Saturday, March 30, 2019
A healthy heart
A healthy heartabstractA healthy heart is the tombstone to good life .The heart is a vital organ of the human being body which ensures the effective pumping of business line throughout the circulatory system. Due to our inactive lives and food habits, the heart is prone to malfunctioning, and heart attack (i.e. coronary arterial filiation watercraft disease), is one of the primary ca engross of death 1. Heart attack is ca utilize by a blockage of the coronary arteries, typically at a position of narrowing (stenosis) caused by coronary arterial blood vessel disease. It is knotty to accu appreciately determine the degree of atherosclerosis in arteries, particularly in the early stages of disease. superstar regularity that has been introduced is the intravascular ultrasonic catheter (IVUS), which sends a cadence of sound from a receiving system and uses the returned call up to fence out the properties of the arterial tissues. Doppler echography is a similar a diagnostic, noninvasive proficiency which croup effectively evaluate the blood f first-class honours degree stop number in the coronary arteries by personnel casualty the high absolute frequency ultrasonography dithers into the blood exploitation a exclusive pass murderer. Our group has found that an improvement in speed estimate cigaret be obtained if the returned Doppler ultrasonography retort is dispassionate by triplex liquidators and the in impressation from those pass catchers is combined. The research proposed here go out use simulation manners to determine the extent to which this same concept can be applied to multiple IVUS receivers.1. introductionDoppler ultrasound provides a valuate of the velocity distribution of blood throughout the volume of the artery. Because the call for is a principle of superposition of echoes from multiple scatterers, the red blood cells, distributed in space, the steer at the receiver is subject to constructive and baneful int erference. This phenomenon is called lucid dispersal and is the primary reason that Doppler ultrasound mansions are inherently noisy. The same phenomenon applies to ultrasonic imaging (B- agency imaging), in which the Doppler shift is ignored and only the magnitude of the returned taper is used to form an visit of the tissue. However, in B-mode ultrasound, the scatterers are variations in the acoustic impedance of the tissue. anatomy 1 shows a typical IVUS two-baser 6. Whereas it is possible to differentiate amongst the lumen, media and adventitia, the exact boundaries are difficult to determine as a upshot of the coherent distribution effects.2. background2.1. Principles of Ultrasonic B-Mode ImagingB mode imaging is typically used for ultrasound imaging as it facilitates the demonstrate of the echoes at various spark or gray levels corresponding to their amplitude.ee handbook nigh B-mode systems in use todaycreate an image in 0.1 s or less, so that the image is exhib ited in real- duration for viewing of woful structures,such as structures in the heart or the fetus moving within the womb. This is not possible with the typicalmagnetic resonance or computed tomography system.Most of these systems use the Doppler principle, but some use sentence do master(prenominal) espial. In Doppler sleuthing,if the ultrasound is reflected from a target moving at some speed vt toward (away from) the source at an angleq with respect to the aerate axis, the frequency of the transmitted signal f is shifted up (down) by an totalityfD, the Doppler shift, according to the following relation(116.4)In principle a mensuration of fD, when f, c, and q are dwelln, result yield the speed of the target vt. However, itis often difficult to determine q because the angle the transducer axis makes with a blood vessel, for example,is often unknown. horizontal when that angle is known, the flow is not necessarily along the direction of the vesselat every post and for al l timesTwo-dimensional B-mode display Echoes from a transducer, or beam, scanned in one plane displayed asbrightness (or gray scale) versus location for the returned echo to produce a two-dimensional image. convert ultrasound Simultaneous display of speed versus time for a chosen vicinity and the two-dimensionalB-mode image. B-mode display Returned ultrasound echoes displayed as brightness or gray scale levels corresponding tothe amplitude versus depth into the body physique 6 in devts in cardio vascular ultrasound.pdfdescribes excitant signal usedB -mode (Brightness mode) ultrasound is the most commonly applied ultrasound technique for intracoronary artery visualization. B-mode images are made up of one dimensional signals from transducer vitreous silicas aline in an arrays,which can also be displayed in two dimensional in the form of a sectorAugust et al.In This mode of imaging, depth and the brightness are the measure of radial axis and echo intensity.2.1.1. break up of so undecho description fundamental sources of misplays2.1.2. Relationship between sound intensity and sparge coefficientThe size of the sprinkling shadow is called the effective cross-section (s cm2) and can be smaller or larger than the geometricalal size of the scattering subatomic particle (A cm2), related by the proportionality constant called the scattering efficiency Qs dimensionless The scattering coefficient s cm-1 describes a medium containing numerous scattering