Imaging of CNS tumors

Full text: Brain tumors represent approximately 2% of all tumors with incident rates of 6-7% per 100,000 of population in Europe and peak at 75-80 years of age. In childhood, primary brain tumors account up to 25 % of all tumors diagnosed by the age of 15. Of all primary brain tumors gliomas are the most common tumors accounting for 49% and ∼2% of all new cases of cancer. Neuroradiology is essential tumor diagnostic discipline and plays a major role in the detection of the tumor, its extent, its spread and in the tumor follow-up. Computer tomography (CT) and especially magnetic resonance imaging (MRI), with its basic and advance techniques, are the most important neuroradiology techniques in a daily use. They help us to detect the tumor, its exact location, anatomical relationships with surrounding structures, tissue density differences (CT) and differences in signal intensity between normal and abnormal brain tissue in tumors (MR). With the intravenous administration of contrast agent we are able to demonstrate vascularity of the tumor or breakdown of the blood-brain barrier. CT is generally the first choice when the brain tumor is suspected, mostly due to the availability of CT units in most community hospitals. The new generation of MDCT enables us to complete examination in a very short time, within seconds. It allows us to analyze not only the brain tissue, but osseous structures as well. Improved temporal resolution enables CT angiography and perfusions studies. The major disadvantages of CT are the high radiation dose, limited contrast resolution of brain tissue and possible nephrotoxic effects. MR imaging with conventional sequences and advanced MR techniques (MR spectroscopy, MR perfusion, DWI, DTI) have major importance in diagnoses and evaluations of brain tumors. The excellent differentiation between white and grey matter and the multiplanar capabilities of MR allows us to analyze the brain tumors in details and to come as close as possible to histological nature of tumor. It is noninvasive and has a great spatial resolution. The major drawback of MRI is that the procedure itself can be time consuming, especially when many sequences are used in a row. Both techniques can be used for planning surgical or irradiation treatments of brain tumors with stereotactic procedures