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It is often difficult to distinguish infectious disease of the central nervous system from a wide variety of non-infectious diseases, as neurosurgeons have few opportunities to treat them. Differentiation of infectious diseases from neoplastic diseases is often challenging. Since it often takes time to eliminate infectious diseases, it is necessary to utilize all the obtained medical information to make a proper diagnosis to avoid missing the appropriate chance of surgical treatment. In this paper, we describe tips for and pitfalls of accurately distinguishing such diseases, including brain abscess versus glioblastoma, meningitis versus dural lesions, and infection versus lymphoproliferative disorders in immunocompromised patients. In these cases, it is difficult to make a decision based only on the examination and imaging findings on admission, and it is important to make a diagnosis based on medical history and patient background.

The recent development in magnetic resonance(MR)hardware and techniques allows the acquisition of functional information, such as perfusion or metabolism, in addition to conventional anatomical information in of cancers.In this review article, various molecular imaging methods based on MR are introduced and their application and usefulness for diagnosis of cancer are discussed.Diffusion weighted image (DWI) is believed to correlate cell density and reflect malignancy of tumor. DWI has been widely used for the diagnosis and evaluation of responses to cancer treatment.Arterial spin labeling (ASL) allows acquisition of perfusion data without the use of any contrast agent and is expected to be an alternative or complementary method to dynamic contrast enhanced MR imaging.Amide proton transfer (APT) imaging reflects the amount of mobile peptide and proteins in cancer tissue, and could be a useful tool for assessing tumor malignancy or evaluating treatment responses.More specific measurement of cancer metabolites is available at the cost of spatial resolution by MR spectroscopy (MRS). Finally, the positron emission tomography (PET)/MR hybrid system enables simultaneous acquisition of functional/ anatomical information from MR imaging and molecular/metabolic information from PET imaging.Combining various molecular MR imaging methods with PET tracers may have a huge potential for clinical diagnosis of cancer.