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P Dastidar

Publications and source records attributed to P Dastidar.

At least 37 records · Page 2Linked to original sources
PubMed2000

Volumetric measurements of right cerebral hemisphere infarction: use of a semiautomatic MRI segmentation technique.

The applications of a new segmentation software, Anatomatic, in the evaluation of volumetric measurements of brain infarctions and the new Medimag 3D software in the evaluation of 3D image representation of infarctions are described. These programs are applied to magnetic resonance imaging. The aim of this study is to evaluate the use of these software packages in making accurate volumetric measurements in 40 patients with right cerebral infarctions, in determining the correlations between the quantitated lesions and neurological/neuropsychological dysfunctions and in creating realistic 3D views of the infarctions. Using Anatomatic, reproducible infarction volumes were achieved with ease and within a reasonably fast time. Medimag helped achieve realistic 3D representations of the infarctions. When compared, the semiautomatic segmentation proved to be much faster and yielded higher infarction volumes than the manual segmentation technique. Significantly positive correlations between the infarction volumes and neurological dysfunctions and neuropsychological deficit (neglect) helped to explain the effect of volumes on the clinical status of the patients.

Adult↗
PubMed2000

Visual neglect as a predictor of functional outcome one year after stroke.

OBJECTIVE: The aim was to study the role of visual neglect in acute right hemisphere brain infarct as a predictor of poor functional outcome during the first year after stroke. In particular, we were interested in the additional value of neglect measures besides hemiparesis, hemianopia, cognitive deficits and age. PATIENTS AND METHODS: A consecutive series of 57 patients with a neuroradiologically verified right hemisphere infarct was examined within 10 days of the stroke. Fifty patients were followed up for 1 year. Neglect was measured with the Conventional and the Behavioural subtests of the Behavioural Inattention Test (BITC and BITB, respectively). The predictors were determined at the 10-day examination. Functional outcome was assessed 3, 6 and 12 months after the onset with the Frenchay Activities Index. RESULTS: Neglect in BITB was the best single predictor, which together with high age formed the best combination of predictors for poor functional outcome at each follow-up. Hemiparesis was also included in this prediction model at the 3-month follow-up, but hemianopia, BITC, or visuoconstructional and memory deficits showed no additional predictive value. However, neglect usually recovered soon. When neurological and cognitive deficits were assessed at the same time as the outcome, hemiparesis rather than neglect was the strongest correlate of poor outcome. CONCLUSION: Neglect in acute stroke is an important predictor of poor functional recovery. Residual neglect, which could be compensated in the follow-up tests, may nevertheless restrict patients' real-life activities and hobbies.

Acute Disease↗
PubMed2000

Unawareness of deficits after right hemisphere stroke: double-dissociations of anosognosias.

OBJECTIVES: The aim was to study whether anosognosia for hemiparesis, anosognosia for neglect and general unawareness of illness double-dissociate, indicating that anosognosias are specific and independent impairments of awareness. On the other hand, anosognosias may be associated with one another and with general cognitive dysfunction, which decreases awareness of deficits. The persistence and predictive value of anosognosias was examined during a 1-year follow-up. PATIENTS AND METHODS: Fifty-seven consecutive patients with acute right hemisphere infarction underwent neurological and neuroradiological examinations, neuropsychological testing and an interview 10 days, 3 months and 1 year after onset. RESULTS: Anosognosia for neglect and anosognosia for hemiparesis double-dissociated, as did unawareness of illness and anosognosia for neglect. Patients showing unawareness of illness or anosognosia for neglect and anosognosia for hemiparesis had poorer orientation and verbal memory than patients who were aware of these defects. Unawareness of illness and anosognosia for hemiparesis disappeared during 3-month follow-up. CONCLUSION: Double-dissociations demonstrate that anosognosias for different defects are independent and specific impairments of awareness, although general cognitive disorder may also reduce awareness of defects. Unawareness of illness and anosognosia for hemiparesis disappear rapidly and can hardly be direct causes of poor long-term recovery. However, transient anosognosia may be associated with persistent disorders which result in poor outcome.

Aged↗
PubMed2000

Preliminary X-ray analysis of a new crystal form of the Escherichia coli KDO8P synthase.

