Computed Tomography Test Computed Tomography Ultimate 2

Question 1

What is the primary purpose of retrospective gating in cardiac CT?

Accepted Answer

To reconstruct images at any phase of the cardiac cycle

Answer

Retrospective gating records ECG data throughout the scan and allows reconstruction at any desired cardiac phase after acquisition.

Question 2

Which artifact appears as a dark band between two high-density objects on CT images?

Accepted Answer

Beam hardening artifact

Answer

Beam hardening causes dark streaks or bands between dense objects like bone or metal because lower-energy photons are preferentially absorbed.

Question 3

What does a CT number of -1000 HU represent?

Accepted Answer

Air

Answer

Air has a CT attenuation value of approximately -1000 Hounsfield Units, the lowest end of the standard CT scale.

Question 4

In CT, what is the 'matrix size' most commonly used in clinical scanners?

Accepted Answer

512 x 512

Answer

Clinical CT scanners most commonly use a 512 x 512 matrix, balancing spatial resolution with acceptable processing time and storage requirements.

Question 5

What is the main advantage of using iterative reconstruction over filtered back projection (FBP)?

Accepted Answer

Reduced image noise at lower radiation doses

Answer

Iterative reconstruction algorithms reduce noise more effectively than FBP, enabling diagnostic-quality images at significantly lower radiation doses.

Computed Tomography Test Practice Test

Computed Tomography Test Practice Test

Computed Tomography Test Computed Tomography Ultimate 2