Abstract |
Inflammation scan using radiolabelled leukocytes has
high sensitivity and specificity. Several methods for
labelling leukocytes have been evaluated using P-32
diisopropyl fluorophosphate (DFP -32), H-3 thymidine,
Cr-5I chromate, Ga-67 citrate and Tc-99m-sulfur
colloid. In-lll-oxine has proved so far to be the most
reliabte agent for labelling leukocytes. In-111-oxine
is, however, expensive, not easily available when
needed, and its radiation dose to leukocytes is
relatively high. Moreover, resolution of the resultant
image is relatively poor. Tc-99m is still the agent of
choice because of, as compared with the indium, its
favorable physical characteris- tics, lower cost and
availability. Now the technique for labelling the
leukocytes with technetium is successfully obtained
using the lipophilic HAPAO with higher efficiency for
granulocytes than for other cells. With this technique
it is possible to label leukocytes in plasrna to
improve the viability of the leukocytes. Inflammation
scan using Tc-99m-HMPAO has been evaluated in several
laboratories, and difference in methods for separation
and labelling accounts for difference in efficiency,
viability and biodistribution of the labelled
leukocytes. We performed inflammation scan using
leukocytes labelled with Tc-99m-HMPAO in three dogs 24
hours after inoculation of live E. Coli and S. Aureus
in their right abdominal wall. We separated mixed
leukocytes by simple sedimentation using 6% hetastarch
(HES) and labelled the leukocytes with Tc-99m-HMPAO in
20% cell free plama diluted with phosphate buffer
solution(Fig. 1). Uptake was high in the liver and
spleen but is was rninimal in the lungs on whole body
scan. Kidneys and intestine showed minimal activity
although it was high in the urinary bladder(Fig. 2).
Uptake of labelled leukocytes in the inflammation site
was definite on 2 hour-postinjection scan and abscess
was cleariy delineated on 24 hour-delayed scan with
high target-to-nontarget ratio(Fig. 3, 4). Inflammation
scan using mixed leukocytes labelled with Tc-99m-HMPAO
is very sensitive and specific in early detection of
inflammation |