particles at a concentration described as a volume density s cm3. The scattering coefficient is essentially the cross-sectional area per unit volume of medium. Scattering coefficient The factor that expresses the attenuation caused by scattering, e.g., of radiant or acoustic energy, during its public life through a medium. look The scattering coefficient is usually expressed in units of common distance. Attenuation The decrease in intensity of a signal, beam, or wave as a result of absorption of energy and of scattering out of the path to the detector, but not including the reduction due(p) to geometric spreading. After JP1 Note 1 Attenuation is usually expressed in dB. Note 2 Attenuation is often used as a misnomer for attenuation coefficient, which is expressed in dB per kilometer. Note 3 A peculiarity must be made as to whether the attenuation is that of signal forefingerMeasurement of the intensity distribution of laser radiation usingby VV Morozov 1979 Related articles All 4 versionsof interaction between the light and sound, i.e., in which the scattering coefficient would depend linearly on the sound intensity. 2.1.3. Constructive and baneful interferenceSound travels in the form of waves.These waves are associated with frequency and amplitude.From introductory laws of physics it is known that intensity is directly proportional to amplitude of the wave which is the discriminating factor between different modes of ultrasound imaging.When these sound waves interact with each other interference occurs.The type of interference is determined by measuring the amplitude of the resultant wave formed by interaction of 2 sound waves.If the amplitude of 2 waves is either positive or negative then(prenominal) the resultant wave has larger amplitude.This phenomenon is known as constructive interference(or in material body interference).If the interacting waves take opposite amplitude then the resultant wave has a lower amplitude.This phenomenon is known as destructive interference(or out of figure interference). The interference type depends on the difference in distances that each wave has to take.In this context,if the ultrasonic signals are emitted from a single transmitter and tranced from multiple receivers separated by a distance of fractional the wavelength, then we can observe constructive interference of returned echo amplitudes of the scaterrers rank d in region of interest at one receiver and destructive interference occurring at the second rec eiver located one-one-half the wavelength apart.cite reference wu thesis book.2.1.4. Signal processing for B-Mode images (e.g. envelope detection)Intracoronary ultrasonic is through on envelope detection of the sum of (returned) echo signals from each receiver .there are many/three ways of envelope detection. One simpler manner of doing it is to perform a full wave rectification on the returned echo followed by a low pass filtering to remove the side lobes of the signal. rectify/ extract the signal and process it by passing it through a low pass filter to remove the side lobes of the returned echo.though this mode of envelope detection appears to be simpler, the operating nitty-gritty frequency for each of the returned signal is to be known and possibly tracked from time to time for changes. The second/ some other yet complex method of envelope detection is using Hilbert transmute to get /generate/create a rational /methodical theatrical of the returned signal from each scattere r at each receiver. The advantage of using this method is that it is independent of the dampening effect present in the returned signal. (i.e. the changes in center frequency of the echo with time).The magnitude obtained from the complex signal is used as the final signal for ultrasonic imaging/next stage of converting into polar plots and plotting it using weighted average method . (refrsprab12 rascal 11 and B-mode handbook).quadrature detection can also be used for extracting the envelope of the signal.refrce(high re answer ultrasound)2.2. modern implementations of intracoronary imagingHeart disease can be diagnosed with the aid of Doppler and B-mode ultrasound, where the Doppler method provides a measure of flow rate and B-mode ultrasound provides an image. Generally these techniques, as typically used, do not have the spatial resolution to demonstrate flow in the coronary arteries. Coronary artery geometry is diagnosed by injecting a radio-opaque dye into the artery with a c atheter and taking x-ray images. However, this method does not specifically provide the locations of atherosclerotic lesions. It provides the internal geometry of the arterial lumen. Intracoronary Doppler ultrasound is a method in which a Doppler-tipped catheter is inserted into the coronary artery to measure blood velocity. IVUS uses a more than complicated catheter that has an array of ultrasound crystals set up in a ring at the tip of the catheter, and each crystal transmits an ultrasound pulsate radially and then receives the returned echo. With multiple crystals, a 2-dimensional image of the cross-section of the arterial lumen can be reconstructed. This technique is soon capable of providing real time cross sectional images in vivo 3.The main objective lens of Doppler ultrasound is to extract the flow velocity measurements and interpret them in physiologically significant variables through assumptions and velocity calculations 