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Quantitatively assessing the tissue stiffness with acoustic radiation force impulse (ARFI) method has proved its worth in clinical trials. Much attention has been focused on the research of the displacement estimation algorithm in ARFI. However, the subsequent shear wave speed estimation part can also affect the accuracy and reliability of the results. In this study, several algorithms for shear wave...
One to five transvaginal ultrasound scans were taken of 63 women to estimate the microstructural changes in cervix using ultrasonic attenuation. Spectral log difference algorithm showed a clear decrease in attenuation as the time to delivery comes closer. The decrease in attenuation occurs earlier in preterm birth compared to full term birth which can be used as a predictor for preterm birth. Attenuation...
Magnetic guide of endovascular devices or magnetized therapeutic microparticles to the specific target in the arterial tree is increasingly studied, since it could improve treatment efficacy and reduce side effects. Most proposed systems use external permanent magnets attached to robotic manipulators or magnetic resonance imaging (MRI) systems to guide internal carriers to the region of treatment...
Needle lifting and thrusting manipulation is one of common skills in acupuncture. However, there exists artificial error in frequency and amplitude due to individual difference when performing lifting and thrusting during acupuncture. For providing stable and quantified effects and higher frequency when doing lifting and thrusting manipulation, a well controlled device is needed. The aim of this article...
This paper reports diffusion weighted MRI measurements of cyclohexane in a novel diffusion tensor MRI phantom composed of hollow coaxial electrospun fibers (average diameter 10.2 μm). Recent studies of the phantom demonstrated its potential as a calibration standard at low b values (less than 1000 s/mm2) for mean diffusivity and fractional anisotropy. In this paper, we extend the characterization...
Recent investigations considering flexible, steer-able needles for minimally invasive surgery have shown the significance of needle shape in determining the needle-tissue interactions leading to the access of targets. Digital Image Correlation has enabled internal deformation and strain caused by needle insertions to be seen in a soft tissue phantom at high resolution for the first time. Here, the...
While mammography remains the gold standard for breast cancer screening, additional adjunctive tools for early detection of breast cancer are needed especially for young women, women with dense breast tissue and those at increased risk due to genetic factors. These patient populations, along with those populations for whom mammography is not readily available, require alternative technologies capable...
In this study, current density (J) — based Magnetic Resonance Conductivity Tensor Imaging (MRCTI) reconstruction algorithms namely, the Anisotropic Equipotential Projection (AEPP), the Anisotropic J-Substitution (AJS) and the Anisotropic Hybrid J-Substitution (AHJS) algorithms are implemented to reconstruct conductivity tensor images of a physical phantom using a 3T magnetic resonance imaging system...
An element design for receive array coils that decouples from the transmit coil without external active detuning is presented for magnetic resonance imaging (MRI) of mice. The array element uses a crisscrossed geometry on the return paths to reduce the current induced by the transmit coil. Without the need for an external active detune network, the proposed method simplifies the construction of MRI...
MRI has been used for imaging interventional procedures with devices such as brachytherapy seeds, biopsy needles, markers, and stents. However, the high susceptibility of these devices leads to signal loss and distortion in the MRI images. Previously, we proposed a method to generate positive contrast of the brachytherapy seeds using a regularized L1 minimization algorithm. In this paper, we further...
Monte Carlo (MC) simulations play a crucial role in nuclear medical imaging since they can provide the ground truth for clinical acquisitions, by integrating and quantifing all physical parameters that affect image quality. The last decade a number of realistic computational anthropomorphic models have been developed to serve imaging, as well as other biomedical engineering applications. The combination...
Neuroimaging artifacts in haptic functional magnetic resonance imaging (Haptic fMRI) experiments have the potential to induce spurious fMRI activation where there is none, or to make neural activation measurements appear correlated across brain regions when they are actually not. Here, we demonstrate that performing three-dimensional goal-directed reaching motions while operating Haptic fMRI Interface...
Sustained release of a small molecule from a prototype implantable drug delivery device was monitored via MRI in an ex vivo tissue phantom over a period of two days. T1 mapping was used as a method to quantify analyte concentration. Continuous, controlled release was observed. The MRI methodology was thus found to be appropriate for device validation and quality assurance/control.
Computed tomography (CT) is the current gold standard for imaging kidney stones, albeit at the cost of radiation exposure. Conventional magnetic resonance imaging (MRI) sequences are insensitive to detecting the stones because of their appearance as a signal void. With the development of 2D ultra-short echo-time (UTE) MRI sequences, it becomes possible to image kidney stones in vitro. In this work,...
An essential feature of magnetic resonance (MR) probes for magnetic resonance imaging and spectroscopy is the ability to generate uniform B1+ excitation in a volume of interest. When the magnetic field strength is increased, leading to an increase in resonance frequency, the constraints on the MR probes size, the sample size and the associated radiation losses caused by conductor elements are higher...
A new MR spectroscopic imaging method, called SPICE (SPectroscopic Imaging by exploiting spatiospectral CorrElation), has been recently proposed to enable highresolution metabolic imaging with good SNR. A key problem within the SPICE framework is image reconstruction from a very noisy and sparsely sampled dataset. This paper addresses this problem by integrating the low-rank model used in SPICE reconstruction...
Photon scatter is the dominant light transport process in biological tissue and is well understood to degrade imaging performance in near-infrared diffuse optical tomography. Measurement of photons arriving at early times following a short laser pulse is considered to be an effective method to improve this limitation, i.e. by systematically selecting photons that have experienced fewer scattering...
This paper presents an algorithm for three dimensional (3D) reconstruction of tumor ablations using ultrasound electrode vibration elastography. Shear wave velocity, which is used as a surrogate for tissue stiffness, is estimated by perturbing the ablation needle and tracking frame-to-frame displacements using radiofrequency ultrasound echo data. This process is repeated over many imaging planes that...
Piecewise linear function fitting is ubiquitous in many signal processing applications. Inspired by an application to shear wave velocity imaging in ultrasound elastography, this paper presents a discrete state-space Markov model for noisy piecewise linear data and also proposes a tractable algorithm for maximum a posteriori estimation of the slope of each segment in the piecewise linear function...
Harmonic Motion Microwave Doppler Imaging (HMMDI) is a hybrid method proposed for breast tumor detection, which images the coupled dielectric and elastic properties of the tissue. In this paper, the performance of a data acquisition system for HMMDI method is evaluated on breast phantom materials. A breast fat phantom including fibro-glandular and tumor phantom regions is produced. The phantom is...
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