Vijay Shamdasani | Philips Electronics (original) (raw)

Papers by Vijay Shamdasani

2019 IEEE International Ultrasonics Symposium (IUS)

Ultrasound shear wave elastography (SWE) has become a clinically accepted tool for tissue charact... more Ultrasound shear wave elastography (SWE) has become a clinically accepted tool for tissue characterization, cancer diagnosis, and therapy assessment. However, it is only commercially available on premium ultrasound scanners and high-performance transducers capable of sustaining high-voltage, long-duration acoustic push-pulses. Mechanical vibration is an alternative method for acoustic radiation force (ARF) to induce shear wave propagation inside soft tissue, thus enabling ultrasound SWE on low-cost and portable systems. One potential application is compartment syndrome (CS), with the acute cases commonly seen in traumatic injuries and chronic cases caused by exercise injuries. CS is a condition in which the increased pressure in the muscle compartment inhibits capillary blood flow and subsequently causes muscle ischemia. To avoid permanent muscle injury, CS must be diagnosed and treated rapidly. In this study, a vibration-enabled SWE prototype was implemented on a commercial scanner and evaluated using an in vivo swine CS model as a proof-of-concept for non-invasive CS detection.

2017 IEEE International Ultrasonics Symposium (IUS), 2017

Ultrasound shear wave elastography (SWE) imaging is commercially available on expensive systems. ... more Ultrasound shear wave elastography (SWE) imaging is commercially available on expensive systems. ARF-based shear wave generation requires complex electronics and may induce thermal stress to the tissue. There is need and interest to develop external mechanical vibration (EMV) as a low-cost approach to generate shear waves. Commercial development of mechanical vibration using a single-element transducer has been successful but lacks 2D imaging as guidance. Here we present the simulation, design and implementation of a new way of performing external mechanical vibration that could be adopted by commercial ultrasound probes for SWE imaging.

2018 IEEE International Ultrasonics Symposium (IUS), 2018

Shear wave generation using external mechanical vibration (EMV)is promising for enabling shear wa... more Shear wave generation using external mechanical vibration (EMV)is promising for enabling shear wave elastography (SWE)imaging on low-cost platforms. In this paper, we present the design and experimental validation of miniature external mechanical vibrators with ergonomic form factor suitable for routine clinical practice: 5 % of their predecessor. The newly designed miniature actuator is able to magnetically attach to ultrasound probes and vibrate at 50 Hz with 2 mm peak-to-peak amplitude. Effective shear wave propagation with varying patterns was induced in elasticity phantoms using miniature shear wave actuators in three different configurations: one actuator in plane; two actuators in plane and two actuators cross plane. A commercial acoustic radiation force impulse (ARFI)based shear wave elastography technique was also used on elasticity phantoms as benchmark. Reconstructed stiffness values from EMV in all configurations were in agreement with the ARFI-based approach at 50 Hz shear wave propagation.

Investigative Radiology, 2021

BACKGROUND Nonalcoholic fatty liver disease (NAFLD) is a leading cause of chronic liver disease w... more BACKGROUND Nonalcoholic fatty liver disease (NAFLD) is a leading cause of chronic liver disease worldwide. Quantitative ultrasound (QUS) parameters based on radiofrequency raw data show promise in quantifying liver fat. PURPOSE The aim of this study was to evaluate the diagnostic performance of 9 QUS parameters compared with magnetic resonance imaging (MRI)-estimated proton density fat fraction (PDFF) in detecting and staging hepatic steatosis in patients with or suspected of NAFLD. MATERIALS AND METHODS In this Health Insurance Portability and Accountability Act-compliant institutional review board-approved prospective study, 31 participants with or suspected of NAFLD, without other underlying chronic liver diseases (13 men, 18 women; average age, 52 years [range, 26-90 years]), were examined. The following parameters were obtained: acoustic attenuation coefficient (AC); hepatorenal index (HRI); Nakagami parameter; shear wave elastography measures such as shear wave elasticity, viscosity, and dispersion; and spectroscopy-derived parameters including spectral intercept (SI), spectral slope (SS), and midband fit (MBF). The diagnostic ability (area under the receiver operating characteristic curves and accuracy) of QUS parameters was assessed against different MRI-PDFF cutoffs (the reference standard): 6.4%, 17.4%, and 22.1%. Linearity with MRI-PDFF was evaluated with Spearman correlation coefficients (p). RESULTS The AC, SI, Nakagami, SS, HRI, and MBF strongly correlated with MRI-PDFF (P = 0.89, 0.89, 0.88, -0.87, 0.81, and 0.71, respectively [P < 0.01]), with highest area under the receiver operating characteristic curves (ranging from 0.85 to 1) for identifying hepatic steatosis using 6.4%, 17.4%, and 22.1% MRI-PDFF cutoffs. In contrast, shear wave elasticity, shear wave viscosity, and shear wave dispersion did not strongly correlate to MRI-PDFF (P = 0.45, 0.38, and 0.07, respectively) and had poor diagnostic performance. CONCLUSION The AC, Nakagami, SI, SS, MBF, and HRI best correlate with MRI-PDFF and show high diagnostic performance for detecting and classifying hepatic steatosis in our study population. SUMMARY STATEMENT Quantitative ultrasound is an accurate alternative to MRI-based techniques for evaluating hepatic steatosis in patients with or at risk of NAFLD. KEY FINDINGS Our preliminary results show that specific quantitative ultrasound parameters accurately detect different degrees of hepatic steatosis in NAFLD.

