magnetization transfer (MT) measurements were performed in vitro at 3 T and 37°C on a variety of tissues: mouse liver, muscle, and heart; rat spinal cord and kidney; bovine optic nerve, cartilage, and white and gray matter; and human blood. The MR parameters were compared to those at 1.5 T. As expected, the T 2 relaxation time constants and quantitative MT parameters (MT exchange rate, R, macromolecular pool fraction, M 0B , and macromolecular T 2 relaxation time, T 2B ) at 3 T were similar to those at 1.5 T. Longitudinal, T 1 , and transverse, T 2 , relaxation time measurements are relevant in understanding water molecular dynamics in biologic systems. T 1 , T 2 relaxation times and MT depend on the chemical and physical environments of water protons in tissue. MRI contrast between normal and pathologic tissue is often based on differences in tissue microstructure and, therefore, different T 1 and T 2 relaxation times. Moreover, T 1 , T 2 , and MT provide quantitative assessment of tissue pathology. In particular, they offer additional information about the processes of demyelination and axonal loss (1-4), inflammation (5), infarction (6), white matter edema (7), tumor malignancy (8), and ischemia (9). Both tissue relaxation and MT parameter estimates are important in designing MRI pulse sequences that aim to accentuate contrast between normal and pathologic tissue. Since MRI at higher fields (particularly 3 T) has become more common, it is important to evaluate MR parameters of tissue quantitatively to determine MRI sequence parameters, such as TE (echo time), TR (repetition time), or MT saturation schemes, that provide an optimal contrast. The literature data regarding MR parameters at high fields (such as 3 T) is surprisingly limited. The goal of this study is to provide a comprehensive evaluation of MR parameters at 3 T to serve as reference for further MRI pulse sequence optimization. Therefore, T 1 and T 2 relaxation, and MT parameters at 3 T and 37°C for a wide range of tissues: liver, muscle, optic nerve, spinal cord, heart, kidney, white (corpus callosum) and gray matter (brain cortex), cartilage, and blood were measured and compared to those at 1.5 T. EXPERIMENTAL METHODS MR MeasurementsAll 3 T, MR measurements were performed at 37°C using a research-dedicated, whole body GE SIGNA magnet. MR pulse sequences and data acquisition were controlled by an NMR spectroscopy console (SMIS, Surrey, England). Rectangular radiofrequency (RF) pulses were transmitted by an RF amplifier (American Microwave Technology, Brea, CA; model 3205) and solenoid RF coil designed to accommodate in vitro tissue measurements in test tubes (9 turns, 8 mm in diameter, 15 mm length). Immediately after tissue excision, the samples (approximately 300 L by volume) were immersed in non-protonated, MR-compatible fluid (Fluorinert; 3M, London, Canada) to avoid dehydration and reduce magnetic susceptibility effects. Temperature was controlled by an air-flow mechanism with MR-compatible thermocouple (Luxtron) inserted into the measured sam...

One of the issues facing credit card fraud detection systems is that a significant percentage of transactions labeled as fraudulent are in fact legitimate. These "false alarms" delay the detection of fraudulent transactions and can cause unnecessary concerns for customers. In this study, over 1 million unique credit card transactions from 11 months of data from a large Canadian bank were analyzed. A meta-classifier model was applied to the transactions after being analyzed by the Bank's existing neural network based fraud detection algorithm. This meta-classifier model consists of 3 base classifiers constructed using the decision tree, naïve Bayesian, and k-nearest neighbour algorithms. The naïve Bayesian algorithm was also used as the meta-level algorithm to combine the base classifier predictions to produce the final classifier. Results from the research show that when a metaclassifier was deployed in series with the Bank's existing fraud detection algorithm improvements of up to 28% to their existing system can be achieved.