Alzheimer's DiseaseNeurology Solutions for more diagnostic confidence

There are a variety of types of dementia and cognitive impairment, which can have various underlying causes, ranging from Alzheimer’s disease (AD) to vascular dementia to name but a few, requiring different therapeutical approaches. Hence various risk factors need to be assessed. While imaging and laboratory tests have traditionally been used independently on a diagnostic basis to rule out other causes of dementia, they may in the future help to assess multiple different aspects of AD pathology and have immediate prognostic importance. Siemens provides technology and laboratory equipment to help effectively differentiate AD from other dementias and venture forward in AD research.

In patients with suspected AD, the clinical evaluation essentially includes lab tests for a number of mimicking diseases such as hypo- and hyperthyroidism, vitamin deficiencies, and infections of the central nervous system (Creutzfeldt-Jakob disease, AIDS dementia, neurosyphilis). As your partner in thyroid testing, Siemens solutions help labs keep pace with the evolving standards in thyroid disease diagnostics.

The simultaneous acquisition of MR imaging (MRI)/ CT imaging and positron emission tomography (PET) data provides exceptional insights into brain anatomy, functions, and metabolism. Biograph mMR and Biograph mCT/Biograph mCT Flow have the ability to precisely visualize areas of decreased or increased glucose metabolism in the brain. This supports differentiation between AD, frontoemporal dementia and other dementias. It also allows a determination of the extent and progression of the disease. In AD, a characteristic pattern of decreased uptake can be seen in the posterior temporo parietal association cortex.² PET imaging is utilized to estimate beta-amyloid neuritic plaque density in adult patients with cognitive impairment who are being evaluated for AD and other causes of cognitive decline.³ Through the combination of CT or MR with PET in one modality, Siemens technology enables shorter acquisition times and optimizes accuracy with motion compensation in agitated patients. Siemens’ exceptional molecular PET/MR and PET/CT technology promises unprecedented insights into AD pathology, more comprehensive brain imaging, and improved functional analysis.

By the time a typical Alzheimer’s disease (AD) patient comes to diagnosis, atrophy is normally well established. Even in patients with mild clinical symptoms, entorhinal volumes are already reduced by around 20–30 % and hippocampal volumes by about 15–25 %.⁴ In particular, the assessment of medial temporal atrophy with MRI has been shown to have a predictive value for AD. Consequently, medial temporal lobe atrophy is now included as one of the biomarkers of AD in proposed criteria for diagnosing (prodromal) AD at a pre-dementia stage.

The benefits of single modality MR and PET in the study of neurological diseases such as AD are well known. Combining these modalities brings the potential for a more complete imaging picture and better understanding of AD pathologies. In addition, the current research and development of new tracers offers great promise. Biograph mMR fully integrates state-of-the-art 3T MRI and cutting-edge molecular imaging. Simultaneous acquisition of the morphology, function, and metabolism of the brain are now possible. You can obtain a comprehensive diagnostic picture with just one scan, which shows MR and PET data in virtually seamless spatial alignment. In addition, the MR acquisition can be used to correct motion-related effects in PET, greatly improving image quality. 

Functional MRI (fMRI) is being increasingly used to investigate the functional integrity of brain networks in AD. In combination with other tests, the information gained from fMRI will help differentiate the diseases and determine the status of progression. Synaptic activity is measured either by the visualization of glucose metabolism of brain cells using PET or the visualization of signal changes due to changes in blood volume, blood flow, and the blood oxyhemoglobin/ deoxyhemoglobin ratio using BOLD MRI. Many fMRI studies in MCI and AD focus on the pattern of fMRI activation in the hippocampus and related structures in the medial temporal lobe. In patients with clinically diagnosed AD, the results have been quite consistent, showing decreased hippocampal activity during theencoding of new information. Furthermore, several studies report increased prefrontal cortical activity in AD patients. These results suggest that other networks may increase activity as an attempted compensatory mechanism during hippocampal failure.⁴ Other MRI techniques such as diffusion tensor imaging (DTI), arterial spin labeling measures of cerebral blood flow and PET tracers targeted at the cholinergic system, microglial activation and other tracers in development will also be contributing to our understanding of AD pathology in the future.

• Multiple parameters can be derived from the diffusion tensor, including the trace, ADC (Apparent Diffusion Coefficient), relative anisotropy, and fractional anisotropy. These secondary parameters are independent of the frame of reference and are very sensitive to white matter pathology.
• syngo DTI (Diffusion Tensor Imaging) Tractography uses diffusion tensor data and allows 3D visualization of specific white matter tracts.
• syngo DTI and syngo DTI Evaluation will help you to identify anatomical substructures, and with fiber direction maps and fiber tracts (tractography) you will be able to assess the microstructural aspects of the brain lesions.
• The Siemens Multidirectional DTI with 256 directions allows a finer and more precise visualisation of fiber tracks and direction.

The available genetic evidence strongly suggests a derangement in amyloid metabolism as the primary instigating factor in Alzheimer’s disease (AD). Interestingly, the autopsy findings in cognitively normal individuals support this speculation. Approximately 30% of cognitively normal elderly subjects have AD pathologic features at autopsy – mostly neocortical diffuse amyloid plaques but not extensive neocortical neurofibrillary tangles.⁵ These observations support the position that amyloid develops first, while neocortical neurofibrillary tangles appear later. Amyloid deposition is estimated to begin about 15 years before the onset of clinical symptoms. Thus, visualizing these neuritic plaques can support the clinical evaluation of AD. With the regulatory approval of PET amyloid tracers in many countries throughout the world, physicians can utilize PET imaging to estimate Amyloid-neuritic plaque density in adult patients with cognitive impairment who are being evaluated for AD and other causes of cognitive decline.

Biograph mMR fully integrates state-of-the-art 3T MRI and cutting-edge molecular imaging. Simultaneous acquisition of the morphology, function, and metabolism of the brain are now possible. You can obtain a comprehensive diagnostic picture with just one scan which shows MR and PET data in virtually seamless spatial alignment. In addition, the MR acquisition can be used to correct motion-related effects in PET, greatly improving image quality.