Ultrasound P1 PDF
Document Details
Uploaded by UnbiasedConsonance5950
Tags
Summary
This document provides a historical overview of ultrasound technology, covering key figures, discoveries, and milestones in its development. The document also details the fundamental principles of ultrasound imaging.
Full Transcript
ULTRASOUND P1 HISTORICAL PERSPECTIVE IN Tom Brown ULTRASOUND -produced a mechanical contact compound 1970 scanner in late 1950's - Ultrasound achieve wide cli...
ULTRASOUND P1 HISTORICAL PERSPECTIVE IN Tom Brown ULTRASOUND -produced a mechanical contact compound 1970 scanner in late 1950's - Ultrasound achieve wide clinical use. Holm 1880 - Also developed a contact compound scanner - Piezoelectric effect was noted by Pierre and which was in regular clinical use by the mid-1960s. Jacques Curie, in which the generation and Wells detection of ultrasound signal depends. - produced probably the first of hinged arm 1912 scanner which rapidly became the main - The first major attempt at a practical configuration for manually operated compound application was made in the unsuccessful search of static scanners until their demise at the hand of the sunken Titanic in the North Atlantic. automated real-time system in early 1980s. 1916 Kossoff - The physical principles on which our modern - developed a complex water bath scanner diagnostic techniques rely therefore probably owe which produced excellent high resolution images their origin to Chilowsky and Laugavin. Their work with good dynamic range display on a non-storage was on the basis of SONAR (Sound Navigation and oscilloscope in 1970s Ranging), the first important successful application - It was probably his work which stimulated the of ultrasound. equipment manufacturers to reintroduce grey scale 1927 and 1929 image display and this was greatly facilitated by the -Worod, Loomis and Johnson published their development of television scan converter tube. result on the bio effect of this newly discovered Late 1960s and early 1970s form of energy. Historical Perspective in - The origin of the real-time ultrasound Ultrasound imaging. Late 30's and early 40's Bom - Sakdov and Firestone took out patients on -pioneered the development of linear array ultrasound device used for detecting metal flows transducers as his first system having 20 elements 1949 giving 20 lines of information in the image. - Ludwig and Struthess used pulse Sonar echo-ultrasound as medical imaging technique to - Simultaneously developing the phased array detect gallstones and foreign bodies in soft tissues. transducer. 1950 Mid 1970s - Howry and Bliss produced first cross-sectional - Annular array transducers were introduced ultrasound image. Historical Perspective in which permitted bea, focusing at any depth. Ultrasound 1980s 1957 - intracavitary mechanical rotating scanner were - Howry and Homes assembled the first produced. compound scanner consisting of water-filled tank in - Doppler ultrasound was being developed. which patient was immersed surrounded by trach in Fundamental work in this field was done by which transducer was moved in a series of Kallnus in 1954. compound 1964 motions - Callagan described the detection of fetal heart Wild and Reid movement by doppler ultrasound and principle was - published their work on direct contact scanner rapidly developed for detection of blood flow showing images of the muscles of forearm and later within accessible superficial vessels throughout the of breast tissue body. Baun Early 1970s - developed an ophthalmic scanner. - Pulsed doppler system was employed which Luksell could permit measurement of depth within the - applied the principle of industrial flaw detector patient from which echoes were arising. Theses to human skull and detected cerebral midline echo. system suffered from the problem of slow image production. ULTRASOUND P1 Mid 1970s to early 1980s Infrasound - A duplex system was introduced in which a -below 16Hz high resolution conventional real-time imaging Audible Sound scanner was linked to a pulsed doppler device. This - lies in the range of 20Hz to 20,000Hz system were popular for evaluation of carotid Diagnostic Ultrasound circulations. - concerned safely with frequencies in the range Late 1980s of 2MHz to 10Mhz. - The major limitation of the duplex system in Catheter based Endoluminal Source its inability of real-time imaging system to detect - Frequencies that extends to 50MHz all plaque and thrombus reliably, especially fresh Propagation Speed thrombus within a vessel was overcome by Doppler - is the distance travelled per unit time. color flow mapping. Sound Speed SUMMARY - is very much dependent on medium of - The use of Ultrasound in medicine began propagation. shortly after the 2nd World War Frequency - Dr. Karl Theodore Dussik's work on - Is independent of the medium and does not transmission ultrasound investigation of the brain in change significantly 1942 (Austria) was the first published work on -the attenuation of