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Jafari S.,University Pierre and Marie Curie | Diou O.,University Paris - Sud | Mamou J.,Lizzi Center for Biomedical Engineering | Renault G.,French Institute of Health and Medical Research | And 3 more authors.
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2014

Liquid-core nanoparticles are promising candidates for targeted ultrasound-controlled therapy, but their acoustic detection remains challenging. High-frequency (20 to 40 MHz) tone burst sequences were implemented with a programmable ultrasound biomicroscope to characterize acoustic response from perfluorooctyl bromide-core nanoparticles with thick poly(lactide-coglycolide) (PLGA) shells. Radio-frequency signals were acquired from flowing solutions of nanoparticles with two different shell-thickness-to-particle-radius ratios, solid PLGA nanoparticles, and latex nanobeads (linear controls). Normalized fundamental (20 MHz) and second-harmonic power spectral density (PSD) increased with particle concentration and was highest for the thinnest shelled particles. The second-harmonic PSD was detectable from the nanoparticles for peak rarefactional pressures (PRP) from 0.97 to 2.01 MPa at 23 cycles and for tone bursts from 11 to 23 cycles at 2.01 MPa. Their second-harmonic-to-fundamental ratio increased as a function of PRP and number of cycles. Within the same PRP and cycle ranges, the second-harmonic-to-fundamental ratios from matched concentration solutions of latex nanobeads and solid PLGA nanoparticles was more weakly detectable but also increased with PRP and number of cycles. Nanoparticles were detectable under flow conditions in vitro using the contrast agent mode of a high-frequency commercial scanner. These results characterize linear acoustic response from the nanoparticles (20 to 40 MHz) and demonstrate potential for their highfrequency detection. © 1986-2012 IEEE.

PubMed | Lizzi Center for Biomedical Engineering, Honda Electronics Co. and Chiba University
Type: Journal Article | Journal: The Journal of the Acoustical Society of America | Year: 2016

In this study, the speed of sound (SOS) of two types of rat livers (eight normal livers, four cirrhotic livers) was measured with a scanning acoustic microscope using two transducers, one of which had an 80-MHz and the other a 250-MHz center frequency. The 250-MHz transducer had a better spatial resolution adapted to studying fiber or hepatic parenchymal cells. In normal livers, averages of the SOS values were from 1598 to 1677m/s at 80-MHz and from 1568 to 1668m/s at 250-MHz. In the fiber tissue of cirrhotic livers, averages of the SOS values were from 1645 to 1658m/s at 80-MHz and from 1610 to 1695m/s at 250-MHz, while the SOS values in the other tissue of cirrhotic livers ranged from 1644 to 1709m/s at 80-MHz and from 1641 to 1715m/s at 250-MHz. In one liver, SOS in fiber tissue was larger than that of tissues without fiber while in others it was lower. The resulting two-dimensional SOS maps provide a unique quantitative insight of liver acoustic microstructures in a healthy liver and in a cirrhotic ones. This study would be helpful to understand the complex relationship between acoustic properties and liver disease including fiber tissue.

Sparks R.,Rutgers University | Sparks R.,Case Western Reserve University | Bloch B.N.,Boston University | Feleppa E.,Lizzi Center for Biomedical Engineering | And 2 more authors.
Proceedings of SPIE - The International Society for Optical Engineering | Year: 2013

In this work, we present a novel, automated, registration method to fuse magnetic resonance imaging (MRI) and transrectal ultrasound (TRUS) images of the prostate. Our methodology consists of: (1) delineating the prostate on MRI, (2) building a probabilistic model of prostate location on TRUS, and (3) aligning the MRI prostate segmentation to the TRUS probabilistic model. TRUS-guided needle biopsy is the current gold standard for prostate cancer (CaP) diagnosis. Up to 40% of CaP lesions appear isoechoic on TRUS, hence TRUS-guided biopsy cannot reliably target CaP lesions and is associated with a high false negative rate. MRI is better able to distinguish CaP from benign prostatic tissue, but requires special equipment and training. MRI-TRUS fusion, whereby MRI is acquired pre-operatively and aligned to TRUS during the biopsy procedure, allows for information from both modalities to be used to help guide the biopsy. The use of MRI and TRUS in combination to guide biopsy at least doubles the yield of positive biopsies. Previous work on MRI-TRUS fusion has involved aligning manually determined fiducials or prostate surfaces to achieve image registration. The accuracy of these methods is dependent on the reader's ability to determine fiducials or prostate surfaces with minimal error, which is a difficult and time-consuming task. Our novel, fully automated MRI-TRUS fusion method represents a significant advance over the current state-of-the-art because it does not require manual intervention after TRUS acquisition. All necessary preprocessing steps (i.e. delineation of the prostate on MRI) can be performed offline prior to the biopsy procedure. We evaluated our method on seven patient studies, with B-mode TRUS and a 1.5 T surface coil MRI. Our method has a root mean square error (RMSE) for expertly selected fiducials (consisting of the urethra, calcifications, and the centroids of CaP nodules) of 3 .39 ± 0.85 mm. © 2013 SPIE.

