Physics Flashcards
Ultrasound systems used for breast imaging require what types of resolution?
Spatial and Contrast
What type of probe has side-by-side piezoelectric crystals, sequencing and electronic phasing, and wide acoustic window?
Linear Array
Wide acoustic window in the near field allows better demonstration of what?
Superficial structures without beam divergence
What type of resolution does a higher frequency improve?
Axial
What is axial resolution?
Ability to differentiate two closely spaced echo interfaces lying in the direction of the sound beam.
How do bandwidth and pulse length pertain to each other?
Inversely proportional
Broader bandwidths improves?
Spatial and contrast resolution
Focusing affects the sound beam how?
thickness and width
A narrower beam improves what?
Resolution and intensifies sound energy at the focus.
Lateral resolution is best where?
At the focus
The ability to resolve two closely spaced interfaces lying side-by-side perpendicular to the sound beam?
Lateral resolution
Focusing that occurs along the long axis of the linear array transducer?
Variable electronic focusing
A shallow elevation focus of a high frequency, linear array transducer improves?
Near field detail and reduces slice thickness
Resolution refers to what?
The size of the smallest object depicted on the ultrasound image given adequate contrast.
Spatial resolution is measured in three planes:
Axial, lateral, and elevation
Spatial resolution is primarily effected by:
Frequency, focusing, and scan lines
Axial resolution improves with what?
Higher frequencies, shorter pulse lengths, and broader bandwidth transducers
Ability of ultrasound system to distinguish anatomic structures based on variations in echo brightness?
Contrast resolution
What type of resolution helps detect a subtle, isoechoic lesion in a fatty breast?
Contrast resolution
What is temporal resolution?
Ability to distinguish moving objects or dynamics over time. (Not typically effected with breast imaging due to depth)
Temporal resolution is limited by what?
Frame rate
What setting affects the amplitude of the transmit voltage and therefore, the intensity of the transmitted sound beam?
Output power
What does not affect the intensity of the sound beam transmitted?
Overall gain
The ratio of the smallest to the largest signal strength the system can handle without distortion?
Dynamic range
What allows a narrow transmit beam over a greater depth?
Multiple focal zones
Dynamic range effects what resolution?
Contrast resolution
Number of images displayed per second and affects temporal resolution?
Frame rate
How do you alter frame rate?
Focal zone, depth, frame size, compound imaging, or Doppler
Multiple transmit foci ____ frame rate. Reduced depth and image size ____ frame rate.
decreases, increases
Ultrasound pulses causes the microbubbles to vibrate causing emission of harmonic frequencies for what?
Doppler contrast agents
Represents a change in the direction of the sound beam as it passes from one medium to another?
Refraction
Occurs at curved edges and with oblique incidence to Coopers ligaments?
Refraction edge shadowing
If the speed of sound is slower than soft tissue, post echoes are registered _____ than in reality.
deeper (propagation speed error)
If the speed of sound is faster than in soft tissue, reflectors will be placed ____ to the transducer than in reality.
closer (propagation speed error)
Color or power Doppler motion artifact produced from tissue vibration from chest when patient hums?
fremitus
How is fremitus useful?
Differentiating a true mass from normal tissue. Normal tissue with transmit Doppler artifact.
What scan plane is best suited for evaluation of major lactiferous ducts?
radial
What thickness should a stand-of pad not exceed for transducers with an elevation focus of <1.5cm?
1cm
What does 123 stand for in the 123-ABC annotation method?
Distance of mass from the nipple
1= near nipple/areolar
2= mid distance from the nipple
3= periphery of breast
What does ABC stand for in the 123-ABC annotation method?
Depth of lesion in breast
A= near skin
B= mammary zone
C= near chest wall
