249 research outputs found
A fast - Monte Carlo toolkit on GPU for treatment plan dose recalculation in proton therapy
In the context of the particle therapy a crucial role is played by Treatment Planning Systems (TPSs), tools aimed to compute and optimize the tratment plan. Nowadays one of the major issues related to the TPS in particle therapy is the large CPU time needed. We developed a software toolkit (FRED) for reducing dose recalculation time by exploiting Graphics Processing Units (GPU) hardware. Thanks to their high parallelization capability, GPUs significantly reduce the computation time, up to factor 100 respect to a standard CPU running software. The transport of proton beams in the patient is accurately described through Monte Carlo methods. Physical processes reproduced are: Multiple Coulomb Scattering, energy straggling and nuclear interactions of protons with the main nuclei composing the biological tissues. FRED toolkit does not rely on the water equivalent translation of tissues, but exploits the Computed Tomography anatomical information by reconstructing and simulating the atomic composition of each crossed tissue. FRED can be used as an efficient tool for dose recalculation, on the day of the treatment. In fact it can provide in about one minute on standard hardware the dose map obtained combining the treatment plan, earlier computed by the TPS, and the current patient anatomic arrangement
A fast - Monte Carlo toolkit on GPU for treatment plan dose recalculation in proton therapy
In the context of the particle therapy a crucial role is played by Treatment Planning Systems (TPSs), tools aimed to compute and optimize the tratment plan. Nowadays one of the major issues related to the TPS in particle therapy is the large CPU time needed. We developed a software toolkit (FRED) for reducing dose recalculation time by exploiting Graphics Processing Units (GPU) hardware. Thanks to their high parallelization capability, GPUs significantly reduce the computation time, up to factor 100 respect to a standard CPU running software. The transport of proton beams in the patient is accurately described through Monte Carlo methods. Physical processes reproduced are: Multiple Coulomb Scattering, energy straggling and nuclear interactions of protons with the main nuclei composing the biological tissues. FRED toolkit does not rely on the water equivalent translation of tissues, but exploits the Computed Tomography anatomical information by reconstructing and simulating the atomic composition of each crossed tissue. FRED can be used as an efficient tool for dose recalculation, on the day of the treatment. In fact it can provide in about one minute on standard hardware the dose map obtained combining the treatment plan, earlier computed by the TPS, and the current patient anatomic arrangement
Combining proton or photon irradiation with epothilone B : An in vitro study of cytotoxicity in human cancer cells
Recently, the use of proton beams in cancer therapy is becoming widespread, and tumour treatment modalities combining radiosensitizing chemical agents with irradiation are under investigation in order to achieve greater tumour local control and reduce the probability of distant failures. The combined treatment modality of radiation and the clinically relevant microtubule-stabilizing compound epothilone B is a promising approach for anticancer therapy. In the present study, we investigated the cytotoxicity of a spread out Bragg peak (SOBP) proton beam, as well as of 6 MV photons, in human glioblastoma (U251 MG) and lung adenocarcinoma (A549) cells pretreated for 24 h, or not, with epothilone B at concentrations of 0.125 and 0.075 nM respectively. Proton irradiation was performed at the middle position of an actively modulated SOBP (12\u201318 cm depth in water) and cell survival was evaluated by a colony forming assay. For both cell lines, survival curves after proton or photon irradiation alone showed linear quadratic behaviour with proton RBE (relative biological effectiveness), compared with photons at 10% survival, of 1.5 \ub1 0.2. Treatment of cells with epothilone B at subnanomolar concentration has an anticlonogenic effect. Furthermore, differently from the results found with radiation alone, the survival curves for the combined treatment epothilone B\u2013radiation showed a linear trend and analysis of the interaction of the two cytotoxic agents indicated a slight synergism. These data provide a radiobiological basis for further experiments, as well as clinical studies
The Maximal Denumerant of a Numerical Semigroup
Given a numerical semigroup S = and n in S, we
consider the factorization n = c_0 a_0 + c_1 a_1 + ... + c_t a_t where c_i >=
0. Such a factorization is maximal if c_0 + c_1 + ... + c_t is a maximum over
all such factorizations of n. We provide an algorithm for computing the maximum
number of maximal factorizations possible for an element in S, which is called
the maximal denumerant of S. We also consider various cases that have
connections to the Cohen-Macualay and Gorenstein properties of associated
graded rings for which this algorithm simplifies.Comment: 13 Page
Tunable linear and quadratic optomechanical coupling for a tilted membrane within an optical cavity: theory and experiment
We present an experimental study of an optomechanical system formed by a
vibrating thin semi-transparent membrane within a high-finesse optical cavity.
We show that the coupling between the optical cavity modes and the vibrational
modes of the membrane can be tuned by varying the membrane position and
orientation. In particular we demonstrate a large quadratic dispersive
optomechanical coupling in correspondence with avoided crossings between
optical cavity modes weakly coupled by scattering at the membrane surface. The
experimental results are well explained by a first order perturbation treatment
of the cavity eigenmodes.Comment: 10 pages, 6 figure
RIDOS: A new system for online computation of the delivered dose distributions in scanning ion beam therapy
Online monitoring for proton therapy: A real-time procedure using a planar PET system
In this study a procedure for range verification in proton therapy by means of a planar in-beam PET system is presented. The procedure consists of two steps: the measurement of the β+-activity induced in the irradiated body by the proton beam and the comparison of these distributions with simulations. The experimental data taking was performed at the CNAO center in Pavia, Italy, irradiating plastic phantoms. For two different cases we demonstrate how a real-time feedback of the delivered treatment plan can be obtained with in-beam PET imaging
Observation of the Three-Mode Parametric Instability
Three-mode parametric interactions occur in triply-resonant optomechanical
systems: photons from an optical pump mode are coherently scattered to a
high-order mode by mechanical motion of the cavity mirrors, and these modes
resonantly interact via radiation pressure force when certain conditions are
met. Such effects are predicted to occur in long baseline advanced
gravitational-wave detectors. They can pump energy into acoustic modes, leading
to parametric instability, but they can also extract acoustic energy, leading
to optomechanical cooling. We develop a large amplitude model of three-mode
interactions that explains the ring-up amplitude saturation after instability
occurs. We also demonstrate both radiation-pressure cooling and mechanical
amplification in two different three-mode optomechanical systems, including the
first observation of the three-mode parametric instability in a free-space
Fabry-Perot cavity. The experimental data agrees well with the theoretical
model. Contrary to expectations, parametric instability does not lead to loss
of cavity lock, a fact which may make it easier to implement control techniques
to overcome instability.Comment: 11 pages, 14 figure
First tests for an online treatment monitoring system with in-beam PET for proton therapy
PET imaging is a non-invasive technique for particle range verification in
proton therapy. It is based on measuring the beta+ annihilations caused by
nuclear interactions of the protons in the patient. In this work we present
measurements for proton range verification in phantoms, performed at the CNAO
particle therapy treatment center in Pavia, Italy, with our 10 x 10 cm^2 planar
PET prototype DoPET. PMMA phantoms were irradiated with mono-energetic proton
beams and clinical treatment plans, and PET data were acquired during and
shortly after proton irradiation. We created 1-D profiles of the beta+ activity
along the proton beam-axis, and evaluated the difference between the proximal
rise and the distal fall-off position of the activity distribution. A good
agreement with FLUKA Monte Carlo predictions was obtained. We also assessed the
system response when the PMMA phantom contained an air cavity. The system was
able to detect these cavities quickly after irradiation.Comment: 11 pages, 6 figures, Proceedings for International Workshop on
Radiation Imaging Detectors, 201
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