Book Flashcards

Question

Acoustic parameters

Answer 1

Describe the features of a particular sound wave

Answer 2

The time required to complete a single cycle

Answer 3

How often are cycle sent out The frequency of a wave is the number cycles of an acoustic variable that occur in one second

Answer 4

Per second Hz

Answer 5

2 MHz - 15 MHz

Answer 6

Better penetration with decreased resolution

Answer 7

Poor penetration with increased resolution

Answer 8

Ultrasound

Answer 9

Infra sound

Answer 10

When one goes up, the other goes down

Answer 11

Higher frequency

Answer 12

Frequency x Period

Answer 13

The difference between the average value and the maximum value of an acoustic variable. The variation of an acoustic variable. Units Pressure- Pascals Density- grams/ cubic cm Particle motion – centimeters, inches, units of distance

Answer 14

The rate of energy transfer Units- watts * Power is proportional to the waves amplitude squared

Answer 15

The concentration of energy in a sound beam Units- watts/ square cm or watts/cm squared

Answer 16

When one goes up, the other goes up

Answer 17

The length or distance of a single cycle and influences image quality (axial resolution) Units- any units of length Determined by both the source and the medium

Answer 18

Wavelength(mm) = prop speed 1.54mm/us divided by frequency (MHz)

Answer 19

In soft tissue, sound with a 1 MHz frequency has a wavelength of 1.54mm In soft tissue, sound with a 2 MHz frequency has a wavelength of 0.77mm

Answer 20

The rate that sound travels through a medium (aka- velocity or speed) Units- meters per second mm/us Determined by medium only (density and stiffness)

Answer 21

All sound travels at the same speed through any specific medium. Cant be changed by sonographer

Answer 22

1,540m/s 1.54km/s 1.54mm/us

Answer 23

Sound in a slow medium has a short wavelength Sound in a fast medium has a long wavelength

Answer 24

Lung(air)<

Answer 25

Stiffness & speed- same direction Density & speed- opposite directions

Answer 26

Same as stiffness When bulk modulus increases, speed increases

Answer 27

In phase waves interfere constructively Out of phase waves interfere destructively

Answer 28

Watts/ cm squared

Answer 29

Continuous wave sound cannot create an atomic images. CW is used for Doppler.

Answer 30

A pulse is a collection of cycles that travel together A pulse must have a beginning and an end, otherwise the sound is continuous wave

Answer 31

Pulse duration Pulse repetition period PRF Duty factor Spatial pulse length

Answer 32

The actual time from the start of a pulse to end of that pulse Units-time, seconds Determined by sound source Changed by sonographer – no Typical values – 0.5 - 3us In clinical Imaging a pulse is comprised of 2 to 4 cycles Equation- pulse duration= number of cycles x period

Answer 33

The distance from the start to the end of one pulse Units/distance, MM Determined by the source and the medium Sonographer cannot change Typical values/0.1 - 1mm Equation - SPL(mm)= # of cycles x wavelength(mm)

Answer 34

Shorter pulses create higher quality images

Answer 35

Pulse repetition period (PR) is the time from the start of one pulse to the start of the next pulse. It includes one pulse duration and one listening time. Determined by Sound source Units - time, msec Changed by sonographer- yes Values- 100us to 1ms

Answer 36

PRF is the # of pulses created by the system in one second. Hertz, Hz, per second Determined By sound source Sonographer can change it Values In clinical imaging, from 1,000-10,000Hz (1-10kHz) » • The PRF is determined by imaging depth only. Shallow image, higher PRF Deep image, lower PRF PRP/ PRF- one goes up, other goes down pulse repetition period (sec) × pulse repetition frequency (Hz) = 1

Answer 37

The percentage or fraction of time that the system transmits sound. Unitless Determined by sound source Can be changed by sonographer Typical values From 0.1% to 1% or 0.001 to 0.01 Shallow image, higher duty factor (little talking, lots of listening) » Deep image, lower duty factor Duty factor is always a small value, typically less than 1%. With deeper imaging, the duty factor is even smaller.» Note An imaging system must use pulsed ultrasound. Therefore, the duty factor always less than 100% Continuous wave sound has a duty factor of 100%. CW cannot create anatomical images.»

Answer 38

deep imaging low pulse repetition frequency (PRF) long pulse repetition period low duty factor

Answer 39

PRP PRF DF All determined by sound source

Answer 40

The concentration of the power in a beam

Answer 41

• Peak the maximum value • Average the mean value • Spatial referring to distance or space • Temporal referring to all time (transmit & receive) •Pulsed referring only to the time the pulse exists (transmit only)

Answer 42

SPTP- spatial peak, temporal peak **highest value SPTA- spatial peak, temporal average **most relevant for thermal bioeffects SATA- spatial average, temporal average **lowest value

Answer 43

SPTA- related to tissue heating SPTP - greatest SATA -smallest

Answer 44

a novel way of rating numbers, a peculiar combination of addition and multiplication. The logarithm of any number represents the number of "1Os" that are multiplied together to create the original number. What is the log of 100? 10 x 10 = 100, the log of 100 is 2. What is the log of 1000? 10 x 10 × 10 = 1000, the log of 1,000 is 3.

