**6. Conclusion**

IMP-SPECT and statistical mapping are considered to be useful for the diagnosis of PCNSL. Multi-modal images should be taken before steroid therapy, because steroids affect the diagnostic performance of both of MRI and SPECT. Statistical mapping is useful for detecting small tumors which cannot be detected by usual IMP SPECT. However, some artifacts also exist in statistical mapping images. The careful interpretation of such image findings is essential. Anatomical standardized statistical mapping is thus considered a useful method for improving the diagnostic sensitivity, specificity and accuracy of IMP SPECT for brain lesions.
