The ISMRM Open Science Initiative for Perfusion Imaging (OSIPI): Results from the OSIPI-Dynamic Contrast-Enhanced challenge.

PURPOSE: K trans $$ {K}^{\mathrm{trans}} $$ has often been proposed as a quantitative imaging biomarker for diagnosis, prognosis, and treatment response assessment for various tumors. None of the many software tools for K trans $$ {K}^{\mathrm{trans}} $$ quantification are standardized. The ISMRM Open Science Initiative for Perfusion Imaging-Dynamic Contrast-Enhanced (OSIPI-DCE) challenge was designed to benchmark methods to better help the efforts to standardize K trans $$ {K}^{\mathrm{trans}} $$ measurement. METHODS: A framework was created to evaluate K trans $$ {K}^{\mathrm{trans}} $$ values produced by DCE-MRI analysis pipelines to enable benchmarking. The perfusion MRI community was invited to apply their pipelines for K trans $$ {K}^{\mathrm{trans}} $$ quantification in glioblastoma from clinical and synthetic patients. Submissions were required to include the entrants' K trans $$ {K}^{\mathrm{trans}} $$ values, the applied software, and a standard operating procedure. These were evaluated using the proposed OSIP I gold $$ \mathrm{OSIP}{\mathrm{I}}_{\mathrm{gold}} $$ score defined with accuracy, repeatability, and reproducibility components. RESULTS: Across the 10 received submissions, the OSIP I gold $$ \mathrm{OSIP}{\mathrm{I}}_{\mathrm{gold}} $$ score ranged from 28% to 78% with a 59% median. The accuracy, repeatability, and reproducibility scores ranged from 0.54 to 0.92, 0.64 to 0.86, and 0.65 to 1.00, respectively (0-1 = lowest-highest). Manual arterial input function selection markedly affected the reproducibility and showed greater variability in K trans $$ {K}^{\mathrm{trans}} $$ analysis than automated methods. Furthermore, provision of a detailed standard operating procedure was critical for higher reproducibility. CONCLUSIONS: This study reports results from the OSIPI-DCE challenge and highlights the high inter-software variability within K trans $$ {K}^{\mathrm{trans}} $$ estimation, providing a framework for ongoing benchmarking against the scores presented. Through this challenge, the participating teams were ranked based on the performance of their software tools in the particular setting of this challenge. In a real-world clinical setting, many of these tools may perform differently with different benchmarking methodology.

Aggregates of Ni/Ni(OH)2/NiOOH Nanoworms on Carbon Cloth for Electrocatalytic Hydrogen Evolution.

The development of an efficient electrocatalyst for hydrogen evolution reaction (HER) is essential to facilitate the practical application of water splitting. Here, we aim to develop an electrocatalyst, Ni/Ni(OH)2/NiOOH, via electrodeposition technique on carbon cloth, which shows efficient activity and durability for HER in an alkaline medium. Phase purity and morphology of the electrodeposited catalyst are determined using powder X-ray diffraction and electron microscopic techniques. The compositional and thermal stability of the catalyst is checked using X-ray photoelectron spectroscopy and thermogravimetry analysis. Electrodeposited Ni/Ni(OH)2/NiOOH material is an efficient, stable, and low-cost electrocatalyst for hydrogen evolution reaction in a 1.0 M KOH medium. The catalyst exhibits remarkable performance, achieving a current density of 10 mA/cm2 at a potential of -0.045 V vs reversible hydrogen electrode (RHE), and the Tafel slope value is 99.6 mV/dec. The overall electrocatalytic water splitting mechanism using Ni/Ni(OH)2/NiOOH catalyst is well explained, where formation and desorption of OH- ion on the catalyst surface are significant at alkaline pH. The developed electrocatalyst shows significant durability up to 200 h in a negative potential window in a highly corrosive alkaline environment along with efficient activity. The electrocatalyst can generate 165.6 µmol of H2 in ∼145 min of reaction time with 81.5% faradic efficiency.

Subcompartmentalization of extracellular extravascular space (EES) into permeability and leaky space with local arterial input function (AIF) results in improved discrimination between high- and low-grade glioma using dynamic contrast-enhanced (DCE) MRI.

