ARDMS SPI - ARDMS Sonography Principles and Instrumentation Image Formation and Processing Questions and Answers

Question 1

A sonographer is trying to improve the temporal resolution while imaging the fetal heart. Which of the following adjustments would be most effective?

Accepted Answer

Decreasing the imaging depth

Answer

Temporal resolution is determined by the frame rate. To increase the frame rate, the time it takes to acquire each frame must be reduced. Decreasing the imaging depth reduces the pulse-return time (go-return time), allowing the system to listen for a shorter period and thus acquire lines faster, which increases the frame rate. Increasing focal zones, widening the sector, or increasing line density would all require more time to build a frame, thereby decreasing temporal resolution.

Question 2

Which of the following functions is considered a preprocessing function because it can only be performed on a live image before the data is stored in the scan converter?

Accepted Answer

Write Magnification

Answer

Preprocessing functions manipulate the image data before it is stored in the scan converter memory. Write Magnification (or Write Zoom) is a classic example of preprocessing; it rescans the selected region of interest with a higher line density to generate a new, higher-resolution image. This can only be done on a live image. Read magnification, caliper placement, and grayscale map adjustments are postprocessing functions that can be applied to a frozen image.

Question 3

The primary function of the scan converter in an ultrasound system is to:

Accepted Answer

Format the echo data from the spoke format into a video format for display.

Answer

The scan converter, or image processor, is a digital memory component that receives echo data from the receiver. Its main job is to reformat this data, which is acquired in a spoke or line-by-line format (like polar coordinates for a sector transducer), into a standard raster scan or video format (Cartesian coordinates) that can be displayed on a monitor.

Question 4

An ultrasound system's ability to display many shades of gray is most directly related to which of the following?

Accepted Answer

The number of bits per pixel

Answer

The number of shades of gray an ultrasound system can display is known as its contrast resolution. This is determined by the bit depth of the digital memory (scan converter). The number of possible gray shades is calculated as 2 to the power of the number of bits (2^n). For example, a system with 8 bits per pixel can display 2^8, or 256, shades of gray.

Question 5

A sonographer freezes an image and then activates the zoom function to enlarge a specific area of interest. This action results in larger pixels and does not improve spatial resolution. Which type of magnification was used?

Accepted Answer

Read magnification

Answer

Read magnification is a postprocessing function that is applied to a frozen image. It takes the existing pixel data stored in the scan converter and simply enlarges it, making each pixel bigger. Because no new data is acquired, the spatial resolution is not improved and may even appear degraded. Write magnification, a preprocessing function, would rescan the area live to create a new image with more pixels, thereby improving spatial resolution.

ARDMS SPI - ARDMS Sonography Principles and Instrumentation Practice Test

ARDMS SPI - ARDMS Sonography Principles and Instrumentation Practice Test

ARDMS SPI - ARDMS Sonography Principles and Instrumentation Image Formation and Processing Questions and Answers