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RTITP LECTURE
ULTZ
| Term | Definition |
|---|---|
| - Ultrasound uses high-frequency sound waves to create images - Humans can hear_________________ but over 20000 is ultrasound > cannot be heard by humans | 20Hz to 20000 Hz |
| - _________ → energy is generated by the machine - ________ → crystal vibrates - Sound (Ultrasound waves) → mechanical vibrations are transmitted into the body | Electrical : Mechanical |
| - Sound (_______) → reflected sound waves return to the transducer - Mechanical → _______ vibrates in response to returning echoes - Electrical → _________ converts mechanical energy back to electrical signals; machine processes and produces image | Echoes : crystal : transducer |
| PROS (Advantages of Ultrasound) | Non-ionizing (no radiation exposure) Portable and flexible Easy to operate Space saver Cost effective Images muscles and tissues Real-time scanning No known long-term effects |
| CONS (Disadvantages of Ultrasound) | Unable to penetrate bone Depth of penetration is limited Operator-dependent |
| HISTORY - 1880: ____________________ discovered the Piezoelectric Effect -____________ developed piezoelectric materials as senders and receivers of high-frequency mechanical disturbances (ultrasound waves) through materials | Pierre and Jacques Curie : Paul Langevin |
| - Refers to the generation of an electrical response to applied pressure - Ability of certain materials to generate an electric charge from mechanical stress, OR change shape when given an electric voltage | Piezzoelectricity |
| Used in WW1 and WW2 by ships and submarines | Sound Navigation and Ranging (SONAR) |
| Key Historical Milestones - 1928: __________________________ (Soviet physicist) used ultrasound to detect hidden flaws in materials - _______: Medical use of ultrasound began | Sergei Yakovlevich Sokolov : 1930s |
| Early 1950s: - Problem: ____ interface between transducer and patient's skin - Solution: Patient placed in a ___________ | Air : bath of water |
| Late 1950s: - Problem: Inconvenient techniques (water bath) - Solution: First contact compound B-scanner with _________as lubricant | olive oil |
| APPEARANCE - ___________: without echoes “echo-fee” (ex. Cysts, gallbladder, vessels) - ___________: tissues with dimmer echoes than adjacent structures (ex. neoplasms) | Anechoic : Hypoechoic |
| APPEARANCE - _____________: Tissues with brighter echoses that adjacent structures (ex. Lipomas, stones) - _____________: same echogenic appearance, harder to differentiate organs - _____________: different acoustic appearance | Hyperechoic : Homogenous : Heterogenous |
| An anatomical path or fluid medium (like a full bladder or the liver) that allows ultrasound waves to pass deep into the body with very little interference - Provides a clean pathway to image deeper organs that might otherwise be hidden | Acoustic window |
| A dark (hypoechoic or anechoic) region that appears behind a highly reflective or attenuating structure like a gallstone, bone, or calcification | Acoustic shadowing - Happens because the dense structure blocks or absorbs the sound waves, leaving no signal for tissues deeper down |
| A bright region that shows up behind a weakly attenuating, fluid-filled structure like a simple cyst or the bladder | Acoustic enhancement - Happens because sound passes through fluid so easily that the machine overcompensates brightness for the tissues right behind it |
| - Ultrasound is a ______ - Propagates through ____________ and ___________ of air molecules | wave : compression : rarefaction |
| TYPES OF SOUND WAVES - (particles vibrate parallel to the direction of propagation) like sound waves in tissues and liquids | Longitudinal waves |
