# Positron Emission Tomography in Cerebral Amyloid Angiopathy: A Scoping Review
## 4 Discussion
Non-hemorrhagic manifestations of CAA, such as CAA-related inflammation or ARIA-like events, ARIA being an acronym for Amyloid-related Imaging Abnormalities, represent a relevant and emerging issue, making CAA the spontaneous model of a mostly iatrogenic phenomenon in immunotherapy trials for AD [10; 11; 12; 13; 14; 15]. The relevance of biomarkers and PET imaging in these patients is high, and ongoing registries will provide data on large and homogeneous cohorts. Collectively, these studies underscore the importance of advanced imaging modalities in diagnosing CAA-ri. MRI findings, such as white matter hyperintensities, cortical swelling, and leptomeningeal enhancement, along with microbleeds, are characteristic of CAA-ri. Amyloid PET imaging further aids in identifying amyloid deposition, supporting the diagnosis. FDG-PET can provide additional information regarding metabolic activity in affected brain regions. Early recognition of these imaging features is crucial for prompt diagnosis and treatment of CAA-ri, potentially leading to better clinical outcomes. Future research should focus on longitudinal imaging studies to monitor disease progression and response to therapy, as well as exploring the underlying mechanisms driving inflammation in CAA. Amyloid PET imaging is also a relevant issue in patients with hereditary CAA, but studies addressing this issue are scarce. This could be due to the fact that the diagnosis is mainly obtained, in symptomatic and in pre-symptomatic cases, through genetic testing. The subtypes of hereditary CAA that have been tested are those due to APP mutations [48], those due to ATTR mutations [44, 45], and Dutch-Type Hereditary CAA [46, 47]. Cortical superficial siderosis, WMH, and cerebral microbleeds are consistent across hereditary CAA subtypes. However, APP duplication cases have demonstrated more extensive parenchymal amyloid deposition. PiB PET is a valuable tool for assessing amyloid pathology, with elevated uptake consistently correlating with disease severity. Studies underscore the heterogeneity of hereditary CAA, with distinct imaging and pathological profiles for Dutch-type and APP duplication subtypes. PET imaging serves as a vital adjunct to MRI in diagnosing and monitoring disease progression. Future research should explore targeted interventions and the prognostic implications of these findings. Despite its utility, amyloid PET imaging faces several limitations. Current tracers, such as [18F]Iforbetapir, [18F]Iforbetaben, and [11C]PiB, have high sensitivity for amyloid-beta, but lack specificity for vascular amyloid deposits. This limitation complicates the distinction between CAA and other conditions with amyloid pathology. Furthermore, variability in imaging protocols and analysis methods across studies contributes to inconsistent findings. Future research should focus on developing advanced PET tracers with higher specificity to vascular amyloids. Emerging tracers targeting amyloid-beta in vascular walls could significantly enhance the diagnostic accuracy of CAA. Additionally, integrating amyloid PET with multi-modal imaging approaches, such as tau PET and advanced MRI techniques, may provide a more comprehensive assessment of amyloid-related pathology. Standardization of imaging protocols and analysis techniques is another critical area for improvement. Consistent methodologies across studies will reduce variability and allow for more reliable comparisons of findings.