Imaging of inflammation with granulocytes labelled in vivo

Intact versus Fragmented 99mTc-Monoclonal Antibody Imaging of Infection in Patients with Septically Loosened Total Knee Arthroplasty

OBJECTIVE: This prospective study compared the diagnostic accuracy of imaging using an intact murine antigranulocyte antibody 99mTc-besilesomab, and a murine antibody Fab' fragment 99mTc-sulesomab, in patients with suspected septically loosened total knee arthroplasty. METHODS: Images from 20 patients who underwent three-phase bone scintigraphy followed by imaging using 99mTc-besilesomab ( n = 10) or 99mTc-sulesomab ( n = 10) were evaluated and compared. Final diagnosis was determined by microbiological evaluation of aspirated synovial fluid, intraoperative samples through the clinical course, or by long-term follow-up. RESULTS: Prosthesis infection was shown in 18 patients. At 4 and 24 h after intravenous injection, absolute uptake of 99mTc-besilesomab was significantly higher than 99mTc-sulesomab in infected knee joints. Infected-to-healthy knee activity ratios were similar at 4 and 24 h for 99mTc-besilesomab and 99mTc-sulesomab. CONCLUSIONS: Both 99mTc-besilesomab and 99mTc-sulesomab had similar diagnostic accuracy for the detection of septic arthroplasty. If repeated use of immunoscintigraphy is needed for follow-up, 99mTc-sulesomab should be preferred over 99mTc-besilesomab since it is known to be well tolerated and without side effects or incompatibility reactions.

Medical imaging of the diabetic foot

Medical imaging of the diabetic foot entails a variety of imaging modalities. The diagnostic evaluation often includes a gamut of studies that include conventional radiography, CT, nuclear medicine scintigraphy, MRI, ultrasonography, and a newcomer, positron emission tomography combined with CT and leukocyte labeling. There is not yet "one best test" for sorting out the diagnostic dilemmas that are commonly encountered. Confirmation or exclusion of the frequent diagnosis of osteomyelitis often requires multiple studies, which are complementary to one another.

Comparison between Leukoscan® (Sulesomab) and Gallium-67 for the diagnosis of osteomyelitis in the diabetic foot

OBJECTIVES

The diagnosis of osteomyelitis in patients with diabetic foot is difficult both clinically and radiologically. An early diagnosis is crucial to optimize therapeutic strategy. Among the diagnostic methods currently used, scintigraphy with ex-vivo labelled white blood cells is the gold standard, but cannot be performed in all centers; therefore 67Gallium citrate (67Ga) imaging in combination with a bone scintigraphy is still widely used.

METHOD

The results of imaging 24 diabetic patients with 31 suspected osteomyelitic lesions using the antigranulocyte Fab' fragment (Sulesomab or LeukoScan or immunoscintigraphy) were prospectively compared with results from the bone scan coupled with 67Ga. The diagnosis of osteomyelitis was confirmed by either biopsy or follow-up, radiological imaging and clinical outcome.

RESULTS AND CONCLUSION

Sulesomab correctly identified 12 of 18 osteomyelitic lesions while 67Ga was able to detect only 8 of 18. Therefore the sensitivity is 67% for Sulesomab and 44% for 67Ga. Among the 13 non-osteomyelitic lesions imaging with Sulesomab was able to rule out infection in 11 cases and 67Ga in 10 cases. The specificity is therefore 85% for Sulesomab and 77% for 67Ga. Image interpretation for Sulesomab in this group of patients is occasionally suboptimal when imaging is performed at 3 hours post injection. High vascular background in the early images may obscure infection especially in small bones. Practically, scintigraphy with Sulesomab is fast and simple due to ease of labeling, no ex-vivo handling of blood, low radiation and provides rapid diagnosis. The diagnosis of osteomyelitis obtained by the antibody fragment scintigraphy influences the management (guided biopsy) and therapy. In several patients, imaging with Sulesomab was able to rule out osteomyelitis, helping to avoid useless antibiotic therapy and its associated side effects.

(99m)Tc-E-selectin binding peptide for imaging acute osteomyelitis in a novel rat model

INTRODUCTION

In the present study, (99m)Tc-radiolabelled E-selectin binding peptide ((99m)Tc-IMP-178) was investigated for its potential to image acute pyogenic osteomyelitis in a new animal model. Intraindividual comparisons were performed using an irrelevant peptide ((99m)Tc-IMP-100) to demonstrate specificity.

