Akihiko Sakata

Beyond the flow: the evolving role of magnetic resonance imaging in arteriovenous shunt evaluation - Diagnostic and Interventional Radiology

Certain brain tumors exhibit cystic components. MRI is particularly effective in characterizing the location, enhancement, and morphology of these cystic regions, enabling radiologists to narrow the differential diagnosis. Cystic components are often associated with circumscribed tumors and may be linked to favorable outcomes. High-grade tumors such as glioblastoma can also occasionally exhibit cystic components. Here, we summarize the imaging characteristics of representative cystic brain intraparenchymal neoplasms, including hemangioblastoma, pilocytic astrocytoma, pleomorphic xanthoastrocytoma, ganglioglioma, desmoplastic infantile ganglioglioma/astrocytoma, central neurocytoma, dysembryoplastic neuroepithelial tumor, ependymoma, glioblastoma, and metastases. This review aims to provide MRI features that facilitate differentiation of these tumors and support appropriate clinical management.

A 28-year-old man presented with acute onset dysarthria and right facial droop. MRI revealed a horseshoe-shaped mass in the left frontal lobe, and tumefactive demyelinating lesion (TDL) was suspected. Despite steroid pulse therapy, follow-up imaging demonstrated lesion enlargement, raising concern for malignancy. ¹⁸ F-Fluciclovine ( ¹⁸ F-FACBC) PET/MRI showed moderate tracer accumulation. Surgical resection was performed, and the diagnosis of TDL was confirmed. This represents the first reported case of TDL evaluated with ¹⁸ F-Fluciclovine PET imaging. The discordance between moderate tracer uptake and rapid lesion growth may be useful for differentiating TDL from glioma.

Photon-counting detector computed tomography in thoracic oncology: revolutionizing tumor imaging through precision and detail - Diagnostic and Interventional Radiology

Recent advances in molecular genetics have revolutionized the classification of pediatric-type high-grade gliomas in the 2021 World Health Organization central nervous system tumor classification. This narrative review synthesizes current evidence on the following four tumor types: diffuse midline glioma, H3 K27-altered; diffuse hemispheric glioma, H3 G34-mutant; diffuse pediatric-type high-grade glioma, H3-wildtype and IDH-wildtype; and infant-type hemispheric glioma. We conducted a comprehensive literature search for articles published through January 2025. For each tumor type, we analyze characteristic clinical presentations, molecular alterations, conventional and advanced magnetic resonance imaging features, radiological-molecular correlations, and current therapeutic approaches. Emerging radiogenomic approaches utilizing artificial intelligence, including radiomics and deep learning, show promise in identifying imaging biomarkers that correlate with molecular features. This review highlights the importance of integrating radiological and molecular data for accurate diagnosis and treatment planning, while acknowledging limitations in current methodologies and the need for prospective validation in larger cohorts. Understanding these correlations is crucial for advancing personalized treatment strategies for these challenging tumors.

The fifth edition of the World Health Organization classification of central nervous system tumors represents a significant advancement in the molecular-genetic classification of pediatric-type diffuse gliomas. This article comprehensively summarizes the clinical, molecular, and radiological imaging features in pediatric-type low-grade gliomas (pLGGs), including MYB- or MYBL1-altered tumors, polymorphous low-grade neuroepithelial tumor of the young (PLNTY), and diffuse low-grade glioma, MAPK pathway-altered. Most pLGGs harbor alterations in the RAS/MAPK pathway, functioning as “one pathway disease”. Specific magnetic resonance imaging features, such as the T2-fluid-attenuated inversion recovery (FLAIR) mismatch sign in MYB- or MYBL1-altered tumors and the transmantle-like sign in PLNTYs, may serve as non-invasive biomarkers for underlying molecular alterations. Recent advances in radiogenomics have enabled the differentiation of BRAF fusion from BRAF V600E mutant tumors based on magnetic resonance imaging characteristics. Machine learning approaches have further enhanced our ability to predict molecular subtypes from imaging features. These radiology-molecular correlations offer potential clinical utility in treatment planning and prognostication, especially as targeted therapies against the MAPK pathway emerge. Continued research is needed to refine our understanding of genotype–phenotype correlations in less common molecular alterations and to validate these imaging biomarkers in larger cohorts.

Appropriate response assessment criteria are crucial for accurate evaluation of clinical trial outcomes, and numerous criteria have been proposed to address this need. With the introduction of Response Assessment in Neuro-Oncology (RANO) criteria version 2.0 (RANO 2.0) in 2023, response assessment in gliomas has evolved significantly, requiring both clinicians and radiologists to develop a comprehensive understanding of its modifications and implementation. This review first provides an overview of standard management and imaging schedule in glioma treatment. We then review the basic framework of RANO 2.0, inherited from previous response criteria, with particular emphasis on major modifications to this framework: the implementation of the Brain Tumor Imaging Protocol and the adoption of post-radiation scan as the baseline scan. Additionally, we analyze critical changes in response evaluation and interpretation, specifically focusing on the role of preliminary progressive disease assessment with confirmation scans, and the elimination of T2/FLAIR lesion measurements from enhancing tumor assessment. Through illustrative clinical cases, we demonstrate the practical application of these modifications and discuss the implementation of three distinct imaging-based categories: enhancing tumor, non-enhancing tumor, and tumors with both enhancing and non-enhancing components (in short, mixed tumor). This comprehensive narrative review provides clinicians with practical guidance for implementing RANO 2.0 in their clinical practice.