Biodistribution and radiation dosimetry of stabilized 99mTc-exametazine-labeled leukocytes in normal subjects.
Labeling leukocytes with 99mTc-exametazime is a validated technique for imaging infection and inflammation. A new radiolabeling technique has recently been described that enables leukocyte labeling with a more stable form of 99mTc-exametazime. A normal value study of stabilized 99mTc-exametazime-labeled leukocytes has been performed, including biodistribution and dosimetry estimates in normal subjects.


METHODS
Ten volunteers were injected with stabilized 99mTc-exametazime-labeled autologous leukocytes to study labeled leukocyte kinetics and dosimetry in normal subjects. Serial whole-body imaging and blood sampling were performed up to 24 h after injection. Cell-labeling efficiency and in vivo viability, organ dosimetry, and clearance calculations were obtained from the blood samples and imaging data as well as urine and stool collection up to 36 h after injection.


RESULTS
Cell-labeling efficiency of 87.5% +/- 5.1% was achieved, which is similar to or better than that reported with the standard preparation of 99mTc-exametazime. In vivo stability of the radiolabeled leukocytes was also similar to in vitro results with stabilized 99mTc-exametazime and better than previously reported in vivo stability for nonstabilized 99mTc-exametazime-labeled leukocytes. Organ dosimetry and radiation absorbed doses were similar with a whole-body absorbed dose of 1.3 x 10(-3) mGy/ MBq. Urinary and fecal excretion of activity was minimal, and visual assessment of the images showed little renal parenchymal activity and no bowel activity up to 2 h after injection.


CONCLUSIONS
Cell labeling and in vivo stability appear improved compared with the leukocytes labeled with the nonstabilized preparation of 99mTc-exametazime. There are advantages in more cost-effective preparation of the stabilized 99mTc-exametazime and an extended window for clinical usage, with good visualization of abdominal structures on early images. No significant increase in specific organ and whole-body dosimetry estimates was noted compared with previous estimates using nonstabilized 99mTc-exametazime-labeled leukocytes.
Robins
P D
PD
Nuclear Medicine Department of Diagnostic Radiology, Mayo Clinic, Rochester, Minnesota 55905, USA.
Salazar
I
I
Forstrom
L A
LA
Mullan
B P
BP
Hung
J C
JC
D000328:Adult; D005260:Female; D006801:Humans; D007962:Leukocytes; D008297:Male; D011829:Radiation Dosage; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D012016:Reference Values; D019690:Technetium Tc 99m Exametazime / Q000493:pharmacokinetics; D014018:Tissue Distribution
D019275:Radiopharmaceuticals; D019690:Technetium Tc 99m Exametazime