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PubMed2002

Cortical thickness: an early morphological marker of atherosclerotic renal disease.

BACKGROUND: Although kidney size is still the most commonly used morphological parameter, it is not sensitive enough for early detection of atherosclerotic renal disease (ARD). The purpose of this work was to evaluate morphological abnormalities on both post-stenotic and contralateral kidneys, by using spiral computed tomography angiography (CTA). METHODS: Spiral CTA was performed in 49 hypertensive patients. Renal diameters, renal length, and cortical thickness were measured in 26 post-stenotic kidneys, 26 contralateral kidneys and 46 control kidneys. Mean cortical thickness, cortical area, and medullary length were calculated. RESULTS: The right and left control kidneys were of comparable morphology. The post-stenotic kidneys showed significant cortical atrophy. The contralateral kidneys also underwent cortical disease, as judged by comparison with control kidneys. A threshold of 800 mm2 was identified for the cortical area that allowed us to distinguish control kidneys from post-stenotic kidneys. Similarly, a threshold of 8 mm was identified for mean cortical thickness. Renal length was still within normal range in all kidney groups. The measurement of superior pole segments appeared to be more sensitive than measurement at other locations for identifying significant intrarenal lesions. There was no significant correlation between clinical and morphological parameters. CONCLUSIONS: These results suggest that cortical parameters are more sensitive for early diagnosis of ARD than kidney size. Cortical atrophy should be a useful marker for guidance for revascularization.

Adult↗

PubMed2005

Cortical thickness analysis examined through power analysis and a population simulation.

We have previously developed a procedure for measuring the thickness of cerebral cortex over the whole brain using 3-D MRI data and a fully automated surface-extraction (ASP) algorithm. This paper examines the precision of this algorithm, its optimal performance parameters, and the sensitivity of the method to subtle, focal changes in cortical thickness. The precision of cortical thickness measurements was studied using a simulated population study and single subject reproducibility metrics. Cortical thickness was shown to be a reliable method, reaching a sensitivity (probability of a true-positive) of 0.93. Six different cortical thickness metrics were compared. The simplest and most precise method measures the distance between corresponding vertices from the white matter to the gray matter surface. Given two groups of 25 subjects, a 0.6-mm (15%) change in thickness can be recovered after blurring with a 3-D Gaussian kernel (full-width half max = 30 mm). Smoothing across the 2-D surface manifold also improves precision; in this experiment, the optimal kernel size was 30 mm.

Algorithms↗

PubMed1980

A comparative estimation of the combined cortical thickness of various bone sites.

Measurement of the cortical thickness of long bones is the best method of quantitatively diagnosing osteoporosis. Combined cortical thickness (CCT) is as good as, or better than more complicated indices. In osteoporosis studies, the problem lies in finding a physiologically consistent bone site . The CCT of the lower shaft of the humerus showed the lowest coefficient of variation in this homogeneous female population and the addition of both CCT values further reduced the variability. It is suggested that the humeral site is significantly superior to the metacarpal sites and that the variability is small enough to give clinically useful information in the diagnosis of osteoporosis.

Adult↗

PubMed2001

Measurement of cortical thickness using an automated 3-D algorithm: a validation study.

A validation study was conducted to assess the accuracy of the algorithm developed by MacDonald et al. (1999) for measuring cortical thickness. This algorithm automatically determines the cortical thickness by 3-D extraction of the inner and outer surfaces of the cerebral cortex from an MRI scan. A manual method of tagging the grey-csf and grey-white interface was used on 20 regions (10 cortical areas found in each hemisphere) in 40 MRIs of the brain to validate the algorithm. The regions were chosen throughout the cortex to get broad assessment of the algorithm's performance. Accuracy was determined by an anatomist tagging the csf-grey and grey-white borders of selected gyri and by allowing the algorithm to determine the csf-grey and grey-white borders and the corresponding cortical thickness of the same region. Results from the manual and automatic methods were statistically compared using overall ANOVA and paired t tests for each region. The manual and automatic methods were in agreement for all but 4 of the 20 regions tested. The four regions where there were significant differences between the two methods were the insula left and right, the right cuneus, and the right parahippocampus. We conclude that the automatic algorithm is valid for most of the cortex and provides a viable alternative to manual methods of determining cortical thickness in vivo. However, caution should be taken when measuring the regions mentioned previously where the results of the algorithm can be biased by surrounding grey structures.

