Ram K.S. Rathore

Comparative evaluation of corpus callosum DTI metrics in acute mild and moderate traumatic brain injury: Its correlation with neuropsychometric tests

Primary objective: To look for differences in vulnerability of corpus callosum (CC) in patients of mild and moderate traumatic brain injury (TBI) in the acute stage using quantitative diffusion tensor imaging (DTI) and to correlate these with neuropsychometric tests (NPT) done at 6 months post-injury. Research design, methods and procedures: Conventional MRI, DTI and NPT were performed on 83 patients (moderate TBI, n = 57; mild TBI, n = 26) within 5–14 days after TBI. Thirty-three age- and sex-matched healthy controls were also included for comparison. Results: Significantly decreased fractional anisotropy (FA) in genu and splenium; significantly increased radial diffusivity (RD) values in genu, midbody and splenium with significant increase in mean diffusivity (MD) and a decrease in axial diffusivity (AD) only in genu, respectively, in patients with moderate TBI compared to healthy controls were observed. However, in moderate TBI, significantly decreased FA was found only in genu compared to mild TBI. Moderate TBI showed poor NPT scores compared to mild TBI, but this did not reach statistical significance. Conclusions: It is concluded that DTI abnormalities in the regions of CC were more in patients with moderate TBI compared to mild TBI and this was associated with relatively poor neuropsychological outcome 6 months post-injury.

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 mm3 obtained from the pus. The mean restricted ADC in the cavity (0.65 ± 0.01 × 10–3 mm2/s) correlated inversely with restricted cell density in both the pyogenic (r = −0.90, P = <0.05) and tuberculous (0.60 ± 0.04 × 10–3 mm2/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. Magn Reson Med, 2005.

Discriminant analysis to classify glioma grading using dynamic contrast-enhanced MRI and immunohistochemical markers.

IntroductionThe purpose of the present study was to look for the possible predictors which might discriminate between high- and low-grade gliomas by pooling dynamic contrast-enhanced (DCE)-perfusion derived indices and immunohistochemical markers.MethodsDCE-MRI was performed in 76 patients with different grades of gliomas. Perfusion indices, i.e., relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), permeability (ktrans and kep), and leakage (ve) were quantified. MMP-9-, PRL-3-, HIF-1α-, and VEGF-expressing cells were quantified from the excised tumor tissues. Discriminant function analysis using these markers was used to identify discriminatory variables using a stepwise procedure. To look for correlations between immunohistochemical parameters and DCE metrics, Pearsons correlation coefficient was also used.ResultsA discriminant function for differentiating between high- and low-grade tumors was constructed using DCE-MRI-derived rCBV, kep, and ve. The form of the functions estimated are “D1 = 0.642 × rCBV + 0.591 × kep − 1.501 × ve − 1.550” and “D2 = 1.608 × rCBV + 3.033 × kep + 5.508 × ve − 8.784” for low- and high-grade tumors, respectively. This function classified overall 92.1% of the cases correctly (89.1% high-grade tumors and 100% low-grade tumors). In addition, VEGF expression correlated with rCBV and rCBF, whereas MMP-9 expression correlated with kep. A significant positive correlation of HIF-1α with rCBV and VEGF expression was also found.ConclusionDCE-MRI may be used to differentiate between high-grade and low-grade brain tumors non-invasively, which may be helpful in appropriate treatment planning and management of these patients. The correlation of its indices with immunohistochemical markers suggests that this imaging technique is useful in tissue characterization of gliomas.

Quantification of physiological and hemodynamic indices using T1 dynamic contrast-enhanced MRI in intracranial mass lesions

To estimate precontrast tissue parameter (T10) using fast spin echo (FSE) and to quantify physiological and hemodynamic parameters with leakage correction using T1‐weighted dynamic contrast‐enhanced (DCE) perfusion imaging.

Differentiation of infective from neoplastic brain lesions by dynamic contrast-enhanced MRI

IntroductionIt is not always possible to differentiate infective from neoplastic brain lesions with conventional MR imaging. In this study, we assessed the utility of various perfusion indices in the differentiation of infective from neoplastic brain lesions.Methods A total of 103 patients with infective brain lesions (group I, n=26) and neoplastic brain lesions (high-grade glioma, HGG, group II, n=52; low-grade glioma, LGG, group III, n=25) underwent dynamic contrast-enhanced MR imaging. The perfusion indices, including relative cerebral blood volume (rCBV), relative cerebral blood flow (rCBF), transfer coefficient (ktrans) and leakage (ve), were calculated and their degree of correlation with immunohistologically obtained microvessel density (MVD) and vascular endothelial growth factor (VEGF) determined. The rCBV was corrected for the leakage effect. Discriminant analysis for rCBV, rCBF, ktrans and ve was performed to predict the group membership of each case and post hoc analysis was performed to look for group differences.ResultsThe rCBV, rCBF, ktrans, ve, MVD and VEGF were significantly different (P<0.001) between the three groups. Discriminant analysis showed that rCBV predicted 73.1% of the infective lesions, 84.6% of the HGG and 72.0% of the LGG. The rCBF classified 86.5% of the HGG, 80.0% of the LGG and 65.4% of the infective lesions. The ktrans discriminated 98.1% of the HGG, 76.0% of the LGG and 88.5% of the infective lesions correctly. The ve classified 98.1% of the HGG, 76.0% of the LGG and 84.6% the infective lesions. The rCBV was correlated significantly with MVD and VEGF, while the correlation between ktrans and MVD was not significant.ConclusionPhysiological perfusion indices such as ktrans and ve appear to be useful in differentiating infective from neoplastic brain lesions. Adding these indices to the current imaging protocol is likely to improve tissue characterization of these focal brain mass lesions.

