The Role of MRI and PET/SPECT in Alzheimers Disease

Abstract

Alzheimer's disease (AD) is difficult to diagnose in its early stages, and even if detected early, there is no preventative treatment. Imaging modalities such as MRI, PET, and SPECT have the potential to contribute to both the diagnosis of Alzheimer's disease, as well as assist in the search for more effective treatments. A number of AD-related biomarkers have been proposed and evaluated. The use of PET imaging to detect alterations in regional brain metabolism using [(18)F]FDG has enabled more sensitive and accurate early diagnosis of AD, especially in conjunction with traditional medical evaluation. Additionally, magnetic resonance imaging and spectroscopy provide a wide range of biomarkers that have been shown to correlate with the progression of AD. Some of these markers have been pursued in clinical trials. Progress has been made toward the evaluation of other more AD-specific biomarkers. However, many questions remain concerning the validity and sensitivity of these imaging biomarkers to aid in the assessment of potential new treatments, especially those related to increased levels of amyloid peptides in the brain.

Role of Myo-Inositol by Magnetic Resonance Spectroscopy in Early Diagnosis of Alzheimer’s Disease in APP/PS1 Transgenic Mice

“…For example, Behar et al [24] believe that the rise in mIns corresponds to the most marked astrocytic reaction and might reflect a specific glial response in hamsters with Creutzfeldt-Jakob disease. Coimbra et al's studies have shown a correlation of increased mIns with AD pathology [25] . In the present study, the results of GFAP staining showed that there were activated and hyperplastic astrocytes in the frontal cortex and hippocampus of 3-month-old AD mice, while no A ␤ plaques were detected and neurons were also not abnormally damaged.…”

MRI in Dementia

“…[17][18][19] Atrophy rates have been reported to be larger in entorhinal cortex than in the hippocampus (w7% per year versus w6% per year), 20 but difficulties in unambiguously defining this brain structure on the basis of landmarks make entorhinal cortex measurements highly variable. 21 In general, manual regions-of-interest measurements are both operator-dependent and labor-intensive.…”

“…21 Diffusion-Weighted Imaging and Diffusion-Tensor Imaging Several studies have used the apparent diffusion coefficient or diffusion characteristics derived from DTI to gain information on demyelinization and axonal loss in the context of Alzheimer's disease. The apparent diffusion coefficient provides information on the overall mobility of tissue water while DTI provides additional directional information on this diffusion process.…”

“…34 Albeit not yet validated to the extent of structural MRI, both diffusion-weighted imaging and DTI appear as promising candidates with potential to support an imaging diagnosis of Alzheimer's disease. 21 A strong correlation between apparent diffusion coefficient and Mini-Mental State Examination scores underlines a possible role for clinical use. 32 However, some technical issues still must be resolved regarding the optimum diffusion time and the optimal strength of the diffusion gradients (b values).…”

Visual Rating and ROI-Based Parametric Analysis of rCBF SPECT in Patients with Mild or Questionable Dementia: A Comparative Study

“…Measurement of regional cerebral blood flow (rCBF) using single-photon emission computer tomography (SPECT) or positron-emission tomography (PET) may be applied as supplemental investigations in patients with cognitive symptoms. Results from these methods will typically demonstrate regionally reduced blood flow or glucose metabolism in AD [4] , and several reports have suggested that focally reduced blood flow or metabolism can be present very early in the cause of the disease, which may increase the diagnostic certainty in AD [4][5][6][7][8][9] . Advanced methods for parametric image analysis and statistical parametric mapping have been available for some years.…”