Radiological Exploration Of The Pituitary Gland PDF

THE RADIOLOGICAL EXPLORATION OF THE PITUITARY GLAND The pituitary pathology is mainly tumoral (adenomas). A growing tumor ussualy compress the bone, creates erosion and invasion of the sphenoidal bone. The normal sella turcica is delimited by the anterior, respectivelly posterior clinoidal processe...

THE RADIOLOGICAL EXPLORATION OF THE PITUITARY GLAND The pituitary pathology is mainly tumoral (adenomas). A growing tumor ussualy compress the bone, creates erosion and invasion of the sphenoidal bone. The normal sella turcica is delimited by the anterior, respectivelly posterior clinoidal processes and during tumoral expansion, these elements can be modified or can dissapear as anatomical reference point. These injuries can be visualised using X-rays, discovered by Roentgen (1895). SKULL X RAY – LATERAL X-rays pass through the body structures and project a shadow of the contents of the body onto the detectors; the projection appears in various shades of gray and only reveals bones clearly, while soft tissue just appears black. A main disadvantage is that the three-dimensional body parts are projected onto two-dimensional film, losing valuable information. The method can visualise the bonny walls of the sella turcica; the sella turcica normal diameters are: 15/12/19 mm (lenght, depth şi width). The normal image changes represents the base for pituitary adenoma diagnosis and classification. Skull X ray; white arrows show sella turcica COMPUTERIZED TOMOGRAPHY Hounsfield introduced CT in 1971. He was awarded the Nobel Prize for this invention in 1979. Principle: CT was originally proposed and used as an extension of the basic X-ray. The CT methodology uses a X-ray tube and detectors rotate around the patient, with the axis of rotation running from the patient’s head to toe. It is based on the fact that X-ray absorption is proportional to density of the structures they go through to obtain a density profile of a body slice (transverse or axial cut). Radiation detection system is composed of detection elements, such as scintillating crystals and photodiodes. Computer reconstructs the image from raw scan data then a picture is created by a cathode ray tube. CT is a low-risk procedure, but can be accompanied by allergic reaction to contrast dye. It uses more radiation than modern standard X-Ray, but still minimal amount. On CT, bone appears white; gases and liquids are black and tissues are gray. CT gives a tomodensitometric analyse of the content of sella turcica (the pituitary tissue structure). The normal pituitary gland may also have a nonhomogeneous CT appearance with intermingled lucent and dense areas. This heterogeneity is related in part to microscopic variation within the anterior and posterior lobes. A contrast dye enhances the image contrast and faciltates the delimitation of tumors by the surrounding tissue. CT -Normal pituitary gland CT – Pituitary adenoma MAGNETIC RESONANCE IMAGING (MRI) uses the magnetic properties of hydrogen and its interaction with a large external magnetic field. MRI is performed with examined part of the patient centered in a magnetic field much stronger than the field generated by the earth or by a normal magnet. In this case, most hydrogen atoms (protons) contained in body water tend to fall into line with this magnetic field. The second step is to apply pulsed radio waves of short duration to modify proton orientation. Protons have the tendency to return to their initial alignment, with emission of radio waves of specific frequency; these radio waves are detected by an antenna placed around the patient. The energy from the radio waves is absorbed and then released in a pattern formed by the type of tissue and by certain diseases. A computer translates the pattern of radio waves given off by the tissues into a very detailed image of parts of the body. A contrast material might be injected to improve the quality of the image. MRI views may be obtained in any plane of space, whereas CT-scan native images are only transverse. MRI does not generate any X-rays and no harmful biological effects have ever been proved under standard examination conditions. However, magnetic field interacts with metallic objects, resulting in image degradation. As any iron object is strongly attracted by the magnet, security precautions need to be respected as mentioned above. MRI is the best imaging test to identify pituitary tumors of all types. MRI can identify a macroadenoma of the pituitary gland, as well as most microadenomas. But the MRI may not be able to detect microadenomas that are smaller than 3 mm. Advantages of these systems are a relatively low cost, no electricity, no irradiation. Between 5% and 25% of healthy people have some minor abnormality of the pituitary gland that shows up on an MRI scan. Normal head MRI showing a sagittal view through the pituitary gland. The large arrow indicates the anterior portion of the pituitary gland, whereas the small arrow indicates the posterior (normally whiter) portion of the pituitary gland. (B) Coronal head MRI with posterior pituitary bright spot noted ectopically at the base of the hypothalamus (arrow). (C) Sagittal MRI view of an infant pituitary gland showing a transected hypothalamic-pituitary stalk (arrow). URINARY AMYLASE DETERMINATION PRINCIPLE: Amylase is filtered by kidney and can be eliminated by urine. In acute pancreatitis the hyperamylasemia is characterised by an increased activity in plasma of pancreatic amylase. In this disease, the activity of the pancreatic amylase varies within wide limits, from within the reference range to more than 50 times the upper reference limit, according to the functional state of the pancreas, the severity, and cause of the inflammation. During the following 4 -10 days the pancreatic amylase activity gradually decreases to normal level. The half-time of pancreatic isoamylase activity in plasma is about 12 hours. The same profile appears in urine and can be determined using the Wohlgemuth method. Anyway, due to variation of the diuresis the reference ranges for analytes in urine are much wider than the corresponding ranges in plasma. Thus, it must be concluded that urine has some disadvantages as compared to plasma/serum as system for determination of amylase activity In chronic pancreatitis with exocrine pancreatic insufficiency the amylase is greatly decreased. MATERIALS – 10 test tubes, urine, starch solution 1%0, Lugol solution PROCEDURE: In the first tube add 2 ml of urine, and in the other 9 add 1 ml of NaCl 0,9% in each. From the first tube take 1 ml of urine and add it into the second one; than take 1 ml from the second and add it into the third one and continue to obtain progressive dilutions of urine in all test tubes. Discard 1 ml from the last tube test. In this way you will obtain next dilutions: 1/1. 