Ultrasound Flashcards
Ultrasound uses high energy (or high frequency) sound waves which by definition have a frequency of
> 20 kHz
the speed of the wave. Constant in a given medium. This is how ultrasound determines depth of tissue - tissue/organ close to probe - wave returns first, longest time to return means the tissue is further away.
Velocity
number of cycles (waves) /second
Frequency
height of the waves.
Amplitude
less detail, farther travel
lower frequency
shorter distance, more detail
high frequency
Strong (high) amplitude waves returning to transducer are ______ on the image
bright (i.e bone deflects the wave showing bright image)
Weak/No amplitude waves (absorbed waves) are ______.
dark
Echogenecity
brightness of reflected waves
hyperechoic
A. high amplitude - bright
B. low amplitude - darker than surrounding tissue
C. non-reflecting, completely absorbs sound - black
high amplitude - bright
hypoechoic
A. high amplitude - bright
B. low amplitude - darker than surrounding tissue
C. non-reflecting, completely absorbs sound - black
low amplitude - darker than surrounding tissue
anechoic
A. high amplitude - bright
B. low amplitude - darker than surrounding tissue
C. non-reflecting, completely absorbs sound - black
non-reflecting, completely absorbs sound - black
Lateral resolution
can differentiate objects side by side
Axial resolution
differentiate objects above and below. High frequency better in both planes
Sound waves are ________ and can physically cause oscillation, or movement within materials
mechanical
The propagation speed of movement through materials varies depending on the _________.
makeup of the material
Speeds are highest in ______ and lowest in ______
solids, gases
When sound is transmitted through a medium (in this case, the body) & it encounters an object it is either:
Absorbed (this process may create heat)
Reflected back toward its source
Scattered in a different direction
A _____________ produces and emits pulses of sound waves
hand-held transducer
Transducers work on the principle of __________
piezoelectricity
Sound waves that are reflected and some that are scattered, return back out of the patient and are detected by the ______
receiver
The ________ is actually the same piece of equipment as the ________.
The receiver is actually the same piece of equipment as the transducer.
better resolution, less depth and penetration - (ex:vascular and ocular - tissues are close to surface and need great detail)
A. High Frequency Linear Array
B. Phased Array
C. Low frequency curvilinear Array
High Frequency Linear Array
(cardiac) projects from a focal source in an arc (wedge shape) to see between rib spaces
A. High Frequency Linear Array
B. Phased Array
C. Low frequency curvilinear Array
Phased Array
wedge shape - low frequency, wide field of view - abdominal
A. High Frequency Linear Array
B. Phased Array
C. Low frequency curvilinear Array
Low frequency curvilinear Array
Diagnostic ultrasound is typically in the range of
2-15 MHz
The _____ frequency is better for deeper imaging, but Detail is better with _____ frequency
The lower frequency is better for deeper imaging, but Detail is better with higher frequency
Reflected sound waves are termed
echoes.
Tissues will have different acoustic impedance, which is defined as__________.
density x propagation speed.
If density increases so does impedance
If speed increases impedance also increases
Attenuation of sound pulses is higher in ____ and in ____ than in ____.
air, bone, soft tissue
The greater the difference in _____ the greater the intensity of the _____
impedance, echo
imaging the patient prior to treatment to confirm the location and alignment of internal anatomy
Interfractional localization
imaging during the treatment to confirm that the location and alignment of internal anatomy
Intrafractional localization
A gel is placed on the patient’s skin to allow the transducer/receiver to directly connect or “_____” to the skin without an air gap.
couple
1 Hertz (HZ)= ?
1 cycle/sec