Differentiation of calcification from chronic hemorrhage with corrected gradient echo phase imaging

Purpose The purpose of the current study was to prospectively evaluate the role of corrected gradient echo phase imaging in differentiation of calcified granuloma from chronic hemorrhage. Method Eighty-five patients with single/multiple calcifications and hemorrhages irrespective of their location were studied with corrected gradient echo phase imaging. In all the cases, CT was used as the gold standard for the presence/absence of calcification. Results All calcified lesions showed positive phase, whereas chronic hemorrhages showed negative phase in all cases. Five calcified lesions showed no phase shift at TE =15 ms and positive shift at TE = 35 ms. Heterogeneous phase shift was observed in three calcified lesions at TE = 35 ms; all three lesions showed positive phase shift at TE = 15 ms. There was no site-specific problem in differentiation of calcification from chronic hemorrhage including in the basal ganglia. Conclusion We conclude that calcified granuloma can be easily differentiated from chronic hemorrhage with corrected gradient echo phase imaging, which may obviate the need for CT for its confirmation.

Treatment-Induced Plasticity in Cerebral Palsy: A Diffusion Tensor Imaging Study

Diffusion tensor imaging is used as a measure of white-matter organization to probe mechanisms underlying clinical responses. Diffusion tensor imaging and clinical assessment in 8 patients with spastic quadriparesis (mean age, 6.13 years) was performed before and 6 months after therapy (botulinum injection, followed by physiotherapy). All patients were graded on the basis of gross motor function. Serial diffusion tensor imaging was also performed on 10 age/sex-matched controls at baseline and after 6 months. Regions of interests were placed on corticospinal tracts at different levels (i.e., corona radiata, posterior limb of internal capsule, midbrain, pons, and upper medulla) and on other major white-matter tracts, in both patients and controls. A significant increase in fractional anisotropy was evident in corticospinal tracts at the level of the posterior limb of the internal capsule and periventricular white matter of the temporal lobe, relative to baseline values in the patient group. Gross motor function classification system grades improved in all patients during follow-up relative to baseline values. The increase in fractional anisotropy in corticospinal tracts, along with improved clinical motor scores, suggests plasticity of the central motor pathway after combined therapy.

Measurement of cytotoxic and interstitial components of cerebral edema in acute hepatic failure by diffusion tensor imaging

To use diffusion tensor imaging (DTI) metrics for measuring cytotoxic and interstitial components of cerebral edema (CE) in acute hepatic failure (AHF) patients. CE is a major complication in patients with AHF.

Understanding epileptogenesis in calcified neurocysticercosis with perfusion MRI

Objectives: Calcified cysticercus larva with perilesional abnormality is thought to be responsible for seizures in patients with neurocysticercosis (NCC). However, it is not well understood why some calcified cysts are associated with seizures even without perilesional abnormality. Methods: The study group consists of 30 subjects from an ongoing survey for disease burden estimation of a swine farming community who had a single calcified lesion without any perilesional abnormality with or without presentation of seizures. Each group consisted of 15 patients with calcified cysts and was labeled as asymptomatic and symptomatic. We performed dynamic contrast-enhanced (DCE) MRI on all these subjects and determined serum matrix metalloproteinase-9 (MMP-9) levels and MMP-9 gene polymorphisms. Results: DCE-MRI–derived rate transfer constant (kep) and serum MMP-9 levels showed significant differences between symptomatic and asymptomatic subjects. We observed an increase in the MMP-9 levels, kep, and the volume transfer coefficient (ktrans) in these lesions. We also observed a significant increase in MMP-9 (R279Q) gene polymorphism in symptomatic subjects compared with asymptomatic and control subjects. Conclusions: Perilesional inflammation, which varies from symptomatic to asymptomatic subjects, can be quantified using DCE-MRI in calcified cysticercosis and may help distinguish these 2 groups with similar imaging findings. The observed increase in kep with serum MMP-9 levels suggests that the former may serve as a biomarker of MMP-9 levels in these subjects. The significant MMP-9 (R279Q) gene polymorphism in symptomatic subjects might explain the differences in the observed DCE-MRI indices between symptomatic and asymptomatic subjects.

Improved bolus arrival time and arterial input function estimation for tracer kinetic analysis in DCE-MRI.

To develop a methodology for improved estimation of bolus arrival time (BAT) and arterial input function (AIF) which are prerequisites for tracer kinetic analysis of dynamic contrast‐enhanced magnetic resonance imaging (DCE‐MRI) data and to verify the applicability of the same in the case of intracranial lesions (brain tumor and tuberculoma).