3-Deoxy-D-manno-octulosonate 8-phosphate (KDO8P) synthase catalyzes the biosynthesis of an essential component of the lipopolysaccharide of all Gram-negative bacteria. The structure and mechanism of KDO8P synthase are being actively studied as this enzyme represents an important target for antibiotic therapy. The structure of the Escherichia coli KDO8P synthase in cubic crystals (space group I23) has recently been determined and the enzyme shown to be a tetramer of identical subunits. However, this information is challenged by biochemical studies, which suggest that the enzyme behaves in solution as a homotrimer. Here, the preparation and preliminary X-ray analysis of monoclinic crystals of KDO8P synthase are reported. The crystals belong to space group P2(1), with unit-cell parameters a approximately 50, b approximately 140, c approximately 74 A, beta approximately 105 degrees. The structure of KDO8P synthase in the monoclinic crystal form was determined by molecular replacement, using as a search model one of the subunits of the enzyme in the cubic crystals. A tetramer of KDO8P synthase with 222 local symmetry is also present in the asymmetric unit of the P2(1) crystals, with a solvent content of 43%. The observation that the same quaternary structure of KDO8P synthase is observed in two different crystal forms belonging to distinct crystal systems (monoclinic and cubic) suggests that a tetramer is the native form of the enzyme.

Aldehyde-Lyases↗
PubMed2000

Low plasma antioxidant activity is associated with high lesion volume and neurological impairment in stroke.

BACKGROUND AND PURPOSE: Oxidative stress is probably involved in neuronal damage induced by ischemia-reperfusion. The purpose of this study was to assess the role of antioxidant activity in cerebral ischemic stroke. METHODS: Antioxidant activity of blood plasma and cerebrospinal fluid was assessed in 22 patients with cerebral hemisphere infarction that was verified and quantified by MRI. RESULTS: Low total peroxyl radical trapping potential of plasma, but not of cerebrospinal fluid, was associated with high lesion volume and high neurological impairment assessed by scores on NIH Stroke Scale, Barthel Index, and Hand Motor Score tests. The plasma concentrations of ascorbic acid, alpha-tocopherol, and protein thiols were also associated with the degree of neurological impairment. CONCLUSIONS: These data suggest that the antioxidant activity of plasma may be an important factor providing protection from neurological damage caused by stroke-associated oxidative stress.

Adult↗
PubMed2000

Magnetic resonance imaging compared to ultrasonography in fetal weight and volume estimation in diabetic and normal pregnancy.

OBJECTIVE: To estimate fetal volume and weight in diabetic and normal pregnancy using high-resolution magnetic resonance imaging. METHODS: T1-weighted magnetic resonance imaging was combined with semiautomatic segmentation technique. The accuracy of fetal volume estimations thus obtained was compared with conventional ultrasound-based weight estimations in ten pregnant women with insulin-dependent diabetes mellitus and ten women with normal pregnancy. Examinations were made within 48 hours before delivery. RESULTS: Ultrasound-based estimations of fetal weight showed a correlation rate of r=0.77 with the actual birth weights in the whole material, while volume determinations based on magnetic resonance imaging showed a significantly better correlation rate of r=0.95. Diabetic women did not differ from the normal pregnancy group with regard to birth weight or the accuracy of weight estimations. CONCLUSIONS: High-resolution magnetic resonance imaging combined with semiautomatic segmentation software was found to be accurate in determining fetal volume and, consequently, better than conventional ultrasound-based techniques in estimating fetal weight. The use of magnetic resonance imaging in fetal weight estimation may be recommended for clinical situations where an accurate weight estimate is considered essential.

Adult↗
PubMed1999

Volumes of brain atrophy and plaques correlated with neurological disability in secondary progressive multiple sclerosis.

The objectives of the present study was to correlate the segmented magnetic resonance imaging (MRI) volumes of intracranial cerebrospinal fluid (CSF) spaces (expressing the extent of brain atrophy) and cerebral plaques with the neurological disability in secondary progressive multiple sclerosis (MS). Earlier studies have mainly correlated MS plaques and neurological disability measured by expanded disability status scale (EDSS). The data on the association between brain atrophy and EDSS or regional functional scoring scale (RFSS) are very limited. We measured the volumes of intracranial CSF spaces in 28 patients with secondary progressive MS using MRI, and semiautomatic segmentation software. The volumes of T1-weighted hypointense and T2-weighted hyperintense MS plaques were also measured. In multiple regression analysis, increasing volumes of total (P=0.006) and relative (P=0.005) intracranial CSF spaces were significantly associated with worsening neurological disability as expressed by EDSS. No associations were found between these intracranial CSF space volumes and total RFSS scores. The mean volume of T2-weighted plaques showed a tendency to associate with total RFSS score (r=0.40, P=0.03), but no correlations were detected between T1- or T2-weighted plaque volumes and EDSS. The application of a new segmentation technique in quantifying intracranial cerebrospinal fluid spaces allowed an exact and sensitive way of assessing brain atrophy. The associations between brain atrophy and neurological disability expressed by EDSS suggests that the effect of MS therapies should be evaluated by measurement of brain atrophy.

Adult↗
PubMed1999

Computerised volumetric analysis of lesions in multiple sclerosis using new semi-automatic segmentation software.

