Association of bone mineral density with bone texture attributes extracted using routine magnetic resonance imaging

OBJECTIVE: Dual-energy X-ray absorptiometry (DXA)-derived bone mineral density (BMD) often fails to predict fragility fractures. Quantitative textural analysis using magnetic resonance imaging (MRI) may potentially yield useful radiomic features to predict fractures. We aimed to investigate the correlation between BMD and texture attributes (TAs) extracted from MRI scans and the interobserver reproducibility of the analysis. METHODS: Forty-nine volunteers underwent lumbar spine 1.5-T MRI and DXA. Three-dimensional (3-D) gray-level co-occurrence matrices were measured from routine sagittal T2 fast spin-echo images using the IBEX software. Twenty-two TAs were extracted from 3-D segmented L3 vertebrae. The estimated concordance coefficient was calculated using linear regression analysis. A Pearson correlation coefficient analysis was performed to evaluate the correlation between BMD and the TAs. Interobserver reproducibility was assessed with the concordance coefficient described by Lin. RESULTS: The results revealed a fair-to-moderate significant correlation between BMD and 13 TAs (r=−0.20 to 0.39; p<0.05). Eight TAs (autocorrelation, energy, homogeneity 1, homogeneity 1.1, maximum probability, sum average, sum variance, and inverse difference normalized) negatively correlated with BMD (r=−0.20 to −0.38; p<0.05), whereas five TAs (dissimilarity, difference entropy, entropy, sum entropy, and information measure corr 1) positively correlated with BMD (r=0.29-0.39; p<0.05). The interobserver agreement was almost perfect for all significant TAs (95% confidence interval, 0.92-1.00; p<0.05). CONCLUSION: Specific TAs could be reliably extracted from routine MRI and correlated with BMD. Our results encourage future evaluation of the potential usefulness of quantitative texture measurements from MRI scans for predicting fragility fractures.

Anatomic and neuropsychological findings in low-educated cognitively intact elderly from a Brazilian cohort / Achados Anatômicos e Neuropsicológicos de Idosos Cognitivamente Saudáveis com Baixa Escolaridade em uma Coorte Brasileira

ABSTRACT In elderly individuals, low educational level may represent a risk factor for the development of dementia and a proxy of cognitive reserve. Objective: This study examined the cognitive and neuroanatomic correlates of high versus low educational levels in cognitively healthy community-dwelling older adults in Brazil. Methods: Fifty-three older adults (mean age: 68±5.3 years) were divided into a "low education" group [LE; 1-4 years of education (N=33)] and "high education" group [HE; >11 years of education (N=20)]. Both groups completed a comprehensive neuropsychological battery and underwent in vivo structural MRI close to the time of testing. Results: Higher educational level increased the chance of having better scores on neuropsychological tests, including verbal and visual delayed recall of information, verbal learning, category fluency, global cognition, and vocabulary. Better scores on these tests were observed in the HE group relative to the LE group. Despite this, there were no group differences between MRI measures. Conclusion: Older adults with higher educational levels showed better scores on neuropsychological measures of cognition, highlighting the need for education-adjusted norms in developing countries. Given the absence of differences in structural anatomy between the groups, these findings appear to be best explained by theories of cognitive reserve.

RESUMO Sabe-se que baixos níveis de educação são comuns em países em desenvolvimento. Em indivíduos idosos, em particular, baixos níveis de educação podem representar um fator de risco para o desenvolvimento de demência. Objetivo: Este estudo examina os correlatos cognitivos e neuroanatômicos de escolaridade alta versus baixa, em idosos cognitivamente saudáveis,vivendo em comunidade no Brasil. Métodos: Cinquenta e três idosos (média de idade: 68±5,3) foram divididos em um grupo de "baixa escolaridade" [LE; 1-4 anos de escolaridade (N=33)] e um grupo de "alta escolaridade" [HE; >11 anos de escolaridade (N=20)]. Ambos os grupos completaram uma bateria neuropsicológica abrangente e foram submetidos à RM estrutural in vivo próximo à testagem. Resultados: O nível educacional aumentou a chance de se obter melhores pontuações em testes neuropsicológicos, incluindo evocação verbal e visual da informação, aprendizagem verbal, fluência de categoria, cognição global e vocabulário. Escores mais altos foram encontrados no grupo HE, em detrimento do LE. Apesar disso, não houve diferenças entre os grupos nas medidas de ressonância magnética in vivo. Conclusão: Idosos com maiores níveis de escolaridade apresentaram melhores pontuações nas medidas neuropsicológicas da cognição, destacando a necessidade de normas ajustadas à educação nos países em desenvolvimento. Não havendo diferenças na anatomia estrutural entre os grupos, os achados parecem ser melhor explicados pelas teorias da "reserva cognitiva".

