Chapter 4: Image Display Flashcards
- Are output devices that show CT images
stored in the computer memory. - Are used by the technologist to perform the CT scan procedure.
DISPLAY MONITORS
- Heavier, bulkier, and less durable
- Produces more heat compared to modern
monitors - Modified for improved image resolution
compared to the standard TVs
CATHODE-RAY TUBE (CRT) Monitors
- Lower luminance and spatial resolution
- has become obsolete
CATHODE-RAY TUBE (CRT) Monitors
- Thin, lightweight and more durable
- higher luminance and spatial resolution,
enhances image quality - Generates less heat and consumes less
power
Flat-Panel Monitors (TFT LCD Thin film
transistor, Liquid Crystal Display)
More compact and practical for modern CT
scanners
Flat-Panel Monitors (TFT LCD Thin film
transistor, Liquid Crystal Display)
- output devices used to transfer CT images to physical film.
Cameras
- transfers images displayed on the monitor directly to film
- relies on the light emission spectrum of the monitor.
Multiformat Cameras
- bypasses the monitor and transfers data
directly from the CT computer to the film. - uses laser beam to expose the film.
Laser Cameras
- controls the range of CT numbers (gray
shades) visible on the image.
Window Width (WW)
- sets the midpoint of the CT number range
displayed.
Window Level (WL)
- is used in CT imaging to display varying
densities of tissues by assigning HU to
different shades of gray.
Grayscale
- a critical tool in medical imaging for
evaluating tissue density.
Hounsfield Measurement
is used to distinguish different tissues, detect lesions, and aid in diagnosis
Hounsfield Measurement
placed over an area to measure
the density of that specific pixel
Cursor (+)
this can be a quick method but only gives the value of a single pixel, which may not
represent the region
Cursor (+)
- a selected area in an image, and the system calculates the average Hounsfield Value for all pixels within this region.
- is typically more accurate for areas of
interest such as lesions or organs.
Region of Interest (ROI)
- measures the variation or spread of
Hounsfield Value within the ROI
STANDARD DEVIATION
Provides the consistency of pixels within the region of interest.
STANDARD DEVIATION
- essential for determining the size of an
abnormality and allows accurate positioning of biopsy needles or drainage devices. - helpful in both diagnostic and procedural
applications.
Distance measurement
- Involves adding important information to
each CT image
IMAGE ANNOTATION
- Shows the slice lines in corresponding
locations on the scout image, helps localize
slices according to anatomical landmarks for better navigation during image
interpretation.
REFERENCE IMAGE
- Increases the size of the image but does not improve the resolution.
IMAGE MAGNIFICATION
- Displays more than one image in a single
frame
MULTIPLE IMAGE DISPLAY
- A graphical display showing how frequently a range of HU occurs in a ROI.
HISTOGRAM
- converts axial images to other planes, for
better diagnosis. - eliminates the limitation of positioning the
patient in a single plane.
Multiplanar Reformatting (MPR)
- creates a 3D image from the 2D slices for a more detailed view
3D Reformatting
converts signals into analog formal for
display
DAC
Factors that can affect accuracy of HU reading
- Image Noise/Artifacts
- Volume Averaging
Two types of cameras in CT systems
Multiformat
Laser
Types of monitors in CT systems
Cathode-ray tube monitors
Flat-panel monitors
Two ways of measuring the HU
Cursor (+)
Region of interest (ROI)
Factors that can Influence Standard Deviation
- Mixed Attenuation
- Image Noise
