Radiography Exam Computed Tomography (CT) Basics

Question 1

In computed tomography, the Hounsfield unit (HU) value for water is:

Accepted Answer

0 HU

Answer

-1000 HU

Answer

+1000 HU

Answer

+40 HU

Question 2

The CT scan parameter that most directly controls the radiation dose to the patient is:

Accepted Answer

mAs (tube current × time)

Answer

Pitch

Answer

Slice thickness

Answer

Field of view (FOV)

Question 3

Which CT reconstruction algorithm produces images with the sharpest edges and highest spatial resolution, typically used for lung and bone imaging?

Accepted Answer

High-frequency (edge-enhancing) kernel

Answer

Soft-tissue (smoothing) kernel

Answer

Standard kernel

Answer

Noise-reduction (iterative) algorithm

Question 4

In helical (spiral) CT, pitch is defined as:

Accepted Answer

Table travel per rotation divided by the total collimation width

Answer

Slice thickness divided by table speed

Answer

Number of detector rows multiplied by rotation time

Answer

Field of view divided by matrix size

Question 5

The CTDI (CT Dose Index) metric most commonly used to represent dose for a specific scanner and protocol is:

Accepted Answer

CTDIvol (volumetric CTDI)

Answer

CTDIw (weighted CTDI)

Answer

CTDI100

Answer

DLP (dose-length product)

Question 6

Window width (WW) and window level (WL) in CT imaging refer to:

Accepted Answer

The range and center of HU values displayed as the visible gray scale

Answer

The slice thickness and reconstruction interval

Answer

The tube voltage and tube current used for the scan

Answer

The matrix size and pixel size of the image