ULTRASOUND REVIEWER.pdf

UNIT 1: HISTORY AND THEORY LATE 1930'S PROFESSOR IAN DONALD DR. KARL DUSSIK an Austrian psychiatrist and Credited with discovering the first diagnosti...

UNIT 1: HISTORY AND THEORY LATE 1930'S PROFESSOR IAN DONALD DR. KARL DUSSIK an Austrian psychiatrist and Credited with discovering the first diagnostic 1794 neurologist at University of Vienna was first to applications of ultrasound. Physiologist LAZZARO SPALLANZANI was use ultrasound for medical diagnoses. Published “Investigation of Abdominal Masses the first to study echolocation among bats, The procedure was called by Pulsed Ultrasound” with Dr. John Macvicar. which forms the basis for ultrasound physics. "hyperphonography". He used heat sensitive paper to record echoes. DR. JAMES WILLOCKS & PROFESSOR IAN In between 1877 - 1881 DONALD PIERRE CURIE (French physicist) found a 1942 Refined techniques for obstetric connection between electrical voltage and DR. GEORGE LUDWIG developed A-mode applications, including discovering the pressure on crystalline material. ultrasound equipment to detect gallstones. importance of a full bladder to visualize pelvic He discovered PIEZOELECTRICITY. structures. LATE 1940'S JACQUES AND PIERRE CURIE (1880) Dr. George Ludwig of University of 1962 First described the PIEZOELECTRIC EFFECT. Pennsylvania was first to record and study the Joseph Holmes, William Wright & Ralph PIEZOELECTRIC EFFECT – the change in difference in sound waves as they traveled Meyerdirk developed the first compound electric charge distribution of certain crystalline through tissues, organs, muscles, and contact B-mode scanner. materials following a mechanical stress. gallstones in animals. Father of Medical Ultrasound 1963 1915 The first commercial handheld, articulated-arm After the sinking of the Titanic, Paul Langevin, 1949-1951 compound contact B-mode scanner. a French professor and Curie’s student invented Douglas Howry and Joseph Holmes, from the the hydrophone to detect icebergs. University of Colorado, were some of the 1973 This was the first transducer. leading pioneers of B-mode ultrasound GEORGE KOSSOF developed new type that equipment, including the 2D B-mode linear could process the returning echoes and display BETWEEN 1920 – 1930 compound scanner. them as different shades of gray. ULTRASOUND is being used for physical John Reid and John Wild invented a handheld Grayscale imaging was born. therapy, sterilization of vaccine and cancer B-mode device to detect breast tumors. therapy in combination with radiation therapy. 1953 1942 1928 Drs. Inge Edler and Carl Hellmuth Hertz Discovery of doppler effect by sir Christian Soviet Physicist Sergei Sokolov use ultrasonic explored the use of ultrasound in the heart using Andreas Doppler energy for industrial purposes including a technique that added a continuous moving detection of flaws in metals. display of the returning echoes (M-mode) to 1950’s evaluate the motion of the heart valves. SHIGEO SATOMURA developed the first Doppler ultrasound device for medical diagnostic purposes. 1959 1990’s MODERN SONOGRAPHY Dr. Robert Rushmer & Dean Franklin Starting in the 1980s, ultrasound technology 1) 3D IMAGING developed a prototype of a continuous wave became more sophisticated with improved 2) 4D IMAGING doppler device image quality and 3D imaging capabilities. 3) COMPOUND IMAGING These improvements continued into the 1990s 4) ELASTOGRAPHY 1960’s with the adoption of 4D (real time) capabilities. 5) FUSION IMAGING DONALD BAKER and DENNIS WATKINS Ultrasound guided biopsies (endoscopic 6) CONTRAST IMAGING developed technology that led to the ultrasounds) also began in the 1990s. development of the first pulsed Doppler COMPACT & HANDHELD UNITS scanner. 