COMPUTED TOMOGRAPHY (CT) IMAGE PRODUCTION II

Which sequence correctly describes the CT imaging workflow from start to finish?

Inputs (Data Acquisition) → Processing (Reconstruction) → Outputs (Image Display)

During which step of the CT workflow are raw data collected using the x-ray tube, detectors, and patient positioning?

Inputs (Data Acquisition)

True or False:

If data acquisition is performed incorrectly, the reconstruction process can compensate for it fully.

False, If acquisition is flawed, the entire scan suffers.

Which of the following directly affects CT image quality and accuracy?

The data acquisition step

The scanner's detectors, x-ray tube, and patient positioning are all part of which CT workflow component?

Step 1 - Inputs (Data Acquisition)

If the ________ is flawed, the entire CT scan suffers.

data acquisition

True or False:

Step 1 of the CT workflow involves reconstruction of raw data into an image.

False

What process builds cross-sectional slices from the collected raw data?

Reconstruction

What is the main purpose of the reconstruction step in CT imaging?

To convert raw scan data into a visible digital image

True or False:

Reconstruction happens before data acquisition begins.

False

Reconstruction uses __________ to generate cross-sectional slices from raw scan data.

mathematical algorithms

When does the processing (reconstruction) step occur in the CT workflow?

After the scan data have been fully acquired

Reconstruction translates the raw data collected during acquisition into a __________.

visible image

True or False:

The image display step focuses on collecting data from the patient before the reconstruction process.

False

What happens during Step 3 of the CT workflow?

final images appear on the monitor for interpretation

True or False:

During the image display step, images can be adjusted using windowing, annotations, and measurements.

True

Which statement best describes how images are organized in Step 3?

They are displayed as pixels in a matrix or voxels in 3D form

What can occur during the image display phase to enhance diagnostic value?

Windowing, annotations, and measurement adjustments

In the final step of the CT workflow, diagnostic images are ready for __________.

interpretation

True or False:

CT imaging is considered 2D because it displays a single flat image like traditional radiography.

False

CT imaging captures data in how many dimensions?

Three (3)

Each CT scan includes which three axes?

X, Y, and Z

The X-axis runs:

Right to left

The Y-axis runs:

Front to back

The Z-axis runs:

Head to toe

The axis that runs horizontally across the patient is:

X-axis

The axis that runs vertically from anterior to posterior is:

Y-axis

The axis that runs longitudinally from superior to inferior is:

Z-axis

Movement along the X-axis produces slices in which plane?

Sagittal plane

Movement along the Y-axis produces slices in which plane?

Coronal plane

Movement along the Z-axis produces slices in which plane?

Transverse plane

True or False:

The Z (transverse) plane is also referred to as the axial plane in CT imaging.

True

True or False:

The Z-axis is also referred to as the longitudinal axis because it runs superior to inferior.

True

CT creates a 3D image by combining:

Thousands of voxels that represent small parts of the patient

What does the term "voxel" represent in CT imaging?

A 3D volume element based on x, y, and z coordinates

The relationship between voxel and pixel can be summarized as __________.

Voxel = Volume + Pixel

Each voxel in a CT image represents:

A small 3D section of the patient's body

Each voxel in a CT image corresponds to a specific location determined by its position on the __________.

x, y, and z axes

In X-ray, "centering" refers to aligning anatomy with the central ray. What is the equivalent concept in CT?

Iso-center

True or False:

In CT, the iso-center represents the midpoint of the x- and y-axes within the scanner.

True

What is the ideal location for the anatomy of interest during a CT scan?

At the scanner's iso-center

What is the main benefit of positioning the patient at the iso-center during a CT scan?

It ensures equal radiation distribution

Where is the iso-center located within the CT gantry?

Right in the middle of the doughnut hole

True or False:

Positioning the patient at the iso-center ensures equal radiation distribution.

True

What does the term "Field of View" (FOV) refer to in CT imaging?

The anatomy included in the scan or visible on the image

True or False:

Field of View represents the anatomical area that is scanned or displayed on the screen.

True

SFOV stands for __________.

Scan Field of View

SFOV represents:

The entire area scanned by the CT system

True or False:

The DFOV is smaller than the SFOV

True

DFOV represents:

The portion of the scanned area used for image display

True or False:

Just because an area was scanned (SFOV) means it is always displayed (DFOV).

