RDT121 - Ultrasound - Radiologic Technology Program PDF

​ ​Radiologic Technology Program​ ​ ​ Prepared by: ​ RDT121- Ultrasound ​ ​ ​ Symphony Apostol, RDT-3B ________________________________________________________________________________________...

​ ​Radiologic Technology Program​ ​ ​ Prepared by: ​ RDT121- Ultrasound ​ ​ ​ Symphony Apostol, RDT-3B ________________________________________________________________________________________ ACOUSTIC VARIABLES Chapter 1:Introduction to Diagnostic Ultrasound _________________________________________________ 1.​ PERIOD 2.​ WAVELENGTH AUDIBLE SOUND 3.​ AMPLITUDE ​ Sound is a form of energy which causes a mechanical 4.​ FREQUENCY disturbance in the form of vibration of molecules within a 5.​ VELOCITY medium. 6.​ POWER ​ Sound is a mechanical wave that travels in a medium in a 7.​ INTENSITY LONGITUDINAL WAVE. _________________________________________________ ​ Sound requires a medium containing molecules and 1.​ PERIOD (s or us) therefore cannot travel through a vacuum. ​ The TIME taken for one complete cycle to occur ​ Sound requires a vibrating object. ​ When a sound travels through a medium: PERIOD FREQUENCY ○​ The molecules of that medium are alternately ⬆ ⇩ compressed (squeezed) and rarefied (stretch) PERIOD FREQUENCY TYPES OF SOUND WAVES ⇩ ⬆ 1.​ LONGITUDINAL OR COMPRESSION WAVES 2.​ TRANSVERSE WAVES OR SHEAR WAVES PERIOD = 1/ FREQUENCY 2.​ WAVELENGTH (λ), (mm) CATEGORIES OF SOUND ​ Length/ DISTANCE of space over which cycle 1.​ ULTRASOUND occurs 2.​ AUDIBLE SOUND ​ Length of a wave or cycle 3.​ INFRASOUND 3.​ AMPLITUDE ​ The maximum displacement that occurs in an CATEGORIES FREQUENCY APPLICATION RANGE acoustic variable (DEPTH,HEIGHT) OF SOUND ​ Amplitude is defined by the difference between the peak (maximum) or trough (minimum) of ABOVE 20,000 DIAGNOSTIC 1-10 MHz the wave and the average value Hz or ABOVE 20 kHz ​ Unit of Amplitude THERAPEUTIC 0.7-1.0 MHz ○​ expressed in Pressure parameters - ULTRASOUND SURGERY 1-5MHz Pascals or MPa ​ Amplitude diminishes as sound propagates INDUSTRIAL 25-400kHz through the body (Attenuation) ​ Sound pressure- Pascal MILITARY 20-50kHz ​ Sound pressure level- Decibel ○​ 1 Pa = 94 dB SPL FREQUENCY MEDIUM SPEED IN ○​ 1 dB SPL = 0.00002244 Pa m/sec ​ Amplitude decreases usually by 1 dB per 1 MHz per 1 centimeter traveled AUDIBLE BETWEEN 16 AIR (at 32ºF) 331 SOUND Hz to 20,000 4.​ FREQUENCY (Hz) Hz or WATER (SEA) (at 1531 16 Hz to 20 ​ Is the number of cycles that occurs in one 77ºF) kHz second SOLID (STEEL) 5200 ​ C/sec ​ It affects penetration of sound and image quality FREQUENCY APPLICATION (resolution) ​ 1 Hertz = 1 Cycle per second INFRASOUND BELOW 16 Hz EARTHQUAKES ○​ Sonography uses pulsed ultrasound: ​ Ex.: A few cycles (2-3 cycles) of ultrasound separated in time with gaps of no signal. ​ Pulse repetition frequency (PRF) ○​ Number of pulses occurring in 1 s. REFERENCE: PPT ​ ​ Allyza Joyce Anajao, RRT,MSRT Professor ​ ​ Radiologic Technology Program​ ​ ​ Prepared by: ​ RDT121- Ultrasound ​ ​ ​ Symphony Apostol, RDT-3B ________________________________________________________________________________________ ○​ Usually expressed in kHz ​ It is dependent on the Power (Watt) and the cross ​ PRP decreases as PRF increases. sectional area (cm2) of a sound beam ○​ More pulse occur in a second, less time ○​ INTENSITY = Watt/cm2 from one to the next. THE HISTORY OF ULTRASOUND PRP PRF 1794: LAZZARO SPALLANZANI ⇩ ⬆ ​ First to study ultrasound physics by deducing Bats PRP PRF (echolocation) ⬆ ⇩ 1826: JEAN DANIEL COLLADON ​ Uses Church Bell (early ultrasound ”transducer”) to PRP = 1/PRF calculate Speed of Sound through Water. Prove Sound PERIOD = 1/FREQUENCY travelled faster through water than air. ​ Pulse Duration (ms: ○​ TIME it takes for one pulse to occur 1842: CHRISTIAN ANDREAS DOPPLER ○​ PD = Period x # of cycles in the pulse ​ Suggests that the frequency of a sound wave depends on the speed of the source. PD vs FREQUENCY ​ “Doppler Effect” PD FREQUENCY 1880: Pierre & Jacques Curie ⇩ ⬆ ​ Discover the Piezzo- Electric Effect PD FREQUENCY 1815: PAUL LANGEVIN ⬆ ⇩ ​ After Titanic Sinking (1912) Invents Hydrophone (1st Transducer) to detect Icebergs and submarines during 5.​ VELOCITY (m/sec) WW1 ​ Is velocity at which sound travels through a particular medium 1942: KARL DUSSIK ​ Is dependant on the compressibility and density of ​ First physician to use ultrasound for medical diagnosis the medium (brain tumors) ​ Usually, the harder the tissue, the faster the propagation velocity. 1948: GEORGE LUDWIG M.D ​ First described the use of ultrasound to diagnose gallstones Density ⬆ 1953: INGE EDLER AND HELLMUTH HERTZ Hardness Compressibility ​ Performed the first successful echocardiogram Stiffness Medium 1958: AIN DONALD ​ The faster the Utz propagation Speed. ​ Pioneer of OB-GYN Ultrasound ​ The velocity os the sound wave in a medium is related to the wavelength.. 1950’s: DOUGHLASS HOWRY & JOSEPH HOLMES ​ Pioneer 2D B-mode ultrasound. ​ EARLY 1950’S ​ Because air does not transmitted ultrasound waves efficiently, the air interface between the transducer and the patient’s skin was initially a problem. ​ Early scanning technique required the patient to be 6.​ POWER (Watts) immersed in a bath of water in order to provide good ​ Is the rate of energy transferred through the transmission of sound wave into the body. sound wave. ​ Power is proportional to the amplitude squared of LATE 1950’s a sound wave ​ The first contact compound B-scanner (using olive oil as ○​ P= A2 lubricant) was developed. This equipment used an articulating arm to produce static images. 7.​ INTENSITY (Watt/cm2) 1966: DON BAKER, DENNIS WATKINS, AND JOHN REID ​ Is the concentration of energy in a sound ​ Pulsed Doppler ultrasound technology wave. REFERENCE: PPT ​ ​ Allyza Joyce Anajao, RRT,MSRT Professor ​ ​ Radiologic Technology Program​ ​ ​ Prepared by: ​ RDT121- Ultrasound ​ ​ ​ Symphony Apostol, RDT-3B ________________________________________________________________________________________ 1970’s: CONTINUOUS WAVE DOPPLER ​ Spectral wave Doppler and color Doppler ultrasound Instruments 1980’s: KAZUNORI BABA ​ 3D ultrasound technology and captured three-dimensional images of a fetus in 1986 1990’s ​ 4D (real time) capabilities and ultrasound guided biopsies _________________________________________________ REFERENCE: PPT ​ ​ Allyza Joyce Anajao, RRT,MSRT Professor ​ ​ Radiologic Technology Program​ ​ ​ Prepared by: ​ RDT121- Ultrasound ​ ​ ​ Symphony Apostol, RDT-3B ________________________________________________________________________________________ ​ Piezoelectric materials are used in the production of Chapter 2: The Piezoelectric Effect ultrasound by converting: _________________________________________________ ○​ Electric energy into Mechanical energy (sound) ○​ E=M PIEZOELECTRIC MATERIALS/ELECTROCERAMIC ★​ Quartz ○​ Naturally occurring crystals THE PIEZOELECTRIC CRYSTAL AS RECEIVER OF SOUND ★​ Lead zirconate titanate (PZT) ​ Piezoelectric materials are used in the detection of echo ○​ Man made ceramics by converting: ★​ Plumbium zirconate titanate (PZT) ○​ Mechanical energy (sound) into Electrical energy ○​ M=E PIEZO ​ Is a Greek word “PIEZIN” means to “press or pressure, NOTE*: squeeze” ​ As the crystal diameter decreases, the beam divergence ​ This is the ability of a material to generate an electrical increases. charge in response to applied pressure. ​ As the crystal diameter increases the beam divergence decreases. STEP BY STEP SIMPLIFIED EXPLANATION OF HOW CRYSTAL SIZE DIAMETER BEAM DIVERGENCE PIEZOELECTRIC EFFECT WORKS IN AN ULTRASOUND TRANSDUCER: ⇩ ⬆ 1.​ Piezoelectric Material CRYSTAL SIZE DIAMETER BEAM DIVERGENCE 2.​ Mechanical Pressure Or Stress 3.​ Electric Field ⬆ ⇩ 4.​ Sound Wave Transmission 5.​ Receiving Echoes _________________________________________________ 6.​ Piezoelectric Response 7.​ Electric Signal Generation 8.​ Image Formation 1.​ PIEZOELECTRIC MATERIALS NATURAL SYNTHETIC 1. Quartz 1. Lead Zirconate Titanate (PZT) 2. Tourmaline 2. Barium Titanate 3. Rochelle Salt 3. Lead Metaniobate 4. Ammonium dihydrogen phosphate 5. Lithium Sulphate ​ Piezoelectric materials are crystalline materials composed of dipolar molecules. ​ Positive at one end and negative at the other. ​ Normally these dipolar molecules have a random arrangement. ​ They are unable to align themselves without an applied electric field. ​ If the materials are heated above the Curie temperature in presence of an electric field, the molecules align themselves with that field. THE PIEZOELECTRIC CRYSTAL AS TRANSMITTER OF SOUND REFERENCE: PPT ​ ​ Allyza Joyce Anajao, RRT,MSRT Professor ​ ​ Radiologic Technology Program​ ​ ​ Prepared by: ​ RDT121- Ultrasound ​ ​ ​ Symphony Apostol, RDT-3B ________________________________________________________________________________________ SUBSTANCE ACOUSTIC SPEED (m/s) Chapter 3:Acoustic Impedance IMPEDANCE IN _________________________________________________ MEGARAYLS ACOUSTIC IMPEDANCE (Z) (kg/m2/s) X 106 ​ The resistance offered by tissues to the movement of Air 0.0004 330 particles caused by the ultrasound waves. ​ Ex. Bone tissue Vs. Soft Tissue Fat 1.38 1450 ​ Acoustic impedance is the opposition of a medium to a longitudinal wave. Water 1.48 1480 ○​ z= p*v ​ p= medium density in kg/m3 Blood 1.61 1570 ​ v= is the speed of sound in m/s ​ The unit of z is “Rayls” which is kg/m2/s Kidney 1.62 1560 ​ A substance which has densely packed molecules will have Soft Tissue 1.63 1540 a high Acoustic impedance. (average) ○​ Ex. Bone ​ A substance which has loosely packed particles will have a Liver 1.65 1550 low acoustic impedance. ○​ Ex. Air Muscle 1.70 1580 ​ Z= Product of density and speed ○​ Z= pc Bone 7.80 3500 ​ Density (p) kg/m3 ​ Speed of sound © m/s PZT (crystal) 30 3870 ​ Acoustic impedance rayls=kg/m2/s ACOUSTIC IMPEDANCE MISMATCH AND REFLECTION MEDIUM DENSITY ( SPEED OF ACOUSTIC kg/m3) ULTRASOUN IMPEDANCE ​ The greater the impedance mismatch, the greater the D per s (kg/m2/s) percentage of energy that will be reflected at the interface or boundary between one medium and another. Air 1.3 330 429 ACOUSTIC IMPEDANCE REFLECTION Water 1000 1500 1.5x106 MISMATCH Blood 1060 1570 1.66x106 ⬆ ⬆ Fat 925 1450 1.34x10 6 ​ Substances with a small difference in acoustic impedance ○​ Small amount of energy is reflected but the Muscle 1075 1590 1.70x106 majority is transmitted. (average) ​ ZR= 5% ; ZT= 95% ​ Substances with a large difference in acoustic impedance BOne (varies) 1400-1900 4080 5.7x106 to ○​ Large amount of energy is reflected and a 7.8x106 small amount is transmitted. Barium 5600 5500 30.8x106 ​ ZR= 95% ; ZT= 1% titanate (transducer material) ​ The average velocity of ultrasonic waves in soft tissue is: ○​ 1540 meters per second ACOUSTIC IMPEDANCE MISMATCH ​ The difference in acoustic impedance between two substances is known as the acoustic impedance mismatch REFERENCE: PPT ​ ​ Allyza Joyce Anajao, RRT,MSRT Professor ​ ​ Radiologic Technology Program​ ​ ​ Prepared by: ​ RDT121- Ultrasound ​ ​ ​ Symphony Apostol, RDT-3B ________________________________________________________________________________________ ​ If there is a large acoustic mismatch ○​ Ex. between (bone & muscle); (air & soft tissue) MISMATCH REFLECTION TRANSMISSION ⬆ ⬆ ⇩ MISMATCH FREQUENCY TRANSMISSION ⇩ ⇩ ⬆ ​ Therefore, it is not practical to use ultrasound to produce images of soft tissue subjects containing GAS OR BONE. ​ Ultrasound Imaging is very good at discriminating between substances with small differences in acoustic impedance such as soft tissues _________________________________________________ REFERENCE: PPT ​ ​ Allyza Joyce Anajao, RRT,MSRT Professor ​ ​ Radiologic Technology Program​ ​ ​ Prepared by: ​ RDT121- Ultrasound ​ ​ ​ Symphony Apostol, RDT-3B ________________________________________________________________________________________ FREQUENCY NEAR FIELD FAR FIELD Chapter 4:Ultrasound Beam _________________________________________________ INCREASE LONG LESS ULTRASOUND BEAM DECREASE SHORT MORE ​ The area through which the sound energy emitted from the ultrasound transducer travels is known as the ultrasound beam. CRYSTAL NEAR FIELD FAR FIELD ​ The beam is three dimensional and symmetrical around DIAMETER its central axis. NARROW DECREASE INCREASE WIDE INCREASE DECREASE THE SHAPE OF THE ULTRASOUND BEAM IS AFFECTED BY: ​ The size and shape of the ultrasound source ​ The beam frequency ​ Beam focusing EFFECT OF BEAM FREQUENCY ​ The length of the near field increases as the beam frequency ​ It can be divided in two regions: is increased. 1.​ Near Field (Fresnel zone) ​ The length of the far field increases as the beam frequency 2.​ Far Field (Fraunhofer zone) is decreased. ​ In addition, they cause a degradation of lateral resolution due to the effective widening of the beam in ​ Increasing the frequency will result in longer near field the scan plane. and less far field divergence. (vice versa) ​ A narrow crystal diameter will result in a narrower beam in the near field, and there is more divergence in the far field. REFERENCE: PPT ​ ​ Allyza Joyce Anajao, RRT,MSRT Professor ​ ​ Radiologic Technology Program​ ​ ​ Prepared by: ​ RDT121- Ultrasound ​ ​ ​ Symphony Apostol, RDT-3B ________________________________________________________________________________________ BEAM WIDTH ​ Beam width refers to the dimension of the beam in the scan plane. UTZ BEAM WIDTH LAT. RESOLUTION ⬆ ⇩ UTZ BEAM WIDTH LAT. RESOLUTION ⇩ ⬆ ​ The beam width affects the LATERAL RESOLUTION ○​ The narrower the beam width, the better the Lateral resolution. FREQUENCY LATERAL BEAM WIDTH RESOLUTION ⬆ ⬆ ⇩ FREQUENCY LATERAL BEAM WIDTH RESOLUTION ⇩ ⇩ ⬆ REFERENCE: PPT ​ ​ Allyza Joyce Anajao, RRT,MSRT Professor