Tc-99m Labeled WBCs

• Used for localizing infection and abscesses

• Principle of labeling

  • Tc-99m Ceretec is lipophilic and crosses lipid bilayer of cell membranes

  • Inside the cell the Ceretec complex is broken down and the resulting charged Tc-99m species is trapped in the cell

  • All cell types are labeled by Ceretec so prior leukocyte separation is necessary

Tc-99m WBC Labeling Procedure

1. Check patient’s white count (must be > 2K)

2. Obtain ~50 mL anticoagulated whole blood from pt (larger volume if WBC count is low)

3. Optional: add Hetastarch as a sedimentation aid

4. Centrifuge at 15 x g for 10 min

5. Aseptically remove the platelet-rich & leukocyte-rich supernatant

6. Centrifuge at 200 x g for 10 min.

7. Decant platelet-rich plasma and then wash cells with 0.9% NaCl

8. Add ~40 mCi freshly prepared Tc-99m Ceretec dropwise to leukocyte pellet and incubate for 20 min. Do NOT use Methylene Blue.

9. Centrifuge, remove unbound Tc-99m, and wash pellet. 

10. Resuspend labeled WBC in either platelet poor plasma or 0.9% NaCl

11. Labeling 50 - 80 %.

12. Draw up dose and inject patient. If patient has been on dialysis, wait until procedure is complete

Quality Control of Tc-99m WBC

• Place a drop of labeled cells on a hemocytometer

• Add a drop of Trypan Blue dye

• Add a cover slip and examine under microscope

• Viable cells exclude dye; dead cells are stained blue

• If  >10% are dead or large clumps are present, don’t use