Adult↗

PubMed1978

Metacarpal cortical thickness in uremic patients on regular hemodialysis.

Metacarpal cortical thickness was measured in 83 patients with chronic renal failure undergoing periodic hemodialysis. Patients were dialyzed twice weekly, 8--9h per session, with a calcium concentration in dialysate of 6.5 mg/dl. Supplements of calcium, vitamin D (5,000 I.U. a day), steroid anabolic hormones, and aluminium hydroxyde were administered to all patients. They were on a normal protein intake and unrestricted physical activity. The results show that the young males have a reduction in cortical thickness as compared to age-matched controls, and that there is a progressive loss in cortical width as the length of dialysis increases. This bone loss is statistically significant in males during their first 18 months of dialysis.

Adolescent↗

PubMed1995

Radial and ulnar cortical thickness of the second metacarpal.

Differential bone mass at various skeletal sites, which may be due to mechanical stress exerted by the muscles attached to the bone, has been demonstrated for athletes who exert one limb more than the other. The question arises as to whether this bilateral asymmetry extends to the two sides of the same bone with different muscular attachments. The objectives of this study were to ascertain whether the radial and ulnar sides of the second metacarpal have similar cortical thickness and determine if bone mass decreases equally with age on the radial and ulnar sides. Hand-wrist radiographs were obtained from 201 male and 191 female Caucasian participants of the Baltimore Longitudinal Study of Aging. Differences between radial and ulnar cortical thickness within age groups were tested with Student's t-test and between age groups using analysis of variance. RAdial cortical thickness of the second metacarpal was found to be 11-12% greater in men and 10-12% greater in women than ulnar cortical thickness in both the left and right hands. Age-related changes in radial cortical thickness were evident in both sexes. In men, radial cortex decreased linearly from age 40 to 89. For women, there was a sharp decline in radial thickness from age 50 to age 60. Ulnar cortical thickness declined from age 50 to 60 for women only. Muscle attachment along the radial length of the second metacarpal may influence the accumulation of bone mass on the radial side at younger ages while muscle disuse may precipitate the loss of bone preferentially from the radial side.

Adult↗

PubMed2004

Cortical thickness in a case of congenital unilateral perisylvian syndrome.

In congenital perisylvian syndrome, there is polymicrogyric cortex distributed in variable extensions around the sylvian fissure. Unilateral cases usually present with congenital hemiparesis, while bilateral cases have pseudobulbar paralysis of the oropharingoglossal region. Both unilateral and bilateral cases have a high rate of epilepsy. Polymicrogyric cortex is characterized by too many small convolutions. Often there are no intervening sulci, and almost no white matter can be seen under them. On MRI they appear to have increased thickness. Bilateral and symmetric polimycrogiria can be hard to recognize on standard MRIs. Accurate and automated methods for measuring the thickness of cerebral cortex are available. They have mainly been used to study a variety of disorders with diminished cortical thickness. We studied a case of right perisylvian polymicrogyria, who presented in adult life with epilepsy and had a normal neurological exam. Fischl and Dale's automated cortical thickness analysis rendered a very clear picture of increased cortical thickness with values up to 9 mm in the affected areas (normal cortical thickness varies between 1 and 4.5 mm). The thickest areas were seen over grossly abnormal gyri on the reconstructed cerebral cortex. On MEG he presented a prominent and monotonous 9 Hz activity that was located within the limits of a thick gyrus. There was a significant difference of thickness between homologous hemispheric areas. To our surprise some areas of the left hemisphere also appeared to have increased thickness, raising the question of a bilateral asymmetric case.

Cerebral Cortex↗

PubMed2000

Three-dimensional mapping of cortical thickness using Laplace's equation.

