DMU physics final

"reverberation with the spaces squeezed out". appears as solid hyperechoic line directed downward. also called ring down artifact

appears as hypoechoic or anechoic region extending downward from very strong attenuating medium. appears when the attenuation is higher in the tissue above the shadow than in surrounding tissue

appears as hypoechoic region extending along the edge of a curved reflector. also called shadowing by refraction

• reverberations
• comet tail
• shadow
• edge shadow
• enhancement
• focal enhancement
• mirror image
• speed error
• lobes
• refraction
• lateral resolution
• axial resolution
• multi path artifacts
• curved and oblique reflectors
• temporal resolution
• spacial resolution
• slice thickness

the bigness of the wave. the difference between maximum value and the average or undisturbed value of an acoustic variable

the number of particular events that occurs in a specific duration of time

higher frequency transducers. only occur with pulsed doppler. when the doppler sampling rate is too low in comparison to the measured blood velocity

1540 m/s

500 m/s

• raise the nyquest limit
• lower frequency transducer
• new view with shallower sample volume
• use continuous wave doppler

• black and white identifies anatomic structures
• color identifies blood flow velocities and function

lower

• lower fequency transducer
• shallow sample volume

when an instrument penetrates the skin or mucous membrane

the amount of contrast harmonics produced

• hydrostatic
• respiration

the interaction of sound waves with microscopic, stabilized gas bubles in tissue

tissue heating is related to the output characteristics of the transducer and the properties of the tissue

39 deg. C

muliple, equally spaced echoes caused by te bouncing of a sound wave between two strong reflectors positioned parallel to the ultrasound beam

also known as comet tail. appears as solid hyperechoic line directed downward

created when sound reflects off of a strong reflector (mirror), and is redirected toward a second structure causing a replica or second copy to appear deeper

off axis sound beams, created by single element transducer, structures within side lobes can generate reflections and degrade lateral resolution

occurs when a sound pulse changes direction during transmission. degrades lateral resolution

• carries energy
• mechanical wave
• cannot travel through vacuum

the bouncing of the sound wave between two strong reflectors positioned parallel to the ultrasoud beam

component of attenuation. occurs when ultrasonic energy is converted into another energy form, such as heat. directly related to frequency

the random redirection of sound in many directions. happens when tissue interface is smaller or equal to the wavelength

the decrease in intinsity, power and amplitude as sound travels through a medium

portion of the sound beam that is redirected when a beam strikes a boundry

weakens the portion of the sound wave that continues forward

when a strong reflector is in the path of the lobe it creates a reflection. the system interprets the reflection as arising from a structure positioned along the beams main axis

• created by array transducers
• deminishes lateral resolution

beneath the structure, hypoechoic or anechoic

• directly related to frequency of the transmitted sound.
• directly related to velocity of blood cells
• created when transmitted sound waves strike red blood cells

artifact appears as a hyperechoic region beneath tissues with abnormally low attenuation. hyperechoic regions are same color as foreground. opposite of shadowing. helps characterize tissue

• with higher frequency transducers
• deep gate
• faster blood velocity

the routing, periodic evaluation of an ultrasound system to guarantee optimal image quality

assesment of system components, repairs, preventive maintenance, record keeping

ultrasonic features similar to soft tissue, more suitable for modern systems, grayscale, tissue texture, multi-focus and adjustable focus

improves lateral resolution by concentrating the sound energy into a narrower beam. external, internal, phased array

• beam diameter in near field and focal zone is reduced
• focal depth is shallower
• beam diameter in the far zone increases
• focal zone is smaller

• period
• frequency
• wavelength
• speed

the number of pulses that an ultrasound system transmits into the body each second

the time from the start of one pulse to the start of the next pulse

the ability of the system to create numerous frames per second

the actual time fromthe start of a pulse to the end of that pulse

the distance that a pulse occupies in space from the start oto the end of a pulse

90

0 or 180

the highest doppler frequency or velocity that can be measured without the appearance of aliasing

enhancement - helps provide valuable information that helps to characterize tissue

shadows - valuable diagnostic info that helps characterize tissue

AKA microprobe. small hypodermic needle with a tiny piece of piezoelectric material attached to its end. measures the characteristics of a sound beam

AKA doppler frequency - a result of relative motion between the sound source and the receiver. away from transducer is negative

magnitude and direction

increased sensitivity to low velocity: unaffected by doppler angles (except 90 deg): no aliasing

• no measurement of velocity
• low frame rates
• susceptible to motion of transducer

• mean velocity measurements
• moderate sensitivity
• provides two dimensional flow info

• subject to aliasing
• reduced temporal resolution

as low as reasonably achievable