Which control determines the amount of amplification occurring in the receiver?
Answer(s): B
Overall gain controls the amplification of all the received ultrasound signals uniformly. This adjustment affects the brightness of the entire image by increasing or decreasing the amplification of the echoes returning from all depths. It is a primary control for adjusting image brightness. The overall gain should be set to an appropriate level to ensure that the ultrasound image is neither too bright (over-gained) nor too dark (under-gained), allowing for optimal visualization of the anatomical structures.
American Registry for Diagnostic Medical Sonography (ARDMS). Sonography Principles and Instrumentation (SPI) Examination Review Guide.
What adjustment is needed to visualize the borders of the anatomical structures in the image below?
Answer(s): C
Dynamic range in ultrasound imaging refers to the range of signal amplitudes that the system can display. Increasing the dynamic range allows the ultrasound system to display a broader range of echo amplitudes, which enhances the contrast resolution and helps to visualize subtle differences in tissue texture and borders of anatomical structures. When the dynamic range is increased, more shades of gray are used, making the image appear softer and less contrasty, which is beneficial for delineating the borders of anatomical structures more clearly.
What is the effect of an increased aperture in a linear array transducer?
Answer(s): A
The aperture of a transducer is the active area that emits and receives the ultrasound waves. In a linear array transducer, increasing the aperture (using more elements for transmission and reception) results in a deeper focus because the beam is more tightly focused over a longer distance. This improves lateral resolution at greater depths, as the ultrasound beam maintains a narrower width for a longer distance. It allows for better imaging of deeper structures without sacrificing resolution.
What happens to the Doppler shift when the angle is changed from 30 to 60 degrees?
Answer(s): D
The Doppler shift is directly related to the cosine of the angle between the ultrasound beam and the direction of blood flow. As the angle increases from 30 degrees to 60 degrees, the cosine of the angle decreases (cosine of 30 degrees is approximately 0.87, while cosine of 60 degrees is 0.5). Since the Doppler shift is proportional to the cosine of the angle, increasing the angle results in a decreased Doppler shift. This means the measured blood flow velocities will appear lower at a 60-degree angle compared to a 30-degree angle.
Which will affect the gray-scale of a 2-D image?
Dynamic range in ultrasound imaging affects the number of gray shades displayed in a 2-D image. Adjusting the dynamic range changes how echo signals are mapped to grayscale. A higher dynamic range means more shades of gray are displayed, providing a more detailed and softer image, which is useful for differentiating subtle tissue textures. Conversely, a lower dynamic range increases contrast by displaying fewer shades of gray, making the image appear more black and white. This adjustment is crucial for optimizing image quality based on the specific diagnostic needs.
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