Pituitary CT, along with MRI, is the leading method of imaging pituitary adenomas (prolactinomas, somatotropinomas, prolacto-corticotropinomas, prolactosomatotropinomas), as well as hormone-inactive (“mute”) tumors. With CT of the pituitary gland, topography, dimensions, glands are evaluated; the presence of additional formations, their size and structure (solid, cystic), spreading beyond the Turkish saddle, germination into bone structures and hard membranes of the brain. When performing a CT scan of the pituitary gland, it is advisable to use high resolution and contrast enhancement.
Pituitary CT is not fundamentally different from other types of computed tomography. As is known, the basis of this method is to obtain layered images of the studied area in the axial plane. This is achieved by moving the source and detector of X-ray radiation around the human body – when passing through tissues of different densities, the intensity of the X-ray beam changes, which is recorded by detectors. The received fluctuations in the radiation intensity are processed by a computer, and a layered image is reconstructed on their basis. The peculiarity of the pituitary CT is the need to use very precise modern equipment capable of ensuring the thickness of the resulting sections of no more than one millimeter – this is due to the insignificant size of the organ and the thinness of its structure.
For this reason, pituitary CT stood out as a separate type of diagnostic procedure much later than the advent of computed tomography in general. Before the advent of high-precision tomographs capable of taking pictures of the thinnest sections of tissues, the pituitary gland area (Turkish saddle) was studied as part of the study of the brain as a whole. At the same time, only pronounced violations of the structure of this organ or significant neoplasms comparable in size to the size of a Turkish saddle could be detected. To date, pituitary CT is gradually gaining popularity in the field of oncology and endocrinology as a modern and fairly accurate diagnostic method.
Only magnetic resonance imaging of this organ can compare the diagnostic value of the information obtained with the CT of the pituitary gland. Moreover, many researchers consider it the best method of diagnosis. However, MRI is somewhat more expensive than CT of the pituitary gland, in addition, it is impossible to conduct it if metal implants (for example, orthopedic or dental) and electronic devices (pacemakers) are present in the body of the subject. The reason for distinguishing between CT of the pituitary gland and computed tomography of the brain as a whole is the desire to reduce the radiation load on the patient’s body – with an isolated study, it is several times lower.
Since the pituitary gland is the central organ of the human endocrine system, most often the reason for its study is a variety of hormonal disorders and their manifestations. So, indications for CT of the pituitary gland may be diabetes mellitus, growth retardation or, on the contrary, gigantism and acromegaly, decreased activity of the sex glands (hypogonadism) with the development of characteristic symptoms. These complaints can be caused by both primary damage to the neuroendocrine organ, and the consequence of other inflammatory, neoplastic, endocrine disorders. It is for the differentiation and diagnosis of these disorders that a pituitary CT is used.
Another frequent indication for pituitary CT is a suspicion of a tumor process, which can be accompanied by both the above endocrine symptoms, as well as visual disturbances, headaches and other manifestations. Sometimes tumors of this organ are detected accidentally on an X-ray of the skull by expanding the area of the Turkish saddle – this also serves as a reason for the appointment of a pituitary CT. Sometimes such a study is necessary after traumatic brain injuries to detect possible lesions of the pituitary gland and the base of the skull, as well as in some inflammatory diseases (for example, meningitis).
There are very few absolute contraindications for native pituitary CT – these include pregnancy, especially in the early stages, and excessive obesity (this is due to the limitations imposed by the capabilities of the equipment). When using intravenous contrast, the list of contraindications expands – in this case, a pituitary CT scan cannot be performed with renal insufficiency, hyperthyroidism, allergies and other forms of intolerance to iodine and radiopaque drugs.
Preparation for pituitary CT
As a rule, the study is prescribed by an endocrinologist, who is guided by the results of determining the level of hormones in the blood and the presence of other symptoms of damage to this organ. In addition, a neurologist or oncologist can issue a referral for this procedure. Prior to conducting a native pituitary CT, preliminary preparation is not required, in case of contrast, it is recommended to limit the amount of food consumed on the eve and perform an examination on an empty stomach. In a medical institution, immediately before computed tomography, allergic tests for radiopaque drugs can be carried out, in the presence of unusual skin reactions (itching, burning, redness), the use of contrast is prohibited.
Methodology of conducting
The subject must remove metal jewelry (in order to avoid the appearance of artifacts in the pictures) and lie down on the CT scanner table, after which his head is fixed and placed inside the ring-shaped opening of the device. Since a pituitary CT scan is an extremely delicate examination, it is very important to remain motionless during the scan. If necessary, contrast is injected intravenously into the patient and the procedure is started. Usually, a full scan of the examined area with a pituitary CT takes only a few minutes, the same amount of processing of the received data and the formation of slice images is carried out. The results obtained are recorded on digital media or printed on film and can be given to the patient or transferred to a specialist for their study and interpretation.
Interpretation of results
With native pituitary CT, the main parameters are the size and position of the organ, the presence or absence of neoplasms in it, their size, nature and relationship with surrounding tissues. Statistically, various cystic tumors (adenomas) are found more often in the pituitary gland, which are combined with a variety of endocrine disorders. Solid tumors in their structure, detected by CT of the pituitary gland, are often hormonally “mute”, that is, they do not produce an increased amount of hormones. Since in most cases tumors have high metabolic activity, they accumulate an increased amount of contrast, therefore, computer tomography with contrast is used to detect them.
An important diagnostic and prognostic characteristic of neoplasms detected by pituitary CT is their relationship with surrounding tissues. An unfavorable prognosis is characterized by tumors with infiltrating growth, sprouting into the dura mater, the bones of the base of the skull, and brain structures. Pituitary neoplasms with expansive growth can lead to compression of surrounding structures, but in general they are more favorable. The type and nature of tumor growth is easily determined by CT of the pituitary gland with contrast, so this diagnostic technique is extremely important for choosing tactics for further treatment in oncology. It can also be used to detect pituitary injuries, hemorrhages as a result of damage to its vessels and a number of other pathological conditions.