Scintigraphie cérébrale de perfusion et troubles cognitifs d’origine vasculaire

The vascular cognitive impairment (VCI) is a heterogeneous group of various etiologies, which share a presumed vascular cause. Although the age is the most important risk factor, the cardiovascular risk factors are also involved. A relatively high proportion of these cognitive disorders could be prevented or delayed. Only the treatment of arterial hypertension is recognized as a factor in preventing vascular dementia. MRI is the examination of choice for the investigation of cerebral vascular pathology. However, this morphological imaging is insufficient and does not provide useful functional information. Perfusion brain SPECT is not widely used in the exploration of VCI. Strategies for screening VCI are not standardized and long-term studies are needed to establish the better prevention of cognitive vascular disorders. This article aims to summarize the possible benefit of cerebral perfusion SPECT in the exploration of VCI.     

Cinétiques de la fixation du 18F-FDG dans les structures cérébrales : faisabilité et résultats préliminaires

ObjectDynamic positron emission tomography (dyn-PET) acquisitions using the radiotracer ¹⁸F-deoxyglucose (¹⁸F-FDG) are mainly developed in research studies of brain PET in kinetic modelling to determine the local glucose consumption rate. This procedure is difficult to establish, due to its requirement for blood sampling. Here, we propose a simple approach to constructing time–activity curves (TACs) for four different brain structures (the arterial & venous regions and grey & white matter) based on direct image measurements on chronologically reconstructed image volumes of regions of interest.Materials and methodsWe applied our processing on 14 control subjects to extract their physiological state. We defined the reference ¹⁸F-FDG kinetic curves as a “population averaged TAC” for four structures. To increase the curves accuracy, our method included the evaluation of two normalization based on the integral of the activity curve in the arteries and the veins.ResultsThe method showed discrimination between artery, venous, grey and white matters. The two normalization methods significantly reduce the dispersion for the grey and white matter curves and that venous normalization showed the best overall efficiency.ConclusionWe have designed and evaluated an approach for directly defining PopAv_TACs which are representative of given anatomical structures.     

La caméra à semi-conducteur D-Spect : aspects techniques et applications cliniques

Clinical practice in nuclear medicine has largely changed in the last decade, particularly with the arrival of PET/CT and SPECT/CT. New semiconductor cameras could represent the next evolution in our nuclear medicine practice. Due to the resolution and sensitivity improvement, this technology authorizes fast speed acquisitions, high contrast and resolution images performed with low activity injection. The dedicated cardiology D-Spect camera (Spectrum Dynamics, Israel) is based on semiconductor technology and provides an original system for collimation and images reconstruction. We describe here our clinical experience in using the D-Spect with a preliminary study comparing D-DPECT and conventional gamma camera.     

Effets de l’âge et du genre sur la perfusion cérébrale régionale étudiée par deux méthodes d’analyse statistique voxel-par-voxel

Fully automated analysis programs have been applied more and more to aid for the reading of regional cerebral blood flow SPECT study. They are increasingly based on the comparison of the patient study with a normal database. In this study, we evaluate the ability of Three-Dimensional Stereotactic Surface Projection (3D-SSP) to isolate effects of age and gender in a previously studied normal population. The results were also compared with those obtained using Statistical Parametric Mapping (SPM99).MethodsEighty-nine ^99mTc-ECD-SPECT studies performed in carefully screened healthy volunteers (46 females, 43 males; age 20–81 years) were analysed using 3D-SSP. A multivariate analysis based on the general linear model was performed with regions as intrasubject factor, gender as intersubject factor and age as covariate.ResultsBoth age and gender had a significant interaction effect with regional tracer uptake. An age-related decline (p < 0.001) was found in the anterior cingulate gyrus, left frontal association cortex and left insula. Bilateral occipital association and left primary visual cortical uptake showed a significant relative increase with age (p < 0.001). Concerning the gender effect, women showed higher uptake (p < 0.01) in the parietal and right sensorimotor cortices. An age by gender interaction (p < 0.01) was only found in the left medial frontal cortex. The results were consistent with those obtained with SPM99.Conclusion3D-SSP analysis of normal rCBF variability is consistent with the literature and other automated voxel-based techniques, which highlight the effects of both age and gender.     

