Week 20
Synthetic Aperture Sequential Beamforming applied to medical imaging
Synthetic Aperture Sequential Beamforming (SASB) is applied to medical ultrasound imaging using a multi element convex array transducer.
The main motivation for SASB is to apply synthetic aperture techniques without the need for storing RF-data for a number of elements and hereby devise a system with a reduced system complexity. Using a 192 element, 3.5 MHz, λ-pitch transducer, it is demonstrated using tissue-phantom and wire-phantom measurements, how the speckle size and the detail resolution is improved compared to conventional imaging.
Measured PSF at depths of 41 and 91 mm obtained using a water tank phantom. The figures (a+c) is made using DRF and (b+d) using SASB
Hemmsen, Martin Christian, Hansen, Jens Munk, Jensen, Jørgen Arendt
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Week 19
Imaging blood's velocity using synthetic aperture ultrasound
The blood velocity vector can be estimated using synthetic aperture techniques in medical ultrasound by using short emission sequences. The whole image region is insonified and the flow can be tracked in all directions continuously. This is a major advantage compared to commercial systems, since the separation between blood and tissue is greatly eased by this, and the estimates can be averaged over long time than in traditional systems.
Vector velocity imaging can, thus, be made and attain an order of magnitude higher precision than in current commercial systems and at higher frame rates. It is also possible to visualize very slow moving flow. The paper will present methods for making such imaging.
Conventional color flow map image of the internal carotid artery.
Jensen, Jørgen Arendt and Li, Ye
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Week 18
Spatial impulse response of a rectangular double curved transducer
Calculation of the pressure field from transducers having both a convex and a concave surface geometry is a complicated assignment that often is accomplished by subdividing the transducer surface into smaller flat elements of which the spatial impulse response is known. This method
is often seen applied to curved transducers because an analytical solution is un-known. In this work a semi-analytical algorithm for the exact solution to a first order in diffraction effect of the spatial impulse response of rectangular shaped double curved transducers is presented.
The algorithm and an approximation of it are investigated. The approximation reformulates the algorithm to an analytically integrable expression which is computationally efficient to solve. Simulation results are compared with the simulation software Field II. Calculating the response from 200 different points yields a mean error for the different approximations ranging from 0.03 % to 0.8 % relative to a numerical solution for the spatial impulse response. It is shown that the presented algorithm gives consistent results with Field II for a linear flat, a linear focused, and a convex non-focused element. Best solution was found to be 0.01 % with a three-point Taylor expansion.
Bæk, David; Jensen, Jørgen Arendt and Willatzen, Morten
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Week 15-17, 2012
The world's most powerful ultrasound scanner
In cooperation with Prevas A/S and BK Medical, Center for Fast Ultrasound Imaging has developed the world's most powerful research scanner for medical ultrasound.
The new scanner was completed in January 2012 and is capable of acquiring data from advanced 2 dimensional transducers with up to 1,024 elements. For each element, data is measured 70 million times per second.
The full scanner generates 140 Gbytes per second, corresponding to 75,000 simultaneous HD TV channel. The build-in data power of the system corresponds to 5,000 PCs and can acquire and process data in real time.
We are developing tomorrow's ultrasound systems and test the methods in close cooperation with the Radiological Department at Copenhagen University Hospital.
Week 11-15, 2012
In vivo evaluation of synthetic aperture sequential beamforming
The basic idea in synthetic aperture techniques is to synthesize a large aperture by moving or multiplexing a small active aperture over a larger array. There are several variants of the technique for ultrasonic imaging that all make it possible to generate images with dynamic focusing during both transmit and receive.
In this article, a novel implementation of twodimensional (2-D) SASB imaging is evaluated in a more comprehensive clinical trial using eighteen healthy volunteers and evaluated by ultrasound specialists (medical doctors). The method is investigated for abdominal imaging using a multi-element convex array transducer and it is compared with conventional convex array imaging. The investigation is based on a double blinded clinical evaluation using paired image sequences.
A data acquisition system capable of producing simultaneous recordings of the exact same locations using both techniques is used.
Transverse scanning of liver
Martin Christian Hemmsen, Peter Møller Hansen, Theis Lange, Jens Munk Hansen, Kristoffer Lindskov Hansen, Michael Bachmann Nielsen and Jørgen Arendt Jensen
Elsevier, Ultrasound in Med. & Biol., Vol. 38, No. 4, pp. 708–716, 2012
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Week 10, 2012
Preliminary comparison of 3D synthetic aperture imaging with Explososcan
Explososcan is the 'gold standard' for real-time 3D medical ultrasound imaging.
In this paper, 3D synthetic aperture imaging is compared to Explososcan by simulation of 3D point spread functions.
There are still many variables to be optimized for the implemented synthetic aperture, but from the simulated point spread functions, it is estimated that synthetic aperture achieves a better imaging quality for medical imaging, than Explososcan. This is based mainly on synthetic aperture's better cystic resolution performance.
