Maintaining Your CT Scanner Calibration

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Maintaining Your CT Scanner Calibration
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By Vikki Harmonay
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With more than 75 million CT scans performed each
year in the U.S., the demand for accurate, high
resolution images is high. If your CT Scanner
isnt calibrated correctly and on a regular
basis, you might not be able to handle the demand
for diagnostic, therapeutic and interventional
procedures in your clinic, hospital, urgent care
center or imaging facility. To make sure your CT
Scanner delivers high resolution images of
nerves, arteries and other vascular structures,
its important to calibrate your CT unit on a
regular basis. While there are no hard and fast
deadlines for calibration maintenance, your
bio-med team, radiologists and department imaging
directors should determine the right protocols
for calibrating the CT Scanners you have
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What Is CT Scanner Calibration?

• CT Scanner calibration is when an object or
  phantom with a known radio density is scanned to
  see if its measurements are giving the
  appropriate Hounsfield units (HU). A HU value
  allows you to measure the absorption/attenuation
  of radiation within tissue. A grayscale is
  produced using a studys appropriate HU during
  the CT reconstruction phase. CT scanners can
  render more than 200 different shades of gray,
  ranging from the lightest whites to the darkest
  darks. This kind of contrast allows you to detect
  the slightest difference within 2 in tissue
  density. If your CT Scanner isnt calibrated
  correctly, it can result in image distortion or a
  lack of proper contrast.

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This can lead to misdiagnosis or even a delay in
the treatment of critically ill patients. A
routine CT calibration is needed to maintain
image accuracy without distortion or loss of
value. However, some CT Scanners need calibration
more often, like those used for CT
angiography. If you are considering buying a CT
Scanner thats used or refurbished, its
important to check the calibration and test the
accuracy for the specific studies performed at
your practice or facility.
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• Calibration depends on technological
  characteristics, image viewing conditions and
  exposure factors used. The following parameters
  are tested during the calibration of a CT
  Scanner
• The CT number. This calculates the relevant
  number of the bodys different tissues.
• Linearity is measured with a phantom and several
  materials that mimic different tissues. The
  images are consequently compared with the actual
  HU of the tissue.
• The calibration also measures the uniformity or
  homogeneity of the image. This ensures that
  hardening artifacts are avoided and that theres
  a uniform appearance free from artifacts when the
  tissue is imaged.

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• Spatial resolution provides the ability to
  distinguish differences between two structures
  with different densities, like muscle versus fat
  cells.
• The calibration also tests for noise or unwanted
  values or densities in a homogenous image.
• The calibration will also test for low contrast
  resolution. CT imaging should distinguish 200
  shades of gray. This is vital for distinguishing
  different types of tissue.
• Calibration also tests for slice thickness as
  well as the positioning of the couch (the
  movement of the table during the scan).

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Its unfortunate that there is currently no
universal standard for scanner calibration.
Thats why its important that your bio-med team
work closely with department imaging directors
and radiologists to determine the specific
protocols for your facility.
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Talk to An Expert
Are you looking for a new CT Scanner for your
practice, clinic, urgent care center or facility?
You might consider purchasing a refurbished or
used CT Scanner that offers the performance you
want at a much lower price. The experts at
Atlantis Worldwide can help you identify the
right CT Scanner for you, and guide you in
selection criteria, such as CT calibration,
warranty coverage and more. Talk to Atlantis
Worldwide today. Contact Us Today!
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Some blogs you may have missed

• Should You Buy New Or Used X-Ray and CT Tubes?
• CT Scanner Artifacts- How Do I Correct Streaks?
• The Lowdown on CT X-Ray Replacement Tubes
• Is Your CT Tube About To Fail?
• Free CT Resources
• Meet the author Vikki Harmonay

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