A novel radioguided surgery (RGS) technique for cerebral tumors using β − radiation is being developed. Checking for a radiotracer that can deliver a β − emitter to the tumor is a fundamental step in the deployment of such a technique. This paper reports a study of the uptake of 90 Y-DOTATOC in meningiomas and high-grade gliomas (HGGs) and a feasibility study of the RGS technique in these types of tumor. Estimates were performed assuming the use of a β − probe under development with a sensitive area 2.55 mm in radius to detect 0.1-mL residuals. Methods: Uptake and background from healthy tissues were estimated on 68 Ga-DOTATOC PET scans of 11 meningioma patients and 12 HGG patients. A dedicated statistical analysis of the DICOM images was developed and validated. The feasibility study was performed using full simulation of emission and detection of the radiation, accounting for the measured uptake and background rate. Results: All meningioma patients but one with an atypical extracranial tumor showed high uptake of DOTATOC. In terms of feasibility of the RGS technique, we estimated that by administering a 3 MBq/kg activity of radiotracer, the time needed to detect a 0.1-mL remnant with 5% false-negative and 1% falsepositive rates is less than 1 s. Actually, to achieve a detection time of 1 s the required activities to administer were as low as 0.2-0.5 MBq/kg in many patients. In HGGs, the uptake was lower than in meningiomas, but the tumor-to-nontumor ratio was higher than 4, which implies that the tracer can still be effective for RGS. It was estimated that by administering 3 mBq/kg of radiotracer, the time needed to detect a 0.1-mL remnant is less than 6 s, with the exception of the only oligodendroma in the sample. Conclusion: Uptake of 90 Y-DOTATOC in meningiomas was high in all studied patients. Uptake in HGGs was significantly worse than in meningiomas but was still acceptable for RGS, particularly if further research and development are done to improve the performance of the β − probe. Radi oguided surgery (RGS) helps the surgeon evaluate the completeness of a tumor resection while minimizing the amount of healthy tissue removed (1). The surgeon is provided with vital and real-time information on the location and extent of the lesion and can assess the resection margins. The technique uses a radiolabeled tracer preferentially taken up by the tumor to discriminate cancerous tissue from healthy organs, as well as a probe (2) sensitive to the emission released by the tracer to identify in real time the targeted tumor focus. The radiopharmaceutical is administered to the patient before surgery.Current clinical applications of RGS are radioimmunoguided surgery for colon cancer (3,4), complete sentinel-node mapping for malignant melanoma (5) and breast cancer (6,7), and detection of parathyroid adenoma (8) and bone tumors (such as osteoid osteoma). There are also clinical studies on applications in neuroendocrine tumors (9,10).Established methods use a combination of a g-emitting tracer with a g-radiation-detec...

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The morphology and the immunohistochemistry of the caudal neurosecretory system of Dicentrarchus labrax were analysed after the fish acclimatation to fresh water. Two different sized neurosecretory cells have been identified in seawater-acclimated fish and denoted as anterior and posterior cells. The two types of cells share similar patterns and intensities of immunoreactivity with urotensin I and urotensin II antisera. Posterior neurosecretory cells decreased in size in freshwater-acclimated specimens, whereas anterior cells did not show changes. Urophyses of seawater-and freshwateracclimated fish reacted with both antisera. Immunohistochemistry of the urophysis did not provide evidence for a significant difference in the activity of the caudal neurosecretory system between seawater-and freshwater-acclimated fish. However, on a morphological basis it was possible to suggest that the caudal neurosecretory system of the sea bass is involved in the hyperosmoregulation.

Morphological features of the goldfish caudal neurosecretory system were investigated by means of immunohistochemical localization of urotensins I and II (UI and UII) and electron microscopic examination of the caudal neurosecretory neurons, the urophysis, and the synaptic neuropil. The aim of the work is to provide a detailed morphological description of the afferent synapses to the caudal neurons and to analyze their distribution through the rostrocaudal extension of the caudal neurosecretory system. Three morphologically different types of neurosecretory cells have been identified according to size and shape: large, medium, and small Dahlgren cells. The three different-sized cells share similar patterns of immunoreactivity with the UI (or oCRF) and the UII antisera. Electron microscopic examination of the synaptic neuropil throughout the caudal system revealed the presence of four types of terminals: dense-cored-vesicle end bulbs (DC), spherical-vesicle end bulbs (S), flattened-vesicle end bulbs (F), and granular-vesicle end bulbs (G). The present study demonstrates that the small Dahlgren cells receive different synaptic inputs from the large and the medium neurosecretory cells. Indeed, G terminals are only found on the small Dahlgren cells, whereas DC, S, and F terminals are distributed on the large, medium, and small Dahlgren cell bodies and proximal processes.

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