La neuroimagen molecular en las demencias degenerativas / Molecular neuroimaging in degenerative dementias

En el contexto de las limitaciones de la imagen estructural, los estudios de perfusión y metabolismo cerebral con SPECT y PET han aportado información relevante en el estudio del deterioro cognitivo. La introducción de radiotrazadores de amiloide cerebral ha replanteado la estrategia diagnóstica en torno a la enfermedad de Alzheimer (EA), considerada actualmente un «continuum». En este nuevo paradigma, la carga amiloide creciente se asocia al estadio preclínico y de deterioro cognitivo leve (DCL) de la enfermedad y ha podido ser objetivada en exploraciones «in vivo» gracias a la introducción del 11C-PIB y los tomógrafos PET. Las características de la imagen 11C-PIB son una elevada retención específica cortical cerebral en los casos positivos, con distribución topográfica característica y no retención en los negativos. Junto a la PET con 18F-FDG constituye la base de la neuroimagen molecular como biomarcador y se está valorando su significado pronóstico en estudios longitudinales. La PET con 11C-PIB se ha consolidado como la técnica óptima para valorar la presencia de amiloide cerebral, pero la necesidad de un ciclotrón cercano para su síntesis limita su disponibilidad, por lo que se están introduciendo trazadores análogos marcados con 18F. Nuestra experiencia en los 2 últimos años aplicando el 11C-PIB, primero en fase investigadora y después en la clínica, ha constatado la utilidad de la técnica en el campo asistencial, tanto de forma aislada como en combinación con la FDG. Así pues, la imagen de amiloide ha demostrado ser una herramienta útil en el diagnóstico diferencial de la demencia y un método prometedor de diagnóstico precoz y evaluación de tratamientos futuros(AU)

In the context of the limitations of structural imaging, brain perfusion and metabolism using SPECT and PET have provided relevant information for the study of cognitive decline. The introduction of the radiotracers for cerebral amyloid imaging has changed the diagnostic strategy regarding Alzheimer's disease, which is currently considered to be a «continuum.» According to this new paradigm, the increasing amyloid load would be associated to the preclinical phase and mild cognitive impairment. It has been possible to observe «in vivo» images using 11C-PIB and PET scans. The characteristics of the 11C-PIB image include specific high brain cortical area retention in the positive cases with typical distribution pattern and no retention in the negative cases. This, in combination with 18F-FDG PET, is the basis of molecular neuroimaging as a biomarker. At present, its prognostic value is being evaluated in longitudinal studies. 11C-PIB-PET has become the reference radiotracer to evaluate the presence of cerebral amyloid. However, its availability is limited due to the need for a nearby cyclotron. Therefore, 18F labeled radiotracers are being introduced. Our experience in the last two years with 11C-PIB, first in the research phase and then as being clinically applied, has shown the utility of the technique in the clinical field, either alone or in combination with FDG. Thus, amyloid image is a useful tool for the differential diagnosis of dementia and it is a potentially useful method for early diagnosis and evaluation of future treatments(AU)

Molecular neuroimaging in degenerative dementias.

In the context of the limitations of structural imaging, brain perfusion and metabolism using SPECT and PET have provided relevant information for the study of cognitive decline. The introduction of the radiotracers for cerebral amyloid imaging has changed the diagnostic strategy regarding Alzheimer's disease, which is currently considered to be a "continuum." According to this new paradigm, the increasing amyloid load would be associated to the preclinical phase and mild cognitive impairment. It has been possible to observe "in vivo" images using 11C-PIB and PET scans. The characteristics of the 11C-PIB image include specific high brain cortical area retention in the positive cases with typical distribution pattern and no retention in the negative cases. This, in combination with 18F-FDG PET, is the basis of molecular neuroimaging as a biomarker. At present, its prognostic value is being evaluated in longitudinal studies. 11C-PIB-PET has become the reference radiotracer to evaluate the presence of cerebral amyloid. However, its availability is limited due to the need for a nearby cyclotron. Therefore, 18F labeled radiotracers are being introduced. Our experience in the last two years with 11C-PIB, first in the research phase and then as being clinically applied, has shown the utility of the technique in the clinical field, either alone or in combination with FDG. Thus, amyloid image is a useful tool for the differential diagnosis of dementia and it is a potentially useful method for early diagnosis and evaluation of future treatments.

