A new method utilizing alpha particles to treat solid tumors is presented. Tumors are treated with interstitial radioactive sources which continually release short-lived alpha emitting atoms from their surface. The atoms disperse inside the tumor, delivering a high dose through their alpha decays. We implement this scheme using thin wire sources impregnated with (224)Ra, which release by recoil (220)Rn, (216)Po and (212)Pb atoms. This work aims to demonstrate the feasibility of our method by measuring the activity patterns of the released radionuclides in experimental tumors. Sources carrying (224)Ra activities in the range 10-130 kBq were used in experiments on murine squamous cell carcinoma tumors. These included gamma spectroscopy of the dissected tumors and major organs, Fuji-plate autoradiography of histological tumor sections and tissue damage detection by Hematoxylin-Eosin staining. The measurements focused on (212)Pb and (212)Bi. The (220)Rn/(216)Po distribution was treated theoretically using a simple diffusion model. A simplified scheme was used to convert measured (212)Pb activities to absorbed dose estimates. Both physical and histological measurements confirmed the formation of a 5-7 mm diameter necrotic region receiving a therapeutic alpha-particle dose around the source. The necrotic regions shape closely corresponded to the measured activity patterns. (212)Pb was found to leave the tumor through the blood at a rate which decreased with tumor mass. Our results suggest that the proposed method, termed DART (diffusing alpha-emitters radiation therapy), may potentially be useful for the treatment of human patients.

Arguments are presented which show that the transverse and longitudinal nuclidic mass relationships of Garvey and Kelson (GK-T and GK-L) contain small but systematic errors. If masses far off the line of fl-stability are calculated, these errors accumulate in the repeated application of the relationships, and the diverging predictions from GK-T and GK-L seem to represent estimates of upper and lower limits only. A new generalized nuclidic mass relationship is introduced.Nuclidic mass relationships constitute an important tool for estimating the masses of unknown nuclei close to and far away from the region of known nuclei. Garvey and Kelson 1 derived the relationship M(A, T~+ 2)-M(A, Tz)+ M(A-1, T~+ 89 -M(A-1, T~+~)+M(A+I, T~+ 891, T~+~)~0(1) assuming an independent-particle model with fourfold degenerate singleparticle orbits. In a later article Garvey et aI. 2 showed that Eq. (1) can also be derived by requiring that the sum over a subset of masses leads to a first-order cancellation of all single-particle energies and of the interactions between nucleons. These requirements also lead to another mass relationship 2, namely M(A+4, T~)-M(A, T~)+M(A+ I, T~+ 89 -M(A+3, T,+ 89Tz-89 T~-89Eqs.(1) and (2) will be referred to as the transverse and the longitudinal Garvey-Kelson nuclidic mass relationships GK-T and GK-L, respectively. The relationship GK-T has been widely used in the past to estimate * On sabbatical leave from The University of Michigan, Ann Arbor, Michigan.

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Two new independent mass relations are derived and are shown to be consistent with several existing nuclear models. The most general functional dependence on proton number, neutron number, and mass number (or isospin value) of masses which satisfy these relations exactly is discussed, and a procedure for determining the values of these functions which give a best least-squares fit to the body of known masses is developed. The functions which give the best over-all fit are listed together with the resulting theoretical mass table which shows the discrepancies to known masses and the theoretical values for proton, neutron, and alpha-particle decay energies.

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