Answer 45

A logarithmic scale, a relative, comparison or ratio between the final to the initial strengths A comparison, therefore, two intensities are needed calculate decibels. Db report the of relative bigness of a sound beam

Answer 46

Means getting bigger, the intensity is increasing 3 dB means two times bigger 10 dB means 10 times bigger

Answer 47

Means getting smaller, the intensity is decreasing -3 dB means 1/2 -10 dB means 1/10

Answer 48

A decrease in strength, (intensity, power, and amplitude) have a sound wave as it travels. Unrelated to speed the further sound travels, the more attenuation occurs. Units -dB/must be negative since attenuation causes intensity to decrease Less attenuation = shorter distance/lower frequency More attenuation = longer distance/higher frequency

Answer 49

Absorption/primary sound converted into heat Scattering Reflection / 1%

Answer 50

Air/ much more attenuation, then in soft tissue. Gel is used to remove air from the path of ultrasound. Lung and bone/bone absorbs and reflects. Lung scatters. Water/ much less than soft tissue Air>> bone & lung >> soft tissue>> water Attenuation and blood is less than that in soft tissue

Answer 51

In soft tissue, lower, frequency results in less attenuation. Thus we penetrate further with lower frequency sound.

Answer 52

Occurs when propagating sound energy, strikes a boundary between two media, and some returns to the transducer

Answer 53

Occurs when the wave length is smaller than the irregularities in the boundary Strongest reflections are produced with normal incidence 90° These aren’t as well seen when the wave strikes the boundary at angles other than 90°. Example vessel wall.

Answer 54

The reflection of sound generally back towards the transducer, but in a number of directions When boundary is rough, reflected, sound is disorganized and random

Answer 55

The distribution of sound randomly in all directions. Higher frequency, sound scatters to a great extent. **If a reflector is much smaller than the wave length of sound, sound is uniformly distributed in all directions

Answer 56

As frequency increases, scattering increases Blood is black due to Rayleigh scattering

Answer 57

The amount of attenuation per centimeter. A way to report attenuation without dealing with how far sound travels. Units- dB, dB per centimeters As frequency increases, the attenuation coefficient increases Remains the same, regardless of how far the sound waves travel Attenuation coefficient is half of the frequency

Answer 58

A number associated with a medium. *It is Calculated not measured. Units- Rayls, Z Reflection of an ultrasound wave depends upon different acoustic impedances of the media on either side of the boundary *Equation- impedance (rayls) = density (kg/m3) X propagation speed (m/s)

Answer 59

Frequency If frequency, doubles, attenuation coefficient, will double

Answer 60

Frequency If frequency, doubles Rayleigh scattering increases by a factor of 16 2x2x2x2=16

Answer 61

Perpendicular Orthogonal Right angle 90° PORNN

Answer 62

Anything other than 90°/not at right angles

Answer 63

Incident intensity- intensity of a sound wave prior to striking a boundary (100%) Reflected intensity -the intensity that after striking a boundary changes direction, and returns back from where it came from (less than 1% reflected) Transmitted intensity - the intensity that after striking a boundary continues on in the same direction that it was originally traveling (99%) Units W/CMsquared Incident= reflected + transmitted

Answer 64

IRC/ intensity reflection coefficient- the percentage of the ultrasound intensity that bounces back when sound strikes a boundary ITC/ intensity transmission coefficient- the percentage of the incident intensity that after striking a boundary continues on the same direction that it was originally traveling No units, percentages Both are unitless Range from 0% to 100% or 0 to 1.0

Answer 65

Exists at a boundary

Answer 66

Boundary. Reflection % Soft tissue -air. 99% Soft tissue -bone. 50% Soft tissue- soft tissue. <1%

Answer 67

**Reflection occurs only if the two media at the boundary have different acoustic impedances Intensity Reflection Coefficient (%) = Z2-Z1/Z2+Z1 squared With greater impedance differences between the two media, the IRC increases and the amount of reflection increases. Z= impedance

Answer 68

Whatever is not reflected, must be transmit it

Answer 69

Transmission and reflection may or may not occur with oblique incidence

Answer 70

Transmission with a band. Refraction is a change in direction at sound transmits from one medium to another. Requires both oblique incidents and different speeds Snells law describes the physics of refraction Sin(transmission angle) —— divided by——- Sin (incident angle) = Propagation, speed 2 ——-divided by———- Propagation, speed one

Answer 71

Smaller angle = slower medium Greater angle = faster medium

Answer 72

The time needed for a post to travel to and from the transducer, and the reflector is called time of flight or round-trip time What time of flight is measured we can determine reflector Depth Since the average speed of sound in soft tissue is 1.54 KM/SEC the time of flight and distance that sound travels in the body are directly related. Time of flight flight is increased by a factor of two. When one reflector is twice as deep as another pulses timer fly is doubled for the deeper reflector.

Answer 73

In soft tissue, every 13 µs of go return time means the reflector is 1 cm deeper in the body. Time of flight/Depth/ Distance trvld 13 µs 1 cm. 2 cm. 26 µs 2 cm 4cm

Answer 74

Speed= distance/ time

Answer 75

A property of certain materials to create a voltage when pressure is applied, or when the material is mechanically deformed

Answer 76

Synthetic- lead zirconate (PZT) aka/ ferroelectric material. Natural- quartz, tourmaline PZT ceramic Active element Crystal

Answer 77

When PZT is heated above the temperature (approx 360°C or 680°F) its properties are destroyed, depolarized. Never heat sterilize or auto clave transducers

Answer 78

The complete destruction of all living microorganisms by means of exposure to heat, chemical agents, or radiation

Answer 79

The application of a chemical agent to reduce or eliminate infectious organisms.

