LEC 5 ECHOCARDIOGRAPHY Flashcards
Soundwaves are mechianical vibrations that induce alternate refraction and compression of any physical medium they pass
Ultrasound waves
Number of ultrasound waves in a 1-second interval, Cycles/sec
Frequency
The speed that a sound wave moves through the body
Velocity propagation
the distance from peak to peak of an ultrasound wave, can be calculated by dividing f in Hz
Wavelength
Height of the ultrasound wave or loudness measured in decibels (dB)
Amplitude
Characteristic of each tissue defined by tissue density (r) and propagation of velocity (c)
Acoustic impedance
Return of ultrasound signal to the transducer from a smooth tissue boundary
Reflection
Deflection of ultrasound from a straight path becuase of differences in acoustic impedance
Refraction
Radiation of ultrasound in multiple directions from a small structure such as blood cells
Scattering
Loss in signal strength due to absorption of ultrasound energy by tissues
Attenuation
Ultrasound transducers use what kind of crystal to alternately transmit and receive ultrasound signals?
piezoelectric crystal
Give characteristics of a transducer
Focal depth
Aperture
Power output
Bandwidth
image is generated from data obtained by sweeping the ultrasound beam across tomographic plane
2D DIMENSIONAL
Data are shown on the video monitor either scrolling or sweeping across screen at 50 to 100 mm/s
M-mode
it is based on the change in frequency of the backscattered signal from small moving structures
Doppler ultrasound
uses 2 ultrasound crystals, one continuously transmits and one constinuously receives ultrasound signal
Continuous wave doppler
allows sampling of blood flow velocities from a specific intercardiac depth
Pulsed dopplerr
Uses the pulsed doppler principle to generate a 2d image or map of blood flow velocity
Color doppler flow
provides a panoramic view of the abdomen and pelvis and is noninvasive
Transabdominal
provides a more limited pelvic view and requires insertion of a probe into the vagina
Transvaginal ultrasound
one of the most commonly performed cardiac investigations
Transthoracic echocardiogram
Offers the advantage of improved image quality compared to transthoracic images, particularly of posterior structures such as pulmonary veins
Transesophageal echocardiography
refers to the injection into the bloodstream of an agent that results in increased echogenicity of the blood or myocardium on ultrasound imaging
Contrast echocardiography
uses a catheter like ultrasound probe that is passed into the right heart chambers from the femoral vein
Intracardiac echocardiography
