Publications
264 results found
Harput S, Christensen-Jeffries K, Brown J, et al., 2018, 3-D super-resolution ultrasound (SR-US) imaging using a 2-D sparse array with high volumetric imaging rate, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE
Super-resolution ultrasound imaging has been sofar achieved in 3-D by mechanically scanning a volume witha linear probe, by co-aligning multiple linear probes, by usingmultiplexed 3-D clinical ultrasound systems, or by using 3-D ultrasound research systems. In this study, a 2-D sparsearray was designed with 512 elements according to a density-tapered 2-D spiral layout and optimized to reduce the sidelobesof the transmitted beam profile. High frame rate volumetricimaging with compounded plane waves was performed usingtwo synchronized ULA-OP256 systems. Localization-based 3-Dsuper-resolution images of two touching sub-wavelength tubeswere generated from a 120 second acquisition.
Harput S, Christensen-Jeffries K, Brown J, et al., 2018, 3-D motion correction for volumetric super-resolution ultrasound (SR-US) imaging, IEEE International Ultrasonics Symposium (IUS) 2018, Publisher: IEEE
Motion during image acquisition can cause imagedegradation in all medical imaging modalities. This is particularlyrelevant in 2-D ultrasound imaging, since out-of-plane motioncan only be compensated for movements smaller than elevationalbeamwidth of the transducer. Localization based super-resolutionimaging creates even a more challenging motion correction taskdue to the requirement of a high number of acquisitions to forma single super-resolved frame.In this study, an extension of two-stage motion correctionmethod is proposed for 3-D motion correction. Motion estimationwas performed on high volumetric rate ultrasound acquisitionswith a handheld probe. The capability of the proposed methodwas demonstrated with a 3-D microvascular flow simulation tocompensate for handheld probe motion. Results showed that two-stage motion correction method reduced the average localizationerror from 136 to 18μm.
Zhou X, Zhou X, Leow CH, et al., 2018, 3D Flow Reconstruction and Wall Shear Stress Evaluation with 2D Ultrafast Ultrasound Particle Imaging Velocimetry, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
Brown J, Kolas S, Christensen-Jeffries K, et al., 2018, Development of Simultaneous Optical Imaging and Super-Resolution Ultrasound to Improve Microbubble Localization Accuracy, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
Christensen-Jeffries K, Harput S, Brown J, et al., 2018, 3D In Vitro Ultrasound Super-Resolution Imaging using a Clinical System, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
Stanziola A, Toulemonde M, Corbett R, et al., 2018, Benefits of adaptive beamforming methods for contrast enhanced high frame-rate ultrasound, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
Zhou X, Leow CH, Rowland E, et al., 2018, 3D velocity and volume flow measurement in vivo using speckle decorrelation and 2D high frame rate contrast-enhanced ultrasound, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Vol: 65, Pages: 2233-2244, ISSN: 0885-3010
Being able to measure 3D flow velocity and volumetric flow rate effectively in the cardiovascular system is valuable but remains a significant challenge in both clinical practice and research. Currently there has not been an effective and practical solution to the measurement of volume flow using ultrasound imaging systems due to challenges in existing 3D imaging techniques and high system cost. In this study, a new technique for quantifying volumetric flow rate from the cross-sectional imaging plane of the blood vessel was developed by using speckle decorrelation, 2D high frame rate imaging with a standard 1D array transducer, microbubble contrast agents, and ultrasound imaging velocimetry (UIV). Through speckle decorrelation analysis of microbubble signals acquired with a very high frame rate and by using UIV to estimate the two in-plane flow velocity components, the third and out-of-plane velocity component can be obtained over time and integrated to estimate volume flow. The proposed technique was evaluated on a wall-less flow phantom in both steady and pulsatile flow. UIV in the longitudinal direction was conducted as a reference. The influences of frame rate, mechanical index, orientation of imaging plane, and compounding on velocity estimation were also studied. In addition, an in vivo trial on the abdominal aorta of a rabbit was conducted. The results show that the new system can estimate volume flow with an averaged error of 3.65±2.37% at a flow rate of 360 ml/min and a peak velocity of 0.45 m/s, and an error of 5.03±2.73% at a flow rate of 723 ml/min and a peak velocity of 0.8 m/s. The accuracy of the flow velocity and volumetric flow rate estimation directly depend on the imaging frame rate. With a frame rate of 6000 Hz, a velocity up to 0.8 m/s can be correctly estimated. A higher mechanical index (MI=0.42) is shown to produce greater errors (up to 21.78±0.49%, compared to 3.65±2.37% at MI=0.19). An in vivo trial, where velo
