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The aim of the SCINTIRAD experiment is to determine the radio-response of 188Rhenium (Re) in in vitro cells and the biodistribution in different organs of in vivo mice, and subsequently to assess the therapeutic effect on liver tumours induced in mice. Both the γ- and β- emissions of 188Re have been exploited in the experiment. The in vivo biodistribution in mice was studied also with a γ-camera using different parallel hole collimators. In the 188Re spectrum, while the 155 keV γ-peak is useful for imaging, the photons emitted at larger energies and the β-particles act as noise in the image reconstruction. The γ-cameras previously used to image biodistributions obtained with 99Tc are, therefore, not optimized for use with 188Re. A new setup of the γ-camera has been studied for 188Re: 66×66 YAP:Ce crystals (0.6×0.6×10 mm3, 5 μm optical insulation) guarantee a FOV of 40×40 mm2, a Hamamatsu R2486 PSPMT, 3 in. diameter, converts their light into an electrical signal and allows reconstructing the spatial coordinates of the light spot; incoming photon directions are selected through a lead collimator with 1.5 mm diameter hexagonal holes, 0.18 mm septa, 40 mm thickness. Using this setup, results have been obtained both with 99Tc filled and 188Re filled capillaries and wells. The energy spectrum of the collected photons and the spatial resolutions obtainable with the 188Re source will be presented.

Gamma, β + , β - and α emissions of radionuclides can be successfully spoiled in the preparation of radiopharmaceuticals as a useful tool in radiodiagnosis (imaging) and radiotherapy against cancer. For nuclear imaging, 99m Tc has become the “universal” isotope because of its physical characteristics in the field of scintigraphy (6 hours half-life, 140 keV γ emission) [1]. Among the radionuclides the β - emitters are particularly promising in radiotherapy for the capability of their 0.3-2.3 MeV electrons to penetrate tissues in a range of 0.5-12 mm avoiding problems related to cellular internalization of radiopharmaceuticals. 188 Re (16.9 hours half life), a β - and γ emitter similar to the congener 99m Tc, is a promising candidate in nuclear medicine. In fact, while the β - emission (85%, E max = 2.12 MeV) is relevant for therapeutic purposes, the γ-rays (15%, 155 keV) can be detected to evaluate the biodistribution of the radiunuclide. Because of its multiple decay modes, 188 Re might be used for a real-time monitoring of regional drug distribution during radiation therapy. Furthermore 188 Re is available as perrhenate from a 188 W/ 188 Re generator. To date, few data are available in the literature on the sensitivity of different tumour cells to such radionuclide. In this context, the aim of the experiment SCINTIRAD supported by the National Institute for Nuclear Physics (INFN, Italy) is to determine the radio-response of tumour cell lines treated “in vitro” with 188 Re, the biodistribution in different organs of “in vivo” mice and subsequently the therapeutic effect on tumours induced in mice. Furthermore, dedicated devices as an optimized YAP camera for the 188 Re photon spectrum and appropriate software have been developed and improved for imaging of small animals. In particular, we present preliminary results on the genotoxic effect of 188 Re-perrhenate on a panel of human tumour cell lines (U87, H460, MCF-7, LNCaP) in terms of inhibition of cell viability, micronuclei induction and apoptosis.