Table 2 How to differentiate CNS PTLD from other pathologies

GBM

  ◦ High perfusion in the enhancing mass

  ◦ More commonly will be a single enhancing lesion, around 2/3 of the time

  ◦ More common involvement of the corpus callosum

  ◦ Peritumoral region can have abnormalities indicating tumor (increased perfusion, restricted diffusion, tumor spectroscopy)

Abscess

  ◦ High diffusion signal centrally with relative restricted ADC

  ◦ Low diffusion signal in the rim with elevated ADC

  ◦ Thin smooth rim of enhancement with thin rim of low T2 signal

  ◦ Smooth rim of hypointensity on susceptibility weighted images

  ◦ Spectroscopy—amino acids present in the abscess cavity ((valine, leucine and isoleucine; 0.9 ppm), acetate (1.9 ppm), alanine (1.5 ppm), and succinate (2.4 ppm))

Metastatic disease

  ◦ High perfusion in the enhancing mass

  ◦ Tend not to occur in the basal ganglia, thalami, or periventricular locations