Biomedical subjects

Asht M Mishra

Publications and source records attributed to Asht M Mishra.

8 recordsLinked to original sources

PubMed2006

Demonstration of interstitial cerebral edema with diffusion tensor MR imaging in type C hepatic encephalopathy.

Brain water may increase in hepatic encephalopathy (HE). Diffusion tensor imaging was performed in patients with cirrhosis with or without HE to quantify the changes in brain water diffusivity and to correlate it with neuropsychological (NP) tests. Thirty-nine patients with cirrhosis, with minimal (MHE) or overt HE, were studied and compared to 18 controls. Mean diffusivity (MD) and fractional anisotropy (FA) were calculated in corpus callosum, internal capsule, deep gray matter nuclei, periventricular frontal, and occipital white matter regions in both cerebral hemispheres. The MD and FA values from different regions in different groups were compared using analysis of variance and Spearman's rank correlation test. In 10 patients with MHE, repeat studies were performed after 3 weeks of lactulose therapy to look for any change in MD, FA, and NP scores. Significantly increased MD was found with insignificant changes in FA in various regions of brain in patients with MHE or HE compared with controls, indicating an increase in interstitial water in the brain parenchyma without any microstructural changes. A significant correlation was found between MD values from corpus callosum, internal capsule, and NP test scores. After therapy, MD values decreased significantly and there was a corresponding improvement in NP test scores. Further analysis showed that MD values were different for different grades of minimal or overt HE. In conclusion, the increase in MD with no concomitant changes in FA in cirrhosis with minimal or early HE indicates the presence of reversible interstitial brain edema.

Adolescent↗

PubMed2006

Comparison of the magnetization transfer ratio and fluid-attenuated inversion recovery imaging signal intensity in differentiation of various cystic intracranial mass lesions and its correlation with biological parameters.

PURPOSE: To compare the signal intensity on the fluid attenuated inversion recovery (FLAIR) sequence and magnetization transfer ratios (MTRs) for the differentiation of abscesses from non-abscess cystic brain lesions, and to correlate these MR parameters with the viscosity, viable cell density and total protein concentration of the cystic fluid. MATERIALS AND METHODS: Signal intensity on FLAIR and MTRs from the cystic cavity of lesions were calculated from 33 patients (brain abscess (N = 12) and non-abscess (N = 21)). The fluid from the lesion was aspirated at the time of surgery, and the viscosity, viable cell density, and total protein concentration were measured. RESULTS: Signal intensity on FLAIR correlated significantly with the total protein concentration in abscess (r = 0.60, P < 0.05) and non-abscess lesions (r = 0.41, P < 0.05). However, there was no significant difference (P > 0.05) in the FLAIR signal intensity of the abscess (318.8 +/- 75) and non-abscess group (258 +/- 47). The MTR of the brain abscesses (13 +/- 0.95) was significantly higher (P < 0.05) than that of the non-abscess group (3.5 +/- 0.3). A significant correlation was observed between MTR and viscosity (r = 0.75, P < 0.05), total protein concentration (r = 0.60, P < 0.05), and cell density (r = 0.70, P < 0.05) in brain abscess, and viscosity (r = 0.81, P < 0.05) and total protein concentration (r = 0.41, P < 0.05) in non-abscess lesions. CONCLUSION: It is possible to differentiate brain abscesses from non-abscess cystic lesions using MT imaging. The MTR correlates significantly with the viscosity, viable cell density, and total protein concentration in brain abscess, and with viscosity and total protein concentration in non-abscess lesions. FLAIR signal intensity correlates significantly only with the total protein concentration in abscess and non-abscess lesions.

Adolescent↗

PubMed2006

Unusual clinical and MRI features of a cerebellopontine angle medulloepithelioma. Case report and review of literature.

We describe for the first time an unusual location and clinical presentation of medulloepithelioma, a rare embryonal tumor. A 5-year-old child presented with sudden onset of bilateral hearing loss. On imaging, the lesion appeared to be extra axial and was located in the right cerebello-pontine (CP) angle, extending into middle fossa along the trigeminal ganglion and in front of the brain stem into the opposite CP angle. It did not show any enhancement following contrast administration and had restricted diffusion on diffusion-weighted imaging, simulating an epidermoid. However, in vivo localized proton MR spectroscopy revealed a creatine peak dominated by a large choline resonance, peak of glycine with lactate/lipid and invisible N-acetylaspartate suggestive of a neoplastic lesion and not an epidermoid. Only subtotal resection could be performed and the patient had a stormy post-operative course due to extensive dissemination of the disease.

