HGGs can be modeled as containing distinct anatomical compartments: a central or bulk portion of tumor, which often contains a zone of central necrosis surrounded by regions of solid tumor, and a surrounding zone of infiltrating tumor with isolated migratory tumor cells. These compartments roughly correspond to areas of decreased signal on T1 images (necrosis), gadolinium enhancement (central or bulk tumor) and increased edema-associated T2 signal (infiltrative tumor cells) on MR images (Fig. 10.2). The central regions contribute to mass effect, generally take up intravenous contrast agents, and contain areas of both active metabolism and hypoxic zones that contribute to treatment resistance. The uptake of contrast agents indicates a disruption of the normal blood-brain barrier (BBB) in this tumor region, which is essential for the delivery of effective doses of most systemic chemotherapeutic agents. Although HGG is a diffuse disease process (see discussion below), approximately 80% of HGG tumor recurrences are detected within 2-3 cm of the original resection cavity [5, 6], and only with intense local therapy such as high-activity radiation implants have significant percentages of recurrences been reported outside this zone (45% in one study). Adding to these local problems of tumor control for HGGs is a poorly defined zone that encompasses bulk
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The term vaginitis is one that is applied to any inflammation or infection of the vagina, and there are many different conditions that are categorized together under this ‘broad’ heading, including bacterial vaginosis, trichomoniasis and non-infectious vaginitis.