Is a pituitary MRI with or without contrast (Magnetic Resonance Imaging) preferred to screen for a positive Adrenocorticotropic hormone (ACTH) stimulation test?

From the Guidelines

For evaluating the pituitary gland in a patient with a positive ACTH stimulation test, an MRI with contrast is preferred. This recommendation is based on the most recent and highest quality study available, which suggests that the addition of IV contrast increases the conspicuity of small adenomas, typically seen as hypoenhancing lesions 1. The use of contrast agent helps distinguish between normal pituitary tissue and potential abnormalities such as microadenomas or macroadenomas that might be causing excess ACTH production (Cushing's disease) or other pituitary pathology.

The typical protocol includes thin-slice (1-2 mm) images through the sella turcica region with both pre-contrast and post-contrast sequences. Dynamic contrast-enhanced imaging is particularly valuable for detecting microadenomas, which may show delayed enhancement compared to normal pituitary tissue. This imaging approach offers the best sensitivity for detecting pituitary lesions that could explain abnormal ACTH production, which is essential for proper diagnosis and treatment planning in patients with abnormal cortisol regulation.

Some key points to consider when evaluating the pituitary gland in a patient with a positive ACTH stimulation test include:

• The use of 3T MRI over 1.5T MRI where available, as it provides better image quality and sensitivity for detecting small lesions 1
• The potential benefit of functional imaging, although more data are needed to define its use in various clinical settings 1
• The importance of high-resolution, focused field-of-view, and thin-section imaging to detect hormone-secreting adenomas, which are often microadenomas (<10 mm) 1

Overall, the use of MRI with contrast is the preferred imaging modality for evaluating the pituitary gland in patients with a positive ACTH stimulation test, due to its high sensitivity and ability to detect small lesions and distinguish between normal and abnormal pituitary tissue.

From the Research

Pituitary MRI Screening for Positive ACTH Stim Test

• The preferred method for pituitary MRI screening for positive ACTH stim test is a topic of discussion among researchers.
• A study from 2003 2 compared the performance of spoiled gradient recalled acquisition in the steady state (SPGR) and standard T1-weighted spin echo (SE) techniques for MRI detection of adrenocorticotropin-secreting pituitary tumors, and found that SPGR had superior sensitivity (80%) compared to SE (49%).
• The study recommended the addition of SPGR to SE sequences using pituitary-specific technical parameters to improve the MRI detection of ACTH-secreting pituitary tumors.
• Another study from 2010 3 reported a method for detecting suspected ACTH-secreting pituitary tumors undetectable by conventional dynamic MRI using dynamic 3-Tesla MRI and half-dose gadopentetate dimeglumine, and found that microadenomas were detected in 100% of the patients using this method.
• A study from 1994 4 compared the value of dynamic serial CT, conventional CT, and T1-weighted MR imaging before and after injection of gadolinium in the detection of pituitary microadenomas, and found that the combination of T1SE-Gd with T1SE+Gd improved the sensitivity to 94% and 82% respectively.

Use of Contrast in Pituitary MRI

• The use of contrast in pituitary MRI is important for detecting ACTH-secreting pituitary tumors.
• A study from 2010 3 found that using half-dose gadopentetate dimeglumine increased the sensitivity of MRI detection of ACTH-secreting pituitary tumors.
• Another study from 1994 4 found that the combination of T1SE-Gd with T1SE+Gd improved the sensitivity of detecting pituitary microadenomas.
• However, the optimal strategy for surveillance imaging of pituitary adenomas, including the use of contrast, is not clearly established 5.

Imaging Protocols

• The imaging protocol for pituitary MRI screening for positive ACTH stim test may vary depending on the specific clinical scenario.
• A study from 2025 6 proposed an imaging algorithm for postoperative MRI following transsphenoidal pituitary adenoma resection, including the use of fat-suppressed T1 and T2 sequences.
• Another study from 2003 2 recommended the use of SPGR and SE sequences with pituitary-specific technical parameters to improve the MRI detection of ACTH-secreting pituitary tumors.