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EXAM 3 PREP
Physics
| Question | Answer |
|---|---|
| What is the function of the automatic Time Gain Compensation (TGC) circuit in an ultrasound imaging system? | Amplify echo signals from deeper tissues more than echo signals from shallower tissues |
| What is the best signal-to-noise ratio (SNR)? | High value for the signal and low value for the noise |
| When evaluating Analog-to-Digital converters, which "bit depth" provides the best digital depiction of variations within the analog signal? | 8-bit |
| Which term describes the range between the weakest to the strongest electrical signal that an electrical component can effectively process? | Dynamic Range |
| What is being compensated for when a sonographer adjusts the slide bar gain controls on an imaging system? | Attenuation |
| The slide bar gain controls (TGC Controls) provide selective control of what receiver function? | Gain at a specific image depth |
| For array transducers, which component of the ultrasound imaging system controls the sound beam's creation, scanning direction, and focusing? | Beam former (pulser or transmitter) |
| Which term describes unwanted electrical signals that can interfere with the proper display of image data in a scanning system? | Noise |
| Which component of a pulse-echo imaging system initially processes the returning echo signals from the transducer for eventual display on an image monitor? | Receiver |
| What is the purpose of the "reject function" in modern scanning systems? | Eliminate electronic noise |
| What is the function of the Analog-to-Digital (A/D) converter in an ultrasonic imaging system? | Convert the analog signals into digital signals |
| Which is a disadvantage of digital electronic systems when compared to analog systems? | Inability to provide continuous representation of electrical signal levels |
| How do digital electronic devices represent electrical signals? | In discrete levels, with fixed steps between the levels |
| What is the result when the Nyquist Criteria is not met as far as the sampling of an electrical signal is concerned analog to digital conversion? | Aliasing |
| What digital signal processing technique enables electronic components in a scanning system to work with signals that have a large dynamic range? | Compression |
| What is the ability to of a gray-scale image to distinguish echoes of slightly different intensities? | Contrast Resolution |
| "Colorizing" a gray scale image can improve what visual parameter of the human eye? | Dynamic Range |
| What effect does a wider sector size have on frame rate? | Decrease |
| Contrast resolution is improved by? | Increasing bits per pixel |
| If the PRF is 8 kHz, what Doopler shifts will cause aliasing? | 6 kHz |
| Which component of a modern scanning system utilizes complicated pulse sequencing and phase (time) delays to influence the sound beam in the transmit and in the receive modes? | Beam former (pulse or transmitter) |
| Where is time gain compensation accomplished? | Receiver |
| With modern scanning systems, what is the effect on transmit power when the beam is focused at a shallow depth? | It decreases |
| What type of images did the first analog scan converters produce? | Bi-stable |
| What information is shown on the vertical axis of an M-Mode display? What information is shown on the horizontal axis of an M-Mode display? | Depth- time |
| Why must the scan converter convert the incoming image acquisition data format into another type of data format before the data is displayed on a monitor? | For proper display of the data on the image monitor |
| Which component of a pulse-echo imaging system initially processes the returning echo signals for eventual display on an image monitor? | Receiver |
| What is an example of post processing? | B-color |
| An increase in penetration requires what change in the PRF? | Decrease |
| The pulse repetition frequency is determined by? | Number of foci, liners per frame, and frame rate |
| Increasing the ? gain increases the SNR. | Transmit |
| Increasing the ? gain may affect the apparent SNR, but not the true SNR. | Receiver |
| The five functions of the receiver. | Compensation, Demodulation, Compression, Rejection, and Amplification |
| What is a technique to reduce the dynamic range of a signal? | Compression |
| For deeper imaging depths, ? the operating frequency will most likely increase the SNR. | Lowering |
| For a system with 10 TGC sliders, if the imaging depth is set to 20cm, each slider represents? | 2cm |
| What would have a greater impact on the perceived brightness of an image, increasing the overall gain by 20 dB or increasing all of the TGCs by 20 dB? | Both changes would have the same effect on the image. |
| What is the smallest signal received if the dynamic range is 10,000 to 1 and the largest signal is 10 Volts? | 1 mV |
| In A-mode, the ? is disaplyed on the vertical axis and time corresponding to depth is displayed on the horizontal axis. | Amplitude |
| Which of the receiver functions would result in a reduction of the signal dynamic range? | Demodulation |
