The inflammatory activity in 108 bowel segments of 40 patients with suspected or known inflammatory bowel disease was assessed macroscopically by endoscopy, histology and technetium-99m hexamethyl propylene amine oxine (99mTc-HMPAO) leucocytes using a numerical grading system (scores 0-3). A 4-h series of scintigrams showed a significant correlation with both histological and macroscopical assessment of disease activity (rho = 0.850, P less than 0.001 and rho = 0.773, P less than 0.001, respectively). Sensitivity, specificity and accuracy of scintigraphy in detecting active inflammatory segments were 85%, 92% and 89%, respectively. A normal scintigram did not completely exclude mild inflammatory activity, especially in the rectosigmoid area. 99mTc-HMPAO leucocytes offer an accurate and non-invasive alternative for the assessment of disease activity in ulcerative colitis and Crohn's disease.

The efficiency of 99Tcm-methylene diphosphonate (MDP) and 99Tcm-dicarboxypropane diphosphonate (DPD) to detect pathologically increased bone uptake was evaluated both by computed quantitative intra-individual and visual inter-individual comparison. Twelve patients with altogether 44 metastases in ribs and lumbar vertebrae were evaluated quantitatively. The lesion to normal bone ratio (mean ± SD) was, with MDP, 2.9 ± 1.6 and with DPD 2.4 ± 1.2 (p<0.001), and the normal bone to soft tissue ratios with MDP 8.5 ± 5.0 and with DPD 9.4±6.1 (NS). Visual analysis of 162 patients with 334 focal lesions showed no significant difference between two MDP preparations and one DPD preparation. Visual and quantitative comparison in the three most common malignancies studied (breast, prostatic, and lung carcinoma) gave the same result. Because the lesion to normal bone ratios were high with both agents, and there was no significant difference on visual analysis, both radiopharmaceuticals are considered to be relevant bone seeking agents and the difference between MDP and DPD is only academic and not of practical value.

Forty-five patients with various inflammatory diseases were imaged with 99Tcm-HMPAO labelled leucocytes and 99Tcm-nanocolloid within 7 days. The overall sensitivity of 99Tcm-leucocytes was 97% and that of 99Tcm-nanocolloid 59% and both agents had a 100% specificity. The 99Tcm-leucocyte method showed reliable results in various inflammatory and infectious conditions, and seems suitable as a primary imaging method. On the contrary, 99Tcm-nanocolloid cannot be recommended for use in inflammatory bowel diseases, soft tissue abscesses or prosthetic vascular graft infections. However, 99Tcm-nanocolloid gave reliable information in inflammatory and infectious bone and joint diseases in which it had a 90% sensitivity and 100% specificity. In those lesions the 99Tcm-nanocolloid method may be useful, because it is simple, fast and cheap. Yet, further evaluation is needed.

Two hundred and fifty-seven patients were studied with bone-seeking radiopharmaceuticals. They were randomly divided into three groups. Two groups were injected with two different 99mTc-methylene diphosphonates from two manufacturers (MDP 1 and MDP 2) and the third group with 99mTc-dicarboxypropane diphosphonate (DPD). DPD was found to be superior with respect to blood clearance, femur to soft tissue ratio and subjectively assessed image quality. There seemed to be no marked differences between the bone-seeking agents in the visualisation of pathological foci. The image quality seemed to be better in the MDP 2 group than in the MDP 1 group but they were similar in other respects. The femur to soft tissue ratio decreased with increasing age in the DPD group but not in the MDP groups. With all agents worsening of scan quality with increasing age was noted and the image quality was better with men than with women. When short incubation times of radiopharmaceuticals were used before injection, the bone to soft tissue ratio was lower and the scan quality was poorer than with incubation times longer than 20 min.

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