Erratum

Since publication of their article [1], the authors have become aware that there is an error in the description of the image data in the legend to Fig. 5. The second sentence of the legend should read as follows:

“The image data show radioactivity distribution in normal brain and cerebral metastases (enclosed in blue circle) (top panel) and are separated into blood (middle upper panel), non-blood (middle lower panel) and corresponding contrast-enhanced MRI images (bottom panel).”