Metabolic In Vivo Visualization of Pituitary Adenomas: a Systematic Review of Imaging Modalities

Abstract

Introduction Pituitary adenomas are the most common intrasellar mass. Functional pituitary adenomas (PAs) constitute the majority of pituitary tumors and can produce symptoms related to hormonal overproduction. Timely and accurate detection is therefore of vital importance to prevent potentially irreversible sequelae. Magnetic resonance imaging (MRI) is the gold standard for detecting PAs, but is limited by poor sensitivity for microadenomas and an inability to differentiate scar tissue from tumor residual or predict treatment response. Several new modalities that detect pituitary adenomas have been proposed. Methods A systematic review of the PubMed database was performed for imaging studies of PAs since its inception. Data concerning study characteristics, clinical symptoms, imaging modalities, and diagnostic accuracy were collected. Results After applying exclusion criteria, 25 studies of imaging pituitary adenomas using positron emission tomography (PET), magnetic resonance spectroscopy (MRS), and single photon emission computed tomography (SPECT) were reviewed. PET reliably detects PAs, particularly where MRI is equivocal, though its efficacy is limited by high cost and low availability. SPECT possesses good sensitivity for neuroendocrine tumors but its use with PAs is poorly documented. MRS consistently detects cellular proliferation and hormonal activity but warrants further study at higher magnetic field strength. Conclusion PET and MRS appear to have the strongest predictive value in detecting PAs. MRS has the advantage of low cost, but the literature is lacking in specific studies of the pituitary. Due to high recurrence rates of FPAs and low sensitivity of existing diagnostic workups, further investigation of metabolic imaging is necessary.

Ex Vivo 1H NMR study of pituitary adenomas to differentiate various immunohistochemical subtypes

“…We have identified aqueous metabolites (in the methanol-water layer) and lipid components (in the chloroform layer) by analyzing 1D 1 H and 2D 1 H- 1 H TOCSY NMR spectra in combination with comparison of chemical shifts reported in the literature 3,9–15 .…”

“…PAs may interfere with normal production of one or more of the pituitary hormones as they grow and compress and/or destroy the normal pituitary gland. The growth of PAs and hypersecretion of hormones can produce a number of clinical symptoms, the consequences of which produce clinical syndromes and therapeutic challenges 3,4 . Although routine diagnostic magnetic resonance imaging (MRI) is used to diagnose most PAs, it may not detect microadenomas unambiguously.…”

“…Although both techniques are complementary to each other, NMR spectroscopy has a unique advantage of being non-destructive including its capability to translate ex vivo observations into in vivo applications using clinical MRI scanners in noninvasive diagnostics. Although NMR spectroscopy has been widely used for the characterization of brain tumors 3,9,10,11 , there has not been a detailed metabolomic investigation of various immunohistochemical subtypes of pituitary tumors. In the present study, we have characterized both aqueous and lipid metabolites that are present in PAs using ex vivo 1 H NMR spectroscopy.…”

Case Report and Literature Review: Ectopic Thyrotropin-Secreting Pituitary Adenoma in the Suprasellar Region

“…Additional imaging examinations, such as positron emission tomography/ computed tomography (PET/CT) and PET/MRI, could contribute to the evaluation of the tumor location. 18 Ffluorodeoxyglucose (FDG) PET/CT is proposed to be positive in 60-67% of cases in studies involving pituitary adenomas (27,28), which can be meaningful for detecting adenomas, especially when the MRI findings are unclear. Ishizaki et al proposed that PET/CT revealed increased FDG uptake in EPA patients (4).…”

Pituitary adenomas: current principles of diagnosis and treatment

“…Среди возможных точек приложения данных методик следует указать визуализацию невидимых на МРТ-изображениях микроаденом, а также обнаружение остаточных фрагментов опухоли и раннее выявление рецидивов. Ряд работ посвящен изучению радиофармпрепаратов, специфичных для рецепторов соматостатина ( 111 In-пентетреотид для сцинтиграфии [72], 68 Ga-DOTA-TATE для ПЭТ [73]), дофаминовых рецепторов ( 123 I-эпидеприд [74]), а также более распространенных 18 F-фтордезоксиглюкозы и 11 C-метионина [75]. По мнению A. Yao и соавт.…”