MRA Head There is no relevant literature regarding the use of MRA in the initial imaging evaluation of suspected or known hyperfunctioning pituitary adenoma. MRI Sella MRI using high-resolution pituitary protocols is generally considered the gold standard for imaging the pituitary gland in cases of suspected hormone-secreting adenoma [15]. MRI can directly visualize the pituitary gland on noncontrast sequences. The addition of IV contrast increases the conspicuity of small adenomas, which are typically seen as hypoenhancing lesions [13,74,75]. MRI with IV contrast may only be performed for use in operative guidance, and should not be considered a first-line imaging test. MRI has been used to characterize tissue consistency [76] and has been used to predict response to therapy in cases of acromegaly [77]. Dynamic contrast-enhanced imaging of the pituitary is advocated by some authors for detection of microadenoma [78-80]. Additionally, recent studies have noted an increased sensitivity for spoiled gradient-echo 3-D T1 sequence in the detection of hormone-secreting adenomas [81]. Hormone-secreting pituitary tumors are more commonly microadenomas (<10 mm), highlighting the need for high-resolution, focused field-of-view, and thin-section imaging. MRI may further characterize hemorrhage within adenomas as areas of decreased signal intensity on T2- weighted images [41,60]. Venous Sampling Petrosal Sinus Petrosal sinus venous sampling is an invasive study reserved for cases in which a definite excess of pituitary hormone is present, medical management has failed, cross-sectional imaging is negative or equivocal, and surgery is planned [67]. When a significant discrepancy in hormone level, usually adrenal corticotrophic hormone, exists between the petrosal sinus and peripheral blood samples, tumor localization is very accurate [66,68].
Neuroendocrine Imaging. MRA Head There is no relevant literature regarding the use of MRA in the initial imaging evaluation of suspected or known hyperfunctioning pituitary adenoma. MRI Sella MRI using high-resolution pituitary protocols is generally considered the gold standard for imaging the pituitary gland in cases of suspected hormone-secreting adenoma [15]. MRI can directly visualize the pituitary gland on noncontrast sequences. The addition of IV contrast increases the conspicuity of small adenomas, which are typically seen as hypoenhancing lesions [13,74,75]. MRI with IV contrast may only be performed for use in operative guidance, and should not be considered a first-line imaging test. MRI has been used to characterize tissue consistency [76] and has been used to predict response to therapy in cases of acromegaly [77]. Dynamic contrast-enhanced imaging of the pituitary is advocated by some authors for detection of microadenoma [78-80]. Additionally, recent studies have noted an increased sensitivity for spoiled gradient-echo 3-D T1 sequence in the detection of hormone-secreting adenomas [81]. Hormone-secreting pituitary tumors are more commonly microadenomas (<10 mm), highlighting the need for high-resolution, focused field-of-view, and thin-section imaging. MRI may further characterize hemorrhage within adenomas as areas of decreased signal intensity on T2- weighted images [41,60]. Venous Sampling Petrosal Sinus Petrosal sinus venous sampling is an invasive study reserved for cases in which a definite excess of pituitary hormone is present, medical management has failed, cross-sectional imaging is negative or equivocal, and surgery is planned [67]. When a significant discrepancy in hormone level, usually adrenal corticotrophic hormone, exists between the petrosal sinus and peripheral blood samples, tumor localization is very accurate [66,68].