Effects of PEEK Anisotropy Formed by 3D Printing on Mechanical Properties of Femoral Substitutes / 医用生物力学

Objective Aiming at the problem of significant anisotropy in the three-dimensional ( 3D) printed polyether-ether-ketone ( PEEK) bone substitutes manufactured by material extrusion technology, taking the femur, the main load-bearing long bone of the lower limb, as an example, the biomechanical properties of the femoral model under different direction in the build chamber were evaluated by the combination of finite element analysis and in-vitro mechanical experiment. Methods A left femoral model was obtained by reconstruction from CT data. The stress and displacement of the 3D printed PEEK femur with different directions in the build chamber under five physiological postures in the human gait cycle were simulated by varying the orthogonal anisotropy mechanical properties. An in-vitro mechanical experiment was conducted to investigate the safety and stability of the femur through a 3D printed PEEK femur. Results When the long axis of the femur model was perpendicular to the building platform of the 3D printer, a better mechanical property was obtained, and the maximum von Mises stress was 46. 56 MPa, which was lower than the yield stress of PEEK, while the maximum displacement was larger than that of the natural femur under same loading condition. Therefore, the 3D printed PEEK femur met the strength requirement, but the stability needs to be improved. Conclusions The long axis is recommended to be perpendicular to the building platform when the material extrusion technology was used for the substitute of the load-bearing long bone, and the effect of its anisotropy on service performance of the substitute should be carefully considered when the 3D printing technology is used for load-bearing bone substitute.

Smartphone as a tool for evaluating oblique muscle dysfunction / Uso do smartphone como ferramenta para avaliar disfunções de músculos oblíquos

ABSTRACT Purpose: The aim of this study was to describe a simple, accessible, and reliable method using a smartphone for evaluating oblique muscle dysfunctions. Methods: The photograph rotation tool in the iPhone PHOTO app was used by 75 examiners to evaluate 22 photographs from only 9 patients, captured in infra- and supra-dextroversion, and infra- and supra-levoversion, as not all the patients were photographed in the 4 positions mentioned. Each patient received a score for the superior and inferior oblique muscle functions, ranging from -4 (hypofunction) to 4 (hyperfunction) or 0 (normal function), using preediting and postediting photographs. These values were compared with the scores previously given by trained personnel in strabismus screening. The difference in score between the two groups was expressed in natural (whole and non-negative) numbers. The mean and pattern deviation were then calculated. Results: The scores of most of the edited photos showed a lower mean than those of the unedited ones, except for a patient with left superior oblique hyperfunction. The patients with no oblique dysfunction and those with right superior oblique hyperfunction demonstrated (after editing the photograph) scores with greater similarity with their initial scores (p<0.05 and p<0.01, respectively). Similar results were found in the patients with oblique hypofunctions and right inferior oblique hyperfunction (p<0.01). Conclusion: The proposed method for assessing muscular function in vertical strabismus is reproducible, accessible, simple, and reliable, and provides better consistency to the admeasurement.

RESUMO Objetivo: Descrição de um método simples, acessível e confiável para a medida das disfunções dos músculos oblíquos, utilizando-se smartphone. Métodos: Foi utilizado o recurso de rotação de fotografias do aplicativo FOTOS do iPhone®; 75 examinadores avaliaram 22 fotos de 9 pacientes, obtidas em infra e supra dextroversão, infra e supra levoversão (nem todos os pacientes foram fotografados nas 4 posições citadas). Conferiu-se aos pacientes uma pontuação para a função do músculo oblíquo superior e músculo oblíquo inferior, que variou de -4 (negativo para hipofunção) a +4 (positivo para hiperfunção), ou 0 (normofuncionantes), antes e depois da edição das fotografias. Esses valores foram comparados à avaliação prévia atribuída pelos assistentes do estrabismo. Computou-se a diferença da pontuação entre eles em números naturais (inteiros e não negativos); foram calculadas média e desvio padrão dessas medidas. Resultado: A medida da maioria das fotos editadas apresentou média inferior as não editadas, à exceção de um paciente com hiperfunção de oblíquo superior esquerdo. Pacientes sem disfunção de oblíquos demonstraram, após edição das fotos, maior similaridade com o valor inicialmente determinado (p<0,05), assim como os pacientes com oblíquo superior direito hiperfuncionantes (p<0,01). Os mesmos resultados são encontrados nos pacientes com hipofunção dos oblíquos e hiperfunção de oblíquo inferior direito (p<0,01). Conclusão: O método utilizado para medida das funções musculares nos estrabismos verticais é reprodutível, acessível, simples, confiável, e confere maior uniformidade à aferição.

