Steve C. N. Hui

Volumetric changes in cerebellar regions in adolescent idiopathic scoliosis compared with healthy controls

BACKGROUND CONTEXT Adolescent idiopathic scoliosis (AIS) is a three-dimensional spinal deformation that affects adolescents, especially girls. The etiopathogenesis of this disease remains uncertain, and studies have been carried out to understand its cause and related organs. Previous studies suggest that AIS is probably related to the cerebellum dysfunction, which could also be related to the abnormality in morphology of the cerebellum. PURPOSE The purpose of the study is to investigate the relationship between AIS and the volume and morphology of cerebellum. STUDY DESIGN/SETTING The study design of the cerebellum segmentation and volume quantification involved the following four steps: whole-brain normalization, cerebellum isolation, mapping with the statistical cerebellum template, and cerebellum regional volume correction. PATIENT SAMPLE In particular, high-resolution T1-weighted magnetic resonance images of 50 AIS patients with the right-thoracic curves (ie, Cobb angle ≥20°) and 40 age-matched normal controls were acquired. The exclusion criteria included history of head injury, back injury, severe headache, weakness or numbness in any limbs, urinary incontinence, nocturnal enuresis, and any space-occupying lesion found on magnetic resonance (MR) images. OUTCOME MEASURES The AIS subjects were all with moderate-to-severe curves (ie, Cobb angle ≥20°) (9 moderate and 41 severe; mean Cobb angle 48.7°, range 20°-90°). METHODS The cerebellum was parcellated to 28 regions by mapping with a well-recognized probabilistic MR cerebellum atlas. Student t test of each cerebellar region and the correction for multiple comparisons were performed. RESULTS The volumes of four regions, namely right VIIIa, right VIIIb, left X, and right X, were significantly increased by approximately 7.43% to 8.25% in the AIS compared with the control group. Statistically, the results suggested that the cerebellar volume in AIS patients was larger compared with normal controls in the cerebellum regions of prepyramidal-prebiventer and intrabiventer fissures, intrabiventer and secondary fissures, and floccular-nodular (X)-posterolateral fissure to the inferior hemispheric margin. CONCLUSIONS The functions of the affected regions involve motor control, somatosensory, working memory, language, and response to visual stimulation. We conclude that the volume difference could be compensatory consequences in the central nervous system because of the persistent effort in AIS patients to maintain the body balance given the asymmetric spine.

Variation in Anisotropy and Diffusivity along the Medulla Oblongata and the Whole Spinal Cord in Adolescent Idiopathic Scoliosis: A Pilot Study Using Diffusion Tensor Imaging

BACKGROUND AND PURPOSE: Disturbed somatosensory evoked potentials have been demonstrated in patients with adolescent idiopathic scoliosis (but this functional delay was found to originate above the C5–6 level, while the lower cord level was unaffected). Together with MR imaging observation of tonsillar ectopia and a relatively tethered cord, we hypothesized that there is disturbed mean diffusivity integrity along the spinal cord. In this study, advanced DTI was used to evaluate whether there was underlying decreased WM integrity within the brain stem and spinal cord in adolescent idiopathic scoliosis and any relationship to cerebellar tonsillar ectopia. Clinical impact on balance testing was also correlated. MATERIALS AND METHODS: Thirteen girls with adolescent idiopathic scoliosis with right thoracic curves were compared with 13 age-matched healthy girls. DTI of the brain and whole spinal cord was performed. ROIs were manually defined for the medulla oblongata and along each intervertebral segment of the cord. Mean values of fractional anisotropy and mean diffusivity were computed at the defined regions. Between-group comparisons were performed by 1-way ANOVA. RESULTS: Significantly decreased fractional anisotropy values and increased mean diffusivity values were found at the medulla oblongata and C1–2, C2–3, C3–4, and C4–5 segments in patients with adolescent idiopathic scoliosis compared with healthy subjects. No significant difference was found in the lower cord levels. Significant correlation was found between the tonsillar level and fractional anisotropy value at the C4–5 level in patients with adolescent idiopathic scoliosis only. CONCLUSIONS: The findings from this study are in agreement with previous findings showing abnormal somatosensory evoked potential readings occurring only above the C5–6 level in patients with adolescent idiopathic scoliosis; these findings might partially explain the pathophysiology of the neural pathway involved.

