Background Arterial spin labeling (ASL) is a magnetic resonance imaging (MRI)-based technique using labeled blood-water of the brain-feeding arteries as an endogenous tracer to derive information about brain perfusion. It enables the assessment of cerebral blood flow (CBF). Method This review aims to provide a methodological and technical overview of ASL techniques, and to give examples of clinical use cases for various diseases affecting the central nervous system (CNS). There is a special focus on recent developments including super-selective ASL (ssASL) and time-resolved ASL-based magnetic resonance angiography (MRA) and on diseases commonly not leading to characteristic alterations on conventional structural MRI (e. g., concussion or migraine). Results ASL-derived CBF may represent a clinically relevant parameter in various pathologies such as cerebrovascular diseases, neoplasms, or neurodegenerative diseases. Furthermore, ASL has also been used to investigate CBF in mild traumatic brain injury or migraine, potentially leading to the establishment of imaging-based biomarkers. Recent advances made possible the acquisition of ssASL by selective labeling of single brain-feeding arteries, enabling spatial perfusion territory mapping dependent on blood flow of a specific preselected artery. Furthermore, ASL-based MRA has been introduced, providing time-resolved delineation of single intracranial vessels. Conclusion Perfusion imaging by ASL has shown promise in various diseases of the CNS. Given that ASL does not require intravenous administration of a gadolinium-based contrast agent, it may be of particular interest for investigations in pediatric cohorts, patients with impaired kidney function, patients with relevant allergies, or patients that undergo serial MRI for clinical indications such as disease monitoring. Key Points:

Background. With fast-growing evidence in literature for clinical applications of chemical exchange saturation transfer (CEST) magnetic resonance imaging (MRI), this prospective study aimed at applying amide proton transfer-weighted (APTw) CEST imaging in a clinical setting to assess its diagnostic potential in differentiation of intracranial tumors at 3 tesla (T). Methods. Using the asymmetry magnetization transfer ratio (MTRasym) analysis, CEST signals were quantitatively investigated in the tumor areas and in a similar sized region of the normal-appearing white matter (NAWM) on the contralateral hemisphere of 27 patients with intracranial tumors. Area under curve (AUC) analyses were used and results were compared to perfusion-weighted imaging (PWI). Results. Using APTw CEST, contrast-enhancing tumor areas showed significantly higher APTw CEST metrics than contralateral NAWM (AUC = 0.82; p < 0.01). In subgroup analyses of each tumor entity vs. NAWM, statistically significant effects were yielded for glioblastomas (AUC = 0.96; p < 0.01) and for meningiomas (AUC = 1.0; p < 0.01) but not for lymphomas as well as metastases (p > 0.05). PWI showed results comparable to APTw CEST in glioblastoma (p < 0.01). Conclusions. This prospective study confirmed the high diagnostic potential of APTw CEST imaging in a routine clinical setting to differentiate brain tumors.

Introduction: Cranial nonenhanced CT (NECT) imaging in hyperacute ischemic stroke is rarely used for assessing arterial obstruction of middle cerebral artery by identifying hyperdense artery sign (HAS). Considering, however, its growing importance due to its impact on the decision-making process of thrombolysis with or without mechanical thrombectomy improved sensitivity to HAS is necessary, particularly in the group of less experienced clinicians being frequently the first one assessing the presence of HAS on NECT. Objective: The present study aimed to investigate the effect of different NECT image reconstructions on the correct detection of hyperdense middle cerebral artery sign in a cohort of observers with lower experience level on NECT. Particularly, MIP image reconstructions were expected to be useful for less experienced observers due to both strengthening of the hyperdensity of HAS and streamlining to less image slices. Methods: Twenty-five of 100 patients’ NECT image data presented with HAS. Sixteen observers with lower practice level on NECT (10 radiologists and 6 neurologists) evaluated independently the 3 image reconstructions of each data set with thin slice 1.5 mm, thick slab 5 mm, and 6-mm maximum intensity projection (MIP) and rated the presence of HAS in middle cerebral artery. A GEE model with random observer effect was used to examine the influence of the 3 image reconstructions on sensitivity to HAS. A linear mixed effects regression model was used to investigate the ranking of detectability of HAS. Interrater reliability was determined by Fleiss’ kappa coefficient (κ). Results: Recognition of HAS and sensitivity to HAS significantly differed between the 3 image reconstructions (p = 0.0106). MIP and thin slice reconstructions yielded each on average the highest sensitivities with 73% compared to thick slab reconstruction with 45% sensitivity. The interobserver reliability was fair (κ, 0.3–0.4). Detectability of HAS was significantly easier and better visible ranked on MIP and thin slice reconstructions compared to thick slab (p < 0.05). Conclusion: MIP and thin slice reconstructions increased the sensitivity to HAS (73%), whereas thick slab reconstructions seemed to be less appropriate (45%).

