Ultrasound Flashcards
Why Ultrasound?
- Ultrasound is harmless. - The exams are controlled by the sonographer. - You can scan in whatever plane you choose. - We can target a specific area.
Ultrasound was first used on humans in what year
1950
Oscilloscope
A mode
With computer revolution came what ?
“B” mode and real-time scanning.
How does Diagnostic Ultrasound work?
The transducer sends out a burst of high frequency sound, then draws in the echoes as they return.
Sound involves
mechanical motion in the medium through which it travels.
The pressure variations in the sound wave cause particles of the medium to
vibrate back and forth
Regions of low pressure and density are call
rarefactions
Regions of high pressure and density are called
compressions
Ultrasound cannot image through
bone or air
Our machine must know how fast the sound is traveling in order to
place the echoes at the proper depth
In soft tissue sound travels approximately
1,540 meters/sec
In AIR sound travels approximately
330 meters/sec
In BONE sound travels approximately
4080 meters/sec
You cannot hear ultrasound and it does not cause
infections
The range of human hearing is from?
20 cycles/sec (hz) to 20,000 cycles /sec.
hz ?
Cycles per secnond
Ultrasound operates from
2,000,000 cycles/sec to 15,000,000 cycles/sec
Higher frequencies give better resolution, but lack
penetrating power.
Lower frequencies penetrate deeper
but give up resolution
Echoes produced by moving objects have frequencies ?
different from the original frequency
How does Ultrasound help me?
- Monitoring fetal heart - Evaluating blood flow in the heart and carotid arteries - Detecting the presence or absence of blood flow and its direction, speed, and character
Doppler ultrasound allows us to
detect and quantify movement (blood flow).
c =
Speed of sound in tissue