Answer 80

Wire, case, backing material, crystal, matching layer Active element- Piezoelectric crystal, also called ceramic, PZT or crystal It is 1/2 wave length thick

Answer 81

The matching layer has an impedance between those of the skin and active element to increase transmission between the active element and the skin 1/4 wave length thick Impedances - PZT> Matching layer> gel> skin Going from the PZT crystal to the face of the probe, the impedance of each layer is less than less

Answer 82

Short pulses, create more accurate images Immaterial is bond it to the active element to reduce it’s ringing Z= impedance

Answer 83

The range of frequencies between the highest, and the lowest frequency emitted from the transducer Bandwidth (Hz)= highest frequency-lowest frequency Imaging probes are wide bandwidth or broadband because they use backing material Main frequency emitted is called the center, resonant, primary or natural frequency

Answer 84

A Unitless number related to extent of damping Low Q= damping, and wide bandwidth, Imaging transducers High Q= no damping and narrow bandwidth, CW and therapeutic transducers

Answer 85

Electrical frequency >>> sounds frequency

Answer 86

The main frequency of sound from a pulse transducer is determined by two characteristics of the Crystal: 1) the thickness 2) propagation speed The propagation speed of PZT is approximately 4-6 mm/us When a PZT crystal is half as thick that sounds frequency is twice as high High frequency // Lower frequency Thin Crystal. Thick Crystal. Fast, PZT Slow, PZT Component // Thickness PZT crystal 1/2 wavelength thick Matching layer 1/4 wavelength thick

Answer 87

Talcum powder

Answer 88

Narrow beams create better images Starts out at exactly the same size as the transducer diameter or aperture Focus or focal point - the location where the beam reaches its minimum diameter Focal depth -the distance from the transducer to the focus. Also called focal length or near zone length. Near zone (Fresnel zone)-the zone in between the transducer and the focus. Sound beams coverage in the near zone. Far zone (Fraunhofer zone)-zone deeper than the focus, beyond the near field . Sound beams diverge in the far zone. Focal zone -the region surrounding the focus where the beam is sort of narrow and the picture is relatively good

Answer 89

See picture

Answer 90

Distance from transducer to the focal point Determined by transducer diameter, or aperture and frequency Shallow Focus.- small diameter/low frequency Deep focus - large diameter/high frequency

Answer 91

Describe the spread of the sound beam in the deep far zone Larger diameter, crystals, producing higher frequency, sound produced beams that diverge less in the far Field Smaller diameter crystals, producing lower frequency sound produced beams that diverge substantially in the far field

Answer 92

V- shaped wave, also called Huygens wavelet

Answer 93

The hourglass shape of an imaging transducers sound beam The overall hourglass shape of a sound beam is the result of the constructive and destructive interference of the mini sound wave. Let’s omit it from these numerous sound sources.

Answer 94

The ability to distinguish two structures that are close to each other, front to back or along the beams main axis Units/ distance , mm cm Not changed by sonographer Short pulse means a short, spatial pulse length or a short pulse duration Images are more accurate with shorter pulses Typical values 0.05 - 0.5 mm Equation - Axial resolution (mm)= SPL(mm)/2

Answer 95

Less ringing(if you are cycles in a pulse) and higher frequency Higher frequency, transducers create more accurate images. As frequency increases, the numerical value of the axial resolution decreases.

Answer 96

The minimum distance that two structures are separated by side to side or perpendicular to the sound beam Units - distance mm Lateral resolution = being diameter Beam diameter, and lateral resolution varies with depth. Also called beam width variation, or point spread artifact Best at the focus or one near zone length from the transducer Degrades at deeper depths in the far zone

Answer 97

Improved axial resolution Improved lateral resolution in far field

Answer 98

Adjustable or multi focusing Better overall lateral resolution Sonographer can move the focus to anatomic region

Answer 99

Narrow waist in the beam Shallower focus Smaller focal zone Focusing is effective, mainly in the near field and focal zone

Answer 100

Fixed- conventional or mechanical Adjustable by electronics called phased array

Answer 101

One disc shaped element Active element mood by a motor, oscillating crystal or mirror Focusing/conventional or fixed Image shape/sector (fan) Defective, crystal/destroys entire image

Answer 102

A collection of active elements in a single transducer PZT cut into separate pieces called elements Combination of electronic circuitry, the wire, and the element Linear array/a collection of elements in a line. Linear switched (or sequential) and linear phase array Annular array/a group of ringed elements (bull’s-eye) with a common center Curvilinear array/elements arranged in an arc. Curvilinear, switched, or curvilinear phased.