BACKGROUND AND PURPOSE: After endovascular treatment of intracranial aneurysms with the Woven EndoBridge (WEB) device, worsening of aneurysm occlusion or re-opening was reported to be possibly associated with WEB shape modification. This study analyzed quantitatively the WEB shape modification with time in association with anatomic results. MATERIALS AND METHODS: Thirty patients with 32 WEB-treated intracranial aneurysms fulfilled the inclusion criteria of cranial CT at baseline (day of intervention) and a follow-up CT at least >1 months’ later (median follow-up time, 11.4 months; interquartile range, 6.5–21.5 months). Adequate occlusion was observed in 84.4%, and aneurysm remnant, in 15.6%. WEB shape modification was quantified by a semiautomated approach on CT scans. Time courses were evaluated graphically and analytically; association analyses were performed by linear mixed-effects regression models. RESULTS: In 29/32 WEB devices (90.6%), the reduction in height was found to be at least 5%. The decrease in height with time was significantly associated with the time interval in days since the intervention (P < .0001): A stronger decrease in WEB height was associated with a longer time since the intervention (median reduction in 1 year, 19.2%; range, 8.6%–52.3%). No significant association was found with the quality of aneurysm occlusion, device size, rupture status of the aneurysm, aneurysm location, and reintervention rate. CONCLUSIONS: Shape modification was common in WEB-treated intracranial aneurysms with a median height reduction of 19.2% in 1 year. The quality of aneurysm occlusion was not associated with WEB modification.

Background/Objectives: Pituitary tumors account for over 90% of all sellar region masses. However, a spectrum of rare neoplastic, inflammatory, infectious, and vascular lesions—benign and malignant—can arise in the intra- and parasellar compartments and clinically and radiologically mimic PitNETs. We report a cohort of 47 such rare and cystic midline intracranial lesions, emphasizing their distinctive morphological, clinical, and imaging features and the personalized treatment strategies applied. Methods: In this retrospective single-center study, we reviewed all patients treated for suspected PitNETs via transsphenoidal approach between 2015 and 2024. Of 529 surgical cases, we excluded confirmed PitNETs, meningiomas, and classical intradural craniopharyngiomas. Collected data encompassed patient demographics, tumor characteristics, presenting symptoms, extent of resection or medical therapy, endocrine outcomes, and follow-up information. Results: Among all 529 patients who underwent surgical treatment for sellar lesions from 2015 to 2024, 47 cases (8.9%) were identified as rare or cystic masses. Forty-six underwent transsphenoidal resection; one patient with hypophysitis received corticosteroid therapy alone. Presenting symptoms included headache (n = 16), dizziness (n = 5), oculomotor disturbances (n = 2), and visual impairment (n = 17). Endocrine dysfunction was found in 30 patients, 27 of whom required hydrocortisone replacement. Histopathological diagnoses were led by colloid cysts (n = 14) and Rathke’s cleft cysts (n = 11). The remaining 22 cases comprised plasmacytoma, germinoma, lymphoma, pituicytoma, inverted papilloma, metastatic carcinoma, chordoma, nasopharyngeal carcinoma, chloroma, and other rare entities. Preoperative imaging diagnosis proved incorrect in 38% (18/47) of cases, with several lesions initially misidentified as PitNETs. Conclusions: Nearly 9% of presumed PitNETs were rare, often benign or inflammatory lesions requiring distinct management. Most could be safely resected and demonstrated excellent long-term outcomes. Yet, despite advanced imaging techniques, accurate preoperative differentiation remains challenging, with over one-third misdiagnosed. Clinical red flags—such as early hormone deficits, rapid progression or atypical imaging findings—should prompt early interdisciplinary evaluation and, when indicated, image-guided biopsy to avoid unnecessary surgery and ensure tailored therapy.