What are the imaging criteria of adrenal masses?

Size --> if >4cm in favor of malignancy CT scan --> Spontaneous density if >10UH then sus of malignancy, density with contrast high >37 at 30 min then malignancy, washout if <50% after 10 min in favor of malignancy (else 100% adenoma) MRI -->Max contrast and low washout in malignancy PET --> maybe FDG or MTO useful in case of sus