Purpose: 99mTc-HMPAO radiolabeled autologous leukocyte scintigraphy is routinely used
clinically for infection imaging. Leukocytes are mostly separated via sedimentation. It is unknown
whether leukocytes are clearly separated by sedimentation or selectively labeled. Therefore, in this
study, the blood cell numbers were investigated after leukocyte radiolabeling to identify the cells
strongly radiolabeled by 99mTc-HMPAO.
Methods: This study was performed with leftover blood samples of the patients who underwent
99mTc-HMPAO scintigraphy at Chonbuk National University Hospital (2018-2019). The blood of 22
patients was drawn for 99mTc-HMPAO scintigraphy. WBCs were separated via conventional sedimentation
at our clinic and radiolabeled. The concentration of cell components was determined using an
automatic hematology analyzer. The cells in the final sample injectate sample were separated using
Histopaque and counted with a dose calibrator.
Results: The average numbers of RBCs, WBCs, and PLTs in the final injection sample were 79 ± 33,
23.26 ± 11.95, and 229.5 ± 206.57 x 103/μL, respectively. The PLT number was almost 10-fold the
number of WBCs. The number of RBCs was nearly 3-fold higher than WBCs [RBC/WBC ratio = 4.67
± 3.58, and PLT/WBC ratio = 10.65 ± 12.46]. Following Histopaque separation, the activity of each
layer showed 99mTc-HMPAO labeling of WBC > RBC > PLT in order. The total activity/cell numbers
of WBCs, RBCs and PLTs were 0.016 ± 0.010, 0.005 ± 0.005 and 0.003 ± 0.002, respectively
(p > 0.05).
Conclusion: Although the numbers of RBCs and PLTs were highly increased after sedimentation, their
individual cellular activity was lower than that of WBCs. 99mTc-HMPAO was more selective to WBCs
than RBCs or PLTs. In conclusion, a higher number of WBCs were radiolabeled compared with RBCs