Answer 103

Approximately 200 rectangular shaped elements 3 -10 but not all are fired at exactly the same time to create a narrow directional beam. Improving lateral resolution. No steering Parallel lines / rectangular shaped Defective crystal/drop out, extending from superficial to deep

Answer 104

Adjustable, focus or multi focus electronically Approximately 200 rectangular shaped elements Electronic pulses delivered to mini or all elements and various patterns for each sound pulse. Sector shaped Time delays are called phase delays If one element malfunctions the staring and focusing become erratic Curvature pattern can change focal depth and amount of focusing The beam former creates the electronic patterns. 10 ns delays. Provides many focusing at many depths during reception

Answer 105

Rings, cut from the same circular slab a PZT. Looks like a bull’s-eye target. Small number of ring-shaped elements Selected focal zones. Inner crystals for shallow regions and outer crystals for deep regions. Small diameter rings, have a shallow focus, but divert rapidly Large diameter rings, have a deep focal length The image is pointed, fan, or sector shaped Multi focusing provides electronic, focusing and all planes at all depths Improved elevational resolution Steering is mechanically Defective, crystal/horizontal side to side drop out

Answer 106

PZT crystals arranged in a curve to provide a natural sector image Approximately 200 rectangular shaped elements Blunted sector, fan shaped image

Answer 107

2D arrays create 3D or 4D images 3D imaging more accurately measure is volumes of structures, such as cysts 4D Imaging is real time 3D imaging 3D Imaging quality is determined by the number of slices 3D Imaging provides more accurate value measurements

Answer 108

Combined linear sequential and linear phased array technologies Trapezoidal shape / sector with a flat top Sector scanners are less useful when imaging superficial structures

Answer 109

Dynamic range Visualizing variety of gray shades in an image

Answer 110

Detail Affected by axial and lateral resolution, line density, and monitor

Answer 111

The ability to accurately locate moving structures are any particular incident in time Resolution pertaining to time **Depends only on frame rate. More images per second improves temporal resolution. Units / Hertz or per second Values / 20Hz - 100 Hz **Frame rate is determined by Imaging, depth and number of pulses **Limited by speed of sound, and imaging depth

Answer 112

Better temporal resolution

Answer 113

Lower frame rate

Answer 114

Sonographer controlled Maxximum Imaging depth Multi focus systems Sector size Line density

Answer 115

When image is shallower or made of fewer pulses Less time to create an image More frames created each second

Answer 116

When image is deeper or made of more pulses More time to create an image Frame rate decreases

Answer 117

Shallow depth of you makes a frame faster and improves temporal resolution If Imaging depth is doubled, the frame rate will be halved

Answer 118

Shallow Imaging Higher frame rate Better temporal resolution Deep Imaging Lower frame rate Worse temporal resolution

Answer 119

Single focus- fewer pulses Higher frame rate Better temporal resolution Multi focus - more pulses Lower frame rate Worst temporal resolution

Answer 120

Narrow sector- fewer pulses Higher frame rate Better temporal resolution Wide sector - more pulses Lower frame rate Worst temporal resolution

Answer 121

Low line density- fewer pulses Higher frame rate Better temporal resolution High line density - more pulses Lower frame rate Worst temporal resolution

Answer 122

Factors that shorten the time required to make each frame increase frame rate and improve temporal resolution Factors that lengthen the time required to make a frame will reduce frame rate and reduce temporal resolution

Answer 123

As temporal resolution improves (higher frame rate) image quality made degrade As temporal resolution degrades (lower frame rate) image quality may improve Increasing the line density degrades, temporal resolution, but improves spatial resolution Using multi focus, degrades temporal resolution by improves lateral resolution

Answer 124

Tf and frame rate are reciprocals Equation - Tf x FR = 1 Ex- 1/10th x 10 = 1 When one frame is created in 1/10 of a second, then the frame rate will be 10/second or 10 HZ

Answer 125

Master synchronizer/organizes, synchronizes and times their functions so as to operate as a single integrated system Pulser/ controls the electrical signals sent to the elements. Creates the firing pattern for phased array system called being former. Transducer/converts electrical into acoustic energy during transmission Receiver/ the electronics associated with processing the electronic signal, produced by the transducer during reception, and producing a picture on display device Display/monitor, audio speakers Storage/computer memory, hard drives

Answer 126

Receives timing signal from synchronizer. Produces electrical voltage up to 100 V that excites PZT Crystal during transmission. When the sonographer increases output power higher electrical voltages are created that strike the PZT crystals. This increases the sound intensity, created by the transducer and sent into the patient.

Answer 127

Continuous wave/ continuous electrical signal Electrical frequency = sounds frequency Pulsed wave, single Crystal /short, duration, electrical, spike, one electrical spike per Ultrasound pulse Pulsed wave, arrays/mini elements fired for each ultrasound pulse. For phased array systems, the pulsar is also called the beam former.

