Leucocyte radiolabelling techniques: practical aspects.

Radiolabelled leucocytes migrate rapidly to sites of acute inflammation. The simplest technique for imaging intestinal inflammation involves radiolabelling patients' mixed while cells ex vivo with either 99mTc or 111In which are then reinjected. However, further purification of mixed white cells to granulocytes is needed for optimal results using 111In. Owing to the simpler labelling procedure, availability, image quality and dosimetry, 99mTc-HMPAO has gained favour for the investigation of acute inflammation including inflammatory bowel disease. Because of its longer half life. 111In is more suited to the imaging of chronic inflammation such as osteomyelitis. Attempts to radiolabel granulocytes in vivo using monoclonal anti-granulocyte antibodies have been largely unsuccessful to date, and this approach remains a challenge for the future.