Treeby B.E.,University College London | Jaros J.,Brno University of Technology | Rohrbach D.,Lizzi Center for Biomedical Engineering | Cox B.T.,University College London
IEEE International Ultrasonics Symposium, IUS | Year: 2014

A new model for simulating elastic wave propagation using the open-source k-Wave MATLAB Toolbox is described. The model is based on two coupled first-order equations describing the stress and particle velocity within an isotropic medium. For absorbing media, the Kelvin-Voigt model of viscoelasticity is used. The equations are discretised in 2D and 3D using an efficient time-stepping pseudospectral scheme. This uses the Fourier collocation spectral method to compute spatial derivatives and a leapfrog finite-difference scheme to integrate forwards in time. A multi-axial perfectly matched layer (M-PML) is implemented to allow free-field simulations using a finite-sized computational grid. Acceleration using a graphics processing unit (GPU) is supported via the MATLAB Parallel Computing Toolbox. An overview of the simulation functions and their theoretical and numerical foundations is described. © 2014 IEEE.

Kuo J.-W.,New York University | Wang Y.,New York University | Aristizabal O.,Lizzi Center for Biomedical Engineering | Ketterling J.A.,Lizzi Center for Biomedical Engineering | Mamou J.,Lizzi Center for Biomedical Engineering
IEEE International Ultrasonics Symposium, IUS | Year: 2013

Volumetric analysis of brain ventricles is important to the study of normal and abnormal development of the central nervous system of mouse embryos. High-frequency ultrasound (HFU) is frequently used to image embryos because HFU is real-time, non-invasive, and provides fine-resolution images. However, manual segmentation of ventricles from 3D HFU volumes remains challenging and time consuming. In this study, in utero and in vivo volumetric ultrasound data were acquired from pregnant mice using a 5-element, 40-MHz annular array. An automatic segmentation algorithm based on active shape model (ASM) was developed to segment the brain ventricles of the embryos; ASM allows us to efficiently 'learn' from training data (i.e., manually segmented data). The algorithm was further enhanced by using detail-preserving reference shapes (also learned from training data) and region growing constrained by the reference shape. The hybrid algorithm was applied to three 12.5-day-old embryos. Results were qualitatively analyzed and compared with manual segmentation results in regions typically difficult to segment (e.g., thin brain ventricle connections). In addition, quantitative analysis using the Dice similarity coefficient (DSC) was used to compare the automatic segmentation results with manual segmentation. We obtained average DSC values of 0.848±0.015 for the brain ventricles and our method produced morphologically accurate results. Therefore, our method could streamline current HFU longitudinal studies of brain development that require manual segmentation. © 2013 IEEE.

Aristizabal O.,New York University | Aristizabal O.,Lizzi Center for Biomedical Engineering | Mamou J.,Lizzi Center for Biomedical Engineering | Ketterling J.A.,Lizzi Center for Biomedical Engineering | Turnbull D.H.,New York University
Ultrasound in Medicine and Biology | Year: 2013

With the emergence of the mouse as the predominant model system for studying mammalian brain development, in utero imaging methods are urgently required to analyze the dynamics of brain growth and patterning in mouse embryos. To address this need, we combined synthetic focusing with a high-frequency (38-MHz) annular-array ultrasound imaging system for extended depth-of-field, coded excitation for improved penetration and respiratory-gated transmit/receive. This combination allowed non-invasive in utero acquisition of motion-free 3-D data from individual embryos in approximately 2min, and data from four or more embryos in a pregnant mouse in less than 30min. Data were acquired from 148 embryos spanning 5d of early to mid-gestational stages of brain development. The results indicated that brain anatomy and cerebral vasculature can be imaged with this system and that quantitative analyses of segmented cerebral ventricles can be used to characterize volumetric changes associated with mouse brain development. © 2013 World Federation for Ultrasound in Medicine & Biology.

