Is Diffusion Tensor Imaging-Guided Radiotherapy the New State-of-the-Art? A Review of the Current Literature and Technical Insights

Despite the increasing precision of radiotherapy delivery, it is still frequently associated with neurological complications. This is in part due to damage to eloquent white matter (WM) tracts, which is made more likely by the fact they cannot be visualised on standard structural imaging. WM is additionally more vulnerable than grey matter to radiation damage. Primary brain malignancies also are known to spread along the WM. Diffusion tensor imaging (DTI) is the only in vivo method of delineating WM tracts. DTI is an imaging technique that models the direction of diffusion and therefore can infer the orientation of WM fibres. This review article evaluates the current evidence for using DTI to guide intracranial radiotherapy and whether it constitutes a new state-of-the-art technique. We provide a basic overview of DTI and its known applications in radiotherapy, which include using tractography to reduce the radiation dose to eloquent WM tracts and using DTI to detect or predict tumoural spread. We evaluate the evidence for DTI-guided radiotherapy in gliomas, metastatic disease, and benign conditions, finding that the strongest evidence is for its use in arteriovenous malformations. However, the evidence is weak in other conditions due to a lack of case-controlled trials.

Vascular Brain Disease in Geriatric Neuropsychiatry

Vascular brain diseases are a significant cause of dementia, and their presence, alone or associated with degenerative conditions, increases the risk of conversion to progressive cognitive decline. Neuropsychiatric manifestations vary according to the affected brain territory and disrupted neuronal circuits. In the current chapter, epidemiological prevalence, the harmonization of the diagnostic criteria of vascular subtypes, and the impact of age and socio-demographic aspects are critically reviewed. Another explored topic refers to the diagnostic and therapeutic approach. Structural imaging, including magnetic resonance (MRI) and computer tomography (CT), and a thorough neuropsychological and clinical exam, may help establish the differential diagnosis and substantially impact clinical evolution. Treatment involves various strategies, including controlling cardiovascular and metabolic risk factors, such as hypertension, atrial fibrillation, cardiopathies, and adopting a healthy lifestyle. Treatment relies on preventive and health promotion strategies related to the timely control of vascular risk factors and symptomatic approaches. The use of acetylcholinesterase inhibitors aims at stabilizing symptoms and is recommended in all stages of dementia.

Multimodality Anatomic and Molecular Imaging of Parkinson Disease and Atypical Parkinson Syndromes with MRI, Iodine 123 N-ω-Fluoropropyl-2β-Carbomethoxy-3β-(4-Iodophenyl) Nortropane SPECT (Dopamine Transporter SPECT), Iodine 123 Metaiodobenzylguanidine Cardiac Scintigraphy, and [18F] FDG-PET

Advances in molecular imaging techniques and the increasing availability of functional imaging are expanding the role of nuclear medicine in neuroradiology. Molecular imaging has a well-established role in the evaluation of extrapyramidal disorders. In this setting, functional assessment can be combined with structural imaging to make a more accurate diagnosis. This is particularly useful in a number of more clinically challenging pathologies. This review discusses the role and context of imaging in extrapyramidal disorders. Structural imaging with MR imaging in combination with iodine 123 N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) nortropane SPECT (dopamine transporter SPECT), iodine 123 metaiodobenzylguanidine cardiac scintigraphy, and [18F]FDG-PET can be used to differentiate various underlying disease processes including Parkinson disease, dementia with Lewy bodies, multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration.Learning Objective: To assess dopamine transporter studies qualitatively and semiquantitatively and categorize them as having normal, abnormal, or indeterminate findings and to understand the role of MR imaging, iodine 123 metaiodobenzylguanidine cardiac scintigraphy, and [18F] FDG-PET in advancing the differential diagnoses of patients with Parkinson disease and atypical parkinsonian syndrome

Privacy-preserving harmonization via distributed ComBat

Challenges in clinical data sharing and the need to protect data privacy have led to the development and popularization of methods that do not require directly transferring patient data. In neuroimaging, integration of data across multiple institutions also introduces unwanted biases driven by scanner differences. These scanner effects have been shown by several research groups to severely affect downstream analyses. To facilitate the need of removing scanner effects in a distributed data setting, we introduce distributed ComBat, an adaptation of a popular harmonization method for multivariate data that borrows information across features. We present our fast and simple distributed algorithm and show that it yields equivalent results using data from the Alzheimer's Disease Neuroimaging Initiative. Our method enables harmonization while ensuring maximal privacy protection, thus facilitating a broad range of downstream analyses in functional and structural imaging studies.