[The nuclear medicine department and the TEP/Biomedical Cyclotron unit]. / Le Service de Médecine Nucléaire et l'Unité TEP/Cyclotron Biomedical.

During the last 25 years, the clinical and experimental activity in nuclear medicine at Erasme hospital has been influenced by the implementation of positron emission tomography (PET) in 1990 as a method of brain functional investigation. The activity of the PET/biomedical cyclotron unit has been dedicated to various subjects in neurology, neurosciences, psychiatry, oncology and cardiology. This has been made possible by developments in radiochemistry. The radiochemistry laboratory has designed and produced original tracers such as 9-[(3-[18F]fluoro-1-hydroxy-2-propoxy)-methyl]guanine (FHPG), a tracer of viral thymidine kinase activity in gene therapy protocols. We have brought new applications of PET, such as its integration into stereotactic neurosurgical and radioneurosurgical techniques in order to improve their diagnostic and therapeutic performance in neurooncology. We have also conducted multiple studies on brain physiology and pathophysiology, in particular with the use of functional and metabolic brain mapping methods and the use of tracers of neurotransmission systems. The Department of nuclear medicine has also performed studies on bone metabolism and investigated in vivo imaging methods of infectious and immune processes.

Assessing study-specific regional variations in fMRI signal.

In this paper, we present a post hoc method for identifying regions where functional MRI data are subject to signal reduction that may compromise sensitivity to activations. The motivation for developing this technique derives from recent language studies that showed responses in the inferior temporal lobe that could be detected by PET but not by fMRI. Reduced signal is due mostly to susceptibility artifacts and can be identified by comparing the T2* images (which are subject to susceptibility artifacts) with T2 images (which are not). However, T2 images are not usually acquired in fMRI studies. Therefore, we propose that areas with reduced signal can be identified by comparing T2* images that are corrected for nonuniformity with the original uncorrected images. The technique provides a voxel-wise characterization of signal reduction that pertains to the particular data that enter into a statistical model. It requires only the functional data and can thus be applied post hoc and without any additional scans.