Answer 128

Output power change the brightness of the entire image Signal-to-noise ratio changes Determined by the excitation voltage from the pulser PZT crystal vibrates with a magnitude related to pulser voltage Sonographer can change Brightness of the entire image changes

Answer 129

High S/N ratio- high quality image Low S/N ratio- low quality image, degrades Increasing output power is the primary way to improve S/N ratio

Answer 130

Gain, TGC, dynamic range, reject Or Amplification Compensation Compression Rejection

Answer 131

Changes the brightness of the entire image. S/N ratio unchanged Adjusted by sonographer Units dB Every signal is treated identically (uniform amplification) Preamplification alters the signal before gain is applied. Usually performed in the probe Gain kill’s resolution

Answer 132

Used to create uniform brightness Makes all echoes from similar reflectors appear identical regardless of depth Uniform from top to bottom Higher frequency = more TGC Lower frequency = less TGC

Answer 133

Adjusts the grayscale range within the image Allows us to see all gray shades and differentiate tissues Changes the gray scale mapping Sonographers can adjust

Answer 134

Illuminates, low level noise in our images Affects only low level signals everywhere on the image, but does not affect bright echoes. Fewer shades of gray. Sonographer can adjust

Answer 135

Micro bubbles of gas entrapped in a shell There is a large impedance difference between contrast agents and biologic tissues

Answer 136

Safe Strong, reflector ultrasound Long persistence Metabolically inert

Answer 137

Adjustments to either output power, or gain alter the brightness of the entire image Output power affects patient exposure Gain doesn’t affect patient exposure Output power affects brightness, by adjusting the strength of the sound waves sent to the body from the transducer When the image is too bright due to high output power, the lateral and longitudinal resolution degrade Gain affects the brightness by changing the amplification of the electronic signals before returning to the receiver With increased gain, the electronic signals in the receiver, are boost it in the image will be brighter

Answer 138

As low as reasonably achievable

Answer 139

To image deep, it is better to use a low frequency, transducer rather than increase output power

Answer 140

Harmonics are multiples of the transducer frequency Creates ULTRASOUND images by using reflections that are twice the transmit frequency. Harmonics are created in the tissues, not in the transducer Nonlinear behavior creates harmonics Nonlinear is uneven Sound moves slightly faster in regions of compression (higher pressure) Sound travel, slightly slower in regions of rarefaction. (lower pressure.)

Answer 141

The major disadvantage is that the frame rate is half that a fundamental imaging. Pulse inversion, imaging degrades, temporal resolution (lower frame rate) well improving spatial resolution (image detail) Transducer bandwidth must include transmit and harmonic frequencies

Answer 142

Bistable: black or white On or off High contrast * Narrow dynamic range * Poor contrast resolution Grayscale : Many shades of gray Multiple levels Low contrast Wide dynamic range Good contrast resolution

Answer 143

Related to the brilliance of the image, how ‘lit up’ is the image

Answer 144

Determines the range of brilliance is that are displayed. Are the whites white? Are the blacks black? Bistable images are high contrast

Answer 145

Analog: Real world/a variable obtains, a continuum of values Ex- actual weight of an individual Digital: Computer world/a variable attains only discrete values Ex- measuring weight on a digital scale

Answer 146

Changes the data format from penetrations to horizontal lines of a display

Answer 147

RAM Random Access Memory

Answer 148

A microprocessor digitizes images. This converts the image into zeros and ones which are stored in memory. The numbers (*digital image data) can be processed and then re converted for display as an image

Answer 149

The smallest element of a digital picture ** Pixel density- the more pixels per inch, the more detail in the image, spatial or detail resolution ** Low pixel density/ poor spatial resolution High pixel density/ good spatial resolution *spatial resolution on a digital display is determined by the pixel density (the # of pixels per inch) * spatial resolution is also related to the # of lines per frame

Answer 150

*Binary digit, the smallest amount of digital storage *a bit is a bistable, having a value of either zero or one *a group of bits is assigned to each pixel to store the gray scale color assigned to that pixel *the more bits per pixel the more shades of gray, and the better the contrast resolution Binary number- group of bits. A series of zeroes and ones Digital (computer based) means binary Ex- 101 or 00110011 *Byte- a group of 8 bits is a byte. 2 bytes (16bits) is a word Ex- Byte 12345678 Word 12345678 12345678 Note- Binary numbers are based on 2 Decimal numbers are based on 10 *

Answer 151

How many bits are assigned to each pixel. Multiply the number 2 by itself the same number of times as there are bits. Thats the answer. Ex- what # of shades that can be represented by 10 bits? 2x2x2x2x2x2x2x2x2x2= 1024 Or 2 to the 10th power So the largest # of shades represented by 10 bits is 1024 Note- digital means binary, not decimal Examples pg 106

Answer 152

Manipulating the data before storage in the scan converter. Preprocessing cannot be reversed TGC Dynamic range Write magnification Fill in interpolation Persistence / frame averaging Special compounding

Answer 153

Manipulating the data after it has been stored in the skin, converter memory, but prior to display. This can be undone * post processing is performed on frozen images Read magnification 3-D rendering

Answer 154

Analog / real world that we live in is analog Digital/ computers is digital Analog to digital conversion/electrical signals, created by the PZT are analog However, a digital scan converter can only process computer information. The analog signal must be converted into digital form for the input into the scan converter this is done by analog to digital converter

Answer 155

Read magnification- Post processing Does not rescan, only reads old image data in memory Same line density Larger pixels Spatial resolution not improved Temporal resolution unchanged Write magnification - Preprocessing Rescans and requires new data, discard old image data Increased line density More pixels Improved spatial resolution * Temporal resolution can change **If pixel size is unchanged, the number of pixels increase (write magnification) If number of pixels is unchanged, pixel, size increases (read magnification)

Answer 156

Imaging artifact *Grainy appearance and tissues, that does not represent actual tissue anatomy * created by interference effects of scattered sound Spackle reduces image contrast, and spatial resolution

Answer 157

Doppler artifact With Doppler blood velocity measurements, the reflection from blood cells are weak. Reflections from anatomic structures are much stronger. These strong reflections are called clutter.