Multimodal quantitative magnetic resonance imaging analysis with individualized postprocessing in patients with drug-resistant focal epilepsy and conventional visual inspection negative for epileptogenic lesions

OBJECTIVES: Approximately one-third of candidates for epilepsy surgery have no visible abnormalities on conventional magnetic resonance imaging. This is extremely discouraging, as these patients have a less favorable prognosis. We aimed to evaluate the utility of quantitative magnetic resonance imaging in patients with drug-resistant neocortical focal epilepsy and negative imaging. METHODS: A prospective study including 46 patients evaluated through individualized postprocessing of five quantitative measures: cortical thickness, white and gray matter junction signal, relaxation rate, magnetization transfer ratio, and mean diffusivity. Scalp video-electroencephalography was used to suggest the epileptogenic zone. A volumetric fluid-attenuated inversion recovery sequence was performed to aid visual inspection. A critical assessment of follow-up was also conducted throughout the study. RESULTS: In the subgroup classified as having an epileptogenic zone, individualized postprocessing detected abnormalities within the region of electroclinical origin in 9.7% to 31.0% of patients. Abnormalities outside the epileptogenic zone were more frequent, up to 51.7%. In five patients initially included with negative imaging, an epileptogenic structural abnormality was identified when a new visual magnetic resonance imaging inspection was guided by information gleaned from postprocessing. In three patients, epileptogenic lesions were detected after visual evaluation with volumetric fluid-attenuated sequence guided by video electroencephalography. CONCLUSION: Although quantitative magnetic resonance imaging analyses may suggest hidden structural lesions, caution is warranted because of the apparent low specificity of these findings for the epileptogenic zone. Conversely, these methods can be used to prevent visible lesions from being ignored, even in referral centers. In parallel, we need to highlight the positive contribution of the volumetric fluid-attenuated sequence.

Quantitative MRI data in Multiple Sclerosis patients: a pattern recognition study

Abstract Introduction Multiple Sclerosis (MS) is a neurodegenerative disease characterized by inflammatory demyelination in the central nervous system. Quantitative Magnetic Resonance Imaging (qMRI) enables a detailed characterization of brain tissue, but generates a large number of numerical results. In this study, we elucidated the main qMRI techniques and the brain regions that allow the identification of MS patients from neuroimaging data and pattern recognition techniques. Methods The data came from the combination of computational tools of image processing and neuroimaging acquired in a 3 Tesla scanner using different techniques: Diffusion, T2 Relaxometry, Magnetization Transfer Ratio (MTR) and Structural Morphometry. Data from 126 brain regions of 203 healthy individuals and 124 MS patients were separated into two groups and processed in a data-mining program using the k-nearest-neighbor (KNN) algorithm. Results The most relevant anatomical structures in the classification procedure were: corpus callosum, precuneus, left cerebellum and fusiform. Among the quantitative techniques the most relevant was the MTR, being indicated for longitudinal studies of this disease. KNN with 5 neighbors and pre-selected attributes had a better performance with an area under the ROC curve (97.3%) and accuracy (95.7%). A restricted classification considering only brain regions previously reported in the literature as affected by MS brought slightly lower scores, area: 97.1% and accuracy: 93.2%. Conclusion The use of standard recognition techniques from quantitative neuroimaging techniques has confirmed that the white matter of the brain is the most affected tissue by MS following a global pattern with greater involvement of the left hemisphere.

Enhancing quality in Diffusion Tensor Imaging with anisotropic anomalous diffusion filter