Traditional synthetic aperture Synthetic aperture with beam steering
Morten Fischer Rasmussen, Jens Munk Hansen, Guillaume Férin, Rémi Dufait and Jørgen Arendt Jensen
Presented at: SPIE Medical Imaging. San Diego, California United States, 2012
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Week 9, 2012
Age and gender related differences in aortic blood flow
Cardiovascular diseases are a leading cause of death worldwide and accounted for 30% of all deaths in 2005.
The age-related changes in the abdominal aorta (AA) configuration, the AA mechanical properties, and, as a consequence, the changes in blood flow properties, are suspected to play an important role.
Computational fluid dynamics (CFD) is a valuable tool in the inspection and quantification of changes in blood flow properties in the human AA. The purpose of this study is to investigate the influence of age and gender in blood flow properties in the AA using this tool.
Example of (a) the setup on the ProFocus scanner and (b) the CFU Grabber GUI during acquisition of the blood flow data. The range gate is marked by the white solid lines in the B-mode image in (a). In the CFU Grabber GUI in (b) the functions are listed to the left and activated by point-and-click.
Marie Sand Enevoldsen, Mads Møller Pedersen, Martin Christian Hemmsen, Lars Lönn, Kaj-Åge Henneberg and Jørgen Arendt Jensen
Presented at: SPIE Medical Imaging. San Diego, California United States, 2012
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Week 8, 2012
Clinical evaluation of synthetic aperture sequential beamforming
In virtually all surgical and internal medicine specialties, ultrasound scanning is a very important diagnostic tool. It is being used for e.g. prenatal screening, diagnosis and assessment of cardiovascular disease, numerous cancer types, musculoskeletal disease, and traumatic organ damage.
In this study, clinically relevant ultrasound images generated with synthetic aperture sequential beamforming (SASB) are compared to images generated with a conventional technique. The advantage of SASB is the ability to produce high resolution ultrasound images with a high frame rate and at the same time massively reduce the amount of generated data. SASB was implemented in a system consisting of a conventional ultrasound scanner connected to a PC via a research interface. This setup enables simultaneous recording with both SASB and conventional technique.
Images were evaluated in terms of spatial resolution, contrast, unwanted artifacts, and penetration depth of the ultrasound beam. Five ultrasound experts (radiologists) evaluated the sequence pairs in a side-by-side comparison, and the results show that image quality using SASB was better than conventional B-mode imaging.
Screen shots from the evaluation software. In the lower right corner the sequence controls are seen. (a) shows an example of the image quality evaluation. The sliding bar used for the actual evaluation is positioned in the bottom of the image. (b) shows an example of the penetration depth evaluation. The sliding bar used for the actual evaluation is shown across the bottom of the image
Hansen, Peter Møller; Hemmsen, Martin Christian; Lange, Theis; Hansen, Jens Munk; Nielsen, Michael Bachmann; Jensen, Jørgen Arendt
Presented at: SPIE Medical Imaging. San Diego, California United States, 2012
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Week 6 + 7, 2012
Ultrasound pulse-echo measurements on rough surfaces with linear array transducers
Despite being easy, quick, portable and safe, ultrasound imaging suffers from a number of artefacts. One is that the images are angle-dependent due to the angle-dependence of the echoes received from interfaces larger than the wavelength of the ultrasound energy emitted.
We have previously studied the influence of roughness, angle and range between transducer and interface as well as transducer type on the echo signal from planar interfaces for a number of different single-element transducers - in the present study, the same effects have been studied quantitatively for a linear array transducer on a commercially available ultrasound scanner at two different frequencies.
Measurements from the smooth surface show a high degree of angle-dependence with a span of 18 dB in the angle range. Surfaces with a roughness smaller than the wavelength also show some angle-dependence, whereas surfaces with roughness comparable to or larger than the wavelength show virtually no angle-dependence with a span of only 2 dB in the angle range. Measurements with linear array transducers are less dependent on the angle than measurements with single-element focused transducers.
Measurement setup seen from above. Transducer placed in the middle of the image with angled phantom below.
Sjøj, Sidsel M. N.; Blanco, Esther N.; Wilhjelm, Jens E.; Jensen, Henrik; Hemmsen, Martin Christian; Jensen, Jørgen Arendt
Presented at: ICU International Congress on Ultrasonics. Gdansk, Poland, 2011
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Week 5, 2012
Comparison of Real-Time In Vivo Spectral and Vector Velocity Estimation
The purpose of this study is to show whether a newly introduced vector flow method is equal to conventional spectral estimation. Thirty-two common carotid arteries of 16 healthy volunteers were scanned using a BK Medical ProFocus scanner and a linear transducer at 5 MHz. Several clinical parameters were estimated and compared for the two methods: Flow angle, peak systole velocity, end diastole velocity and resistive index. With a paired t-test, the spectral and vector angles did not differ significantly, whereas PS, ED and RI differed significantly. Vector flow can measure the angle for spectral angle correction, thus eliminating the bias from the radiologist performing the angle setting with spectral estimation. The flow angle limitation in velocity estimation is also eliminated, so that flow at any angle can be measured.
