====== Magnetic resonance imaging for intracranial metastases ======

Although magnetic resonance imaging (MRI) is more sensitive than [[computed tomography]] (CT) for detection of brain metastases, CT remains a vital tool for initial work-up and perioperative management. Advanced MRI techniques such as [[magnetic resonance spectroscopy]] (MRS), [[magnetic resonance perfusion imaging]] (MRP), [[diffusion weighted imaging]] (DWI), and [[diffusion tensor imaging]] (DTI) may also be utilized to help distinguish brain metastases from other pathologies, and also to monitor treatment response. Nuclear medicine studies including 18 [[fluorodeoxyglucose]] [[positron emission tomography]] ([[FDG-PET]]) and other molecular imaging may play a larger role in the future.

They usually appear as multiple lesions with nodular or annular [[enhancement]] and are surrounded by [[edema]]. They are hypervascularized and have no [[restriction]] of their [[diffusion coefficient]] in their necrotic area and contain [[lipid]]s on [[Proton magnetic resonance spectroscopic imaging]]. Metastases can be distinguished from primary tumors by the lack of malignant cell infiltration around the tumor
((Grand S, Pasteris C, Attye A, Le Bas JF, Krainik A. The different faces of
central nervous system metastases. Diagn Interv Imaging. 2014 Oct;95(10):917-31. 
doi: 10.1016/j.diii.2014.06.014. Review. PubMed PMID: 25023732.
)).

===== Magnetic resonance imaging =====

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Interpretable and easy to obtain [[MRI]] features may not be sufficient to predict directly the primary tumour entity of [[brain metastases]] (BMs) but seem to have the potential to aid differentiating high- and low-proliferative BMs, such as [[SCLC]] and [[NSCLC]]
((Kiyose M, Herrmann E, Roesler J, Zeiner PS, Steinbach JP, Forster MT, Plate KH, Czabanka M, Vogl TJ, Hattingen E, Mittelbronn M, Breuer S, Harter PN, Bernatz S. [[MR]] imaging profile and histopathological characteristics of tumour vasculature, [[cell density]] and proliferation rate define two distinct growth patterns of human [[brain metastases]] from [[lung cancer]]. Neuroradiology. 2022 Oct 3. doi: 10.1007/s00234-022-03060-2. Epub ahead of print. PMID: 36184635.)).

===== Sequences =====
The two most commonly used MRI [[sequence]]s for assessing brain metastases are contrast-enhanced [[T1]]-weighted (CET1W) and [[T2]]-weighted [[FLAIR]], which provide information about size, morphology and macroscopic structures. Newer MRI sequences have been developed to increase the conspicuity of enhancing metastases. More recently, advanced MRI techniques that have moved beyond anatomical imaging are available to characterize microstructures, cellularity, physiology, perfusion, and metabolism. Changes in these attributes may supersede perceivable macroscopic anatomic changes and can serve as potential biomarkers for monitoring treatment effect, recurrence, and disease progression
((Mehrabian H, Detsky J, Soliman H, Sahgal A, Stanisz GJ. Advanced Magnetic Resonance Imaging Techniques in Management of Brain Metastases. Front Oncol. 2019 Jun 4;9:440. doi: 10.3389/fonc.2019.00440. PMID: 31214496; PMCID: PMC6558019.)).

In some clinical protocols, diffusion weighted MRI—usually with three diffusion b-values of 0, 500, and 1,000 [s/mm2]—is also acquired in order to provide information about tumor cellularity through measurement of the [[apparent diffusion coefficient]] (ADC) 
((Geijer B, Holtås S. Diffusion-weighted imaging of brain metastases: their potential to be misinterpreted as focal ischaemic lesions. Neuroradiology. 2002 Jul;44(7):568-73. doi: 10.1007/s00234-002-0792-0. Epub 2002 May 29. PMID: 12136357.))
((Duygulu G, Ovali GY, Calli C, Kitis O, Yünten N, Akalin T, Islekel S. Intracerebral metastasis showing restricted diffusion: correlation with histopathologic findings. Eur J Radiol. 2010 Apr;74(1):117-20. doi: 10.1016/j.ejrad.2009.03.004. Epub 2009 Apr 9. PMID: 19359117.)).

===== Magnetic resonance imaging with contrast enhancement for intracranial metastases =====

[[Magnetic resonance imaging with contrast enhancement for intracranial metastases]].

===== Magnetic resonance imaging for intracranial metastases Multicenter Studies =====

[[Magnetic resonance imaging for intracranial metastases Multicenter Studies]].