Blood sample precautions
do not use needle smaller than 21 gauge
small diameter needles may damage cells
label all supplies with patient name and ID number
wear latex gloves/lab coats are all times
consider all blood to be infectious
Tc-99m HMPAO
questionable diagnostic accurarcy due to nonspecific bowel accumulation
abdomen imaging normally performed at 30min and 3h
bowel excretion seen at 4h
infection/inflammation detection within 4h and as early as 30 min after injection
Tc-99m Ceretec General Properties
plasma half life = 4h
diffuses into leukocyte and is converted to nondiffusible hydrophilic complex
highly lipophilic
140 keV photopeak
Normal adult dose of 10-20 mCi
6 hour half life
In-111 oxine
In-111 Oxine General Properties
plasma half life = 7h
Penetrates neutrophil membranes where transchelation of In-111 to transferrin occurs
normal dose = 0.5 mCi
Lipid soluble
Photopeaks at 171 and 245 keV
67 Hour half life
Imaging Protocol
highest diagnostic specificity at 24 h
4-6 h for preliminary images
prominent abscess to bacckground ratio
optimal imaging 24h post injection
Tc-99m HMPAO vs. In-111 Oxine
Tc-99m HMPAO Advantages
often used for inflammatory processes in extreminities
rapid diagnosis
selective granulocyte labeling
reduced radiation burden
high count rate - enhanced image resolution
technetium availability
In-111 oxine advantages
used frequently for abdominal imaging
high target to background ratio
7h half life in blood compared to 4h BHL with Tc-99m HMPAO
greater stability within granulocytes and inflammatory site
preferred for chronic processes(fever of unknown origin, infected prosthesis)
WBC imaging
Anticoagulants
heparin
1000-2000U Most commonly used
Low cost
some affinity for technetium
ACD - Anticoagulant citrate dextrose or Acid citrate dextrose
less adhesion to centrifuge tubes/syringes used in labeling procedures
no affinity for technetium
shown to be cytotoxic to cells (insignificant)
High cost when compared to heparin
Hespan (HES)
rarely allergic reactions reported
cleared from body after administration
sometimes* added to blood sample to increase erythrocyte edimentation rate and greater leukocyte recovery
synthetic polysaccharide colloid used as volume expander
clinical considerations
Nuclear medicine allows for whole body imaging
important when no localizing signs are present
CT and ultrasound are often used initially but cannot differentiate between infection and noninfectious process
delayed diagnosis is associated with increased mortality
early diagnosis can cure most infections
sites of occult infection are difficult to diagnose
WBC separatory technique
Gravity sedimentation
"buffy coat"
contains high leukocyte concentration
accumulation of cells of top of erythrocyte layer
at 1 hour, 70% of WBC's suspended in supernatant
minimize blood agitation
most popular separation method
Labeling Procedure
9. Inject 500 uCi In-111 oxine
8. Remove supernatant and suspend in 5 mL PPP
7. Add 10mL PPP, centrifuge @450g for 5 min
6. Suspend in 2 mL 0.9% saline and add 0.5 mCi In-111 Oxine
5. Resuspend WBC button with 2mL 0.9% saline, add 9.1 mL sterile water, swirl for 20 seconds, add 2 mL 5% saline, followed by 10mL 0.9% saline, centrifuge @ 450g and discard liquid
Lyse RBC
4. Remove PPP and centrifuge @ 1000g for 5 min
3. transfer plasma, centrifuge @450g for 5min
2. Sediment 50-60 minutes
1. Take 43mL(at least) blood with 7 mL ACD or 400U heparin plus 6mL 6% hetastarch
Leukocytes Ave Adult ~7000 WBC/microliter
Granulocytes (65%)
basophils
eosinophils
neutrophils
Lymphocytes (30%)
Monocytes (5%)
Inflammtion
it is mainly the neutrophils and monocytes that are involved in the inflammatory response
chronic
Acute
Agents: In-111 Oxine Tc-99m Ceretec (HMPAO)
