Histogram analysis of T2*-based pharmacokinetic imaging in cerebral glioma grading.

BACKGROUND AND OBJECTIVE: To investigate the feasibility of histogram analysis of the T2*-based permeability parameter volume transfer constant (Ktrans) for glioma grading and to explore the diagnostic performance of the histogram analysis of Ktrans and blood plasma volume (vp). METHODS: We recruited 31 and 11 patients with high- and low-grade gliomas, respectively. The histogram parameters of Ktrans and vp, derived from the first-pass pharmacokinetic modeling based on the T2* dynamic susceptibility-weighted contrast-enhanced perfusion-weighted magnetic resonance imaging (T2* DSC-PW-MRI) from the entire tumor volume, were evaluated for differentiating glioma grades. RESULTS: Histogram parameters of Ktrans and vp showed significant differences between high- and low-grade gliomas and exhibited significant correlations with tumor grades. The mean Ktrans derived from the T2* DSC-PW-MRI had the highest sensitivity and specificity for differentiating high-grade gliomas from low-grade gliomas compared with other histogram parameters of Ktrans and vp. CONCLUSIONS: Histogram analysis of T2*-based pharmacokinetic imaging is useful for cerebral glioma grading. The histogram parameters of the entire tumor Ktrans measurement can provide increased accuracy with additional information regarding microvascular permeability changes for identifying high-grade brain tumors.

Post-insult valproate treatment potentially improved functional recovery in patients with acute middle cerebral artery infarction.

Animal stroke models suggest that valproate has multiple neuroprotective mechanisms against ischemic brain damage. This study investigated whether valproate improves functional recovery in patients with acute middle cerebral artery (MCA) infarction. This was an open-label controlled trial. Three to 24 hours after acute MCA infarction, patients were assigned to either the valproate group (n = 17) or the non-valproate group (n = 17). The valproate group received intravenous valproate (400 mg) at enrollment, and then every 12 hours for three days, followed by oral valproate (500 mg) every 12 hours for three months. Neurological function, laboratory data, and brain magnetic resonance imaging were examined at stroke onset, and at two-week and three-month follow-up. No significant differences were observed between the groups with regard to demographics or baseline characteristics. All patients were elderly, had a high pretreatment score on the NIH stroke scale (NIHSS), and slow stroke lesion growth with a final large infarct volume at two-week follow-up. At the three-month follow-up, functional outcome between pre- and post-treatment had improved significantly in the valproate group (NIHSS, p = 0.004; modified Rankin scale (mRS), p = 0.007; Barthel index (BI), p = 0.001). No such improvement was noted in the NIHSS or mRS for the non-valproate group, though mild improvement was seen on the BI (p = 0.022). This open-label trial is the first to demonstrate that valproate treatment markedly improves functional outcome in patients with acute MCA infarction.

Isotropic three-dimensional MRI-Fricke-infused gel dosimetry.

PURPOSE: Fricke-infused gel has been shown to be a simple and attainable method for the conformal measurement of absorbed radiation dose. Nevertheless, its accuracy is seriously hindered by the irreversible ferric ion diffusion during magnetic resonance imaging, particularly when three-dimensional (3D) dose measurement in radiosurgery is considered. In this study, the authors developed a fast three-dimensional spin-echo based Fricke gel dosimetry technique to reduce the adverse effects of ferric ion diffusion and to obtain an accurate isotropic 3D dose measurement. METHODS: A skull shaped phantom containing Fricke-infused gel was irradiated using Leksell Gamma Knife. The rapid image-based dosimetry technique was applied with the use of a 3D fast spin-echo magnetic resonance imaging sequence. The authors mathematically derived and experimentally validated the correlations between dose-response characteristics and parameters of the 3D fast spin-echo MR imaging sequence. Absorbed dose profiles were assessed and compared to the calculated profiles given by the Gamma Knife treatment planning system. Coefficient of variance (CV%) and coefficient of determination (R(2)) were used to evaluate the precision of dose-response curve estimation. The agreement between the measured and the planned 3D dose distributions was quantified by gamma-index analysis of two acceptance criteria. RESULTS: Proper magnetic resonance imaging parameters were explored to render an accurate three-dimensional absorbed dose mapping with a 1 mm(3) isotropic image resolution. The efficacy of the dose-response estimation was approved by an R(2) > 0.99 and an average CV% of 1.6%. Average gamma pass-rate between the experimentally measured and GammaPlan calculated dose distributions were 83.8% and 99.7% for 2%/2 and 3%/3 mm criteria, respectively. CONCLUSIONS: With the designed MR imaging sequence and parameters, total 3D MR acquisition time was confined to within 20 min postirradiation, during which time ferric ion diffusion effects were negligible, thus enabling an accurate 3D radiation dose measurement.

Delayed parkinsonism after CO intoxication: evaluation of the substantia nigra with inversion-recovery MR imaging.

