Magnetic resonance imaging (MRI) of the kidneys

The most common indication for MRI of kidneys is the diagnosis and staging of tumors. Nevertheless, CT for the same purpose is prescribed much more often. Multiple comparative studies have shown that CT and MRI can equally accurately detect neoplasm, but the latter provides additional information on the stage of the process. Usually the use of MRI is recommended as an additional diagnostic method if CT does not provide all the necessary information. MRI should replace it in those cases when it is impossible or dangerous to use radiopaque preparations due to allergies or kidney failure, as well as when radiation exposure (pregnancy) is impossible. High interstitial differentiation with MRI allows more accurate assessment of tumor invasion in neighboring organs. A number of studies confirm that a non-contrast MR-cavalography has a 100% sensitivity to the detection of tumor thrombosis of the inferior vena cava. Unlike other intrascopic methods, MRI allows you to visualize the pseudocapsule of a kidney tumor, which can be very valuable in planning organ-saving operations. To date, MRI is the most informative method for diagnosing bone metastases, which should be resorted to in observations when other diagnostic methods do not provide the necessary information or their data are questionable. MR-characteristics of bone metastasis of a kidney tumor correspond to those of the main tumor focus, which can be used in the search for a primary tumor in observations with multiple neoplasms when the origin of bone metastasis is unclear.

MRI (magnetic resonance imaging) is a highly effective method of detecting and studying the morphology of any cystic formations. This is due to the ability of the method to determine the presence of liquid on the basis of differences in the MP signal associated with long values of T1 and T2 of water. If protein or blood is present in the contents of the cyst, then the corresponding changes in the characteristics of the MP signal from the contents of the cyst are noted. MRI is the best method of diagnosing cysts with hemorrhagic contents. Because it is inherent to a shorter time T1, which causes a higher intensity of the MR signal than in a simple cyst. In addition, it is possible to trace the dynamics of hemorrhage. Blood is an excellent natural contrast agent, which is associated with the iron content in hemoglobin. The processes of transformation of the latter during hemorrhage at different stages are characterized by typical MP-pictures. The intensity of the signal from hemorrhagic cysts on T1-weighted images is higher than from simple cysts, ie. They are lighter. Moreover, on T2-weighted images, they are either hyperintensive, like simple cysts, or hypo-intensive.

In the 80-ies of the XX century. Has developed a new method of visualization of the urinary tract - magnetic resonance urography. This is the first technique in the history of urology that allows you to visualize VMP, without any invasive intervention, contrast and radiation load. Magnetic resonance urography is based on the fact that when performing an MRI in the hydrography mode, a high-intensity MP signal is recorded from a stationary or slow moving fluid located in the natural and (or) pathological structures in the study area, and the signal from the tissues and organs surrounding them. Much less intensive. At the same time, clear images of the urinary tract are obtained (especially when they are enlarged), cysts of different localization, the spinal canal. Magnetic resonance urography is indicated in cases where excretory urography is not sufficiently informative or can not be performed (for example, with retentive changes in VMP of different genesis). The introduction of MSCT into practice also allows one to clearly visualize VMP without even contrasting, narrowing the range of indications to magnetic resonance urography.

MRI of the bladder has the greatest practical value in detecting and determining the stage of neoplasm. Bladder cancer is attributed to hypervascular tumors, in connection with which the accumulation of contrast material in it occurs faster and more intensively than in the unchanged wall of the bladder. As a result of better interstitial differentiation, the diagnosis of a bladder tumor with MRI is more accurate than with KT.

MRI of the prostate best (among all intrascopic methods) demonstrates the anatomy and structure of the organ, which is especially valuable for diagnosis and clarification of the stage of cancer of the gland. Detection of foci suspicious of cancer, allows you to perform a targeted biopsy, even in cases where ultrasound suspicious areas are not identified. In this case, the maximum information is obtained only with the use of paramagnetic contrast preparations.

In addition, MRI can provide accurate information about the forms of adenoma growth, helps diagnose cystic and inflammatory diseases of the prostate and seminal vesicles.

High-quality mapping of the structure of the external genital organs with MRI can be successfully used to diagnose their congenital anomalies, injuries, staging of Peyronie's disease, testicular tumors, inflammatory changes.

Modern MP-tomographs make it possible to carry out dynamic MRI of various organs, in which, after the introduction of a contrast medium, repeatedly repeated arias of the sections of the investigated region are performed. Then, graphs and maps of the rate of changes in signal intensity in the areas of interest are plotted on the device's workstation. The resulting color maps of the rate of accumulation of contrast medium can be combined with the original MR tomograms.

Simultaneously, it is possible to study the dynamics of accumulation of contrast medium in several zones. The use of dynamic MRI increases the informative value of differential diagnostics of oncological diseases and diseases of non-tumorous etiology.

During the last 15 years, non-invasive research methods have been developed that make it possible to obtain information about biochemical processes in various organs of the body tissues, i.e. Conduct diagnostics at the molecular level. Her. The essence is reduced to the determination of key molecules of pathological processes. These methods include MR-spectroscopy. This is a non-invasive diagnostic method that allows to determine the qualitative and quantitative chemical composition of organs and tissues using nuclear magnetic resonance and chemical shift. The latter consists in the fact that the nuclei of the same chemical element depend on the molecule in which they are composed, and the positions. Which they occupy in it, reveal the absorption of electromagnetic energy in various sections of the MR spectrum. Investigation of the chemical shift implies obtaining a spectrum of the graph reflecting the relationship between the chemical shift (the abscissa axis) and the intensity of the signals (ordinate axis) emitted by the excited nuclei. The latter depends on the number of nuclei emitting these signals. Thus, when analyzing the spectrum, one can obtain information about the substances in the studied object (qualitative chemical analysis), and their quantity (quantitative chemical analysis). In urological practice, MR-spectroscopy of the prostate has spread. In the investigation of the organ, proton and phosphoric spectroscopy is usually used. When 11P of MP-spectroscopy of the prostate, peaks of citrate, creatine, phosphocreatine, choline, phosphocholine, lactate, inositol, alanine, glutamate, spermine and taurine are found. The main disadvantage of proton spectroscopy is that living objects contain a lot of water and fats that "pollute" the spectrum of interesting metabolites (the number of hydrogen atoms contained in water and fat is approximately 7,000 times greater than their content in other substances). In this connection, special methods for suppressing signals emitted by protons of water and fats have been developed. To avoid the formation of "polluting" signals also help other types of spectroscopy (for example, phosphoric). When 11P MP spectroscopy is used, peaks of phosphomonoester, diphosphodiester, inorganic phosphate, phosphocreatine and adenosine triphosphate are studied. There are reports of the use of 11C- and 23Na-spectroscopy. Nevertheless, the spectroscopy of organs deep (for example, the kidneys), while presenting serious difficulties.

[1], [2], [3], [4], [5], [6], [7], [8], [9], [10], [11], [12]