Imaging of pituitary pathology.

Modern imaging techniques play a vital role in the diagnosis, surveillance, and treatment monitoring of patients with pituitary disease. For its high soft tissue contrast, magnetic resonance (MR) imaging provides detailed information about the localization and extent of a lesion. It is thus, to date, the most important imaging technique for documenting or ruling out structural lesions. It is usually the first and only imaging procedure to be employed in pituitary pathology. While large pituitary adenomas are reliably depicted in standard T1-weighted sequences, small microadenomas, such as in Cushing's disease, may only become visible if repeat studies, sophisticated techniques and high-field scanners are employed. For monitoring treatment effects after surgical procedures, drug applications, or irradiation, follow-up studies with identical parameters should be employed, preferably at the same investigation site. Some space is devoted to intraoperative imaging, which not only allows assessment of how radical tumor resection needs to be during pituitary tumor surgery, but also provides extremely accurate structural data for neuronavigation. Less frequent lesions, such as craniopharyngiomas, meningiomas, germ cell tumors, gliomas, skull base tumors, hypothalamic hamartomas, vascular malformations, inflammatory and developmental lesions and other, even less frequent pathologies should be considered in the differential diagnosis. The particular strength of computed tomography (CT) is the direct depiction of calcification, a weakness of MRI, and the high resolution of bone structures at the skull base. This chapter presents the characteristics of both frequent and less commonly encountered tumoral lesions, with an emphasis on computed tomography and magnetic resonance imaging.