Application of Multimodal MR Imaging on Studying Alzheimer's Disease: A Survey.

The aim of this review is to summarize the current magnetic resonance imaging (MRI) variants applied on the studies of Alzheimers disease (AD). Experimental findings, advantages and disadvantages, and the prospect of every individual technique will be presented. MRI can be used to investigate the change of the brain in terms of volume, function, white matter track orientation and even mechanical properties and metabolic concentration.Results from volumetric and morphological analysis indicated that the hippocampus reduced by approximately 18%-24% or 3%-4% annually. Functional MRI (fMRI) detected the blood oxygen level dependent (BOLD) signaland suggested thatmedial temporal lobe (MTL) such as hippocampus and entorhinal cortex reduced at the early stage of AD, and frontal, temporal, and parietal cortices at the later stage. In diffusion tensor imaging (DTI), the white matter fiber track integrity is measured but the results are inconsistent. Besides,magnetic resonance spectroscopy (MRS), chemical shift imaging (CSI), arterial spin labeling (ASL), magnetic resonance elastography (MRE) and susceptibility weighted imaging (SWI) will also be included in this review.

Ethical principles and standards for the conduct of biomedical research and publication.

Clear and widely acceptable values and principles should be involved in scientific investigations. Scientific honesty is a fundamental aspect which leads to the overall quality of a study while misconduct involving cheating and plagiarism could cause controversy and could eventually lead to a tragedy. The aim of this letter is to promote principles and correct values to all scientists especially in research involving humans. In the field of biomedical engineering and medical physics, investigators, in many cases, initiate research related to living subjects and data. Protection of volunteers and their privacy becomes a primary and significant concern, and so conducting the research with good ethics inevitably becomes an important element for a successful study leading to valuable medical science publications. New ideas, inventions,methods, discoveries and evidence are the core contributions of research to a society. Significant contributions of research are based on the quality and impact to the society. Carrying out a good research study with integrity helps to maintain the accuracy and reliability, which is managed by quality control and assurance. Quality assurance involves the establishment of standards, the execution of procedures, verification of data and improvement of any aspect in a research. The overall quality of a research could be improved if investigators follow the standard, commit to the protocol, monitor and audit all data and financial issues. One might not find an exact definition of research integrity, butwhen your research is conducted using high moral standard in common and core values and beliefs, strict principles and guidelines,with good quality control and assurance, investigators will be on the right track. This Letter will provide specific details on the principles of research integrity and good writing mannerism.

Upright, prone, and supine spinal morphology and alignment in adolescent idiopathic scoliosis

