Radiological Investigations for Suspected Acromegaly
MRI of the sella turcica with dedicated pituitary protocol is the gold standard radiological investigation for patients with suspected acromegaly. 1, 2, 3
Primary Imaging Recommendation: MRI Sella
MRI using high-resolution pituitary protocols should include both pre-contrast (T1 and T2) and post-contrast-enhanced (T1) thin-sliced sequences with focused field-of-view targeting the sellar and parasellar regions. 1, 2 This approach provides:
- Direct visualization of the pituitary gland on non-contrast sequences, with IV contrast increasing conspicuity of small adenomas (typically appearing as hypoenhancing lesions) 1, 2
- Superior sensitivity compared to CT for detecting pituitary pathology, even with optimized CT technique 2
- Better demonstration of cavernous sinus invasion, which is critical for surgical planning 2
Enhanced MRI Techniques
Consider volumetric gradient (recalled) echo sequences after contrast administration, as these increase sensitivity for adenoma detection. 2 The American College of Radiology notes that spoiled gradient-echo 3-D T1 sequences show increased sensitivity for detecting hormone-secreting adenomas. 1
3-Tesla MRI provides better anatomical delineation and enhances surgical planning compared to standard field strength imaging. 2
Role of CT Imaging
CT is not recommended as first-line imaging for acromegaly due to limited sensitivity compared to MRI. 1, 2 However, CT has specific limited applications:
- CT can identify large pituitary tumors and demonstrate sellar remodeling (enlargement, bony erosion, suprasellar extension, clival invasion, or sphenoid sinus involvement) 1
- CT may be useful for evaluating bony anatomy prior to transsphenoidal surgery 2
Advanced Vascular Imaging
CTA or MRA are not routinely indicated for initial evaluation of suspected acromegaly. 1 These modalities may be reserved for:
- Operative planning or image guidance when vascular lesions are suspected 1, 2
- Better definition of vessel displacement or encasement in surgical planning 2
Invasive Diagnostic Procedures
Petrosal sinus venous sampling is reserved exclusively for cases where definite hormone excess is present, medical management has failed, cross-sectional imaging is negative or equivocal, and surgery is planned. 1 This invasive procedure is not part of routine diagnostic workup. 1
Clinical Pitfalls and Caveats
Hormone-secreting pituitary tumors are more commonly microadenomas (<10 mm), highlighting the absolute need for high-resolution, focused field-of-view, and thin-section imaging. 1 Standard brain MRI protocols are insufficient.
Gadolinium contrast should be used with caution in patients with renal impairment (eGFR <30 ml/min/1.73m²). 2
Plain radiography of the sella is insensitive and nonspecific, as pituitary adenomas are frequently associated with normal sella size, and should not be used. 1
Complementary Diagnostic Workup
While not strictly radiological, the diagnostic algorithm for acromegaly requires: