State-of-the art imaging evaluation of brain tumors has extended beyond conventional contrast-enhanced MR imaging. Functional imaging assessment of brain tumor vascularity is important because there is a close association between angiogenesis and prognosis. MR perfusion imaging, including arterial spin labeling, T2∗-weighted dynamic susceptibility contrast (DSC), and T1-weighted dynamic contrast-enhanced methods, can provide the radiologist with quantitative imaging biomarkers for characterization of tumor vascularity that can be helpful to determine tumor grading, predict prognosis, and evaluate therapeutic efficacy. This is particularly crucial as current and future anticancer agents may target specific aspects of tumor biology that may not be reflected by assessment of simple size measurement on conventional MRI. Technical factors including methods of image acquisition, data post-processing, and interpretation are also discussed. Modern evaluation of brain tumors has extended beyond conventional contrast-enhanced MR imaging. Relying on the enhancing portion of a brain tumor alone can be problematic because it underestimates the actual tumor volume in high-grade gliomas, and low-grade gliomas often do not enhance to a significant degree (Earnest et al., Radiology 166:823-27, 1988). Incorporation of functional imaging techniques to complement the morphologic information provided by conventional MR imaging allows for a more comprehensive understanding of the complex biology of brain tumors. The development and validation of quantitative noninvasive imaging biomarkers are critical to improve diagnostic, predictive, and therapeutic efficacy evaluation of brain tumors. Functional imaging assessment of brain tumor vascularity is important because there is a close association between angiogenesis and prognosis (Gaa et al., 6:518-22, 1996). Among current advanced MR imaging techniques, MR perfusion imaging has the potential to provide the radiologist with quantitative imaging biomarkers of tumor vascularity and angiogenesis. Despite an abundance of studies, particularly those involving T2∗-weighted DSC MR imaging, demonstrating characterization of brain tumor perfusion parameters, these techniques have yet to be implemented in routine clinical practice. A brain tumor's angiogenic physiology lends itself to perfusion imaging, where measures of cerebral blood volume, flow, and permeability have been shown to characterize the behavior of various tumor types. Image acquisition and processing are discussed, as well as efforts to standardize these techniques. Although the role of MR perfusion in characterizing brain tumors is constantly evolving, this chapter defines its current applications and limitations. Finally, future directions and prospects are explored.
|Title of host publication||Functional Brain Tumor Imaging|
|Editors||Jay J. Pillai|
|Place of Publication||New York, NY|
|Number of pages||23|
|ISBN (Print)||1441958576, 9781441958570|
|Publication status||Published - 1 May 2014|