Lymphoscintigraphy is a minimally invasive functional examination of the lymphatic system with the introduction of a radionuclide substance and subsequent fixation of its passage through the lymphatic channel using a special scanning device. It is carried out to determine the features of the structure of lymphatic vessels, the rate of lymph flow, the structure of lymph nodes in traumatic, inflammatory, less often – congenital pathologies. Lymphoscintigraphy is also used to prepare for operations on lymphatic and blood vessels and for oncological interventions (when the spread of cells with lymph flow to the nearest lymph nodes is important). It is carried out on an outpatient basis without special training.
Radionuclides have been used in diagnostics since the middle of the XX century. The scintillation gamma camera for fixing radiation was invented later, since then it has become possible to conduct lymphoscintigraphy, as well as similar studies of blood vessels and various internal organs. The procedure can be prescribed for many pathologies, but the equipment is available in a small number of medical institutions, which limits the possibilities of using the method. The technique has high accuracy only with severe insufficiency of the lymphatic system. At the initial stages of lymphedema, the error in the display of vessels is of great importance, the images are unclear due to the peculiarities of radiation fixation. Lymphoscintigraphy is more often used in vascular surgery, oncology and traumatology, used for diagnostic purposes, to prepare for operations and evaluate the effectiveness of therapy.
In addition to lymphoscintigraphy, the state of the lymphatic system can be assessed using anthropometry, ultrasound, lymphography, MRI. Anthropometry allows us to suspect a pronounced insufficiency of the function of lymphatic vessels, but in the initial stages of lymphedema, the volume of the affected limb may not increase. Ultrasound diagnostics makes it possible to determine the localization and severity of edema, but in general, the method is not very accurate and is used only for quantitative assessment. The most accurate way to diagnose the state of the lymphatic system is MRI. In this case, layer-by-layer scanning is possible to obtain high-definition images even in the early stages of diseases. The advantage of lymphoscintigraphy is the ability to assess the state of the lymphatic system in dynamics.
Lymphoscintigraphy is prescribed to determine the usefulness of lymphatic drainage function and the condition of the collectors of the lymphatic system. Violation of lymph outflow occurs in chronic venous insufficiency, limb injuries, burns with subsequent scar formation, inflammatory diseases (for example, erysipelas), and also often occurs in the presence of overweight and chronic heart failure. Lymphoscintigraphy is performed in preparation for mastectomy and other oncological surgical interventions to determine the pathways of lymph outflow. During the procedure, the condition of the lymphatic vessels is assessed, the presence of collaterals is detected, etc. The results of the study influence the tactics of surgical intervention, and also allow to identify possible metastases in regional lymph nodes. In the postoperative period, lymphoscintigraphy is necessary to monitor the state of the lymphatic bed and the effectiveness of tumor treatment.
The procedure is contraindicated during pregnancy, since it is associated with the introduction of radioactive nuclides, which can have a teratogenic effect. In persons with severe somatic pathology and elderly patients, there is a risk of deterioration after gamma loading, therefore, lymphoscintigraphy in such cases is carried out only for vital indications. A contraindication is also intolerance to radionuclide drugs.
Preparation for lymphoscintigraphy
The procedure is performed according to the appointment of an oncologist, traumatologist, vascular surgeon. Previously, anthropometric confirmation of limb edema or ultrasound examination of this area, vascular ultrasound in vascular insufficiency is necessary. Special preparation for lymphoscintigraphy is not required. The allergological history and the list of medications taken are being clarified. If the patient is being treated with tricyclic antidepressants, calcium antagonists and some other antihypertensive agents, as well as sympathomimetics and adrenostimulants, this treatment is recommended to be discontinued a few days before the study.
Methodology of conducting
Lymphoscintigraphy is performed on an outpatient basis. The patient lies on his back, the specialist injects the patient with a radionuclide drug. Labeled albumin, labeled dextran, colloidal solution and other substances are used, depending on the area and purpose of the study. Contrast is injected subcutaneously into the area of the interdigital spaces: the first – during the examination of the lower extremities, the second – on the upper extremities. During lymphoscintigraphy, it is recommended to repeat certain exercises: flexion and extension of limbs, walking on stairs, etc. This is necessary for the rapid entry of the radiopharmaceutical into the lymphatic channel.
Lymphoscintigraphy is a series of images obtained using a special scintigraphic scanning technique at certain intervals, usually 5, 10, 30 minutes and 3 hours after administration of the drug. In a short time from the beginning of the procedure, an assessment of the local reaction in the area of administration is carried out. There is always an anti-shock kit for allergy relief in the office. Complications during lymphoscintigraphy are extremely rare. The results of the study are prepared within one or several days, in emergency cases, data processing and interpretation take several hours. It is possible to record on a digital medium.
Interpretation of results
Interpretation of the results of the study begins with a visual assessment of the place of contrast injection. Next, the number, size of vessels and the timeliness of their filling with radiopharmaceutical are determined. The same applies to regional lymph nodes. Thus, with lymphoscintigraphy of the lower extremities, popliteal lymph nodes are usually visualized 2 minutes after administration of the drug, inguinal – after about 7.5 minutes. The accumulation of isotope in the lymph nodes is calculated as a percentage of the injected drug, taking into account the thickness of the tissues, which can be determined using ultrasonography. The specialist also evaluates the symmetry of filling the vessels on both sides and establishes the presence of collateral lymph flow, which is one of the signs of a block in the main lymphatic vessel.
During the assessment of lymphoscintigraphy readings, the so-called transport index is calculated according to a special table. This indicator is formed based on the assessment of transport kinetics, the type of isotope propagation, the time of its appearance in the lymph nodes, as well as the state of the lymph nodes and lymphatic vessels. Normally, the transport index should not exceed 5. At higher values, the degree of violation of lymphatic drainage function is determined.