| Gliomas are the most common primary neoplasms of the central nervous system. Magnetic resonance imaging (MRI) is a well-established noninvasive tool for evaluation of brain tumors because of its exellent tissue contrast and the availability of multi-planar imaging. Moreover, the use of Gd-DTPA improves the depiction and detection of brain tumors. However, conventional postcontrast MR images do not provide information about tumorous vascular beds of the brain, because increase in signal intensity reflects accumulation of Gd-DTPA in the interstitium. Therefore, X-ray angiography (or DSA) is still necessary in patients in whom information about tumor vascularity is essential for diagnosis, although this method is rather invasive. In adition, MR imaging has not yet resolved clinical issued that affect the management of brain tumors, including defferentiation between low-grade and high grade gliomas or between radiation necrosis and tumor recurrence. On the other hand, other noninvasive methods such as positron emission tomography (PET) and single photon emission computed tomography (SPECT) have had a substantial effect on diagnosis and treatment in patients with brain neoplasms because they enable distinction between radiation necrosis and tumor regrowth in spite of the poorer spatial resolusion. PET is not the routine imaging method for gliomas because of its expensive examinationcharge.Recently, echo planar imaging (EPI) and dynamic susceptibility contrast MR imaging have been developed to obtain functional images of relative cerebral blood volume (CBV). On images obtained with this method, MR signal intensity is transiently reduced by susceptibility effects during the first pass of paramagnetic agent through the vasculature. This technique has been used to provide a dynamic assessment of tumor vascular beds and thereby suggests the potential to offer useful additional information. CBV maps caculated from MR images are particularly sensitive for depicting the microvasculature and can enable the detection of neovascularization at the capillary level, as well as its quantification in relative terms. It is known that malignant tumors depend on neovascularization for their growth and metastasis. It has also been suggested that the degree of tumor angionenesis is related to clinical outcome, suggesting that angiogenic properties correlate with tumor aggressiveness. Microvessel density (MVD) is an independent prognostic indicator in patients with malignant neoplasms. Many studies have shown that the secretion and activation of various endothelial growth factors, called angiogenic factors, by tumor cells play crucial roles in the formation of neovasculature, However, there have been few studies on the association of the expression of angiogenic factors (such as VEGF) or MVD and the tumors rCBV values. In this study, 46 cases with supratentorial gliomas underwent MR perfusion weighted imaging. All the cases were proved by operation and pathology. Tumor's samples were examined immunohistochemically to investigate the correlation between the expression of vascular endothelial growth factor (VEGF),microvessel density (MVD) and tumor's maxiumrCBV. The association between tumor grade and maxium rCBV was also invesgated. Material and methodOur study group consisted of 46 patients (31 male patients, 15 female patients) with supratentorial gliomas. Patient ages ranged from 17 to 68 years (mean age, 38±8.87 years). No one received any treatment (such as operation, radiation or chemical treatment). After MR examination, all patients received surgical operation treatment within 1 to 5 days.MR imaging was performed on a 1.5T imager (GE signa CV/i) with a maxium gradient volume of 40 mT/m and a slew rate of 150T/m/s. The procedures of MR examination were plain MR scan, perfusion weighted imaging, and routine contrast-enhanced MR scan. The pulse sequence of PWI was single shot gradient-recalled echo-echo planar imaging T2*-weighted imaging (SS-GRE-EPI-T2*WI) during the first pass of Gd-DTPA through...
|
PDF Full Text Request