BackgroundPatients with adolescent idiopathic scoliosis (AIS) are usually investigated by serial imaging studies during the course of treatment, some imaging involves ionizing radiation, and the radiation doses are cumulative. Few studies have addressed the correlation of spinal deformity captured by these different imaging modalities, for which patient positioning are different. To the best of our knowledge, this is the first study to compare the coronal, axial, and sagittal morphology of the scoliotic spine in three different body positions (upright, prone, and supine) and between three different imaging modalities (X-ray, CT, and MRI).MethodsSixty-two AIS patients scheduled for scoliosis surgery, and having undergone standard pre-operative work-up, were included. This work-up included upright full-spine radiographs, supine bending radiographs, supine MRI, and prone CT as is the routine in one of our institutions. In all three positions, Cobb angles, thoracic kyphosis (TK), lumbar lordosis (LL), and vertebral rotation were determined. The relationship among three positions (upright X-ray, prone CT, and supine MRI) was investigated according to the Bland-Altman test, whereas the correlation was described by the intraclass correlation coefficient (ICC).ResultsThoracic and lumbar Cobb angles correlated significantly between conventional radiographs (68° ± 15° and 44° ± 17°), prone CT (54° ± 15° and 33° ± 15°), and supine MRI (57° ± 14° and 35° ± 16°; ICC ≥0.96; P < 0.001). The thoracic and lumbar apical vertebral rotation showed a good correlation among three positions (upright, 22° ± 12° and 11° ± 13°; prone, 20° ± 9° and 8° ± 11°; supine, 16° ± 11° and 6° ± 14°; ICC ≥0.82; P < 0.001). The TK and LL correlated well among three different positions (TK 26° ± 11°, 22° ± 12°, and 17° ± 10°; P ≤ 0.004; LL 49° ± 12°, 45° ± 11°, and 44° ± 12°; P < 0.006; ICC 0.87 and 0.85).ConclusionsAlthough there is a generalized underestimation of morphological parameters of the scoliotic deformity in the supine and prone positions as compared to the upright position, a significant correlation of these parameters is still evident among different body positions by different imaging modalities. Findings of this study suggest that severity of scoliotic deformity in AIS patients can be largely represented by different imaging modalities despite the difference in body positioning.

Quantification of brown and white adipose tissue based on Gaussian mixture model using water–fat and T2* MRI in adolescents

To develop a technique for the separation and quantification of brown adipose tissue (BAT) and white adipose tissue (WAT) using fat fraction and T2* intensity based on the Gaussian mixture model (GMM).

Adaptive Distance Metric Learning for Diffusion Tensor Image Segmentation

High quality segmentation of diffusion tensor images (DTI) is of key interest in biomedical research and clinical application. In previous studies, most efforts have been made to construct predefined metrics for different DTI segmentation tasks. These methods require adequate prior knowledge and tuning parameters. To overcome these disadvantages, we proposed to automatically learn an adaptive distance metric by a graph based semi-supervised learning model for DTI segmentation. An original discriminative distance vector was first formulated by combining both geometry and orientation distances derived from diffusion tensors. The kernel metric over the original distance and labels of all voxels were then simultaneously optimized in a graph based semi-supervised learning approach. Finally, the optimization task was efficiently solved with an iterative gradient descent method to achieve the optimal solution. With our approach, an adaptive distance metric could be available for each specific segmentation task. Experiments on synthetic and real brain DTI datasets were performed to demonstrate the effectiveness and robustness of the proposed distance metric learning approach. The performance of our approach was compared with three classical metrics in the graph based semi-supervised learning framework.

Altered topological organization of cortical network in adolescent girls with idiopathic scoliosis.

Adolescent idiopathic scoliosis (AIS) is a multifactorial disease affecting approximately 1–4% of teenagers especially girls at the age of 10–16, but its etiopathogenesis remains uncertain. Previous study has revealed that the cortical thickness in AIS patients is different from that in normal controls. Cortical thickness measurements are known to be strongly correlated between regions that are axonally connected. Hence, a hypothesis is proposed to study the possibility to demonstrate abnormal structural network revealed by cortical thickness in AIS patients. The aim of the study is to investigate abnormalities in the organization of the brain cortical network in AIS patients. This study included 42 girls with severe idiopathic scoliosis (14.7±1.3 years old) and 41 age-matched normal controls (NC, 14.6±1.4 years old). The brain cortex was partitioned into 154 cortical regions based on gyral and sulcal structure. The interregional connectivity was measured as the statistical correlations between the regional mean thicknesses across the subjects. We employed the graph theoretic analysis to examine the alteration in interregional correlation, small-world efficiency, hub distribution, and regional nodal characteristics in AIS patients. We demonstrated that the cortical network of AIS patients fully preserved the small-world architecture and organization, and further verified the hemispheric asymmetry of AIS brain. Our results indicated increased central role of temporal and occipital cortex and decreased central role of limbic cortex in AIS patients compared with controls. Furthermore, decreased structural connectivity between hemispheres and increased connectivity in several cortical regions were observed. The findings of the study reveal the pattern of structural network alteration in AIS brain, and would help in understanding the mechanism and etiopathogenesis of AIS.

