Ferroelectret-based Hydrophone Employed in Oil Identification-A Machine Learning Approach.

This work focuses on acoustic analysis as a way of discriminating mineral oil, providing a robust technique, immune to electromagnetic noise, and in some cases, depending on the applied sensor, a low-cost technique. Thus, we propose a new method for the diagnosis of the quality of mineral oil used in electrical transformers, integrating a ferroelectric-based hydrophone and an acoustic transducer. Our classification solution is based on a supervised machine learning technique applied to the signals generated by an in-home built hydrophone. A total of three statistical datasets entries were collected during the acoustic experiments on four types of oils. The first, the second, and third datasets contain 180, 240, and 420 entries, respectively. Eighty-four features were considered from each dataset to apply to two classification approaches. The first classification approach is able to distinguish the oils from the four possible classes with a classification error less than 2%, while the second approach is able to successfully classify the oils without errors (e.g., with a score of 100%).

Chirp- and random-based coded ultrasonic excitation for localized blood-brain barrier opening.

Chirp- and random-based coded excitation methods have been proposed to reduce standing wave formation and improve focusing of transcranial ultrasound. However, no clear evidence has been shown to support the benefits of these ultrasonic excitation sequences in vivo. This study evaluates the chirp and periodic selection of random frequency (PSRF) coded-excitation methods for opening the blood-brain barrier (BBB) in mice. Three groups of mice (n = 15) were injected with polydisperse microbubbles and sonicated in the caudate putamen using the chirp/PSRF coded (bandwidth: 1.5­1.9 MHz, peak negative pressure: 0.52 MPa, duration: 30 s) or standard ultrasound (frequency: 1.5 MHz, pressure: 0.52 MPa, burst duration: 20 ms, duration: 5 min) sequences. T1-weighted contrast-enhanced MRI scans were performed to quantitatively analyze focused ultrasound induced BBB opening. The mean opening volumes evaluated from the MRI were mm3, mm3and mm3 for the chirp, random and regular sonications, respectively. The mean cavitation levels were V.s, V.s and V.s for the chirp, random and regular sonications, respectively. The chirp and PSRF coded pulsing sequences improved the BBB opening localization by inducing lower cavitation levels and smaller opening volumes compared to results of the regular sonication technique. Larger bandwidths were associated with more focused targeting but were limited by the frequency response of the transducer, the skull attenuation and the microbubbles optimal frequency range. The coded methods could therefore facilitate highly localized drug delivery as well as benefit other transcranial ultrasound techniques that use higher pressure levels and higher precision to induce the necessary bioeffects in a brain region while avoiding damage to the surrounding healthy tissue.

Two-dimensional simulations of displacement accumulation incorporating shear strain.

Using ultrasound images to track large tissue deformations usually requires breaking up the deformation into steps and then summing the resulting displacement estimates. The accumulated displacement estimation error therefore depends not only on the error in each step but also on the statistical relationships between estimation steps. These relationships have not been thoroughly studied. Building on previous work with one-dimensional (1-D) simulations, the work reported here measured error variance for single-step and accumulated displacement estimates using two-dimensional (2-D) numerical simulations of ultrasound echo signals, subjected to both normal and axial shear strain as well as electronic noise. Previous results from 1-D simulations were confirmed, showing that errors due to electronic noise are negatively correlated between steps and accumulate slowly, while errors due to strain are positively correlated and accumulate quickly. These properties hold for both normal and axial shear strain. An analysis of 2-D kernel size for tissue under normal and axial shear strain was also performed. Under axial shear strain, error variance tends to increase with larger lateral kernel sizes but decrease for larger axial kernel sizes; the opposite relationship holds under normal strain. A combination of these two types of strain limits the practical kernel size in both dimensions.

Evaluation of delayed neuronal and axonal damage secondary to moderate and severe traumatic brain injury using quantitative MR imaging techniques.

