Domain III(F): radiolabel blood components with radiopharmaceutical according to protocol

required lab equipment & supplies

- syringes, needles, sterile gloves

- lead shields/syringe shields

- heparin or ACD tubes (for anticoagulation)

- centrifuge

- laminar flow hood (aseptic handling)

- dose calibrator

- gamma well counter (assess labeling efficiency)

- radiopharmaceutical-specific kits

anticoagulants & other additives

- heparin or ACD (acid citrate dextrose: prevents clotting

- stannous chloride (SnCl2): used to reduce Tc-99m so it can bind to blood components

- HES (hydroxylethyl starch): helps separate WBCs by sedimentation in some WBC labeling protocols

chemical reactions

- reduction of Tc-99m by stannous ions to allow binding to cellular components

- in vitro labeling: tin reduction followed by addition of Tc-99m pertechnetate

- WBC labeling: WBCs are isolated, washed, & incubated with radionuclide

cell washing

- essential for WBC labeling

- removes plasma & unwanted cells

- ensures labeling specificity

- usually done with isotonic saline after centrifugation

in vivo labeling

- labeling occurs inside the body

- inject stannous chloride IV (acts as a reducing agent to prepare RBCs for labeling)

- wait ~15-30 minutes

- inject Tc-99m pertechnetate (Tc-99m binds to circulating RBCs in bloodstream)

- pros: quick, easy, minimal handling

- cons: lower labeling efficiency (60-80%)

modified in vivo

- hybrid of in vivo & in vitro

- inject stannous chloride IV

- wait ~20 minutes, & then draw sample of patient's blood

- add Tc-99m to syringe with blood sample

- allow labeling to occur (~10 mins), then inject labeled RBCs

- pros: higher labeling efficiency (80-90%) than in vivo

- cons: requires handling of blood outside body (more regulation)

in vitro (UltraTag®)

- labeling is always done completely outside the body

- withdraw patient blood

- mix with kit reagents & Tc-99m in vitro

- after incubation (~20 mins), reinject labeled RBCs

- highest labeling efficiency (95-98%)

- cons: most complex method, requires sterile technique & strict radiation safety compliance

reinjection patient & sample verification

- double-verify patient ID before reinjection

- ensure labeled blood is re-injected only into same patient from whom it was drawn

- follow universal precautions & maintain proper documentation