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Yih-Yian Sitoh

Publications and source records attributed to Yih-Yian Sitoh.

7 recordsLinked to original sources
PubMed2006

Contrast-enhanced flair imaging in the evaluation of infectious leptomeningeal diseases.

PURPOSE: The purpose of our study was to compare contrast-enhanced fluid-attenuated inversion recovery (FLAIR) images with contrast-enhanced T1 weighted images for infectious leptomeningitis. MATERIALS AND METHODS: We studied twenty-four patients with a clinical suspicion of infectious meningitis with unenhanced FLAIR, contrast-enhanced T1 weighted and contrast-enhanced FLAIR MR sequences. Twelve patients had cytologic and biochemical diagnosis of meningitis on cerebrospinal fluid (CSF) examination obtained 48 h before or after the MR study. Sequences were considered positive if abnormal signal was seen in the subarachnoid space (cistern or sulci) or along pial surface. RESULTS: Twenty-seven examinations in 24 patients were performed. Of the 12 patients (thirteen studies) in whom cytology was positive, unenhanced FLAIR images were positive in six cases (sensitivity 46%), contrast-enhanced FLAIR images were positive in 11 (sensitivity 85%), and contrast-enhanced T1 weighted MR images were positive in 11 patients (sensitivity 85%). Of the 12 patients (14 studies) in whom cerebrospinal fluid study was negative, unenhanced FLAIR images were negative in 13, contrast-enhanced FLAIR images were negative in 11, and contrast-enhanced T1 weighted MR images were negative in eight. Thus, the specificity of unenhanced FLAIR, contrast-enhanced FLAIR and contrast-enhanced T1 weighted images was 93, 79 and 57%, respectively. CONCLUSION: Our results suggest that post-contrast FLAIR images have similar sensitivity but a higher specificity compared to contrast-enhanced T1 weighted images for detection of leptomeningeal enhancement. It can be a useful adjunct to post-contrast T1 weighted images in evaluation of infectious leptomeningitis.

Adolescent↗
PubMed2006

Evaluation of dementia: the case for neuroimaging all mild to moderate cases.

INTRODUCTION: The aim of this study was to assess the usefulness of 4 clinical prediction rules, the neuroimaging guidelines from the Canadian Consensus Conference on Dementia (CCCAD) and the modified Hachinski's Ischaemic Score (HIS) in identifying patients with suspected dementia who will benefit from neuroimaging. MATERIALS AND METHODS: Two hundred and ten consecutive patients were referred to the memory clinic in a geriatric unit for the evaluation of possible dementia. Sensitivity, specificity and likelihood ratios (LR) were calculated for each of the prediction rules and the CCCAD guidelines, in terms of their ability to identify patients with significant lesions [defined firstly as space-occupying lesions (SOL) alone and secondly as SOL or strokes] on neuroimaging. Similar analyses were applied for the HIS in the detection of strokes. RESULTS: When considering SOL alone, sensitivities ranged from 28.6% to 100% and specificities ranged from 21.7% to 88.4%. However, when strokes were included in the definition of significant lesions, sensitivities ranged from 16.2% to 79.0% and specificities ranged from 20.9% to 92.4%. The modified HIS had a similarly poor sensitivity and specificity (43.3% and 78.9% respectively). The LR for the clinical decision tools did not support the use of any particular instrument. CONCLUSIONS: Clinical decision tools do not give satisfactory guidance for determining the need for neuroimaging patients with suspected dementia, when the detection of strokes, in addition to SOL, is regarded as important. We recommend therefore that neuroimaging be considered for all patients with suspected mild or moderate dementia in whom the potential benefits of any treatment outweigh the potential risks.

Aged↗
PubMed2005

Functional magnetic resonance imaging in adult craniopagus for presurgical evaluation.