METHODS

An acute pyogenic osteomyelitis was induced by injecting 0.05 ml of 5% sodium morrhuate and 5x10(8) CFU of Staphylococcus aureus into the medullary cavity of the right tibia in 16 rats. Sixteen additional rats served as untreated controls. Whole-body imaging of pyogenic (n=4) and untreated (n=4) animals was performed continuously during the first 8 h (12 MBq i.v. of (99m)Tc-IMP-178 and (99m)Tc-IMP-100 for control), and one further single image was acquired after 16 h p.i. Tissue biodistribution studies were performed in 12 rats with an acute pyogenic osteomyelitis and in 12 untreated rats 1, 4 and 24 h after injection. Data of the histological/radiological and haematological investigations were obtained in all animals.

RESULTS

Histopathologically, 15 of 16 treated rats (93%) developed an acute pyogenic osteomyelitis showing a major infiltration of the bone marrow by polymorphonuclear leukocytes as well as the formation of sequestra. Haematologically, the number of leukocytes increased by 100%, the lymphocytes by 11% and the granulocytes decreased by 39%. After i.v. injection, (99m)Tc-IMP-178 rapidly cleared from the body resulting in good scintigraphic target-to-background (T/B) ratios. The highest uptake of the tracer in the pyogenic bone was observed at 60 min p.i. (0.43+/-0.02% ID.g-1 for (99m)Tc-IMP-178 and 0.30+/-0.02% ID.g-1 for (99m)Tc-IMP-100), resulting in a higher osteomyelitis-to-healthy collateral ratio with T/B of 2.40+/-0.65 ((99m)Tc-IMP-178) compared with 1.85+/-0.48 ((99m)Tc-IMP-100). No adverse reactions were seen after injection of (99m)Tc-IMP-178.

CONCLUSIONS

(99m)Tc-IMP-178 allows imaging of an acute osteomyelitic lesions, presumably by interaction of (99m)Tc-IMP-178 with activated upregulated vascular endothelium.

HM-PAO-labeled leukocyte scintigraphy in pediatric patients with inflammatory bowel disease

Leukocyte scintigraphy (LS) was performed in 20 pediatric patients with inflammatory bowel disease (IBD: 10 with ulcerative colitis, 2 with indeterminate colitis, and 8 with Crohn disease) in different stages of clinical activity. Leukocytes were separated from 15 to 60 ml venous blood and were labeled in vitro with [99mTc]HM-PAO. The segmental extent (small intestine; ascending, transverse, and descending colon; and recto-sigmoideum) of the process was determined by LS. The uptake of each bowel segment was scored in relation to the bone marrow uptake. The scintigraphic activity, calculated by summing the segment scores, was compared with laboratory parameters. The mean labeling efficacy was 76% (60-86%). The segmental extent of the process determined by LS was compared with the results of barium enema or colonoscopy with regard to 32 bowel segments. The sensitivity, specificity, and accuracy of LS were 93, 88, and 91%, respectively. Two extraintestinal manifestations (abdominal abscess and joint involvement) were also detected by LS. These lesions were verified by computed tomography (CT) (abscess) and on the basis of the clinical outcome (arthritis). The scintigraphic activity correlated with the C-reactive protein (CRP) level (r = 0.82, p < 0.001), the alpha 2-globulin level (r = 0.63, p < 0.02), the sedimentation rate (r = 0.51, p < 0.05), and the fS iron level (r = -0.66, p < 0.005). LS is applicable in pediatric patients. The method is an excellent technique for assessment of the extent of IBD in children. Extraintestinal manifestations of IBD can also be investigated by LS. The scintigraphic activity is a useful parameter for determination of the activity of IBD in children.

Anti-granulocyte immunoscintigraphy and [99mTc]hexamethylpropyleneamine-oxime-labeled leukocyte scintigraphy in inflammatory bowel disease

A prospective study was carried out on 13 patients with ulcerative colitis and 11 with Crohn's disease to compare the value of radioimmunoscintigraphy involving 99mTc-labeled antigranulocyte monoclonal antibody (BW 250/183) with that of hexamethylpropyleneamine-oxime-labeled leukocyte scintigraphy. The extent of the process (various segments of the small bowel; ascending, transverse, and descending colon; and rectosigmoideum) was determined in 115 segments by means of radioimmunoscintigraphy and leukocyte scintigraphy and compared with the results of enteroclysis and colonoscopy in 64 segments. The scintigraphic activity, calculated by summing the segment scores, was compared with clinical and laboratory parameters. During radioimmunoscintigraphy, the 24-hr fecal excretion of the antibody was measured. The two methods revealed a different extent of the process (P<0.01). The segmental sensitivity and specificity were 63% and 96% in radioimmunoscintigraphy, and 87% and 94% in leukocyte scintigraphy. Leukocyte scintigraphy proved to be superior in cases with small intestine involvement, but the methods are of similar value in cases with large bowel involvement. The scintigraphic activity determined by radioimmunoscintigraphy and the fecal excretion of monoclonal antibody correlated with seven parameters, while that determined by leukocyte scintigraphy did so with 12 variables. Both methods are of similar value for the detection of large bowel involvement, but leukocyte scintigraphy was the better method for determination of the involved segments in the small intestine. The scintigraphic activity proved a useful parameter, correlating well with the clinical and laboratory variables.

