Recent investigations have shown that nuclear magnetic resonance (NMR) can be used in conjunction with a suitable chemical dosimeter to estimate the dose from ionizing radiation (Gore et al., Phys Med. Biol. 29, 1189-1197, 1984). Based on this fact it was proposed that spatial dose distributions can be measured in gels infused with the chemical dosimeter using NMR imaging. There have been few such attempts and they provided only qualitative results. In this paper, we report results demonstrating the feasibility of obtaining quantitative dose distribution measurements by this technique. It is shown that quantitative dose distribution measurements necessitate the calculation of relaxation rate maps. We have determined that the spin-spin relaxation rate is a more sensitive parameter than the spin-lattice relaxation rate. It is also demonstrated that the addition of chemical sensitizers could improve the dose sensitivity of the measured NMR parameters. The two features characterizing a photon beam, depth-dose relationship, and beam profile as measured by this technique are in good agreement with the measurements using conventional methods, ionization chambers, and film dosimetry.

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The Lp3/LP4, Lyf/Lpf, Ln2/Lef, Lp2 fg/Lo'f and the Lp 2 f5/Le2 transition probabi]ities have been measured for some 27 elements ranging in atomic number from 57La to 92U. Other L transitions have also been measured for a smaller number of elements in the same range of atomic numbers. This has been accomplished by bombarding these elements with a constant energy electron beam and measuring their x-ray emission spectrum. The measured ratios are compared with the most recent calculation based on a relativistic Hartree-Fock-Slater (RHFS) potential, and screened Coulomb potential. In general, the form of the dependence of these ratios on atomic number predicted by calculations based on a RHFS potential is favored and the agreement between theory and experiment ranges from excellent for the Le2/Lnf ratio to a discrepancy of about 22% in the Lp 2 fs/Lcyf ratio for elements of large atomic number.