Answer 158

Preprocessing Improves image detail (spatial resolution) by filling in the missing data, especially for deeper parts of a sector shaped image. Example/edges of a circular structure will be better defined

Answer 159

Creating an image by averaging images obtained from different angles. Scan lines are steered by the system in different angles or views Phased array transducers only Frames are averaged, improving signal to noise ratio -artifacts reduced -spatial resolution (detail) improved -temporal resolution (frame rate) reduced - shadows and edge shadows are reduced or eliminated

Answer 160

Creating an image by overlaying images obtained at different times Also called temporal averaging Used in color flow Doppler Resulting image is a consolidation of past frames Temporal resolution is decreased Moving anatomic structures appear blurred Improves dynamic range, and contrast resolution

Answer 161

Creating an image by averaging frames obtained from different frequency sub-bands. Images are averaged, improving signal-to-noise ratio *Spackle artifact is reduced Spatial resolution is improved

Answer 162

Improves lateral resolution *A form of electronic receive focusing *Accomplished, by varying the number of elements used to receive the reflected signal Minimizes beam width variation

Answer 163

Increases the contrast at a boundary to make image appear sharper Most useful to emphasize different tissues Distinguish interfaces

Answer 164

Takes place in the pulser Improves : Axial resolution Penetration Spatial resolution Contrast resolution coded excitation creates long sound pulses that contain a complex pattern of frequencies and cycles, called a code. Special mathematical techniques process the long reflected codes, creating high quality images

Answer 165

a dynamic technique that produces images, called elastograms, based on the deformation (change in shape) when an force is applied to tissue. The force is exerted a sound pulse from the transducer. Tissue stiffness is often related to underlying disease. identifies tissues of different mechanical properties, or different stuffiness

Answer 166

Ratio* of the largest to the smallest signal strength that each component processes, the number of choices indicates the number of gray shades on an image. Can eliminate low level noise* Units - dB* Transducers process using the widest dynamic range. Recoding device date has the lowest dynamic range

Answer 167

PACS- Picture archiving and communications system DICOM- Digital imaging and communications in medicine NAS- Network attached storage

Answer 168

Steady, pulsatile & phasic flow Steady flow- fluid moving at a constant speed Pulsatile- Arterial Cardiac High rate Higher pressure Phasic- Venous Respiration Low rate Lower pressure

Answer 169

Flow- Volume How much? Volume/ time Liters/ min Velocity- Speed How fast? Distance/ time Meters/ sec

Answer 170

Plug or parabolic Plug flow Layers travel at same speed Parabolic flow Layers travel at individual speeds, highest in the center of the lumen

Answer 171

Chaotic flow in many directions and speeds Associated with cardiovascular pathology and increased velocities (ex stenosis) *Turbulence may be identified as doppler spectral broadening Vortex- swirling pattern Eddy currents- turbulent flow

Answer 172

A unitless number, indicating whether flow is laminar or turbulent Reynolds #. Flow Less than 1500 Laminar Between 1500 and 2000 ???? Greater than 2000 Turbulent

Answer 173

Law of conservation of energy Describes the relationship between pressure (potential energy,) and flow (kinetic energy)

Answer 174

a change or difference in the frequency of sound as a result of motion between the sound source and the receiver. Greater velocities create greater Doppler shifts. *difference between received and transmitted frequencies» positive/ change (or shift) when source and receiver are approaching each other. Reflected frequency is higher than transmitted.* negative/ change when the source and receiver are moving apart. Reflected frequency is less than transmitted frequency. *doppler measures frequency shift not amplitude Units- Hertz, cycles per second Values- * 20 Hz - 20kHz *audible Created when sound reflects off of moving red blood cells We still use 2 MHz to 10 MHz transducers to perform a Doppler ultrasound study. but the change in frequency (Doppler shift) ranges from 20-20,000 Hz.• Demodulation extracts the Doppler frequency from the transducer frequency and is performed by a demodulator. Bidirectional Doppler is analyzed with phase quadrature processing. Doppler shift = received frequency - transmitted frequency

Answer 175

Doppler shift = 2 x reflector speed x incident frequency x cos (angle) —— Divided by ——— Propagation speed *** in order to accurately determine velocity, the angle between the directions of flow and sound beam must be known

Answer 176

Blood cell speed Transducer frequency Cosine of the angle between flow and the sound beam

Answer 177

The speed of sound in the medium

Answer 178

In clinical Doppler, there is a double Doppler shift. The first occurs when the sound strikes the blood cell. The second shift results from sound wave, reflecting off of the moving blood cell and returning back to the transducer.