Cingulum bundle integrity in schizophrenia with auditory verbal hallucinations: A diffusion tensor imaging tractographic study

Background & objectives: Cingulum bundle (CB) is frequently implicated in schizophrenia; however, its role in specific symptoms of schizophrenia such as auditory verbal hallucinations (AVHs) is less explored. Few studies have reported association between reduced integrity of CB and severity of AVH. Using a symptom-based approach, this diffusion tensor imaging (DTI) tractographic study was aimed to assess and compare the integrity of CB in schizophrenia with AVH, schizophrenia without AVH and healthy controls. Methods: A total of 92 right-handed adult individuals (aged 18-50 yr) were recruited across three study groups. Those with Diagnostic and Statistical Manual of Mental Disorders-5 (DSM-5) diagnosis of schizophrenia with AVH (group I; n=30) were compared to those with DSM-5 schizophrenia without lifetime AVH (group II; n=32) and healthy controls (group III; n=30; screened using Mini International Neuropsychiatric Interview version-7.0.0. and negative family history). Clinical assessments (groups I and II) included scale for assessment of positive symptoms, scale for assessment of negative symptoms, clinical global impression-schizophrenia and psychotic symptom rating scale. All participants underwent DTI, and quantitative tract-based measurements of fractional anisotropy (FA) were obtained for images using DTI studio version-3.0. Results: All groups were comparable for age, gender, education and severity of illness. Group I had significantly lower FA values in the cingulate gyrus (CG) part of the left CB compared to groups II and III. No significant difference was found between groups II and III. Interpretation & conclusions: The findings of this study suggest that the disruption in the left CB appears to be specific for AVH-positive schizophrenia. The finding is, however, preliminary subject to replication in future studies. Further investigations are needed to understand its relevance in the context of AVH-positive schizophrenia.

Study on Anisotropy Properties of in vitro Pig Trachea and Numerical Simulation / 医用生物力学

Objective To study mechanical properties of the anisotropy for pig trachea and main bronchi, and determine the constitutive model of trachea deformation by finite element numerical simulation. Methods The pig tracheas were collected and cut through in their axial directions and expanded into two-dimensional planes. Then, by setting the length direction of the trachea aortas as 0°, each planar trachea was anticlockwisely cut into 6 samples with orientation of 30°,60°,90°,120°,150° and 180°, respectively. Uniaxial tensile tests were applied on the specimen in 6 angular directions by using the electronic universal test machine, to obtain stress and strain of the specimen in different directions. Nonlinear fitting to the experimental data was performed by using the Mooney-Rivilin hyperelastic model, in order to obtain the material characteristic parameters. Finite element models of the trachea and the main bronchi were established, and tensile numerical simulation was carried out.Results Samples at different angles showed different stress-strain curves. In the trachea, the stresses of samples with angle of 30°, 120° and 150° were in the range of 1.0-1.5 MPa, the stresses of samples with angle of 60° and 90° were in the range of 0.5-1.0 MPa, and the stresses of samples with angle of 180° were in the range of 2.5-3.0 MPa. In the main bronchi, the stresses of samples with angle of 30°, 120° and 150° were in the range of 0.8-1.0 MPa, the stresses of samples with angle of 90° and 180° were in the range of 1.4-1.8 MPa, and the stresses of samples with angle of 120° were in the range of 0.4-0.6 MPa. There was an obvious difference between the trachea and the main bronchi. The finite element simulation verified that the Mooney-Rivilin constitutive model was suitable for describing small deformation behavior of the trachea. Conclusions The pig trachea exhibits strong anisotropy. Meanwhile, the Mooney-Rivilin model can characterize small tracheal deformations. The results provide theoretical references for tracheal resection and reconstruction in clinical treatment and intervention with surgical instruments such as bronchoscopy.

Associations of white matter microstructural abnormalities with clinical symptoms, cognitive impairment and clinical outcomes in the early course of first-episode schizophrenia / 中华行为医学与脑科学杂志