ultrasound beam energy and medical ultrasound. quality of image are strong function of frequency. - Ultrasound was first developed for clinical Amplitude (Depth) purposes in 1956 in Glasgow. -the maximum displacement that occurs in an - Obstetrician lan Donald and engineer Tom acoustic variable Relevant Terminologies Brown developed the first prototype systems based Piezoelectric effect on an instrument used to detect industrial flaws in - Piezein -"press or pressure" ships. - Ability of a material to generate an electrical - They perfected its clinical use, and by the end charge in response to applied pressure of the 1950s, ultrasound was routinely used in Attenuation Glasgow hospitals. - The reduction in amplitude of the ultrasound - Commercial systems became available in the beam as a function of distance through the imaging mid 1960s. medium. Acoustic Impedance (Z) RELEVANT TERMINOLOGIES - is the opposition of a medium to a longitudinal Ultrasound wave motion - can be defined as the sound waves beyond the ordinary limits of hearing. - is a form of mechanical energy which can be BASIC PHYSICS TERMS characterized as a wave phenomenon. Ultrasound Wavelength or length of wave (入) - Utilizes sound waves of very high frequency - Is the distance between two-band of (2MHz or greater). compression or rarefaction and is represented by 入. - It is propagated via waves of compression and Period (T) rarefaction, and requires a medium (tissue) for - The time to complete a single cycle travel. Rarefaction - The higher the frequency, the less depth - Molecules of air are alternatively compressed penetration, however the resolution is improved. and decompressed by mechanical action. Resolution Frequency (f) - Is the parameter of an ultrasound imaging - The number of oscillation (cycles) per second. system that characterizes its ability to detect Hertz(Hz) closely spaced interfaces and displays the echoes - is used to describe the number of oscillation from those interfaces as distinct and separate per second in modern physics. objects. Velocity - The better the resolution, the greater the clarity - Frequency × Wave length (入) of an ultrasound image. ULTRASOUND P1 Axial Resolution water level in the transducer assembly before - Is the minimum required reflector separation scanning and if you see air bubbles, make sure along the direction of propagation required to you fill it with the deionized water. produce separate reflections. - Good axial resolution is achieved with short spatial pulse lengths. Short spatial pulse lengths ADDITIONAL ULTRASOUND are a result of higher frequency and higher TERMINOLOGIES AND TERMS damped transducers. B-Mode (Brightness modulation) - Therefore the higher the frequency the better - A two-dimensional display of ultrasound. The the resolution. A mode spikes are electronically converted into Lateral Resolution dots and displayed at the correct depth from the - Is the minimum reflector separation transducer perpendicular to the direction of propagation Complex required to produce separate reflections. - Refers to a mass that has both fluid-filed and -Good lateral resolution is achieved with solid areas within it narrow acoustic beams. A narrow acoustic beam is Cystic the result of a long near zone and a small angle of -This term is used to describe any fluid-filled divergence in the far zone. structure, for example, the urinary bladder Transducers Enhancement (acoustic) - Convert one form of energy to another. - Sound is not weakened (attenuated) as it - Transducers operate on piezoelectricity passes through a fluid-filled structure and therefore meaning that some Materials (ceramics, quartz) the structure behind appears to have more echoes produce a voltage when deformed by an applied than the same tissue beside it pressure, and reversely results in a production of Frequency pressure when these materials are deformed by - The number of complete cycles per second an applied voltage. (Hertz) Pulse Transducer Gain - Consists of one transducer element which - Refers to the amount of amplification of the functions as both the source and receiving returning echoes transducers. Gel Couplant Attenuation - A trans-sonic material which eliminates the air - A decrease in amplitude and intensity, as interface between the transducer and the sound travels through a medium. animal's skin - Attenuation occurs with absorption Interface (conversion of sound to heat), reflection (portion of -Strong echoes that delineate the boundary of sound returned from the boundary of a medium, and organs, caused by the difference between the scattering (diffusion or redirection of sound in acoustic impedance of the two adjacent several directions when encountering a particle structures; an interface that is usually more suspension or a rough surface). pronounced when the transducer is - These different forms of attenuation are perpendicular to it responsible for artifacts that may be in your M-Mode image. Some of these artifacts are