Tang M-X, Tortoli P, 2018, Introduction to the Special Issue on High Frame Rate/Ultrafast Contrast-Enhanced Ultrasound Imaging, IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL, Vol: 65, Pages: 2210-2211, ISSN: 0885-3010
Toulemonde MEG, Li Y, Lin S, et al., 2018, High-frame-rate contrast echocardiography using diverging waves: initial in-vitro and in-vivo evaluation, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Vol: 65, Pages: 2212-2221, ISSN: 0885-3010
Contrast Echocardiography (CE) ultrasound with microbubble contrast agents (UCA) has significantly advanced our capability for assessment of cardiac function, including myocardium perfusion quantification. However in standard CE techniques obtained with line by line scanning, the frame rate and image quality are limited. Recent research has shown significant frame rate improvement in non-contrast cardiac imaging. In this work we present and initially evaluate, both in-vitro and in-vivo, a high frame rate (HFR) CE imaging system using diverging waves and pulse inversion sequence. An imaging frame rate of 5500 frames per second before and 250 frames per second after compounding is achieved. A destruction-replenishment sequence has also been developed. The developed HFR CE is compared with standard CE in-vitro on a phantom and then in-vivo on a sheep heart. The image signal to noise ratio, contrast between the myocardium and the chamber are evaluated. Results show up to 13.4 dB improvement in contrast for HFR CE over standard CE when compared at the same display frame-rate even when the average spatial acoustic pressure in HFR CE is 36% lower than the standard CE. It is also found that when coherent compounding is used the HFR CE image intensity can be significantly modulated by the flow motion in the chamber.
Stanziola A, Leow CH, Bazigou E, et al., 2018, ASAP: super-contrast vasculature imaging using coherence analysis and high frame- rate contrast enhanced ultrasound, IEEE Transactions on Medical Imaging, Vol: 37, Pages: 1847-1856, ISSN: 0278-0062
The very high frame rate afforded by ultrafast ultrasound, combined with microbubble contrast agents, opens new opportunities for imaging tissue microvasculature. However, new imaging paradigms are required to obtain superior image quality from the large amount of acquired data while allowing real-time implementation. In this paper, we report a technique - acoustic sub-aperture processing (ASAP) - capable of generating very high contrast/SNR images of macro- and microvessels, with similar computational complexity to classical Power Doppler (PD) imaging. In ASAP, the received data are split into sub- groups. The reconstructed data from each sub-group are temporally correlated over frames to generate the final image. As signals in sub-groups are correlated but the noise is not, this substantially reduces the noise floor compared to PD. Using a clinical imaging probe, the method is shown to visualize vessels down to 200μm with a SNR 10dB higher than PD, and to resolve microvascular flow/perfusion information in rabbit kidneys non-invasively in vivo at multiple centimeter depth. With careful filter design, the technique also allows estimation of flow direction and separation of fast flow from tissue perfusion. ASAP can readily be implemented into hardware/firmware for real-timing imaging, and can be applied to contrast enhanced and potentially non-contrast imaging and 3D imaging.
Toulemonde M, Zhang G, Riemer K, et al., 2018, Locally activated nanodroplets and high frame rate imaging for real-time flow visualization – preliminary in-vivo demonstration, BioMedEng18
Zhang G, Harput S, Lin S, et al., 2018, Acoustic wave sparsely activated localization microscopy (AWSALM): super-resolution ultrasound imaging using acoustic activation and deactivation of nanodroplets, Applied Physics Letters, Vol: 113, Pages: 014101-1-014101-5, ISSN: 0003-6951
Photo-activated localization microscopy (PALM) has revolutionized the field of fluorescence microscopy by breaking the diffraction limit in spatial resolution. In this study, “acoustic wave sparsely activated localization microscopy (AWSALM),” an acoustic counterpart of PALM, is developed to super-resolve structures which cannot be resolved by conventional B-mode imaging. AWSALM utilizes acoustic waves to sparsely and stochastically activate decafluorobutane nanodroplets by acoustic vaporization and to simultaneously deactivate the existing vaporized nanodroplets via acoustic destruction. In this method, activation, imaging, and deactivation are all performed using acoustic waves. Experimental results show that sub-wavelength micro-structures not resolvable by standard B-mode ultrasound images can be separated by AWSALM. This technique is flow independent and does not require a low concentration of contrast agents, as is required by current ultrasound super resolution techniques. Acoustic activation and deactivation can be controlled by adjusting the acoustic pressure, which remains well within the FDA approved safety range. In conclusion, this study shows the promise of a flow and contrast agent concentration independent super-resolution ultrasound technique which has potential to be faster and go beyond vascular imaging.
