Biodistribution and dosimetry of technetium-99m-hydrazino nicotinamide IgG: comparison with indium-111-DTPA-IgG.
The biological behavior of human polyclonal immunoglobulin G (IgG), radiolabeled with 99mTc via a nicotinyl hydrazine derivative (99mTc-HYNIC-IgG), was evaluated in normal human subjects.


METHODS
Initial biodistribution and dosimetry studies were performed in six normal male volunteers. Additionally, 99mTc-IgG and 111In-DTPA-IgG were co-injected into six subjects and scintillation camera images were acquired at 6 and 18 hr later and serial blood and urine samples were collected. Biodistribution of both radiopharmaceuticals were measured by region of interest analysis. In the dual-injection group, images were crossover-corrected.


RESULTS
All subjects tolerated injection of the radiolabeled IgG preparations without apparent ill effects. Biodistribution of the two antibody preparations were remarkably similar with an increase in liver and abdominal activity for the 111In preparation. Linear correlation of the tissue-to-blood ratios of 99mTc and 111In-labeled IgG was observed at both times (r2 > 0.98). The slopes of the regression line were 0.97 and 0.76 at 6 and 18 hr, respectively. The beta phase of the blood clearance of 99mTc-HYNIC-IgG was significantly delayed (p < 0.01) compared with 111In-IgG (t1/2: 51.9 +/- 6.5 versus 35.3 +/- 3.4 hr). In contrast, the volumes of redistribution and urinary excretions of the radiopharmaceuticals were not significantly different.


CONCLUSIONS
These studies establish that the biodistribution of 99mTc-HYNIC-IgG in normal human subjects is nearly identical to 111In-DTPA-IgG.
Callahan
R J
RJ
Division of Nuclear Medicine, Department of Radiology, Massachusetts General Hospital, Boston, Massachusetts 02114, USA.
Barrow
S A
SA
Abrams
M J
MJ
Rubin
R H
RH
Fischman
A J
AJ
D000328:Adult; D006801:Humans; D007074:Immunoglobulin G / Q000378:metabolism; D007205:Indium Radioisotopes / Q000493:pharmacokinetics; D008297:Male; D008875:Middle Aged; D015609:Organotechnetium Compounds / Q000493:pharmacokinetics; D004369:Pentetic Acid / Q000493:pharmacokinetics; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D013997:Time Factors; D014018:Tissue Distribution
D007074:Immunoglobulin G; D007205:Indium Radioisotopes; D015609:Organotechnetium Compounds; D004369:Pentetic Acid