The Experts below are selected from a list of 16845 Experts worldwide ranked by ideXlab platform
Thomasbüttner - One of the best experts on this subject based on the ideXlab platform.
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Transient Response Harmonic Imaging
Stroke, 1998Co-Authors: Thomaspostert, Andreamuhs, Saskiameves, Jensfederlein, Horstprzuntek, ThomasbüttnerAbstract:Background and Purpose—Gray-scale Harmonic Imaging is the first method to visualize blood perfusion and capillary blood flow with ultrasound after intravenous contrast agent application. The purpose of the present study was to evaluate the potential of transient response second Harmonic Imaging (TRsHI) to assess normal echo contrast characteristics in different brain areas by transcranial ultrasound. Methods—In 18 patients without cerebrovascular diseases, TRsHI examinations were performed bilaterally with the use of the transtemporal approach after application of 6.5 mL of a galactose-based microbubble suspension (400 mg/mL). The transmission rate was once every 4 cardiac cycles. Regional cerebral contrast was visually assessed and then quantified off-line with the use of time-intensity curves. In 4 different regions of interest (ROI) (posterior part of the thalamus [ROIa], anterior part of the thalamus [ROIb], lentiform nucleus [ROIc], and white matter [ROId]), the following parameters were evaluated: p...
Shigao Chen - One of the best experts on this subject based on the ideXlab platform.
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delay encoded Harmonic Imaging de hi in multiplane wave compounding
IEEE Transactions on Medical Imaging, 2017Co-Authors: Ping Gong, Pengfei Song, Shigao ChenAbstract:The development of ultrafast ultrasound Imaging brings great opportunities to improve Imaging technologies such as shear wave elastography and ultrafast Doppler Imaging. In ultrafast Imaging, several tilted plane or diverging wave images are coherently combined to form a compounded image, leading to trade-offs among image signal-to-noise ratio (SNR), resolution, and post-compounded frame rate. Multiplane wave (MW) Imaging is proposed to solve this trade-off by encoding multiple plane waves with Hadamard matrix during one transmission event (i.e. pulse-echo event), to improve image SNR without sacrificing the resolution or frame rate. However, it suffers from stronger reverberation artifacts in B-mode images compared to standard plane wave compounding due to longer transmitted pulses. If Harmonic Imaging can be combined with MW Imaging, the reverberation artifacts and other clutter noises such as sidelobes and multipath scattering clutters should be suppressed. The challenge, however, is that the Hadamard codes used in MW Imaging cannot encode the $2^{\mathrm {nd}}$ Harmonic component by inversing the pulse polarity. In this paper, we propose a delay-encoded Harmonic Imaging (DE-HI) technique to encode the $2^{\mathrm {nd}}$ Harmonic with a one quarter period delay calculated at the transmit center frequency, rather than reversing the pulse polarity during multiplane wave emissions. Received DE-HI signals can then be decoded in the frequency domain to recover the signals as in single plane wave emissions, but mainly with improved SNR at the $2^{\mathrm {nd}}$ Harmonic component instead of the fundamental component. DE-HI was tested experimentally with a point target, a B-mode Imaging phantom, and in-vivo human liver Imaging. Improvements in image contrast-to-noise ratio (CNR), spatial resolution, and lesion-signal-to-noise ratio ( $l$ SNR) have been achieved compared to standard plane wave compounding, MW Imaging, and standard Harmonic Imaging (maximal improvement of 116% on CNR and 115% on $l$ SNR as compared to standard HI around 55 mm depth in the B-mode Imaging phantom study). The potential high frame rate and the stability of encoding and decoding processes of DE-HI were also demonstrated, which made DE-HI promising for a wide spectrum of Imaging applications.