Rohrbach D.,Lizzi Center for Biomedical Engineering | Lloyd H.O.,Columbia University | Silverman R.H.,Lizzi Center for Biomedical Engineering | Silverman R.H.,Columbia University | Mamou J.,Lizzi Center for Biomedical Engineering
Journal of the Acoustical Society of America | Year: 2015

Ex vivo assessment of microscale tissue biomechanical properties of the mammalian retina could offer insights into diseases such as keratoconus, and macular degeneration. A 250-MHz scanning acoustic microscope (7-μm resolution) has been constructed to derive two-dimensional quantitative maps of attenuation (α), speed of sound (c), acoustic impedance (Z), bulk modulus (B), and mass density (ρ). The two-dimensional maps were compared to coregistered hematoxylin-and-eosin stained sections. This study is the first to quantitatively assess ? α, c, Z, B, and ρ of individual retinal layers of mammalian animals at high ultrasound frequencies. Significant differences in these parameters between the layers were demonstrated. © 2015 Acoustical Society of America.

Ketterling J.A.,Lizzi Center for Biomedical Engineering | Gross D.,Lizzi Center for Biomedical Engineering | Silverman R.H.,Columbia University
2015 IEEE International Ultrasonics Symposium, IUS 2015 | Year: 2015

Ophthalmic ultrasound is almost exclusively performed using single-element, handheld transducers. Linear-array systems are not feasible for ophthalmology for the foreseeable future. Annular arrays permit linear-array image quality but without the system complexity and cost. Here, an annular-array transducer previously demonstrated using a cumbersome immersion-scan technique (i.e., water bath coupled to eye) was integrated into a handheld probe that permitted contact scanning of the human eye. A custom, 5-element, 20-MHz annular array based on a 25-μm, P(VDF-TrFE) membrane was packaged in a stainless steel shell and mounted in a commercial, handheld, mechanical probe specifically designed for clinical ophthalmic imaging. The array had a focal length of 25.8 mm and an aperture of 9 mm. The array was characterized using a 25-μm wire and a calibrated hydrophone. After establishing the acoustic parameters were within safety limits, human subjects were imaged. Human-subject scanning was performed by placing the tip of the fluid-filled probe in contact with the sclera. © 2015 IEEE.

Ketterling J.,Lizzi Center for Biomedical Engineering
Proceedings of Meetings on Acoustics | Year: 2013

A high-frequency (HF) imaging system based on a custom 5-element, 40-MHz annular array was used to study cardiovascular development of mouse embryos. High-frame-rate imaging of the heart dynamics was achieved using a retrospective reconstruction method based on electrocardiogram (ECG) waveforms and respiratory gating. The ECG signals were obtained by measuring blood-flow velocities in major arteries of in-vivo mouse embryos using a custom, HF Doppler apparatus made from two, 20-MHz, single-element, PZT transducers. Co-registered M-mode data were acquired from the annular array excited with a 5-channel pulser/receiver. A synthetic-focusing algorithm was used to improve spatial resolution (< 100 μm), depth-of-field (> 10 mm) and signal-to-noise ratio (> 45 dB). This technique was used on embryos aged from 11.5 to 14.5 days and provided high-resolution, morphologically correct B-mode cine-loops of the heart chamber dynamics at frame rates of 1 kHz. The ultra-fine temporal resolution (1 ms) permitted precise quantification of the mean cardiac cycle length and detailed visualization of fast events such as opening and closing of the mitral valve. The speckle characteristics of the high-resolution images could be used to assess blood flow and to quantify myocardial strain at each developmental stage of the embryonic heart. © 2013 Acoustical Society of America.

Ketterling J.A.,Lizzi Center for Biomedical Engineering | Filoux E.,Lizzi Center for Biomedical Engineering
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2012

Annular arrays provide a means to achieve enhanced image quality with a limited number of elements. Synthetic-focusing (SF) strategies that rely on beamforming data from individual transmit-to-receive (TR) element pairs provide a means to improve image quality without specialized TR delay electronics. Here, SF strategies are examined in the context of high-frequency ultrasound (>15 MHz) annular arrays composed of five elements, operating at 18 and 38 MHz. Acoustic field simulations are compared with experimental data acquired from wire and anechoic-sphere phantoms, and the values of lateral beamwidth, SNR, contrast-to-noise ratio (CNR), and depth of field (DOF) are compared as a function of depth. In each case, data were acquired for all TR combinations (25 in total) and processed with SF using all 25 TR pairs and SF with the outer receive channels removed one by one. The results show that removing the outer receive channels led to an overall degradation of lateral resolution, an overall decrease in SNR, and did not reduce the DOF, although the DOF profile decreased in amplitude. The CNR was >1 and remained fairly constant as a function of depth, with a slight decrease in CNR for the case with just the central element receiving. The relative changes between the calculated and measured quantities were nearly identical for the 18- and 38-MHz arrays. B-mode images of the anechoic phantom and an in vivo mouse embryo using full SF with 25 TR pairs or reduced TR-pair approaches showed minimal qualitative difference. © 2012 IEEE.

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