| The ? determines the initial amplitude, frequency, and mode of ultrasound. | Pulser |
| Techniques applied in the scan converter | Post-Processing |
| Real-time signal conditioning | Pre-Processing |
| Ignore signals below a defined level | Reject |
| Amplitude of signal divided by amplitude of noise | Signal-To-Noise |
| Any phenomenon desired to be measured | Signal |
| Unwanted signals that mask desired signals | Noise |
| Ratio of the maximum to the minimum amplitude of any quantity | Dynamic Range |
| Used to reduce the dynamic range | Compression |
| Demodulation is a means of signal ? by removing the initial transmit frequency from the returning echo. | Detection |
| A compression of 20 dB in amplitude means the range of signals has been compressed or decreased by a factor of? | 10 |
| Amplification is another word for? | Receiver Gain |
| Functions of the received in the order in which they occur | Amplification, compensation, compression, demodulation, rejection |
| What is the minimum number of shades necessary to present data? How many bits does this require? | 2,1 |
| How many bits are necessary to represent 64 gray levels? | 6 |
| How many gray levels can be represented by 10 bits? | 1024 |
| ? resolution is the ability to distinguish between neighboring structures based on change in signal brightness. | Contrast |
| ? resolution is the ability to visualize and quantify the change of a structure's position over time. | Temporal |
| ? resolution is the ability to distinguish between neighboring side-by-side structures. | Lateral |
| Aspects of detail resolution | Axial, temportal, and lateral |
| Lateral resolution is impacted by? | Both transmit and the receive beams |
| Conventional sequentially generated images have used ? transmit focus. | Single |
| With conventional sequential imaging, two ways to improve temporal resolution are? | Narrower FOV and lower line density |
| One of the downsides of a single focus is that the composite (two-way) beam is narrow only at one depth, resulting in a degradation in ? resolution at other depths. | Lateral |
| Conventional sequentially generated images with modern ultrasound systems use ? receive focus. | Dynamic Continuous |
| Multi-foci sequential imaging improves ? resolution at the expense of ? resolution. | Lateral, Temporal |
| If four foci are used in multi-foci imaging, the frame time would increase by a factor... | Less than four |
| When more than one receive beam is generated from a single transmit event, the approach is referred to as? | MLA |
| ? allows for more than one line of data to be received and processed simultaneously. | Parallel Processing |
| The benefit of MLA is an improvement in ? resolution at the expense of ? resolution unless dynamic retrospective transmit focusing is used. | Temporal, Lateral |
| Because single focus transmit results in suboptimal lateral resolution, ? was created. | Dynamic Retrospective Focus |
| Dynamic retrospective focus basically reverses ? using signals from different elements at different times to effectively create a narrow transmit focus. | Time |
| The narrowest effective (two-way) beam would be generated by using... | Retrospective dynamic transmit and dynamic continuous receive focusing |
| MLT implies that more than one ? is created simultaneously. | Transmit |
| An advantage of MLT is improved ? resolution. | Temporal |
| A disadvantage of MLT is... | Crosstalk between elements |
| The concept of ? is based on the idea of constructive and destructive interference. | Averaging |
| When signals are purely coherent, and noise is purely random, averaging nine samples results in an ? in the SNR by a factor of ? | Increase, Three |
| The averaging of multiple images generated at different angles is referred to as ? imaging. | Spatial Compound |
| Spatial compounding is a ? reduction technique. | Speckle |
| Many artifacts such as reverberation and acoustic shadowing are ? by spatial compound imaging. | Reduced |
| Extraordinarily high frame rates can be achieved by using ? imaging. | Plane wave |
| A single plane wave image would be expected to have relatively ? detail resolution, ? contrast resolution, ? SNR, and ? temporal resolution. | Poor, poor, poor, and excellent |
| Compounding plane wave images taken at varying ? sacrifices some of the extraordinary high frame rate to improve resolution and contrast. | Angles |
| ? imaging is a technique to dramatically increase the field of view by building up an image over time as the transducer is swept across the patient. | Panoramic |
| ? imaging is a technique to synchronously display live ultrasound data with uploaded, previously generated reference imaging from CT, MR, of PET scans. | Fusion |
| ? is any technique which automatically varies the processing and/or display of the data based on the signal characteristics. | Adaptive processing |
| ? is a pixel-by-pixel technique whereas ? is a frame averaging technique. | Spatial averaging, spatial compounding |
| ? is a frame averaging technique whereas ? is a technique by which ultrasound and another reference modality are linked and displayed simultaneously. | Frequency fusion, pulse inversion imaging |