False

SFOV covers the entire scanned region, while DFOV determines the part that is __________.

shown or displayed

Where is the raw data from a CT scan saved?

SFOV

What does DFOV stand for in CT imaging?

Display Field of View

Who determines the DFOV for image interpretation?

The technologist during post-processing

What color represents the area scanned by the CT system in the SFOV vs DFOV image?

Gray

What color represents the area processed and viewable on the image (DFOV)?

Black

True or False:

Anatomy outside the SFOV cannot be recovered because it was never scanned.

True

If anatomy is within the SFOV but outside the DFOV, what allows recovery of that data?

Retrospective reconstruction

If anatomy is outside the __________, it results in lost data and cannot be recovered.

SFOV

What is the DFOV based on?

Localizer images

The SFOV is based on scout images.

False

True or False:

Once the DFOV is set, it cannot be changed after the scan.

False

The DFOV can be adjusted larger or smaller using the:

Console

The DFOV is adjusted according to:

The anatomy size and purpose of the scan

The DFOV can be thought of like a __________.

window that can be resized to focus on important anatomy

True or False:

The DFOV is based on scout images.

True

True or False:

Acquisition thickness refers to the thickness of the patient's anatomy being scanned.

False

Which best describes data collection in axial scanning?

Data is collected one section at a time

How does the x-ray tube and table move during axial scanning?

The tube rotates, then the table moves.

Axial scanning is also known as __________.

step-and-shoot scanning

What type of path does the x-ray tube follow in helical scanning?

A spiral path around the patient

True or False:

Helical scanning provides faster image acquisition compared to axial scanning.

True

How do the x-ray tube and table move during helical scanning?

They move continuously together

Which analogy best describes helical scanning?

Like recording a video while walking — continuous movement for faster results

What is one major advantage of helical scanning?

Faster scans with fewer motion artifacts

Helical scanning helps reduce:

Patient breath holds

True or False:

Helical scanning keeps pace with fast-moving IV contrast, improving diagnostic timing.

True

Helical scanning eliminates __________, improving patient comfort and diagnostic accuracy.

pauses between sections

Which type of CT scanning is essential for precise contrast timing in chest studies?

Helical scanning

True or False:

Spiral (helical) scanning captures the entire organ in one rotation.

False

True or False:

Pitch determines how tightly or loosely the helical path wraps around the patient during scanning.

True

True or False:

When pitch is less than 1, there is overlap between slices

True

Volume scanning captures the entire organ in how many rotations?

One rotation

True or False:

During volume scanning, the table does not move.

True

Volume scanning requires at least __________ detector rows.

250

What type of CT scanning captures an entire organ in a single rotation without table movement?

Volume scanning

A patient is scheduled for a CT of the abdomen and pelvis with IV contrast to evaluate possible internal bleeding. Which scanning method would be most appropriate for this exam?

Helical scanning

A patient is scheduled for a CT study to evaluate coronary artery function. The radiologist needs the entire heart captured instantly without table motion to reduce motion artifacts. Which scanning method should be used?

Volume scanning

True or False:

Axial, helical, and volume scans all produce completely different image types.

False, they produce similar images, but are obtained differently.

The acquisition rate in CT refers to:

How fast a CT scan is completed

Which of the following does NOT control the CT scan's acquisition rate?

Tube filtration

Scan speed is controlled by rotation time, acquisition thickness, and __________.

beam width

A technologist decreases the rotation time while increasing the mA during a CT scan. What was the likely reason for making these adjustments?

To speed up scan time while maintaining image quality

What does a shorter rotation time result in?

Faster scan speed

A technologist is preparing a trauma patient for a rapid chest CT. The goal is to capture images as quickly as possible to evaluate internal bleeding. Which factor would most directly help increase scan speed?

Decreasing the rotation time

A shorter rotation time can increase __________ if mA is not adjusted.

image noise

True or False:

Shorter rotation time results in a faster scan.

True

What is one advantage of using a shorter rotation time?

Less motion artifact

A technologist reduces the rotation time to decrease patient motion during a chest CT. After scanning, the images appear grainier than usual. What is the most likely reason?

The mA was not increased to maintain image quality