Answer 179

*Doppler measures velocity not speed Speed/ magnitude only Velocity/magnitude and direction * Doppler frequency depends on direction. The magnitude of shift depends upon the cosine of the angle between the sound being in the direction of motion. You need to know the angle to accurately evaluates velocity Equation - Velocity (measured)= True velocity x cos (angle) Angle Cosine 0° 1 (100% of the info parallel) 60° 0.5 90° 0 Maximum doppler shift at 0° No Doppler shift at 90°

Answer 180

Two crystals in the transducer > one crystal is continuously transmitting > the other is continuously receiving Advantage/high velocity is our accurately measured.* Disadvantage/echoes arise from entire length of overlap between the transmit and receive beams called range ambiguity (doesn’t focus on specific area.) Range means depth CW can be thought of as a ‘Jet Sniffer’

Answer 181

One Crystal, alternates between sending, and receiving * Echoes arise only from the area of interrogation, the sample volume or gate. We locate the gate.(center of the lumen, parallel to vessel walls.)* Disadvantage/aliasing, errors in measuring high velocities And imaging and pulse Doppler can be performed with a single Crystal transducer Simultaneous Imaging and Doppler is known as duplex, ultrasound Axes- >the horizontal axis (or X axis, side to side) of a doppler spectrum is time. > the vertical axis (or Y axis, up and down) of a Doppler spectrum is Doppler shift or velocity.

Answer 182

High velocities appear negative. With pulse Doppler, high velocity, measurements are inaccurate if the pulsed doppler sampling rate, the PRF, is too low in comparison to measured Doppler shift. Aliasing grows from top or bottom, never from the baseline Wrap around aliasing / with extremely high velocities High frequency transducers tend to show aliasing

Answer 183

The doppler frequency at which aliasing occurs, equal to half the PRF Equation- Nyquist limit (kHz) = PRF/2

Answer 184

1) use CW doppler (CW has no aliasing) 2) use a lower frequency transducer/ it reduces the doppler shift & shrink the spectrum 3) select new view with shallower sample volume (this increases PRF & nyquist limit) 4) increase the scale 5) baseline shift (move baseline) *when the transducer frequency is halved, the measured doppler shift is halved *the calculated velocity will be the same regardless of the transducer’s frequency perform doppler at angles closer to 90°

Answer 185

Smaller sample volumes create doppler spectra with cleaner spectra window Larger sample volumes create Doppler spectra with filled in spectra (spectral broadening)

Answer 186

Amplitude or strength of the reflected signal Or Concentration of blood cells creating the reflection

Answer 187

Pg 124 See picture chart

Answer 188

Range resolution, or specificity* Aliasing *

Answer 189

Flow direction

Answer 190

Color flow measures mean velocities (average) Pulsed and CW space Doppler measures. Peak velocity is.

Answer 191

Top color/ always flow toward or closer to the transducer Bottom color/ always flow away from the transducer Velocity mode/colors on map do not vary side to side Variance mode/ colors on map very side to side

Answer 192

The vessel is without color due to 90° incidence between sound being and flow The cosine of 90° zero

Answer 193

For a sector shaped image, look at the map. The flow direction is always from the top color to the bottom color. What is the vertical black line in the center of the vessel on a sector image? No Doppler shift because a normal incidence

Answer 194

Velocity mode/ colors show information on flow direction Variance mode/ colors show information on flow direction AND the presence or absence of turbulence Left side-laminar or parabolic (normal) Right side-turbulent or disturbed (pathology)

Answer 195

Multiple pulses are called a packet, or ensemble length Small packets- Less accurate doppler Less sensitive to slow velocity or low flow High frame rate, improved temporal resolution Large packet- More accurate doppler More sensitive to fast velocity or flow Lower frame rate, reduced temporal resolution Advantages- Greater accuracy of velocity measurements Sensitivity to low flows Disadvantages- More time to acquire information Frame rate and temporal resolution are reduced The packet size must balance between accurate velocity measurements and temporal resolution Color doppler measures mean velocity ** color flow measures mean velocity **pulsed and CW measures peak velocity

Answer 196

Energy mode, color angio Direction and velocity are not calculated. Any measured doppler shift is simply colorized without consideration of direction or speed Advantages- *increased sensitivity to slow flows (venous flow, small and deeper vessels) *angle independent, not affected by doppler angles, unless the angle= 90° no aliasing Limitations- *low frame rates, poor temporal resolution No information on velocity or direction

Answer 197

CW doppler- identifies highest velocity anywhere along length of ultrasound beam PW doppler- accurately identifies the location of flow (range resolution) Has good temporal resolution. Color flow doppler- provides 2-D flow information directly on anatomic image. Power mode doppler- greatest sensitivity. Allows the use of color with low velocities or small volumes of blood flow

Answer 198

Spectral analysis is performed to extract or identify the individual frequencies making up the complex signal. It is used to interpret individual velocities in the signal. *Techniques: Pulsed and CW doppler= fast fourier transform (FFT) Color flow- autocorrelation or correlation function *both FFT and autocorrelation are digital techniques that are performed by computers * Autocorrelation used for color doppler -determines average velocities -used for variance mode (pg128)

Answer 199

*Also known as high pass filter Wall filters serve as a reject for doppler. Removed low level doppler shifts around the baseline. *rejects clutter Increasing scale will eliminate clutter *Wall filter may eliminate end diastolic flows from the spectral display, since they are the lowest velocities

Answer 200

Found in spectral doppler only “Mirror image” Causes- Doppler gain set too high Incident angle near 90 degrees when flow is at focus

Answer 201

Pulsed wave Doppler has a receive gate that is adjusted by the sonographer.

