Contents
Diffusion is one of the main processes occurring in the process of metabolism of the cells of the human body. The first diffusion-weighted magnetic resonance image was built by specialists in 1985. In clinical work, diffusion magnetic resonance imaging has emerged along with 3rd generation magnetic resonance scanners. In this case, the main difference in obtaining diffusion-weighted tomograms is the “spin echo” or echo-planar pulse sequences with two different diffusion gradients, with the same amplitude and duration. To quantify the diffusion properties of water in tissues, it is necessary to build diffusion maps, where, depending on the diffusion coefficient, one can observe different colors of pixel staining. At a high rate of diffusion processes in the tissue, they become red-white, and at a low rate, they become blue-black. At the same time, the dependence of such processes on the direction is an anisotropy of diffusion, which is expressed in the fact that, for example, water molecules in the white matter of the brain can easily move along the nerve fiber, but their transverse movement is limited by the myelin sheath with low permeability.
Diffusion-weighted magnetic resonance imaging is a tomography that helps to evaluate the processes in the human body at the level of cell molecules.
Properties and applications
Diffusion-weighted MRI helps specialists see and quantify both the Brownian motion of water molecules in the intracellular and extracellular space, and the diffusion itself (that is, the passage of water molecules through cell membranes). The fact is that when various diseases occur in the human body, the permeability of such membranes can change, which provokes a violation of diffusion processes – their acceleration or slowdown. An indicator of this change is the calculated coefficient of diffusion processes, which diffusion-weighted magnetic resonance imaging helps to determine, depending on the organ or tissue being examined. With changes in this coefficient, doctors can draw conclusions about the appearance of the first signs of serious disorders in the body.
After collecting all the data during the examination, specialists prepare special maps, on which it becomes clear that different tissues are dyed in different colors from each other, as mentioned above. Based on the data of such maps, it is possible to draw conclusions about anatomical disorders in the human body, and about functional ones.
With the help of this diagnostic technique, it became possible to examine the entire body of the patient. With its help, even minimally sized cysts or tumors that occur in various organs, as well as purulent abscesses, which are characteristic of inflammatory processes and diseases, can be detected.
When performing this examination, it is important to remember that a brain scan gives a slightly more accurate picture of the examination, since when scanning the entire body, the accuracy of diagnosis may be limited by respiratory and peristaltic movements. At the same time, diffusion-weighted MRI of the brain easily detects the early stages of ischemic strokes, which allows specialists to restore blood flow in the affected tissue areas and prevent the development of a stroke. Also, this diagnosis helps in the visualization of cerebral edema, vascular thrombosis, neoplasms and other things.
Benefits of this examination for the patient
The modern method of diffusion-weighted magnetic resonance imaging is much more informative and convenient for both doctors and patients. The main benefits of this survey include:
- simplicity of the procedure, thanks to high-quality and high-precision equipment that is used for it;
- the prevalence of magnetic resonance scanners, which makes it easier to carry out the procedure when needed;
- safety of diffusion-weighted MRI, where no contrasts are used and there is no ionizing radiation that is harmful to both patients and medical workers;
- significantly lower cost of the study, in comparison with ordinary MRI;
- speed of diagnostics, which instead of 5 hours with other methods takes only about half an hour;
- thanks to the use of the latest DWIBS technology in diffusion-weighted MRI, the patient can breathe freely;
- the possibility of obtaining anatomical and functional indicators in one study.
Indications and contraindications for examination
An indication for the passage of diffusion-weighted magnetic resonance imaging is the suspicion of the occurrence of even the smallest, insignificant foci of tissue damage, metastases, neoplasms. Very well with this diagnosis, deviations that occur in the lymph nodes are visualized, since the tomograph signal passes through them perfectly. Therefore, this method is very common in the diagnosis of lymphomas. It is also used to determine the effectiveness and quality of ongoing therapy aimed at treating various tumors, and to make necessary adjustments to it, if necessary.
Since the diffusion-weighted MRI technique is very effective in diseases of various parts and systems of the human body, its results help doctors of various specializations in making diagnoses and prescribing therapy. More often than others, this examination is prescribed to patients by oncologists, cardiologists, neurosurgeons, and neurologists. To date, equipment for conducting diffusion-weighted MRI is available in many clinics, where you can get an examination very quickly.
Since diffusion-weighted magnetic resonance imaging is performed on patients without the introduction of special contrast agents, it can be performed even for people with renal insufficiency and young children, including those in the womb. The main contraindication to this diagnosis is the patient’s presence of implants and electrical devices with metal parts, such as pacemakers and insulin pumps. Since tomographs for this diagnosis are mostly closed, this type of research is difficult to carry out in people who are overweight, exceeding the allowable for a tomograph, as well as in those who suffer from severe claustrophobia. With these pathologies, it is recommended to carry out the procedure in an open circuit tomograph.
Before the tomography, the patient must remove all objects containing any metal from himself. During the procedure, the person should lie motionless inside the tomograph. The duration of tomography is affected by how many zones and areas the specialist analyzes during the procedure.
In modern medicine, diffusion-weighted magnetic resonance imaging is used as an independent diagnostic screening method, and can also be combined with other diagnostic procedures to identify various types of diseases. At the same time, the above method not only allows visualizing the obtained functional information, but also reveals changes in signals in structures that have not yet changed their size and shape, which helps specialists to anticipate the progression of diseases and increase the effectiveness of therapy.