| TYPES OF SOUND WAVES - particles oscillate in the direction perpendicular to wave propagation like sound waves in bones | Transverse waves |
| RELATIONSHIP OF ACOUSTIC VELOCITY, COMPRESSIBILITY, AND DENSITY | ↑ Acoustic Velocity = ↓ Compressibility = ↑ Density |
| VELOCITY OF ULTRASOUND IN MATERIALS - Air - Fat/Oil - Water - Blood | 348 : 1500 : 1480 : 1570 |
| VELOCITY OF ULTRASOUND IN MATERIALS - Liver - Muscle - Soft tissue | 1550 : 1580 : 1540 |
| VELOCITY OF ULTRASOUND IN MATERIALS - Bone - Aluminum - Beryllium | 3360 : 2700 : 12890 |
| INTERACTIONS OF ULTRASOUND WITH TISSUE - Major interaction of interest - Sound waves bounce back at a boundary between two different tissue types - Creates bright lines or borders on the screen | Reflection |
| INTERACTIONS OF ULTRASOUND WITH TISSUE - Waves hit small or rough structures and spread out in different directions - Helps create the textured background view inside organs | Scattering |
| INTERACTIONS OF ULTRASOUND WITH TISSUE - The sound beam bends when it hits a border at an angle - Occurs because the two tissues have different sound speeds | Refraction |
| INTERACTIONS OF ULTRASOUND WITH TISSUE - Describes how the ultrasound beam naturally spreads out or bends as it moves away from the probe face or passes around small structures inside the body | Diffraction - Beam divergence changes wave intensity and limits lateral resolution |
| INTERACTIONS OF ULTRASOUND WITH TISSUE - Overlapping scattered waves add together (constructive) or cancel out (destructive) - Creates the grainy "speckle" pattern seen inside organs like the liver or kidneys | Interference |
| INTERACTIONS OF ULTRASOUND WITH TISSUE - Tissues take in the sound wave energy and turn it into tiny amounts of heat - Causes the beam to fade out with depth | Absorption |
| INTERACTIONS OF ULTRASOUND WITH TISSUE - Gradual loss of ultrasound energy as it travels through tissue - Combines effects of absorption, reflection, scattering, and refraction | Attenuation |
| - Preferred measure of ultrasound beam - Refers to loudness - Power that passes through a tissue - Expressed in mW/cm² | Ultrasound intensity |
| - Difference between max. and min. values of molecule displacement/pressure/velocity - Expressed in Decibels (dB) | Ultrasound amplitude |
| A device that changes electrical energy into high-frequency sound waves, sends them into the body, and catches the returning echoes to make pictures | Transducer |
| FREQUENCY RANGE AND PRIMARY USES OF LINEAR PROBE | 7-18 MHz - Vascular - Thyroid - Breast |
| FREQUENCY RANGE AND PRIMARY USES OF PHASED ARRAY PROBE | 1-5 MHz - Cardiac - Transcranial - Thoracic |
| FREQUENCY RANGE AND PRIMARY USES OF CURVED PROBE | 2-7 MHz - Abdominal - Obstetrics - Pelvic |
| FREQUENCY RANGE AND PRIMARY USES OF ENDOCAVITARY PROBE | 5-9 MHz - Transvaginal - Transrectal |
| FREQUENCY RANGE AND PRIMARY USES OF MICROCONVEX PROBE | 3-9 MHz - Pediatrics - Neonatal |
| Common material for piezzoelectric materials: - Synthetic ceramics like _____________________ (PZT) — most common - Natural minerals like _______ | Lead Zirconate Titanate : Quartz |
| - The ability of certain materials to generate an electric charge from mechanical stress - OR change shape when given an electric voltage | Piezzoelectric effect |
| 4 ARRAY TYPES OF PIEZOELECTRIC CRYSTALS - Crystals: Thin - Arrangement: Largest (256–512 elements) - Application: Superficial organs | Linear, Sequential |
| 4 ARRAY TYPES OF PIEZOELECTRIC CRYSTALS - Crystals: Thick - Arrangement: Smallest (64–128 elements) - Application: Deep organs | Linear, Sequential (Thick Crystals) |
