Speed of accumulation of 111In-labelled granulocytes in focal non-osseous inflammatory processes

Using a method of 111In-oxine granulocyte labelling in diluted plasma, we performed 162 scintigraphic studies in 159 patients with suspected non-osseous infection. We obtained a positive predictive value of 82%, and a negative predictive value of 97%, i.e. the method is very sensitive, albeit less specific. Sequential imaging showed around 50% of the scintigrams to turn positive at 30 min after the injection, the most rapid accumulation being seen in cases of superficial soft tissue infections and in pulmonary and pleural infections, cerebral abscesses showing a rather sluggish accretion of activity, urinary tract infections, abdominal abscesses and bowel inflammation accumulating activity at an intermediate rate. Our results indicate that the described method is sensitive, and that the sequential scintigraphic approach allows an early diagnosis in most cases, and facilitates the interpretation of delayed scans.     

Analysis of factors that may affect the speed of accumulation of 111In-labelled granulocytes at sites of inflammation

The mechanisms governing the accumulation of granulocytes in inflammatory lesions are poorly understood. Using a sensitive method of sequential 111In-granulocyte scintigraphy, we recorded the speed of focal 111In-granulocyte accumulation in 70 patients with non-osseous inflammatory and infectious foci, with special reference to the influence exerted by the duration of disease, patient age, body temperature, antibiotic therapy and initial trapping of granulocytes in the lungs. About 50% of the images had turned positive at 30 min after injection. Except for patients with urinary tract infections, the age of the patient did not influence the speed of 111In-granulocyte accumulation; nor did the duration of disease, antibiotic therapy or degree of initial granulocyte hold-up in the lungs. High fever, on the other hand, presumably reflecting an intense inflammatory reaction, was associated with an accelerated focal 111In-granulocyte accumulation, indicating that properties of the inflammatory process per se are major determinants of the speed of accumulation of 111In-labelled granulocytes in inflammatory processes.     

Targeting of lymphocytes with 111In-labelled monoclonal antibodies

In this paper, we emphasize the rationale and work-up studies for using two radiolabelled anti-lymphocyte monoclonal antibodies for in vivo application as radiolabelling agents for T and B cells. In vitro experimental work involved radioimmunoassays on human lymphoid cell lines and anticoagulated whole blood with identification of relevant binding kinetics in terms of antibody internalization and elution. We tested also for the effect of the radiolabelled monoclonal antibodies on in vitro cell function defined as mitogen-induced proliferation in whole blood. As a final work-up in an animal model, the distribution of both unlabelled and 111In-labelled anti-Pan T cell monoclonal antibody was studied in the rat. Results from the in vitro experiments pointed to the possibility of using the described technique for specific lymphocyte radiolabelling. The in vivo application enabled us to identify optimal doses of antibody and radioactivity which showed agreement with the in vitro data.     

White cells radiolabelled with 111In and 99Tcm--a study of relative sensitivity and in vivo viability

In this study a comparison between the classical (111In oxine) and the newer (99Tcm HMPAO) technique of labelling leucocytes is reported. The behaviour in vivo and the relative sensitivity in the detection of infection (chest and bone) and inflammatory bowel disease (IBD) is presented. Simultaneous dual-radionuclide gamma camera acquisition methodology was applied to study 99 patients, 18 with chest infection, 26 with bone infection, 41 with IBD and 14 with other pathological conditions. The mean (1 SD) 50% washout time from the lungs was 483.03 (79.10) s for 99Tcm HMPAO-labelled white blood cells and 475.85 (83.79) s for 111In oxine-labelled white cells (r = 0.81). Concordance between the two techniques was 94% in the chest-infection group of patients, 88% in the bone-infection group and 71% in the localization of IBD.     

An improved method for the quantification of the in vivo kinetics of a representative population of 111In-labelled human platelets

The recommended and commonly used methods for the isolation of platelets from whole blood do not harvest a representative platelet population. There is evidence that these methods may result in the loss of a functionally more active platelet subpopulation. We describe a method whereby a completely representative population of platelets was isolated from the whole blood of 28 normal human volunteers by repeated washing of platelets from the red-cell layer. The harvesting efficiency was 98.3% +/- 2.8%. The platelets were labelled with 111In-oxine in a saline milieu with a labelling efficiency of 86.4% +/- 6.8%. The disappearance of reinjected labelled autologous platelets from the circulation was almost linear, and the mean platelet survival was estimated to be 224 +/- 23 h. At equilibrium, 61% +/- 12% of the labelled platelets were recovered from the circulation. The in vivo distribution at equilibrium and the sites of sequestration of the senescent labelled platelets were determined by geometric-mean whole-body quantification in six of the volunteers. This improved method permits accurate quantification of organ 111In radioactivity. Following reinjection, the labelled platelets pooled in the spleen and the accumulated activity can be presented by a single exponential function. At equilibrium, 31.1% +/- 6.1% and 9.6% +/- 1.2% of the platelets were in the spleen and liver, respectively. Splenic and hepatic radioactivity increased significantly with time, and at the end of the platelet life span, 35.6% +/- 9.7% and 28.7% +/- 8.3% of the labelled platelets were sequestrated in these organs, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

