NM artefacts

Technical issues

  • Injection site will cause high radiotracer activity
  • Extravasation of injection causes uptake in lymph nodes

Equipment malfunction

  • Malfunction of gamma camera system
    • Photomultiplier tube (PMT) failure
    • Cracked or broken scintillation crystal
    • Correction matrix failure
    • Cracked crystal
    • Differences in detector sensitivity

Patient related

  • Attenuation can be caused by:
    • Objects worn by the patient e.g. belt buckles
    • Breast attenuation especially breast prosthesis
    • Diaphragmatic attenuation: especially in patients that are obese, have ascites, on dialysis
  • Patient motion causes misalignment of reconstructed images
  • Urinary contamination

Physiological uptake

  • Head and neck
    • Brain cortex
    • Waldeyer's ring
    • Salivary glands
    • Extra-ocular muscles
    • Larynx in excessive talking
  • Muscles
    • Stress-induced tension - trapezius and paraspinal muscles
    • Hyperventilation - diaphragm
    • Insulin - skeletal muscle
    • Vigorous exercise
  • GIT / GUT
    • Caecum / right colon more glucose avid
    • Renal collecting system, ureters and bladder
    • Uterine uptake in menstruation
  • Miscellaneous
    • Lactating breasts
    • Myocardial uptake post-prandially
    • Brown fat
    • Thymus in children

SPECT and PET/CT specific

  • Centre-of-rotation error
    • In SPECT, if presumed centre-of-rotation doesn't match actual axis of rotation back-projection will be affected
  • Misregistration between radionuclide and CT images
  • All CT related artefacts
  • Truncation
    • SPECT field of view is larger than CT field of view
    • No CT data available for attenuation correction of the SPECT images


Out now in paperback and on Kindle
Written by radiologists, for radiologists with plenty of easy-to-follow diagrams to explain complicated concepts. An excellent resource for radiology physics revision.


FRCR Physics Notes: Medical imaging physics for the First FRCR examination

Note: Not available in all regions.

Next page: NM quality assurance

  Send us your feedback


Buy FRCR Physics Notes in paperback or on Kindle and follow us for the latest developments and updates via social media.

Buy online
Available on Amazon


Follow on Facebook


Join 10k+ subscribers

Please note: Your email address will never be shared with any 3rd parties. It will only be used for Radiology Cafe communications. Emails are sent less than once a month on average. Read our Privacy policy for more details.