In contrast to previous results and predictions of biological models we observed dose-dependent differential effects of PDR and CLDR brachytherapy with reduced efficacy of PDR in the lower dose range.

The hypeffine structure seperations Av and gs-factors have been measured in the 2pZ 3p states of 13C (I= 1/2) and a2C (I--0), respectively, using the atomic beam magnetic resonance method. The results are Av(3pa, 13C) =4.200(25)MHz, Av(3P2, 13C)=372.593 (25) MHz, gj(3P1, 1zc)=1.501052 (13), and gj(3P2, 12C)= 1.501039 (15). After applying corrections due to perturbations by neighbouring fine structure levels one deduces the constants of the magnetic dipole interaction A(3pa, 13C)= + 2.838 (17) MHz, A(3P2, laC)= + 149.055 (10) MHz. No signs of the A-factors were determined by the experiment; they follow from the known positive sign of the nuclear magnetic moment /~I of 13C. Combining A(3P2, 13C) with the results of other measurements on aaC, yields pI(11C)=--0.964 (1)nm. L IntroductionIn 1963 Haberstroh et al. measured the hyperfine structure separations in the 2p 2 3p states of the 20.4-min carbon isotope 1~C (I=3/2) by atomic beam magnetic resonance 1. They obtained the coefficients A and B of the magnetic dipole and electric quadrupole interactions, respectively, in the aP 2 state and two possible values for A in the 3p1 state. This ambiguity in A (3p~) was due to two possible orderings of the hyperfine levels F= 3/2 and 5/2 in that state. The magnetic dipole moment of the ~C nucleus could not be deduced directly from these experiments. It was calculated by Moser et al. 2 from A(3p1) using various generalized Hartree-Fock wave functions for the configuration 1 s z 2s 2 2p z. In order to obtain an independent value for pi(~lC) to test these computations, as well as to resolve the ambiguity in A (3P1), it was deemed desirable to measure the hyperfine structure separations in the 3p states of stable 13C, the magnetic moment of which is known 3-5. The present paper

To better understand the relationship of the growth characteristics of tumor tissues and their response to ionizing radiation alone and in combination with local tumor hyperthermia, we compared three different tumor sublines of the Dunning rat prostate carcinoma R3327. This report includes results obtained with the anaplastic AT1 subline (volume doubling time 5.2 days), the moderately differentiated mucin-secreting HI subline (volume doubling time about 9 days) and the well-differentiated, hormone-dependent H subline (volume doubling time about 17 days). The effects of single doses of photons (10 to 40 Gy) with and without local tumor hyperthermia (35 min immersion at 43.5 degrees C) were quantified by growth delay. The time to reach five times the volume at the time of treatment after 30 Gy alone was found to be 56.0, 134.9 and 184.0 days for the R3327-AT1, HI and H tumors, respectively. The R3327-H tumor was more radiosensitive than the AT1 or HI subline. Five of nine R3327-H tumors were controlled locally with a single dose of photons (40 Gy). Local tumor hyperthermia alone induced growth delay in both differentiated tumors, while the anaplastic tumor subline did not respond. Combined treatment modalities with heat applied directly after irradiation revealed isoeffective thermal enhancement ratios for 30 Gy which decreased from 1.59 for the AT1 tumor and 1.42 for the HI tumor to 1.23 in the well-differentiated subline R3327-H.

Reports indicate that cancer of the prostate, soft tissue sarcomas, salivary gland tumors, and melanomas respond well to fast-neutron treatment. To better understand the action of fast neutrons on such tumor tissues, we have begun studies with the versatile Dunning rat prostate tumor system. In our initial studies with the R3327-AT1 subline we observed a relative biological effectiveness (RBE) of approximately 3 for single doses of 14-meV fast neutrons. As a continuation of those studies the present report discusses our findings following fractionated treatments with 10 equal fractions of 14-MeV fast neutrons or 60Co gamma rays at several dose levels per fraction. After either fractionated neutron or photon treatment the volume of the tumors continued to increase for 2 weeks and then reached a plateau, the level of which was dose dependent. Tumor growth resumed and no local control was observed. Analysis of the data using growth delay as biological end point yielded an RBE of approximately 4.2 +/- 1.3.