Journal of Ultrasound in Medicine, 2012

troke due to atherosclerosis is among the leading causes of death and disability worldwide, with ... more troke due to atherosclerosis is among the leading causes of death and disability worldwide, with estimated direct and indirect costs in 2010 of $73.7 billion in the United States alone. 1 Although stenotic narrowing of major vessels, including the carotid artery, is a clear risk factor for stroke, many pathologic studies have concluded that certain high-risk features of culprit atherosclerotic plaques themselves should also play a role in assessing the risk of cardiovascular events. Specifically, vulnerable lesions are typically characterized by a thin fibrous cap separating a lipid-rich necrotic core from the lumen. 2-4 In addition, the presence of intraplaque hemorrhage is associated with

2015 IEEE International Ultrasonics Symposium (IUS), 2015

Perform a comparison of shear wave speed (SWS) measurements between commercially-available system... more Perform a comparison of shear wave speed (SWS) measurements between commercially-available systems using calibrated phantoms that have viscoelastic behavior similar to that observed in normal and fibrotic liver.

Physics in medicine and biology, Jan 7, 2012

Most techniques for contrast-enhanced ultrasound imaging require linear propagation to detect non... more Most techniques for contrast-enhanced ultrasound imaging require linear propagation to detect nonlinear scattering of contrast agent microbubbles. Waveform distortion due to nonlinear propagation impairs their ability to distinguish microbubbles from tissue. As a result, tissue can be misclassified as microbubbles, and contrast agent concentration can be overestimated; therefore, these artifacts can significantly impair the quality of medical diagnoses. Contrary to biological tissue, lipid-coated gas microbubbles used as a contrast agent allow the interaction of two acoustic waves propagating in opposite directions (counter-propagation). Based on that principle, we describe a strategy to detect microbubbles that is free from nonlinear propagation artifacts. In vitro images were acquired with an ultrasound scanner in a phantom of tissue-mimicking material with a cavity containing a contrast agent. Unlike the default mode of the scanner using amplitude modulation to detect microbubble...

Journal of Clinical and Experimental Hepatology, 2022

Background/Aims: Non-alcoholic fatty liver disease (NAFLD) is widespread chronic disease of the l... more Background/Aims: Non-alcoholic fatty liver disease (NAFLD) is widespread chronic disease of the live in humans with the prevalence of 30% of the United States population. 1,2 The goal of the study is to validate the performance of quantitative ultrasound algorithms in the assessment of hepatic steatosis in patients with suspected NAFLD. Methods: This prospective study enrolled a total of 31 patients with clinical suspicion of NAFLD to receive liver fat measurements by quantitative ultrasound and reference MRI measurements (proton density fat-fraction, PDFF). The following ultrasound (US) parameters based on both raw ultrasound RF (Radio Frequency) data and 2D Bmode images of the liver were analyzed with subsequent correlation with MRI-PDFF: hepatorenal index, acoustic attenuation coefficient, Nakagami coefficient parameter, shear wave viscosity, shear wave dispersion and shear wave elasticity. Ultrasound parameters were also correlated with the presence of hypertension and diabetes. Results: The mean (± SD) age and body mass index of the patients were 49.03 (± 12.49) and 30.12 (± 6.15), respectively. Of the aforementioned ultrasound parameters, the hepatorenal index and acoustic attenuation coefficient showed a strong correlation with MRI-PDFF derivations of hepatic steatosis, with r-values of 0.829 and 0.765, respectively. None of the remaining US parameters showed strong correlations with PDFF. Significant differences in Nakagami parameters and acoustic attenuation coefficients were found in those patients with and without hypertension. Conclusions: Hepatorenal index and acoustic attenuation coefficient correlate well with MRI-PDFF-derived measurements of hepatic steatosis. Quantitative ultrasound is a promising tool for the diagnosis and assessment of patients with NAFLD.

Fig. 2 Plaque Components (Calcification – Dark Blue, Loose Matrix – Purple), lumen (red) and oute... more Fig. 2 Plaque Components (Calcification – Dark Blue, Loose Matrix – Purple), lumen (red) and outer wall (light blue) boundaries as appeared in US images. Calcification in (a) Subject 1 and (b) Subject 3. (c) Loose matrix appears dark in an US image. Table 2: Average, standard deviation (in parenthesis) and range (inside [ ]) of each plaque component of each subject. Table 1: Registration error (in mm) without (w/o) and with (w Sh) manual shifting adjustment. Characterization of Carotid Plaque in Three-Dimensional Ultrasound by Registration with Multicontrast MRI

American Journal of Roentgenology

Journal of Ultrasound in Medicine

Proceedings of Spie the International Society For Optical Engineering, Mar 1, 2007

Three-dimensional (3D) ultrasound has become a useful tool in cardiac imaging, OB/GYN and other c... more Three-dimensional (3D) ultrasound has become a useful tool in cardiac imaging, OB/GYN and other clinical applications. It enables clinicians to visualize the acquired volume and/or planes that are not easily accessible using 2D ultrasound, in addition to providing an intuitive ...