First exam U/S and Radiology

Two dimensional mode

"B-mode" Default mode of most machines

M-Mode

"Motion" mode Analyze movement of structures over time I.E. Measure the size of the heart chambers or movement of valves (lung pleural to R/O pneumo)

BART

(Blue Away, Red Towards)

Reflection and propagation of sound waves through tissues depends on?

-Acoustic impedance -Attenuation

What makes a good image?

-Acoustic interfaces perpendicular to the ultrasound beam -Equal brightness from top to bottom -Have less extraneous depth.

Phased Array (footprint)

-Crystal fire at different times -Small footprint; wide field -Ability to focus and steer -Drawback- deeper structure=lower resolution The phased array principle Phased array waves arrive at the target image at the same time- where resolution is best Price of focus is beam divergence.

Linear (Frequency)

-Each crystal creates a single scan line -Rectangular image -Good for imaging small parts & shallow structures -Higher frequency -Good for vascular

Frequency

-Inversely proportional to wavelength -Varies according to the specific velocity of sound in a given tissue.

Gain: Adjust to accentuate the appearance Time gain compensation

-Near gain or far gain -Adjusts the strength (amplitude) of returning signals based on depth -If too low, image will appear dark -If to high, image bright and white

Knobology: Brightness

-Start by adjusting the brightness -Turn the brightness to highest point, then slowly turn it down until the bottom is black or disappears

Intensity

-The concentration of power per unit area -Determines how much heat is generated in tissues.

Transducer movements

1) sliding 2) tilting (framing/sweeping) - used to obtain serial cross-sectional images of solid organs of a fluid collection 3) rocking - often used to center the image on the screen 4) rotating- used to align the US beam with the long or short axis of a structure

Adjusting Gain?

Adjusting gain only manipulates the computer generates image *DOES NOT affect signal quality

Depth of structures?

Along the axis of the US beam is determined by the time delay for echoes to return to the transducer

Power Doppler

Analyzes only amplitude of returning echos Level of brightness correlates with magnitude of flow No info on direction of flow (not used for cardiac) Ex: Venous thrombosis

ALARA

As Low As Reasonably Achievable

Blood flow

Blood moving towards the transducer shifts echos to a higher frequency. Blood moves away - lower frequency. Angling toward the direction of blood flow = Positive doppler shift

High Acouostic Impedence

Calcium, ribs-less sound reflected back to transducer from the calcified area

Depth

Default focal zone depth is typically center of the screen Low frequency Low resolution Longer depth

Resolution: Axial

Determined by soundwave freq.

Resolution: lateral

Determined by the width of US be a, which is influenced by diameter and frequency.

Acoustic impedance

Differences in acoustic impedance determine reflectivity of sound waves at tissue interfaces Greater differences = greater reflection of sound waves

Absorption

Energy transferred from the US beam to tissues as heat

Elevational

Fixed property of the transducer Refers to the ability to resolve objects w the height or thickness of the ultrasound.

Transducer type: Phased array Frequency Range: Imaging Depth: Applications:

Frequency Range: 1-5 MHz Imaging Depth: 35 cm Applications: Heart, inferior vena cava, lungs, pleura, abdomen

Transducer type: Linear Frequency Range: Imaging Depth: Applications:

Frequency Range: 5-10 MHz Imaging Depth: 9cm Applications: arteries/veins pleura, skin/soft tissues, musculoskeletal, testicles/hernia, eyes, breast

Transducer type: Intracavity Frequency Range: Imaging Depth: Applications:

Frequency Range: 5-8 MHz Imaging Depth: 13 cm Applications: Uterus/ovaries, Pharynx

Transducer type: Curvilinear Frequency Range: Imaging Depth: Applications:

Frequency Range:2-5 MHz Imaging Depth: 30cm Applications:Gallbladder, kidney, liver, bladder, abd aorta, abd free fluid, uterus/ovaries

Side Lobes/Grating Lobes

Grating occurs with phased array transducer

Comet tails →

High amplitude tail

Shorter wavelengths

Higher frequency Higher resolution images Penetrate too shallow depths

Transducer Frequency: Higher frequency= Lower frequency =

Higher frequency=better resolution, shorter penetration lower =longer penetration

Overcoming attenuation?