Investigation of suspected intra-abdominal sepsis: the contribution of nuclear medicine

The diagnosis of abdominal infections and inflammations often presents considerable difficulty, and various imaging techniques may be required to localize them accurately. At present, radiolabelled leucocytes offer the most widely accepted radionuclide method for imaging inflammation. Because of the many advantages of technetium-99m (99mTc) over indium-111 (111In), 99mTc-HMPAO-leucocyte scintigraphy is preferred for the investigation of acute abdominal sepsis and inflammatory bowel disease, and 111In-leucocyte scintigraphy for more chronic infections and renal sepsis. The 99mTc-HMPAO-labelled leucocytes technique is highly accurate within the first few hours postinjection, and is therefore useful also in acutely ill patients. It is sensitive in detecting abdominal abscesses in all locations except the liver and spleen. By whole body imaging, unsuspected sites and types of infection can be found. 99mTc-HMPAO-leucocyte scan is valuable also in the investigation of acute cholecystitis in problematic situations in which ultrasound is known to give misleading results, especially in acute acalculous cholecystitis. In inflammatory bowel disease it can reliably assess disease activity, but a normal scintigraphy does not exclude mild inflammation. Leucocyte scan is useful also in suspected acute appendicitis, acute diverticulitis, pelvic inflammatory disease, aortic graft infection, etc. But infection and inflammation cannot reliably be differentiated, which may cause misinterpretations in the early postoperative period. Radionuclide techniques have an important role to play in the investigation of abdominal sepsis if the nuclear medicine department can offer instant investigations when the clinical problem is acute.

Generation of bispecific monoclonal antibodies for two phase radioimmunotherapy

A two phase radioimmunotherapy based on bispecific MAbs in which one arm recognises a tumour antigen and the other a radiolabelled chelate, may prove more effective in the treatment of carcinomas than currently available immunotherapies. To establish this system we first showed that penetration into human carcinoma xenografts as well as long term retention of intact MAb outside the carcinoma cells can be obtained. Epitope saturation was not obtained however, despite the large MAb doses injected i.v. for 10 days. We then generated hybridomas producing high avidity anti-metal chelate MAbs (anti-DTPA-Y). These hybridomas were fused with hybridomas producing MAbs against CEA or GIT-mucin, and stable bispecific MAb producing quadromas were obtained. For the anti-GIT-mucin x anti-chelate MAb a purification procedure based on double anti-idiotype affinity chromatography was shown to result in greater than 95% pure bispecific immunoreactive MAb. Comparative in vivo stability studies profiled DTPA-Y as the chelate of choice for in vivo application.

Radiolabelled granulocytes in inflammatory bone disease

Inflammatory lesions in 7 patients have been investigated using labelled in vivo granulocytes. Targeting of white cells was done with a monoclonal antibody, mouse IgG1 reacting with NCA (non-specific crossreacting antigen) and CEA (carcinoembryonic antigen) (BW 250/183) labelled with 99mTc. All inflammatory lesions were visualized, with excellent quality scintigram, between 3-6 and 24 h after the injection. Because the antibody can be stored in a freeze-dried form and labelled at any time with 99mTc without cell separation being necessary, the method appears to be suitable even for use in acute diagnosis.

Blood cell labeling with 99mTc: progress and perspectives

Blood cell labeling with 99mTc has progressed through various developmental phases. In the case of red cell labeling, the science seems to have matured sufficiently, although minor refinements in the procedures will no doubt continue to be made. During the last 3 to 5 years, there has been a resurgence of interest in labeling leukocytes and platelets with 99mTc. As a result of these efforts, the techniques for these cell types appear to be developing slowly, having finally come out of their infancy. Progress in these directions over the last 3 1/2 years is summarized and discussed in this article. Emerging techniques that offer the promise of combining simplicity and convenience with reliable and reproducible data are highlighted. Mechanisms involved in the various labeling approaches, if studied and understood, are included. Recent efforts on cell labeling with 99mTc using the monoclonal antibody approach are summarized. Although results in this area are quite preliminary, the monoclonal antibody approach holds the greatest promise for labeling leukocytes and platelets in vivo, and thus overcoming the biggest drawback of current techniques, ie, cell separation and handling before labeling. This is a US government work. There are no restrictions on its use.