下垂体腫瘍の画像診断

Neuroimaging of Pituitary Neuroendocrine Tumors

Point

・成長ホルモン（GH）産生下垂体神経内分泌腫瘍（PitNET）は，下方に進展することが多い．Densely granulated typeでは，腫瘍がT2WIで低信号域となることが多い．

・副腎皮質刺激ホルモン（ACTH）産生PitNETの微小腫瘍の検出には，造影T1強調像（SPGR法）が有用である．

・プロラクチン（PRL）産生PitNETのカベルゴリンによる治療効果判定には，T2WI所見が有用である．

　Magnetic resonance imaging（MRI）is the preferred imaging technique for sellar and parasellar regions. In this study, we report our clinical experience with MRI for pituitary neuroendocrine tumors（PitNETs）with reference to histopathological findings through a review of the literature. Our previous study indicated that the three dimensional-spoiled gradient echo（3D-SPGR）sequence is suitable for evaluating sellar lesions on a postcontrast T1 weighted image（T1WI）. This image demonstrates a defined relationship between the tumor and its surroundings, such as the normal pituitary gland, cavernous sinus, and optic pathway. This 3D-SPGR sequence is also suitable for detecting microtumors in corticotroph PitNETs. In somatotroph PitNETs, the signal intensity on T2WI is important to differentiate densely granulated tumors from sparsely granulated somatotroph tumors. In lactotroph PitNETs, distinct hypointense areas in the early phase on T2WI, possibly due to diffuse hemorrhage, indicate pronounced regression of invasive macroprolactinomas during cabergoline therapy.