A comparative distribution study of 111In-labelled DTPA and TTHA monoclonal antibody conjugates in a choriocarcinoma xenograft model

Conjugates of the chelating agents DTPA and TTHA with a monoclonal anti-HCG were prepared. The tissue distribution of the ¹¹¹In-labelled conjugates and also ¹¹¹In-citrate was studied in mice bearing human choriocarcinoma xenografts. The antibody conjugates both gave high liver and spleen radionuclide accumulation. Elevated femur levels were observed for the TTHA conjugate and ¹¹¹In-citrate. Generally the DTPA conjugate showed the highest tumor/tissue ratios, although its tumor/blood ratio was lower than the other two materials. The results infer that the DTPA conjugate has the greatest utility as an imaging agent but that it would require a background subtraction technique.     

Quantification of the distribution of 111In-labelled platelets in organs

A simple and practical approach to the in vivo quantification of ¹¹¹indium-oxine labelled blood platelets with a scintillation camera and computer assisted imaging system was evaluated. Radioactivity of the 172 and 247 keV energies was measured in a phantom at various source distances from the collimator and the accuracy of anterior and posterior mode measurements compared with that of the geometrical mean (GM) method, with and without correction for Compton scatter (CS). Organ radioactivity, expressed as a percentage of whole body radioactivity, was determined in vivo in five baboons and the accuracy of the methods verified by post mortem quantification in the animals. Measurement in the anterior mode significantly overestimates hepatic and underestimates splenic radioactivity; posterior mode quantification reverses these results. Correction with the GM method made the accuracy and reproducibility very acceptable. Further correction for anterior-posterior attenuation and/or CS did not improve results materially. The GM method could readily be applied in five human subjects. This study shows that the GM method is an accurate and practical method for the in vivo quantification of organ and regional distribution of ¹¹¹In-labelled platelets.     

99Tcm-labelled HSA-nanocolloid versus 111In oxine-labelled granulocytes in detecting skeletal septic process

Fifty-seven investigations of the skeletal system were performed on 54 patients, using a 99Tcm-labelled nanometer-sized HSA colloid in a crossover comparison with 111In oxine-labelled granulocytes for the detection of sites of infection. The findings were in agreement in 55 out of 57 investigations (96.5%). Based on 44 studies in which a final clinical diagnosis was obtained, both methods were found to display the same specificity (93%), whilst the sensitivity of 99Tcm nanocolloid scintigraphy (87%) was slightly higher than that obtained with 111In leucocyte scintigraphy (81%). In our opinion, 99Tcm nanocolloid is easier to use and the total duration of the investigation is considerably shorter. The use of 99Tcm is scintigraphically more advantageous and, with the dosage required, the absorbed radiation dose to the red bone marrow is three times lower than with 111In granulocytes. For the detection and therapy monitoring of osteomyelitis, as well as for the investigation of arthroplasties suspected of infective loosening, we consider scintigraphy with 99Tcm nanocolloid to be equivalent to leucocyte scintigraphy. Identical findings were obtained with both tracers in suspected spondylodiscitis.     

111In-labelled somatostatin analogues in a rat tumour model: somatostatin receptor status and effects of peptide receptor radionuclide therapy