Cranially conjoined twins are rare and pose unique challenges in the preoperative evaluation of cerebral language function. The authors report on their experience in the functional magnetic resonance (fMR) imaging evaluation of adult craniopagus (temporoparietooccipital fusion) to evaluate hemispheric language dominance and the eloquent language areas in the preoperative planning stages. Conventional clinical imaging hardware originally designed for individuals was adapted and tailored for use in the twins. They were assigned a selection of language tasks while undergoing fMR imaging. Significant blood oxygen level-dependent activations were detected in the main language regions in each twin, that is, the inferior frontal gyrus (around the Broca area), the middle and superior temporal lobes (around the Wernicke area) together with the inferior parietal lobe, and the middle and superior frontal gyri. Overall, the right-handed twin was strongly left lateralized for language, whereas the left-handed twin showed more bilateral activation during language tasks. Noninvasive language mapping with the aid of fMR imaging has been demonstrated for the first time in total craniopagus.

Adult↗
PubMed2005

Facial fat volume in HIV-infected patients with lipoatrophy.

BACKGROUND: The volume and anatomical distribution of facial fat depletion in HIV related lipoatrophy have not been properly quantified. We aimed to determine the extent and distribution of facial fat loss in HIV-infected patients with lipoatrophy and whether this differs from wasting. DESIGN: We studied HIV-infected patients with clinically defined moderate to severe lipoatrophy without wasting (n = 15), clinically defined wasting (> 10% weight loss and recent opportunistic infection) with no previous reported lipodystrophy (n = 15), and controls without lipodystrophy or wasting (n = 15). Facial MRI scans were performed, and areas of fat were manually traced bilaterally in all individual image slices and summed to calculate volume in anatomically defined regions of interest. RESULTS: Patients with lipoatrophy had lower fat volumes in the temporal region (8.9 +/- 9.4 vs 20.5 +/- 7.2 ml; P < 0.001), cheek region (25.6 +/- 24.9 vs 55.5 +/- 15.0 ml; P < 0.001), periorbital region (1.9 +/- 1.0 vs 2.7 +/- 1.0 ml; P = 0.09) and buccal fat pad (13.4 +/- 9.4 vs 21.8 +/- 9.8 ml; P = 0.030) compared with controls. Patients with wasting had temporal, cheek, periorbital and buccal fat pad volumes (10.4 +/- 6.7 ml, 34.0 +/- 14.8 ml, 1.4 +/- 1.1 ml and 13.1 +/- 4.6 ml respectively) that were lower than controls (all P < 0.01) but similar to lipoatrophy patients (all P > 0.5). CONCLUSIONS: Facial fat depletion in lipoatrophy is substantial (approximately 50% volume loss) and involves superficial and deep fat (buccal fat pad). The distribution and volume of fat change is similar to that seen in wasting. Given the extent of the changes, complete surgical correction is unlikely to be possible and hence emphasis should be placed on prevention of lipoatrophy [corrected]

Adipose Tissue↗
PubMed2004

Parallel imaging techniques in functional MRI.

Originally developed for increased scanning velocity in cardiac imaging, parallel imaging (PI) techniques have recently also been applied for the reduction of artifacts in single-shot techniques. In functional brain imaging (fMRI) techniques, PI has been used for several purposes. It has been applied to reduce the distortions caused by the length of the echo-planar imaging readout, diminution of the gradient-related acoustic noise, as a means to increase acquisition speed or to increase the achievable brain coverage per unit time. In this article, the different applications of PI techniques in fMRI are reviewed, together with the basic theoretical background and the recently developed hardware necessary to achieve rapid, high signal-to-noise ratio PI-fMRI.

Artifacts↗
PubMedDate not supplied

Combined magnetic resonance tractography and functional magnetic resonance imaging in evaluation of brain tumors involving the motor system.

The goal of neuro-oncologic surgery is to maximize tumor resection while preserving vital brain functions. Identification of the relation between the tumor and adjacent functional cortical areas as well as efferent subcortical white matter tracts is important for preservation of function. Combined diffusion tensor imaging with magnetic resonance (MR) tractography and functional blood oxygen level-dependent MR imaging were applied successfully for preoperative planning and guidance in 2 patients with tumors near the motor cortex. The combination of these novel functional imaging techniques can provide new information for presurgical planning.

Adult↗