing strain. Additionally, a deviation from longitudinal orientation on the sagittal plane (elevation) is required laterally to decrease strain. Despite several detailed morphological studies, our understanding of muscle‐fibre orientations in the entire axial musculature of fish remains incomplete. Furthermore, most research has been done in post‐larval stages, leaving a knowledge gap regarding the changing axial muscle architecture during larval development. Larval fish exhibit different body size, body shape and swimming kinematics compared to adults. They experience relatively high viscous forces, requiring higher tail‐beat amplitudes to overcome increased drag. Additionally, larval fish swim with higher tail‐beat frequencies. Histological studies have shown that in larval fish, muscle fibres in the anal region transition from an almost longitudinal orientation to a pseudo‐helical pattern by 3 dpf (days post‐fertilization). However, these studies were limited to a few sections of the body and were prone to shrinkage and tissue damage. Here, we introduce a novel methodology for quantifying muscle‐fibre orientations along the entire axial muscles. We selected 4 dpf larval zebrafish for our analyses, a stage where larvae are actively swimming but not yet free‐feeding. High‐resolution confocal 3D scans were obtained from four genetically modified zebrafish expressing green fluorescent protein in fast muscle fibres. Fluorescence variation allowed segmentation of individual muscle fibres, which were then converted to fish‐bound coordinates by correcting for the fish's position and orientation in the scan, and normalized to pool results across individuals. We show that at 4 dpf, muscle‐fibre trajectories exhibit a helical pattern tapering towards the tail. Average fibre angles decrease from anterior to posterior, with azimuth varying over the dorsoventral axis and elevation varying over the mediolateral axis. Notably, only the anteriormost 20% of the body displayed higher azimuth angles near the medial plane. Angles between neighbouring fibres were substantial, particularly at the rim of the epaxial and hypaxial muscles. The revealed muscle‐fibre architecture at this age presumably contributes to the swimming performance of these larvae, but that swimming performance is probably not the only driving factor for the fibre pattern. Our methodology offers a promising avenue for exploring muscle‐fibre orientations across ontogenetic series and provides a foundation for in‐depth functional studies on the role of muscle architecture in facilitating swimming performance of larval fish.

MRI Investigation of Kidneys, Ureters and Urinary Bladder in Rabbits.

Twelve clinically healthy and sexually mature New Zealand White rabbits were studied. The non-contrast imaging included T1-weighted and T2-weighted spin-echo and gradient-echo sequences in the transverse, sagittal and dorsal planes. Transverse MRI (T2-weighted image) through L1 demonstrated only the right kidney. The transverse T2-weighted image through L2 showed both kidneys. The cranial part of the urinary bladder on T1-weighted transverse scans through L4 was flexed to the left. The T2-weighted sagittal image 30 mm to the right of the median plane showed the right kidney, the right ureter and the urinary bladder. The T2-weighted sagittal image 30 mm to the left of the median plane showed part of the left kidney, the left ureter and the urinary bladder. The T2-weighted sagittal image 45 mm to the left of the median plane presented the lateral part of the left kidney. The dorsal MRI image (T2-weighted sequence) through the horizontal plane 30 mm ventral to the spine demonstrated the whole organs. These data will be useful in imaging anatomy and diagnostic studies of various pathologies of the excretory system in rabbits and other mammalian species.