Pituitary MRI is a method of obtaining a three-dimensional image of the pituitary gland and nearby structures: the sella turcica, funnel, optic nerve intersection and others. The study is in demand in the diagnosis of benign and malignant tumors, cysts and abnormalities of the pituitary gland structure, empty sella turcica syndrome. There are two options for the procedure: native and with artificial contrast.
Before an MRI of the pituitary gland, the patient must remove all products that have metal elements: dentures, braces, clothes with metal fasteners, accessories. It is necessary to warn the doctor about the metal devices inside the body (pacemaker, hearing aid, implant, pin). If the procedure involves the introduction of a contrast agent, in addition to the above measures, it is recommended to refrain from eating for 5-8 hours.
Native pituitary MRI is performed if necessary to determine the location and size of the gland. The result may indicate the presence of a medium or large tumor, cyst. Contrast examination more clearly visualizes the pituitary gland structure, reveals small neoplasias, in particular, microadenomas. The normal gland in the frontal representation is a rectangular formation, the lower edge of which corresponds to the shape of a sella turcica, and the upper one can be convex, horizontal or concave. The length and width are 10-17 mm, height – from 3 to 8 mm. With the help of MRI, the following pathologies are diagnosed:
- SPTS. In patients with empty sella turcica syndrome, tomograms show a thinned gland distributed along the bottom of the bone structure. In the images in the anteroposterior projection, the pituitary gland has a crescent shape, its thickness is up to 3 mm. An additional sign is the sagging of the chiasm into the depth of the saddle.
- Pituitary tumors. Tumors of the pituitary gland are intensely colored by contrast, localized in the area of the sella turcica, spread to the cerebral ventricles, nasal sinuses. Microadenomas are up to 0.1 cm in size, medium adenomas are 0.11–0.22 cm, giant ones are more than 0.3-0.4 cm. It is possible to detect germinomas, meningiomas, craniopharyngiomas and other tumors.
- Diabetes insipidus. In patients with diabetes insipidus of unknown origin, a hyperintensive signal from the neurohypophysis is detected on MRI, which is absent in the T1 VI mode. It is possible to detect a malignant tumor or inflammatory process in the pituitary gland.
- Anomalies of the pituitary gland structure. MRI is actively used in the diagnosis of congenital anomalies of the development of this structure. According to the images, hypoplasia of the gland (reduction in overall size), hypoplasia of the anterior lobe, ectopic location of the posterior lobe, hypo- or aplasia of the leg of the gland is visualized.
- Cyst of the Ratke pocket. When visualizing the Rathke pocket cyst, the monitor displays a clearly limited medially located formation between the adeno- and neurohypophysis. The shape of the cyst is rounded, oval or dumbbell-shaped. The intensity of the MR signal is usually homogeneous.
Despite the high quality of the image obtained by MRI, the final diagnosis requires taking into account the data of a comprehensive examination of the patient. When interpreting the images, the doctor compares them with the clinical picture, the results of laboratory tests, CT and ultrasound of the pituitary gland, radiography of the sella turcica.
The key advantages of MRI are higher image clarity than with ultrasound and CT of the pituitary gland, hypoallergenic contrast agents. The disadvantages include the inability to examine patients with a body weight of more than 150 kg, as well as having devices with metal elements in the body. Currently, ultrasound and radiography have a lower cost than MRI of the pituitary gland, but tomographic examination makes it possible to detect micro-tumors and minimal changes in the structure of the gland that are not available for visualization by other methods.