Toulemonde MEG, Corbett R, Papadopoulou V, et al., 2018, High frame rate contrast echocardiography –in human demonstration, JACC: Cardiovascular Imaging, Vol: 11, Pages: 923-924, ISSN: 1936-878X
Papadopoulou V, Germonpre P, Cosgrove D, et al., 2018, Variability in circulating gas emboli after a same scuba diving exposure, EUROPEAN JOURNAL OF APPLIED PHYSIOLOGY, Vol: 118, Pages: 1255-1264, ISSN: 1439-6319
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- Citations: 34
Harput S, Christensen-Jeffries K, Brown J, et al., 2018, Two-stage motion correction for super-resolution ultrasound imaging in human lower limb, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, Vol: 65, Pages: 803-814, ISSN: 0885-3010
The structure of microvasculature cannot be resolved using conventional ultrasound imaging due to the fundamental diffraction limit at clinical ultrasound frequencies. It is possible to overcome this resolution limitation by localizing individual microbubbles through multiple frames and forming a super-resolved image, which usually requires seconds to minutes of acquisition. Over this time interval, motion is inevitable and tissue movement is typically a combination of large and small scale tissue translation and deformation. Therefore, super-resolution imaging is prone to motion artefacts as other imaging modalities based on multiple acquisitions are. This study investigates the feasibility of a two-stage motion estimation method, which is a combination of affine and non-rigid estimation, for super-resolution ultrasound imaging. Firstly, the motion correction accuracy of the proposed method is evaluated using simulations with increasing complexity of motion. A mean absolute error of 12.2 μm was achieved in simulations for the worst case scenario. The motion correction algorithm was then applied to a clinical dataset to demonstrate its potential to enable in vivo super-resolution ultrasound imaging in the presence of patient motion. The size of the identified microvessels from the clinical super-resolution images were measured to assess the feasibility of the two-stage motion correction method, which reduced the width of the motion blurred microvessels approximately 1.5-fold.
Li Y, Ho CP, Toulemonde M, et al., 2018, Fully automatic myocardial segmentation of contrast echocardiography sequence using random forests guided by shape model, IEEE Transactions on Medical Imaging, Vol: 37, Pages: 1081-1091, ISSN: 0278-0062
Myocardial contrast echocardiography (MCE) is animaging technique that assesses left ventricle function and myocardialperfusion for the detection of coronary artery diseases.Automatic MCE perfusion quantification is challenging and requiresaccurate segmentation of the myocardium from noisy andtime-varying images. Random forests (RF) have been successfullyapplied to many medical image segmentation tasks. However, thepixel-wise RF classifier ignores contextual relationships betweenlabel outputs of individual pixels. RF which only utilizes localappearance features is also susceptible to data suffering fromlarge intensity variations. In this paper, we demonstrate howto overcome the above limitations of classic RF by presentinga fully automatic segmentation pipeline for myocardial segmentationin full-cycle 2D MCE data. Specifically, a statisticalshape model is used to provide shape prior information thatguide the RF segmentation in two ways. First, a novel shapemodel (SM) feature is incorporated into the RF frameworkto generate a more accurate RF probability map. Second, theshape model is fitted to the RF probability map to refineand constrain the final segmentation to plausible myocardialshapes. We further improve the performance by introducinga bounding box detection algorithm as a preprocessing stepin the segmentation pipeline. Our approach on 2D image isfurther extended to 2D+t sequences which ensures temporalconsistency in the final sequence segmentations. When evaluatedon clinical MCE datasets, our proposed method achieves notableimprovement in segmentation accuracy and outperforms otherstate-of-the-art methods including the classic RF and its variants,active shape model and image registration.
