Application of Nuclear Microlocalization Techniques to Biomedical Problems

Ion beams at the Brookhaven 3.5 MV Research Van de Graaff accelerator have been used for elemental analysis and distribution in biomedical samples. This paper will present results from several collaborations. Both collimated and uncollimated charged particle beams are used for elemental analysis by measurement of characteristic x-rays (PIXE). A collimated proton beam, using a pinhole collimator (~20 ¿m) has been used as a particle microprobe in the laboratory ambient. Thick, essentially unprepared, samples can be measured with general elemental sensitivities of ¿ 10 ppm. The spatial resolution and elemental sensitivity have proven adequate for many samples of tissue sections and cell clusters. Specimen damage by charged particle beams is discussed and results of cell irradiations by triton beams are presented. Deuterium localization has been carried out in cell uptake studies using the 2H(3H,n)4He reaction initiated by the triton beam at the accelerator. Alpha particles from the reaction register the deuterium distribution in a plastic track detector. This technique suggests that 3H may be replaced by the stable isotope H in tracer studies. Studies have included the detection of nonexchangeable 2H in oocytes and the uptake of deuterated thymidine in blood cells.