No abstract

Scintigraphic imaging of infection and inflammation is a powerful diagnostic tool in the management of patients with infectious or inflammatory diseases. Most infectious and inflammatory foci can be visualized accurately with radiolabeled autologous leukocytes. However, preparation of this radiopharmaceutical is laborious and requires the handling of potentially contaminated blood. Nowadays, a few radiopharmaceuticals are available that could replace radiolabeled leukocytes, such as: 67Ga-citrate, 99mTc-IgG and 99mTc-labeled antigranulocyte antibody preparations. Furthermore, various agents labeled with 99mTc are currently developed for this application: chemotactic peptides, cytokines and liposomes. Here, the characteristics and the diagnostic potential of established and experimental radiopharmaceuticals for infection and inflammation imaging are reviewed.

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In the present study, the potential role of 99mTc-PEG-liposome to determine the extent and severity of active disease of Crohn's colitis was investigated. Patients suspected of having an exacerbation of Crohn's disease underwent a 99mTc-PEG-liposome scan (740 MBq, imaging at 4 and 24 h p.i.). A barium enema or endoscopy was performed as the standard verification procedure. Disease activity indices (Clinical Disease Activity Index and Van Hees Activity Index) were calculated. In seven patients positive images of colon segments affected by Crohn's colitis were obtained using 99mTc-PEG-liposomes. Only a moderate relation between 99mTc-liposome scan grading and verification procedures was found (Spearman rank r = 0.22). In accordance with previous studies, no significant correlation was found between the clinical disease activity indices and the verification procedures. This study was prematurely terminated because of unacceptable side-effects in 3 out of 9 patients, which occured almost immediately after starting the infusion. The complaints consisted of dyspnea and facial erythema. The symptoms were self-limiting when the infusion was stopped. In conclusion, the extent of Crohn's colitis can be established non-invasively with 99mTc-PEG-liposome scintigraphy. However, in view of the encountered side-effects, the PEG-liposomal preparation may have to be modified.

99mTc-PEG liposomes and 99mTc-HYNIC IgG performed at least as well as the standard agent, 67Ga citrate, in the detection of experimental intraabdominal abscesses, with obvious advantages such as lower radiation exposure and more favorable physical properties. Of the two technetium agents, the liposomes seemed to be superior, providing the earliest diagnostic image and the best correlation with the inflammatory abnormalities. In addition, the preferential localization of radiolabeled PEG liposomes holds promise for targeted delivery of liposome-encapsulated drugs.