useful and - is the motion mode displaying moving some are not. Some artifacts are produced by structures along a single line in the ultrasound improper transducer location or machine beam settings. Noise Mechanical Probes - An artifact that is usually due to the gain - Allows the sweeping of the ultrasound beam control being too high through the tissues rapidly and repeatedly. This Reverberation is accomplished by oscillating a transducer. -An artifact that results from a strong echo - The oscillating component is immersed in a returning from a large acoustic interface to the coupling liquid within the transducer assembly. transducer. This echo returns to the tissues In our case the coupling fluid is deionized water. again, causing additional echoes parallel and It is important that the fluid is bubble free, so equidistant to the first echo that your image is not compromised. Check the ULTRASOUND P1 Shadowing Propagation of Sound - Failure of the sound beam to pass through an - Sound wave are mechanical pressure waves object, e.g. a bone does not allow any sound to (longitudinal) which propagate through a medium pass through it and there is only shadowing seen by compression of the particles behind it -As a sound pressure wave propagates throught Anechoic he medium,particles in regions of high pressure will - A structure that does not produce any internal be pushed together (compression) and particles in echoes regions of low pressure will be pulled apart A-Mode (Amplitude modulation) (rarefaction). - A single dimension display consisting of a Power and Intensity horizontal baseline. This baseline represents -A sound wave transports Energy through a time and or distance with upward(vertical) medium from a source. deflections (spikes depicting the acoustic - Energy is measured in joules (J) interfaces) - The Power (P), produce by a souce of sound is Attenuation the rate at which it produces energy. - The ultrasound beam undergoes a progressive - Power is measured in watts (W) where 1 W= weakening as it penetrates the body due to 1J/s absorption, scattering and beam spread. The - The Intensity (I), associated with a sound amount of weakening is dependent on wave is the power per unit area. frequency. tissue density, and the number and -Intensity is measure in W/m2. types of interfaces - The power and intensity associated with a Homogenous wave increase with the pressure amplitude (p). -Of uniform appearance and texture Wave'ength, Frequency and Speed Hypo-echoic - Waves are characterized by their wavelength, -A relative term used to describe an area that frequency and speed has decreased brightness of its echoes relative to an - The wavelength (y) is the distance between adjacent structure consecutive peaks or other similar points on the wave. Hyper-echoic - The frequency (f) is the number of oscillation - Also a relative term used to describe a per second structure which has increased brightness of its - Frequency is measured in Hertz (Hz) where 1 echoes relative to an adjacent structure Hz is one oscillation per second. Time-Gain Compensation - The Speed of sound (c) is the distance -Compensation for attenuation is accomplished travelled by the wave per unit time and is equal to by amplifying echoes in the near field slightly the wavelength multiplied by the frequency. and progressively increasing amplification as - The speed of sound is dependent on the echoes return from greater depths medium through which it travels and varies greatly Transducer in different materials - A device which houses the element for - The speed of the wave is determined by the transmitting and receiving ultrasound waves. bulk modulus (B) (measure the stiffness) and the Also referred to as a probe or Scanhead density (p) (mass per unit volume) of the medium Velocity (of sound) - Highly compressible media (low B), such as - Is the speed at which a sound wave is traveling. air, has a low speed of sound - 330m/s In soft tissue at 37 degrees C. sound travels at - Less compressible media (high B), such as a 1540 m/second bonr, has higher speed of sound -4080 m/s Material Density(Kg/m2) C (m/s) Air 1.2 330 Fat 924 1,450 SOUND WAVES AND THEIR CHARACTERISTICS Water 1k 1,480 Wave Motion Kidney 1,041 1,556 - Waves transfer energy from one location to another “AverageTissue” 1,050 1,540 - Waves can be broadly described as either "Transverse" Muscle 1,068 1,600 or "Longitudinal" Bone 1,912 4,080 ULTRASOUND P1 - The frequency of a sound wave is unaffected BASIC PRINCIPLES OF IMAGE by changes in the speed of the wave as it propagates FORMATION through different media - FOCUS, which concentrates the soundbeam - Therefore, the wavelength changes as the into a smaller beam area than would exist otherwise wave travels through different media in the transducers. - Wavelength increases with an increase in - This area of focus is where you will obtain wave speed. - Higher frequency sound waves have your best images. You will find thefocus on the a shorter