Guidelines for Complications of Cancer Treatment Vol VIII Part B

involvement. several factors limit the radiologic assessmentof neurovascular structures:(1) Arteries and veins are small structures, placing greatdemands on imaging studies to depict the structures andtheir relationship to a tumor.(2) the vessels are often not parallel to the imaging plane(3) normal anatomic relationships are distorted by thepresence of a tumor mass.(4) It can be difficult or impossible to differentiate edemain the reactive zone surrounding a tumor and the tumoritself at imaging limiting the evaluation of theneurovascular structures present within that abnormaltissue.(5) Non-invasive cross-sectional imaging techniques suchas CT and MRI can demonstrate whether a tumor is closeto or in contact with a neurovascular structure, but usuallycannot differentiate mere contact, adherence or subtleinvasion. Gross encasement of a vessel can be diagnosedreliably only when a tumor mass clearly surrounds thevessel. Irregularity of vessel walls shown at angiographycan be due to tumor encasement or atherosclerosis.In the Radiology Diagnostic Oncology Group multiinstitutionalcollaborative trial 1 which compared CT and MRI in localstaging of malignant musculoskeletal neoplasms, the positivepredictive value of CT and MRI for neurovascular involvementby sarcomas in that study was only 6± 27%, with a negativepredictive value of 92±99%. Panicek et al 1 emphasise theimportance of excellent image quality and recommend largeimaging matrices and small field-of-view imaging focused onthe local tumor site along with appropriate MRI surface coils.For CT, they suggest that intravenous contrast materialdelivered by rapid bolus injection should be used to optimizethe delineation of vessels. Special CT or MRI angiographic144