Low Level Gamma-Ray Scintillation Spectrometry: Experimental Requirements and Biomedical Applications

Research in radiobiology. Annual report of work in progress in the internal irradiation program

“…3), the exact value depending upon the energy region of the spectrum which is consi dered. Marinelli (1962), the low energy background was diminished significantly by the addition of a thin Pb layer inside the steel. In this case (Fig.…”

“…However, to avoid the gamma-rays from neutron capture by hydrogen in the polyethylene, thin, stainless steel sheets would be used if another positioner were to be built at this altitude. The framework was constructed of stainless steel tubing of 2.54 cm outside diameter, with silver soldered joints, to eliminate the use of welding rods that frequently contain variable amounts of Th, Ra, and K (Marinelli et al, 1962). The framework also supports a 3 mm thick steel plate, 64 cm x 45 cm, having two 22 cm wide slots into which the NaI (Tl) crystals can be inserted to place them reproducibly above the positioner.…”

“…Several authors have shown(Delwaide et .al., 1962,Lloyd 1964, Marinelli et al, 1962) that for chair-type positioners, a 10 to 24 hour period is.required for an administered 42K activity to become equilibrated with body potassium for purposes of i.!1 vivo counting. Following an overnight fast, about 4 uci 42K in a few ml of sterile solution were given orally to each of the adult subjects.…”

Gamma-ray spectrometry of humans at the University of Utah

“…Similarly, Peterson et al (1965) discovered a neutron background inside their shielded enclosure and reported a greater neutron production by cosmic ray muon interactions with a high atomic number (Z) material such as Pb than a low Z material such as H20. Evaporation neutrons arise from the interaction of cosmic ray nucleons and muons with nuclei (ICRU, 1972;Marinelli et al, 1962;Marinelli, 1962, 1964;Tongiorgi, 1949). Being of cosmic-ray origin, this effect increases greatly with altitude.…”

“…Being of cosmic-ray origin, this effect increases greatly with altitude. It seems likely that the muon component of the cosmic radiation (Roos, 1961) is at least partially responsible for the production of 0.5 MeV photons (ICRU, 1972;Marinelli et al, 1962;May and Marinelli, 1962) that are partially shielded from the crystals by the bulk of Can Man (as illustrated in Fig. Thick shields of iron, lead or other high Z materials produce more than thinner shields or those of lower Z materials.…”