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Improved Shear Wave Motion Detection Using Pulse-Inversion Harmonic Imaging With a Phased Array Transducer
IEEE transactions on medical imaging, 2013Co-Authors: Pengfei Song, Heng Zhao, Matthew W. Urban, Armando Manduca, Sorin V. Pislaru, Randall R. Kinnick, Cristina Pislaru, James F. Greenleaf, Shigao ChenAbstract:Ultrasound tissue Harmonic Imaging is widely used to improve ultrasound B-mode Imaging quality thanks to its effectiveness in suppressing Imaging artifacts associated with ultrasound reverberation, phase aberration, and clutter noise. In ultrasound shear wave elastography (SWE), because the shear wave motion signal is extracted from the ultrasound signal, these noise sources can significantly deteriorate the shear wave motion tracking process and consequently result in noisy and biased shear wave motion detection. This situation is exacerbated in in vivo SWE applications such as heart, liver, and kidney. This paper, therefore, investigated the possibility of implementing Harmonic Imaging, specifically pulse-inversion Harmonic Imaging, in shear wave tracking, with the hypothesis that Harmonic Imaging can improve shear wave motion detection based on the same principles that apply to general Harmonic B-mode Imaging. We first designed an experiment with a gelatin phantom covered by an excised piece of pork belly and show that Harmonic Imaging can significantly improve shear wave motion detection by producing less underestimated shear wave motion and more consistent shear wave speed measurements than fundamental Imaging. Then, a transthoracic heart experiment on a freshly sacrificed pig showed that Harmonic Imaging could robustly track the shear wave motion and give consistent shear wave speed measurements of the left ventricular myocardium while fundamental Imaging could not. Finally, an in vivo transthoracic study of seven healthy volunteers showed that the proposed Harmonic Imaging tracking sequence could provide consistent estimates of the left ventricular myocardium stiffness in end-diastole with a general success rate of 80% and a success rate of 93.3% when excluding the subject with Body Mass Index higher than 25. These promising results indicate that pulse-inversion Harmonic Imaging can significantly improve shear wave motion tracking and thus potentially facilitate more robust assessment of tissue elasticity by SWE.
R Schlief - One of the best experts on this subject based on the ideXlab platform.
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Wideband Harmonic Imaging: a novel contrast ultrasound Imaging technique.
European radiology, 1999Co-Authors: A Bauer, P Hauff, J Lazenby, P Von Behren, M Zomack, M Reinhardt, R SchliefAbstract:A novel ultrasonic Imaging method, wideband Harmonic Imaging, for nonlinear Imaging of microbubble contrast agents is evaluated. In wideband Harmonic mode, two pulses of alternate phase are send out. The image is then processed from the sum of both pulses, resulting in an image of nonlinear scatterers such as microbubbles. A prototype ultrasound system, Siemens Elegra, was evaluated with in vitro investigations and animal trials, using conventional, Harmonic and wideband Harmonic settings with the galactose based ultrasound contrast agent Levovist. Wideband Harmonic Imaging offers superior sensitivity for ultrasound contrast agents compared to conventional Imaging and Harmonic Imaging. At low transmit power settings (MI 0. 1-0.5) the nonlinear response is already sufficient to generate a image of the blood pool distribution of Levovist in the rabbit kidney including the microvasculature, with clear delineation of vessels and perfused parenchyma. At high transmit amplitudes, nonlinear tissue response reduced the apparent image contrast between contrast agent and tissue. The results suggest that wideband Harmonic Imaging is currently the most sensitive contrast Imaging technique, maintaining highest spatial resolution. This may add to image quality and offer new clinical potential for the use of ultrasound contrast agents such as Levovist.
Dong Zhang - One of the best experts on this subject based on the ideXlab platform.
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Third order Harmonic Imaging for biological tissues using three phase-coded pulses.
Ultrasonics, 2006Co-Authors: Xiufen Gong, Dong ZhangAbstract:Compared to the fundamental and the second Harmonic Imaging, the third Harmonic Imaging shows significant improvements in image quality due to the better resolution, but it is degraded by the lower sound pressure and signal-to-noise ratio (SNR). In this study, a phase-coded pulse technique is proposed to selectively enhance the sound pressure of the third Harmonic by 9.5 dB whereas the fundamental and the second Harmonic components are efficiently suppressed and SNR is also increased by 4.7 dB. Based on the solution of the KZK nonlinear equation, the axial and lateral beam profiles of Harmonics radiated from a planar piston transducer were theoretically simulated and experimentally examined. Finally, the third Harmonic images using this technique were performed for several biological tissues and compared with the images obtained by the fundamental and the second Harmonic Imaging. Results demonstrate that the phase-coded pulse technique yields a dramatically cleaner and sharper contrast image.
