Quantification of disease activity in patients undergoing leucocyte scintigraphy for suspected inflammatory bowel disease.

PURPOSE: Whole-body gamma camera counting is an alternative to faecal 111In collection for quantifying disease activity in inflammatory bowel disease (IBD) but requires administration of imaging activities of 111In. The aim of this study was to explore a dedicated whole-body counter which requires 20-fold less activity than gamma camera counting. METHODS: Thirty patients with known or suspected IBD received 99mTc-granulocytes (approximately 200 MBq) and 111In-granulocytes (approximately 0.5 MBq). The 99mTc-cells were injected 45 min after the 111In-cells and immediately after a baseline 111In whole-body count. The decay-corrected count at 120 h was expressed as a fraction of baseline to give whole-body 111In retention (WBR). One patient was excluded as the injected cells were non-viable. RESULTS: Median 45-min intravascular 111In recovery was 35% in patients compared with 43% in six normal volunteers (p<0.05). WBR in normals ranged from 91% to 93% and in 11 patients with negative 99mTc imaging from 87% to 96%. Only one of 11 patients with negative imaging had WBR <90% while 11/12 patients with WBR <90% had abnormal imaging. Ten of 13 patients with Crohn's disease (CD) had abnormal imaging. The lowest WBR in these ten was 77% and six had values of >90%. There was a significant association between WBR and 99mTc image grade (Rs=0.73, p<0.002) in 16 patients without CD, but not in 13 patients with CD (Rs=0.54, p>0.05). CONCLUSION: Dedicated whole-body counting is able to quantify disease activity in IBD but may give normal values in active CD.

Measurement of the extraction fractions of nanocolloid and polyclonal immunoglobulin by axillary lymph nodes in patients with breast cancer.

BACKGROUND: 99mTc nanocolloid (99mTc-NC) is the most widely used tracer for lymphoscintigraphy, although others have been proposed, including radiolabelled proteins such as human serum albumin and polyclonal human immunoglobulin G (HIG). The extraction fraction of such tracers by individual nodes is clearly important but has not previously been measured in humans. METHODS: Patients scheduled for axillary clearance surgery (three groups) received dual-labelled radiotracers 2-4 h before surgery: group 1 (3 patients) received 99mTc-NC (10 MBq) and 111In-HIG (2 MBq) as a mixture (0.2 ml) into the breast parenchyma above the primary tumour; group 2 (3 patients) received 99mTc-HIG (10 MBq) and 111In-HIG (2 MBq) as a mixture (0.2 ml) into the breast parenchyma above the primary tumour; and group 3 (4 patients) received 99mTc-HIG (10 MBq) and 111In-HIG (2 MBq) separately (both 0.2 ml) into the breast parenchyma above the tumour and the intradermal plane at the areola. All resected nodes were counted for Tc and In in a well-type scintillation counter. In group 1, nodes were ranked according to their Tc uptake. In groups 2 and 3, nodes were ranked separately according to their respective Tc and In uptakes. If nodes are arranged in linear order and each node extracts a constant fraction of incoming tracer, then the activity in the nodes would decrease exponentially with an individual nodal extraction fraction, E, equal to 1-e(-k), where k is the rate constant of decrease. RESULTS: In the first group, 99mTc-NC and 111In-HIG identified the same sentinel and second echelon nodes. The observed decrease in nodal activity was exponential in all groups, at least for the first five nodes. Average values for E, based on the first five nodes were 0.69 (range 0.57-0.89; n=3) for 99mTc-NC and 0.45 (0.15-0.70; n=17) for HIG (irrespective of label) (Wilcoxon rank sum, P=0.02). With respect to HIG, there was no significant difference in E between 99mTc and 111In or between deep and superficial injections in group 3. CONCLUSION: Although HIG has an extraction fraction less than 99mTc-NC, the value of E is still high enough to make HIG a useful tracer for lymphoscintigraphy, especially for identifying second echelon nodes in addition to sentinel nodes and for imaging lymphatic vessels as well as lymph nodes.