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During heavy ion therapy, some particles in the beam undergo atomic nuclear inelastic collisions with other nuclei in the target, resulting in the production of a range of nuclear fragments, including neutrons. The neutron component is moderated by matter in the target, causing them to lose energy and thermalise. These neutrons are of particular interest as they offer the potential for therapeutic applications via neutron capture. Accurate and reliable quantification of the thermal neutron fluence produced during particle therapy will provide valuable information regarding the feasibility of therapeutic exploitation of this thermal neutron field. However, measurement of thermal neutron fluence is extremely challenging due to the intense and diverse mixed radiation field in the target volume. In this work, we present the results of experimental quantification of thermal neutron fluence, performed using the gold activation method, during carbon and helium beam therapy. Geant4 Monte Carlo simulations were used to validate the approach, establishing that the activation of gold is almost exclusively due to neutron capture, and that nearly all gamma photons detected in the vicinity of 411 keV result from the decay of the activated gold. The method was then applied to experimentally measure the fluence of thermal neutrons per Gy(RBE) of delivered dose during carbon and helium beam therapy, both inside and outside of the beam in a poly(methyl methacrylate) (PMMA) phantom. Thermal neutron fluence was measured at four different depths: at the entrance, distal edge, middle of the SOBP and in the tail region of the spread-out Bragg peak (SOBP). o our knowledge, this is the first time that this method has been used in particle therapy., The 2019 IEEE Nuclear Science Symposium (NSS) and Medical Imaging Conference (MIC)

The purpose of this work is to develop a validated Geant4 simulation model of a whole-body prototype PET scanner constructed from the four-layer depth-of-interaction detectors developed at the National Institute of Radiological Sciences, National Institutes for Quantum and Radiological Science and Technology, Japan. The simulation model emulates the behaviour of the unique depth of interaction sensing capability of the scanner without needing to directly simulate optical photon transport in the scintillator and photodetector modules. The model was validated by evaluating and comparing performance metrics from the NEMA NU 2-2012 protocol on both the simulated and physical scanner, including spatial resolution, sensitivity, scatter fraction, noise equivalent count rates and image quality. The results show that the average sensitivities of the scanner in the field-of-view were 5.9 cps kBq−1 and 6.0 cps kBq−1 for experiment and simulation, respectively. The average spatial resolutions measured for point sources placed at several radial offsets were 5.2± 0.7 mm and 5.0± 0.8 mm FWHM for experiment and simulation, respectively. The peak NECR was 22.9 kcps at 7.4 kBq ml−1 for the experiment, while the NECR obtained via simulation was 23.3 kcps at the same activity. The scatter fractions were 44% and 41.3% for the experiment and simulation, respectively. Contrast recovery estimates performed in different regions of a simulated image quality phantom matched the experimental results with an average error of -8.7% and +3.4% for hot and cold lesions, respectively. The results demonstrate that the developed Geant4 model reliably reproduces the key NEMA NU 2-2012 performance metrics evaluated on the prototype PET scanner. A simplified version of the model is included as an advanced example in Geant4 version 10.5.

Heavy ion therapy is a form of radiotherapy in which a beam of highlyenergetic ions is used to deliver a therapeutic dose to a treatment region.Currently, there is no way of verifying the dose being delivered in real timeduring treatment. We present a method for non-invasive in-vivo calculation of the dose deposited by a heavy ion beam based on the observed distribution of positron-emitting radioactive fragments. By decomposing the observed activity distribution into profiles of each individual positron-emitting radionuclide and iteratively fitting each of these using a library of basis function profiles, the relative weights of each energy component of the beam can be estimated. The weighting factors can then be used to estimate the spatial distribution of the deposited dose, which can be compared to the treatment plan for verification of the accuracy of treatment delivery and identification of any misplaced dose.

The thesis of this paper is that Brasidas, while being second to no Spartan in courage and endurance, excelled them all, if not other Greek generals as well, even during his short life, in grasp of military principles, in energy, enterprise, leadership, in military genius.

A country probably gets the system of education it deserves. But lucky is that country where education is a natural growth and a tradition rather than the clean-cut system of an expert. Sparta very clearly followed a very ancient tradition—very ancient and very novel, as Xenophon says: παλαιοὶ ὄντες ἔτι καὶ νυ̃ν τοι̃ς ἄλλοις καινότατοί εἰσι—‘new ideals’ in education are usually the oldest.