2000’s – present 1) EMERGENCY DEPARTMENT A variety of compact, handheld devices have 2) REMOTE PLACES 1973 come onto the market in recent years. The 3) AMBULANCE DONALD BAKER developed technology that iPhone now has a telesonography app and 4) BATTLEFIELD led to the development of the first Duplex NASA has developed a virtual guidance 5) OUTER SPACE Doppler scanner. program for non-sonographers to perform ultrasounds in space. WHAT IS ULTRASOUND? 1974 Sound that exceeds a frequency of 20kHz. Duplex Doppler scanner was combined w/ 2D ULTRASOUND THEN AND NOW: It occurs in nature and is used by various imaging and pulsed Doppler called ATL Mark I 1916 – SONAR animals for navigating, detecting prey and EARLY 1950’s – WATER BATH IMMERSION communication. 1983 TECHNIQUE used in such application as automatic door CHIHIRO KASAI, KOROKU NAMEKAWA AND LATE 1950’s – COMPOUND B-SCANNER openers, and to detect flaws in metals. RYOZO OMOTO published a paper on cardiac EARLY 1980’s SONAR used by submarines which can locate application of color Doppler. 1) REAL-TIME SCANNER objects under water as well as determine the 2) B-SCANNER distance. 1984 LATE 1980’s The first color Doppler images were shown at 1) CONTINUOUS WAVE DOPPLER SONAR (Sound Navigation and Ranging) the meeting of RSNA. 2) PULSED DOPPLER A beam of ultrasound is transmitted from a 3) COLOR FLOW DOPPLER surface ship into the depths of the ocean, if it 1980’s 4) OBSTETRICS should intersect a submerged object, a small KAZUNORI BABA of the University of 5) GYNECOLOGY amount of the ultrasound will be reflected back Tokyo developed 3D ultrasound technology and 6) ABDOMINAL to the surface and detected. captured three-dimensional images of a fetus in 7) CARDIOLOGY it allows the accurate determination of direction 1986. 8) RADIOLOGY and distance. 9) VASCULAR MEDICINE 1987 Color-flow imaging started to take off in the United States WHAT IS ULTRASOUND? UNIT II: ULTRASOUND: USES AND ITS interest, due to the extreme differences in acoustic Ultrasound also has medical uses in both IMPORTANCE IN DIAGNOSIS OF DISEASES impedance. diagnostic and therapeutic applications: Obese patient 1) Physical & occupational therapy 1. Confirmation of a viable pregnancy and 2) Lithotripsy assessment of progress during the same. WHAT ARE THE BENEFITS & RISKS? 3) Diagnostic ultrasound 2. Detection of developmental/structural abnormalities in the fetus BENEFITS What is SONOGRAPHY? 3. Diagnosis and evaluation of liver, hepatobiliary, 1. Most ultrasound scanning is noninvasive (no The term used to specify the diagnostic imaging gallbladder, pancreatic and splenic diseases. needles or injections) and is usually painless. application of ultrasound. 4. Diagnosis and evaluation genitourinary problems 2. Ultrasound is widely available, easy-to-use and and gynecologic diseases. less expensive than other imaging methods. It uses frequencies between 1MHz -18MHz- 5. Assessment of small parts like the thyroid, 20MHz. submandibular and thyroid glands, breasts 3. Ultrasound imaging uses no ionizing radiation. The technique that uses ultrasound to produce (sonomammogram) and testes 4. Ultrasound scanning gives a clear picture of soft images. 6. Evaluation and diagnosis of soft tissue lesions, tissues that do not show up well on x-ray images. Also called “ultrasonography” joints and musculoskeletal 5. Ultrasound causes no health problems and may 7. Evaluation of the neonatal brain be repeated as often as is necessary. SONOGRAPHY 8. Evaluation of the chest/pleural effusions Uses NO IONIZING RADIATION. 