Generalized overlap measures for evaluation and validation in medical image analysis

Measures of overlap of labelled regions of images, such as the Dice and Tanimoto coefficients, have been extensively used to evaluate image registration and segmentation algorithms. Modern studies can include multiple labels defined on multiple images yet most evaluation schemes report one overlap per labelled region, simply averaged over multiple images. In this paper, common overlap measures are generalized to measure the total overlap of ensembles of labels defined on multiple test images and account for fractional labels using fuzzy set theory. This framework allows a single "figure-of-merit" to be reported which summarises the results of a complex experiment by image pair, by label or overall. A complementary measure of error, the overlap distance, is defined which captures the spatial extent of the nonoverlapping part and is related to the Hausdorff distance computed on grey level images. The generalized overlap measures are validated on synthetic images for which the overlap can be computed analytically and used as similarity measures in nonrigid registration of three-dimensional magnetic resonance imaging (MRI) brain images. Finally, a pragmatic segmentation ground truth is constructed by registering a magnetic resonance atlas brain to 20 individual scans, and used with the overlap measures to evaluate publicly available brain segmentation algorithms.     

0.75 V supply nanowatt resistorless sub-bandgap curvature-compensated CMOS voltage reference

This work presents a resistorless self-biased and small area sub-bandgap voltage reference that works in the nano-ampere consumption range with 0.75 V of power supply. The circuit applies a curvature compensation technique that allows an extended temperature range without compromising the temperature stability. The behavior of the circuit is analytically described, and a design methodology is proposed which allows the separate adjustment of the bipolar junction transistor bias current and its curvature compensation. Simulation results are presented for a 180 nm CMOS process, where a reference voltage of 469 mV is designed, with a temperature coefficient of 5 ppm/°C for the ?40 to 125 °C extended temperature range. The power consumption of the whole circuit is 16.3 nW under a 0.75 V power supply at 27 °C. The estimated silicon area is 0.0053 mm².     

Antioxidant and antibacterial activities of a starch film with bioextracts microencapsulated from cactus fruits (Opuntia oligacantha)

Food Science and Biotechnology - The use of unconventional sources is very relevant in the food area. In the present study the development of active films with the addition of bioextract (BE) or...     

Prevalence and antimicrobial resistance of Salmonella recovered from processed poultry

This study was conducted to determine the prevalence and antimicrobial resistance of Salmonella isolates recovered from processed poultry. Four hundred eighty pre- and postchill whole broiler chicken carcasses were collected from a poultry processing plant between July 2004 and June 2005. Water samples also were collected at the entrance and exit of the chiller. After preenrichment, carcass and water samples were analyzed for the presence of Salmonella using the automated BAX system followed by traditional culture methods. The proportions of pre- and postchill carcasses that were positive for Salmonella were 88.4 and 84.1%, respectively. Ninety-two percent of water samples collected at the entrance of the chiller were positive for Salmonella, but all exit samples were negative. There was no significant difference in the prevalence of Salmonella between pre- and postchill carcasses (P > 0.05). Salmonella isolates recovered were serotyped and tested for susceptibility to antimicrobials. Thirteen serotypes were identified; the most common were Salmonella Kentucky (59.5%) and Salmonella Typhimurium (17.8%). Three hundred thirty-nine (79.8%) of the isolates were resistant to at least one antimicrobial, and 53.4% were resistant to three or more antimicrobials. Resistance was most often observed to tetracycline (73.4% of isolates), ampicillin (52.9%), amoxicillin-clavulanic acid (52%), ceftiofur (51.7%), streptomycin (35.2%), and sulfisoxazole (21.8%). These results indicate the high prevalence of Salmonella contamination in whole broiler carcasses, and a large number of these Salmonella isolates were resistant to commonly used antimicrobials.     

