We studied the possibility of in vivo tracing of multipotent mesenchymal stromal cells labeled with a radiophermaceutic preparation based on metastable isotope Technetium-99m and injected to rats with modeled traumatic brain injury. Accumulation of labeled cells occurred primarily in the liver and lungs. The cells distribution in internal organs greatly varied depending on the administration route. Cell injection into the carotid artery led to their significant accumulation in the damaged brain hemisphere, while intravenous injection was followed by diffuse cell distribution in all brain structures. Scintigraphy data were confirmed by magnetic resonance imaging and histological staining of cells. Visualization of stem cells labeled with Technetium-99m-based preparation by scintigraphy is an objective and highly informative method allowing real-time in vivo cell tracing in the body.
Practically any organ in the body can be studied by means of radionuclide diagnostics. Some organs can be studied by several methods. Most well-known studies are done using the gamma camera installed in the hospital. When a problem is clearly stated and continual feedback is maintained between the radiologist and the doctors in the clinical departments, the possibilities of radionuclide diagnostics become limitless and the assistance in making difficult diagnoses is invaluable.Compounds labeled with radionuclides were first used in clinical practice at the end of 1920. A good illustration of the use of radioactive substances in medicine is analysis of the iodine distribution in different diseases of the thyroid gland. It is known that the thyroid gland picks up all iodine entering the body, irrespective of the entry path. The patient was asked to ingest a solution of 131 I with known activity, which was taken to be 100%. The accumulation of the preparation in the thyroid gland was determined empirically by measuring the counting rate near the thyroid gland 2, 4, and 24 h after the radioactive iodine was ingested. An accumulation rate above the normal rate indicates hyperactivity of the thyroid gland and an accumulation rate lower than normal indicates hypoactivity [1].This example of the use of a radioactive tracer for clinical purposes clearly demonstrates the essence and possibilities of radionuclide diagnostics. Even though improved radiopharmaceuticals, radioactive tracers, and detectors exist, the principle of detection and estimation of tracer accumulation in live tissue remains the same.The production of adequate quantities of various radionuclides became possible in the mid-1950s with the development of the atomic industry. This expanded the selection of organotropic radiopharmaceuticals. Radiometric instruments were also improved at this same time. It became possible, for example, to introduce a radioactive label into hippuric acid, which was traditionally used to determine the functional state of the ductule system of the kidneys. Introducing labeled hippuran and performing external radiometry on each kidney separately, a recording instrument was attached to the sensor in a two-channel radiometer and recorded the change in the radioactivity over time. The changes in the shape and height of the curve characterized a specific pathology. This procedure is a classic case of a dynamic (functional) analysis.The next stage in the development of radionuclide visualization was the development of a scanner. It was proposed that the radioactivity be measured by moving the sensor in a radiometer over the organ being studied, stopping for a prescribed counting time at equally spaced positions and obtaining in this way a linear slice. Next, the sensor was shifted by one unit in a direction perpendicular to the preceding motion and moved parallel to the first straight line. Such a collection of linear slices (or scans) has become known as a scanogram and the method itself as scanning.The development of new instruments...
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