ct

• z axis refers to the thickness of the plane and determines the thickness of the slices
• The most common matrix size is 512
• FOV increased, fixed matrix. Result: increased pixel size
• Fixed FOV, increase matrix size. Result: decreased pixel size
• Intermediate attenuation are areas represented by various shades of gray
• Hounsfield unit quantify the degree that a structure attenuates an x-ray beam
• Raw data are all the thousand bits of data acquired by the system with each scan.
• Lateral- refers to movement towards sides of the body
• Midsagittal plane located either the left or right side of the midline
• Collimator restricts the x-ray beam to a specific area, thereby reducing scatter radiation
• Hard drive is an essential components of all CT systems
• ROM refers to the computers internal memory
• Pitch is the relationship between slice thickness and table travel

  per rotation during a helical scan acquisition.
• Two common 3D techniques are the MIP and the MinIP.
• The ability to distinguish an object that is nearly the same density as its background is referred to as low contrast detectability.
• Contrast resolution may also be referred to as the sensitivity of the system; hence the term low contrast sensitivity is also used
• Noise is caused by the combination of many factors, the most prevalent being quantum noise, or quantum mottle.
• Ray– the path the x-ray beam takes from tube to detector
• View– a complete set of ray sums
• Filtering– a process to minimize streak artifacts in a star pattern on the image
• DFOV determines how much of the raw data is used to create an image
• Saving studies on auxillary devices for possible future viewing is referred to as archiving
• In retrospective reconstruction, Display field of view (DFOV), image center, and reconstruction algorithm can be changed on both axial and helical data
• Region of interest is the first step in a number of image display and measurement functions
• Cooling Systems are important because many imaging components can be affected by temperature fluctuation
• SFOV determines the area within the gantry for which raw data are acquired
• Shading due to a group of channels or views deviating gradually from the true measurement
• Reformatted images can be either 2D or 3D in nature
• Features of MSCT/MDCT

  • Advantages

  1. No motion artifacts
  2. Improved lesion detection
  3. Reduced partial volume
  4. Optimized IV contrast
  5. Multiplanar images improved 

• Features

  of MSCT

  • Limitations

  1. Increased image noise
  2. Reduced z-axis resolution
  3. Increased processing time