Objective:To investigate the associations of brain white matter integrity deficits, and to explore the association of fractional anisotropy (FA) abnormality with clinical symptoms and cognitive impairments, as well as the prediction effect of the FA alterations on symptoms and cognitive function outcomes in the acute stage of schizophrenia from the whole brain level based on magnetic resonance diffusion tensor imaging (DTI).Methods:From November 2019 to December 2020, thirty-eight patients with first-episode schizophrenia and 38 healthy controls were recruited in this study. Wisconsin card classification test (WCST), digit span test (DST forward/backward), verbal fluency test, Stroop (A/B/C), trail making test (TMT-A/B), as well as positive and negative syndrome scale (PANSS) were utilized to evaluate patients' cognitive function and clinical symptoms both before and after 8 weeks of risperidone monotherapy. T1-weighted images and DTI data of all the subjects were collected . FSL and SPM8 were used to preprocess MRI data and compare the between-group differences of FA. Support vector machine (SVM) analysis was used to evaluate the accuracy of abnormal FA values in differentiating schizophrenic patients from healthy controls. Finally, stepwise multiple regression analysis or generalized linear models were used to explore the associations between white matter integrity and symptoms or cognition.Results:Before treatment, patients' FA values of right medial temporal lobe (mTL), cuneus, anterior cingulate gyrus (ACG) and inferior parietal lobe (IPL) were significantly lower than those in healthy controls ( P<0.01, GRF corrected), and patients' FA values of bilateral middle cingulate gyrus (mCG) were significantly higher than those in the control group ( P<0.01, GRF corrected). SVM analysis showed that four combinations could distinguish the patients from the control with the most accurate rate of 89.47%. Patients' baseline decreased FA values in the right IPL were positively associated with their increased total response time in WCST ( β=0.489, P=0.003, FDR corrected), correct response time in WCST ( β=0.450, P=0.008, FDR corrected), error response time in WCST ( β=0.435, P=0.008, FDR corrected), TMT-B ( β=0.296, P=0.042, FDR corrected), Stroop-C ( β=0.345, P=0.035, FDR corrected), and PANSS-P ( β=0.321, P=0.042, FDR corrected). Reduced FA values in the right mTL in patient group were significantly negatively related to the total time spent on the TMT-A ( β=-0.425, P=0.009, FDR corrected) and TMT-B ( β=-0.325, P=0.026 with FDR correction). Increased FA values in right mCG in patient group demonstrated positive associations with total response time in the WCST ( β=0.585, P=0.002, FDR corrected), correct response time in WCST ( β=0.524, P=0.003, FDR corrected), error response time in WCST ( β=0.536, P=0.003, FDR corrected) and total time consuming in TMT-B ( β=0.484, P=0.004, FDR corrected), as well as negative associations with DST-forward ( β=-0.319, P=0.042, FDR corrected). After treatment, patients' percentage changes in total response time of WCST ( β=0.715, P<0.001, FDR corrected), correct response time of WCST ( β=0.752, P<0.001, FDR corrected), as well as total time-consuming of TMT-A ( β=1.333, P=0.001, FDR corrected) showed positive correlations with baseline increased FA values in the left mCG. Percentage alteration of Stroop-B was negatively correlated with baseline FA values in the right cuneus ( β=-0.745, P=0.015, FDR corrected). Conclusions:The combination of abnormal FA values in multiple brain regions may be potential biomarkers to distinguish schizophrenic patients from healthy volunteers. There was regional dependence in the associations of the impairment of white matter integrity with the cognitive impairment, the severity of psychopathological symptoms as well as the prognosis of patients in the acute stage.

Altered white matter microarchitecture in Parkinson's disease: a voxel-based meta-analysis of diffusion tensor imaging studies / 医学前沿

This study aimed to define the most consistent white matter microarchitecture pattern in Parkinson's disease (PD) reflected by fractional anisotropy (FA), addressing clinical profiles and methodology-related heterogeneity. Web-based publication databases were searched to conduct a meta-analysis of whole-brain diffusion tensor imaging studies comparing PD with healthy controls (HC) using the anisotropic effect size-signed differential mapping. A total of 808 patients with PD and 760 HC coming from 27 databases were finally included. Subgroup analyses were conducted considering heterogeneity with respect to medication status, disease stage, analysis methods, and the number of diffusion directions in acquisition. Compared with HC, patients with PD had decreased FA in the left middle cerebellar peduncle, corpus callosum (CC), left inferior fronto-occipital fasciculus, and right inferior longitudinal fasciculus. Most of the main results remained unchanged in subgroup meta-analyses of medicated patients, early stage patients, voxel-based analysis, and acquisition with 30 diffusion directions. The subgroup meta-analysis of medication-free patients showed FA decrease in the right olfactory cortex. The cerebellum and CC, associated with typical motor impairment, showed the most consistent FA decreases in PD. Medication status, analysis approaches, and the number of diffusion directions have an important impact on the findings, needing careful evaluation in future meta-analyses.

Diffusion tensor imaging in assessment of demyelinating diseases of central nervous system

Background: Conventional MR plays an important role in detection of demyelinating lesions. Involvement of the lesion core, perilesional region and normally appearing white matter (NAWM) cannot be quantified using routine T2/FLAIR sequences. DTI is an important tool in assessment of anisotropy in affected and apparently normal region of brain. 3D Tractography maps are useful in showing white matter fibre loss. Aim was the assessment of white matter damage and neuroaxonal loss using DTI in demyelinating lesionsMethods: Cross sectional observational study including clinically suspected 30 patients of demyelinating disease. Patients were studied in 3Tesla Siemens Skyra MRI scanner with phased array coils. T1w, T2w, FLAIR, DWI, DTI, post contrast T1w images were included and FA, ADC, Tractography maps were generated. ANOVA test and BONFERONI analysis were used.Results: We found mean FA of core lesion was 0.307±0.06, of perilesional region 0.444±0.03 and NAWM 0.567±0.06. The mean ADC value of core of the lesion was 1.24×10-3mm2/sec±0.11×10-3mm2/sec, perilesional region 1.16×10-6mm2/sec ±0.1×10-3mm2/sec and NAWM 1.04×10-3mm2/sec±0.06×10-3mm2/sec.Conclusions: DTI is a useful MR technique that allows quantification of extent of demyelination in the white matter measuring FA and ADC values. The FA values which denote diffusivity and directionality are more reliable marker of demyelination compared to ADC values. DTI Tractography shows white matter tract disruption which may play role in assessing clinical outcome of patients.

