Carlos F. Gonzalez

The sensitivity of the Mini‐Mental State Exam in the white matter dementia of multiple sclerosis

Fifty-six patients diagnosed with definite multiple sclerosis (MS) according to Poser criteria were administered the Mini-Mental State Examination (MMSE) and a comprehensive battery of neuropsychological tests. Extent of cerebral lesion involvement was determined by quantitative magnetic resonance imaging (MRI) ratings. The MMSE correlated with overall levels of physical disability, but did not correlate with total lesion area on MRI. Sensitivity of the MMSE to the subcortical dementia of MS was low (28%) when performance on the neuropsychological testing battery was used as the criterion. Impairment on tests of memory, speed of information processing, abstract reasoning, naming/verbal fluency, as well as visuoperceptual organization, were correlated highly with total lesion area on MRI. The low sensitivity of the MMSE to cognitive impairment in MS is discussed in terms of its item composition and the characteristic pattern of deficits found in MS.

Moyamoya disease in the United States

The epidemiology and radiological features of Moyamoya disease (MMD) in the US were investigated. This study encompassed 98 cases; 26 were newly collected from eight US institutions and 72 were previously reported in the US literature. The patients ranged in age from 6 months to 67 years with age peaks in the first, third and fourth decades. MMD was seen in various ethnic groups and females were more commonly involved (71%) than males. A specific etiology could not be determined in most cases but arteriosclerosis and use of oral contraceptives were occasional associations. On angiography and/or magnetic resonance angiography (MRA), carotid arterial stenosis or occlusion was seen bilaterally in 95 cases (97%) and unilaterally in three. On MR or MRA, internal carotid steno-occlusive lesions were well demonstrated in all cases but Moyamoya collateral vessels (MMVs) were visualized in only 65% of the patients. MMVs in the basal ganglia and thalami were best demonstrated on T1 weighted images. Parenchymal lesions were seen in all patients and were often bilateral. With advances in MR techniques and increasing awareness of diagnostic guidelines, MMD will be diagnosed more frequently than before in the US.

Fast tissue segmentation based on a 4D feature map in characterization of intracranial lesions.

The aim of this work was to develop a fast and accurate method for tissue segmentation in magnetic resonance imaging (MRI) based on a four‐dimensional (4D) feature map and compare it with that derived from a 3D feature map. High‐resolution MRI was performed in 5 normal individuals, in 12 patients with brain multiple sclerosis (MS), and 9 patients with malignant brain tumors. Three inputs (proton‐density, T2‐weighted fast spin‐echo, and T1‐weighted spin‐echo MR images) were routinely utilized. As a fourth input, either magnetization transfer MRT was used or T1‐weighted post‐contrast MRI (in patients only). A modified k‐nearest neighbor segmentation algorithm was optimized for maximum computation speed and high‐quality segmentation. In that regard, we a) discarded the redundant seed points; b) discarded the points within 0.5 standard deviation from the cluster center that were non‐overlapping with other tissue; and c) removed outlying seed points outside 5 times the standard deviation from the cluster center of each tissue class. After segmentation, a stack of color‐coded segmented images was created. Our new technique utilizing all four MRI inputs provided better segmentation than that based on three inputs (P < 0.001 for MS and P < 0.001 for tumors). The tissues were smoother due to the reduction of statistical noise, and the delineation of the tissues became sharper. Details that were previously blurred or invisible now became apparent. In normal persons a detailed depiction of deep gray matter nuclei was obtained. In malignant tumors, up to five abnormal tissue types were identified: 1) solid tumor core, 2) cyst, 3) edema in white matter 4) edema in gray matter, and 5) necrosis. Delineation of MS plaque in different stages of demyelination became much sharper. In conclusion, the proposed methodology warrants further development and clinical evaluation. J. Magn. Reson. Imaging 1999;9:768–776.

Distributional Patterns of Multiple Sclerosis Brain Lesions Magnetic Resonance ImagingClinical Correlation

Forty–one patients with multiple sclerosis were studied with magnetic resonance imaging (MRI) and a battery of neuropsychological tests to determine the pattern of lobar distribution of lesions in the relapsing–progressive and relapsing–remitting forms of the disease. Correlation of lesions with the patients cognitive and emotional dysfunction was also obtained. The results of this study indicate that patients with relapsing–progressive multiple sclerosis are characterized by the large or coalescent lesions located predominantly in the periventricular area. These lesions were more frequently found in the parietooccipital areas and were accompanied by significant cognitive dysfunction and severe personality changes. The patients with relapsing–remitting disease, however, were characterized by punctiform or small discrete lesions predominantly located in the intermediate and subcortical areas. These lesions were more frequently seen in the parietooccipital regions and the patients had significantly less severe cognitive and emotional involvement than did the patients with relapsing–progressive disease. Recognition of these patterns was easily accomplished by MRI. In this investigation MRI studies were utilized as an index of the pathological changes occurring at one point in time in the evaluation of the disease. Only repeated MRI studies and continuous clinical observation can establish the final diagnosis.