Li Y, Tang MX, Agarwal R, et al., 2018, Power Doppler Quantification in Assessing Gestational Trophoblastic Neoplasia, ULTRASCHALL IN DER MEDIZIN, Vol: 39, Pages: 206-212, ISSN: 0172-4614
Lin S, Zhang G, Jamburidze A, et al., 2018, Imaging of vaporised sub-micron phase change contrast agents with high frame rate ultrasound and optics., Phys Med Biol, Vol: 63, Pages: 065002-065002
Phase-change ultrasound contrast agent (PCCA), or nanodroplet, shows promise as an alternative to the conventional microbubble agent over a wide range of diagnostic applications. Meanwhile, high-frame-rate (HFR) ultrasound imaging with microbubbles enables unprecedented temporal resolution compared to traditional contrast-enhanced ultrasound imaging. The combination of HFR ultrasound imaging and PCCAs can offer the opportunity to observe and better understand PCCA behaviour after vaporisation captures the fast phenomenon at a high temporal resolution. In this study, we utilised HFR ultrasound at frame rates in the kilohertz range (5-20 kHz) to image native and size-selected PCCA populations immediately after vaporisation in vitro within clinical acoustic parameters. The size-selected PCCAs through filtration are shown to preserve a sub-micron-sized (mean diameter < 200 nm) population without micron-sized outliers (>1 µm) that originate from native PCCA emulsion. The results demonstrate imaging signals with different amplitudes and temporal features compared to that of microbubbles. Compared with the microbubbles, both the B-mode and pulse-inversion (PI) signals from the vaporised PCCA populations were reduced significantly in the first tens of milliseconds, while only the B-mode signals from the PCCAs were recovered during the next 400 ms, suggesting significant changes to the size distribution of the PCCAs after vaporisation. It is also shown that such recovery in signal over time is not evident when using size-selective PCCAs. Furthermore, it was found that signals from the vaporised PCCA populations are affected by the amplitude and frame rate of the HFR ultrasound imaging. Using high-speed optical camera observation (30 kHz), we observed a change in particle size in the vaporised PCCA populations exposed to the HFR ultrasound imaging pulses. These findings can further the understanding of PCCA
Bamber J, Shah A, Bush N, et al., 2018, Photoacoustic imaging and contrast agents in cancer research, Leeds Microbubble Symposium
Cox K, Taylor-Phillips S, Sharma N, et al., 2018, Enhanced pre-operative axillary staging using intradermal microbubbles and contrast-enhanced ultrasound to detect and biopsy sentinel lymph nodes in breast cancer: a potential replacement for axillary surgery, BRITISH JOURNAL OF RADIOLOGY, Vol: 91, ISSN: 0007-1285
Harput S, Christensen-Jeffries K, Brown J, et al., 2017, Ultrasound Super-Resolution with Microbubble Contrast Agents, 16th IEEE SENSORS CONFERENCE, Publisher: IEEE, Pages: 1104-1106, ISSN: 1930-0395
Ultrasound super-resolution imaging can be achieved by localizing spatially isolated microbubble contrast agents over multiple imaging frames. In vivo images with resolutions of ~10-20 microns in deep tissue have been demonstrated. The technique has the potential to revolutionize the way micro-circulation can be visualized and quantified, and has implications in a wide range of clinical applications including cancer, diabetes and beyond. In this paper we describe the principle of the technique with in vivo results demonstrating the superior resolution achieved compared with existing ultrasound imaging. We also discuss the challenges and opportunities in the area of 3D imaging including, imaging speed, tissue motion and microbubble localization errors.
Toulemonde M, Duncan WC, Leow C-H, et al., 2017, Cardiac flow mapping using high frame rate diverging wave contrast enhanced ultrasound and image tracking, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
Contrast echocardiography (CE) ultrasound with microbubble contrast agents have significantly advanced our capability in assessing cardiac function. However in conventional CE techniques with line by line scanning, the frame rate is limited to tens of frames per second, making it difficult to track the fast flow within cardiac chamber. Recent research in high frame-rate (HFR) ultrasound have shown significant improvement of the frame rate in non-contrast cardiac imaging. In this work we show the feasibility of microbubbles flow tracking in HFR CE acquisition in vivo with a high temporal resolution and low MI as well as the detection of vortex near the valves during filling phases agreeing with previous study.
Toulemonde M, Stanziola A, Li Y, et al., 2017, Effects of motion on high frame rate contrast enhanced echocardiography and its correction, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
Contrast echocardiography (CE) ultrasound with microbubble contrast agents have significantly advanced our capability in assessing cardiac function, including myocardium perfusion imaging and quantification. However in conventional CE techniques with line by line scanning, the frame rate is limited to tens of frames per second and image quality is low. Recent research works in high frame-rate (HFR) ultrasound have shown significant improvement of the frame rate in non-contrast cardiac imaging. But with a higher frame rate, the coherent compounding of HFR CE images shows some artifacts due to the motion of the microbubbles. In this work we demonstrate the impact of this motion on compounded HFR CE in simulation and then apply a motion correction algorithm on in-vivo data acquired from the left ventricle (LV) chamber of a sheep. It shows that even if with the fast flow found inside the LV, the contrast is improved at least 100%.