Brain Chemistry↗

PubMed2005

Biological correlates of diffusivity in brain abscess.

Restricted diffusion in brain abscess is assumed to be due to a combination of inflammatory cells, necrotic debris, viscosity, and macromolecules present in the pus. We performed diffusion-weighted imaging (DWI) on 41 patients with proven brain abscesses (36 pyogenic and five tuberculous), and correlated the apparent diffusion coefficient (ADC) from the abscess cavity with viable cell density, viscosity, and extracellular-protein content quantified from the pus. On the basis of the correlation between cell density and ADC in animal tumor models and human tumors in the literature, we assumed that the restricted ADC represents the cellular portion in the abscess cavity. We calculated restricted and unrestricted lesion volumes, and modeled cell density over the restricted area with viable cell density per mm(3) obtained from the pus. The mean restricted ADC in the cavity (0.65 +/- 0.01 x 10(-3) mm(2)/s) correlated inversely with restricted cell density in both the pyogenic (r = -0.90, P = <0.05) and tuberculous (0.60 +/- 0.04 x 10(-3) mm(2)/s, r = -0.94, P = <0.05) abscesses. We conclude that viable cell density is the main biological parameter responsible for restricted diffusion in brain abscess, and it is not influenced by the etiological agents responsible for its causation.

Adolescent↗

PubMed2005

Role of diffusion weighted imaging in differentiation of intracranial tuberculoma and tuberculous abscess from cysticercus granulomas-a report of more than 100 lesions.

Restricted diffusion is noted in a large number of non-stroke conditions including tuberculoma. The purpose of this study was to demonstrate spectrum of diffusion weighted imaging (DWI) abnormalities in tuberculomas and tuberculous abscess and to distinguish these from degenerating neurocysticercosis. Seventy tuberculomas and tuberculous abscesses in 30 patients were categorized in three groups depending on the intensity in the core of the lesion on T2 weighted images. Mean apparent diffusion coefficient (ADC) was calculated from the core as well as from the wall of the lesions. Forty-five lesions of neurocysticercosis in different stage of evolution in 12 patients were also included for comparison. The mean ADC value from the core of the T2 hypointense lesions was significantly higher compared to the wall ((1.24+/-0.32)x10(-3) and (1.06+/-0.15)x10(-3)mm(2)/s, respectively), while mean ADC value from the core of mildly T2 hyperintense lesions was significantly lower compared to the wall ((0.80+/-0.08)x10(-3) and (1.08+/-0.13)x10(-3)mm(2)/s, respectively). Truly T2 hyperintense lesions were divided into two subgroups, tuberculomas and tuberculous abscesses; ADC values from the core and the wall of these lesions were (0.74+/-0.13)x10(-3), (0.61+/-0.08)x10(-3) and (1.03+/-0.14)x10(-3), (1.08+/-0.14)x10(-3)mm(2)/s, respectively, and was significantly lower in core as compared to the wall. However, there was no significant difference between ADC values of the tuberculous abscess and the hyperintense tuberculomas. Vesicular and degenerating stages of cysticercus cysts from the core showed ADC values of (1.66+/-0.29)x10(-3) and (1.51+/-0.23)x10(-3)mm(2)/s, respectively, and were significantly higher than the core of all groups of tuberculomas and tuberculous abscess. We conclude that addition of DWI to routine imaging protocol may help in differentiation of tuberculous lesions from degenerating cysticercus granuloma.

Adult↗

PubMed2005

Diffusion-weighted EPI with magnetization transfer contrast.

Capabilities of diffusion-weighted (DW) and magnetization transfer (MT) imaging are well established for tissue characterization in various pathologies individually. However, the effect of suppression of macromolecules on applying MT pulse on signals associated with DW imaging and resulting change in the apparent diffusion coefficient (ADC) of water molecules has not been demonstrated previously. In the present study, we have performed DW echo planar imaging (EPI) with and without MT preparation pulse to see the effect of macromolecular signal suppression on ADC. A total of 10 normal volunteers and 20 patients with different intracranial cystic lesions [abscesses (n=10), cystic tumors (n=5), arachnoid cysts (n=5)] were subjected to DW imaging (b=0 and 1000 s/mm(2)) with and without MT saturation pulse. Analysis of region of interest (ROI) from different areas of white matter in normal volunteers and in the wall and cavity of cystic lesions in patients was carried out for calculating the ADC values. We found a significant increase (P<.05) in the ADC values in brain parenchyma and cavity of those intracranial cystic lesions having considerable amount of proteins after the application of MT preparation pulse except for arachnoid cysts. This is due to the size of the macromolecules present in the normal and abnormal tissue. Our studies suggest that this technique is likely to give a novel image contrast and may be of value in improving the tissue specificity in pathologies associated with variable macromolecular size.

