zzi Center For Biomedical Engineering

Riverside, NY, United States

zzi Center For Biomedical Engineering

Riverside, NY, United States
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Mamou J.,zzi Center For Biomedical Engineering | Rohrbach D.,zzi Center For Biomedical Engineering
ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings | Year: 2017

Quantitative acoustic microscopy (QAM) is an imaging modality which uses very-high-frequency ultrasound (i.e., >200 MHz) to form two-dimensional (2D) quantitative images of acoustical and mechanical properties of soft tissues with microscopic resolution (i.e., better than 8 μm). The key component of a QAM system is the ultrasound transducer which must be broadband, have a very small F-number (i.e., < 1.2), and good sensitivity. In this study, two QAM systems based on a 250-MHz and a 500-MHz transducer are presented, yielding 2D quantitative images at spatial resolution of 7 μm and 4 μm respectively. Thin tissue sections obtained using a microtome or cryotome are raster scanned with precise motors and pulse-echo RF signals are digitized. Inverse models are then used to process each RF signal individually to estimate acoustic impedance, speed of sound, and acoustic attenuation as well as derived parameters such as bulk modulus, mass density, and compressibility. To illustrate the QAM technology and signal processing algorithms, images from cancerous human lymph nodes and ophthalmologic samples are presented and coregistered with histology photomicrographs. © 2017 IEEE.

Oelze M.L.,University of Illinois at Urbana - Champaign | Mamou J.,zzi Center For Biomedical Engineering
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2016

Conventional medical imaging technologies, including ultrasound, have continued to improve over the years. For example, in oncology, medical imaging is characterized by high sensitivity, i.e., the ability to detect anomalous tissue features, but the ability to classify these tissue features from images often lacks specificity. As a result, a large number of biopsies of tissues with suspicious image findings are performed each year with a vast majority of these biopsies resulting in a negative finding. To improve specificity of cancer imaging, quantitative imaging techniques can play an important role. Conventional ultrasound B-mode imaging is mainly qualitative in nature. However, quantitative ultrasound (QUS) imaging can provide specific numbers related to tissue features that can increase the specificity of image findings leading to improvements in diagnostic ultrasound. QUS imaging can encompass a wide variety of techniques including spectral-based parameterization, elastography, shear wave imaging, flow estimation, and envelope statistics. Currently, spectral-based parameterization and envelope statistics are not available on most conventional clinical ultrasound machines. However, in recent years, QUS techniques involving spectral-based parameterization and envelope statistics have demonstrated success in many applications, providing additional diagnostic capabilities. Spectral-based techniques include the estimation of the backscatter coefficient (BSC), estimation of attenuation, and estimation of scatterer properties such as the correlation length associated with an effective scatterer diameter (ESD) and the effective acoustic concentration (EAC) of scatterers. Envelope statistics include the estimation of the number density of scatterers and quantification of coherent to incoherent signals produced from the tissue. Challenges for clinical application include correctly accounting for attenuation effects and transmission losses and implementation of QUS on clinical devices. Successful clinical and preclinical applications demonstrating the ability of QUS to improve medical diagnostics include characterization of the myocardium during the cardiac cycle, cancer detection, classification of solid tumors and lymph nodes, detection and quantification of fatty liver disease, and monitoring and assessment of therapy. © 2015 IEEE.

Mamou J.,zzi Center For Biomedical Engineering | Oelze M.L.,University of Illinois at Urbana - Champaign
Quantitative Ultrasound in Soft Tissues | Year: 2013

Due to parallel advances in signal processing and computer hardware in the last 15 years, quantitative ultrasound techniques have reached maturity, allowing for the construction of quantitative maps or images of soft tissues. This book will focus on 5 modern research topics related to quantitative ultrasound of soft tissues: - Spectral-based methods for tissue characterization, tissue typing, cancer detection, etc.; - Envelope statistics analysis as a means of quantifying and imaging tissue properties; - Ultrasound elastography for quantifying elastic properties of tissues (several clinical ultrasound scanners now display elastography images); - Scanning acoustic microscopy for forming images of mechanical properties of soft tissues with micron resolution (desktop size scanners are now available); and - Ultrasound computer tomography for breast cancer imaging (new ultrasound tomography systems have been developed and are currently under evaluation clinically). © Springer Science+Business Media Dordrecht 2013.

Mamou J.,zzi Center For Biomedical Engineering | Wa C.A.,VMR Institute for Vitreous Macula Retina | Wa C.A.,Doheny Eye Institute | Yee K.M.P.,VMR Institute for Vitreous Macula Retina | And 6 more authors.
Investigative Ophthalmology and Visual Science | Year: 2015

