Computed Tomography Test Computed Tomography Science 4

Question 1

The Nyquist theorem in CT states that to accurately represent a spatial frequency, the sampling rate must be at least:

Accepted Answer

Twice the frequency of interest

Answer

The Nyquist criterion requires a sampling frequency at least twice the highest spatial frequency to avoid aliasing artifacts in the reconstructed image.

Question 2

What is the primary advantage of dual-energy CT (DECT) over single-energy CT?

Accepted Answer

Material decomposition and iodine quantification

Answer

DECT acquires data at two different kVp levels, enabling material decomposition to identify and quantify iodine, calcium, uric acid, and other substances.

Question 3

Quantum noise in CT images is primarily a function of:

Accepted Answer

The number of photons reaching the detector

Answer

Quantum (photon) noise arises from statistical fluctuations in photon counts; fewer photons (low mAs or high attenuation) result in increased noise.

Question 4

In CT, the term 'z-axis resolution' refers to resolution along which dimension?

Accepted Answer

Superior-to-inferior patient axis

Answer

The z-axis is the longitudinal axis running head-to-foot along the patient, and z-axis resolution determines the ability to distinguish structures in that direction.

Question 5

Which factor primarily determines the minimum slice thickness achievable in a multi-detector CT system?

Accepted Answer

Individual detector element width in the z-direction

Answer

The detector element width in the z-axis sets the minimum detector aperture and therefore the thinnest slice that can be acquired.

Computed Tomography Test Practice Test

Computed Tomography Test Practice Test

Computed Tomography Test Computed Tomography Science 4