Simultaneous data acquisition using spectral estimation and transverse oscillation. The manually set flow angle and the spectral estimation results are marked in red at the lower left of the image. The color encoded vector values are decoded using the color map shown in the top, right corner
Comparison of Real-Time In Vivo Spectral and Vector Velocity Estimation
Mads Møller Pedersen, Michael Johannes Pihl, Per Haugaard, Jens Munk Hansen, Kristoffer Lindskov Hansen, Michael Bachmann Nielsen, and Jørgen Arendt Jensen.
Week 4, 2012
Simulation of Shadowing Effects in Ultrasound Imaging from Computed Tomography Images
Simulation of US images based on CT data has previously been performed with different methods. Shadowing effects are normally pronounced in US images, so they should be included in the simulation.
In this work, a new method to introduce shadowing effects has been tested that makes the simulated US image from the CT image appear more realistic. The experiment provides the US data for assessment of the simulation results as well as instrument parameters and CT data for the simulation process. The method emphasizes the necessity of mapping the Hounsfield Unit to the backscattering, attenuation coefficients and characteristic acoustic impedance in the simulation of US images from CT images.
The TRC map for US focused beam tracing model
Simulation of Shadowing Effects in Ultrasound Imaging from Computed Tomography Images
by: An Hoia Pham. Paper presented at the IEEE International Ultrasonics Symposium, Orlando, Florida, 2011
Week 3, 2012
Synthetic Aperture Beamformation using the GPU
Image quality and diagnostic capabilities of medical imaging depend on the inversion of the measured data for the given modality. For ultrasound imaging, the inversion is primarily made by delay-and-sum beamformation. This comprises computation and application of channel delays and apodization for both the emissions and the individual receiving elements. Ideally, one would like the result of the beamformation to approximate the true inverse of the forward model, which itself is a complex model of both time and space. A forward model or simulation model is described by the ultrasound simulation program Field II.
An equally high demand for memory throughput is found in the computer gaming industry, where hundreds of megabytes of data are processed every second for rendering a scene in a 3D computer game. The processing takes place on the graphics processing unit (GPU), which is a many-core massively parallel throughput-oriented execution unit. It contains a lot of arithmetic logic units (ALUs) and is suitable for single-instruction-multiple-data (SIMD) execution.
In this paper, the most recent framework, OpenCL [5] is used for SA beamformation of ultrasound data. Previous work has already done using multiple GPUs for SA beamformation of ultrasound data. This work is different in the way that a more advanced apodization is used and the beamformer can be configured using Matlab.
Synthetic Aperture Beamformation using the GPU
by: Jens Munk Hansen, Dana Schaa and Jørgen Arendt Jensen. Paper presented at the IEEE International Ultrasonics Symposium, Orlando, Florida, 2011
Week 2, 2012
Patient-Specific models of the Abdominal Aorta with and without Aneurysms
This research study presents computational simulation models for analysis of parameters which are in evidence of development and clinical management of abdominal aortic aneurysms (AAA). The research covers three main areas: interpretation of material parameters,
implementation of the constitutive relations for computational analysis, and evaluation of the material model predictability.
The purpose of the study was to investigate whether significant risk factors related to AAA development can be identified from a specific pattern in material parameters and aimed at developing computational simulation models incorporating subject-specific geometry of the abdominal aorta (AA) as well as subject-specific blood flow conditions. The geometry was acquired from magnetic resonance imaging, and the blood flow characteristics were acquired from ultrasound.
Example of an abdominal aortic aneurysm
Patient-Specific models of the Abdominal Aorta with and without Aneurysms
by: Marie Sand Enevoldsen. PhD thesis, to be defended 11 January 2012
Week 1, 2012
Third Harmonic Imaging using Pulse Inversion
Tissue harmonic imaging is a technique widely used in commercial ultrasound systems to improve spatial resolution. In harmonic B-mode imaging, however, an overlap is often seen between the harmonic components in the received RF signal, making separation of a single harmonic band difficult.
The pulse inversion (PI) technique can be utilized to separate and enhance harmonic components of a waveform for tissue harmonic imaging. While most ultrasound systems can perform pulse inversion, only few image the 3rd harmonic component. PI pulse subtraction can isolate and enhance the 3rd harmonic component for imaging on any ultrasound system capable of PI.
This paper describes how third harmonic B-mode imaging has successfully been accomplished using SARUS. The lateral resolution of the 3rd harmonic image is determined to be higher than that of 2nd harmonic and fundamental B-mode imaging.
The point spread functions (PSF) of the fundamental pulse (top), 2nd harmonic pulse (middle), and 3rd harmonic pulse (bottom). The PSFs are displayed with 6dB contour lines
Third Harmonic Imaging using Pulse Inversion
by: Joachim Hee Rasmussen, Yigang Du and Jørgen Arendt Jensen. Presented at the IEEE International Ultrasonics Symposium, Orlando Florida, 2011
Week 51 + 52, 2011
Second harmonic imaging using synthetic aperture sequential beamforming
Synthetic aperture imaging is a well-know ultrasound imaging method, where dynamic focusing can
be achieved in both transmit and receive. In conventional synthetic aperture imaging a single element is used for emissions to simulate a spherical wave. The major drawback is that the transmitting energy for a single element is too low, so that the harmonic signals are very weak. Synthetic aperture sequential beamforming is a novel technique, also called dual-stage beamforming. The advantage is that the lateral resolution is improved independently of image depth compared to the conventional ultrasound imaging.
