Brain MRI: Tumor evaluation

Abstract

The designation "brain tumors" is commonly applied to a wide variety of intracranial mass lesions that are distinct in their location, biology, treatment, and prognosis. Since many of these lesions do not arise from brain parenchyma, the more appropriate term would be "intracranial tumors." The term "tumor" is used to include both neoplastic and non-neoplastic mass lesions, and should be considered in its broadest sense to simply indicate a space-occupying mass. This review describes an imaging-based approach for evaluating intracranial tumors. Conventional MRI is discussed in the setting of a regional classification system. This system provides a framework for analysis, and imaging clues can then be applied to narrow the differential possibilities. Emphasis is placed on advanced MRI techniques and their utility for deciphering common diagnostic problems.

Functional MRI tools in oncology

“…L'imagerie pondé ré e en diffusion, si elle est ré alisé e avec un jeu d'orientations successives du gradient de sensibilisation, peut ê tre utilisé e pour tracer les faisceaux de fibres nerveuses et ainsi repé rer les voies de conduction intracé ré brales avant une intervention neurochirurgicale [12].…”

“…La SRM peut ê tre utilisé e en oncologie à dé terminer un index de malignité local, important pour la caracté risation des tumeurs cé ré brales [12]. Le rapport citrate/ choline est significativement plus bas dans le cancer prostatique, en comparaison de la glande normale et de l'hypertrophie bé nigne [8].…”

A low cost approach for brain tumor segmentation based on intensity modeling and 3D Random Walker

“…Intravenous contrast agents augment lesion conspicuity and reveal enhancement characteristics that can help improve specificity [5]. In T1ce, blood vessels and part of the tumoral tissue where the contrast agent (gadolinium) passed the blood-brain barrier, are observed as hyperintense regions, while necrotic tissue is observed as hypointense since there is no blood flow into this area.…”

“…FLAIR, on the other hand, highlights mostly tissue with increased water content, such as edema [6]. Additionally, several advanced imaging techniques have been used to provide complementary information about tumoral or edematous tissue, such as Perfusion Imaging, Diffusion Imaging, or Spectroscopic Imaging [5]. However, such imaging techniques have inherently low signal-to-noise ratio compared to conventional MR modalities and, in addition, such acquisitions are not performed in clinical routine, especially during regular followup.…”

Classification of Malignant and Benign Tumors

“…However, this situation has been more challenging in cases of head and neck cancer, where luckily the combination with positron emission tomography (PET) has overcome shortages of CT and revolutionized the management of this cancer [2]. On the other hand, magnetic resonance imaging (MRI), which is more financially expensive but with better soft tissue discrimination and sparing from exposure to ionizing radiation, has risen in recent years in the diagnosis of difficult cases such as prostate [3], brain [4,5], and breast cancers [6].…”