Pulmonary emboli imaging with (99m)Tc-labelled anti-D-dimer (DI-80B3) Fab' followed by SPECT

Pre-clinical experiments demonstrated that intravenous (99m)Tc labelled DI-DD-3B6/22-80B3 humanised anti-fibrin-D-dimer Fab' fragments ((99m)Tc-DI-80B3) allowed scintigraphic imaging of acute pulmonary emboli (PE). The aims of this clinical study were to determine the safety of (99m)Tc-DI-80B3 in patients with PE and evaluate the resulting scintigraphic images for the localisation of acute PE.

(99m)Tc-DI-80B3 (0.5mg, 710-850MBq) was administered intravenously to subjects (n=14) with segmental or larger PE on recent contrast-enhanced helical CT scans. Thoracic SPECT scans were acquired 15 minutes, 2 hours and 4 hours afterwards. Subjects were followed for 90 days subsequently.

There were no serious adverse events or antibody responses associated with (99m)Tc-DI-80B3 administration. Focal accumulations of (99m)Tc-DI-80B3 on the SPECT images of the thorax acquired at four hours corresponded to pulmonary emboli detected by CT. Two independent "blinded" SPECT readers identified 79% and 71% (respectively) of the right lung and 79% and 64% (respectively) of the left lung in which CT scans disclosed PE.

(99m)Tc-DI-80B3 is well-tolerated in patients with acute PE and does not induce an immune response. (99m)Tc-DI-80B3 may offer a novel approach to imaging PE in a clinically acceptable timeframe without exposure to potentially nephrotoxic radiographic contrast agents.