This paper investigates Second Harmonic Imaging using Synthetic Aperture Sequential Beamforming.
Pulses and envelops in the axial direction using different imaging methods - These show the center image lines for DRFI, DRFSHI, SASBI, SASBSHI and their envelopes. The plots show the second point target (P2) along the scanning depth and is around 47.5 mm from the transducer surface. The transmit foci is 50 mm for DRFI and DRFSHI, and it is 10 mm for SASBI and SASBSHI
Second harmonic imaging using synthetic aperture sequential beamforming
by: Yigang Du, Joachim Rasmussen, Henrik Jensen and Jørgen Arendt Jensen
Week 50
Scalable Intersample Interpolation Architecture for High-channelcount Beamformers
Medical ultrasound imaging is a well-established diagnostic modality, characterized by short preparation time, lack of side effects, portability and a low price compared to other imaging modalities. The vast majority of commercial ultrasound scanners feature a digital beamformer and employ delay-and-sum focusing of the digitized echo signals from the tissue. The quality of the focusing is directly dependent on the timing precision with which it is done.
This paper presents methods for combining filter-based interpolation with focusing and summing logic which greatly reduces the computational and the coefficient storage demands in high channel count systems.
Filtering of an upsampled signal: The differently colored subsets of the filter coefficients create the identically colored output samples.
Scalable Intersample Interpolation Architecture for High-channelcount Beamformers
by: Borislav Georgiev Tomov, Svetoslav Ivanov Nikolov and Jørgen Arendt Jensen
Week 49
Preliminary In-Vivo evaluation of Synthetic Aperture Sequential Beamformation using a multielement convex array
The paper presents a preliminary in-vivo study of synthetic aperture sequential beamforming (SASB) in comparison with conventional imaging. The advantage of SASB is the ability to obtain a more range independent point spread function, without any loss in lateral resolution or frame rate. The objective was to evaluate whether SASB imaging is feasible in-vivo and whether the image quality obtained is comparable with traditional scanned imaging in terms of penetration depth, spatial resolution, contrast, and unwanted artifacts.
The result of the statistical evaluation showed that SASB imaging can obtain satisfying penetration within the current intensity limits. Furthermore, the image quality evaluation showed highly significant improvement in SASB images compared with conventional images. One should be careful about interpreting the absolute VAS values, since the interobserver variation in VAS scale interpretation is large. The conclusion is important for future development of ultrasound imaging. Especially for a future towards cheaper devices with more processing done by standard PC’s.
Visualization of an image pair for overall image quality evaluation. The scale used for scoring is shown in the bottom and the control panel for navigating the sequences are shown in the lower right corner.
Preliminary In-Vivo evaluation of Synthetic Aperture Sequential Beamformation using a multielement convex array
by: Martin Christian Hemmsen, Peter Møller Hansen, Theis Lange, Jens Munk Hansen, Svetoslav Ivanov Nikolov, Michael Bachmann Nielsen and Jørgen Arendt Jensen
Week 48, 2011
Performance of Synthetic Aperture Compounding for in-vivo imaging
Medical ultrasound imaging is used for many purposes - localizing and classifying cysts, lesions, and other processes. Almost any mass is first observed using B-mode imaging and later classified using color flow, strain, or biopsies. It is therefore important that the B-mode images have high contrast. Like all imaging modalities, ultrasound is subject to a number of inherent artifacts that compromise image quality. The most prominent artifact is the degradation by coherent wave interference, known as speckle. The speckle reduces image contrast and diminishes the possibilities for detection of lowcontrast regions. A successful approach to remedy the speckle artifacts is spatial compounding. This paper investigates an approach based on synthetic aperture imaging, where compounding can be obtained without any loss in temporal resolution.
A method for synthetic aperture compounding (SAC) is applied to data from water tank measurements, data from a tissue-mimicking phantom, and clinical data from the abdomen of a healthy 27 year old male. The water tank and tissue-mimicking phantom measurements show an improved lateral resolution and an improved NID for the suggested method for compounding using synthetic aperture data. An improved contrast resolution is also observed for the clinical data and it is definitely worth continuing studying this method for further evidence of its work
PSF images obtained using water tank phantom with wires
Performance of Synthetic Aperture Compounding for in-vivo imaging
by: Jens Munk Hansen and Jørgen Arendt Jensen. Paper presented at the IEEE International Ultrasonics Symposium, Orlando Florida, 2011
Week 47, 2011
Directional Synthetic Aperture Flow Imaging Using a Dual Stage Beamformer Approach
The paper presents a new method for directional synthetic aperture flow imaging using a dual stage beamformer approach. The velocity estimation is angle independent and the amount of calculations is reduced compared to full synthetic aperture, but still maintains all the advantages. In the paper, it is described how the new method was studied using Field II simulations and experimental flow rig measurements. The simulations and experiments substantiate that it can be used for directional flow estimation.
