111In-DTPA
octreotide (DTPAOC) has been used for detecting
somatostatin receptor positive
tumor for years. In-111 DOTA-Tyr3-octreotide (
DOTATOC) is newly developed for diagnostic and therapeutic purposes. In this study, we compared the biodistribution and
tumor uptake ratio after injection of
In-111 DTPAOC and In-111
DOTATOC in rats. Twelve rats bearing pancreatic
tumors were divided into two groups: six rats were sacrificed at 4 hr after injection of 3.7 MBq of
In-111 DTPAOC and another 6 rats were sacrificed at the same time after injection of 3.7 MBq of In-111
DOTATOC. Samples of various organs were obtained and counted to calculate the tissue concentration. In addition, 12 rats bearing pancreatic
tumors were scanned at 4, 24, and 48 hr after injection of 37 MBq of
In-111 DTPAOC or In-111
DOTATOC. The
tumor uptake ratios (T/N ratio) were calculated. The biodistribution data showed that the activity in the
tumor as well as in the kidney was significantly higher in the In-111
DOTATOC group than in the
In-111 DTPAOC group, although both
radiopharmaceuticals had the expected high affinity to the
tumor. The T/N ratios in the In-111
DOTATOC group were also significantly higher than those in the
In-111 DTPAOC group at 24 hr after injection. We conclude that In-111
DOTATOC showed lower clearance than
In-111 DTPAOC in the rats bearing pancreatic
tumors, although both of these
radiopharmaceuticals showed expected high
tumor uptake.