Volumetría de fascículos cerebrales en población sana / Brain fascicles volumetry in healthy population

Objetivo Desde la aparición de la tractografía, al tratarse de una técnica no invasiva y que usa la ampliamente conocida resonancia magnética (RM), el estudio de la sustancia blanca se ha facilitado. A partir de eso, se han logrado grandes descubrimientos en cuanto a fascículos cerebrales involucrados en funciones cognitivas. Sin embargo, su evaluación sigue siendo subjetiva y depende de la experiencia y entrenamiento del evaluador, razón por la cual se ha limitado su aplicabilidad en la práctica clínica. En ese sentido, es conveniente parametrizar volúmenes cerebrales de sustancia blanca en población sana a través de una herramienta electrónica que se pueda reproducir y así poderlo aplicar en enfermos. Materiales y métodos Se reportan 10 sujetos sanos desde el punto de vista neurológico. Para cada sujeto, se adquirieron imágenes ponderadas por difusión y los resultados se visualizaron mediante FiberNavigator (http://scilus.github.io/fibernavigator). Finalmente, esa misma herramienta fue utilizada para purificar los fascículos objeto de estudio y realizar el conteo de las fibras. Resultados Se obtuvieron valores de volumetría del fascículo longitudinal superior (FLS), fascículo longitudinal inferior (FLI), fascículo frontoccipital inferior (FFI), fascículo uncinado (FU) y fascículo del cíngulo (FC), identificando que no existen diferencias estadísticamente significativas entre el número de fibras que componen los fascículos cerebrales. Discusión Los resultados alcanzados de la anatomía y la direccionalidad de fibras de los fascículos cerebrales de este estudio coinciden con el resto de la evidencia publicada hasta el momento, sin encontrar diferencias en cuanto a su organización y recorrido. Conclusión Aunque esos resultados no sirven como valores de referencia para ser aplicados en pacientes con patología neurológica, brindamos información inexistente hasta el momento, con ese equipo en específico y la reproducción entre los distintos usuarios y el software.

Objective Since the appearance of tractography, as it is a non-invasive technique and uses the widely known magnetic resonance (MR), the study of white matter has been facilitated. After this, great discoveries have been made regarding the brain fascicles involved in cognitive functions. However, its evaluation continues to be subjective and depends on the evaluator's experience and training. That the reason why its applicability has been limited in clinical practice. Because of this, it is convenient to parametrize cerebral volumes of white matter in healthy population through an electronic, reproducible tool that could be applied in patients. Materials and Methods Ten neurologically healthy subjects are reported, for each subject we acquired images weighted by diffusion and the results were visualized by means of FiberNavigator (http://scilus.github.io/fibernavigator). Finally, this same tool was used to purify the fascicles under study and perform the fiber count. Results Volumetric values of the upper longitudinal fasciculus, inferior longitudinal fasciculus, inferior frontoccipital fasciculus, uncinated fasciculus and cingulate fasciculus were obtained, identifying that there are not statistically significant differences in the number of fibers that make up the cerebral fascicles. Discussion The results achieved of the anatomical and fiber directionality of the cerebral fascicles of this study, coincide with the rest of the evidence published up to now, without finding differences regarding its organization and route. Conclusion Although these results do not serve as reference values to be applied in patients with neurological pathology, do we provide nonexistent information so far, with this specific equipment and the reproducibility between the different users and the software.

DTI study of neonatal hyperbilirubinemia brain injury based on cerebellar dentate nucleus / 中国医师杂志

Objective Magnetic resonance diffusion tensor imaging ( DTI) technique was used to investigate the changes of DTI parameters in nerve fiber bundles of children with hyperbilirubinemia. Meth-ods A retrospective analysis of DTI imaging data of 43 children with hyperbilirubinemia and 24 normal controls in our hospital using the German Siemens 3. 0t Trio superconducting magnetic resonance imaging in-strument from December 2016 to March 2018. Children with hyperbilirubinemia were divided into two groups, total serum bilirubin mildly elevated group (34 cases) and total serum bilirubin moderate to severe elevation group (9 cases). The right and left cerebellar dentate nuclei were selected as the regions of inter-est. Relevant parameters were measured, and the parameters of each group were analyzed and compared. Results Compared with the normal control group,the fractional anisotropy ( FA) of the total serum biliru-bin mildly elevated group was decreased ( P=0. 022 ) and the volume ratio ( VR ) of that was increased (P=0. 036). Compared with the normal control group, the FA of the total serum bilirubin moderate to se-vere elevation group was decreased (P=0. 002) and the VR of that was increased (P=0. 047). Compared with the total serum bilirubin mildly elevated group,the FA of the total serum bilirubin moderate to severe elevation group was decreased (P=0. 035). In addition, in the cerebellar dentate nucleus, there was a lin-ear negative correlation (r= -0. 201, P=0. 029) between the FA values and the total bilirubin level, while linear positive correlation (r=0. 245, P=0. 045) between the VR value and the total bilirubin level. Conclusions There are changes in FA and VR values of the cerebellar dentate nucleus in children with hy-perbilirubinemia,which of them are linearly related to bilirubin levels. It can early indicate the destruction or dysplasia of nerve fiber bundles in children.