Adolescent↗

PubMed2005

High fractional anisotropy in brain abscesses versus other cystic intracranial lesions.

BACKGROUND AND PURPOSE: It is known that intracranial mass lesions are relatively isotropic on diffusion-weighted imaging. The purpose of this study is to report an unusually high fractional anisotropy (FA) and mean diffusivity (D(av)) in the cavity of the brain abscess compared with other cystic lesions. METHODS: We performed diffusion tensor imaging (DTI) in 12 patients with cystic intracranial lesions (pyogenic abscess, n = 5; cysticercus cysts, n = 2; and low-grade astrocytoma, n = 5). Mean FA, D(av) from the lesion core, perifocal edema, and corresponding contralateral normal-appearing regions were measured and compared for relative changes in these parameters. In the abscess cases, we placed regions of interest on areas with FA >0.2 and FA <0.2 to get FA and D(av) values. RESULTS: There were two patterns of FA values in the abscess cavity in all five patients. Part of the abscess showed mean FA = 0.440 +/- 0.135, with D(av) = (0.993 +/- 0.185) x 10(-3) mm(2)/s, whereas other parts had FA = 0.131 +/- 0.039 with D(av) = (0.824 +/- 0.183) x 10(-3) mm(2)/s. The cystic tumors and neurocysticercosis showed very high D(av) = (2.806 +/- 0.25, 2.654 +/- 0.35)x 10(-3) mm(2)/s, with low FA = (0.108 +/- 0.037, 0.08 +/- 0.01), respectively. CONCLUSION: Brain abscess cavity shows regions of increased FA values with restricted mean diffusivity compared with other cystic intracranial lesions. This information may prevent misinterpretation of the DTI information as white matter fiber bundle abnormalities associated with mass lesions.

Adolescent↗

PubMedDate not supplied

Role of diffusion-weighted imaging and in vivo proton magnetic resonance spectroscopy in the differential diagnosis of ring-enhancing intracranial cystic mass lesions.

OBJECTIVES: Proton magnetic resonance spectroscopy (PMRS) and diffusion-weighted imaging (DWI) were compared to determine which technique is more effective in the differential diagnosis of cystic intraparenchymal ring-enhancing lesions with variable perifocal edema. METHODS: Fifty-two patients (abscesses [n = 29], tumor cysts [n = 20], and benign cysts [n = 3]) formed the basis for comparative evaluation in this study. The criteria for abscess diagnosis were apparent diffusion coefficient (ADC) values less than 0.9 +/- 1.3 x 10 mm/s and presence of lactate cytosolic amino acids (AAs) with/without succinate, acetate, alanine, and glycine on PMRS. Criteria for nonabscess cyst identification were ADC values of 1.7-3.8 x 10 mm/s and presence of lactate and choline on PMRS. On the basis of these criteria, patients were categorized into abscess (n = 29) and nonabscess (n = 23) groups. Sensitivity and specificity of PMRS and DWI with respect to the final diagnosis were calculated based on the efficacy of these techniques. RESULTS: : Apparent diffusion coefficient values in 21 patients with abscesses were observed within the range of defined criteria, whereas in 8 patients, ADC values were beyond the range of defined criteria. Lactate and AAs with or without other metabolites were observed in 25 of 29 cases of abscesses on PMRS. In the nonabscess group, ADC values of cystic lesions in all patients were consistent with respect to the defined criteria. Only lactate was seen in 14 of 23 patients, whereas both lactate and choline were visible in 6 patients. In 3 patients with neurocysticercosis, AAs (n = 2), lactate (n = 3), acetate (n = 1), succinate (n = 3), choline (n = 2), and alanine (n = 3) were seen. The sensitivity of DWI and PMRS for differentiation of brain abscess from nonbrain abscess was 0.72 and 0.96, respectively, whereas the specificity was 1 for both techniques. CONCLUSION: Demonstration of restricted diffusion on DWI with reduced ADC is highly suggestive of brain abscess; however, in the absence of restriction, PMRS is mandatory to distinguish brain abscesses from cystic tumors.

Acetates↗