The paper describes the application of new semi-automatic segmentation software to the task of detection of anatomical structures and lesion and their three-dimensional (3D) visualisation in 23 patients with secondary progressive multiple sclerosis (MS). The purpose is to study the correlation between magnetic resonance imaging (MRI) parameters (volumes of plaques and cerebrospinal fluid spaces) and clinical deficits (neurological deficits in the form of EDSS and RFSS scores, and neuropsychological deficits). The software operates in PC/Windows and PC/NeXTstep environments and utilises graphical user interfaces. Quantitative accuracy is measured by performing segmentation of fluid-filled syringes (relative error of 1.5%), and reproducibility is measured by intra- and inter-observer studies (3% and 7% variability, respectively). The mean volumes of MS plaques show significant correlations with the total RFSS scores (p = 0.04). Relative intracranial cerebrospinal fluid (CSF) space volumes show statistically significant correlation with EDSS scores (p = 0.01). The mean volume of MS plaques shows a significant correlation with the overall neuropsychological deficits (p = 0.03). 3D visualisation helps to understand the relationship of lesions to the surrounding brain structures. The use of semiautomatic segmentation techniques is recommended in the clinical diagnosis of MS patients.

Brain↗
PubMed1999

Semi-automatic segmentation of computed tomographic images in volumetric estimation of nasal airway.

The objective of this study was to determine nasal cavity volumes and cross-sectional profiles from segmented coronal high-resolution computed tomography (HRCT) images. Pathological mucosal changes and congenital sinonasal variants were quantitated and three-dimensional (3D) images for determining sinonasal airway diseases evaluated by using the new semiautomatic segmentation software, Anatomatic. Anterior to posterior cross-sectional profiles of the sinonasal airway were obtained from acoustic rhinometry and segmented coronal HRCT images and compared in five patients having complaints of nasal obstruction and chronic sinusitis. Results showed that accurate volumes of air spaces in the nasal cavity and paranasal sinuses were obtained. When compared, the cross-sectional profiles of the nasal cavities obtained from acoustic rhinometry and the segmentation technique were similar in the anterior portion, but differed in the posterior portion. The results obtained by coronal HRCT and segmentation were more reliable than those produced with acoustic rhinometry. 3D images acquired from segmented images were found to help make a good pre-operative assessment of the whole sinonasal compartment. Segmentation and volumetric analysis using the Anatomatic technique also proved to be well suited to the evaluation of the nasal cavity and paranasal sinus geometry in patients with sinonasal diseases.

Acoustics↗
PubMed1998

Semi-automatic tool for segmentation and volumetric analysis of medical images.

Segmentation software is described, developed for medical image processing and run on Windows. The software applies basic image processing techniques through a graphical user interface. For particular applications, such as brain lesion segmentation, the software enables the combination of different segmentation techniques to improve its efficiency. The program is applied for magnetic resonance imaging, computed tomography and optical images of cryosections. The software can be utilised in numerous applications, including pre-processing for three-dimensional presentations, volumetric analysis and construction of volume conductor models.

Brain Ischemia↗
PubMed1998

Cortical silent period evoked by transcranial magnetic stimulation in ischemic stroke.

OBJECTIVES: Transcranial magnetic stimulation (TMS) of the motor cortex produces motor evoked potentials (MEPs). Besides this excitatory response, TMS has inhibitory effects. When TMS is performed during voluntary muscle contraction, the MEP is followed by a pause in electromyographic activity (cortical silent period, SP). The aim of this study was to evaluate the clinical usefulness of the SP. METHODS: We studied SP changes in 50 patients with acute hemispheric brain infarction. A stimulator with a round coil and a fixed intensity of 90% of maximum was used to evoke MEPs. RESULTS: SP was elicited on the affected side in 29 of the 50 patients. The mean SP duration was markedly longer on the affected side in the patient group. There were no significant differences between left and right sides in the means of the MEP amplitude ratio (amplitude related to corresponding amplitudes to peripheral electric stimulation) and MEP latencies in the patient group. Prolonged SP was found in 25 of the 29 patients (86%) whereas only 4 (14%) had abnormalities in MEP latency or amplitude ratio. The mean SP duration was significantly prolonged also in a subgroup of 14 patients with normal hand function. CONCLUSIONS: The SP measurement is an easily performed and sensitive method to detect even subclinical disturbances in motor system function in ischemic stroke.

Adult↗
PubMed1998

CSF and MRI findings in patients with acute herpes zoster.