PURPOSE: To modify the generalized tracer kinetic model (GTKM) by introducing an additional tissue uptake leakage compartment in extracellular extravascular space (LTKM). In addition, an implicit determination of voxel-wise local arterial input function (AIF) Cp (t) was performed to see whether these changes help in better discrimination between low- and high-grade glioma using dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI). MATERIALS AND METHODS: The modified model (LTKM) was explored and fitted to the concentration-time curve C(t) of each voxel, in which the local AIF Cp (t) could be estimated by a time invariant convolution approximation based on a separately measured global AIF Ca (t). A comparative study of tracer kinetic analysis was performed on 184 glioma patients using DCE-MRI data on 1.5T and 3T MRI systems. RESULTS: The LTKM analysis provided more accurate pharmacokinetic parameters as evidenced by their relative constancy with respect to the length of concentration-time curve used. In addition, LTKM with local AIF resulted in improved discrimination between low-grade and high-grade gliomas. CONCLUSION: LTKM with local AIF provides more accurate estimation of physiological parameters and improves discrimination between low-grade and high-grade gliomas as compared with GTKM.

Quantification of physiological and hemodynamic indices using T(1) dynamic contrast-enhanced MRI in intracranial mass lesions.

PURPOSE: To estimate precontrast tissue parameter (T(10)) using fast spin echo (FSE) and to quantify physiological and hemodynamic parameters with leakage correction using T(1)-weighted dynamic contrast-enhanced (DCE) perfusion imaging. MATERIALS AND METHODS: Voxel-wise T(10) computation was performed followed by the analysis of T(1)-weighted DCE perfusion data for the conversion of signal intensity time curve to concentration time curve, estimation of hemodynamic and physiological perfusion indices, and a method for leakage correction. Validations of accuracy of the computations have also been carried out. RESULTS: The computed T(10) and hemodynamic perfusion indices in normal white and gray matter were in good agreement with the literature values. Physiological perfusion indices in these regions were found negligible, validating computations. Cerebral blood volume (CBV) values change negligibly over the length of concentration time curve in white matter, gray matter, and lesion (CBV(corrected)), while CBV(uncorrected) (lesion) shows linear increase over time. CONCLUSION: T(1)-weighted DCE perfusion data along with FSE-based T(1) estimation can be used for an accurate estimation of hemodynamic and physiological perfusion indices.

Increased anisotropy in neonatal meningitis: an indicator of meningeal inflammation.

INTRODUCTION: Increased anisotropy in brain abscesses has been shown to be due to adhesion of inflammatory cells and is suggestive of an active inflammatory process. The objective of this study was to determine if similar changes occur in the pia-arachnoid on the surface of the cerebral cortex in patients with pyogenic meningitis, and if these changes regress following antibiotic therapy. METHODS: Diffusion tensor imaging (DTI) was performed on 14 term neonates (mean age 13 days) with bacterial meningitis and 10 healthy age- and sex-matched controls. Regions of interest (ROIs) were placed on areas including the leptomeninges, the cerebral cortex and adjoining subcortical white matter for quantitation of mean fractional anisotropy (FA) and diffusivity (MD) values. Follow-up MRI was performed in five of the neonates in the patient group after 2 weeks of antibiotic treatment. FA and MD values were compared in patients before and after antibiotic treatment as well as with those in the healthy controls. RESULTS: Significantly higher FA values but no difference in MD values were observed in the patient group as compared to the healthy controls at both time points (before and after antibiotic treatment). Significantly decreased FA values in the frontal, occipital and temporal cortical regions were observed in patients following antibiotic treatment. CONCLUSION: DTI-derived FA may be of value in the noninvasive assessment of meningeal inflammatory activity and treatment response in neonates.

Relative cerebral blood volume is a measure of angiogenesis in brain tuberculoma.

OBJECTIVE: The aim of this study was to correlate the perfusion indices with magnetic resonance imaging-derived cellular and necrotic fraction of the tuberculoma and angiogenesis metrics on histopathology. METHODS: We performed dynamic contrast-enhanced magnetic resonance imaging in 13 excised brain tuberculoma patients. Microvascular density and vascular endothelial growth factor (VEGF)-expressing cells were quantified from the excised tuberculoma. The cellular and necrotic fractions of the tuberculomas were quantified on a postcontrast T1-weighted imaging. RESULTS: Relative cerebral blood volume of cellular portion significantly correlated with cellular fraction volume (r = 0.882, P < 0.001), microvascular density (r = 0.900, P < 0.001), and VEGF (r = 0.886, P < 0.001) of the 13 excised tuberculomas. Microvascular density also correlated significantly with VEGF (r = 0.919, P < 0.001). CONCLUSIONS: Relative cerebral blood volume is a measure of angiogenesis in the cellular fraction of the brain tuberculoma. This information may be of value in predicting the therapeutic response in future.

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.