2. The most fundamental measuring rod we cons ider is the flow rate as it best describes the extent of perfusion of blood in the region of interest 2 (i.e. a section of the coronary artery). The objective of IVUS is to obtain a mapping of the make-up of the artery as an image. Although IVUS uses some(prenominal) transmitter-receivers, only a single receiver is being used to capture the reflected ultrasound wave and to view the circumferential view of the artery.The problem pertain by using a single receiver is that we miss many precise details about the physiological status of the artery due to its limited view and the obtained images are noisy because of coherent scattering. The possible solution can be to use multiple receivers to look at the region of interest from different angles to get a detailed view. The doctor can get a clear picture of the artery in hurt of velocity, flow rate, the size of plaque present inside artery and can treat the patient in a better way.2.2.5. Geometry of the transducers.We assume transducer as a point size spherical shaped piezoelectric crystal. document B-mode handbook.pdfsprab12.pdf page 72.2.6. Transducer frequency answer characteristics.The phrase frequency response characteristic usually implies a complete description of a systems curving steady-state behavior as a function of frequency.2.2.7. Specifics of the transmitted signalfrom program2.2.8. Signal conditioning and signal processing2.3. Limitations of intracoronary imaging (particularly coherent scattering/scattering from multiple scatterers)One of the main problems encountered with Doppler and B-Mode ultrasound velocity estimation is coherent scattering of noise. Coherent scattering error is caused by the changes in phase of the reflected echo as the red blood cells enter and fall in the sample volume. This phase depends on the distance of the transmitter to the scatterer and then to the receiver 5. The main research objective is to simulate this process of multiple receiver Doppler ultrasound using Matl ab simulation software and to see how well it improves the soul of image quality and clarity. Even the state of art of image is to be observed using the simulations.paper basic model of ivus.pdf page 8Intravascular ultrasonic image quality remains poor due to touch noise, imaging artifacts and shadowing of parts of vessel wall by calcifications. (Refce intravascular ultrasound image segmentation.)2.4. Previous work done on multiple receivers independency of coherent scattering noise in Doppler signals when receivers are sufficiently uttermost apart.Velocity Measurements made/obtained everyplace the region of interest (ROI) in an intracoronary artery have inherited velocity estimation errors due to coherent scattering. One of the methods to reduce these estimated errors is the use of multiple receivers .The echo received from each of the receivers will have some complementary information which not only improves velocity estimation, also contributes in enhancing the image clarit y in a B-mode ultrasound image processing. Jones, Krishnamurthy 2002 Improvement in velocity estimation is observed if returned Doppler ultrasound echo is collected and combined from all the multiple receivers. Most pregnantly the returned echo signal obtained at each receiver is independent of coherent scattering noise in Doppler signals when receivers are sufficiently far apart. In the case of an intracoronary artery, the RBCs are the major kind of multiple scatterers distributed in artery space. Since the returned echo signal detected/obtained at each of the receiver is a summation of all the echo amplitude signals from multiple scatterers in the region of interest, they are subjected to constructive and destructive interference This way multiple receivers in B-mode can improve the image quality of B -mode intravascular ultrasound (IVUS) images.initially a 2 dimensional geometry for the artery would be simulated. The transmitted signal would be generated using by a piezoelectri c crystal in an ultrasound in real time applications. But in this proposed research, using Matlab, we first try generating a discrete signal using the pulse generator. Based on the defined parameters such as the frequency, pulse width, amplitude, pulse repetition time, artery geometryr (?), angle of transmission of the transmitted and received signal, the image would be extracted. Primarily, the signal from a single scatterer is sculpted. In the advanced stages, multiple scatterer signals would be modeled. The following questions would be answered while doing the actual simulation. individually scatterer is modeled as a point source that reflects the transmitted signal with a set reflectivity. The scatterer does not alter the signals phase, but alters the amount of power that is returned to the receiver. Each receiver therefore is subjected to a signal that is the sum of returns from all of the scatterers, where it is important to keep track of the phases of the signals from each s catterer so that coherent scattering is adequately accounted for.The signal at each receiver is rectified and then averaged in time with a moving window to produce a signal that represents scattered power as a function of time. The range, corresponding to the location in the image, is proportional to the delay time of the returned signal.Each receiver will provide an image, and a composite image will be