| 4 ARRAY TYPES OF PIEZOELECTRIC CRYSTALS - Crystals: Thick - Application: Deep organs | Curvilinear, Sequential |
| 4 ARRAY TYPES OF PIEZOELECTRIC CRYSTALS - Crystals: Thin - Application: Superficial organs | Curvilinear, Phased |
| 4 TYPES OF ULTRASOUND RESOLUTION - Ability to distinguish two structures along the beam axis - Determined by pulse length | Axial Resolution (Longitudinal) |
| 4 TYPES OF ULTRASOUND RESOLUTION - Ability to distinguish two structures side-by-side - Determined by beam width | Lateral Resolution (Transverse) |
| 4 TYPES OF ULTRASOUND RESOLUTION - Governed by beam height (slice thickness) - Fixed focal point acoustic lens - Best at lens focal point - 1.5D transducers allow dynamic elevational focusing | Elevational Resolution |
| 4 TYPES OF ULTRASOUND RESOLUTION - Contributes to partial volume artifact - 5D Transducer (Linear Array): 5–7 stacked rows (elevational elements); electronic focusing in elevational (height) direction | Elevational Resolution |
| 4 TYPES OF ULTRASOUND RESOLUTION - Determined by frame rate (Hz) - Frame only complete when ALL beamlines done - Inversely proportional to: depth, beamlines, focal points | Temporal Resolution - One complete frame is built by transmitting all beamlines across the field of view |
| RELATIONSHIP OF SPATIAL PULSE LENGTH AND AXIAL RESOLUTION | Relationship: ↓ SPL = ↑ Axial Resolution - Higher frequency = shorter wavelength = shorter pulse = better resolution |
| RELATIONSHIP OF BEAM WIDTH AND LATERAL RESOLUTION | Narrower beam = better lateral resolution - Improved by: smaller transducer, greater focusing, higher scan line density |
| RELATIONSHIP OF SLICE THICKNESS AND ELEVATIONAL RESOLUTION | Slice thickness effect: - thick slice = poor elevational resolution = two separate objects appear as one - thin slice = good elevational resolution = two separate objects clearly seperated |
| Ways to increase Frame Rate | reduce imaging depth, reduce field width, reduce focal points, reduce beamlines per field |
| - Number of pulses emitted per second - Measured in Hz | Pulse Repetition Frequency (PRF) |
| - Time required from the beginning of one pulse to the beginning of the next - Measured in microseconds (μs) - Inversely related: PRP (μs) = 1 / PRF (μs) | Pulse Repetition Period (PRP) |
| - Time in which ultrasound pulses are emitted - Measured in milliseconds (ms) - Product of UTZ period and number of cycles in a pulse | Pulse Duration (PD) |
| - Fraction of time that ultrasound is actually emitted - Formula: DF = PD / PRP | Duty Factor (DF) |
| - Length over which an UTZ pulse occurs - Expressed in mm - ↓ SPL = ↑ Axial Resolution | Spatial Pulse Length (SPL) |
| WHAT STATIC MODE DISPLAY? - for measuring the depth of interfaces and to detect their separation accurately - Used for measuring midline shifts in the brain | A-Mode |
| WHAT STATIC MODE DISPLAY? - Depicted brightness of reflected wave will be equivalent to the intensity - Most widely used - Primarily for abdominal imaging | B-Mode |
| WHAT DYNAMIC IMAGING DISPLAY? - Ultrasonic Cardiography - Principal application of monitoring the heart | M-Mode |
| WHAT DYNAMIC IMAGING DISPLAY? - Allows for observation of structures in motion | REAL TIME |
| The change in the frequency or pitch of a wave when the source of the wave and the observer move closer together or farther apart | Doppler Effect |
| - Illustrates the direction and velocity of flow within a user-defined field of view - Brightness: Brighter pixels = higher flow; darker pixels = slower flow - Adjustable scale and field of view | Color Doppler |
| Color Convention of Color Doppler: - _____ = flow towards the transducer - _____= flow away from the transducer | Red : Blue |
Created by:
yulyae