MRI-based morphological evidence of spinal cord tethering predicts curve progression in adolescent idiopathic scoliosis.

BACKGROUND CONTEXT Existing prognostic factors for adolescent idiopathic scoliosis (AIS) patients have focused mainly on curve, maturity, and bone-related factors. Previous studies have shown significant associations between curve severity and morphological evidences of relative shorter spinal cord tethering in AIS, and increased prevalence of abnormal somatosensory cortical-evoked potentials and low-lying cerebellar tonsil in severe AIS. Earlier evidence suggests that there might be neural morphological predictors for curve progression. PURPOSE The purpose of this study was to identify any morphological predictors associated with cord tethering, as measured by magnetic resonance imaging (MRI), for curve progression in AIS patients. STUDY DESIGN/SETTING This is a prospective cohort study. PATIENT SAMPLE A total of 81 female AIS subjects between 10 and 14 years were included, without surgical intervention during the follow-up period. OUTCOME MEASURES Magnetic resonance imaging scans of hindbrain and whole spine and areal bone mineral density (BMD) at bilateral femoral necks were performed. METHODS All AIS patients were longitudinally followed up starting from initiation of bracing beyond skeletal maturity in 6-month intervals. Clinical and radiographic data were recorded at each clinic visit. Bone mineral density and MRI measurements including ratio of spinal cord to vertebral column length, ratio of anteroposterior (AP) and transverse (TS) diameter of cord, lateral cord space (LCS) ratio, cerebellar tonsil level, and conus medullaris position were obtained at baseline. Only compliant patients with a minimum 2-year follow-up were analyzed. Adolescent idiopathic scoliosis girls were assigned into three groups according to bracing outcome: Group A, nonprogression (curvature increase of less than or equal to 5°); Group B, progression (curvature increase of greater than or equal to 6°); Group C, progression with surgery indication (Cobb angle of greater than or equal to 50° after skeletal maturity despite bracing). The predictors for curve progression were evaluated using univariate analysis and multivariate ordinal regression model. RESULTS The average duration of follow-up was 3.4 (range, 2.0-5.6) years. There were 46 girls (57%) in Group A, 19 (23%) in Group B, and 16 (20%) in Group C. No significant intergroup differences were found in spinal cord length, tonsil level, and conus position. Group C had significantly longer vertebral column length, smaller cord-vertebral length ratio, and higher AP/TS cord ratio compared with Group A, whereas LCS ratio in Group C was significantly increased compared with both Group A and Group B. In regression model, five significant independent predictors including cord-vertebral length ratio (odds ratio [OR]: 1.993 [95% confidence interval {CI}: 1.053-3.771], p=.034), LCS ratio (OR: 2.639 [95% CI: 1.128-6.174], p=.025), initial Cobb angle (OR: 1.156 [95% CI: 1.043-1.281], p=.006), menarche age (OR: 1.688 [95% CI: 1.010-2.823], p=.046), and BMD (OR: 2.960 [95% CI: 1.301-6.731], p=.010) and a marginally significant predictor namely AP/TS cord ratio (OR: 1.463 [95% CI: 0.791-2.706], p=.096) were obtained. CONCLUSIONS On baseline MRI measurement, cord-vertebral length ratio and LCS ratio are identified as new significant independent predictors for curve progression in AIS, whereas AP/TS cord ratio is suggested as a potential predictor requiring further validations. The earlier MRI parameters can be taken into accounts for prognostication of bracing outcome.

Asymmetry of the Vertebral Body and Pedicles in the True Transverse Plane in Adolescent Idiopathic Scoliosis: A CT-Based Study.

