Lymph node imaging

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Lymph node imaging is a useful technique, aiding the clinician in determining whether nodes are benign or malignant. Multiple modalities are used for the assessment and characterization of lymph nodes, each with its advantages and drawbacks.

Modalities

Ultrasound
  • size 
  • number
  • shape
  • contour
  • internal architecture
    • echotexture
    • hilum
    • cystic/necrotic change
    • calcification
  • long to short axis ratio
  • vascularity
CT
  • size 
  • shape
  • number
  • attenuation characteristics
  • enhancement with contrast
  • internal architecture
    • cystic/necrotic change
    • calcification
MRI
  • size 
  • shape
  • number
  • cystic/necrotic change
Contrast MRI 
  • enhancement kinetics 
  • flow kinetics
  • blood volume
  • microvascular permeability
Diffusion-weighted imaging
  • pending
MR spectroscopy
  • adjunct technique
  • elevated choline levels have been associated with metastatic lymph nodes
    • active research into other metabolites is ongoing
MRI with USPIO
  • promising adjunct technique using ultra small superparamagnetic iron oxide particles
  • several patterns of uptake have been defined which are helpful in the characterization of lymph nodes
Interstitial administration of lymphangiographic contrast with MRI
  • a different approach which helps in the visualization of the lymphatic system on MRI
  • helps in identification of sentinel nodes and the course of draining lymphatics
Nuclear medicine
PET
  • has gained importance in recent years in identifying small nodal metastases
  • F-18-FDG is the main radiotracer used, and it is avidly taken up by malignant cells with high rates of glycolysis