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The problem of searching ways to enhance efficiency of cancer treatment is extremely important. One of the currently recognized methods of treatment is radiation therapy. However, efficiency of radiotherapy is limited by radiosensitivity of intact tissues surrounding the tumor on the one hand, and by radioresistance of the malignancy on the other hand. The problem of overcoming radiation resistance of tumors is a key element in the local control of tumor growth [1]. Introduction of radiosensitizers into a tumor with subsequent irradiation results in secondary radiation inside the tumor, thus increasing the effect of radiotherapy. Various substances capable of converting ionizing radiation can serve as radiosensitizers. This may be diagnostic preparations containing heavy chemical elements, such as iodine, gadolinium, gold nanoparticles, platinum and other chemicals [5]. The aim of our experiment was selection of a drug which would give a significant increase of the secondary radiation in biological tissues when irradiating with gamma rays (GR) with the energy of 1.25 MeV. We used as a radiation sensitizer a drug containing gold nanoparticles and iodine particles which, when introduced directly into a tumor, will increase energy of the radiation inside the tumor without increasing the dose permitted according to the plan of exposure.

A new method is suggested for improving the accuracy of energy-dispersive x-ray fluorescence analysis (EDXRF) and its implementation is described. This method is a result of studying changes in coefficients of the inter-elemental effect, A = f .Z/. We created a data bank for elements from K to Br, which accounts for the effect of three lighter and five heavier neighboring elements upon the sought element. This study offers a physical explanation of sharp bends in coefficient curves. We suggest principles for optimizing the analytical region parameters so as to reduce the effect of neighboring elements. Finally, we describe the principles of building a data bank A = f .Z, R/ to account for the effect of energy resolution (R) change. Application of the suggested method to the exploration of oceanic nodules reduced the cobalt detection threshold by 50-75% (C lim−0.95 = 0.032%) and decreased the standard deviation of spectrum analysis, thus enhancing confidence in EDXRF as an effective tool for research on complex objects. The approach suggested in this study can be used with newer energy-dispersive analyzers, including TXRF models.

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