Color flow map made by the new method. 48 emissions are used for making one image frame
Directional Synthetic Aperture Flow Imaging Using a Dual Stage Beamformer Approach
by: Ye Li and Jørgen Arendt Jensen. Paper presented at the IEEE International Ultrasonics Symposium, Orlando Florida, 2011
Week 46, 2011
Compound imaging using Synthetic Aperture Sequential Beamformation
Synthetic Aperture Sequential Beamforming (SASB) is a technique with low complexity and the ability to yield a more uniform lateral resolution with range. However, the presence of speckle artifacts in ultrasound images degrades the contrast.
In this work, spatial compounding using SASB images was succesfully implemented for a linear multi element array transducer. Compounding of a number of images was based on SASB second stage image points positioned on a rectangular grid independent of individual beam directions.
The method resulted in reduced speckle appearence in B-mode images and a reduced level of noise especially evident in anechoic cysts. As a consequence, the contrast was improved making classification of cysts and other structures easier.
Illustration of the propagating waves for two multi element emmisions (blue and red respectively). The black dot indicates a specific image point rip which is part of a rectangular grid placed independent of the viewing angle. The second stage image point contain information from two first stage scan lines used to calculate the sample value h(rip). The same rectangular grid is used for all viewing angles.
Compound imaging using Synthetic Aperture Sequential Beamformation
by: Casper Bo Jensen, Jonas Jensen, Martin Christian Hemmsen, Jens Munk Hansen and Jørgen Arendt Jensen. Paper presented at the IEEE International Ultrasonics Symposium, Orlando Florida, 2011
Week 45, 2011
An Architecture and Implementation of Real-time Synthetic Aperture Compounding with SARUS
Synthetic aperture and compounding are imaging techniques for increasing the resolution and contrast of ultrasound images. Both techniques are computationally intensive, and combined they require approximately two orders of magnitude more lines to be beamformed per second compared to conventional B-mode imaging with similar frame rates. In this paper, an implementation of a system capable of synthetic aperture compound imaging in real-time producing more than 325 million complex beamformed samples per second is presented.
Top: Reference image beamformed using BFT3. Bottom: Image beamformed with SARUS.
An Architecture and Implementation of Real-time Synthetic Aperture Compounding with SARUS
by: Matthias Bo Stuart and Jørgen Arendt Jensen. Presented at the IEEE International Ultrasonics Symposium, Orlando Florida, 2011
Week 44, 2011
Angular spectrum approach for fast simulation of pulsed non-linear ultrasound fields
Simulation of non-linear wave equation is usually solved by numerically integrating the KZK or Burger's equation. This makes the simulation slow and inefficient with hundreds of steps needed, if the desired simulated points are far from the original acoustic source.
This paper describes how the pulsed non-linear ultrasound fields are successfully simulated by the ASA, whose accuracy is investigated and compared to Abersim. The ASA makes the non-linear ultrasound simulation flexible to any kind of transducer with arbitrary focus and excitation and calculation speed 70 times faster.
Emitted ultrasound fields calculated by ASA and Abersim - Fundamental and second harmonic fields at the focal depth (40 mm) are shown in the figure with 6 dB between two adjacent color lines
Angular spectrum approach for fast simulation of pulsed non-linear ultrasound fields
by Yigang Du, Henrik Jensen and Jørgen Arendt Jensen. Presented at the IEEE International Ultrasonics Symposium, Orlando Florida, 2011
Week 43, 2011
Recent advances in blood flow vector velocity imaging
A number of methods for ultrasound vector velocity imaging are presented in the paper. The transverse oscillation (TO) method can estimate the velocity transverse to the ultrasound beam by introducing a lateral oscillation in the received ultrasound field. The approach has been thoroughly investigated using both simulations, flow rig measurements, and in-vivo validation against MR scans. The TO method obtains a relative accuracy of 10% for a fully transverse flow in both simulations and flow rig experiments.
Click on picture to enlarge
Recent advances in blood flow vector velocity imaging
by Jørgen Arendt Jensen. Invited talk at IEEE International Ultrasonics Symposium 2011, Orlando, Florida.
Week 42, 2011
3D Vector Velocity Estimation using a 2D Phased Array
Conventional methods only estimate velocities in one dimension. As the velocities vary as a function of time and space, 3D techniques need to be employed to fully estimate and characterize the complicated flow patterns. This simulation study demonstrates, that the TO method can be used to estimate the 3D velocity vector within 5%. The requirements are a 2D phased array, five parallel beamformers, and 1024 active channels.
