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