9. Evaluation of the heart and diagnosis of cardiac Ultrasound transducers require the use of water RISKT problems For standard diagnostic ultrasound there are base gel as medium that will allow sound 10. Emergency assessment of blunt abdominal transmission through tissues. no known harmful effects on humans. trauma using FAST (Focused Assessment Most ultrasound scanning is noninvasive (no Sonography in Trauma) needles or injections) and is usually painless. DANGERS OF ULTRASOUND 11. As guide in Biopsy and interventional Procedures The two major possibilities with ultrasound are as Ultrasound scanning gives a clear picture of soft tissues that do not show up well on x-ray images. follows: UNIT III: BIOLOGICAL EFFECT: WEAKNESSESS & LIMITATION, BENEFITS & RISKS, DANGERS OF 1. DEVELOPMENT OF HEAT - tissues or water SONOGRAPHER ULTRASOUND absorb the ultrasound energy which increases Formerly called as “ultrasound technical specialist”, their temperature locally “ultrasound technologist”, ultrasound technologist” WEAKNESSES & LIMITATIONS OF ULTRASONIC 2. FORMATION OF BUBBLES (CAVITATION) - A person who performs medical ultrasound. IMAGING when dissolved gases come out of solution due It is not ideal tool for the examination of air- to local heat caused by ultrasound SONOLOGIST? containing structures since ultrasound greatly A person who interprets ultrasound studies, no attenuated by gas. However, there have been no substantiated ill-effects matter the specialty. Sonographic devices have trouble penetrating of ultrasound documented in studies in either humans bone. or animals. This being said, ultrasound should still be Ex: adult brain used only when necessary (i.e. better to be cautious). Sonography performs very poorly when there is a gas between the transducer and the organ of MODULE 2: RELEVANT TERMINOLOGIES SYNTHETIC PIEZOELECTRIC EFFECT AND ULTRASOUND TRANSDUCERS PIEZOELECTRIC EFFECT 1. LEAD ZIRCONATE TITANATE (PZT) 2. BARIUM TINATE A transducer converts one type of energy into The creation of electrical energy by applying 3. LEAD METANIOBATE another. another energy to a crystal. 4. AMMONIUM DIHYDROGEN PHOSPHATE Based upon the pulse-echo principle occurring with The generation of sound waves emitted from the 5. LITHIUM SULPHATE ultrasound piezoelectric crystals, ultrasound transducer crystals when precise electrical transducers convert: charges are applied to make them vibrate. a) Piezoelectric materials are crystalline materials ⎯ Electricity into sound = pulse PIEZO = Greek word that means to “press” or composed of dipolar molecules, which are ⎯ Sound into electricity = echo squeeze. positive at one end and negative at the other. Describes the manner in which some Normally these dipolar molecules have a random ULTRASOUND substances become electrically polarized when arrangement within the material and they are Defined as mechanical waves with higher stressed. unable to align themselves with an applied electric frequency than human can hear; mechanical field. waves with frequencies greater than 20,000 Hz – PIEZOELECTRIC EFFECT However, if the materials are heated above the 20 kHz Curie temperature in presence of an electric field, PIEZO→ is a Greek word “PIEZIN” that means the molecules align themselves with that field. FREQUENCY APPLICATION RANGE to “press or pressure”; therefore, piezoelectric b) THE PIEZOELECTRIC CRYSTAL AS ULTRASOUND ABOVE DIAGNOSTIC 1-10 MHz describes the manner in which some TRANSMITTER OF SOUND 20,000 Hz substances become electrically polarized when Piezoelectric materials are used in the stressed. OR production of ultrasound by converting: This is the ability of a material to generate an Electrical energy into Mechanical energy ABOVE 20 electrical charge in response to applied (sound) kHz pressure c) THE PIEZOELECTRIC CRYSTAL AS RECEIVER THERAPEUTI 0.7-1.0 MHz OF SOUND C A. PIEZOELECTRIC MATERIALS Piezoelectric materials are used in the Quartz- naturally occurring crystals detection of ultrasound by converting: Lead zirconate titanate- man made ceramics SURGERY 1-5 MHZ Mechanical energy (sound) into electrical NATURAL energy. 