[Extraosseous abnormalities and artifacts in skeletal scintigraphy].

Objective: to specify frequency, patterns and diagnostic significance of extraosseous soft tissue findings in 99mTc-pyrophosphate skeletal scintigraphy.
Material and Methods: Results of skeletal scintigraphy from 1060 patients (447 men, 613 women) were analyzed. Scanning in "whole body" mode started in 3-4 hours after 740 MBq of radiotracer activity intravenous administration, and performed in anterior and posterior projections in continuous table motion mode at rate of 6-8 cm per minute. Single photon emission computed tomography/computed tomography (SPECT/CT) was additionally performed when necessary.
Results: Extraosseous scintigraphic findings were discovered in 161 (15.2%) patients, they can be divided into three categories: nephrourological (7.7%), soft tissue (5.4%) and artifacts (2.1%). First category included anatomical and functional changes in the urinary system (kidney location anomalies and nonobstructive uropathies). SPECT/CT was performed to differentiate calycostasis in the projection of the upper group of calyces and focal changes of the ribs. Soft tissue extrarenal findings included diffuse or focal RP hyperfixation within breasts (29 patients), thyroid glands (15), myocardium (5), scrotum (4) and abdominal cavity (4). Symmetrical increased RP accumulation in breast or thyroid lobes was accepted as normal. Pathologic soft tissue findings in 11 patients were verified by history or instrumental data: breast cancer (2), testicular cancer (1), nodular goiter (2), uterine fibroids (2), primary cancer with liver metastases (1), association of "hot kidney" phenomenon with chemotherapy (2), and "superscan" phenomenon with myelofibrosis (1). Causes of radiotracer artifacts in the liver and spleen (14) were of radiopharmaceutical factors, in axillary lymph node (7)--partially infiltrative radiopharmaceuticals administration, in the colon (1)--previous myocardial perfusion scintigraphy.
Conclusion: Analysis and interpretation of abnormal extraosseous findings in skeletal scintigraphy is an essential component of additional diagnostic information, that can influence subsequent diagnostic and therapeutic tactics.