3D Vector Velocity Estimation using a 2D Phased Array
Michael Johannes Pihl and Jørgen Arendt Jensen, presented at the IEEE International Ultrasonics Symposium, Orlando, FL, USA, 2011
Week 40 + 41, 2011
Blood velocity estimation using ultrasound and spectral iterative adaptive approaches
The paper proposes two novel iterative data-adaptive spectral estimation techniques for blood velocity estimation using medical ultrasound scanners. The techniques are shown using both simplified and more realistic FieldII simulations as well as in vivo data to outperform current state-of-the-art techniques allowing for accurate estimation of the blood velocity spectrum.
SignalProcess.(2011)
doi:10.1016/j.sigpro.2010.12.014 p. 7
Blood velocity estimation using ultrasound and spectral iterative adaptive approaches
Erik Gudmundson, Andreas Jakobsson, Jørgen A. Jensen, Petre Stoica.
Week 39, 2011
Civilingeniør i Medicin og Teknologi
Medicin og Teknologi er en civilingeniøruddannelse i medicoteknik, der udbydes i et samarbejde mellem Det Sundhedsvidenskabelige Fakultet på Københavns Universitet og DTU. Artiklen giver et overblik over uddannelsens mål, struktur og indhold.
Civilingeniør i Medicin og Teknologi
Henneberg, Kaj-Åge; Wilhjelm, Jens. E.; Jensen, Jørgen Arendt; Stallknecht, Bente; Højgaard, Liselotte (2011): Medicinsk Teknologi & Informatik, 8(2), 8-11
Week 38, 2011
Image processing in medical ultrasound
The project is divided into three main topics - 1) Development and implementation of a versatile research data acquisition system. 2) Clinical evaluation of SASB using a convex array transducer, and 3) Simulation of acoustic fields for high quality ultrasound imaging.
Illustration of the GUI associated with the assessment of penetration depth. The horizontal red line is placed at the respective depth where the assessor evaluates the image quality no longer usable for reliable diagnostic use. The control panel for navigating the sequences are shown in the lower right corner. The B-mode image shown is generated using SASB.
Image processing in medical ultrasound
Martin Christian Hemmsen
The results were submitted as a PhD dissertation to be defended Friday, 4 November at 2 pm.
Download pdf and read the dissertation in full.
Week 36 + 37, 2011
Non-linear Ultrasound Imaging
A dual stage harmonic imaging is presented, and the measured results from the preliminary study show that the combination of harmonic imaging and SASB gives a great improvement on the lateral resolution. Accordingly, it seems that the axial resolution is only improved by harmonic imaging and hardly by SASB, compared with conventional imaging.
Point spread function of emitted field at the focal depth - The figure shows the emitted fields along the lateral direction at the focal depth 40 mm from the transducer surface calculated by the ASA based on Field II and by Abersim for the fundamental field on the top and for the second harmonic field on the bottom and 6 dB between two adjacent lines.
Non-linear Ultrasound Imaging
Yigang Du
The results were submitted as a PhD dissertation and defended on 13 September 2011 at DTU.
Download pdf and read the dissertation in full.
Week 35, 2011
Examples of Vector Velocity Imaging
A series of scans has been performed with UltraView - for the first time, it has possible to obtain a real-time angle independent estimate of the blood flow direction as a directly readable parameter.
Scan on the longitudinal axis of the common carotid artery illustrating simple blood flow (click on picture to enlarge)
Hansen, Peter M.; Pedersen, Mads M.; Hansen, Kristoffer L.; Nielsen, Michael B.; Jensen, Jørgen Arendt (2011): Examples of Vector Velocity Imaging. In: Dremstrup,K; Rees,S; Jensen,M. Ø (Eds.), IFMBE Proceedings (p. 77-80)
Presented at: 15. Nordic-Baltic Conference on Biomedical Engineering and Medical Physics; 15, Aalborg, Denmark Springer
Download pdf and read the article in full.
Week 34, 2011
Preliminary Experimental Verification of Synthetic Aperture Flow Imaging Using a Dual Stage Beamformer Approach
A dual stage beamformer method for synthetic aperture flow imaging has been developed to increase the frame rate and still maintain a beamforming quality sufficient for flow estimation that is possible to implement in a commercial scanner. With the new method high resolution images can be obtained continuously, which will highly increase the frame rate. The experimental results showed that increasing the number of imaging lines used for the estimation from 4 to 24 reduces the standard deviation from 21% to 7.6%.
Four image lines from the first stage. They only carry information within the transmit pattern defined by the opening angle. The high resolution points, the green dots, are obtained by adding all low resolution points overlapping at that position.
Li, Ye; Jensen, Jørgen Arendt (2011): Preliminary Experimental Verification of Synthetic Aperture Flow Imaging Using a Dual Stage Beamformer Approach. In: Dremstrup,Kim; Rees,Steve; Jensen,Morten Ølgaard (Eds.), IFMBE Proceedings (p. 53-56)
Presented at: 15. Nordic-Baltic Conference on Biomedical Engineering and Medical Physics; 15, Aalborg, Denmark Springer
Download pdf and read the article in full.