wavelength monitor (arrow),on the vertical millimeter scale. MACHINE COMPONENTS Transducers PULSE ECHO PRINCIPAL Beam Former - A short ultrasound pulse is delivered to the Receiver tissues, and where there are changes in the acoustic Memory properties of the tissue, a fraction of the pulse is Display reflected (an echo) and returns to the souce (pulse-echo principal) TRANSDUCER TYPES - Collection of the echoes and analysis of their Mechanical amplitudes provides information about tissues along - Oscillating the path of travel - Rotating - Distance (D)= speed (c) x time (t) Electronic - Linear Arrays TOMOGRAPHIC IMAGING - Curved Arrays - Repeating this process many times with - Phased Arrays incremental changes in pulse direction allow a volume to be samples and a tomographic image to Electronic Arrays be formed - Groups of piezoeletric materials working singly or in groups B-MODE IMAGE Sector Array - A B-mode image is a cross-sectional image - crystal are placed parallel or in concentric representi tissues and organ bounderies within the rings body. - transducer face is curved - Each echo is displayed at a point in the image - produces sector or pie-shaped image which corresponds to the relative position of its Linear Array origin within the body. - crystals are placed parallel - Bmode = Brightness mode - transducer face is flat - The mode that is used for the display of - produces rectangular image echoes that.return to the transducer. - The returning echoes are displayed on a DISPLAY FIELD OF VIEW television monitor as shades of gray. Field of View - Typically the brighter gray shades represent - the display of the echo amplitude echoes with greater intensity levels. - shape dependent on transducer type and - This mode allows you to scan. function - Minimum time for one line = (2 x depth / FIELD OF VIEW SHAPES speed of sound = 2D/c seconds Sector FOV - Each frame of image contains N lines -produced by - Time for one frame = 2ND / c seconds oscillating - Additinal interpolated lines are inserted rotating between image lines to boost image quality to the curved arrays human eye phased arrays - Time is very important -typically used in abdominal application Linear FOV - produced by linear arrays - typically used in superficial application ULTRASOUND P1 TIME GAIN COMPENSATION (TGC) ALIASING - The deeper the souce of echo - Is the production of false doppler shift and - smaller signal intensity Due signal attenuation blood velocity information when the Doppler shift in tissue and reduction of the initial US beam exceeds a threshold. It appears as if the spectral intensity by reflections display is cut off and wraps around and reappears in - Operator can use to artificially 'boost' the the opposite region of the display. signals from deeper tissues to compensate for this (like a graphic equaliser) - Equalizes differences in received reflection amplitudes because of the reflector depth. SPECTRAL BROADENING - TGC allow you to adjust the amplitude to - The widening of the doppler shift spectrum. compensate for the path length differences. Meaning the increase of the range of doppler shift - The longer the path length the higher the frequencies present,owing to a broader range of amplitude. flow speeds encountered by the sound beam. - The TGC is located on the right upper hand corner of the monitor, and is displayed graphically. COLOR DOPPLER M-MODE IMAGE - In color doppler echoes are displayed with - Can be used to observe the motion of tissues colors corresponding to the direction of flow that (e.g. Echocardiography) their positive or negative doppler shifts represent - Image the same position (one image line) (toward or away from the transducer). repeatly. - The brightness of the color represents the - One direction of display is used to represent intensity of the echoes, and sometimes other colors time rather than space are added to indicate the extent of spectral - Is a graphic B-mode pattern that is a single broadening line time display that represents the motion of structures along the ultrasound beam, 1000fps. - This mode allows you to trace motion i.e. heart wall motion, vessel wall motion. POWER DOPPLER - This allows detection of a larger range of doppler shifts and therefore better visualization of PULSE WAVE MODE the smaller vessels, but at the expense of directional - Frequency change of reflected sound waves as and velocity information a result of reflection motion relative to the transducer used to detect the velocity and direction of blood flow. This reflection shift can be displayed grap DOPPLER SHIFT - Is dependent on the insonating frequency, the velocity moving blood and the angle between the sound beam and direction of the moving blood. - The angle of the sound beam should be less than 60 degrees at all times. SAMPLE VOLUME - Is the gate length which chooses the doppler shifts that will be used to produce audible sounds or spectral display.The larger the sample volume the more Doppler frequencies detected.