produced as the average over all of the receivers.3.4.1. Transmitter/Receiver characteristics (transmitted frequency, beam width)3.4.2. belt along of sound3.4.3. Scattering coefficients for (1) Background and (2) PlaquesThe fraction of the incident energy reflected or scattered is very small for soft tissues like elastin collagen etc. ee handbook The first derivative Backscattering coefficient/scattering coefficient is the aspect that expresses the attenuation caused by scattering, of acoustic energy, while passing through a medium. The scattering coefficient (s) is usually express ed in units of reciprocal distance. There certainly lies a difference between the normal aortal intima and various kinds of atherosclerotic plaques. More than 90% of normal vessels usually have scattering coefficients in the range of 15 mm-1 to 36 mm-1 ,where as atherosclerotic plaques like the lipid rich blocks, fibrocalcific plaques have scattering coefficients lesser than 20 mm-1 Levitz, Andersen et al .The fibrous plaques which constituted elasin ,lipids and collagen demonstrated a comparatively large variations in terms of scattering coefficient. Out of the three kinds of atherosclerotic plaques, fibrocalcific samples do not show up as frosty regions in any kind of image and hence can be assumed as in homogeneities within the tissue wall having passing scattering coefficient.3.4.4. Random numbers (particle location and scattering coefficients)3.5. Signal psychoanalysis (envelope detection)http//www.mathworks.com/products/demos/shipping/dspblks/dspenvdet.htmlHilbert Transfor m can be used to generate a time domain envelope. The point is to create a rectified signal that is more suitable for calculating a smooth envelope. In the frequency domain, magnitude data is already all positive, so I dont know why youd use Hilbert Transform. To get a spectrum envelope, just average several(prenominal) spectrum frames together. The headstone then is to choose correct frame size precedent to FFT, which should be base on the nature of your data and the sampling rate you are using. Averaging will help your SNR and maybe you can differentiate key frequencies between good and damaged bearings. x = Hilbert (xr) returns a complex coiled chronological succession, sometimes called the analytic signal, from a real data sequence. The analytic signal x = xr + i*xi has a real part, xr, which is the original data, and an speculative part, xi, which contains the Hilbert transform. The imaginary part is a version of the original real sequence with a 90 phase shift. Sines are therefore transformed to cosines and sin versa. The Hilbert transformed series has the same amplitude and frequency content as the original real data and includes phase information that depends on the phase of the original data. If xr is a matrix, x = Hilbert (xr) operates column wise on the matrix, purpose the Hilbert transform of each column. x = Hilbert (xr, n) uses an n point FFT to compute the Hilbert transform. The input data xr is zero-padded or truncated to length n, as appropriate. The Hilbert transform is useable in calculating instantaneous attributes of a time series, especially the amplitude and frequency. The instantaneous amplitude is the amplitude of the complex Hilbert transform the instantaneous frequency is the time rate of change of the instantaneous phase angle. For a light sinusoid, the instantaneous amplitude and frequency are constant. The instantaneous phase, however, is a aphorism tooth, reflecting the way in which the local phase angle varies linearly over a single cycle. For mixtures of sinusoids, the attributes are short term, or local, averages spanning no more than two or three points. Reference 1 describes the Kolmogorov method for minimum phase reconstruction, which involves taking the Hilbert transform of the logarithm of the spectral density of a time series. The toolbox function rceps performs this reconstruction. For a discrete-time analytic signal x, the last half of fft(x) is zero, and the first (DC) and center (Nyquist) elements of fft(x) are purely real. http//dip.sun.ac.za/weideman/research/mfiles/hilb1.mfunction h = hilb1(F, N, b, y)% The function h = hilb1(F, N, b, y) computes the Hilbert transform% of a function F(x) defined on the real line, at specified% values of y (y could be a scalar, vector, or matrix.)8. bibliographyhttp//www.johnshopkinshealthalerts.com/white_papers/heart_health_ch_wp/digital08_landing.html, last accessed on 02/26/2008, 0830 pm.Jones SA, Fundamental Sources of error and spectral broaden ing in Doppler ultrasound signals, Crc critical reviews in biomedical Engineering, page(s)399-483, 1993. Van der Steen AFW, Cespedes EI, de Korte C.L, Carlier S.G , Li W, Mastik F, Lancke C.T, Borsboom J, Lupotti F, Krams R, Sermys P.W, Bom N,Novel developments in intravascular imaging, Ultrasonics Symposium Proceedings, IEEE, Volume 2, page(s)1733 1742, 1998.Kumar P and Shoukri MM, Copula based prediction models an application to an aortic regurgitation study, BMC Medical Research Methodology, page 721, 2007.Jones SA and Krishnamurthy K,Reduction of coherent scattering noise with multiple receiver doppler, Ultrasound in Med. Biol., Volume 28, page(s) 647-653, 2002.Zhu H, Oakeson K D, and Friedman M H, Retrieval of Cardiac manakin from IVUS IVUS Sequences, Medical Imaging 2003 Ultrasonic Imaging and Signal Processing, Volume 5035, 2003 page(s) 1605-7422.