Winston E. H. Lim

Phonological processing in Chinese-English bilingual biscriptals: an FMRI study

The advent of modern neuroimaging techniques such as functional magnetic resonance imaging (fMRI) provided an impetus for investigating language representation in the healthy bilingual brain. To date, neuroimaging experiments involving English-Chinese bilinguals suggest that common brain areas subserve the two languages. Given that the oral and written forms of English and Mandarin differ so markedly, and differences have been reported for bi-alphabetic readers, the null findings for English-Chinese bilinguals warrant further investigation. In this paper, the language representation of skilled English-Chinese bilingual biscriptals was investigated at the phonological level, using both equivalent behavioural (N = 28) and fMRI (n = 6) experiments. Differences in neural activation patterns between English and Mandarin will be discussed.

Correlation of the apparent diffusion coefficient and the creatine level in early ischemic stroke: A comparison of different patterns by magnetic resonance

It has been reported that reduction of the apparent diffusion coefficient (ADC) after stroke can persist for several days, after which the ADC increases gradually to an abnormally high level. We evaluated ADC values of stroke lesions and compared the results to the cellular density of the lesion by means of the creatine (Cre) level. This two‐parameter estimation is of particular relevance in ascertaining the underlying cellular status. Lesion‐to‐contralateral ADC ratios (ADCn) were obtained based on diffusion‐weighted echo‐planar and fast spin‐echo imaging. Single‐voxel localized spectroscopy was used for quantification of cerebral metabolites in infarcted regions. Their levels were also compared to that in homotopic contralateral regions. Fifteen patients with ischemic stroke were examined at times ranging from 18–88 hours following the onset of symptoms. In the stroke lesion, there was a significant correlation between the ADC and the Cre level showing that the higher the cell density the lower the ADC value. For ADCn vs. the lesion Cre concentration and the lesion‐to‐contralateral Cre ratio (Cren), the strengths of relationship were R2 = 0.70 and 0.58, respectively. It is concluded that ADC is a good reflection of cell density. Greatly lowered ADC values occur within the context of a stable cellularity. ADC and the Cre level have complementary roles in the characterization of stroke lesion with regard to the sequential stage. J. Magn. Reson. Imaging 2001;13:335–343.

Hippocampal Volumetry with Magnetic Resonance Imaging: A Cost-Effective Validated Solution

Summary: Purpose: The clinical utility of hippocampal volumetry is well documented, but the materials and techniques required to perform the procedure are not widely available outside major research centers. We describe a personal computer‐based method of volumetric data analysis.

A developmental theory of the superior sagittal sinus(es) in craniopagus twins

IntroductionBased on the study of the vascular anatomy of craniopagus twins, and particularly that of Ladan and Laleh, a theory is hypothesised regarding the embryological formation of the sagittal sinuses.Theory and discussion The superior sagittal sinus develops in contact with the calvarium bone within the inter-periosteal leptomeningeal space following a signal from the midline of the telencephalic vesicle derived from a single prosencephalic one. The position of the falx cerebri and most likely in the deepest part, the corpus callosum, points to the position of this midline.

Vertebrae adjacent to spinal bone lesion are inconsistent reference markers: a magnetic resonance spectroscopic viewpoint.

To ascertain the suitability of vertebrae adjacent to spinal bone lesions as a signal intensity reference on MRI, and compare the MR spectroscopic appearance of vertebral body compression fractures due to malignant tumor infiltration, bone weakening (e.g., osteoporosis), and/or minor trauma.

Is Your Interventional Radiology Service Ready for SARS?: The Singapore Experience

The recent epidemic of severe acute respiratory syndrome caught many by surprise. Hitherto, infection control has not been in the forefront of radiological practice. Many interventional radiology (IR) services are therefore not equipped to deal with such a disease. In this review, we share our experience from the interventional radiologist’s perspective, report on the acute measures instituted within our departments and explore the long-term effects of such a disease on the practice of IR.

Optic Nerve Tortuosity and Globe Proptosis in Normal and Glaucoma Subjects

Purpose To assess the difference in optic nerve tortuosity during eye movements and globe proptosis between primary open angle glaucoma and normal subjects using orbital magnetic resonance imaging. Methods 10 Chinese subjects matched for age, ethnicity and refractive errors were recruited, including five normal controls and five patients with primary open angle glaucoma. All subjects underwent magnetic resonance imaging to assess their optic nerves and globes for three eye positions: primary gaze, adduction and abduction. Optic nerve tortuosity (optic nerve length divided by the distance between two ends) and globe proptosis (maximum distance between cornea and interzygomatic line) were measured from magnetic resonance imaging images. Results In adduction, the tortuosity of normal eyes was significantly larger than that of the glaucomatous eyes. Optic nerve tortuosity in adduction in the control and glaucoma groups were 1.004±0.003 (mean ± standard deviation) and 1.001±0.001, respectively (p=0.037). Globe proptosis (primary gaze) in glaucoma subjects (19.14±2.11 mm) was significantly higher than that in control subjects (15.32±2.79 mm; p = 0.046). Conclusions In this sample, subjects with glaucoma exhibited more taut optic nerves and more protruding eye globes compared to normal eyes. This may impact optic nerve head deformations in anatomically predisposed patients. Précis Eyes with glaucoma have tauter optic nerves compared with normal eyes, which may exert more force on the optic nerve head tissues during eye movements.