Toulemonde M, Eckersley RJ, Tang M-X, 2017, High frame rate contrast enhanced echocardiography: microbubbles stability and contrast evaluation, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
Contrast Echocardiography (CE) with microbubble contrast agents have significantly advanced our capability in assessing cardiac function, including myocardium perfusion imaging and quantification. However in conventional CE techniques with line by line scanning, the frame rate is limited to tens of frames per second and image quality is low. Recent works in high frame-rate (HFR) ultrasound have shown significant improvement of the frame rate. The aim of this work is to investigate the MBs stability and the contrast improvement using HFR CE compared to CE transmission at an echocardiography relevant frequency for different mechanical indices (MIs). Our results show that the contrast and bubble destruction of HFR CE and standard CEUS varies differently as a function of space and MIs. At low MIs, HFR CE shows a similar behavior as focused CE with little MB destruction, and generates better CTR (up to 3 folds). As MI increases, the MB destruction is more significant for HFR CE with a reduction of the CTR.
Leow CH, Marta B, Stanziola A, et al., 2017, Multi-Frame Rate Plane Wave Contrast-Enhance Ultrasound Imaging for Tumour Vasculature Imaging and Perfusion Quantification, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
A multi-frame rate plane wave imaging strategy is developed to simultaneously image tumor vasculature and quantify tumor perfusion. Customised imaging sequences interleaving a short but high frame rate (HFR) plane wave imaging sequence with a long but low frame rate imaging (LFR) sequence were implemented using a programmable ultrasound research platform. The results from a spatio-temporal coherence processing technique of ours demonstrated a significant improvement in the SNR and vasculature contrast when compared with the existing ultrafast Power Doppler (PD) using the same data. Initial perfusion quantification using LFR imaging was also demonstrated. Mean time intensity curve and some parametric measures were generated. Combining both structural and functional perfusion imaging using the multiframe rate sequences, a better evaluation of the tumour angiogenesis can be assessed.
Brown J, Christensen-Jeffries K, Harput S, et al., 2017, Investigation of microbubble detection methods for super-resolution imaging of microvasculature, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
Harput S, Christensen-Jeffries K, Li Y, et al., 2017, Two Stage Sub-Wavelength Motion Correction in Human Microvasculature for CEUS Imaging, IEEE International Ultrasonics Symposium (IUS), Publisher: IEEE, ISSN: 1948-5719
The structure of microvasculature cannot be resolved using clinical B-mode or contrast-enhanced ultrasound (CEUS) imaging due to the fundamental diffraction limit at clinical ultrasound frequencies. It is possible to overcome this resolution limitation by localizing individual microbubbles through multiple frames and forming a super-resolved image. However, ultrasound super-resolution creates its unique problems since the structures to be imaged are on the order of 10s of μm. Tissue movement much larger than 10 μm is common in clinical imaging, which can significantly reduce the accuracy of super-resolution images created from microbubble locations gathered through hundreds of frames. This study investigated an existing motion estimation algorithm from magnetic resonance imaging for ultrasound super-resolution imaging. Its correction accuracy is evaluated using simulations with increasing complexity of motion. Feasibility of the method for ultrasound super-resolution in vivo is demonstrated on clinical ultrasound images. For a chosen microvessel, the super-resolution image without motion correction achieved a sub-wavelength resolution; however after the application of proposed two-stage motion correction method the size of the vessel was reduced to half.
Harput S, Christensen-Jeffries K, Brown J, et al., 2017, Localisation of multiple non-isolated microbubbles with frequency decomposition in super-resolution imaging, IEEE International Ultrasonics Symposium, IUS, Publisher: IEEE, ISSN: 1948-5719
Sub-diffraction imaging, also known as ultrasound localization microscopy, is a novel method that can overcome the fundamental diffraction limit by localizing spatially isolated microbubbles. This method requires the use of a low concentration of microbubbles to ensure that they are spatially isolated. For in vivo microvascular imaging, especially for cancer tissue with high microvascular density, spatial isolation cannot be always achieved, since vessels are close to each other and the speed of flow is slow. This study proposes a frequency decomposition method that uses the polydisperse nature of commercial contrast agents to separate spatially non-isolated microbubbles with different acoustic signatures. Zero-phase filters were applied to ensure that there is no relative phase delay between decomposed signals. Results showed that a super-resolution image after frequency decomposition can be generated with three times lower number of acquisitions without sacrificing image quality.
Bamber J, Eckersley RJ, Harvey C, et al., 2017, In Memoriam: David Cosgrove (1938-2017), Ultrasound in Medicine and Biology, ISSN: 0301-5629
Cox K, Taylor-Phillips S, Weeks J, et al., 2017, Enhanced pre-operative axillary staging using intradermal microbubbles and contrast enhanced ultrasound in breast cancer patients at Maidstone Hospital: Test performance of individual radiologists, Annual Scientific Meeting of the British-Society-of-Breast-Radiology, Publisher: BMC, ISSN: 1465-542X
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