Week 33, 2011
Ultrasonography Fused with PET-CT Hybrid Imaging
This paper published in Current Medical Imaging Reviews describes how it is possible to fuse 3D UL and PET-CT, a potential important supplement to conventional imaging in the external radiation therapy in the treatment of anal cancer, where the precise delineation of a tumor is crucial to avoid damage from radiation therapy to the healthy tissue surrounding it. Three-modality imaging may also be used in certain other diagnostic or therapeutic fields.
An example of one image of the fused US-PET-CT data set. On screen the US and CT images are shown in black and white. The PET-image is in blue-yellow-red colors
Udesen, Jesper; Ewertsen, Caroline; Gran, Fredrik; Fogh Christensen, Anders; Kjaer-Kristoffersen, Flemming; Engelholm, Svend Aage; Jensen, Jørgen Arendt; Nielsen, Michael Bachmann (2011): Ultrasonography Fused with PET-CT Hybrid Imaging. Current Medical Imaging Reviews, 7(3), 248-251
Download pdf and read the article in full.
Week 32, 2011
Synthetic Aperture Focusing for a Single Element Transducer undergoing Helix Motion
American men have a risk of 16.7% for developing prostate cancer. Treatment depends on a pre-operation analysis of the prostate to decide on seed placements, using x-ray CT or trans-rectal ultrasound (TRUS). For a better placement of the seeds a real-time visualization of the prostate gland is desired. Using 3D TRUS to visualize the prostate gland during operation allows for an interactive guided placement of the seeds.
In this paper, the single-element TRUS probe, primarily designed to investigate the rectal wall, is investigated.
Andresen, Henrik; Nikolov, Svetoslav Ivanov; Jensen, Jørgen Arendt (2011): Synthetic Aperture Focusing for a Single Element Transducer undergoing Helix Motion. I E E E Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 58(5), 935-943
Download pdf and read the article in full.
Week 31, 2011
Finite Element Implementation of a Structurally-Motivated Constitutive Relation for the Human Abdominal Aortic Wall with and without Aneurysms
The structural integrity of the abdominal aorta is maintained by elastin, collagen, and vascular smooth muscle cells. Changes with age can lead to development of aneurysms. This paper presents initial work to capture these changes and provides more accurate insight into the stress conditions in aortic aneurysms.
Enevoldsen, Marie Sand; Henneberg, Kaj-Åge; Lönn, L; Jensen, Jørgen Arendt (2011): Finite Element Implementation of a Structurally-Motivated Constitutive Relation for the Human Abdominal Aortic Wall with and without Aneurysms. In: Dremstrup,Kim; Rees,Steve; Jensen,Morten Ølgaard (Eds.), IFMBE Proceedings (p. 13-16)
Presented at: 15. Nordic-Baltic Conference on Biomedical Engineering and Medical Physics; 15, Aalborg, Denmark Springer
Download pdf and read the article in full.
Week 30, 2011
Summer holiday
Week 29, 2011
Performance Evaluation of a Synthetic Aperture Real-Time Ultrasound System
The paper evaluates the signal-to-noise ratio, the time stability, and the phase difference of the sampling in the experimental ultrasound scanner SARUS capable of advanced real-time computations such as synthetic aperture imaging. The system is built using fieldprogrammable gate arrays (FPGAs) making it very flexible and allowing implementation of other real-time ultrasound processing methods in the future.
Stuart, Matthias Bo; Tomov, Borislav Gueorguiev; Jensen, Jørgen Arendt (2011): Performance Evaluation of a Synthetic Aperture Real-Time Ultrasound System. In: Dremstrup,Kim; Rees,Steve; Jensen,Morten Ølgaard (Eds.), IFMBE Proceedings (p. 160-163)
Presented at: Nordic Baltic Conference on Biomedical Engineering and Medical Physics; 15, Aalborg, Denmark Springer
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Week 28, 2011
Ultrasonic colour Doppler Imaging
The journal paper gives a comprehensive review of velocity estimation using ultrasound including the latest techniques for vector velocity imaging.
Longitudinal scan of the femoral vein with disturbed flow at the passage of a venous valve. A vortex is formed in the pocket behind the valve. The vector velocity scan has been obtained from a BK Medical ProFocus scanner.
(click picture to enlarge)
Evans, David H.; Jensen, Jørgen Arendt; Nielsen, Michael Bachmann (2011): Ultrasonic colour Doppler imaging. Interface Focus
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Week 27, 2011
Simulation of ultrasound backscatter images from fish
In-situ identification of fish is important to fisheries operations as well as scientific marine surveys, as unwanted by-catches can be avoided if the fisher knows the species prior to the catching.
The work described in the paper has generated realistic simulated ultrasound images of a fish from computed tomography images. The results will be used as library sets to improve the technique of the fish identification using acoustic.
a) Measured ultrasound image of a slice of a fish
b) Simulated ultrasound image of a slice of a fish
(click picture to enlarge)
Presented at: SPIE Medical Imaging SPIE - International Society for Optical Engineering
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Week 26, 2011
Preliminary comparison between real-time in vivo Spectral and Transverse Oscillation velocity estimates
It has been shown that the Transverse Oscillation method provides equally good estimations of blood velocities as the Spectral Doppler method, and with more correct calculations of flow angles, as correction is not neccesary.