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Investigation on phase-coded third Harmonic Imaging for normal and pathological tissues in transmission mode in vitro
Chinese Science Bulletin, 2006Co-Authors: Xiufen Gong, Dong ZhangAbstract:In this paper, a phase-coded pulse technique is proposed to improve the signal-to-noise ratio (SNR) in the 3rd Harmonic Imaging in transmission mode, where three pulses with initial phases of 0°, 120° and 240° are transmitted and their corresponding received signals are linearly summed. By means of simulations and measurements, we show that the 3rd Harmonic is enhanced by 9.5 dB, whereas the fundamental or the 2nd Harmonic components are suppressed; the axial and lateral beam profiles of the processed 3rd Harmonics are superior to those of the fundamental or 2nd Harmonic components. In addition, this technique is applied to obtain the 3rd Harmonic images for two normal and pathological biological tissues in transmission mode. This technique yields a dramatically cleaner and sharper contrast than the images obtained by the traditional fundamental Imaging and the 2nd Harmonic Imaging, which helps distinguish the normal and pathological states of tissues.
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Improvement of tissue Harmonic Imaging using the pulse-inversion technique.
Ultrasound in medicine & biology, 2005Co-Authors: Xiufen Gong, Dong ZhangAbstract:Harmonic Imaging has brought about significant improvements in image quality by taking advantage of the second Harmonic component, but it still has one shortcoming, namely, a low signal-to-noise ratio. In this paper, a pulse-inversion technique is used in second Harmonic Imaging for biologic tissues to increase the signal-to-noise ratio. Enhancement of the second Harmonic component is theoretically analyzed based on the theory of the finite amplitude sound wave and confirmed by the measurement. Second Harmonic Imaging for biologic tissues is constructed with the pulse-inversion technique and compared with the traditional fundamental frequency and also with second Harmonic Imaging before the use of this technique. Results demonstrate that this technique yields a dramatically cleaner and sharper contrast between the different structures of biologic tissues in ultrasonic images.
Nico De Jong - One of the best experts on this subject based on the ideXlab platform.
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Super-Harmonic Imaging: development of an interleaved phased-array transducer
IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control, 2010Co-Authors: Paul L. M. J. Van Neer, Guillaume Matte, Franc Van Den Adel, Christian Prins, Mikhail G. Danilouchkine, Nico De JongAbstract:For several years, the standard in ultrasound Imaging has been second-Harmonic Imaging. A new Imaging technique dubbed "super-Harmonic Imaging" (SHI) was recently proposed. It takes advantage of the higher-third to fifth-Harmonics arising from nonlinear propagation or ultrasound-contrast-agent (UCA) response. Next to its better suppression of near-field artifacts, tissue SHI is expected to improve axial and lateral resolutions resulting in clearer images than second-Harmonic Imaging. When SHI is used in combination with UCAs, a better contrast-to-tissue ratio can be obtained. The use of SHI implies a large dynamic range and requires a sufficiently sensitive array over a frequency range from the transmission frequency up to its fifth Harmonic (bandwidth > 130%). In this paper, we present the characteristics and performance of a new interleaved dual frequency array built chiefly for SHI. We report the rationale behind the design choice, frequencies, aperture, and piezomaterials used. The array is efficient both in transmission and reception with well-behaved transfer functions and a combined -6-dB bandwidth of 144%. In addition, there is virtually no contamination of the Harmonic components by spurious transducer transmission, due to low element-to-element crosstalk (< 30 dB) and a low transmission efficiency of the odd Harmonics (< 46 dB). The interleaved array presented in this article possesses ideal characteristics for SHI and is suitable for other methods like second-Harmonic, subHarmonic, and second-order ultrasound field (SURF) Imaging.
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Effect of Harmonic Imaging without contrast on image quality of transesophageal echocardiography.
The American journal of cardiology, 1999Co-Authors: Guido Rocchi, Nico De Jong, Tjebbe W. Galema, Jaroslaw D. Kasprzak, Folkert J. Ten CateAbstract:Harmonic Imaging improves endocardial border delineation during transesophageal echocardiography when compared with conventional Imaging (26% improvement vs 2% worsening; p
