CT Image Quality Quiz

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Questions and Answers

What is the primary purpose of Maximum Intensity Projection (MIP) in CT imaging?

To average pixel values for better image quality

To display the lowest value pixels along a line

To create a full 3D image using all data points

To reconstruct images using the highest value pixels along any line (correct)

Which view does the Multiplanar Reconstruction (MPR) NOT allow?

Saggital

Rectangular (correct)

Coronal

Transverse

How does the Shaded Volume Display (SVD) enhance image quality compared to Shaded Surface Display (SSD)?

By focusing on surface boundaries only

By limiting the viewing angle

By utilizing the entire data set (correct)

By using only selected pixels

What is one limitation of using Maximum Intensity Projection (MIP)?

It may miss small vessels passing through a voxel Signup and view all the answers

Which of the following is NOT a type of image representation mentioned in the content?

Image Averaging Display (IAD) Signup and view all the answers

What distinguishes the Shaded Surface Display (SSD) from other imaging techniques?

It creates images that appear as organ surfaces Signup and view all the answers

In what way does Multislice helical CT excel?

In 3D Multiplanar Reconstruction (MPR) Signup and view all the answers

What is the main advantage of the Shaded Volume Display (SVD) compared to other imaging methods?

It produces better image quality and more information Signup and view all the answers

Which method measures the scanner's ability to separate two adjacent objects?

Spatial resolution Signup and view all the answers

What does a low spatial frequency represent in CT imaging?

Large objects Signup and view all the answers

How does slice thickness affect spatial resolution in CT imaging?

Thinner slices improve spatial resolution Signup and view all the answers

What reflects the ability to distinguish soft tissues in CT imaging?

Contrast resolution Signup and view all the answers

What is the primary cause of image noise in CT systems?

Pixel size Signup and view all the answers

Linearity in CT imaging refers to which of the following?

The relationship between CT numbers and linear attenuation Signup and view all the answers

What type of object tends to drift in CT imaging measurements?

Uniform objects like water Signup and view all the answers

Which technique is used to increase image accuracy by manipulation of raw data?

Image reconstruction Signup and view all the answers

What effect does high noise have on CT images?

It causes graininess Signup and view all the answers

What is the primary benefit of solid-state detectors compared to film in CT imaging?

Better differentiation of similar densities Signup and view all the answers

What does a high noise level in CT images typically indicate?

Reduced image clarity Signup and view all the answers

What effect does image filtering have on CT images?

Improves soft tissue discrimination Signup and view all the answers

Which parameter directly affects the uniformity of CT images?

Consistent calibration of the system Signup and view all the answers

Study Notes

CT Image Quality

Five methods are used to measure CT image quality: spatial resolution, contrast resolution, noise, linearity, and uniformity.

Spatial Resolution

Spatial resolution measures how well a CT image can differentiate small objects.
Blurring of sharp interfaces in images is inversely proportionate to spatial resolution.
Smaller pixel sizes result in better spatial resolution.
Spatial resolution depends on pixel size.
Low spatial frequencies represent large objects, while high frequencies represent small objects.
Resolution is related to the detector element size; thinner slices and smaller voxel sizes improve resolution.
Spatial resolution is expressed as line pairs per centimeter (lp/cm).

Contrast Resolution

Contrast resolution refers to the ability to differentiate tissues with similar densities.
Multislice helical CT excels in this area.
The attenuation coefficient depends on x-ray energy and the atomic number of the tissue.
CT utilizes x-ray absorption to determine tissue density.
Amplified contrast scales improve differentiation of adjacent tissues.
Contrast resolution is affected by image noise and the uniformity of the object.

Noise

CT image noise appears as graininess.
Noise is affected by various factors such as kVp, filtration, pixel size, slice thickness, detector efficiency, and patient radiation dose.
Low noise appears smooth, while high noise appears spotty or blotchy.
Variation in CT numbers from the ideal zero value is a measure of noise.
Image noise limits the resolution of low-contrast objects.

Linearity

Linearity refers to the relationship between CT numbers and the linear attenuation of the imaged object.

Uniformity

Uniformity ensures consistent CT number values for a uniform material (e.g., water).
CT values for water can vary slightly from day to day or hour to hour.

CT Image Manipulation and Display

Localizer scans (scout images) are used to position the patient and verify anatomy in the CT scan field of view.
These scans are performed with the x-ray tube stationary.
Image enlargement reduces resolution.
Image filtering techniques smooth the image and, in some cases, enhance edges.
Contrast is improved by adjusting window width and level.

Image Manipulation

Image reconstruction is the process of manipulating raw CT data
various image manipulations and filters produce modified images (e.g., MIP, MPR)
Various manipulation techniques include different filters, display field of view, multiplanar reconstructions, and maximum intensity projection.

3D Imaging

Multiplanar reconstruction (MPR) is a method to generate sagittal, coronal, and oblique views from axial images.
Other 3D image manipulations allow for volume and surface rendering, maximizing intensity projections, and shaded surface/volume displays.

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Description

Test your understanding of CT image quality with this quiz focusing on spatial and contrast resolution. Explore key concepts such as pixel sizes, resolution measurements, and the significance of the attenuation coefficient. This quiz will help reinforce your knowledge of imaging technologies in medical settings.