Evaluation of inadequate positions of Tc99m MDP bone scintigraphy in adults

The diagnostic accuracy and image quality of bone scan depends on adequate patient's positioning. Inadequate positioning causes difficulty in interpretation since it leads to hiding or simulating abnormalities. Objective: The aim of this study is to evaluate the effect of inadequate positioning on the image quality of bone scans of adults. Methods: retrospective analysis of positioning of bone scans of 46 adults patients (24 males, 22 females), was obtained using delayed images of the scans. Whole body and spot views were obtained three hours after intravenous injection of 925 MBq (25 mCi) of Tc99m MDP. The image was performed with a dual head gamma camera. Images were acquired anterior and posterior views simultaneously using 256X256 matrix for the spot views and 256 X 1024 matrixes with a speed of 8 min/meter. 500 kcounts were collected for each spot view. Results: Thirty seven cases (17 males, 20 females) showed one or more positional error, seen on a total of 78 images. Inadequate skull positioning had been showed in 13 cases (6 male, 7 females), which is mostly due to tilting. Inadequate chest positioning was found in 15 cases (4 males, 6 females), mostly due to tilted shoulder and asymmetry with non-centralized sternum. Tilted pelvis was seen in 15 cases (6 male, 9 females). 13 cases (7 males, 6 females) were found to have improper positions of the upper extremities, mostly due to raised arms (not extended beside the patient). Inadequate lower extremities positioning had been showed in 27 cases (15 males, 12 females). In most of the cases, the feet were not internally rotated. Conclusion: In-adequate positioning of adult patients for bone scintigraphy is common in the skull, shoulder, pelvis and extremities. Principles of proper positioning of patients for bone scanning should be followed with whole body and spot acquisition to preserve and enhance the diagnostic value of this valuable procedure.; care should be taken during positioning of adults patients to avoid false results. (authors)