Answer 202

Tissues that appear brighter than normal “Brighter”

Answer 203

Tissues that appear less bright than normal

Answer 204

Without echoes

Answer 205

Equal echo brightness

Answer 206

Similar echos

Answer 207

Different echos within the image

Answer 208

Reverberations- Multiple equally spaced Parallel to the sound beam Appears like a ladder Created when ultrasound ping-pongs between reflectors Comet tail or ring down - Single, solid, hyperechoic line Parallel to sound beam Shadowing - Shadow is background color (too few reflections on the scan) Too much attenuation Hypoechoic or anechoic region beneath Absence of true anatomy on scan in the region of the shadow Parallel to sound beam Edge shadow or shadowing by refraction - Eliminated by spatial compounding * Hypoechoic color Often along the edge of a curved reflector Enhancement - Results from too little attenuation in the structure above the artifact Hyperechoic Mirror image - Extra reflections on the skin Artifact located deeper than the true reflector

Answer 209

*Speed errors appear as a step off, split, or cut When speed is faster than soft tissue / reflector beneath will be placed to shallow on the display When speed is slower than soft tissue/ reflector beneath will be placed too deep on the display Fat/ sound travel slower than 1540 ms in fat. Reflectors beneath that may be placed too deep on the display.

Answer 210

Cannot identify refraction artifact from true anatomy with a single static image -Artifact appear side-by-side with the true anatomic structure -Sound can change direction or bend while transmitting -Occurs with oblique, incidence and different speeds Degrades lateral resolution

Answer 211

-Artifact appearance, side-by-side with the true anatomic structure -occurs when reflections arise from off axis sound * mechanical transducers create side lobes * array transducers create grading lobes * grating lobes can be reduced by dividing each element into even smaller pieces. This is called subdicing. Grading lobes are further reduced by exciting the sub diced elements with different voltages. Center of the sound beam are excited with high voltages and outer most further away from the center. Excited with low voltage is. This is called apodization, which reduces lobes. * lobe artifacts, degrade lateral resolution With lobe artifact, the assumption that reflections arise from the beams, main axis are violated

Answer 212

Slice thickness, artifact occurs when beam has a greater width than the reflector This is called elevational resolution Phil and I have an anatomic structure is called partial, volume artifact, or section thickness, artifact *Generally, linear array transducers, have poor, elevational resolution

Answer 213

*Grainy appearance * created by interference effects of the scattered sound

Answer 214

Created by reflection from structure, located deeper than the maximum imaging depth Fixed by changing depth

Answer 215

Tests flow Used to assess the accuracy of pulsed, continuous wave and color flow systems Vibrating string and moving belt phantoms maybe used to evaluate dollar systems

Answer 216

When adjustments make changes in display or echo brightness from scarcely visible to fully saturated, sensitivity is being assessed

Answer 217

SDMS/society of diagnostic medical sonographer’s -Assists in acquisition of data * acquires, and reviews data OSHA / occupational safety, and health administration -Regulatory agency * regulates

Answer 218

Hydrophone/a small needle with a Piezoelectric crystal at the end. Measures the pressure in a sound beam. Calorimeter/a transducer that turns acoustic energy into heat Thermocouple/ a small device and better in absorbing material. The intensity at specific locations are measured. ** the exam duration is the greatest way to decrease exposure

Answer 219

In VIVO- in the natural setting In vitro- anything else; literal meaning in glass Difficult to study in vivo(living tissues) due to absorption, scattering, and reflection

Answer 220

The science of identifying, and measuring those characteristics of an ultrasound field, which are especially relevant to its potential for producing biological affects

Answer 221

American Institute of Ultrasound in medicine Evaluates science

Answer 222

Food and drug administration Regulates

Answer 223

SPTA 100mW/cm squared unfocused 1,000mW/cm squared focused

Answer 224

Mechanistic approach/ Identify “cause-effect” relationship Empirical approach/ Identify “exposure-response”. relationship

Answer 225

Tissues/bone is an absorber Fetal tissues/fetal soft tissues adjacent to bone are of great concern/greater harm than adults SPTA/related to tissue heating Any exam that causes the temperature elevation two greater than 41°C is considered potentially harmful to a fetus Thermal index is a number proposed in the most recent AIU, and guidelines that relates to tissue Heating

Answer 226

Gaseous nuclei/ microbubbles Mechanical index/a number proposed in the a RUM guidelines that relates to cavitation Higher with peak rarefaction pressure and lower frequency sound. -Micro bubbles get bigger during the rarefactions -cavitation is more likely to occur in lung than other tissues Equation- *MI=peak rarefaction pressure/freq

Answer 227

Bubbles intercept, redirect and absorb acoustic energy. Effects *shear stresses & microstreaming in surrounding fluids

Answer 228

Bubbles expand during rare factions, and the bubbles burst TIN- Transient Inertial Normal Threshold is 10% greater than stable cavitation Highly localized violent effects/ Enormous pressures/mechanical stress Colossal temperatures /thousands of degrees

Answer 229

Population studies/large number of patients, clinical studies, ultrasounds ***Best study is perspective and randomized ** Limitations Often retrospective Ambiguities Other risk factors, such as age nutrition Etc Potential benefits should outweigh the risks AIUM suggests/ Don’t perform studies without reason Don’t prolong studies Minimize exposure ALARA principal - use minimum output, power, and highest game