Effect of construction orientation on the microstructure and properties of SLM Ti alloy clasps / 口腔疾病防治

Objective@#To investigate the physical properties of Ti-6Al-4V clasps generated by selective laser melting (SLM) with different construction directions and to compare these clasps with cast clasps, which could provide a basis for fabricating SLM clasps with high precision and excellent mechanical properties. @*Methods@# Ti-6Al-4V clasps were fabricated by SLM at 0 degrees (SLM0 group), 45 degrees (SLM45 group) and 90 degrees (SLM90 group) (n = 12). Twelve clasps were cast by the casting method as the control group. Meanwhile, four metal abutments were cast randomly as the abutments of the four groups. X-ray was used to detect cracks in the clasps of each group. The roughness of the clasps was measured by confocal microscopy, the fitness tests between clasps and abutment were processed by stereomicroscopy, and the microstructure of clasps in each group was observed under a metallographic microscope to evaluate the physical properties.@*Results @# There were 0-8 visible cracks in the casting group but no obvious defects in the SLM groups. The maximum surface roughness was observed in the cast group (18.102 ± 3.762) μm, while the minimum roughness was observed in the SLM90 group (5.942 ± 1.486) μm (P < 0.05). There was no statistically significant difference in surface roughness between the SLM0 group [(8.711 ± 2.378) μm] and the SLM45 group [(8.513 ± 1.161) μm]. Fitness was worst in the casting group [(68.445 ± 14.876) μm] and best in the SLM90 group [(33.417 ± 5.880) μm] (P < 0.05). There was no statistically significant difference in fitness between the SLM0 group [(52.917 ± 12.102) μm] and the SLM45 group [(50.889 ± 7.011) μm]. In addition, the growth direction of the β grains was roughly parallel to the build direction, and acicular α grains were present between β grains. SLM was composed of fine grains, while the cast group had large grains.@* Conclusions@# Specimens generated by SLM had finer grains than cast specimens. In addition, SLM90 clasps had the highest fitness and the lowest surface roughness.

Research on mode of anisotropy and other diffusion tensor imaging derived indices of white matter with mild to moderate Alzheimer disease based on tract based spatial statistics / 中华放射学杂志

Objective We performed a diffusion tensor imaging (DTI) study to explore the value of mode of anisotropy (MO) and other DTI-derived indices in assessing white matter fiber damage with mild to moderate Alzheimer disease (AD) patients. Methods This study was a prospective study. From February 2015 to February 2018, 33 patients with mild to moderate AD according to criteria were prospectively recruited as AD group at the First Affiliated Hospital of Wenzhou Medical University. Twenty healthy age-, sex-matched volunteers were recruited as normoal conctrast (NC) group. All subjects were performed by conventional brain MRI and DTI scans. The MO, anisotropic fraction (FA), mean diffusivity (MD), radial diffusivity (RD) and axial diffusivity (AxD) of white matter fibers were obtained from DTI images after TBSS post-processing. The statistical analyses of DTI indices between AD group and NC group were carried out in Functional MRI Software Library software. Results As compared with NC group, we found 1 cluster with significant decrease FA and increase RD in AD group, the affected fibers involving bilateral anterior thalamic radiation, corticospinal tract, cingulate gyrus, hippocampus, inferior fronto-occipital fasciculus, inferior longitudinal fasciculus, uncinated fasciculus, superior longitudinal fasciculus (P<0.05). The MD value increase(P<0.1) was found to coincide with the decrease of FA and the increase of RD, while no significant increase or decrease in P<0.05. Three clusters of MO increases (P<0.05) accompanying with increases of AxD were found in left anterior limb of internal capsule, bilateral posterior limb of internal capsule, posterior forceps, left centrum semiovale and parietal lobe. Two clusters of MO decreases (P<0.05) accompanying with decreases of FA and increases of RD were found in fornix, forceps, external capsule, centrum semiovale and left frontal lobe. Conclusions The combination of MO with DTI routine tensor indices (FA, RD, MD, AxD) can further reveal the microstructural damage of white matter fibers in AD, especially to crossing-fibers. The abnormalities of MO combined with FA, RD and MD reveal the degeneration of both bundles of crossing-fibers,and the abnormalities of MO combined with AxD reveal that the white matter damage was mainly caused by axon damage of one bundle of cross fibers.