We present a novel, computerized method of examining cerebral cortical thickness. The normal cortex varies in thickness from 2 to 4 mm, reflecting the morphology of neuronal sublayers. Cortical pathologies often manifest abnormal variations in thickness, with examples of Alzheimer's disease and cortical dysplasia as thin and thick cortex, respectively. Radiologically, images are 2-D slices through a highly convoluted 3-D object. Depending on the relative orientation of the slices with respect to the object, it is impossible to deduce abnormal cortical thickness without additional information from neighboring slices. We approach the problem by applying Laplace's Equation (V2psi = 0) from mathematical physics. The volume of the cortex is represented as the domain for the solution of the differential equation, with separate boundary conditions at the gray-white junction and the gray-CSF junction. Normalized gradients of psi form a vector field, representing tangent vectors along field lines connecting both boundaries. We define the cortical thickness at any point in the cortex to be the pathlength along such lines. Key advantages of this method are that it is fully three-dimensional, and the thickness is uniquely defined for any point in the cortex. We present graphical results that map cortical thickness everywhere in a normal brain. Results show global variations in cortical thickness consistent with known neuroanatomy. The application of this technique to visualization of cortical thickness in brains with known pathology has broad clinical implications.

Algorithms↗

PubMed2003

The cortical thickness of the proximal humeral diaphysis predicts bone mineral density of the proximal humerus.

The operative treatment of fractures of the proximal humerus can be complicated by poor bone quality. Our aim was to evaluate a new method which allows prediction of the bone quality of the proximal humerus from radiographs. Anteroposterior radiographs were taken of 19 human cadaver humeri. The cortical thickness was measured at two levels of the proximal humeral diaphysis. The bone mineral density (BMD) was determined for the humeral head (HH), the surgical neck (SN), the greater tuberosity (GT) and lesser tuberosity (LT) using dual-energy x-ray absorptiometry. The mean cortical thickness was 4.4 +/- 1.0 mm. Specimens aged 70 years or less had a significantly higher cortical thickness than those aged over 70 years. A significant positive correlation was found between cortical thickness and the BMD for each region of interest. The cortical thickness of the proximal diaphysis is a reliable predictor of the bone quality of the proximal humerus.

Absorptiometry, Photon↗

PubMed2006

Pattern classification using principal components of cortical thickness and its discriminative pattern in schizophrenia.

We proposed pattern classification based on principal components of cortical thickness between schizophrenic patients and healthy controls, which was trained using a leave-one-out cross-validation. The cortical thickness was measured by calculating the Euclidean distance between linked vertices on the inner and outer cortical surfaces. Principal component analysis was applied to each lobe for practical computational issues and stability of principal components. And, discriminative patterns derived at every vertex in the original feature space with respect to support vector machine were analyzed with definitive findings of brain abnormalities in schizophrenia for establishing practical confidence. It was simulated with 50 randomly selected validation set for the generalization and the average accuracy of classification was reported. This study showed that some principal components might be more useful than others for classification, but not necessarily matching the ordering of the variance amounts they explained. In particular, 40-70 principal components rearranged by a simple two-sample t-test which ranked the effectiveness of features were used for the best mean accuracy of simulated classification (frontal: (left(%)|right(%))=91.07|88.80, parietal: 91.40|91.53, temporal: 93.60|91.47, occipital: 88.80|91.60). And, discriminative power appeared more spatially diffused bilaterally in the several regions, especially precentral, postcentral, superior frontal and temporal, cingulate and parahippocampal gyri. Since our results of discriminative patterns derived from classifier were consistent with a previous morphological analysis of schizophrenia, it can be said that the cortical thickness is a reliable feature for pattern classification and the potential benefits of such diagnostic tools are enhanced by our finding.

Adult↗

PubMed1982

Inhibition of calcium absorption in the cortical thick ascending limb of Henle's loop by furosemide.

The effect of luminal furosemide on calcium transport across the cortical thick ascending limb of Henle's loop was studied. Cortical thick ascending limbs were dissected from rabbit kidneys and perfused in vitro. Calcium concentrations in perfused and collected tubule fluids were measured by continuous-flow microcolorimetry. Tubules were perfused at slow flow rates and parathyroid hormone was added to the bathing solution to maximize the difference between perfusate and collectate calcium concentrations. Furosemide simultaneously and reversibly inhibited the lumen-positive transepithelial voltage and calcium absorption. In the presence of furosemide perfusate-minus-collectate calcium concentration difference was smallest under conditions that minimized the residual transepithelial voltage. It was concluded furosemide inhibits calcium absorption in the cortical thick ascending limb of Henle's loop by reducing the lumen-positive transepithelial voltage that drives passive calcium ion transport.

