signal on T2-Weighted and T1-Weighted Magnetic Resonance Images

Causes of Low Intensity in Tumors on T2-Weighted Magnetic Resonance Images

Paramagnetic effects    Iron within dystrophic calcification or necrosis    Ferritin/hemosiderin from prior hemorrhage    Deoxyhemoglobin in acute hemorrhage    Intracellular methemoglobin in early subacute hemorrhage    Melanin (or other free radicals) Low spin density    Calcification    Scant cytoplasm (high nucleus:cytoplasm ratio)    Dense cellularity Fibrocollagenous stroma Macromolecule content Very high (nonparamagnetic) protein concentration Intratumoral vessels    Signal void from rapid flow

Causes of High Intensity in Tumors on T1-Weighted Magnetic Resonance Images

Paramagnetic effects from hemorrhage Subacute-chronic blood (methemoglobin) Paramagnetic material without hemorrhage Melanin Naturally occurring ions associated with necrosis of calcification    Manganese    Iron    Copper Nonparamagnetic effects Very high (nonparamagnetic) protein concentration Fat Flow-related enhancement in tumor vessels