Increase gain Amplify signal in post processing

To Optimize view:

Look at pt position (gastric US - right lateral position), probe

Longer wavelengths

Lower frequency Lower resolution Penetrate deep

Transverse plane *out of plane

Marker should be pointed to operators left side

Longitudinal (coronal & sagittal) *in plane

Marker should be pointed to patients head

Resolution (measured?)

Measured by wave length used

Doppler imaging

Measures a change in freq.

Focal Zone

Narrowest part of the ultrasound beam where resolution is the greatest Region of highest intensity

Color Flow Doppler: Based on PWD with multiple sample volumes Sonographer selects area of interest Multiple lines with multiple sample volumes Mean frequencies are calculated at each spot

RED=blood moving towards the transducer BLUE=blood is moving away from the transducer GREEN= turbulence (left-laminar) (right-turbulent) Brightness corresponds to velocity Color corresponds to direction of flow

Deflection

Results in a reduction in echo amplitude

Resolution: elevational

Slice thickness resolution determined by transducer thickness

Ultrasound Sound waves

Sound waves at a frequency above the average human audible range (>20Hz) Frequencies used in Ultrasound 2-18 MHz U/S images are generated by sound waves reflected and scattered back to the transducer

Piezoelectric effect

The ability of certain crystals to generate vibrations with the application of electricity

Resolution: temporal

The ability of image moving structures

Axial

The ability to differentiate two objects along the axis of the ultrasound beam. -Is the vertical resolution on the screen -Depends on transducer frequency the higher the frequency:, the better axial resolution, shallower penetration

Lateral (horizontal)

The ability to differentiate two objects perpendicular to the US beam Decreases as deeper structures are images d/t divergence and increased. of the ultrasound Optimized Lateral resolution by placing target structure in the focal zone.

Transducers receive and record ?

The intensity of returning sound waves

Attenuation

The loss of energy as sound waves travel through tissues D/T absorption, deflection & divergence of sound

propogation speed

The velocity of sound in tissues (varies depending on physical properties of tissues)

Injuries:

Thermal (heat generation) Nonthermal (Cavation) from contrast enhanced US.

Screen orientation

Top corresponds with probe face Tranduscer marker corresponds with left of screen Heart US - transducer marker corresponds to right of screen

True pathology should be visualized in at least

True pathology should be visualized in at least two planes. Suspected pathology that is not seen in multiple planes is most likely an artifact.

Higher frequencies

Used in Linear array transducers to visualize superficial structures *(vascular & peripheral nerves)

Lower frequencies

Used in curvilinear & phased array transducers to visualize paper structures in the thorax, abdomen & pelvis.

Artifacts arise when

When one or more properties of sound are violated. Artifacts are false images, or parts of images, that do not represent true anatomic structures.

Mirroring artifact-

aorta, pleural, calcified edge of aorta Strong reflector (diaphram, calcified aorta) creates a mirror image that apprears to be behind target image

Resolution of ultrasound images is divided into four different types:

axial, lateral, elevational, and temporal.

Coronal plane

divides body into front and back *frontal plane

Sagittal plane

divides body into left and right.

Transverse plane

divides the body into superior and inferior parts (upper and lower) *Short axis plane

(Artifacts) Reverberation:

equally spaced bright liner echos from repeated reflections from air space Looks like a ladder

Resolution

high frequency high resolution shorter depth

Point-of-care ultrasound

is defined as a goal-directed, bedside ultrasound examination performed by a healthcare provider to answer a specific diagnostic question or to guide performance of an invasive procedure.

Hypoechoic -

iso, various gray shades → muscles, solid organs Reflect some sound waves but less than surrounding structures

Divergance

loss of US be a, intensity as the beam widens

Temporal

refers to clarify or resolutions of moving structures.

Hyperechoic

reflect greater than surrounding structures → bones, nerves, fascial plane Reflect the most sound waves Appear bright on US Calcified & dense

Spectral Doppler

represented graphically Y-axis: Velocity X-Axis: time quantitative assessment of velocities: Pulse wave, continuous wave

Murphys Point:

see more in Trendelenburg position for gastric hemorrhage

Average power

total energy on a tissue in a specific time

Anechoic

transmit all sound waves w/o reflecting → fluid filled structure → vessel Black Structure that transmits all sound waves Fluid-filled structures *blood vessels