BACKGROUND AND PURPOSE: Traumatic brain injury (TBI) is a classic model of monophasic neuronal and axonal injury, in which tissue damage mainly occurs at the moment of trauma. There is some evidence of delayed progression of the neuronal and axonal loss. Our purpose was to test the hypothesis that quantitative MR imaging techniques can estimate the biologic changes secondary to delayed neuronal and axonal loss after TBI. MATERIALS AND METHODS: Nine patients (age, 11-28 years; 5 male) who sustained a moderate or severe TBI were evaluated at a mean of 3.1 years after trauma. We applied the following techniques: bicaudate (BCR) and bifrontal (BFR) ventricle-to-brain ratios; T2 relaxometry; magnetization transfer ratio (MTR); apparent diffusion coefficient (ADC); and proton spectroscopy, by using an N-acetylaspartate/creatine (NAA/Cr) ratio measured in normal-appearing white matter (NAWM) and the corpus callosum (CC). The results were compared with those of a control group. RESULTS: BCR and BFR mean values were significantly increased (P < or = .05) in patients due to secondary subcortical atrophy; increased T2 relaxation time was observed in the NAWM and CC, reflecting an increase in water concentration secondary to axonal loss. Increased ADC mean values and reduced MTR mean values were found in the NAWM and CC, showing damage in the myelinated axonal fibers; and decreased NAA/Cr ratio mean values were found in the CC, indicating axonal loss. CONCLUSIONS: These quantitative MR imaging techniques could noninvasively demonstrate the neuronal and axonal damage in the NAWM and CC of human brains, secondary to moderate or severe TBI.

Spatiotemporal evaluation of human colon motility using three-axis fluxgates and magnetic markers.

An alternative method to study the mechanical activity of the human colon in fasting and postprandial states is presented. The method is based on measurements of the magnetic fields produced by a magnetic marker, a small cylindrical NdBFe magnet, when it was ingested by the subjects. A portable magnetic probe, consisting of two digital three-axis fluxgate magnetometers, arranged in a first-order electronic gradiometer, was implemented for this research. Measurements were taken in 16 healthy male subjects. Contractile activity frequency measurements were taken along the colon length, including the ascending, transverse and descending sections, as well as the rectal sigmoidal section. Values for the contractile activity frequency of 2-5 cycles min(-1) were measured. The set-up is simple, low-cost and suitable for use in an unshielded environment.

Euterpe Olerácea (Açaí) as an alternative oral contrast agent in MRI of the gastrointestinal system: preliminary results.

Using contrast agents is a common practice in medical imaging protocols. Paramagnetic properties of certain compounds present in contrast agents can affect magnetic resonance imaging (MRI) signals. For abdominal applications, they are usually injected, but may also be administered orally. However, their use as a routine technique is limited, mainly due to the lack of appropriate oral contrast agents. We herein present the preliminary characterization and results for implementation of Euterpe Olerácea (popularly named Açaí) as a possible clinical oral contrast agent for MRI of the gastrointestinal tract. The pulp of Açaí, a fruit from the Amazon area, presented an increase in T(1)-weighted MRI signal, equivalent to that of gadolinium-diethyltriamine pentaacetic acid, and a decrease in T(2)-weighted images. We looked for intrinsic properties that could be responsible for the T(1) signal enhancement and T(2) opacification. Atomic absorption spectra revealed the presence of Fe, Mn and Cu ions in Açai. The presence of such ions contribute to the susceptometric value found of chi = -4.83 x 10(-6). This finding assents with the hypothesis that image contrast changes were due to the presence of paramagnetic material. The first measurements in vivo demonstrate a clear increase of contrast, in T(1)-weighted images, due to the presence of Açaí. Consistently, the opacification in a T(2)-weighted acquisition was evident, revealing a good contrast on bowel walls of gastric tissues.

Theoretical evaluation of the susceptometric measurement of iron in human liver by four different susceptometers.

This paper is an evaluation of liver iron quantification using a simulated magnetic susceptibility measurement in the hepatic region. Susceptometers having homogeneous and non-homogeneous magnetizing fields coupled with axial second-order and planar first-order gradiometric magnetic detectors were considered. The intensity of magnetic flux threading the detector coils was evaluated considering samples with volume and susceptibility equivalent to liver iron, tissue and lung air individually. These volumes were represented by cylindrical and spherical geometries. The main sources of error in quantifying iron overload in susceptometric measurement of hepatic tissue were evaluated for four configurations of the susceptometer.