Abstract Introduction: Diffusion tensor imaging (DTI) is an important medical imaging modality that has been useful to the study of microstructural changes in neurological diseases. However, the image noise level is a major practical limitation, in which one simple solution could be the average signal from a sequential acquisition. Nevertheless, this approach is time-consuming and is not often applied in the clinical routine. In this study, we aim to evaluate the anisotropic anomalous diffusion (AAD) filter in order to improve the general image quality of DTI. Methods A group of 20 healthy subjects with DTI data acquired (3T MR scanner) with different numbers of averages (N=1,2,4,6,8, and 16), where they were submitted to 2-D AAD and conventional anisotropic diffusion filters. The Relative Mean Error (RME), Structural Similarity Index (SSIM), Coefficient of Variation (CV) and tractography reconstruction were evaluated on Fractional Anisotropy (FA) and Apparent Diffusion Coefficient (ADC) maps. Results The results point to an improvement of up to 30% of CV, RME, and SSIM for the AAD filter, while up to 14% was found for the conventional AD filter (p<0.05). The tractography revealed a better estimative in fiber counting, where the AAD filter resulted in less FA variability. Furthermore, the AAD filter showed a quality improvement similar to a higher average approach, i.e. achieving an image quality equivalent to what was seen in two additional acquisitions. Conclusions In general, the AAD filter showed robustness in noise attenuation and global image quality improvement even in DTI images with high noise level.

Pattern recognition of abscesses and brain tumors through MR spectroscopy: Comparison of experimental conditions and radiological findings

Abstract Introduction The interpretation of brain tumors and abscesses MR spectra is complex and subjective. In clinical practice, different experimental conditions such as field strength or echo time (TE) reveal different metabolite information. Our study aims to show in which scenarios magnetic resonance spectroscopy can differentiate among brain tumors, normal tissue and abscesses using classification algorithms. Methods Pairwise classification between abscesses, brain tumor classes, and healthy subjects tissue spectra was performed, also the multiclass classification between meningiomas, grade I-II-III gliomas, and glioblastomas and metastases, in 1.5T short TE (n = 195), 1.5T long TE (n = 231) and 3.0T long TE (n = 59) point resolved spectroscopy setups, using LCModel metabolite concentration as input to classifiers. Results Areas under the curve of the Receiver Operating Characteristic above 0.9 were obtained for the classification between abscesses and all classes except glioblastomas, reaching 0.947 when classifying against metastases, grade I-II gliomas and glioblastomas (0.980), meningiomas and glioblastomas (0.956), grade I-II gliomas and metastases (0.989), meningiomas and metastases (0.990), and between healthy tissue and all other classes in both conditions except for anaplastic astrocytomas in short TE 1.5T setup. When the multiclass classification agrees with radiological diagnosis the accuracy reaches 96.8% for short TE and 98.9% for long TE. Conclusions The results in the three conditions were similar, highlighting comparable quality, robust quantification and good regularization and flexibility in either algorithm. Multiclass classification provides useful information to the radiologist. These findings show the potential of the development of decision support systems as well as tools for the accompaniment of treatments.

Does a small size needle puncture cause intervertebral disc changes?

PURPOSE:Small size needles have been regularly used for intradiscal injection of innocuous/potential therapeutic compounds in experimental conditions, but also in clinic procedures, such as discography. Our aim was to investigate if a 30-gauge needle could trigger observable changes on intact intervertebral discs. We compared these effects to those induced by a large size needle (21-gauge), a well-known intervertebral disc degenerative model based on needle puncture.METHODS:Coccygeal intervertebral discs (Co8-9) of adult male Wistar rats were punctured with a 21-gauge needle, while the coccygeal levels Co7-8 and Co9-10 remained intact. The 30-gauge needle was used to inject a safe volume of saline (2 µl) on both intact (Co9-10) and punctured (Co8-9) discs. MRI and histological score were performed at 2, 15 and 42 days after procedure.RESULTS: MRI analyses revealed significant reduction on signal intensity of 21-gauge punctured discs. Intact discs which received a saline injection through a 30-gauge needle also revealed significant alterations in the MRI signal when compared with control discs. No histological changes were observed in the intact saline injected discs at any time analyzed.CONCLUSION: Since significant intervertebral image changes were observed with a 30-gauge needle, cautious interpretation of the pharmacological inoculation findings is required.

Susceptibility weighted imaging: differentiating between calcification and hemosiderin / Imagem ponderada em suscetibilidade magnética: diferenciando calcificação de hemossiderina

Objective: To present a detailed explanation on the processing of magnetic susceptibility weighted imaging (SWI), demonstrating the effects of echo time and sensitive mask on the differentiation between calcification and hemosiderin. Materials and Methods: Computed tomography and magnetic resonance (magnitude and phase) images of six patients (age range 41– 54 years; four men) were retrospectively selected. The SWI images processing was performed using the Matlab’s own routine. Results: Four out of the six patients showed calcifications at computed tomography images and their SWI images demonstrated hyperintense signal at the calcification regions. The other patients did not show any calcifications at computed tomography, and SWI revealed the presence of hemosiderin deposits with hypointense signal. Conclusion: The selection of echo time and of the mask may change all the information on SWI images, and compromise the diagnostic reliability. Amongst the possible masks, the authors highlight that the sigmoid mask allows for contrasting calcifications and hemosiderin on a single SWI image. .