Quantitative Predictive Imaging Biomarkers of Lumbar Intervertebral Disc Degeneration

STUDY DESIGN: Observational comparative study. PURPOSE: To compare fractional anisotropy (FA) maps with T2 values of the nucleus pulposus (NP) and annulus fibrosus (AF) of intervertebral discs in healthy volunteers and patients to develop a predictive disc health scale. OVERVIEW OF LITERATURE: T2-weighted magnetic resonance imaging (MRI) is not sensitive to early morphological changes and provides no quantitative biomarker profile for early degeneration. METHODS: We examined 59 healthy controls and 59 patients with back pain by MRI using T2 relaxometry and diffusion tensor imaging (DTI). Each group was divided into three age subgroups: A (50 years, n=21). We obtained FA values for AF and NP and T2 values for NP for each intervertebral disc. Furthermore, we calculated the FA (AF/NP) ratios. RESULTS: We categorized 590 intervertebral discs from 118 participants, 566 of which were analyzed with T2 relaxometry and DTI. The T2 values were as follows: subgroup A, 55.8±4.4 ms; B, 48.5±6.9 ms; C, 45.8±8.7 ms (p120 ms, 90–100 ms, and 70 ms, respectively (p<0.001). Control subgroup A had higher T2 values and AF/NP ratios than subgroups B and C; the AF values were not significantly different. Control subgroup B had higher T2 values and AF/NP ratios than subgroup C but lower FA (NP). CONCLUSIONS: FA maps of the AF/NP ratio and T2 values of NP are potential microstructure biomarkers of normal and degenerating discs and can help detect early degeneration using a predictive disc health score on a continuous scale.

Clinical features and corneal optical anisotropies in a rabbit model of limbal stem cell deficiency / Fenótipos clínicos e anisotropias ópticas da córnea em coelhos com deficiência de células tronco limbais

ABSTRACT Purposes: To investigate the intra-laboratory reproducibility of clinical features and to evaluate corneal optical anisotropies in a rabbit model of limbal stem cell deficiency. Methods: Limbal injury was induced in the right eye of 23 adult New Zealand White rabbits using a highly aggressive protocol that combined 360 degrees limbal peritomy, keratolimbectomy, alkaline chemical burn, and mechanical removal of the epithelium. Clinical evaluation of the injured eyes was performed for 28 days and included corneal impression cytology. Corneas with a severe clinical outcome set typical of limbal stem cell deficiency were then collected, subjected to a histopathological examination, and examined for optical anisotropies. Corneas from healthy rabbit eyes were used as controls. Differences in optical path due to stromal collagen birefringence, as well as linear dichroism related to the expression and spatial orientation of glycosaminoglycan chains from proteoglycans, were measured from cross-sections under a quantitative polarized light microscope. Results: One eye showed signs of hypopyon and was excluded. Signs of ocular inflammation were observed in all eyes studied (n=22). Corneal impression cytology did not detect goblet cells. Twelve of the 22 corneas presented a clinical outcome set typical of limbal stem cell deficiency, which is characterized by the presence of epithelial defects, inflammatory cells, moderate-to-severe opacity, and neovascularization. Microscopic studies under polarized light revealed that relative to controls, limbal stem cell deficiency caused a 24.4% increase in corneal optical path differences. Further, corneas with limbal stem cell deficiency were less dichroic than controls. Conclusions: These results suggest that rabbit models of limbal stem cell deficiency must be rigorously screened for use in preclinical studies to ensure experimental homogeneity because protocols used to create limbal stem cell deficiency could be not associated with good intra-laboratory reproducibility of clinical features. Limbal stem cell deficiency, as induced herein, altered the optical anisotropic properties of the corneal stroma. Such alterations are indicative of changes in collagen packing and the spatial orientation of glycosaminoglycan chains from proteoglycans. Knowledge of these changes is important to potentiate strategies aimed at restoring the morphofunctional integrity of the corneal stroma affected by limbal stem cell deficiency.

RESUMO Objetivos: Investigar a reprodutibilidade intra-la­boratorial dos fenótipos clínicos e avaliar anisotropias ópticas em córneas de coelhos com deficiência de células tronco limbais. Métodos: Lesões ao limbo foram feitas no olho direito de 23 coelhos adultos da Nova Zelândia Branco, usando um protocolo altamente agressivo, que envolveu peritomia limbal em 360 graus, ceratolimbectomia, cauterização por álcali, e remoção mecânica de epitélio remanescente. Os olhos foram clinicamente avaliados por 28 dias, inclusive por citologia de impressão corneal. As córneas que manifestaram um conjunto de alterações típicas de deficiência de células tronco limbais foram coletadas e submetidas à estudos em histopatologia e em anisotropias ópticas. Córneas saudáveis foram usadas como controles. Diferenças de caminho óptico de birrefringência relacionada à organização do colágeno estromal, e dicroísmo linear relacionado à expressão e à orientação das cadeias de glicosaminoglicanos dos proteoglicanos estromais, foram quantificados por microscopia de luz polarizada. Resultados: Um olho apresentou hipópio e foi excluído do estudo. Todos os olhos estudados (n=22) apresentaram sinais de inflamação ocular. A citologia de impressão não detectou células caliciformes na superfície corneal. Doze de 22 córneas manifestaram alterações clínicas típicas de deficiência de células tronco limbais, caracterizado por defeitos epiteliais, infiltrados inflamatórios, opacidade de moderada à severa, e neovascularização. Estudos por microscopia de luz polarizada mostraram que a deficiência de células tronco limbais aumentou a diferenças de caminho óptico corneal em 24,4% (versus controles). As cór­neas com deficiência de células tronco limbais foram menos dicroicas do que as córneas controle. Conclusões: Coelhos com deficiência de células tronco limbais, para aplicações em estudos pré-clínicos, devem ser rigorosamente selecionados para assegurar homogeneidade experimental, pois há evidências de que protocolos utilizados para indução de deficiência de células tronco limbais não estão associados com boa reprodutibilidade intra-laboratorial de fenótipos clínicos. A deficiência de células tronco limbais, como induzida aqui, alterou as propriedades ópticas anisotrópicas do estroma corneal. Tais alterações são indicativas de mudanças no empacotamento de colágeno e na orientação das cadeias de glicosaminoglicanos dos proteoglicanos. Conhecimentos nessas alterações são importantes para potencializar estratégias que visam a restabelecer a integridade morfofuncional do estromal corneal acometido pela deficiência de células tronco limbais.

