The initial focus is on the various sources of bias and variance in the measurement of microvascular parameters and diffusion parameters as such parameters are being used relatively commonly as secondary or exploratory end points in current phase 1/2 see more clinical trails of conventional and targeted therapies. Several ongoing initiatives that seek to identify the magnitude of some of the sources of measurement variations are then discussed. Finally, resources being made available through the National Cancer Institute Reference Image Database to Evaluate Response (RIDER) project that might be of use in investigations of quantitative

MRI biomarker change analysis are described. These resources include 1) data from phantom-based assessment of system response, selleck chemicals llc including short-term (1 hour) and moderate-term (1 week) contrast response and relaxation time measurement, 2) data obtained from repeated dynamic contrast agent-enhanced MRI studies in intracranial tumors,

and 3) data obtained from repeated diffusion MRI studies in both breast and brain. A concluding section briefly discusses issues that must be addressed to allow the transition of MR-based imaging biomarker measures from their current role as secondary/exploratory end points in clinical trials to primary/surrogate markers of response and, ultimately, in clinical application.”
“Analysis and modeling of impedance spectroscopy data of ferroelectric BaTi2O5 single crystal has been carried out at temperatures both below and above the ferroelectric Curie temperature, T-C. The most appropriate equivalent circuit is found to consist of a parallel combination of a resistor (R), capacitor (C), and constant phase element

(CPE). Below TC, the resistance R is too large to measure and the circuit simplifies to C-CPE. Above T-C, R shows Arrhenius behavior with low values of conductivity, MK-8931 eg similar to 4 X 10(-7) S cm(-1) at 800 K and high activation energy, 1.13(2) eV, and represents a thermally activated dc hopping process associated with leakage transport of either electrons or holes through the crystal lattice. C is frequency-independent, passes through a maximum at the ferroelectric-paraelectric transition temperature, T-C similar to 475 degrees C, represents the limiting high frequency capacitance of the crystal and is attributed to the response of the individual dipoles that are responsible for the ferroelectricity. The A parameter of the CPE also passes through a maximum at T-C, is not thermally activated in the same manner as R but shows similar temperature dependence to that of C.