PURPOSE: To quantitatively investigate signal alterations of the substantia nigra in patients with delayed parkinsonism following CO intoxication, as seen on gray matter (GM)-suppressed inversion-recovery (IR) magnetic resonance (MR) images. MATERIALS AND METHODS: This prospective study was approved by the local institutional review board, and written informed consent was obtained from all subjects. Thirteen patients with delayed onset of CO-induced parkinsonism (nine men and four women; mean age, 40.3 years), 13 age-matched CO-intoxicated patients without parkinsonism, and 13 age-matched healthy volunteers were examined with GM-suppressed IR MR imaging. The signal intensity of the substantia nigra was normalized to the adjacent normal-appearing white matter in the temporal lobe, followed by semiautomatic segmentation into medial, middle, and lateral parts by using a skeleton-based algorithm. Multivariate and univariate analyses and Spearman rank correlation test were performed to examine the relationships between variables. Clinical severity was assessed with the modified Hoehn and Yahr rating scale. RESULTS: The normalized signal ratios in the middle and lateral segments of the substantia nigra were significantly higher in those with CO-induced parkinsonism, compared with those with CO intoxication without parkinsonism or normal volunteers (P=.02). For the medial segments, the ratios showed no significant differences among the groups. The normalized signal ratios of substantia nigra were correlated with the severity of parkinsonism, particularly in the lateral segments (ρ=0.927, P<.001). CONCLUSION: CO toxicity to the substantia nigra plays a role in pathophysiologic mechanisms of CO-induced parkinsonism. GM-suppressed IR MR imaging is a useful tool in depicting substantia nigra injury following CO intoxication.

Potential long-term effects of MDMA on the basal ganglia-thalamocortical circuit: a proton MR spectroscopy and diffusion-tensor imaging study.

PURPOSE: To investigate the effects of 3,4-methylenedioxymethamphetamine (MDMA, commonly known as "ecstasy") on the alterations of brain metabolites and anatomic tissue integrity related to the function of the basal ganglia-thalamocortical circuit by using proton magnetic resonance (MR) spectroscopy and diffusion-tensor MR imaging. MATERIALS AND METHODS: This study was approved by a local institutional review board, and written informed consent was obtained from all subjects. Thirty-one long-term (>1 year) MDMA users and 33 healthy subjects were enrolled. Proton MR spectroscopy from the middle frontal cortex and bilateral basal ganglia and whole-brain diffusion-tensor MR imaging were performed with a 3.0-T system. Absolute concentrations of metabolites were computed, and diffusion-tensor data were registered to the International Consortium for Brain Mapping template to facilitate voxel-based group comparison. RESULTS: The mean myo-inositol level in the basal ganglia of MDMA users (left: 4.55 mmol/L ± 2.01 [standard deviation], right: 4.48 mmol/L ± 1.33) was significantly higher than that in control subjects (left: 3.25 mmol/L ± 1.30, right: 3.31 mmol/L ± 1.19) (P < .001). Cumulative lifetime MDMA dose showed a positive correlation with the levels of choline-containing compounds (Cho) in the right basal ganglia (r = 0.47, P = .02). MDMA users also showed a significant increase in fractional anisotropy (FA) in the bilateral thalami and significant changes in water diffusion in several regions related to the basal ganglia-thalamocortical circuit as compared with control subjects (P < .05; cluster size, >50 voxels). CONCLUSION: Increased myo-inositol and Cho concentrations in the basal ganglia of MDMA users are suggestive of glial response to degenerating serotonergic functions. The abnormal metabolic changes in the basal ganglia may consequently affect the inhibitory effect of the basal ganglia to the thalamus, as suggested by the increased FA in the thalamus and abnormal changes in water diffusion in the corresponding basal ganglia-thalamocortical circuit.

Idiopathic growth hormone deficiency in the morphologically normal pituitary gland is associated with perfusion delay.

PURPOSE: To investigate quantitatively the topographic perfusion characteristics of the adenohypophysis by using dynamic contrast material-enhanced magnetic resonance (MR) imaging in a subgroup of patients with idiopathic growth hormone deficiency (IGHD) and with normal-appearing pituitary morphology on MR images. MATERIALS AND METHODS: This HIPAA-compliant, prospective study was approved by an institutional review board, and informed consent was obtained for all patients. Twenty-five patients (mean age, 10.6 years ± 3.3 [standard deviation]) with clinical growth retardation, proved IGHD, and normal pituitary morphology on MR images were included for analysis. Sixteen children (mean age, 10.8 years ± 5.5) were included as control subjects. Time to peak (TTP) perfusion properties of the adenohypophysis in 10 regions of interest from multisection coronal dynamic contrast-enhanced T1-weighted MR images were quantitatively derived by using the Brix pharmacokinetic model. Significant difference was determined with a two-tailed Student t test. The Pearson correlation coefficient was used to correlate the perfusion parameters, including maximal enhancement peak and slope, with serum growth hormone levels in the IGHD group. RESULTS: TTP for the IGHD group was significantly prolonged compared with that for the control group (P < .005). The prolonged TTP in the IGHD group was found to be diffuse. The levels of growth hormone deficiency were negatively correlated with the peak enhancement and the slope of the wash-in phase, which suggests increased blood volume in IGHD within the pituitary gland. CONCLUSION: IGHD and the degree of growth hormone deficiency are associated with nonregional perfusion delay in morphologically normal adenohypophyses. The lack of lateralization of perfusion delay may suggest that microvascular structural abnormalities play a role in IGHD.