| Refraction, which is governed by ? law, results in objects appearing ? displaced from their true position. | Snell's, laterally |
| ? results in the appearance of strongly reflecting structures multiple times at constant depth increments. | Reverberation |
| Two specular reflectors are located in the same vicinity. If the first reflector is insonified at an oblique angle and the second reflector is off-axis of the beam, a ? artifact will most likely result. | Multi-path |
| The ? artifact causes a strongly reflecting structure to appear too deep. | Multi-path |
| Off-axis beams which result from single element transducers are called? | Side lobes |
| Off-axis beams created by multi-element transducers are called? | Grating Lobes |
| The general effect of ? and ? is a creation of a spurious lateral structure or a clouding/haze over the image. | Side lobes and Grating lobes |
| ? error results in a misregistration of a structure because the actual propagation velocity is not assumed propagation velocity of 1540 m/s. | Speed |
| If the propagation velocity is ? 1540 m/sec, an ultrasound system will represent a structure shallower than reality. | Greater than |
| If the propagation velocity is ? 1540 m/sec, an ultrasound system will represent a structure deeper than reality. | Less than |
| One way to differentiate mirroring from reverberation artifact is that for mirroring, movement of the actual structure and the duplicated structure will be in the ? direction, whereas with reverberation will be in the ? direction. | Opposite, same |
| ? occurs in the shallow depth settings in PW Doppler. | Range Ambiguity |
| The PW Doppler gate is placed over the myocardium and mitral flow is registered from a depth that is approximately twice the Doppler gate depth. The most likely explanation is ? | Range Ambiguity |
| High PRF Doppler utilizes ? to achieve a higher ? | Range Ambiguity, Nyquist Limit |
| Similar to multi-path artifact, ? artifact results in one structure spuriously displaced twice. | Mirror Image |
| ? is the reduction or absence of echo below a highly attenuative structure. | Shadowing |
| ? is the opposite of shadowing. | Enhancement |
| ? is a brighter than normal echo below a structure which is ? attenuative than normal. | Enhancement, less |
| ? results when the Nyquist criterion is violated. | Aliasing |
| The Nyquist limit dictates that to detect a frequency of "f" you must sample at a frequency of at least... | 2f |
| Spectral mirroring is evident as a mirrored spectrum in the ? direction of strong flow. | Reverse |
| ? is an artifactual smearing of the Doppler spectrum resulting in peak velocity overestimation and possibly the diminishing of the spectral window. | Spectral broadening |
| Spectral broadening generally becomes a significant concern when using large ? arrays and insonification angles become ? | Linear, larger |
| Using sequential color Doppler for assessing venous flow with the following settings, which should you suspect as the most likely cause of artifactual color dropout? | Color sacles above or below 40 cm/sec |
| True or False: 3D/4D imaging suffers from almost all of the same imaging artifacts as 2D imaging. | True |
| One of the most significant benefits of harmonic imaging is ? | A reduction in clutter artifacts |
| Amplitude of signals from highest to lowest at the fundamental frequency. | Tissue, bubbles, blood |
| Amplitude of signals from highest to lowest at the 2nd harmonic frequency. | Tissue, bubbles, blood |
| Amplitude of signals from highest to lowest at either the fundamental or the 2nd harmonic frequency as specified? | Fundamental bubbles, harmonic tissue, fundamental blood |
| True or False: Harmonic signals are generated as a result of the non-linear propagation of sound through tissue. | True |
| True or False: Decreasing the mechanical index (MI) results in an increase in the harmonic signal strength. | False |
| True or False: Harmonic imaging results in a reduction in grating lobe artifacts. | True |
| True or False: The harmonic signal is always lower in amplitude than the fundamental signal. | True |
| True or False: Pulse inversion harmonics suffers from the same axial resolution degradation as standard harmonic imaging. | False |
| True or False: The use of contrast agents generally increases the acoustic impedance mismatch within the blood by 30 dB. | True |
| The MI below which most contrast agents will not undergo cavitation and "survive" to work effectively is? | 0.2 |
| The mechanical index of a very low MI imaging technique is? | <0.2 |
| Power modulation is a multiple pulse technique that uses... | Different amplitudes |
| Pulse inversion is a multiple pulse technique that uses... | Alternating phases |
| LVO stands for? | Left Ventricular Opacification |
| High MI techniques with contrast agents are challenging because? | Triggering is required |
| Very low MI techniques are challenging because? | They have a low signal-to-noise ratio |
| True or False: Ultrasound enhancing agents for use in cardiac applications have only been approved in the US | False |
Created by:
marissagirl