Lung MRI is a diagnostic study of the lungs and organs of the thoracic cavity, based on measuring the resonant absorption of radio waves by the nuclei of hydrogen atoms under conditions of a constant magnetic field of high voltage. It is used to determine focal formations of lung tissue, the state of lymph nodes, pleural cavity and mediastinal organs. The diagnostic value of MRI lies in the possibility of accurate differentiation of tissue and vascular structures, clarification of the shape, size, typology of tumors, determination of their germination into adjacent organs and vessels. Limitations are associated with the inability to visualize the broncho-alveolar tissue and its diffuse changes.
With lung MRI, pathological changes of the heart, trachea, large bronchi and vessels, pleura, thymus gland, esophagus are clearly visible. Therefore, the indisputable grounds for the diagnosis are suspicions of:
- pathology of the lungs of vascular genesis;
- tumors and cysts of the mediastinum;
- enlargement of intra-thoracic lymph nodes;
- pleural tumors.
In these cases, MRI allows for a clear differentiation of tissue and vascular structures, lymphoid formations, fluid accumulations and delimited formations, tumor tissue, to determine tumor invasion into mediastinal organs and major vessels. Lung MRI helps to differentiate inflammatory and other organ lesions, which makes the study promising in pulmonology, thoracic surgery and phthisiology. Lung MRI can be used to plan thoracic operations and monitor their results, if contrast computed tomography is not possible.
Circumstances precluding the possibility of lung MRI are the presence of an electrocardiostimulator, metal implants, fragments, chips, staples, ferromagnetic clips, cochlear implants. MRI is not performed when the patient is on a ventilator and the patient’s weight is over 150 kg. The possibility of magnetic tomography in patients with artificial valvular heart prostheses, cava filters, tantalum braces on the sternum is decided by a radiologist performing the study. The relative limitations of MRI are cases of decompensated heart failure; early postoperative period after the installation of metal endovascular stents, occluders, spirals; pregnancy, claustrophobia, schizophrenia, epilepsy; inability of the patient to maintain a stationary state during the study.
Methodology of conducting
Lung MRI does not require restrictions in food intake and preliminary preparation. Before the procedure outside the room with a tomograph, the patient is asked to remove clothes with metal parts (buttons, zippers, buckles, buttons, hooks), belts, watches, jewelry, etc. There should be no magnetic or electronic devices in the pockets of the patient’s clothes: mobile phones, iPods, coins, flash cards, magnetic cards. Such objects are not only irreversibly damaged in the magnetic field zone, but can also interfere with the operation of the MR tomograph.
During lung MRI, which lasts 30-40 minutes, the subject should lie motionless on a table placed in the tunnel of a magnetic tomograph. During the scan, the tomograph emits a rhythmic tapping, which is a feature of the device. If it is necessary to use contrast in the process of lung MRI, the patient is injected intravenously with gadolinium.
With MRI, sections about 10 mm thick are obtained, not only horizontal, but also sagittal and frontal, allowing a detailed study of the tops of the lungs, spine, costal-diaphragmatic sinuses. When assessing the diagnostic capabilities of MRI, it is noted that this technique is most accurate in identifying additional formations of central localization and is inferior to CT of the lungs in the case of recognition of peripheral syndromes. With the help of lung MRI, mediastinal tumors, coelomic cysts of the pericardium, abdominal-mediastinal lipomas are accurately determined; conditions associated with the germination of tumors into the pericardium, diaphragm, esophagus, large bronchi and vessels, changes in the pleura or the presence of even a small amount of pleural effusion.