STUDY DESIGN Cross-sectional. OBJECTIVES To quantify the asymmetry of the vertebral bodies and pedicles in the true transverse plane in adolescent idiopathic scoliosis (AIS) and to compare this with normal anatomy. SUMMARY OF BACKGROUND DATA There is an ongoing debate about the existence and magnitude of the vertebral body and pedicle asymmetry in AIS and whether this is an expression of a primary growth disturbance, or secondary to asymmetrical loading. METHODS Vertebral body asymmetry, defined as left-right overlap of the vertebral endplates (ie, 100%: perfect symmetry, 0%: complete asymmetry) was evaluated in the true transverse plane on CT scans of 77 AIS patients and 32 non-scoliotic controls. Additionally, the pedicle width, length, and angle and the length of the ideal screw trajectory were calculated. RESULTS Scoliotic vertebrae were on average more asymmetric than controls (thoracic: AIS 96.0% vs. controls 96.4%; p = .005, lumbar: 95.8% vs. 97.2%; p < .001) and more pronounced around the thoracic apex (95.8%) than at the end vertebrae (96.3%; p = .031). In the thoracic apex; the concave pedicle was thinner (4.5 vs. 5.4 mm; p < .001) and longer (20.9 vs. 17.9 mm; p < .001), the length of the ideal screw trajectory was longer (43.0 vs. 37.3 mm; p < .001), and the transverse pedicle angle was greater (12.3° vs. 5.7°; p < .001) than the convex one. The axial rotation showed no clear correlation with the asymmetry. CONCLUSIONS Even in non-scoliotic controls is a degree of vertebral body and pedicle asymmetry, but scoliotic vertebrae showed slightly more asymmetry, mostly around the thoracic apex. In contrast to the existing literature, there is no major asymmetry in the true transverse plane in AIS and no uniform relation between the axial rotation and vertebral asymmetry could be observed in these moderate to severe patients, suggesting that asymmetrical vertebral growth does not initiate rotation, but rather follows it as a secondary phenomenon. LEVEL OF EVIDENCE Level 4.STUDY DESIGN Cross-sectional. OBJECTIVES To quantify the asymmetry of the vertebral bodies and pedicles in the true transverse plane in adolescent idiopathic scoliosis (AIS) and to compare this with normal anatomy. There is an ongoing debate about the existence and magnitude of the vertebral body and pedicle asymmetry in AIS and whether this is an expression of a primary growth disturbance, or secondary to asymmetrical loading. METHODS Vertebral body asymmetry, defined as left-right overlap of the vertebral endplates (ie, 100%: perfect symmetry, 0%: complete asymmetry) was evaluated in the true transverse plane on CT scans of 77 AIS patients and 32 non-scoliotic controls. Additionally, the pedicle width, length, and angle and the length of the ideal screw trajectory were calculated. RESULTS Scoliotic vertebrae were on average more asymmetric than controls (thoracic: AIS 96.0% vs. controls 96.4%; p =.005, lumbar: 95.8% vs. 97.2%; p <.001) and more pronounced around the thoracic apex (95.8%) than at the end vertebrae (96.3%; p =.031). In the thoracic apex; the concave pedicle was thinner (4.5 vs. 5.4 mm; p <.001) and longer (20.9 vs. 17.9 mm; p <.001), the length of the ideal screw trajectory was longer (43.0 vs. 37.3 mm; p <.001), and the transverse pedicle angle was greater (12.3° vs. 5.7°; p <.001) than the convex one. The axial rotation showed no clear correlation with the asymmetry. CONCLUSIONS Even in non-scoliotic controls is a degree of vertebral body and pedicle asymmetry, but scoliotic vertebrae showed slightly more asymmetry, mostly around the thoracic apex. In contrast to the existing literature, there is no major asymmetry in the true transverse plane in AIS and no uniform relation between the axial rotation and vertebral asymmetry could be observed in these moderate to severe patients, suggesting that asymmetrical vertebral growth does not initiate rotation, but rather follows it as a secondary phenomenon. LEVEL OF EVIDENCE Level 4.