Ultrasound Physics and Instrumentation - MRD535

A-mode displays echo information in one dimension showing spike amplitude and depth, while B-mode creates a two-dimensional image by displaying the intensity (brightness) of echoes along multiple scan lines, providing a cross-sectional view.

A-mode images display the amplitude of returning echoes against time. It is represented as spikes, whose height represents the amplitude of the echo, and their horizontal position corresponds to the depth of the reflector.

B-mode images are generated by scanning the ultrasound beam across the area of interest. Multiple scan lines are acquired, each providing a line of echo intensity information. These lines are combined to make a two-dimensional image of the cross-section being scanned.

<p>M-mode is used to visualize the movement of objects lying along the ultrasound beam. It essentially provides a time-dependent representation of the movement of reflectors within the beam path.</p> Signup and view all the answers

<p>The intensity or brightness of a dot in a B-mode image is directly proportional to the strength of the returning echo. Strong echoes, indicating a high degree of reflection, appear as bright dots, while weak echoes appear as darker dots.</p> Signup and view all the answers

<p>A-mode provides only one-dimensional information along the beam path. This limitation prevents A-mode from creating a detailed two-dimensional image, making it less suitable for comprehensive anatomical assessments.</p> Signup and view all the answers

<p>In B-mode, the ultrasound beam is swept across the area of interest. Each scan line captures a series of echoes, which are displayed as dots. By combining these dots from multiple scan lines, a composite 2D image is created, resembling a slice through the scanned region.</p> Signup and view all the answers

<p>B-mode offers the advantage of displaying a two-dimensional cross-sectional image, allowing visualization of a larger area and providing more comprehensive structural information compared to the one-dimensional data provided by A-mode.</p> Signup and view all the answers

<p>M-mode provides one-dimensional information along the ultrasound beam path, capturing movement over time. Real-time imaging uses rapid B-mode scanning to produce a series of static images at a fast rate, creating the illusion of motion.</p> Signup and view all the answers

<p>The M-mode technique is suitable for examining cardiac motion because it captures movement along the beam path, which aligns perfectly with the direction of heart valve and muscle contractions. This allows for detailed visualization of the heart's movement over time.</p> Signup and view all the answers

<p>The bug's leg movements create disturbances that propagate as circular waves outward in all directions from the source. Since the disturbances travel in the same medium at the same speed, they reach the edges of the puddle simultaneously.</p> Signup and view all the answers

<p>Observer A will observe a lower frequency of disturbances than the bug's actual frequency. This is because the bug is moving away from Observer A, increasing the distance between each consecutive disturbance and Observer A, resulting in a longer time interval between arrivals.</p> Signup and view all the answers

<p>Observer B will observe a higher frequency of disturbances than the bug's actual frequency. Since the bug is moving towards Observer B, the distance between consecutive disturbances and Observer B decreases, leading to a shorter time interval between their arrivals, resulting in a higher perceived frequency.</p> Signup and view all the answers

<p>The rate of image acquisition and viewing in real-time imaging is critical for creating the impression of motion. A rate exceeding 25 image frames per second is necessary to achieve a smooth and continuous perception of movement.</p> Signup and view all the answers

<p>Recording dot lines at different lateral positions in M-mode imaging captures the time variation of moving structures graphically. By representing the position of the structure at different moments along a lateral axis, the M-mode allows for visualization of the structure's motion over time.</p> Signup and view all the answers

<p>The M-mode technique relies on the ultrasound beam path to measure the displacement of the structure over time. Therefore, the structure must lie along the beam path for the reflected ultrasound waves to accurately capture its movement.</p> Signup and view all the answers

<p>The perceived frequency difference is caused by the relative motion between the source of sound and the observer.</p> Signup and view all the answers

<p>An observer moving towards the source experiences a higher frequency (Doppler shift), while an observer moving away hears a lower frequency.</p> Signup and view all the answers

<p>The Doppler effect can be observed in sound waves, light waves, and water waves.</p> Signup and view all the answers