[Assessment of cerebral blood flow in patients with eating disorders in the acute clinical phase using Tc99m-HMPAO spect]. / Valoración del flujo sanguíneo cerebral en pacientes con trastornos de la conducta alimentaria en fase aguda mediante SPECT con HMPAO-Tc99m.

OBJECTIVE: To assess the status of cerebral perfusion in patients with eating disorders (ED) in the acute phase of the disease. MATERIALS AND METHODS: Seventeen patients, with a mean age of 22 years, diagnosed with ED according to DSM-III-R (Diagnostic and Statistical Manual of Mental Disorders) criteria and under close clinical monitoring were studied in the initial acute phase of their disease. Brain SPECT with 15 mCi of Tc99m HMPAO was performed on all patients and assessed using visual and semi-quantitative analysis. The latter was carried out by obtaining left/right indices in sixteen symmetrical 5 x 5 pixel regions of interest (ROI) in three transverse slices, one below the cantho-meatal line and two above, at 2 and 5 cm, respectively. RESULTS; Visual analysis showed hypoperfusion of the anteroinferior region of the left temporal lobe in 7/17 patients, and in the homonymous region of the right temporal lobe in 1/17. Semi-quantitative analysis did not show statistically significant differences in the slices above the cantho-meatal line when the means of the asymmetry indices were compared between the anterior (frontal), middle (temporal and parietal) and posterior (occipital) regions of each slice, obtaining values ranging between 0.99 +/- 0.05 and 1.02 +/- 0.03. However, in the lowest slice, the anterior (temporal) region showed a mean asymmetry value of 0.89 +/- 0.15, and on comparing it with the mean of the asymmetry indices of the posterior region (cerebellum), it showed a statistically significant difference (p < 0.05). CONCLUSION: Patients with ED frequently show hypoperfusion of the anteroinferior region of the temporal lobe, predominantly in the left hemisphere, in the acute phase of the illness.

[Potential sources of diagnostic pitfall and variants in FDG-PET/CT]. / Potenciales fuentes de error diagnóstico y variantes de la FDG-PET/TAC.

UNLABELLED: Oncological FDG PET show variants and findings that may lead to a diagnostic error and that may be clarified by the morfofunctional imaging from PET/CT. In this article we show the experience acquired since a Siemens PET/CT Biograph LSO Pico3D was applied in our centre. We describe some representative examples of FDG distribution patterns which may lead to erroneous interpretations of the clinical studies when they refer to specific clinical situations. The examples included are classified into two main groups according to the cause: Technical and biological, and the latter into physiological and non-physiological (pathophysiological). Patterns are described within the biological group showing changes of the FDG biodistribution that may reduce the uptake in tumoural lesions, the physiological variants that may be interpreted as pathology, the effects of previous treatment and uptakes related to benign diseases. CONCLUSION: We consider that knowledge of these variants and findings to be crucial in order to obtain optimal performance of PET/CT and to overcome the PET limitations.

[Bone scintigraphy in Erdheim-Chester disease]. / Gammagrafía ósea en la enfermedad de Erdheim-Chester.

Erdheim-Chester disease (ECD) is a rare disorder with fewer than 80 cases reported in the world. It consists of a non-Langerhans' cell histiocytosis that usually presents as pain due to bone involvement; however, the prognosis is marked by extraskeletal involvement. Although the final diagnosis needs an anatomophatologic study (normally through a bone biopsy), radiologic and scintigraphic findings are quasi pathognomonic. In this work, we report 2 ECD cases and their respective bone scans showing typical findings described in the literature. We found bilateral and symmetrical increased uptake of diaphyses and metaphyses of long bones, mainly in lower limbs. The mid-diaphyses and the epiphyses (partially in the first case) as well as the axial skeleton are spared.