Many brain disorders do not show visible lesions and most likely are resulted from abnormalities in regional brain activity or connectivity. Conventional diagnostic neuroimaging techniques are not capable of precisely localizing the abnormal brain activity, but the recently developed integrated PET/MR technology may have the potential to bridge this gap. Integrated PET/MR has been used in clinical practice. However, its primary application is still a combination of functional PET imaging and structural MRI. Simultaneous PET/fMRI, a " functional+ functional" imaging technique, holds the advantages of high spatial and temporal resolution, high sensitivity and specificity, and non-invasiveness. Globally, simultaneous PET/fMRI research is still in its beginning stage, and a few initial PET/fMRI studies have shown that voxel-wise correlation between PET and fMRI metrics was not very high, indicating that they may reflect very different aspects of brain activity. To date more than 5 integrated PET/MR scanners have been set up in mainland China. China has the largest patient population, rapidly developing PET imaging techniques, and well-established capabilities in fMRI neuroimaging analytics. PET/fMRI studies require multi-disciplinary collaborations in nuclear medicine, radiology, chemistry, medical physics, computation science, and cognitive neuroscience. At the moment, the research management system in Chinese hospitals is not conducive to such collaborations and further improvement is needed to encourage multi-disciplinary research such as PET/fMRI. Given the known advantages in patient population and other resources, multi-center and multi-disciplinary studies hold the potential to put China at the leading edge of PET/fMRI research and produce high value results that will advance both neuroimaging sciences and future patient care in brain disorders.

Brain disease; Diagnosis; Positron-emission tomography; Magnetic resonance imaging; Trends