Real-time example of simultaneous in vivo data acquisition with both spectral estimation, and Transverse Oscillation (click picture to enlarge)
Velocity profile using spectral estimation (top), and Transverse Oscillation (bottom) using simultaneously acquired data (click picture to enlarge)
Pedersen, Mads Møller; Pihl, Michael Johannes; Haugaard, Per; Hansen, Jens Munk; Hansen, Kristoffer Lindskov; Nielsen, Michael Bachmann; Jensen, Jørgen Arendt (2011): Preliminary comparison between real-time in-vivo spectral and transverse oscillation velocity estimates. In: D'hooge,Jan; Doyley,Marvin M. (Eds.), Proceedings of SPIE
Presented at: Medical Imaging 2011: Ultrasonic Imaging, Tomography, and Therapy, San Diego, California, USA SPIE - International Society for Optical Engineering
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Non-linear Imaging Using an Experimental Synthetic Aperture Real Time Ultrasound Scanner
The research scanner SARUS is capable of producing non-linear imaging. This provides us with a great potential to improve focus and contrast in ultrasound images.
Contour plot of point scatterer measured by the SARUS system. The top figures shows the non-linear field and the bottom the conventional, linear field. The top plot is narrower indicating a smaller point size (sharper image) and a better contrast.
Rasmussen, Joachim; Du, Yigang; Jensen, Jørgen Arendt (2011): Non-linear Imaging using an Experimental Synthetic Aperture Real Time Ultrasound Scanner. In: Dremstrup,K.; Rees,S; Jensen,M. Ø (Eds.), IFMBE Proceedings (p. 101-104)
Presented at: Nordic Baltic Conference on Biomedical Engineering and Medical Physics, Aalborg, Denmark Springer
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Week 24, 2011
New interpretation of arterial stiffening due to cigarette smoking using a structurally motivated constitutive model
Knowledge of histo-mechanical changes is sparse but new interpretation indicates that the stiffening process is isotropic
Tissue specimen experimental data (from rat pulmonary arteries) divided in two different age groups with smokers (open triangles) vs. controls (open circles) were used for parameter estimation and re-interpretation of the stress-stretch relationship. The solid line is the fit of experimental data using the structurally motivated constitutive relation
Enevoldsen, Marie Sand; Henneberg, Kaj-Åge; Jensen, Jørgen Arendt; Lönn, L; Humphrey, J.D. (2011): New interpretation of arterial stiffening due to cigarette smoking using a structurally motivated constitutive model. Journal of Biomechanics, 44(6), 1209-1211
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Week 23, 2011
Demonstration of a Vector Velocity Technique
A new ultrasound technique developed at CFU - and now implemented in a commercial BK scanner
The paper demonstrates examples of the use of this technique in the clinic:
Hansen, Peter Møller; Pedersen, Mads M.; Hansen, Kristoffer L.; Nielsen, Michael Bachmann; Jensen, Jørgen Arendt (2011): Demonstration of a Vector Velocity Technique. Ultraschall in der Medizin, 32(2), 213-215
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Scan on the longitudinal axis of the femoral vein with disturbed flow at the passage of a venous valve. A vortex is formed in the pocket behind the valve
Week 22, 2011
Comparison on simulated and measured non-linear ultrasound fields
Simulation programs for non-linear ultrasound are often slow and not competitive when doing measurements. An new simulation program, 140 times faster, has been developed.
The non-linear simulation program was presented at the SPIE conference for Medical Imaging, Ultrasonic Imaging, Tomography, and Therapy, 2011, Lake Buena Vista, Florida, USA:
Du, Yigang; Jensen, Henrik; Jensen, Jørgen Arendt (2011): Comparison of Simulated and Measured Non-linear Ultrasound Fields. In: D'hooge,Jan; Doyley,Marvin M. (Eds.), Proceedings of SPIE
Presented at: SPIE Medical Imaging: Ultrasonic Imaging, Tomography, and Therapy, Lake Buena Vista, Florida, United States SPIE - International Society for Optical Engineering
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Week 21, 2011
Toolbox for offline beamformation of ultrasound signals on a workstation
The toolbox supports parametric and dynamic apodization and a number of focusing strategies. It is capable of exploiting parallelization on a single computer, on a cluster, or both, 19 times faster
The improved toolbox, BFT3, was presented at the SPIE conference for Medical Imaging, Ultrasonic Imaging, Tomography, and Therapy, 2011, Lake Buena Vista, Florida, USA:
Hansen, Jens Munk; Hemmsen, Martin Christian; Jensen, Jørgen Arendt (2011): An object-oriented multi-threaded software beamformation toolbox. In: D'hooge,Jan; Doyley,Marvin M. (Eds.), Proceedings of SPIE Volume
Presented at: SPIE Medical Imaging: Ultrasonic Imaging, Tomography, and Therapy, Lake Buena Vista, Florida, United States SPIE - International Society for Optical Engineering, 79680Y
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