1. QUARTZ NOTE: INDUSTRIAL 25-400 kHz 2. TOURMALINE As the crystal diameter decreases, the beam 3. ROCHELLE SALT divergence increases. MILITARY 20-50 kHz As the crystal diameter increases, the beam divergence decreases  FREQUENCY MEDIUM SPEED IN ULTRASOUND 4. FREQUENCY1 Hertz= 1Cycle per second m/sec Ultrasound is the name given to high frequency It is the number of vibration (back and forth sound waves, which are above the human hearing AUDIBLE 16 Hz TO AIR (at 32º F) 331 movements) that a molecule makes per second. range. SOUND 20,000 Hz The number of times the cycle is repeated each Acoustic vibrations of frequencies higher than 20 second. OR kHz, non-audible by human ear. 5. VELOCITY Non ionizing radiation 16 Hz TO 20 The propagation velocity is the velocity at which kHz sound travels through a particular medium and ACOUSTIC VARIABLES is dependant on the compressibility and WATER (SEA) 1531 density of the medium. Usually, the harder the (at 77º F) 1. Period tissue, the faster the propagation velocity 2. Wavelength Velocity= Frequency x Wavelength 3. Amplitude 4. Frequency SOUND WAVES SOLID 5200 5. Velocity (STEEL) Sound is a mechanical energy that is 1. PERIOD transmitted by pressure waves through a medium. Period, T (s or µs) They oscillate at frequencies of 20 to 20, 000 FREQUENCY APPLICATION The TIME taken for one complete cycle to cycles/second also referred as Hertz (Hz) occur INFRA BELOW 16 Hz EARTHQUAKES 2. WAVELENGTH HERTZ Wavelength (λ), (m or mm) SOUND The unit of frequency Length of space over which one cycle occurs 1 Hertz = 1 cycle/second The extent of one complete wave cycle. It is the distance between successive equivalent density HEINRICH RUDOLF HERTZ SOUND February 22, 1857 – January 1, 1894 zones. He was the first to demonstrate the is a form of energy which causes a mechanical Expressed in units of meters, centimeters, existence of electromagnetic waves disturbance in the form of vibration of molecules millimeters within a medium. 3. AMPLITUDE ACOUSTIC VELOCITY In order to be transmitted, sound requires a The maximum displacement that occurs in an medium containing molecules, and therefore acoustic variable. (depth, height) It is the speed at which a wave propagation cannot travel through a vacuum. through the medium. The production of sound requires a vibrating The rate of transfer of mechanical vibrations. object. COMPRESSION 4. PROPAGATION MODULE III: PHYSICAL PRINCIPLES OF The periodic changes in pressure when DIAGNOSTIC ULTRASOUND Describes the formation of the high-pressure vibrating molecules interact with neighboring region. 1.1 WAVE EQUATION molecules are conveyed from one location to REFRACTION another. Velocity = Frequency x Wavelength It is used to describe the transmittal to distant The velocity of sound or ultrasound remains Describes the creation of the low-pressure regions remote from the sound source. constant for a particular medium. region. 5. ATTENUATION Increasing the frequency causes the The phase of the wave when the molecules are Is the process where in the intensity (loudness wavelength to decrease. pushed together is called compression, and of audible sound beam) of the beam is reduced. When going from a medium with one acoustic when apart, rarefaction Occurs during refraction, scattering, velocity to medium of another, the frequency of diffraction, divergence and absorption. the sound beam remains constant. Decrease in the intensity of the ultrasound 1.2 RESONANCE TYPES OF SOUND WAVES waves as they pass through tissues, measured in decibels per centimeter. The reinforcement or prolongation of sound by 1. LONGITUDINAL WAVES 6. ACOUSTIC IMPEDANCE reflection from a surface or by the synchronous particle motion is along the direction of the wave The resistance offered by tissues to the vibration of a neighboring object. energy propagation. That is, the molecule movement of particles caused by ultrasound The transfer of vibrating energy from one vibrates back and forth in the same direction as waves. system to another. the wave traveling It is equal to the product of the density of the Ex. Sound wave in liquids and tissues tissue and the speed of the ultrasound wave I 1.3 ACOUSTIC INTENSITY AND POWER 2. TRANSVERSE WAVES the tissue. ACOUSTIC