Application of MR diffusion tensor imaging in rats with spinal cord inj ury in early stage / 实用放射学杂志

Objective To investigate the value of diffusion tensor imaging(DTI)in the evaluation of diffuse microstructural changes in early stage of spinal cord injury (SCI)in rats.Methods Improved Allen's method was used to make SCI in rats model.The rats were divided in the group of four as control,mild,moderate and severe injury groups respectively.We used DTI parameters [fraction anisotropy (FA)and apparent diffusion coefficient(ADC)]values to observe the spinal cord at different stages (6,24 and 72 hours) after spinal injury in the rats.Results The FA value of the spinal cord began to decrease at 6 hours and reached the lowest at 24 hours after SCI (P<0.05).There were significant differences in FA values between mild,moderate,and severe injury groups (P<0.05). However,ADC value was seen decreased only in the severe injury group,which was lowest at 24 hours after SCI(P<0.05).Conclusion Compared with ADC value,FA value can better reflect the severity of spinal cord injury in rats with acute SCI.FA values are correlated with the degrees of injury of spinal cord.

Application of magnetic resonance diffusion tensor imaging in rat C 6 glioma grading / 重庆医学

Objective To explore the application value of fractional anisotropy(FA)values of magnetic resonance diffusion tensor imaging(DTI)parameters in rat rat glioma grading.Methods Sixty-seven female Wistar rats were divided into the experi-mental group(n=57)and control group(n=10)according to the random number table method.All the surviving rats were exam-ined by 3.0T DTI at 1-2 weeks(22 cases)and 3-4 weeks(35 cases)after inoculation,and the FA values of the tumor were ob-tained and compared with the pathological results.Results Among 57 tumor-loading rats,there were 18 low-grade gliomas and 39 high-grade gliomas.DTI showed that the FA value of high-grade gliomas was higher than that of the low-grade glioma,the differ-ence was statistically significant[(0.167 ± 0.035)vs.(0.147 ± 0.015),t=2.34,P<0.05].Conclusion The FA value of DTI pa-rameters can provide accurate,reliable and noninvasive imaging information for preoperative glioma grading.

Diffusion Tensor-Derived Properties of Benign Oligemia, True “at Risk” Penumbra, and Infarct Core during the First Three Hours of Stroke Onset: A Rat Model

OBJECTIVE: The aim of this study was to investigate diffusion tensor (DT) imaging-derived properties of benign oligemia, true “at risk” penumbra (TP), and the infarct core (IC) during the first 3 hours of stroke onset. MATERIALS AND METHODS: The study was approved by the local animal care and use committee. DT imaging data were obtained from 14 rats after permanent middle cerebral artery occlusion (pMCAO) using a 7T magnetic resonance scanner (Bruker) in room air. Relative cerebral blood flow and apparent diffusion coefficient (ADC) maps were generated to define oligemia, TP, IC, and normal tissue (NT) every 30 minutes up to 3 hours. Relative fractional anisotropy (rFA), pure anisotropy (rq), diffusion magnitude (rL), ADC (rADC), axial diffusivity (rAD), and radial diffusivity (rRD) values were derived by comparison with the contralateral normal brain. RESULTS: The mean volume of oligemia was 24.7 ± 14.1 mm³, that of TP was 81.3 ± 62.6 mm³, and that of IC was 123.0 ± 85.2 mm³ at 30 minutes after pMCAO. rFA showed an initial paradoxical 10% increase in IC and TP, and declined afterward. The rq, rL, rADC, rAD, and rRD showed an initial discrepant decrease in IC (from −24% to −36%) as compared with TP (from −7% to −13%). Significant differences (p < 0.05) in metrics, except rFA, were found between tissue subtypes in the first 2.5 hours. The rq demonstrated the best overall performance in discriminating TP from IC (accuracy = 92.6%, area under curve = 0.93) and the optimal cutoff value was −33.90%. The metric values for oligemia and NT remained similar at all time points. CONCLUSION: Benign oligemia is small and remains microstructurally normal under pMCAO. TP and IC show a distinct evolution of DT-derived properties within the first 3 hours of stroke onset, and are thus potentially useful in predicting the fate of ischemic brain.

