Imaging inflammation with 99Tcm HMPAO labelled leucocytes.

Labelling leucocytes with 99Tcm using hexamethylpropyleneamine oxime (HMPAO) utilizes the advantages of technetium over indium in imaging inflammation. A retrospective study has been performed on 43 consecutive patients imaged with 99Tcm HMPAO labelled leucocytes in order to assess the reliability of the technique. Particular attention was paid to the different handling characteristics of the 99Tcm HMPAO labelled cells compared with those labelled with indium. It was found that 99Tcm HMPAO labelled leucocytes gave an overall accuracy of 93.2%, a sensitivity of 92.8%, a specificity of 93.3% and a positive predictive value of 86%. 99Tcm HMPAO labelled leucocyte scanning provides a reliable method of imaging inflammation, though errors in interpretation may occur due to the hepato-biliary excretion of activity that occurs with this technique.