INTENSITY particle motion is perpendicular to the direction 7. PULSE of the wave energy propagation. That is, the Force of sound is sent to soft tissues the rate of flow of energy through a unit area. molecule vibrates up and down in the same measured in Watts per square centimeter. (W/cm²) Sound interaction with soft tissue =bioeffects direction as the wave traveling. Referred to as “As the intensity of ultrasound increases, the Pulsing is determined by the transducer or shear waves or stress waves. displacement of an individual molecule in the probe crystal(s) and is not operator controlled. Ex. Sound wave produced by the bone. conducting medium will increase.” 8. Echo 3. AMPLITUDE Echo produced by soft tissues ULTRASONIC POWER It is the change in the magnitude of a physical Tissue interaction with sound = acoustic entity. It can be applied to pressure in the the ultrasonic intensity times the cross-sectional propagation properties medium or particle density, particle beam area. Echoes are received by the transducer crystals displacement or particle velocity in the medium. measured in Watts or milliwatts. Echoes are interpreted and processed by the ultrasound machine.  “At a given beam intensity, therefore, a broad 2.2 REFLECTIVITY 2.2. REFRACTION ultrasound transmission would have higher power A change in direction of the sound wave as it The reduction in reflected power caused by the than a narrow ultrasound beam.” passes from one tissue to a tissue of higher or introduction of an absorbing material. 2.1 ACOUSTIC IMPEDANCE The reflective quality or power of a surface or lower sound velocity material. 1. DEVIATION OF THE BEAM. The resistance offered by tissues to the 2. BENDING OF WAVES movement of particles caused by ultrasound 2.1 ACOUSTIC REFLECTION 3.3 SCATTERING waves. Occurs when the beam encounters an interface Reflection of a sound wave occurs when the Use to describe the reflection of sound at an that is irregular and smaller than the source wave passes between two tissues of different interface. densities. beam. The higher the density, the greater is the The return of the sound wave energy back to the 2.3.1. BACKSCATTERED ULTRASOUND acoustic impedance. transducer. Sounds scattered back to the transducer and The higher the velocity of sound in the medium, Is the redirection of a portion of the ultrasound contributed to image formation. the greater the acoustic impedance. beam each toward its source. 3.1. ACOUSTIC ABSORPTION Table 33-4 Acoustic Impedance for several It occurs when a wave strikes an object and is Denotes an all-or-nothing phenomenon, as in materials of Diagnostic Importance bounced off in different direction. the photoelectric absorption of an x-ray. MATERIAL ACOUSTIC IMPED ANCE kg/m2s (10-6) 2.1.1. SPECULAR INTERFACE 3.2. ATTENUATION Air 0.0004 Is the process where in the intensity (loudness Aluminum 17 Large smooth interfaces reflect sound like a of audible sound beam) of the beam is reduced. Blood 1.61 mirror 3.2. ATTENUATION Only the echoes returning to the machine are Bone 7.80 Decrease in the intensity of the ultrasound displayed Brain 1.58 waves as they pass through tissues, measured Specular reflectors will return echoes to the Fat 1.38 in decibels per centimeter. machine only if the sound beam is perpendicular Kidney 1.62 to the interface Is the process where in the intensity (loudness Liver 1.65 of audible sound beam) of the beam is reduced. Muscle 1.70 2.1.2. DIFFUSED INTERFACES Occurs during refraction, scattering, diffraction, Oil 1.43 Small interfaces or nooks and crannies divergence and absorption. Polyethylene 1.88 Most echoes that are imaged arise from small Decrease in the intensity of the ultrasound Soft tissue 1.63 interfaces within solid organs waves as they pass through tissues, measured Water 1.48 These echoes form the characteristic pattern of in decibels per centimeter. solid organs and other tissues