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BURLINGTON, MA, United States

Numerous improvements in HIV testing technology led recently to the first revision of recommendations for diagnostic laboratory testing in the USA in 25 years. Developments in HIV testing continue to produce tests that identify HIV infection earlier with faster turnaround times for test results. These play an important role in identifying HIV infection during the highly infectious acute phase, which has implication for both patient management and public health interventions to control the spread of HIV. Access to these developments, however, is often delayed by the regulatory apparatus for approval and oversight of HIV testing in the USA. This article summarizes recent developments in HIV diagnostic testing technology, outlines their implications for clinical management and public health, describes current systems of regulatory oversight for HIV testing in the USA, and proposes alternatives that could expedite access to improved tests as they become available. © 2015, Springer Science+Business Media New York. Source

Khan S.,Dartmouth College | Manwaring P.,Dartmouth College | Manwaring P.,Domain Surgical | Borsic A.,Dartmouth College | And 2 more authors.
IEEE Transactions on Medical Imaging

Electrical impedance tomography (EIT) is used to image the electrical property distribution of a tissue under test. An EIT system comprises complex hardware and software modules, which are typically designed for a specific application. Upgrading these modules is a time-consuming process, and requires rigorous testing to ensure proper functioning of new modules with the existing ones. To this end, we developed a modular and reconfigurable data acquisition (DAQ) system using National Instruments' (NI) hardware and software modules, which offer inherent compatibility over generations of hardware and software revisions. The system can be configured to use up to 32-channels. This EIT system can be used to interchangeably apply current or voltage signal, and measure the tissue response in a semi-parallel fashion. A novel signal averaging algorithm, and 512-point fast Fourier transform (FFT) computation block was implemented on the FPGA. FFT output bins were classified as signal or noise. Signal bins constitute a tissue's response to a pure or mixed tone signal. Signal bins' data can be used for traditional applications, as well as synchronous frequency-difference imaging. Noise bins were used to compute noise power on the FPGA. Noise power represents a metric of signal quality, and can be used to ensure proper tissue-electrode contact. Allocation of these computationally expensive tasks to the FPGA reduced the required bandwidth between PC, and the FPGA for high frame rate EIT. In 16-channel configuration, with a signal-averaging factor of 8, the DAQ frame rate at 100 kHz exceeded 110 frames s-1, and signal-to-noise ratio exceeded 90 dB across the spectrum. Reciprocity error was found to be < 1\% for frequencies up to 1 MHz. Static imaging experiments were performed on a high-conductivity inclusion placed in a saline filled tank; the inclusion was clearly localized in the reconstructions obtained for both absolute current and voltage mode data. © 2014 IEEE. Source

Butler K.S.,University of New Mexico | Adolphi N.L.,University of New Mexico | Bryant H.C.,University of New Mexico | Lovato D.M.,University of New Mexico | And 2 more authors.
Physics in Medicine and Biology

As new magnetic nanoparticle-based technologies are developed and new target cells are identified, there is a critical need to understand the features important for magnetic isolation of specific cells in fluids, an increasingly important tool in disease research and diagnosis. To investigate magnetic cell collection, cell-sized spherical microparticles, coated with superparamagnetic nanoparticles, were suspended in (1) glycerine-water solutions, chosen to approximate the range of viscosities of bone marrow, and (2) water in which 3, 5, 10 and 100% of the total suspended microspheres are coated with magnetic nanoparticles, to model collection of rare magnetic nanoparticle-coated cells from a mixture of cells in a fluid. The magnetic microspheres were collected on a magnetic needle, and we demonstrate that the collection efficiency versus time can be modeled using a simple, heuristically-derived function, with three physically-significant parameters. The function enables experimentally-obtained collection efficiencies to be scaled to extract the effective drag of the suspending medium. The results of this analysis demonstrate that the effective drag scales linearly with fluid viscosity, as expected. Surprisingly, increasing the number of non-magnetic microspheres in the suspending fluid results increases the collection of magnetic microspheres, corresponding to a decrease in the effective drag of the medium. © 2014 Institute of Physics and Engineering in Medicine. Source

Borsic A.,Ne Scientific, Llc | Perreard I.,Dartmouth Hitchcock Medical Center | Mahara A.,Dartmouth College | Halter R.J.,Dartmouth College
IEEE Transactions on Medical Imaging

Magnetic Resonance-Electrical Properties Tomography (MR-EPT) is an imaging modality that maps the spatial distribution of the electrical conductivity and permittivity using standard MRI systems. The presence of a body within the scanner alters the RF field, and by mapping these alterations it is possible to recover the electrical properties. The field is time-harmonic, and can be described by the Helmholtz equation. Approximations to this equation have been previously used to estimate conductivity and permittivity in terms of first or second derivatives of RF field data. Using these same approximations, an inverse approach to solving the MR-EPT problem is presented here that leverages a forward model for describing the magnitude and phase of the field within the imaging domain, and a fitting approach for estimating the electrical properties distribution. The advantages of this approach are that 1) differentiation of the measured data is not required, thus reducing noise sensitivity, and 2) different regularization schemes can be adopted, depending on prior knowledge of the distribution of conductivity or permittivity, leading to improved image quality. To demonstrate the developed approach, both Quadratic (QR) and Total Variation (TV) regularization methods were implemented and evaluated through numerical simulation and experimentally acquired data. The proposed inverse approach to MR-EPT reconstruction correctly identifies contrasts and accurately reconstructs the geometry in both simulations and experiments. The TV regularized scheme reconstructs sharp spatial transitions, which are difficult to reconstruct with other, more traditional approaches. © 2015 IEEE. Source

Borsic A.,Ne Scientific, Llc | Helisch A.,Dartmouth Hitchcock Medical Center
Proceedings of the IEEE Annual Northeast Bioengineering Conference, NEBEC

In this paper we present results relative to speeding up multiscale vessel enhancement filters for angiography images by using Graphic Processing Units (GPUs). These filters, proposed initially by Frangi [1], can be used to preferentially enhance image features that have a tubular-like structure, and therefore result in the enhancement of vessels. Vessel enhancement filters are used commonly as a pre-processing step for vessel segmentation. As this process is computationally and memory intensive, filtering high-resolution 3D micro-CT (mCT) images can take several hours. We propose a method for speeding up this process using GPUs which results in significant speed gains and which is memory efficient. © 2014 IEEE. Source

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