Image Quality Flashcards

Which CT parameter most directly controls the amount of radiation dose delivered to the patient?

Answer: mAs

mAs (milliampere-seconds) directly determines the number of X-ray photons produced and is the primary controller of patient dose.

Increasing the reconstruction field of view (FOV) while keeping matrix size constant will:

Answer: Increase pixel size and decrease spatial resolution

Larger FOV with the same matrix means each pixel covers more area, increasing pixel size and reducing spatial resolution.

A 'blooming artifact' in CT most commonly results from:

Answer: High-density metallic objects causing overestimation of structure size

Blooming occurs when high-attenuation objects like metals or calcifications appear larger than their true size due to beam hardening and partial volume effects.

Which factor primarily determines the z-axis (longitudinal) resolution in a multislice CT scanner?

Answer: Detector row width

Z-axis resolution is primarily determined by detector row width (collimation), which defines slice thickness in the longitudinal direction.

Quantum mottle in CT images is primarily caused by:

Answer: An insufficient number of detected photons

Quantum mottle (noise) occurs when too few photons reach the detector, causing statistical fluctuations that appear as grainy image texture.

The Hounsfield unit (HU) value of pure water is:

Answer: 0

By definition, pure water is assigned an HU value of 0 on the Hounsfield scale used in CT imaging.

When evaluating a CT image for streak artifacts emanating from a hip prosthesis, the BEST corrective technique is:

Answer: Metal artifact reduction (MAR) reconstruction algorithm

Metal artifact reduction algorithms use iterative or sinogram-based techniques to model and subtract metal-induced streaks from the image.