Relevance. Giant cell tumor of the bone is most common in people of working age, which determines the high social significance of successful treatment of this category of patients. The main method of treatment is surgical. Currently, the targeted drug denosumab has appeared, the criteria for evaluating the effectiveness of therapy for which, according to the data of radiation methods, are not clearly defined.Target. To analyze and compare the possibilities of CT and MRI in evaluating the effectiveness of denosumab therapy for giant cell tumors.Materials and methods. The data of CT and MRI of 19 patients with giant cell tumor of tubular bones on the background of denosumab therapy were analyzed.Results. Before treatment, the extraosseous component was determined in 57.9 % (n = 11), after – 31.6 % (n = 6). The decrease occurred in 100 %, the disappearance – in 45 % (n = 11) of cases. The thickness of the extraosseous component before treatment ranged from 4 to 43 mm (Me = 15 mm), after treatment it ranged from 0 to 30 mm (Me = 8 mm). The decrease occurred in the range from 4 to 14 mm (M ± SD = 7 ± 4 mm). In 100 % of cases, a sclerotic rim appeared, the thickness of which after treatment ranged from 1 to 5 mm (Me = 3 mm). In the structure of the tumor, fibrosis occurred in 95 % (n = 18), a decrease in the cystic component occurred in 82 % (n = 9) of cases. Perifocal changes decreased in 100 % of cases. In 100 %, the average tumor density increased. The mean tumor density before treatment ranged from 27 to 65 HU (M ± SD = 42 ± 11 HU), after treatment it ranged from 69 to 500 HU (Me = 150 HU). The increase in density occurred in the range from 41 to 454 HU (Me = 101 HU). All differences are statistically significant (p < 0.05).Conclusions. Evaluation of effectiveness with the definition of quantitative and qualitative indicators is possible according to the data of both CT and MRI; with CT, changes are recorded longer, and more indicators available for quantitative measurement are determined.

Purpose: To demonstrate a clinical case of metastatic lesions of the bones, which clearly reflects the difference in the sensitivity of diagnostic methods SPECT/CT and MRI.Material and methods: A 69-year-old female patient with poorly differentiated gastric adenocarcinoma, which underwent WBS, SPECT/CT and MRI.Results: MRI revealed several metastases that were not reflected on SPECT/CT examination. Conclusion: Despite the high sensitivity and specificity of SPECT/CT, in some cases additional diagnostic methods are required. MRI allows to clarify and, possibly, detect previously undetected metastases.

Purpose: Demonstrate a clinical case of poorly differentiated chordoma, confirmed using a wide range of research methods.Material and methods: A 63-year-old female patient with poorly differentiated chordoma who underwent immunohistochemical examination, MRI, CT and scintigraphy.Results: An immunohistochemical study confirmed the morphological affiliation of the tumor, supplemented by the data of imaging methods.Conclusion: The poorly differentiated type of chordoma has a specific immunohistochemical picture, however, differential diagnosis based on imaging methods is currently a difficult task.

Relevance: Radionuclide bone scan signs of lesions are not specific and require radiological identification. Hybrid tomographic technology is a combination of spatial distribution of radiopharmaceuticals and its anatomical binding. Thus, makes it possible to accurately identify the affected bone structure and also determine the nature of this changes (radiological anatomy). In cancer patients, SPECT/CT method allows to visualize tumor pathology in the bones, but also keeps to a minimum errors and other excessive examinations.Purpose: To demonstrate the most frequent diseases and conditions that simulate tumor lesions in bones on bone scan.Material and methods: We analyzed the results of examinations of 81 patients with various tumor diseases (2015–2020). Bone scan was performed in the whole body 3 hours later, after intravenous administration of 99mTc-phosphotech on a Symbia E, T2 (Siemens, Germany). SPECT/CT was performed after WB Bone Scan.Results: The most frequent reasons for the focal increased uptake of radiopharmaceutical were: reactive increase in metabolism and as a result additional mineral repair: deforming osteoarthritis, osteophytes; post‑traumatic and postoperative changes; fractures (osteoporosis and stress fractures); inflammatory processes; focal uptake due to the benign neoplasms of bones and dysplasia. Combination of highly sensitive but non-specific scintigraphy with highly specific computed tomography makes it especially useful in anatomically difficult areas.Conclusion: SPECT/CT reveals a direct pater of anatomical and structural abnormalities with changes in bone tissue metabolism in case of different injuries and minimizes a number of ambiguous conclusions. SPECT/CT in oncological practice greatly helps nuclear medicine physician in the differential diagnostic process and reduces time of examination for the patient.