Biomedical subjects

N Saeed

Publications and source records attributed to N Saeed.

41 records · Page 3Linked to original sources

PubMedDate not supplied

A registration and interpolation procedure for subvoxel matching of serially acquired MR images.

OBJECTIVE: Methods for automatically registering and reslicing MR images using an interpolation function that matches the structure of the image data are described. MATERIALS AND METHODS: Phantom and human brain images were matched by rigid body rotations and translations in two and three dimensions using a least-squares optimization procedure. Subvoxel image shifts were produced with linear or sinc interpolation. RESULTS: The use of sinc interpolation ensured that the repositioned images were faithful to the original data and enabled quantitative intensity comparisons to be made. In humans, image segmentation was vital to avoid extraneous soft tissue changes producing systematic errors in registration. CONCLUSIONS: The sinc-based interpolation technique enabled serially acquired MR images to be positionally matched to subvoxel accuracy so that small changes in the brain could be distinguished from effects due to misregistration.

Humans↗

PubMedDate not supplied

Detection of subtle brain changes using subvoxel registration and subtraction of serial MR images.

OBJECTIVE: The aim of this study was to examine the potential of accurate image registration for detecting subtle changes in the brain. MATERIALS AND METHODS: Isotropic T1-weighted volume images were obtained in 10 normal subjects and five patients on two or more occasions (including pre- and postcontrast studies). The images were segmented and a 3D rigid body translation and rotation technique was used with sinc interpolation to precisely match the images using a chi 2-test. The registered images and the subtraction images produced from them were used to detect changes in signal intensity, sit, shape, and size of the brain. RESULTS: Small changes due to differences in orientation of the head, growth, and development as well as inhalation of oxygen and carbogen (95% O2/5% CO2) were observed in normal subjects. Changes were also observed in patients with minor head trauma, a meningioma, an astrocytoma, and multiple sclerosis. Differences due to contrast enhancement and surgery and/or anesthesia were also seen. CONCLUSION: With use of subvoxel registration, subtle changes in the brain were detected in a variety of physiological and clinical situations where differences have hitherto been difficult or impossible to detect.

Adult↗

PubMedDate not supplied

A knowledge-based approach to deconvolve the water component in in vivo proton MR spectroscopy.

OBJECTIVE: The water component dominates in in vivo proton (1H) spectroscopy. This consists of a prominent central peak with large "wings," and consequently metabolites that lie on the "wings" become difficult to quantitate. A method has been developed to deconvolve the water component in in vivo 1H spectroscopy, hence highlighting the metabolite information. MATERIALS AND METHODS: Spectra were acquired from volunteers and patients using 4D chemical shift imaging. The water deconvolution procedure employed knowledge-based data processing in the frequency domain and was fully automated. This involved describing the water component as a coarse function consisting of a "bulk" region and "wing" areas. Points were identified in the spectrum that fit this description and then linked together to produce the water component. The latter was smoothed and then subtracted from the original spectra to produce good water deconvolution. RESULTS: Over 2,000 in vivo 1H spectra have been subjected to this algorithm. The method took approximately 5 s to execute per spectrum consisting of 2,048 data points. CONCLUSION: Knowledge-based data processing has provided a fast, efficient, and robust procedure to deconvolve the water component.

Adult↗

PubMedDate not supplied

Automated brain segmentation from single slice, multislice, or whole-volume MR scans using prior knowledge.

PURPOSE: An automated procedure has been developed to isolate the brain in single/multislice or whole-volume MR images obtained from various sequences. METHOD: T1-weighted, T2-weighted, and inversion recovery images were acquired. The brain segmentation procedure employed (A) a knowledge base that held generic information about the brain in the three orthogonal views and (B) a texture definition and intensity characteristics of features within the head. The brain was segmented by selectively blurring scans using components of B; contour following with region growing was initiated until the isolated feature satisfied the measurements in A. RESULTS: The brain was segmented automatically from 210 subjects (whole volume) and 52 subjects (multi/single slice). Detailed analysis of seven segmented brains showed that < 0.8% of the contour pixels were erroneously identified. Whole-volume head scans consisting of 140 x 256 x 256 pixels were segmented in < 30 min. CONCLUSION: A robust, fast, and efficient procedure has been developed to segment the brain from MR images.

Adult↗

PubMedDate not supplied

Eicosapentaenoic acid treatment in schizophrenia associated with symptom remission, normalisation of blood fatty acids, reduced neuronal membrane phospholipid turnover and structural brain changes.

The administration of the omega-3 fatty acid eicosapentaenoic acid (EPA) to a drug-naive patient with schizophrenia, untreated with conventional antipsychotic medication, led to a dramatic and sustained clinical improvement in both positive and negative symptoms. This was accompanied by a correction in erythrocyte membranes of abnormalities in both n-3 and n-6 highly unsaturated fatty acids and with reduced neuronal membrane phospholipid turnover, as evidenced by serial 31-phosphorus cerebral magnetic resonance spectroscopy. Using recently developed techniques of image segmentation, subvoxel registration and quantitation, analysis of serial high-resolution 3D cerebral MRI scans showed that, in the year before EPA treatment, cerebral atrophy was taking place and that this atrophy was reversed by six months of EPA treatment. These results demonstrate that EPA can reverse both the phospholipid abnormalities previously described in schizophrenia and cerebral atrophy. They provide strong further evidence in support of the membrane phospholipid model of schizophrenia.

Adult↗