PURPOSE. Clinical evaluation of floaters lacks quantitative assessment of vitreous structure. This study used quantitative ultrasound (QUS) to measure vitreous opacities. Since floaters reduce contrast sensitivity (CS) and quality of life (Visual Function Questionnaire [VFQ]), it is hypothesized that QUS will correlate with CS and VFQ in patients with floaters.METHODS. Twenty-two eyes (22 subjects; age ¼ 57 6 19 years) with floaters were evaluated with Freiburg acuity contrast testing (FrACT; %Weber) and VFQ. Ultrasonography used a customized probe (15-MHz center frequency, 20-mm focal length, 7-mm aperture) with longitudinal and transverse scans taken in primary gaze and a horizontal longitudinal scan through premacular vitreous in temporal gaze. Each scan set had 100 frames of log-compressed envelope data. Within each frame, two regions of interest (ROIs) were analyzed (whole-central and posterior vitreous) to yield three parameters (energy, E; mean amplitude, M; and percentage of vitreous filled by echodensities, P50) averaged over the entire 100-frame dataset. Statistical analyses evaluated E, M, and P50 correlations with CS and VFQ.RESULTS. Contrast sensitivity ranged from 1.19%W (normal) to 5.59%W. All QUS parameters in two scan positions within the whole-central ROI correlated with CS (R > 0.67, P < 0.001). P50 in the nasal longitudinal position had R ¼ 0.867 (P < 0.001). Correlations with VFQ ranged from R ¼ 0.52 (P < 0.013) to R ¼ 0.65 (P < 0.001).CONCLUSIONS. Quantitative ultrasound provides quantitative measures of vitreous echodensity that correlate with CS and VFQ, providing objective assessment of vitreous structure underlying the functional disturbances induced by floaters, useful to quantify vitreous disease severity and the response to therapy. © 2015 The Association for Research in Vision and Ophthalmology, Inc.

Chitnis P.V.,zzi Center For Biomedical Engineering | Koppolu S.,zzi Center For Biomedical Engineering | Mamou J.,zzi Center For Biomedical Engineering | Chlon C.,Philips | Ketterling J.,zzi Center For Biomedical Engineering
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2013

This two-part study investigated shell rupture of ultrasound contrast agents (UCAs) under static overpressure conditions and the subharmonic component from UCAs subjected to 20-MHz tonebursts. Five different polylactide-shelled UCAs with shell-thickness-to-radius ratios (STRRs) of 7.5, 30, 40, 65, and 100 nm/¿m were subjected to static overpressure in a glycerol-filled test chamber. A video microscope imaged the UCAs as pressure varied from 2 to 330 kPa over 90 min. Images were postprocessed to obtain the pressure threshold for rupture and the diameter of individual microbubbles. Backscatter from individual UCAs was investigated by flowing a dilute UCA solution through a wall-less flow phantom placed at the geometric focus of a 20-MHz transducer. UCAs were subjected to 10- and 20-cycle tonebursts of acoustic pressures ranging from 0.3 to 2.3 MPa. A method based on singular-value decomposition (SVD) was employed to obtain a cumulative subharmonic score (SHS). Different UCA types exhibited distinctly different rupture thresholds that were linearly related to their STRR, but uncorrelated with UCA size. The rupture threshold for the UCAs with an STRR = 100 nm/μm was more than 4 times greater than the UCAs with an STRR = 7.5 nm/μm. The polymer-shelled UCAs produced substantial subharmonic response but the subharmonic response to 20- MHz excitation did not correlate with STRRs or UCA-rupture pressures. The 20-cycle excitation resulted in an SHS that was 2 to 3 times that of UCAs excited with 10-cycle tonebursts. © 2013 IEEE.

Franceschini E.,CNRS Laboratory of Mechanics and Acoustics | Monchy R.D.,CNRS Laboratory of Mechanics and Acoustics | Mamou J.,zzi Center For Biomedical Engineering
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control | Year: 2016

Quantitative ultrasound (QUS) methods based on the backscatter coefficient (BSC) are typically model-based. The BSC is estimated from experiments and is fit to a model. The fit parameters are often termed QUS estimates and are used to characterize the scattering properties of the tissue under investigation. Nevertheless, for physical interpretation of QUS estimates to be accurate, the scattering model chosen must also be accurate. The goal of this work was to investigate the use of the structure factor model (SFM) to take into account coherent scattering from high volume fractions of scatterers. The study focuses on comparing the performance of two sparse models (fluid-filled sphere and Gaussian) and one concentrated model (SFM) to estimate QUS parameters from simulations and cell pellet biophantoms with a range of scatterer volume fractions. Results demonstrated the superiority of the SFM for all investigated volume fractions (i.e., from 0.006 to 0.30). In particular, the sparse models underestimated scatterer size and overestimated acoustic concentration when the volume fraction was greater than 0.12. In addition, the SFM has the ability to provide the volume fraction and the relative impedance contrast (instead of only the acoustic concentration provided by the sparse models), which could have a great benefit for tissue characterization. This study demonstrates that the SFM could prove to be an invaluable tool for QUS and could help to more accurately characterize tissue from ultrasound measurements. © 2016 IEEE.

