Experiments and FLUKA simulations of 12C^{12}C and 16O^{16}O beams for therapy monitoring by means of in-beam Positron Emission Tomography

Since 1997 at the experimental C-12 ion therapy facility at Gesellschaft fuer Schwerionenforschung (GSI), Darmstadt, Germany, more than 350 patients have been treated. The therapy is monitored with a dedicated positron emission tomograph, fully integrated into the treatment site. The measured beta+-activity arises from inelastic nuclear interactions between the beam particles an the nuclei of the patients tissue. Because the monitoring is done during the irradiation the method is called in-beam PET. The underlying principle of this monitoring is a comparison between the measured activity and a simulated one. The simulations are presently done by the PETSIM code which is dedicated to C-12 beams. In future ion therapy centers like the Heidelberger Ionenstrahl Therapiezentrum (HIT), Heidelberg, Germany, besides C-12 also proton, $^3$He and O-16 beams will be used for treatment and the therapy will be monitored by means of in-beam PET. Because PETSIM is not extendable to other ions in an easy way, a code capable to predict the beta+-activity created by all ions of interrest, also possible future ones, is needed. A candidate for such a role is the multi purpose particle transport and interaction Monte Carlo code FLUKA. The objective of this thesis is to investigate the ability of FLUKA to predict the beta+-activity induced by C-12 and O-16 beams, necessary for in-beam PET. Experiments with O-16 and C-12 beams on homogeneous targets of water, polymethyl methacrylate (PMMA) and graphite were performed and the created beta+-activity was measured by means of in-beam PET. In case of the O-16 beams this was done for the first time. The build up and decay of the beta+-active nuclei, their spatial distribution and total amount of produced beta+-activity was investigated. The experimental data was used for benchmarking FLUKA and its implemented nuclear reaction modells. Of special interrest was the performance of the recently added event generator BME which handels nucleus-nucleus interactions at low energies. FLUKA was interfaced with the part of PETSIM which modells the detector response and stores the detected events in list mode data format. This enables to process the simulated data exactly the same way than in the experimental case and avoids uncertainties due to the detection and backprojection. To reduce the computing time, full advantage of the biasing options in FLUKA was taken. Because of the double head geometry of the in-beam PET only a small fraction of the created annihilation photons can be detected. Because most of the annihilation photons produced are not detected, a lot of computing time is wasted. To futher speed up the simulations decay direction biasing for annihilation photons was introduced. This biasing preferentially emits the annihilation photons into a wanted direction, i.e. the detector heads. The use of this biasing additionally with other standard biasing methods brought an dramatic improvement in terms of computing time. In the final simulations good agreement between measured and simulated beta+-activity could be obtained within reasonable computing times. However, also limits of the new BME event generator in its present implementetion were pointed out

Criminology of Crime Avoidance: Creative Compliance Delinquency in the Borderlands of Legality

This article outlines the research program of a “criminology of crime avoidance” using the example of the preemptive use of legal opinions by white-collar actors to shift the boundaries of the law in their own favor. For this purpose, the term creative compliance is introduced and explained with regard to the Cum-Ex scandal in Germany. Then, a look is taken at possible criminological explanations for the phenomenon. Finally, the hypothesis is developed that law enforcement personnel is deterred from investigations by the reputational capital of certain legal advisors

Relativistic Meson Spectroscopy and In-Medium Effects

We extend our earlier model of $q\bar q$ mesons using relativistic quasipotential (QP) wave equations to include open-flavor states and running quark-gluon coupling effects. Global fits to meson spectra are achieved with rms deviations from experiment of 43-50 MeV. We examine in-medium effects through their influence on the confining interaction and predict the confining strength at which the masses of certain mesons fall below the threshold of their dominant decay channel.Comment: 12 Pages, 2 Postscript figures (appended at the end with instructions, available also from [email protected]

