MR Angiography is a modern diagnostic technique based on the effect of nuclear magnetic resonance. During the procedure, the device reads electromagnetic waves received during the oscillation of the nuclei of hydrogen atoms, after which the computer converts the information received into a three-dimensional image of the zone under study. MR angiography allows to carry out studies of arteries, veins and lymphatic vessels of any localization, to carry out a detailed assessment of the state of vascular networks, to identify pathological changes in the early stages and to determine the cause of the pathology.
Types of research
Depending on the type of vessels, there are three types of MR angiography:
- Arteriography is a technique that allows you to assess the condition of the arteries.
- Phlebography or venography is a procedure during which the venous bed is examined.
- Lymphography is a method designed to study lymphatic vessels.
Taking into account the anatomical zone, the following popular types of MR angiography are distinguished:
- MRI of cerebral vessels – examination of cerebral vessels. It may also include examination of the vessels of the neck.
- MRI of limb vessels – examination of peripheral arteries and veins.
- MRI of mesenteric vessels – examination of the abdominal trunk, abdominal aorta, mesenteric arteries, hepatic artery, splenic artery and renal arteries.
- MRI of the lymphatic system is a study of lymphatic vessels.
In addition, when making a diagnosis, MRI of the spinal vessels, MRI of the heart and coronary vessels, MRI of the thoracic aorta and a number of other studies are used. Taking into account the use of a contrast agent, MRI can be native – without a contrast agent and contrast – with contrast enhancement.
MRI of cerebral vessels allows you to create detailed three-dimensional images of vascular networks and surrounding brain tissues, identify hematomas, hemorrhages, aneurysms, arteriovenous shunts and areas of circulatory disorders. MRI angiography is indicated for suspected post-traumatic intracranial hematoma, stroke, chronic cerebral ischemia with vertebrobasilar insufficiency, encephalopathy, post-traumatic or post-stroke changes, as well as with vegetative-vascular dystonia, pituitary adenoma, Parkinson’s disease and some other pathological conditions. The study can be both native and contrast.
MRI of the vessels of the extremities makes it possible to determine the structure of vascular networks, the condition, localization and interposition of the arteries and veins of the extremities, as well as hemodynamic parameters in unchanged areas and areas of pathological changes. MRI is used for atherosclerosis, vasculitis, thrombosis, chronic venous insufficiency, angiopathies of various genesis, traumatic injuries of arteries and veins, compression or germination of vessels by neoplasms, aneurysms, malformations and vascular dysplasia of the extremities. In some cases, contrast-free MRI is performed. If necessary, gadolinium contrast is used.
MRI of mesenteric vessels allows you to recreate a complete picture of the localization and structure of the abdominal aorta and the vessels departing from it and to identify various pathological changes (structural abnormalities, stenosis, occlusion, traumatic injury, etc.). MRI is prescribed for circulatory disorders in the abdominal aorta basin, with suspicion of abdominal aorta coarctation, atherosclerotic lesion of abdominal vessels, aneurysm aorta, malformations and vascular ruptures of traumatic origin. Vascular contrast can be used to increase the informative value of MRI.
MRI of the lymphatic system makes it possible to assess the condition of the entire lymphatic system and its individual areas. During the procedure, a specialist can examine lymph nodes and large collectors, as well as determine the level of fluid content in tissues, drawing conclusions about the degree of violation of lymphatic drainage function. MRI is used for lymphedema caused by inflammatory processes, oncological lesions and fibrous changes that have arisen as a result of previously transferred diseases. The purpose of the study may be to determine the stage of the process, assess the prognosis and choose the optimal treatment tactics.
The main contraindication to MRI is the presence of implanted ferromagnetic structures and electronic devices in the patient’s body. The study is not prescribed for non-removable external metal structures (Ilizarov apparatus, rod apparatuses). In addition, MR angiography is not recommended for tattoos applied using metal dyes. An intrauterine device and titanium implants are not a contraindication. Patients with installed titanium metal structures must have documents confirming the composition of the implant.
There are limitations due to the technical capabilities of the equipment. MRI is not used for weight over 120-130 kg, waist height over 32 cm and waist volume over 120-140 cm. In some cases, the problem of dimensions (but not weight) can be solved by conducting MRI using open-type devices. About 5% of patients in the course of the study experience pronounced unpleasant sensations associated with being in a confined space. To prevent a possible panic attack, such patients are also referred for MRI in open-type devices.
Relative contraindications to the procedure are severe diseases of the cardiovascular system, severe pain, hyperkinesis, impaired consciousness and other conditions that prevent the preservation of immobility. Contrast MR angiography is not prescribed during gestation, with allergies to gadolinium and with severe renal dysfunction. During lactation, patients are advised to refrain from feeding for 24-48 hours after the end of the study.
Special training is usually not required. An exception is the MRI of abdominal vessels with contrast. The patient is recommended to abstain from eating for 6 hours and from taking fluids for 1-2 hours. You should take extracts and the results of previous diagnostic studies with you. The patient is asked to undress and remove all metal objects, including dentures. Then the patient is placed on the table and a contrast agent is injected intravenously. After that, the table is pushed into the tunnel of the tomograph or the ring of the open device.
MR angiography on average lasts about half an hour. During this time, it is important to remain motionless in order to ensure high-quality images. If you experience unpleasant sensations (shortness of breath, dizziness, increased heartbeat, nausea and other symptoms that may be due to claustrophobia or intolerance to the contrast agent), you should immediately inform your doctor. The conclusion is usually prepared within 2-3 hours after the completion of the procedure and either given to the patient or handed over to the attending physician. With a heavy workload of specialists, the documents can be ready the next day.
MR angiography makes it possible to create three-dimensional images, enlarge individual parts of these images, change the viewing angle and study various slices. The advantage of the technique is wider possibilities when recreating the image of the studied area in various planes. In addition, during MRI, tissues and anatomical structures of similar density are more clearly delimited, which allows for a more accurate assessment of the severity and prevalence of pathological changes.
Unlike CT and classical angiography, MR angiography does not provide for the mandatory administration of a contrast agent. Features of the technology allow to obtain images of vascular networks without additional contrast. During MRI angiography, the specialist sees not only the arteries and veins, but also the surrounding soft tissues. Contrast is used according to indications to improve the quality of visual information when recognizing certain pathological conditions (for example, oncological lesions). Another advantage of MR angiography is the absence of X-rays. The technique can be used even when examining young children and pregnant women (with certain restrictions).