Mamou J.,zzi Center For Biomedical Engineering
Proceedings of Meetings on Acoustics | Year: 2013

Histology performed to assess lymph nodes excised during node-dissection surgeries from cancer patients suffers an unsatisfactory rate of false-negative determinations due to labor and time constraints. In this study, more than 300 lymph nodes were scanned in 3D using a 26-MHz high-frequency ultrasound transducer. Following scanning, individual nodes underwent a special histology procedure that involved step-sectioning each node at 50-μm intervals to guarantee that no significant cancer foci were missed. The 3D radio-frequency ultrasound dataset was analyzed using overlapping 3D regions-of-interests that were individually processed to yield thirteen quantitative ultrasound (QUS) estimates associated with tissue microstructure and were hypothesized to show contrast between normal and cancerous regions in lymph nodes. Step-wise linear discriminant analyses were performed to yield an optimal QUS-based classifier. ROC curves and areas under the ROC curves (AUCs) were obtained to assess cancer-detection performance. The AUC for the linear combination of four QUS estimates was 0.83 for a dataset of 110 axillary nodes of breast-cancer patients. Similarly, using five QUS estimates, an AUC of 0.97 was obtained for a dataset of 180 nodes of gastrointestinal-cancer patients. These studies demonstrate that QUS methods may provide an effective tool to guide pathologist towards suspicious regions in lymph nodes. © 2013 Acoustical Society of America.

Zenbutsu S.,Chiba University | Igarashi T.,Chiba University | Mamou J.,zzi Center For Biomedical Engineering | Yamaguchi T.,Chiba University
Japanese Journal of Applied Physics | Year: 2012

Laparoscopic surgery is one of the most challenging surgical operations, because inside information about the target organ cannot be fully understood from the laparoscopic image. Therefore, a fusion technique of laparoscopic and ultrasonic images is proposed for guidance during laparoscopic surgery. The proposed technique can display the internal organ structure by overlaying a three-dimensional (3D) ultrasonic image over a 3D laparoscopic image, which is acquired using a stereo laparoscope. The registration of the 3D images is performed by registering the surface of the target organ, which is found in the two 3D images without requiring the use of an external position detecting device. The proposed technique was evaluated experimentally using a tissue-mimicking phantom. Results obtained led to registration accuracy better than 2 cm. The total computation time was 3.1 min on a personal computer (Xeon processor, 3 GHz CPU). The structural information permits the visualization of target organs during laparoscopic surgery. © 2012 The Japan Society of Applied Physics.

Silverman R.H.,Columbia University | Silverman R.H.,zzi Center For Biomedical Engineering | Urs R.,Columbia University | Roychoudhury A.,Columbia University | And 5 more authors.
Investigative Ophthalmology and Visual Science | Year: 2014

PURPOSE. To develop and evaluate automated computerized algorithms for differentiation of normal and keratoconus corneas based solely on epithelial and stromal thickness data. METHODS. Maps of the corneal epithelial and stromal thickness were generated from Artemis-1 very high-frequency ultrasound arc-scans of 130 normal and 74 keratoconic subjects diagnosed by combined topography and tomography examination. Keratoconus severity was graded based on anterior curvature, minimum corneal thickness, and refractive error. Computer analysis of maps produced 161 features for one randomly selected eye per subject. Stepwise linear discriminant analysis (LDA) and neural network (NN) analysis were then performed to develop multivariate models based on combinations of selected features to correctly classify cases. The sensitivity, specificity, and area under the receiver operating characteristic curve (AUC) were determined for each classifier. RESULTS. Stepwise LDA resulted in a six-variable model that provided an AUC of 100%, indicative of complete separation of keratoconic from normal corneas. Leave-one-out analysis resulted in 99.2% specificity and 94.6% sensitivity. Neural network analysis using the same six variables resulted in an AUC of 100% for the training set. Test set performance averaged over 10 trials gave a specificity of 99.5 6 1.5% and sensitivity of 98.9 6 1.9%. The LDA function values correlated with keratoconus severity grade. CONCLUSIONS. The results demonstrate that epithelial remodeling in keratoconus represents an independent means for differentiation of normal from advanced keratoconus corneas. © 2014 The Association for Research in Vision and Ophthalmology, Inc.

PubMed | zzi Center For Biomedical Engineering, Kuakini Medical Center, Paris-Sorbonne University, French National Center for Scientific Research and 3 more.
Type: Journal Article | Journal: Japanese journal of applied physics (2008) | Year: 2014

This work investigates the statistics of the envelope of three-dimensional (3D) high-frequency ultrasound (HFU) data acquired from dissected human lymph nodes (LNs). Nine distributions were employed, and their parameters were estimated using the method of moments. The Kolmogorov Smirnov (KS) metric was used to quantitatively compare the fit of each candidate distribution to the experimental envelope distribution. The study indicates that the generalized gamma distribution best models the statistics of the envelope data of the three media encountered: LN parenchyma, fat and phosphate-buffered saline (PBS). Furthermore, the envelope statistics of the LN parenchyma satisfy the pre-Rayleigh condition. In terms of high fitting accuracy and computationally efficient parameter estimation, the gamma distribution is the best choice to model the envelope statistics of LN parenchyma, while, the Weibull distribution is the best choice to model the envelope statistics of fat and PBS. These results will contribute to the development of more-accurate and automatic 3D segmentation of LNs for ultrasonic detection of clinically significant LN metastases.

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