Quantitative assessment of overall inflammatory bowel disease activity using labelled leucocytes: a direct comparison between indium-111 and technetium-99m HMPAO methods.

The ideal imaging method in inflammatory bowel disease would reliably detect inflammation, identify the correct intestinal location, and assess the severity of the disease. The aim of this study was to compare scintigraphic methods of quantifying overall disease activity using both indium-111 (111In) and technetium-99M (99mTc) HMPAO labelled leucocyte scans. The four day faecal excretion of 111In was measured after 111In scintigraphy in 24 patients known to have inflammatory bowel disease. The same patients also underwent 99mTc HMPAO scanning. The scans were performed 10 days or less apart with no changes in treatment between scans. Bowel activity on the 99mTc HMPAO scans was assessed using a computer based method (scan score) and a visual grading method in a further 54 99mTc HMPAO. The results showed a close correlation between inflammatory activity defined by faecal 111In excretion and the scan score generated from the computer analysis of the 99mTc HMPAO image (Spearman rank correlation: rs = 0.78; p < 0.001). Accurate information to localise inflammatory activity could be obtained by simple visual assessment of both types of scan images, although image quality was superior with 99mTc HMPAO. Qualification of disease activity from 99mTc HMPAO images by visual grading was associated with a large variability, only 69% of scans had similar scores when graded by three observers. Computer generated image analysis was more reproducible. In conclusion, in inflammatory bowel disease 99mTc HMPAO scintigraphy and faecal 111In excretion correlated well. Either method can quantify and localise the inflammation. As 99mTc HMPAO scanning provides a quicker result, with a lower radiation dose, and avoids faecal collection, it may be the preferred method.