<p>When the source is stationary, the wavefronts are neither compressed nor stretched, resulting in no shift in frequency.</p> Signup and view all the answers

<p>Doppler mode is used in medical ultrasound to study blood flow by detecting frequency shifts in echoes from moving red blood cells.</p> Signup and view all the answers

<p>The Doppler shift allows observers to determine the velocity of a moving structure by analyzing the changes in frequency.</p> Signup and view all the answers

<p>Observer B perceives a higher frequency because they are moving towards the source, causing wavefronts to be compressed.</p> Signup and view all the answers

<p>As the distance between the observer and the source decreases, the frequency received increases; conversely, it decreases as the distance increases.</p> Signup and view all the answers

<p>If the reflector moves towards the transducer, the detected frequency increases, indicating a positive Doppler shift. Conversely, if it moves away, the detected frequency decreases, reflecting a negative Doppler shift.</p> Signup and view all the answers

<p>The angle $ heta$ affects the cosine component in the formula, directly influencing the magnitude of the Doppler shift. A smaller angle results in a larger cosine value, hence a greater shift.</p> Signup and view all the answers

<p>The Doppler shift is approximately 0.0078MHz.</p> Signup and view all the answers

<p>The four types are Continuous Wave Doppler, Pulse Wave Doppler, Color Flow Doppler, and Power Doppler. They differ primarily in how they capture and analyze blood flow velocities.</p> Signup and view all the answers

<p>Continuous Wave Doppler cannot specify the location along the Doppler line where velocities are recorded, only that they are present. This results in a lack of spatial resolution.</p> Signup and view all the answers

<p>The speed of sound, denoted as $c$, is used in the denominator of the Doppler shift equation, impacting the overall value. A higher speed of sound would decrease the resulting Doppler shift.</p> Signup and view all the answers

<p>Higher blood velocity increases the Doppler shift, resulting in a higher received frequency. This relationship is directly proportional within the context of the Doppler equation.</p> Signup and view all the answers

<p>$fd$ represents the Doppler shift, while $fr$ is the received frequency, and $ft$ is the transmitted frequency. This equation quantifies the change in frequency due to motion.</p> Signup and view all the answers

Amplitude mode, displaying reflected sound as spikes.

Brightness mode, shows echoes as dots of varying brightness.

Motion mode, records moving objects as electronic traces.

Displays live images as the scan occurs.

Measures the change in frequency or wavelength of echoes.

Study of sound waves and their interactions with tissues.

Device that converts electrical energy into ultrasound waves.

Time taken for a sound wave to return to the transducer.

The distance from the transducer to the structure being examined, critical for accurate imaging.

A rapid scanning method generating images at high speeds creating motion perception.

The speed at which images are captured in real-time imaging, typically over 25 frames per second.

Change in observed frequency of a wave from a moving source relative to an observer.

The number of disturbances produced by a moving source per second, influencing wave observation.

Ripples caused by a moving object in a medium, like water from a bug's leg movements.

The apparent change in frequency due to the relative motion of the source and observer.

The observer who experiences a lower frequency of sound because the source is moving away.

The observer who experiences a higher frequency of sound because the source is moving towards them.

When the source moves toward an observer, sound waves are compressed, increasing frequency.

A sound source that is not moving; wave fronts remain unchanged and no Doppler effect occurs.

Using the Doppler effect to determine if an object is moving, and in which direction.

A color system used to indicate blood flow direction: Blue Away, Red Toward.

fd = (fr - ft) = (2 ft v cosθ) / c, where fd is Doppler shift.

Values of cos θ for angles related to Doppler measurements affect frequency calculations.

A Doppler method where ultrasound waves are transmitted and received continuously.

A Doppler method that emits pulses of ultrasound, allowing better location of flow velocities.

A method that uses colors to visualize blood flow and its velocity in real-time.

A type of Doppler imaging that shows blood flow strength, but not direction.