1/2, 1/4., 1/8, 1/16, 1/32, 1/64, 1/128, 1/256, 1/512. In each tube add 2 ml of starch solution 1%0 (which means 2 mg of starch) and put the tube sat thermostate at 37ºC for 30 minutes. After 30’ cool the tubes under cold water and add 4 drops od iodide solution each. The test tubes containing the undigested strach will be blue, instead the tubes with digested starch will be colorless. Note the last colorless tube , which contains enough amylase to digest 2 mg of starch. Express the result in Wohlgemuth units.  One Wohlgemuth Unit represents the amount of amylase which can hydrolyse 1 mg of starch at 37ºC in 30 minutes. It means that the noted tube test contains 2 WU. If this tube is the sixth, the dilution is 1/32. If this dilution of 1/32 contains 2 UW, it means that the undiluted urine contains 2x32 = 64 UW. The amylase determination has to be done in 24 h urine. The normal value for urinary amylase is 32-64 UW and for plasma amylase is 16-32 UW. 1 2 3 4 5 6 7 8 9 10 ROSENBACH REACTION (BILE PIGMENTS IDENTIFICATION) MATERIALS – filter paper, bile pigments solution (bile), concentrated nitric acid HNO3, sodium nitrite cristals (NaNO2) PROCEDURE: drip 2-3 drops from bile solution on the filter paper. In the middle of the spot add 1 drop of nitrogen acid. Around the last drop. Some concentric rings appear: yellow- red, violet-blue and green. The last one is characteristic for bilirubin presence. THYROID SCINTIGRAM The method represents a nuclear medicine investigation. Different types of nuclear medicine are: histogram mode, list mode, synchronized recordings and three dimensional reconstruction (SPECT and PET). Histogram Mode: In this mode the viewing area of the gamma camera is divided into a matrix of picture elements (pixels). The pixels become darker (or more red) by adding more pictures of the same place by time. This method can be used to examine the activity distribution in the target organ. Histogram mode is based on a predefined time interval. Three Dimensional Reconstruction: In this mode images obtained with a rotating gamma camera (multiple two dimensional) will be processed to render a three dimensional image similar to the process in CT scan. The procedure is called single photon emission computed tomography (SPECT). A more accurate way to obtain two and three dimensional images is positron emission tomography (PET) where positron emitting isotopes are used. These isotopes combine quickly with an electron and two gamma quanta are emitted in opposite direction. By detecting both quanta the location of the emission can be measured. For the thyroid scintigram, the histogram mode is most used. Principle: During nuclear medicine examination, the radioactive labeled material is injected. The radiation of the radioactive material can be detected by a gamma-camera which is sends the information to a computer for further processing.It is better to use an isotope with a relatively short half-life. The agents used for thyroid imaging include iodine 123 (I123), iodine 131( I131), technetium( Tc 99m) pertechnetate and thallium 201(Tl 201). Scanning is performed 15 minutes after administration of technetium pertechnetate, 4 hours after administration of I123 and 24 to 72 hours after administration of I 131 agents. Scanning is performed 5 to 10 minutes after thallium Tl 201administration. The patient is immobilized in a comfortable position and the scanning tube is run over the neck or other area where functioning tissue is thought to be present. The following information can be obtained from a thyroid scintigram: (1) approximate size and weight of the thyroid gland; (2) its shape (symmetric; one lobe greater than the other; one lobe missing, etc.); (3) distribution of activity (homogeneous; inhomogeneous); and (4) nodules recognition (including their position, size, and degree of activity). A major role of scintigraphy in the evaluation of a thyroid nodule or mass is "hot" (more uptake than the normal thyroid gland), "warm" (some activity but not as much as the normal gland), or "cold" (hypofunctioning). The risk of cancer in a hot nodule is 1 to 4% , in a warm nodule 8 to 10%, and in a cold nodule 15 to 25%. By far the majority (90%) of solitary, hot nodules on scintigraphy are benign in etiology, usually adenomas. A cold nodule is approached more aggressively because of the higher incidence of malignancy. A biopsy or aspiration is often neccessary. Another role of nuclear medicine scintigraphy is to determine whether a patient has a multinodular goiter. A goiter is simply an enlarged thyroid gland, which may be seen with hyperthyroidism or hypothyroidism. The thyroid abnormalities characteristic of Graves' disease result from the action of immunoglobulin of the IgG class on the gland. These antibodies may be directed against components or regions of the plasma membrane that include the receptor for thyroid simulating hormone (TSH) itself. The principal destabilizing factor resulting in autoimmune thyroid disease appears to be an organ specific defect in suppressor T-lymphocytes. Graves' disease is characterized by the association of thyrotoxicosis, diffuse goiter, infiltrative ophthalmopathy and occasionally infiltrative dermopathy. The infiltrative ophthalmopathy follows a course independent from the thyrotoxic component and is not influenced by the treatment. The thyroid scintigram typically shows a symmetrically enlarged gland with homogeneous tracer distribution and a prominent pyramidal lobe. Ectopic thyroid tissue is found in roughly 25% of thyroglossal duct cysts. The incidence of carcinoma within the thyroid tissue of a thyroglossal duct cyst is less than 1%. The lingual thyroid gland represents arrest of migration of the thyroid tissuewithin the tongue, usually in the midline between the circumvallate papillae and the epiglottis. A scintigram alone cannot provide a complete description of the physical structure of the thyroid gland. It only represents the distribution of activity measured over it. Thyroid scintigram