Response surface models for effects of temperature, pH, and previous growth pH on growth kinetics of Salmonella Typhimurium in brain heart infusion broth

Response surface models were developed for effects of temperature (15 to 40 degrees C), pH (5.2 to 7.4), and previous growth pH (5.7 to 8.6) on lag time (lambda) and specific growth rate (mu) of Salmonella Typhimurium in brain heart infusion broth (BHIB). Seventy-five growth curves for model development and 30 growth curves for model validation were fit to a two-phase linear growth model to obtain direct estimates of lambda and mu of Salmonella Typhimurium in BHIB. Response surface models for natural logarithm transformations of lambda and mu as a function of temperature, pH, and previous growth pH were obtained by regression analysis. Previous growth pH did not alter (P > 0.05) or interact with temperature or pH to alter subsequent growth kinetics of Salmonella Typhimurium. However, lambda and mu of Salmonella Typhimurium in BHIB were affected (P < 0.05) by linear and quadratic effects of temperature and pH. The models were validated against data not used in their development. Mean absolute relative error of predictions (model accuracy) was 7.8% for lambda and 6.6% for mu. Median relative error of predictions (model bias) was -1.8% for lambda and -2.8% for mu. Results of the current study indicated that the models developed accurately predicted growth kinetics of Salmonella Typhimurium in BHIB within the matrix of factors modeled and that the range of previous growth pH (5.7 to 8.6) investigated did not alter the subsequent growth kinetics of Salmonella Typhimurium in BHIB.     

Description of the kinetic enzymatic browning in banana (Musa cavendish) slices using non-uniform color information from digital images

A novel methodology “fractal browning indicator” (FBI) is presented, that describes the enzymatic browning kinetic based on the use of irregular color patterns from banana slice images. It uses the fractal Fourier texture image value in a selected area, to calculate a fractal dimension (FD), which represents the complexity of color distribution. During the procedure, colors from digital images were first transformed to L^*a^*b^* space color using a transformation function (quadratic model), in order to derivate three color channels, lightness (L^*), redness (a^*), and yellowness (b^*). In the results, lightness and yellowness parameters decreased during the browning kinetic, when their respective FD values increased, indicating major color distribution complexity in a selected area analyzed during the kinetic. The redness color (a^*) did not show any statistical variation. The empirical power law model was suitable to correlate enzymatic browning kinetic data both for FBI and for the traditional method (when an L^* mean was used). However, enzymatic browning rates using the FBI method, were between 8.5 and 35 times higher than rates calculated with the traditional method.     

A filtration-based real-time PCR method for the quantitative detection of viable Salmonella enterica and Listeria monocytogenes in food samples

We developed a novel filtration-based method that can eliminate dead or severally damaged Salmonella enterica and Listeria monocytogenes in food samples. This new method can recover all viable bacteria in less than 30 min, and can be coupled with a subsequent bacterial DNA extraction and real-time PCR. No statically significant differences (p < 0.01) were found between real-time PCR results obtained separately from S. enterica and L. monocytogenes when different ratios of living and dead cells were used. The analytical sensitivity in both cases was 1 genome equivalent (GE), and the quantification was linear (R² > 0.9969) over a 5-log dynamic range with PCR efficiencies >0.9754. When compared with the standard microbiological methods for the detection of these foodborne pathogens, the relative accuracy was excellent ranging from 95.72% to 104.48%. Finally, we applied the pre-treatment method to the direct detection of viable forms of these foodborne pathogens in food samples using yogurt as a model, the results being similar to those obtained using pure cultures.     

Design of whey protein nanostructures for incorporation and release of nutraceutical compounds in food

Whey proteins are widely used as nutritional and functional ingredients in formulated foods because they are relatively inexpensive, generally recognized as safe (GRAS) ingredient, and possess important biological, physical, and chemical functionalities. Denaturation and aggregation behavior of these proteins is of particular relevance toward manufacture of novel nanostructures with a number of potential uses. When these processes are properly engineered and controlled, whey proteins may be formed into nanohydrogels, nanofibrils, or nanotubes and be used as carrier of bioactive compounds. This review intends to discuss the latest understandings of nanoscale phenomena of whey protein denaturation and aggregation that may contribute for the design of protein nanostructures. Whey protein aggregation and gelation pathways under different processing and environmental conditions such as microwave heating, high voltage, and moderate electrical fields, high pressure, temperature, pH, and ionic strength were critically assessed. Moreover, several potential applications of nanohydrogels, nanofibrils, and nanotubes for controlled release of nutraceutical compounds (e.g. probiotics, vitamins, antioxidants, and peptides) were also included. Controlling the size of protein networks at nanoscale through application of different processing and environmental conditions can open perspectives for development of nanostructures with new or improved functionalities for incorporation and release of nutraceuticals in food matrices.