Hemodynamic changes in recurrent intracranial terminal aneurysm after endovascular treatment

RATIONALE AND OBJECTIVES Multiple cases of recurrence of aneurysms after endovascular treatment have been reported. The purpose of the current hemodynamic study was to identify changes in shear stress and pressure associated with the recurrence of terminal intracranial aneurysms after endovascular occlusion. METHODS Using a finite element method, a pulsed flow with a non-Newtonian viscosity of blood was simulated within the aneurysm cavity. A recurrent terminal intracranial aneurysm of a patient originally treated with balloon occlusion was then studied. This was based on a physiologic pulsatile flow, which was observed in the middle cerebral artery. Before and after the balloon occlusion, local maximum wall shear stress and pressure drop at the neck of the aneurysm were calculated and compared with the normal shear stress. RESULTS Although the maximum shear stress at the right neck of the aneurysm was significantly reduced after balloon insertion, it was still 2.5 times greater than the normal maximum shear stress. This was attributable to the presence of a portion of the aneurysmal neck (residual neck), which was not obliterated by the balloon. The balloon also helped to reduce the maximum pressure inside the aneurysm by approximately 15%. Hemodynamic changes in the residual aneurysm neck, where the shear stress and the pressure are high, and other factors may be responsible for the recurrence of aneurysms after balloon or coil occlusion. CONCLUSION Residual necks after balloon occlusion, coil occlusion, or both are attributable to the geometric orientation of the aneurysm with respect to parent and daughter vessels and the variety of configurations of the balloon and coils used to occlude the aneurysms. Inadequate reduction in local shear stress found in these residual necks is an important factor in the recurrence and rupture of the aneurysm after endovascular occlusion.

Tissue Segmentation in MRI as an Informative Indicator of Disease Activity in the Brain

The presented tissue segmentation technique is based on a multispectral analysis approach. The input data were derived from high resolution MR images. Usually, only two inputs, proton density (PD) and T2-weighted images, are utilized to calculate the 2D feature map. In our method, we introduced a third input, T1-weighted MR image, for segmentation based on 3D feature map. k-Nearest Neighborhood segmentation algorithm was utilized. Tissue segmentation was performed in phantoms, normal humans and those with brain tumors and MS. Our technique utilizing all three inputs provided the best segmentation (p<0.001). The inclusion of T1 based images into segmentation produced dramatic improvement in tissue identification. Using our method, we identified the two distinctly different classes of tissue within the same MS plaque. We presume that these tissues represent the different stages involved in the evolution of the MS lesions. Further, our methodology for measuring MS lesion burden was also used to obtain its regional distribution as well as to follow its changes over time. The segmentation results were in full accord with neuropsychological findings.

Tissue segmentation by high resolution MRI: improved accuracy and stability

Tissue segmentation based on 2D and 3D feature maps derived from high resolution MR images was performed in experimental brain edema in cats, normal humans and those with brain tumors and MS. Statistical and anisotropic diffusion filters were applied to the data. The k-nearest neighborhood segmentation algorithm was utilized. Segmentation based on a 3D feature map was found to be much better than that based on a 2D feature map (p<0.01). Inter-observer variability ranged between 6.6% and 9.3% and intra-observer variability ranged between 8.3% and 10.4%. The use of high resolution MRI resulted in detection of new lesions which well correlated with neuropsychological exams. In conclusion, the presented technique is an accurate, stable and promising method of tissue characterization.<<ETX>>

Correlation between structural brain lesions and emotional and cognitive function in patients with multiple sclerosis: an MRI study

Forty-two patients in the acute phase of multiple sclerosis (MS) were studied with MRI and a battery of neuropsychological tests to determine the correlation beween the quantity and distribution of MS plaques in the brain and the emotional and cognitive profile. A semiautomated quantitative system was utilized to measure MRI variables such as focal distribution of the lesions in specific regions of the white matter, total lesion area, size of the corpus callosum, and ventricular brain ratio. Our findings indicate good correlation between cognitive dysfunction and altered emotional status with the total lesion area. The greatest correlation was found with lesions in the parietal and occipital areas. This suggests that white matter damage in this region may result in dementia and affective changes such as euphoria and depression.

Enhanced resolution of pituitary fossa by three-dimensional fat-suppressed gradient-echo magnetic resonance: before and after gadolinium enhancement.

In imaging small anatomical parts such as the pituitary fossa, thin sections enhance the spatial resolution. Gradient recalled images (GRASS) using three‐dimensional volume data produce ultrathin contiguous sections with a high signal‐to‐noise ratio. In this study, conventional spin‐echo magnetic resonance images (MRis) of the pituitary fossa were compared to threedimensional gradient recalled MRI in 5 volunteers and 10 patients suspected of having pituitary gland abnormalities. Utility of fat suppression was also assessed, along with gadolinium enhancement. Conventional spin‐echo and three‐dimensional spoiled GRASS images, three‐dimensional spoiled GRASS images without and with fat suppression (Group II), and three‐dimensional spoiled GRASS images with fat suppression before and after gadolinium enhancement were compared. Three‐dimensional spoiled GRASS images provided better delineation of the pituitary fossa structures. There was differential enhancement between the normal gland and pituitary tumors. The fat suppression technique following gadolinium administration helped separate the high signal of tumor from the high signal of the clivus marrow. In conclusion, T1‐weighted three‐dimensional gradient‐echo images with fat suppression following gadolinium enhancement appear promising in evaluation.

Plain Film Radiography and Polytomography of the Orbit

Diagnostic imaging technologies are becoming of increasing value in the evaluation of ophthalmologic patients. These techniques include routine radiographic studies, tomographic radiography, computed tomography (CT), ultrasound imaging, and magnetic resonance imaging (MRI). To understand and evaluate these studies, a knowledge of orbital anatomy is vital.