Absorption↗

PubMed2003

Resident's ridge: assessing the cortical thickness of the lateral wall and roof of the intercondylar notch.

PURPOSE: The purpose of this study was to better delineate the anatomy of "resident's ridge," a term coined by William Clancy Jr., M.D., to describe the raised bony landmark commonly visualized just anterior to the femoral attachment of the anterior cruciate ligament (ACL). This landmark can mislead the novice surgeon into misplacing the femoral tunnel of ACL reconstructions. TYPE OF STUDY: Cadaveric anatomic study. METHODS: Ten human distal femurs harvested from embalmed specimens were fixed, sectioned, and analyzed for the presence and descriptive characteristics of resident's ridge. A single, blinded examiner evaluated slope, cortical thickness at 4 sites, and the presence or absence of a distinct ridge relative to the attachment of the ACL. RESULTS: A defined resident's ridge was present in 9 of 10 specimens. This was directly associated with a change in slope of the intracondylar roof in the same 9 of 10 patients. The mean cortical thickness at the ACL attachment site was 1.6 mm. This was thicker than at resident's ridge (mean, 0.90 mm), the cartilage-intercondylar notch junction (mean, 0.96 mm), and a point midway between the ACL attachment and the cartilage-intercondylar notch junction (mean, 0.90 mm). CONCLUSIONS: The phenomenon of "resident's ridge" is accounted for by a distinctive change in slope of the femoral notch roof that occurs just anterior to the femoral attachment of the ACL. The density change apparent at the time of notchplasty is probably caused by the transition between normal cortical thickness just anterior to the ACL and the cortical thickness of the ACL attachment. No distinctive increased cortical thickness can be identified as "resident's ridge."

Anterior Cruciate Ligament↗

PubMed1977

Cortical thickness measurements and photon absorptiometry for determination of bone quantity.

Reproducibility of estimates of cortical bone quantity in the appendicular skeleton by two methods was studied in healthy individuals and patients undergoing long-term hemodialysis. Repeated measurements of cortical thickness (CT) at the midpoint of the second metacarpal were taken from single radiographs of both hands by two independent observers. Repeated measurements by the same observer were more reproducible and the degree of reproducibility was far greater in healthy subjects than in dialysis patients. Repeated measurements were made of bone mineral content (BMC) and bone width (W) of the distal radius by photon absorptiometry. Repeated BMC/W determinations were highly reproducible in both healthy subjects and dialysis patients. High correlation was found between BMC and cross-sectional cortical area and between both simple cortical thickness and cortical area/width. Thus the photon absorptiometric technique is superior for the serial monitoring of bone quantity, particularly in patients with uremic osteodystrophy, but results obtained by the two methods in group studies should be comparable.

Adult↗

PubMed2006

Reliability of MRI-derived measurements of human cerebral cortical thickness: the effects of field strength, scanner upgrade and manufacturer.

In vivo MRI-derived measurements of human cerebral cortex thickness are providing novel insights into normal and abnormal neuroanatomy, but little is known about their reliability. We investigated how the reliability of cortical thickness measurements is affected by MRI instrument-related factors, including scanner field strength, manufacturer, upgrade and pulse sequence. Several data processing factors were also studied. Two test-retest data sets were analyzed: 1) 15 healthy older subjects scanned four times at 2-week intervals on three scanners; 2) 5 subjects scanned before and after a major scanner upgrade. Within-scanner variability of global cortical thickness measurements was <0.03 mm, and the point-wise standard deviation of measurement error was approximately 0.12 mm. Variability was 0.15 mm and 0.17 mm in average, respectively, for cross-scanner (Siemens/GE) and cross-field strength (1.5 T/3 T) comparisons. Scanner upgrade did not increase variability nor introduce bias. Measurements across field strength, however, were slightly biased (thicker at 3 T). The number of (single vs. multiple averaged) acquisitions had a negligible effect on reliability, but the use of a different pulse sequence had a larger impact, as did different parameters employed in data processing. Sample size estimates indicate that regional cortical thickness difference of 0.2 mm between two different groups could be identified with as few as 7 subjects per group, and a difference of 0.1 mm could be detected with 26 subjects per group. These results demonstrate that MRI-derived cortical thickness measures are highly reliable when MRI instrument and data processing factors are controlled but that it is important to consider these factors in the design of multi-site or longitudinal studies, such as clinical drug trials.

