Stroke results in considerable morbidity and mortality. Prevention is therefore of particular importance. On the basis of large clinical trials, carotid endarterectomy (CEA) is performed in selected patient groups to prevent stroke. Patient symptomatology and degree of carotid stenosis are the main clinical grounds to perform CEA. However, many individual patients undergo surgery with its attendant risks without taking advantage of it, whereas in others CEA is probably incorrectly withheld. There is therefore an urgent need for new adjuncts to identify high-risk subgroups of patients who particularly benefit from potentially hazardous interventions. Multiple noninvasive imaging modalities have shown their potential to differentiate high-risk, vulnerable carotid plaques from stable plaques. The ultimate goal is to implement one or a combination of these imaging modalities in daily clinical practice. This review gives an up-to-date overview of the clinical potential of these imaging modalities in identifying patients with carotid atherosclerosis who are at high risk for developing stroke. Advantages and limitations of each imaging technique are outlined. Additionally, recommendations for future research are presented.
Differentiation between viable myocardium and scar tissue in segments with abnormal contraction has important consequences in the clinical management of patients with coronary artery disease. Positron emission tomography (PET) can identify viable tissue using 18F-fluorodeoxyglucose (FDG). However, application of PET for daily routine is limited. In this study, FDG uptake was visualized with single photon emission computed tomography (SPECT) and compared with regional perfusion assessed with thallium-201 (201Tl) SPECT. The scintigraphic findings were related to regional wall motion determined with two-dimensional echocardiography. Patients (n = 9) with wall motion abnormalities underwent FDG SPECT and resting 201Tl SPECT. To control the metabolic status patients were studied with a hyperinsulinaemic euglycemic clamp during FDG SPECT. Analysis of reconstructed data was performed visually and semiquantitatively using circumferential profiles. High-quality images were obtained. Eight 201Tl defects showed concordantly decreased FDG uptake (metabolism-perfusion matches) indicating scarred tissue, whereas six regions of hypoperfusion demonstrated a relatively increased FDG uptake (mismatches), suggesting viable myocardium. Semiquantitative analysis confirmed visual findings. Mean 201Tl and FDG activities were not significantly different in matching defects. In mismatches the mean FDG activity was 81 +/- 11% vs 64 +/- 9% mean 201Tl activity (P < 0.0001). In four of six segments with increased FDG uptake, two-dimensional echo revealed hypokinesia. Seven of eight regions with a matching defect in contrast were akinetic. Thus, in the areas with a mismatch contractility was preserved. We conclude that FDG uptake can be visualized with SPECT. Furthermore, our preliminary observations suggest that this approach can identify viable tissue.
Red marrow is usually the dose-limiting organ during radioimmunotherapy. Several non-invasive approaches to calculate the red marrow dose have been proposed. We compared four approaches to analyse the differences in calculated red marrow doses. The data were obtained from immunoscintigraphy of two antibodies with different red marrow kinetics [iodine-131-16.88 IgM and indium-111-OV-TL-3 F(ab')2]. The approaches are based on, respectively, homogeneously distributed activity in the body, a red marrow-blood activity concentration ratio of 0.3, scintigraphic quantification, and a combination of the second and third approaches. This fourth approach may be more adequate because of its independence from the chosen antibody. In addition, the influence of activity accumulation in liver, kidneys or cancellous bone on red marrow dose was studied. The calculated red marrow dose varied between 0.14 and 0.42 mGy/MBq for 111In-OV-TL-3 and between 0.13 and 0.68 mGy/MBq for 131I-16.88. If the radiopharmaceutical shows high affinity for cancellous bone or another organ situated near the red marrow, the activity in these organs must be included in dose calculations. This study shows a large variation in calculated red marrow dose and selection of the definitive non-invasive approach awaits validation.
Safety and feasibility of tumor targeting with radiolabeled monoclonal antibodies was studied in 28 patients suspected of having ovarian carcinoma, after i.v. administration of 1 mg F(ab')2 fragments of the murine monoclonal antibody OV-TL 3, labeled with 150 MBq Indium-111. There were no adverse reactions, hematological and biochemical serum parameters were stable. In one patient a (subclinical) HAMA-response was found. Plasma clearance of the immunoconjugate was biphasic with half lives of t(1/2)}alpha = 1.4+/-0.8 h and t(1/2)}beta = 25.1+/-3.7 h, resulting in an optimal time period for immunoscintigraphy at 24-48 h after administration. In 20 patients, undergoing extensive explorative surgery, a total of 271 samples of tumorous and normal tissues were analyzed for radiolabel uptake and tumor presence. The mean uptake in tumor deposits was 5.6 times (range 2.2-19.3) as high as the uptake in normal tissues (fat, peritoneum, muscle, skin). The diagnostic accuracy of immunosctigraphy was compared with that obtained with computer tomography, magnetic resonance imaging, ultrasonography and physical examination. While pelvic localizations were equally well detected by all methods, 48% of the abdominally located tumor deposits were correctly diagnosed by immunoscintigraphy, with only 12% detected by ultrasonography, 8% by CT-scanning and physical examination, and 6% by MRI. Immunoscintigraphy has potential as a diagnostic tool in ovarian cancer patients and biolocalization results justify further research into the therapeutic application of labeled monoclonal antibodies.
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