RESUMEN
Coronary CT angiography (CCTA) suffers from a reduced diagnostic accuracy in patients with heavily calcified coronary arteries or prior myocardial revascularisation due to artefacts caused by calcifications and stent material. CT myocardial perfusion imaging (CTMPI) yields high potential for the detection of myocardial ischemia and might help to overcome the above mentioned limitations. We analysed CT single-phase perfusion using high-pitch helical image acquisition technique in patients with prior myocardial revascularisation. Thirty-six patients with an indication for invasive coronary angiography (28 with coronary stents, 2 with coronary artery bypass grafts and 6 with both) were included in this prospective study at two study sites. All patients were examined on a 2nd generation dual-source CT system. Stress CT images were obtained using a prospectively ECG-triggered single-phase high-pitch helical image acquisition technique. During stress the tracer for myocardial perfusion (MP) SPECT imaging was administered. Rest CT images were acquired using prospectively ECG-triggered sequential CT. MP-SPECT imaging and invasive coronary angiography served as standard of reference. In this heavily diseased patient cohort CCTA alone showed a low overall diagnostic accuracy for detection of hemodynamically relevant coronary artery stenosis of only 31% on a per-patient base and 60% on a per-vessel base. Combining CCTA and CTMPI allowed for a significantly higher overall diagnostic accuracy of 78% on a per-patient base and 92% on a per-vessel base (p < 0.001). Mean radiation dose for stress CT scans was 0.9 mSv, mean radiation dose for rest CT scans was 5.0 mSv. In symptomatic patients with known coronary artery disease and prior myocardial revascularization combining CCTA and CTMPI showed significantly higher diagnostic accuracy in detection of hemodynamically significant coronary artery stenosis when compared to CCTA alone.
Asunto(s)
Técnicas de Imagen Sincronizada Cardíacas , Angiografía por Tomografía Computarizada , Angiografía Coronaria/métodos , Circulación Coronaria , Isquemia Miocárdica/diagnóstico por imagen , Imagen de Perfusión Miocárdica/métodos , Tomografía Computarizada de Emisión de Fotón Único , Tomografía Computarizada Espiral , Anciano , Anciano de 80 o más Años , Puente de Arteria Coronaria , Electrocardiografía , Femenino , Alemania , Hemodinámica , Humanos , Masculino , Persona de Mediana Edad , Isquemia Miocárdica/complicaciones , Isquemia Miocárdica/fisiopatología , Isquemia Miocárdica/terapia , Intervención Coronaria Percutánea/instrumentación , Valor Predictivo de las Pruebas , Estudios Prospectivos , Interpretación de Imagen Radiográfica Asistida por Computador , Reproducibilidad de los Resultados , StentsRESUMEN
Functional imaging methods such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) allow in vivo assessment of cerebral metabolism at rest and cerebral responses to cognitive stimuli. Activation studies with different cognitive tasks have deepened the understanding of underlying pathology leading to Alzheimer disease (AD) and how the brain reacts to and potentially compensates the imposed damage inflicted by this disease. The aim of this manuscript study was to summarize current findings of activation studies in healthy people at risk for AD, in people with mild cognitive impairment (MCI) as a possible progenitor of AD and finally in patients with manifest AD, adding recent results about impaired deactivation abilities and default mode function in AD. A new comprehensive model will be introduced integrating these heterogeneous findings and explaining their impact on cognitive performance.
Asunto(s)
Enfermedad de Alzheimer/diagnóstico , Enfermedad de Alzheimer/fisiopatología , Mapeo Encefálico/métodos , Encéfalo/fisiopatología , Diagnóstico por Imagen/métodos , Modelos Neurológicos , Red Nerviosa/fisiopatología , Simulación por Computador , HumanosAsunto(s)
Insomnio Familiar Fatal/patología , Tálamo/patología , Encéfalo/patología , Resultado Fatal , Femenino , Alemania , Humanos , Procesamiento de Imagen Asistido por Computador , Insomnio Familiar Fatal/genética , Insomnio Familiar Fatal/fisiopatología , Persona de Mediana Edad , Tomografía de Emisión de Positrones , Priones/genéticaRESUMEN
BACKGROUND: Successful cognitive performance depends not only on the activation of specific neuronal networks but also on selective suppression of task-irrelevant modalities, i.e., deactivation of non-required cerebral regions. This ability to suppress the activation of specific brain regions has, to our knowledge, never been systematically evaluated in patients with Alzheimer disease (AD). The aim of the current study was to evaluate both cerebral activation and deactivation in (1) healthy volunteers, (2) patients with mild cognitive impairment (MCI) who are at risk for AD, and (3) patients with moderate AD during active navigation, representing a cognitive task typically affected in AD. METHODS AND FINDINGS: Changes in regional cerebral blood flow (rCBF) were assessed with PET imaging during an active navigation task in a 3D virtual-reality environment. The task was based on visual cues exclusively; no auditory cues were provided. Age-matched groups of healthy individuals, patients with MCI, and patients with AD were examined. Specific differences in the activation patterns were observed in the three groups, with stronger activation of cerebellar portions and visual association cortex in controls and stronger activation of primary visual and frontal cortical areas in patients with MCI and AD. Highly significant bilateral decrease of rCBF in task-irrelevant auditory cortical regions was detected in healthy individuals during performance of the task. This rCBF decrease was interpreted as a cross-modal inhibitory effect. It was diminished in patients with MCI and completely absent in patients with AD. A regression analysis across all individuals revealed a clear positive relation between cognitive status (mini mental state examination score) and the extent of auditory cortical deactivation. CONCLUSION: During active navigation, a high level of movement automation and an involvement of higher-order cerebral association functions were observed in healthy controls. Conversely, in patients with MCI and AD, increased cognitive effort and attention towards movement planning, as well as stronger involvement of lower-order cerebral systems, was found. Successful cognitive performance in healthy individuals is associated with deactivation of task-irrelevant cerebral regions, whereas the development of AD appears to be characterized by a progressive impairment of cross-modal cerebral deactivation functions. These changes may cause the generally decreased ability of patients with AD to direct attention primarily to the relevant cognitive modality.