Aliasing artifact (CT)

Andrew Murphy ◉ et al.

Aliasing artifact, otherwise known as undersampling, in CT refers to an error in the accuracy proponent of analog to digital converter (ADC) during image digitization.

Image digitization has three distinct steps: scanning, sampling, and quantization.

When sampling, the brightness of each pixel in the image is measured, and via a photomultiplier, creates an output analog signal that is then due to undergo quantization.

The more samples that are taken the more accurate the representation of the signal will be, hence if a lack of sampling has occurred the computer will process an inaccurate image resulting in an aliasing artifact.

The artifact has the appearance of Moiré patterns.

Quiz questions

References

Imaging technology

imaging technology
imaging physics
i maging in practice
x-ray
fluoroscopy
- automatic brightness control (ABC)
computed tomography (CT)
- CT physics
- CT in practice
- CT technology
- CT image reconstruction
- CT image quality
- CT dose
- CT contrast media
- CT artifacts
  - patient-based artifacts
  - physics-based artifacts
  - hardware-based artifacts
    - ring artifact
    - tube arcing
    - out of field artifact
    - air bubble artifact
    - helical and multichannel artifacts
- CT safety
- history of CT
  - Godfrey N Hounsfield
MRI
- MRI physics
- MRI in practice
- MRI hardware
- signal processing
- MRI pulse sequences (basics | abbreviations | parameters)
- MR angiography (and venography)
  - contrast-enhanced MRA
  - non-contrast-enhanced MRA
    - phase contrast imaging
    - time of flight angiography
    - TRICKS
- MR spectroscopy (MRS)
  - 2-hydroxyglutarate peak: resonates at 2.25 ppm
  - alanine peak: resonates at 1.48 ppm
  - choline peak: resonates at 3.2 ppm
  - citrate peak: resonates at 2.6 ppm
  - creatine peak: resonates at 3.0 ppm
  - functional MRI (fMRI)
    - BOLD imaging
  - gamma-aminobutyric acid (GABA) peak: resonates at 2.2-2.4 ppm
  - glutamine-glutamate peak: resonates at 2.2-2.4 ppm
  - Hunter's angle
  - lactate peak: resonates at 1.3 ppm
  - lipids peak: resonates at 1.3 ppm
  - myoinositol peak: resonates at 3.5 ppm
  - MR fingerprinting
  - N-acetylaspartate (NAA) peak: resonates at 2.0 ppm
  - propylene glycol peak: resonates at 1.13 ppm
- MRI artifacts
  - MRI hardware and room shielding
  - MRI software
  - patient and physiologic motion
  - tissue heterogeneity and foreign bodies
  - Fourier transform and Nyquist sampling theorem
- MRI contrast agents
- MRI safety
  - magnetic shielding
  - specific absorption rate
ultrasound
- ultrasound physics
- transducers
  - linear array
  - convex array
  - phased array
  - frame averaging (frame persistence)
  - ultrasound image resolution
- imaging modes and display
  - pulse-echo imaging
  - real-time imaging
  - Doppler imaging
    - Doppler effect
    - color Doppler
    - power Doppler
    - B flow
    - color box
    - Doppler angle
    - pulse repetition frequency and scale
    - wall filter
    - color write priority
    - packet size (dwell time)
    - peak systolic velocity
    - end-diastolic velocity
    - resistive index
    - pulsatility index
    - Reynolds number
  - panoramic imaging
  - compound imaging
  - harmonic imaging
  - elastography
  - scanning modes
    - 2D ultrasound
    - 3D ultrasound
    - 4D ultrasound
    - M-mode
  - ultrasound artifacts
    - acoustic shadowing
    - acoustic enhancement
    - beam width artifact
    - reverberation artifact
      - comet tail artifact
        color comet tail artifact
    - ring down artifact
    - mirror image artifact
    - side lobe artifact
    - speckle artifact
    - speed displacement artifact
    - refraction artifact
    - multipath artifact
    - anisotropy
    - electrical interference artifact
    - hardware-related artifacts
      - transducer
    - Doppler artifacts
      - aliasing
      - tissue vibration
      - spectral broadening
      - blooming
      - motion (flash) artifact
      - twinkling artifact
      - acoustic streaming
  - biological effects of ultrasound
    - mechanical index
    - thermal index
  - history of ultrasound
nuclear medicine
- nuclear medicine physics
  - nuclide
- detectors
  - scintillation detectors (gamma camera)
    - photomultiplier tube
  - emission tomography
    - single photon emission computed tomography (SPECT)
    - positron emission tomography (PET)
- tissue to background ratio
- radiopharmaceuticals
  - fundamentals of radiopharmaceuticals
  - radiopharmaceutical labeling
  - radiopharmaceutical production
    - nuclear reactor produced radionuclides
    - cyclotron produced radionuclides
  - radiation detection
    - dosimetry
  - specific agents
    - carbon-11
    - chromium-51
    - fluorine agents
    - gallium agents
      - Ga-67 citrate
      - Ga-68
        Ga-68 DOTATATE
    - iodine agents
      - I-123
        
        I-123 iodide
        
        I-123 ioflupane (DaTSCAN)
        
        I-123 ortho-iodohippurate
      - I-131
      - MIBG scans
        
        I-123 MIBG
        
        I-131 MIBG
    - indium agents
      - In-111 Octreoscan
      - In-111 OncoScint
      - In-111 Prostascint
      - In-111 oxine labeled WBC
    - krypton-81m
    - nitrogen-13
    - oxygen-15
    - phosphorus-32
    - selenium-75
      - SeHCAT
    - technetium agents
      - Tc-99m DMSA
      - Tc-99m DTPA
      - Tc-99m DTPA aerosol
      - Tc-99m HMPAO
      - Tc-99m HMPAO labeled WBC
      - Tc-99m MAA
      - Tc-99m MAG3
      - Tc-99m MDP
      - Tc-99m mercaptoacetyltriglycine
      - Tc-99m pertechnetate
      - Tc-99m labeled RBC
      - Tc-99m sestamibi
      - Tc-99m sulfur colloid
      - Tc-99m sulfur colloid (oral)
    - thallium-201 chloride
    - xenon agents
      - Xe-127
      - Xe-133
  - in vivo therapeutic agents
- pharmaceuticals used in nuclear medicine

Article information

rID: 52109

Section: Radiography, Imaging Technology

Tag: cases, cases, snippet title

Synonyms or Alternate Spellings:

Aliasing artefact (CT)

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