Anticorps anti-spermatozoïdes: techniques de dépistage et interprétation des résultats

Since the first publication on the detection of sperm-agglutinating antibodies in infertile men, multiple assays have been described. The most useful tests are able to detect antibodies bound to the sperm membrane of motile spermatozoa. The immunobeads test (IBT) is considered to be the most advantageous in terms of its sensitivity, the low incidence of false-positive results, and its ability to localize antibodies of different immunoglobulin classes on the sperm surface. The IBT assay can be used in parallel with the mixed antiglobulin reaction (MAR), to detect sperm-associated antibodies in the ejaculates of infertile men, the most rational way to test for antisperm antibodies (ASA) in males. In view of the high level of agreement between the two assays, MAR, the easier of the two, may be used as a first step in the detection of these antibodies. A positive MAR must be confirmed by IBT, as this assay is more specific for the detection of IgA antibodies. The clinical significance of sperm-associated antibodies is usually established according to the proportion of motile spermatozoa coated with immunobeads, its class and its localization on the sperm surface. However, binding of immunobeads does not provide any information about the antigens against which the antibodies are directed. As the functional effects of sperm-associated antibodies may vary as a function of their antigenic specificities, other assays, using purified fertilization related antigens, are necessary to establish, for each individual, the specific impact of the antibodies on the fertilization process. The indirect IBT assay has recently become the most widely used test to detect the various classes of ASA in serum and cervical mucus of infertile women and in the serum and seminal fluid of infertile men, in combination with the direct assay described above. However, in most laboratories, it is performed with only one dilution of the biological fluid tested, usually a low dilution, so that antibody levels of no significance for fertility could be detected. This may explain a recente debate (Human Reprod, 1999) on the significance of ASA as a cause of infertility. At present, and in the absence of standardized assays able to identify the antigens involved in each individual immune reaction, antibody assays, as detected by the IBT assay, in the serum and/or genital secretions of infertile subjects might provide useful clinical guidance.     

Scintigraphie myocardique et séquelles de myocardite : présentation d’un cas clinique

Acute and subacute myocarditis are well-defined pathological entities but it is often difficult to identify them because their clinical expression is variable and the diagnosis is histological showing myocardial inflammation associated with degeneration and/or necrosis. Often symptoms are similar to those of acute pericarditis with “chest-crushing” pain that mimics myocardial infarction and prompts practitioners to request angiography, especially when there are cardiovascular risk factors. We report the case of a 61-year-old patient with neither cardiac history nor cardiovascular risk factor who consulted for a long and self-limited atypical chest pain with normal clinical examination and electrocardiogram. Myocardial perfusion scintigraphy showed a non-reversible photopenic area suspected of being a nontransmural necrosis or an artifact. The discovery of inferolateral hypokinesis of left ventricle on echocardiography led to perform a coronary angiography which was finally normal. Cardiac MRI allowed to diagnose scars of a previous episode of myocarditis.     

Intérêt d’une semi-quantification et d’une analyse statistique automatique pour l’interprétation de la tomoscintigraphie cérébrale de perfusion dans la maladie d’Alzheimer

IntroductionAs the visual interpretation of the brain perfusion SPECT for the diagnosis of Alzheimer's disease might be difficult, it is wished to benefit from techniques allowing to improve the diagnostic accuracy especially for the inexperienced readers.Materials and methodsThree readers retrospectively interpreted 77 ^99mTc-ECD SPECT studies within the context of suspected neurodegenerative disease. The probability of Alzheimer's disease was quoted from 1 to 5, and the optimum sensitivity and specificity values were determined from ROC curves. The readers also attributed a hypoperfusion score to 13 brain regions; a diagnosis was obtained from this semi-quantification using a simple logic rule. The SPECT scans were also analyzed using the Planet Neuro software and a diagnosis was reached from a threshold for 2 of the 90 analyzed regions. The gold standard was established by a comprehensive neurological evaluation with at least 5 years of follow-up.ResultsThe sensitivities and specificities of the three readers were 50 %, 56 %, 28 % and 76 %, 83 % and 90 %, respectively. Using the semi-quantification they were 50 %, 67 %, 61 % and 54 %, 85 %, 69 %. The results of two readers were more in agreement. Using the automatic quantification, sensitivity was 78 % and specificity 81 %.ConclusionThe semi-quantification seems to ameliorate the results of and the agreement between certain readers. However, the automatic quantification seems to be the only way of assisting all of the readers to improve their diagnostic performances.