Safety of Autologous Umbilical Cord Blood Therapy for Acquired Sensorineural Hearing Loss in Children

BACKGROUND AND OBJECTIVES: Sensorineural hearing loss (SNHL) in children is associated with neurocognitive morbidity. The cause of SNHL is a loss of hair cells in the organ of Corti. There are currently no reparative treatments for SNHL. Numerous studies suggest that cord blood mononuclear cells (human umbilical cord blood, hUCB) allow at least partial restoration of SNHL by enabling repair of a damaged organ of Corti. Our objective is to determine if hUCB is a safe treatment for moderate to severe acquired SNHL in children. SUBJECTS AND METHODS: Eleven children aged 6 months to 6 years with moderate to severe acquired SNHL were treated with intravenous autologous hUCB. The cell dose ranged from 8 to 30 million cells/kg body weight. Safety was assessed by measuring systemic hemodynamics during hUCB infusion. Infusion-related toxicity was evaluated by measuring neurologic, hepatic, renal and pulmonary function before and after infusion. Auditory function, auditory verbal language assessments and MRI with diffusion tensor imaging (DTI) were obtained before and after treatment. RESULTS: All patients survived, and there were no adverse events. No infusionrelated changes in hemodynamics occurred. No infusion-related toxicity was recorded. Five subjects experienced a reduction in auditory brainstem response (ABR) thresholds. Four of those 5 subjects also experienced an improvement in cochlear nerve latencies. Comparison of MRI with DTI sequences obtained before and after treatment revealed increased fractional anisotropy in the primary auditory cortex in three of five subjects with reduced ABR thresholds. Statistically significant (p < 0.05) reductions in ABR thresholds were identified. CONCLUSIONS: TIntravenous hUCB is feasible and safe in children with SNHL.

Electrodeless conductivity tensor imaging (CTI) using MRI: basic theory and animal experiments

The electrical conductivity is a passive material property primarily determined by concentrations of charge carriers and their mobility. The macroscopic conductivity of a biological tissue at low frequency may exhibit anisotropy related with its structural directionality. When expressed as a tensor and properly quantified, the conductivity tensor can provide diagnostic information of numerous diseases. Imaging conductivity distributions inside the human body requires probing it by externally injecting conduction currents or inducing eddy currents. At low frequency, the Faraday induction is negligible and it has been necessary in most practical cases to inject currents through surface electrodes. Here we report a novel method to reconstruct conductivity tensor images using an MRI scanner without current injection. This electrodeless method of conductivity tensor imaging (CTI) utilizes B1 mapping to recover a high-frequency isotropic conductivity image which is influenced by contents in both extracellular and intracellular spaces. Multi-b diffusion weighted imaging is then utilized to extract the effects of the extracellular space and incorporate its directional structural property. Implementing the novel CTI method in a clinical MRI scanner, we reconstructed in vivo conductivity tensor images of canine brains. Depending on the details of the implementation, it may produce conductivity contrast images for conductivity weighted imaging (CWI). Clinical applications of CTI and CWI may include imaging of tumor, ischemia, inflammation, cirrhosis, and other diseases. CTI can provide patient-specific models for source imaging, transcranial dc stimulation, deep brain stimulation, and electroporation.

The simulative study of a new probe for the dielectric measurement of anisotropic tissue in radio frequency band / 生物医学工程学杂志

In this paper, a new probe is proposed for the dielectric measurement of anisotropic tissue in radio frequency band, which could accomplish the dielectric measurement in perpendicular directions by one operation. The simulative studies are performed in the frequency range from 1-1 000 MHz in order to investigate the influence of probe dimension on the energy coupling and sensitivity of measurement. The suitable probe is designed and validated for the actual measurement in this frequency band. According to the simulation results, the energy coupling of the probe could be kept below -12 dB in the frequency range from 200-400 MHz with high sensitivity of measurement for the dielectric properties of anisotropic tissue. That indicates the new type of probe has the potential to achieve the dielectric measurement of anisotropic tissue in radio frequency band and could avoid the measurement error by multi-operations in the conventional method. This new type of probe could provide a new method for the dielectric measurement of anisotropic tissue in radio frequency band.

Mechanical Experiment and Microscopic Analysis on Anisotropic Properties of Cortical Bone / 医用生物力学

Objective To investigate the relationship between microstructure characteristics and its mechanical behavior. Methods The compression experiments on longitudinal and transverse specimens of the cortical bone from bovine femoral bone were conducted. The fracture routes of longitudinal and transverse specimens and microstructural features of fractured surfaces were observed. The effects of osteon orientation on elastic modulus and ultimate fracture strength of the bone were analyzed based on the theory of composite micromechanics. Results The compressive elastic modulus and ultimate fracture strength of longitudinal specimens were significantly greater than those of transverse specimens. The fracture routes of longitudinal specimens were along their loading direction (0°) and relatively flat, while the fracture routes of transverse specimens were relatively zigzagging, being approximately 45° with their loading direction. There were many striped structures on fractured surfaces of longitudinal specimens and the fractured surfaces were relatively smooth, while there were many annular concave and convex structures on fractured surfaces of transverse specimens and the fractured surfaces were relatively rough. Conclusions The bovine femoral bone had anisotropic mechanical properties, and its anisotropic mechanical properties were closely related to the orientation of osteons.