Aged↗

PubMed2003

Morphology-based cortical thickness estimation.

We describe a new approach to estimating the cortical thickness of human brains using magnetic resonance imaging data. Our algorithm is part of a processing chain consisting of a brain segmentation (skull stripping), as well as white and grey matter segmentation procedures. In this paper, only the grey matter segmentation together with the cortical thickness estimation is described. In contrast to many existing methods, our estimation method is voxel-based and does not use any surface meshes. While this fact poses a principal limit on the accuracy that can be achieved by our method, it offers tremendous advantages with respect to practical applicability. In particular, it is applicable to data sets showing severe cortical atrophies that involve areas of high curvature and extremely thin gyral stalks. In contrast to many other methods, it is entirely automatic and very fast with computation times of a few minutes. Our method has been used in two clinical studies involving a total of 27 patients and 23 healthy subjects.

Algorithms↗

PubMed2006

Gender effects on cortical thickness and the influence of scaling.

Using magnetic resonance imaging and well-validated computational cortical pattern matching methods in a large and well-matched sample of healthy subjects (n = 60), we analyzed the regional specificity of gender-related cortical thickness differences across the lateral and medial cortices at submillimeter resolution. To establish the influences of brain size correction on gender effects, comparisons were performed with and without applying affine transformations to scale each image volume to a template. We revealed significantly greater cortical thickness in women compared to men, after correcting for individual differences in brain size, while no significant regional thickness increases were observed in males. The pattern and direction of the results were similar without brain size correction, although effects were less pronounced and a small cortical region in the lateral temporal lobes showed greater thickness in males. Our gender-specific findings support a dimorphic organization in male and female brains that appears to involve the architecture of the cortical mantle and that manifests as increased thickness in female brains. This sexual dimorphism favoring women, even without correcting for brain size, may have functional significance and possibly account for gender-specific abilities and/or behavioral differences between sexes.

Adult↗

PubMed2006

Regional cortical thickness matters in recall after months more than minutes.

The aim of this study was to determine the role of regional cortical thickness in recall of verbal material over an extended time period. MRI scans of healthy adults of varying ages were obtained. Two scans were averaged per person to achieve high spatial resolution, and a semi-automated method for continuous measurement of thickness across the entire cortical mantle was employed. Verbal memory tests assessing recall after 5 min, 30 min, and a mean interval of 83 days were administered. A general linear model (GLM) of the effects of thickness at each vertex on the different memory indices was computed, controlling for gender, age, IQ, and intracranial volume. These analyses were repeated with hippocampal volume as an additional variable to be controlled for, to assess to which extent effects of cortical thickness were independent of hippocampal size. Minute effects of cortical thickness were observed with regard to shorter time intervals (5 and 30 min). However, even when controlling for the effects of hippocampal volume, higher recall across months was associated with thicker cortex of distinct areas including parts of the gyrus rectus, the middle frontal gyrus, the parieto-occipital sulcus and the lingual gyrus of both hemispheres. In addition, hemisphere-specific associations were found in parts of the right temporal and parietal lobe as well as parts of the left precuneus. This supports a unique and critical role of the thickness of distinct cortical areas in recall after months, more than after minutes.

Adult↗

PubMed2006

Measurement of cortical thickness in 3D brain MRI data: validation of the Laplacian method.

OBJECTIVES: We aimed to determine the precision of the Laplacian approach for cortical thickness measurement due to changes in computational and acquisition parameters. We compared these results to two other methods widely used in clinical research using brain MRI data. MATERIALS AND METHODS: Brain MRI scans were obtained in 10 healthy adults using three different sets of acquisition parameters. The first and the second acquisitions used different slice thickness but the same head position. The third scan was performed after head repositioning. We measured cerebral cortical thickness in all brain segmentations using three thickness methods: Laplacian, nearest distance, and the orthogonal projection. RESULTS: The Laplacian method demonstrated the least variability with regard to the effect of interchange of boundaries, slice thickness, and repositioning of the head, compared with the other two methods. CONCLUSION: The Laplacian method is the most precise and reliable tool for in vivo cortical thickness measurement using brain MRI data.

Adult↗