¹¹C and¹⁵O Induced in the Mouse by 175 Mev Protons

Tissue Perfusion Rate Determined from the Decay of Oxygen-15 Activity After Photon Activation in Situ

“…The radioactive tissue water is washed out of the imaged volume through transcapillary exchange with water in plasma, and it is from the half time for such wash-out that the rate of tissue perfusion is determined. Studies in our laboratory with irradiated, packed red blood cells and also with irradiated rat hearts have established that substantial wash-out of 150, consistent with the above interpretation, can be expected after in situ photon activation of living tissue (8). Thus, from the data collected from gelatin and living matter, it is assumed that for several minutes after activation, the time dependence of positron emission from an activated tissue volume may be adequately described by two exponential terms, representing, respectively, signal decay from fixed and mobile fractions of 150.…”

“…This is consistent with the gradual filling of a capacitance. 8. The more complex model of bidirectional exocytosis or exocytosis linked to endocytosis cannot explain the present results in a simple fashion.…”

Verification of absolute ionization chamber dosimetry in a proton beam using carbon activation measurements

“…where A(t) is the activity induced in the detector during time of its irradiation and measured after period t that has elapsed since the end of the irradiation, (E) is the 12 C(p,pn) 11 C nuclear reaction cross section for protons of energy E incident on the irradiated detector, N is the number of carbon atoms in the detector, and is the decay constant of the reaction product, 11 C. The factor (1Ϫe Ϫ ) accounts for the accumulation of the 11 C nuclide during the detector irradiation while the exponent, e t , reflects the decrease in the 11 C activity after the irradiation has been finished.…”

“…First attempts to apply activation techniques to proton dosimetry and radiobiology were done in the 1970s and 1980s. 10,11 The carbon activation method found application as a standard method of dosimetry in a pulsed clinical proton beam 12 and has subsequently been implemented with several improvements. 13 Although neither the ion chamber, nor the carbon activation method is new in proton dosimetry, a direct comparison of these methods in a proton beam has not been reported previously.…”

“…5,9 The choice was therefore made in favor of the carbon activation technique. The carbon activation method is based on the 12 C(p,pn) 11 C nuclear reaction. First attempts to apply activation techniques to proton dosimetry and radiobiology were done in the 1970s and 1980s.…”