Purpose Peptide receptor scintigraphy with the radioactive somatostatin analogue ¹¹¹In-DTPA-octreotide is a sensitive and specific technique to show in vivo the presence of somatostatin receptors on various tumours. Since ¹¹¹In emits not only gamma rays but also therapeutic Auger and internal conversion electrons with a medium to short tissue penetration (0.02–10 m and 200–550 m, respectively), ¹¹¹In-DTPA-octreotide is also being used for peptide receptor radionuclide therapy (PRRT). In this study we investigated the therapeutic effects of ¹¹¹In-DTPA-octreotide in tumours of various sizes. Regrowth of a tumour despite PRRT with ¹¹¹In-DTPA-octreotide may be due to the lack of crossfire from ¹¹¹In, whereby any possible receptor-negative tumour cell can multiply. We therefore also investigated the somatostatin receptor status of the tumour before and after PRRT.Methods The radiotherapeutic effects of different doses of ¹¹¹In-DTPA-octreotide in vivo were investigated in Lewis rats bearing small (1 cm²) or large (8 cm²) somatostatin receptor-positive rat pancreatic CA20948 tumours expressing the somatostatin receptor subtype 2 (sst₂). In addition, the somatostatin receptor density on the tumour after injection of a therapeutic labelled somatostatin analogue was investigated when the tumour was either declining in size or regrowing after an initial reduction in size. To initiate a partial response of the tumour (so that regrowth would follow) and not a complete response, a relatively low dose was administered.Results Impressive radiotherapeutic effects of ¹¹¹In-labelled octreotide were observed in this rat tumour model. Complete responses (up to 50%) were found in the animals bearing small (1 cm²) tumours after at least three injections of 111 MBq or a single injection of 370 MBq ¹¹¹In-DTPA-octreotide, leading to a dose of 6.3–7.8 mGy/MBq (1–10 g tumour). In the rats bearing the larger (8 cm²) tumours, the effects were much less pronounced and only partial responses were achieved in these groups. Clear sst₂ expression was found in the control as well as in the treated tumours. A significantly higher tumour receptor density (p<0.001) was found when the tumours regrew after an initial decline in size after low-dose PRRT in comparison with the untreated tumours.Conclusion Therapy with ¹¹¹In-labelled somatostatin analogues is feasible but should preferably start as early as possible during tumour development. One might also consider the use of radiolabelled somatostatin analogues in an adjuvant setting after surgery of somatostatin receptor-positive tumours in order to eradicate occult metastases. We showed that PRRT led to an increase in the density of somatostatin receptors when the tumours regrew after an initial decline in size because of PRRT. Upregulation of the somatostatin receptor may lead to higher uptake of radiolabelled peptides in therapeutic applications, which would probably make repeated injections of radiolabelled peptides more effective.     

In vivo labelling of granulocytes using 123I-tagged anti-granulocyte antibodies

On the basis of previous work with various monoclonal antibodies (Mab) raised against carcino-embryonic antigen (CEA), the anti-CEA Mab 47 was identified which selectively reacted with a surface glycoprotein (95 kDa; NCA 95) of normal human granulocytes. This new tracer was quality tested and radioiodinated with 123I (123I Mab 47) for clinical use according to established procedures. Extended in vitro studies revealed a high selectivity for granulocytes without inhibiting their vital functions. In vivo cell binding to the granulocyte pool was completed very rapidly and remained unchanged over 24 h. For clinical use one dose consisting of 120 mcg of Mab was labelled with 4-5 mCi of 123I. Clinical interest was mainly concentrated on cases of osteomyelitis, infected allografts and abdominal and brain abscesses. After injection of 123I Mab 47, infectious lesions were usually seen after 3-5 h or could be excluded after 24 h. Because of high counting rates the image quality was excellent and single photon emission computerized tomography (SPECT) could be performed for an exact topographical localization of the lesions. No adverse reactions have been seen. It is concluded that there are distinct advantages of the new method compared with scanning of 111In-labelled leucocytes. However, despite this and the low dose of antibodies administered, we recommend restriction of immunoscintigraphy of infectious lesions before a clinically relevant immunization can be excluded.     

In vivo Studies of 111In-Labelled canine Lymphocytes

[¹¹¹In]oxine was used to label canine periperal blood lymphocytes from two normal animals and one animal with breast carcinoma. Using 150 μCi of [¹¹¹In]oxine to label 50 × 106 cells yielded a labeling efficiency between 40 and 75% and a viability of about 95%. Gamma camera images obtained 24–44 h after injection showed uptake in the subcutaneous lymph nodes of the head, neck, axilla, pelvis and popliteal regions. Uptake in the liver, spleen, bowel, and bone marrow was also seen. In the animal bearing breast carcinoma, uptake occurred in the tumor, lungs and in a draining sinus in the left axilla. These results suggest that ¹¹¹In labeled lymphocytes are useful in visualizing regional lymph nodes and may be valuable in assessing tumor recognition by these cells in vivo.     

Detection of muscle necrosis in dermatomyositis by 111In-labelled antimyosin Fab fragments

This paper presents the findings on two patients with a final diagnosis of dermatomyositis in whom 111In-antimyosin imaging revealed diffuse muscle necrosis of the limbs. The potential application of this scintigraphic procedure for diagnosis and follow-up of patients with dermatomyositis-polymyositis is addressed.     

