On brain MRI, pituitary adenoma is characterized by a large mass with heterogeneous signal. Other findings may include remodeling of the floor of the sella and deviation of the pituitary infundibulum to the opposite side.

• MRI is the mainstay of imaging for pituitary microadenomas
• Contrast enhanced MRIs have a sensitivity of 90%.^[1]

• Subtle morphology changes can be identified on non-contrast images, these changes include:

• Bulkiness of the pituitary gland on the side of the microadenoma

• Remodeling of the floor of the sella

• Deviation of the pituitary infundibulum away from the adenoma

• T1

• T1 is usually shows isointense to normal pituitary gland.

• T1 C+ (Gd)

• Dynamic sequences demonstrate a rounded region of delayed enhancement compared to the rest of the gland.

• Delayed images are variable, ranging from hypo-enhancement (most common) to isointense to the rest of the gland, to hyperintense (retained contrast).

• T2

• T2 is variable, but often shows a little hyperintensity.

Patient #1: Pituitary mircoadenoma

• 
  Pituitary microadenoma on T1.^[2]
• 
  Pituitary microadenoma on T2.^[2]
• 
  Pituitary microadenoma on T1.^[2]
• 
  Pituitary microadenoma on T2.^[2]

Patient #2: Pituitary mircoadenoma

• 
  T1 C+ demonstrating a pituitary microadenoma, seen as a rounded expansion of the gland to the right of the midline slightly displacing the stalk to the left. On post contrast images it enhances less than the surrounding pituitary.^[3]

• T1

• T1 typically isointense to grey matter

• Larger lesions are often heterogeneous and vary in signal due to areas of cystic change, necrosis, or haemorrhage.

• T1 C+ (Gd)

• A solid component demonstrates moderate to bright enhancement.

• T2

• T2 typically isointense to grey matter

• Larger lesions are often heterogeneous and vary in signal due to areas of cystic change, necrosis, or haemorrhage.

• T2 gradient echo parameters

• Most sensitive for detecting any haemorrhagic components, which appear as areas of signal loss.
• Calcification is rare, but should be excluded by reviewing CT scans.

Patient #1: Pituitary macroadenoma

• 
  There is a well defined round lesion noted in the pituitary fossa, the lesion is homogeneous and isodense on T1.^[5]
• 
  There is a well defined round lesion noted in the pituitary fossa, the lesion shows homogeneous contrast enhancement.^[5]
• 
  There is a well defined round lesion noted in the pituitary fossa, the lesion is homogeneous and isodense on T1.^[5]
• 
  There is a well defined round lesion noted in the pituitary fossa, the lesion is slightly hyperintense on axial FLAIR.^[5]
• 
  There is a well defined round lesion noted in the pituitary fossa, the lesion is homogeneous and isodense on T2.^[5]

Patient #2: Pituitary marcoadenoma

• 
  There is a well defined homogeneously enhancing lesion in the pituitary fossa on Sagittal T1 C+ suggestive of pituitary adenoma.^[5]
• 
  There is a well defined homogeneously enhancing lesion in the pituitary fossa on Axial T1 C+ suggestive of pituitary adenoma.^[5]