Objetivo: Expor em detalhes o processamento da imagem ponderada em suscetibilidade magnética (susceptibility weighted imaging – SWI), destacando o efeito da escolha do tempo de eco e da máscara sensível à diferenciação de calcificação e hemossiderina simultaneamente. Materiais e Métodos: Imagens de tomografia computadorizada e por ressonância magnética (magnitude e fase) foram selecionadas, retrospectivamente, de seis pacientes (idades entre 41 e 54 anos; quatro homens). O processamento das imagens SWI foi realizado em rotina própria no programa Matlab. Resultados: Dos seis pacientes estudados, quatro apresentaram calcificações nas imagens de tomografia computadorizada. Nestes, as imagens SWI mostraram sinal hiperintenso para as regiões de calcificações. Os outros dois pacientes não apresentaram calcificações nas imagens de tomografia computadorizada e apresentaram depósito de hemossiderina com sinal hipointenso na imagem SWI. Conclusão: A escolha do tempo de eco e da máscara pode alterar toda a informação da imagem SWI e comprometer a confiabilidade diagnóstica. Dentre as possíveis máscaras, destacamos que a máscara sigmoide permite contrastar calcificação e hemossiderina em uma única imagem SWI. .

Evaluation of nuclear magnetic resonance spectroscopy variability

INTRODUCTION: The intrinsically high sensitivity of Magnetic Resonance Spectroscopy (MRS) causes considerable variability in metabolite quantification. In this study, we evaluated the variability of MRS in two research centers using the same model of magnetic resonance image scanner. METHODS: Two metabolic phantoms were created to simulate magnetic resonance spectra from in vivo hippocampus. The phantoms were filled with the same basic solution containing the following metabolites: N-acetyl-aspartate, creatine, choline, glutamate, glutamine and inositol. Spectra were acquired over 15 months on 26 acquisition dates, resulting in a total of 130 spectra per center. RESULTS: The phantoms did not undergo any physical changes during the 15-month period. Temporal analysis from both centers showed mean metabolic variations of 3.7% in acquisitions on the same day and of 8.7% over the 15-month period. CONCLUSION: The low deviations demonstrated here, combined with the high specificity of Magnetic Resonance Spectroscopy, confirm that it is feasible to use this technique in multicenter studies in neuroscience research.

Magnetic resonance imaging and neuropsychological testing in the spectrum of normal aging

OBJECTIVE: To understand the relationships between brain structures and function (behavior and cognition) in healthy aging. METHOD: The study group was composed of 56 healthy elderly subjects who underwent neuropsychological assessment and quantitative magnetic resonance imaging. Cluster analysis classified the cohort into two groups, one (cluster 1) in which the magnetic resonance imaging metrics were more preserved (mean age: 66.4 years) and another (cluster 2) with less preserved markers of healthy brain tissue (mean age: 75.4 years). RESULTS: The subjects in cluster 2 (older group) had worse indices of interference in the Stroop test compared with the subjects in cluster 1 (younger group). Therefore, a simple test such as the Stroop test could differentiate groups of younger and older subjects based on magnetic resonance imaging metrics. CONCLUSION: These results are in agreement with the inhibitory control hypotheses regarding cognitive aging and may also be important in the interpretation of studies with other clinical groups, such as patients with dementia and mild cognitive impairment. .

Ressonância magnética em portadores de sistema artificial de estimulação cardíaca: indicar ou não? / Magnetic resonance imaging in patients with artificial cardiac pacing system: state or not?

Este artigo busca compilar e organizar as informações atualmente disponíveis e sugerir algumas medidas de segurança para a realização do exame de ressonância magnética (IRM), na ausência de alternativa diagnóstica. Até o momento, não há estudos com a fnalidade de criar uma normativa de consenso, que envolvam todos os interessados no tema. Estudos recentes indicam que é possível realizar com segurança exames de IRM em portadores de sistemas artificiais de estimulação cardíaca (SAEC), desde que algumas ações preventivas sejam observadas previamente. São abordadas propostas para alcançar um consenso em relação ao exame de IRM no portador de SAEC. Os dispositivos mais novos oferecidos ao mercado já incorporam tecnologia para aumentar a segurança dos pacientes submetidos a IRM.