Body ownership refers to the special perceptual status of one's own body, which makes bodily sensations seem unique to oneself. We studied the neural correlates of body ownership by controlling whether an external object was accepted as part of the body or not. In the rubber hand illusion (RHI), correlated visuotactile stimulation causes a fake hand to be perceived as part of one's own body. In the present study, we distinguished between the causes (i.e., multisensory stimulation) and the effect (i.e., the feeling of ownership) of the RHI. Participants watched a right or a left rubber hand being touched either synchronously or asynchronously with respect to their own unseen right hand. A quantifiable correlate of the RHI is a shift in the perceived position of the subject's hand toward the rubber hand. We used positron emission tomography to identify brain areas whose activity correlated with this proprioceptive measure of body ownership. Body ownership was related to activity in the right posterior insula and the right frontal operculum. Conversely, when the rubber hand was not attributed to the self, activity was observed in the contralateral parietal cortex, particularly the somatosensory cortex. These structures form a network that plays a fundamental role in linking current sensory stimuli to one's own body and thus also in self-consciousness.

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Radiolabeled somatostatin analogs represent valuable tools for both in vivo diagnosis and therapy of neuroendocrine tumors (NETs) because of the frequent tumoral overexpression of somatostatin receptors (sst). The 2 compounds most often used in functional imaging with PET are 68 Ga-DOTATATE and 68 Ga-DOTATOC. Both ligands share a quite similar sst binding profile. However, the in vitro affinity of 68 Ga-DOTATATE in binding the sst subtype 2 (sst2) is approximately 10-fold higher than that of 68 Ga-DOTATOC. This difference may affect their efficiency in the detection of NET lesions because it is the sst2 that is predominantly overexpressed in NET. We thus compared the diagnostic value of PET/CT with both radiolabeled somatostatin analogs ( 68 Ga-DOTATATE and 68 Ga-DOTATOC) in the same NET patients. Methods: Forty patients with metastatic NETs underwent 68 Ga-DOTATOC and 68 Ga-DOTATATE PET/CT as part of the work-up before prospective peptide receptor radionuclide therapy. The performance of both imaging methods was analyzed and compared for the detection of individual lesions per patient and for 8 defined body regions. A region was regarded positive if at least 1 lesion was detected in that region. In addition, radiopeptide uptake in terms of the maximal standardized uptake value (SUVmax) was compared for concordant lesions and renal parenchyma. Results: Seventy-eight regions were found positive with 68 Ga-DOTATATE versus 79 regions with 68 Ga-DOTATOC (not significant). Overall, however, significantly fewer lesions were detected with 68 Ga-DOTATATE than with 68 Ga-DOTATOC (254 vs. 262, P , 0.05). Mean 68 Ga-DOTATATE SUVmax across all lesions was significantly lower than 68 P , 0.01). Mean SUVmax for renal parenchyma was not significantly different between 68 Ga-DOTATATE and 68 Ga-DOTATOC (12.7 6 3.0 vs. 13.2 6 3.3). Conclusion: 68 Ga-DOTATOC and 68 Ga-DOTATATE possess a comparable diagnostic accuracy for the detection of NET lesions, with 68 Ga-DOTATOC having a potential advantage. The approximately 10-fold higher affinity for the sst2 of 68 Ga-DOTATATE does not prove to be clinically relevant. Quite unexpectedly, SUVmax of 68 Ga-DOTATOC scans tended to be higher than their 68 Ga-DOTATATE counterparts.

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