The Metal Promoted Hydration of di-2-pyridyl Ketone and the Crystal and Molecular Structures of bis-2,2\u27,N,N\u27-Bipyridyl Ketone-Hydrate Chromium(III) Chloride and Ruthenium(III) Chloride

The metal promoted hydration of Di-2-Pyridyl Ketone (DPK), has been of interest for some time in that it falls into a rare class of ligands that undergo reaction upon coordination to a transition metal ion. Metal promoted hydration here means that the carbonyl linkage of the ketone has undergone hydration to the diol form because the DPK is coordinated to a metal. Fig. 1 illustrates the hydration process. This is of interest because it is well known that ketones do not normally undergo hydration unless they are flanked by very strong electron withdrawing groups such as chloride or fluoride. Special mention must be made here about the role of the metal ion in that this hydration reaction should not be confused with a catalytic reaction. In this system, DPK becomes coordinated to the transition metal and remains in the complexed form throughout the hydration reaction of the ligand and remains attached thereafter. It has also been found that when DPK is coordinated to a metal ion in the hydrated form, it behaves in a tridentate fashion in that one of the oxygen atoms from the diol group forms a bond to the metal in the axial position. This third bond is very interesting in that the oxygen bonds in an unusual off axis position making an angle with the line normal to the equatorial plane (see Fig. 2). In 1:2 complexes of metal ion with DPK there is the possibility of pseudo-octahedral coordination about the metal ion. This study was undertaken in an attempt to gain additional insight into this intriguing system in hope that a better understanding of how this system works could be obtained

Time-Evolution of a Fractal Distribution: Particle Concentrations in Free-Surface Turbulence

Steady-state turbulence is generated in a tank of water and the trajectories of particles forming a compressible system on the surface are tracked in time. The initial uniformly distributed floating particles coagulate and form a fractal distribution, a rare manifestation of a fractal object observable in real-space. The surface pattern reaches a steady state in approximately 1 s. Measurements are made of the fractal dimensions $D_q(t)$ ($q=1$ to $6$) of the floating particles starting with the uniform distribution $D_q(0)$ = 2 for Taylor Microscale Reynolds number $Re_{\lambda} \simeq 160$. Focus is on the the time-evolution of the correlation dimension $D_2(t)$ as the steady state is approached. This steady state is reached in several large eddy turnover times and does so at an exponential rate

Intermingled basins in coupled Lorenz systems

We consider a system of two identical linearly coupled Lorenz oscillators, presenting synchro- nization of chaotic motion for a specified range of the coupling strength. We verify the existence of global synchronization and antisynchronization attractors with intermingled basins of attraction, such that the basin of one attractor is riddled with holes belonging to the basin of the other attractor and vice versa. We investigated this phenomenon by verifying the fulfillment of the mathematical requirements for intermingled basins, and also obtained scaling laws that characterize quantitatively the riddling of both basins for this system

Computerized Scanning Auger Microprobe

An Auger spectrometer has been automated using a microcomputer. Fundamental considerations in the design and choice of the computerized system are presented and should be of general interest. The spectrometer was a Physical Electronics Ind. model 545 scanning Auger microprobe. The microcomputer chosen was a Southwest Technical Products 6809 computer system. Hardware details are discussed with emphasis on the four computer-spectrometer interface boards. These boards are (1) Auger energy control board, which sets the Auger detection energy with its 16 bit digital-to-analog converter (DAC); (2) read Auger signal board, which reads the Auger signal intensity with its 12 bit analog-to-digital converter; (3) multipurpose DAC board, which uses two pairs of 8 bit DAC\u27s to position the excitation beam and display the data in memory on a CRT monitor, and (4) timing and relay control board, which selects various instruments and power supplies as required during the fully automated depth profiling sputter sequences. Organizational details of the control, analysis, and output software are discussed. The operation of the main Auger control program is emphasized along with its menu driven options, which provide great versatility to the operator. Examples are shown of the various data output modes, which include displays on the CRT monitor and plots from the multicolor digital plotter. © 1985, American Vacuum Society. All rights reserved