CAMRT - Canadian Association of Medical Radiation Technologists Image Production and Quality Questions and Answers

Question 1

A digital radiograph of a knee appears excessively noisy and grainy. The exposure indicator (EI) is significantly below the target range. Which of the following is the most likely cause for this appearance?

Accepted Answer

Insufficient mAs

Answer

A grainy or noisy appearance, known as quantum mottle, is caused by an insufficient number of x-ray photons reaching the detector. The mAs setting directly controls the quantity of photons produced. A low exposure indicator value confirms that the detector received inadequate exposure, which is most commonly due to insufficient mAs.

Question 2

Which of the following technical factor adjustments will increase the penetrability of the x-ray beam, resulting in lower image contrast?

Accepted Answer

Increasing the kVp

Answer

Kilovoltage peak (kVp) controls the kinetic energy of the electrons striking the anode, which in turn determines the maximum energy and overall quality of the x-ray photons. Increasing the kVp produces a higher-energy, more penetrating x-ray beam. This increased penetration leads to less differential absorption between tissues, resulting in a longer scale of contrast (more shades of gray).

Question 3

An MRT is performing a CT scan of the head. The resulting axial images show dark, streak-like artifacts and a 'cupping' artifact where the central portion of the brain parenchyma appears artificially dark. This is most characteristic of:

Accepted Answer

Beam hardening artifact

Answer

Beam hardening artifacts occur because a polychromatic x-ray beam becomes 'harder' (higher average energy) as it passes through dense objects like the skull, as lower-energy photons are preferentially absorbed. This differential absorption is not fully corrected by standard reconstruction algorithms, leading to characteristic dark streaks and 'cupping' where the center of a uniform object appears less dense than its periphery.

Question 4

In digital radiography, what is the primary purpose of applying a look-up table (LUT) during image processing?

Accepted Answer

To map raw pixel data to specific brightness and contrast levels for display

Answer

A look-up table (LUT) is a post-processing tool that translates the raw numerical pixel values from the detector into specific grayscale values for display on a monitor. Each LUT is designed to provide the optimal brightness and contrast for a specific anatomical part, ensuring consistent image presentation regardless of minor exposure variations.

Question 5

Which combination of geometric factors will result in the highest degree of image unsharpness (penumbra)?

Accepted Answer

Large focal spot, short SID, long OID

Answer

Geometric unsharpness, or penumbra, is the blurring at the edges of a structure. It is maximized by using a large focal spot, a short source-to-image distance (SID), and a long object-to-image distance (OID). Each of these factors increases the divergence of the x-ray beam as it passes the edge of the object, creating a larger, more poorly defined shadow on the detector.

CAMRT - Canadian Association of Medical Radiation Technologists Practice Test

CAMRT - Canadian Association of Medical Radiation Technologists Practice Test

CAMRT - Canadian Association of Medical Radiation Technologists Image Production and Quality Questions and Answers