Advanced Imaging Techniques for Radiotherapy Planning of Gliomas

Abstract

The accuracy of target delineation in radiation treatment (RT) planning of cerebral gliomas is crucial to achieve high tumor control, while minimizing treatment-related toxicity. Conventional magnetic resonance imaging (MRI), including contrast-enhanced T1-weighted and fluid-attenuated inversion recovery (FLAIR) sequences, represents the current standard imaging modality for target volume delineation of gliomas. However, conventional sequences have limited capability to discriminate treatment-related changes from viable tumors, owing to the low specificity of increased blood-brain barrier permeability and peritumoral edema. Advanced physiology-based MRI techniques, such as MR spectroscopy, diffusion MRI and perfusion MRI, have been developed for the biological characterization of gliomas and may circumvent these limitations, providing additional metabolic, structural, and hemodynamic information for treatment planning and monitoring. Radionuclide imaging techniques, such as positron emission tomography (PET) with amino acid radiopharmaceuticals, are also increasingly used in the workup of primary brain tumors, and their integration in RT planning is being evaluated in specialized centers. This review focuses on the basic principles and clinical results of advanced MRI and PET imaging techniques that have promise as a complement to RT planning of gliomas.

Fluorescence-Guided Surgery in the Surgical Treatment of Gliomas: Past, Present and Future

“…It appears that two types of invasion occur here: a fast and non-directional spread coupled with a slow but directional infiltration characterised by leading and following tumour cell populations [ 6 ]. It is due to the need to capture these outermost invading cells that the planning of radiotherapy usually has a planning target volume that is 0.3–0.5 cm beyond abnormal FLAIR areas on imaging [ 7 ].…”

Bombesin Receptor Family Activation and CNS/Neural Tumors: Review of Evidence Supporting Possible Role for Novel Targeted Therapy

“…Treatment involves primarily surgery, radiation, and chemotherapy, but for the glioblastomas, which are the majority, despite improvements in prognostic markers, there has been little improvement in survival (27,(130)(131)(132). Therefore, particularly in the case of glioblastomas, there is increased interest in newer approaches in treatment.…”

“…Therefore, particularly in the case of glioblastomas, there is increased interest in newer approaches in treatment. In other non-CNS tumors (as reviewed earlier) the ectopic expression/ overexpression of various peptide receptors is increasingly being applied and investigated for its possible diagnostic and therapeutic approaches for treatment of these tumors (10,73,124,125,(132)(133)(134)(135)(136). In the case of gliomas and particularly for glioblastomas, the over-/ectopic expression of the BnR family has been investigated in a number of studies and may provide new therapeutic approaches, as recently used in non-CNS tumors (prostate, colon, etc.)…”

“…While magnetic resonance imaging (MRI) remains the mainstay for initial and follow-up imaging of CNS/neural tumors and provides important information on tumor location, size, number of lesions, perifocal edema, and contrast enhancement, other aspects of tumor behavior are either not defined or incompletely defined, such as tumor heterogeneity, extent of metabolically active tissue, differentiating treatmentrelated changes from recurrent disease in previously treated patients, and extent of tumor invasion, in some cases (132,(239)(240)(241)(242). Because of these latter limitations, there is increased interest in the development of other imaging approaches, particularly the use of positron emission tomographic (PET) techniques including [ 18 F]Fluorodeoxyglucose (FDG) (132,235,239,243), as well as other nuclear medicine approaches (132,235,243,244).…”

“…In the case of gliomas and particularly for glioblastomas, the over-/ectopic expression of the BnR family has been investigated in a number of studies and may provide new therapeutic approaches, as recently used in non-CNS tumors (prostate, colon, etc.) ( 10 , 13 , 20 , 22 , 132 , 137 ) and will be reviewed in the following section.…”