Autologous 111In-oxine-labeled granulocytes in Yersinia infections

Autologous ¹¹¹In-oxine-labeled granulocytes have proved to be valuable for the localization of inflammatory bowel diseases, especially Crohn's disease and ulcerative colitis. Other rare inflammatory bowel diseases also yield positive ¹¹¹In scans. One case of Yersinia infection of the terminal ileum (Yersinia enterocolitica) showing an accumulation of ¹¹¹In-oxine-labeled granulocytes 0.5, 4, and 24 h after the reinjection of the labeled cells is described. The 4-day fecal excretion of ¹¹¹In-oxine granulocytes showed a slight inflammatory activity of the terminal ileum. One negative scan is reported in a cotrimoxazoletreated patient with Yersinia infection.     

In vivo tracking of 111In-labeled bone marrow mesenchymal stem cells in acute brain trauma model

IntroductionThis study was to evaluate the in vivo distribution of intravenously transplanted bone marrow-derived mesenchymal stem cells (BMSCs) in an acute brain trauma model by ¹¹¹In-tropolone labeling.MethodsRat BMSCs were labeled with 37 MBq ¹¹¹In-tropolone. Their labeling efficiency and in vitro retention rate were measured. The viability and proliferation of labeled BMSCs were evaluated for 14 days after labeling. The biodistribution of ¹¹¹In-labeled BMSCs in trauma models was compared with those of sham-operated rats and normal rats on gamma camera images. The migration of ¹¹¹In-BMSCs to the traumatic brain was evaluated using confocal microscope.ResultsThe labeling efficiency of ¹¹¹In-BMSCs was 66±5%, and their retention rate was 85.3% at 1 h after labeling. There was no difference in the number of viable cells between ¹¹¹In-BMSCs and controls at 48 h after labeling. However, the proliferation of ¹¹¹In-BMSCs was inhibited after the third day of labeling, and it did not reach confluency. On gamma camera images, most of the ¹¹¹In-BMSCs uptake was observed in the liver and spleen at the second day of injection. The brain uptake of ¹¹¹In-BMSCs was detected prominently in trauma models (1.4%) than in sham-operated (0.5%) or normal rats (0.3%). Radiolabeled BMSCs were observed at the traumatic brain on the confocal microscope as they have a homing capacity, although its proliferation capacity was suppressed.ConclusionAlthough growth inhibition by ¹¹¹In-labeling need to be evaluated further prior to use in humans, ¹¹¹In-labeled BMSCs are useful for the tracking of intravenously transplanted mesenchymal stem cells in brain disease models.     

Autologous 111In-oxine-labeled granulocytes in Yersinia infections

Autologous 111In-oxine-labeled granulocytes have proved to be valuable for the localization of inflammatory bowel diseases, especially Crohn's disease and ulcerative colitis. Other rare inflammatory bowel diseases also yield positive 111In scans. One case of Yersinia infection of the terminal ileum (Yersinia enterocolitica) showing an accumulation of 111In-oxine-labeled granulocytes 0.5, 4, and 24 h after the reinjection of the labeled cells is described. The 4-day fecal excretion of 111In-oxine granulocytes showed a slight inflammatory activity of the terminal ileum. One negative scan is reported in a cotrimoxazole-treated patient with Yersinia infection.     

In-111 granulocyte response to intervening surgery. Evidence of sustained in vivo viability

A patient with chronic osteomyelitis had surgery performed between the early and delayed images of an In-111 granulocyte scan. The early images showed no uptake, while the delayed images demonstrated marked soft tissue uptake, which was felt to be secondary to the inflammation of the intervening surgery. It was concluded that granulocytes, when labeled with In-111, remain viable and can respond to inflammation that occurs after their injection.     

111In-labelled leucocyte and 99mTc-methylene diphosphonate bone scanning in pelvic osteomyelitis

A positive 99mTc-methylene diphosphonate bone scan was obtained in a case of pelvic osteomyelitis in a 15-year-old girl. An 111In-labelled leucocyte scan confirmed the presence of pus, gave a more accurate anatomical location than was obtained by the bone scan, and enabled the most suitable surgical route to be selected.     

111In-labelled leucocyte and 99mTc-methylene diphosphonate bone scanning in pelvic osteomyelitis

A positive ^99mTc-methylene diphosphonate bone scan was obtained in a case of pelvic osteomyelitis in a 15-year-old girl. An ¹¹¹In-labelled leucocyte scan confirmed the presence of pus, gave a more accurate anatomical location than was obtained by the bone scan, and enabled the most suitable surgical route to be selected.