Metallic nanoparticles (MNP) are able to release localized x-rays when activated with a high energy proton beam by the particle-induced x-ray emission (PIXE) effect. The exploitation of this phenomenon in the therapeutic irradiation of tumors has been investigated. PIXE-based x-ray emission directed at CT26 tumor cells in vitro, when administered with either gold (average diameter 2 and 13 nm) or iron (average diameter 14 nm) nanoparticles (GNP or SNP), increased with MNP solution concentration over the range of 0.1-2 mg ml(-1). With irradiation by a 45 MeV proton therapy (PT) beam, higher concentrations had a decreased cell survival fraction. An in vivo study in CT26 mouse tumor models with tumor regression assay demonstrated significant tumor dose enhancement, thought to be a result of the PIXE effect when compared to conventional PT without MNP (radiation-only group) using a 45 MeV proton beam (p < 0.02). Those receiving GNP or SNP injection doses of 300 mg kg(-1) body weight before proton beam therapy demonstrated 90% or 75% tumor volume reduction (TVR) in 20 days post-PT while the radiation-only group showed only 18% TVR and re-growth of tumor volume after 20 days. Higher complete tumor regression (CTR) was observed in 14-24 days after a single treatment of PT with an average rate of 33-65% for those receiving MNP compared with 25% for the radiation-only group. A lower bound of therapeutic effective MNP concentration range, in vivo, was estimated as 30-79 µg g(-1) tissue for both gold and iron nanoparticles. The tumor dose enhancement may compensate for an increase in entrance dose associated with conventional PT when treating large, solid tumors with a spread-out Bragg peak (SOBP) technique. The use of a combined high energy Bragg peak PT with PIXE generated by MNP, or PIXE alone, may result in new treatment options for infiltrative metastatic tumors and other diffuse inflammatory diseases.

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The cold-cathode-type Penning ion gauge (PIG) ion source for the internal ion source of KIRAMS-13 cyclotron has been used for generation of negative hydrogen ions. The dc H-beam current of 650 microA from the PIG ion source with the Dee voltage of 40 kV and arc current of 1.0 A is extrapolated from the measured dc extraction beam currents at the low extraction dc voltages. The output optimization of PIG ion source in the cyclotron has been carried out by using various chimneys with different sizes of the expansion gap between the plasma boundary and the chimney wall. This paper presents the results of the dc H-extraction measurement and the expansion gap experiment.

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High energy proton induced neutron fluence spectra were determined at the Korea Institute of Radiological and Medical Sciences (KIRAMS) using an extended Bonner Sphere (BS) set from the Korea Atomic Energy Research Institute (KAERI) in a series of measurements to quantify the neutron field. At the facility of the MC50 cyclotron of KIRAMS, two Be targets of different thicknesses, 1.0 and 10.5 mm, were bombarded by 35 and 45-MeV protons to produce six kinds of neutron fields, which were classified according to the measurement position and the use or no use of a beam collimator such as the gantry of the neutron therapy unit. In order to obtain a priori information to unfold the measured BS data the MCNPX code was used to calculate the neutron spectrum, and the influence of the surrounding materials for cooling the target assembly were also reviewed through this calculation. Some dosimetric quantities were determined by using the spectra determined in this measurement. Dose equivalent rates of these neutron fields ranged from 0.21 to 5.66 mSv h(-1)nA(-1) and the neutron yields for a thick Be target were 3.05 and 4.77% in the case of using a 35 and a 45-MeV proton, respectively.