OBJECTIVE: To explore MRI and CSF findings in patients with herpes zoster (HZ) and to correlate the findings with clinical manifestations of the disease. METHODS: Fifty immunocompetent patients (mean age, 59 years; range, 17 to 84 years) with HZ of fewer than 18 days duration participated. None had clinical signs of meningeal irritation, encephalitis, or myelitis. In 42 patients (84%), the symptoms constituted pain and rash only. Six patients (12%) had motor paresis, and three patients (6%) had ocular complications. One to three CSF samples were obtained from 46 patients (the first sampling taken 1 to 18 days from onset of rash), and 16 patients (all with either trigeminal or cervical HZ) underwent MRI of the brain. The clinical follow-up continued at least 3 months. RESULTS: CSF was abnormal in 28/46 patients (61%): pleocytosis (range, 5 to 1,440 microL) was detected in 21, elevated protein concentration in 12, varicella zoster virus (VZV) DNA in 10, and immunoglobulin G antibody to VZV in 10. These changes were more common in patients with acute complications, although they did not predict development of postherpetic neuralgia (PHN). In 9/16 patients (56%), MRI lesions attributable to HZ were seen in the brainstem and cervical cord. At 3 months, 5/9 patients (56%) with abnormal MRI had PHN, whereas none of the 7 patients with no HZ-related lesions on MRI had any remaining pain. CONCLUSIONS: Subclinical extension of viral inflammation into the CNS occurs commonly in HZ. This finding may have implications for treatment of HZ and prevention of various associated complications.

Acute Disease↗
PubMed1998

Methylprednisolone reduces adhesion molecules in blood and cerebrospinal fluid in patients with MS.

OBJECTIVE: To analyze the expression of adhesion molecules on mononuclear cells from blood and CSF of patients with exacerbations of MS before and after megadose IV methylprednisolone (MP). BACKGROUND: Adhesion molecules regulate transmigration of lymphocytes and monocytes/macrophages to the CNS and have an important role in the pathogenesis of MS. METHODS: The expression of very late activation antigen 4 (VLA-4) and vascular cell adhesion molecule 1, lymphocyte function-associated antigen 1 (LFA-1), and intercellular adhesion molecule 1 (ICAM-1) was analyzed immunocytologically on lymphocytes and monocytes from blood and CSF of 23 patients and 11 healthy control subjects. The results were correlated with the Expanded Disability Status Scale and in half of the patients with the number of T2-weighted MS plaques and brain atrophy analyzed by MRI. RESULTS: After treatment, the mean proportions of VLA-4, LFA-1, and ICAM-1 on blood lymphocytes (p < 0.0003, p < 0.00001, p < 0.01) and monocytes (p < 0.0001, p < 0.0002, p < 0.007) of 23 patients decreased. The expression of these adhesion proteins was also diminished on CSF leukocytes. However, even after treatment, the levels of VLA-4 and LFA-1 on lymphocytes from blood of MS patients remained higher than in the control subjects. The level of VLA-4 and LFA-1 on blood lymphocytes (r=0.67, p=0.023) and VLA-4 on monocytes (r=0.61, p=0.047) correlated with the number of T2-weighted lesions. CONCLUSIONS: Megadose MP may suppress brain inflammation by reducing the expression of adhesion molecules on mononuclear cells from blood and CSF of MS patients. The inhibition of cellular trafficking in MS by MP offers an important means of altering the autoimmune response in MS.

Adult↗
PubMed1997

Segmentation of T1 MR scans for reconstruction of resistive head models.

This paper describes a segmentation method primarily developed for reconstructing resistive head models for electroencephalographic modelling purposes. The method was implemented by combining several image processing techniques, such as amplitude segmentation, region growing, and image fusion. Also a graphical user interface was developed to enable semiautomatic approach to the segmentation process. This method was developed especially for segmentation of the brain and skull from T1-weighted magnetic resonance images, but can also be applied in any segmentation procedure. The entire project was implemented successfully in a PC-based computer running the Unix/NeXTstep operating system.

Algorithms↗
PubMed1997

Pain in spasmodic torticollis.

Spasmodic torticollis (cervical dystonia) is frequently a painful condition but little is known of the characteristics of the pain. We assessed 39 patients with spasmodic torticollis for the presence or absence, location, and quality of pain, as well as its correlation to postural abnormality. Muscle tenderness was evaluated by manual palpation and pressure algometry. Measurements were made on muscles either actively maintaining or opposing abnormal head posture, as well as on muscles not contributing to it. Control measurements were made in 18 healthy subjects. Two-thirds of patients reported continuous or intermittent recurrent pain. Pain was reported widespread and diffuse over the neck and shoulders, with some radiation, predominantly on the side toward which the head was twisted. There were no differences between study groups when compared for pressure algometry and only moderate differences when compared for manual palpation. No correlation was found between the severity of motor signs and pain. Degenerative changes seen on X-rays were similar in painful and pain-free patients. These findings suggest that pain associated with spasmodic torticollis does not arise in muscles alone, and we hypothesise that central mechanisms are also involved.

Adult↗