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PURPOSE: Neutron Capture Enhanced Particle Therapy (NCEPT) is a proposed augmentation of charged particle therapy which exploits thermal neutrons generated internally, within the treatment volume via nuclear fragmentation, to deliver a biochemically targeted radiation dose to cancer cells. This work is the first experimental demonstration of NCEPT, performed using both carbon and helium ion beams with two different targeted neutron capture agents (NCAs). MATERIALS AND METHODS: Human glioblastoma cells (T98G) were irradiated by carbon and helium ion beams in the presence of NCAs, [10B]-BPA and [157Gd]-DOTA-TPP. Cells were positioned within a PMMA phantom either laterally adjacent to, or within, a 100 × 100 × 60 mm spread out Bragg peak (SOBP). The impact of NCAs and location relative to the SOBP on the cells was measured by cell growth and survival assays in six independent experiments. Neutron fluence within the phantom was characterised by quantifying the neutron activation of gold foil. RESULTS: Cells placed inside the treatment volume reached 10% survival by 2 Gy of C or 2-3 Gy of He in the presence of NCAs compared to 5 Gy of C and 7 Gy of He with no NCA. Cells placed adjacent to the treatment volume showed a dose-dependent decrease in cell growth when treated with NCAs, reaching 10% survival by 6 Gy of C or He (to the treatment volume), compared to a no detectable effect on cells without NCA. The mean thermal neutron fluence at the centre of the SOBP was approximately 2.2 × 109 n/cm2/Gy(RBE) for the carbon beam and 5.8 × 109 n/cm2/Gy(RBE) for the helium beam and gradually decreased in all directions. CONCLUSIONS: The addition of NCAs to cancer cells during C and He beam irradiation has a measurable impact on cell survival and growth in-vitro. Through the capture of internally generated neutrons, NCEPT introduces the concept of a biochemically targeted radiation dose to charged particle therapy. NCEPT enables the established pharmaceuticals and concepts of neutr

This paper presents a new version of the 3D mesa "bridge" microdosimeter comprised of an array of 4248 silicon cells fabricated on 10 µm thick silicon-on-insulator substrate. This microdosimeter has been designed to overcome limitations existing in previous generation silicon microdosimeters and it provides well-defined sensitive volumes and high spatial resolution. The charge collection characteristics of the new 3D mesa microdosimeter were investigated using the ANSTO heavy ion microprobe, utilizing 5.5 MeV He2+ ions. Measurement of microdosimetric quantities allowed for the determination of the Relative Biological Effectiveness of 290 MeV/u and 350 MeV/u 12C heavy ion therapy beams at the Heavy Ion Medical Accelerator in Chiba (HIMAC), Japan. The microdosimetric RBE obtained showed good agreement with the tissue-equivalent proportional counter. Utilizing the high spatial resolution of the SOI microdosimeter, the LET spectra for 70 MeV 12C+6 ions, like those present at the distal edge of 290 and 350 MeV/u beams, were obtained as the ions passed through thin layers of polyethylene film. This microdosimeter can provide useful information about the lineal energy transfer (LET) spectra downstream of the protective layers used for shielding of electronic devices for single event upset prediction.

Background and purpose: Characterization of the out-of-field dose profile following irradiation of the target with a 3D treatment plan delivered with modern techniques. Methods: An anthropomorphic RANDO phantom was irradiated with a treatment plan designed for a simulated 5×2×5cm 3 tumor volume located in the center of the head. The experiment was repeated with all most common radiation treatment types (photons, protons and carbon ions) and delivery techniques (Intensity Modulated Radiation Therapy, passive modulation and spot scanning). The measurements were performed with active diamond detector and passive thermoluminescence (TLD) detectors to investigate the out-of-field dose both inside and outside the phantom. Results: The highest out-of-field dose values both on the surface and inside the phantom were measured during the treatment with 25 MV photons. In the proximity of the Planned Target Volume (PTV), the lowest lateral dose profile was observed for passively modulated protons mainly because of the presence of the collimator in combination with the chosen volume shape. In the far out-of-field region (above 100 mm from the PTV), passively modulated ions were characterized by a less pronounced dose fall-off in comparison with scanned beams. Overall, the treatment with scanned carbon ions delivered the lowest dose outside the target volume. Conclusions: For the selected PTV, the use of the collimator in proton therapy drastically reduced the dose deposited by ions or photons nearby the tumor. Scanning modulation represents the optimal technique for achieving the highest dose reduction far-out-of-field.