Ortsdosimetrie in gepulsten Strahlungsfeldern

In dem Bericht werden Methoden und Ergebnisse experimenteller Untersuchungen an verfügbaren Ortsdosisleistungsmessgeräten in Feldern gepulster, ionisierender Strahlung beschrieben. Es zeigte sich, dass die meisten Messgeräte nur erheblich eingeschränkt für die Messung dieser Art Strahlung geeignet sind. Ionisationskammern, soweit einsetzbar, stellen das geeignetste der untersuchten Messprinzipien dar. Felder gepulster Strahlung treten bei einer Vielzahl industrieller, medizinischer und wissenschaftlicher Anwendungen auf. Die Veröffentlichung richtet sich an die in diesen Bereichen tätigen Strahlenschützer

Channeling radiation on quartz stimulated by acoustic waves

The stimulation of channeling radiation by acoustic waves excited in the single crystal has been predicted in early works of the 1980’s. Based on quantum calculations, the described experiment aimed at verification of theoretical considerations. Making use of the reverse piezoelectric effect, hypersonic waves of frequency 12GHz, which corresponds to a dedicated transition between bound states of planar channelled relativistic electrons, were excited in a single-Crystal quartz plate. The spectrum of channeling radiation measured under the influence of acoustic waves reveals enhanced radiation intensity. The obtained results are discussed and may be phenomenologically understood assuming electron diffraction on an acoustic superlattice

Advanced sandwich composite cores for patient support in advanced clinical imaging and oncology treatment

Ongoing advances in both imaging and treatment for oncology purposes have seen a significant rise in the use of not only the individual imaging modalities, but also their combination in single systems such as Positron Emission Tomography combined with Computed Tomography (PET–CT) and PET–MRI (Magnetic Resonance Imaging) when planning for advanced oncology treatment, the most demanding of which is proton therapy. This has identified issues in the availability of suitable materials upon which to support the patient undergoing imaging and treatment owing to the differing requirements for each of the techniques. Sandwich composites are often selected to solve this issue but there is little information regarding optimum materials for their cores. In this paper, we presented a range of materials which are suitable for such purposes and evaluated the performance for use in terms of PET signal attenuation, proton beam stopping, MRI signal shading and X-Ray CT visibility. We found that Extruded Polystyrene offers the best compromise for patient support and positioning structures across all modalities tested, allowing for significant savings in treatment planning time and delivering more efficient treatment with lower margins

Passive SOBP generation from a static proton pencil beam using 3D-printed range modulators for FLASH experiments

The University Proton Therapy facility in Dresden (UPTD), Germany, is equipped with an experimental room with a beamline providing a static pencil beam. High proton beam currents can be achieved at this beamline which makes it suitable for FLASH experiments. However, the established experimental setup uses only the entrance channel of the proton Bragg curve. In this work, a set of 3D-printed range modulators designed to generate spread out Bragg peaks (SOBPs) for radiobiological experiments at ultra-high dose rate at this beamline is described. A new method to optimize range modulators specifically for the case of a static pencil beam based on the central depth dose profile is introduced. Modulators for two different irradiation setups were produced and characterized experimentally by measurements of lateral and depth dose distributions using different detectors. In addition, Monte Carlo simulations were performed to assess profiles of the dose averaged linear energy transfer (LETD) in water. These newly produced range modulators will allow future proton FLASH experiments in the SOBP at UPTD with two different experimental setups

Study of the time and space distribution of beta+ emitters from 80 MeV/u carbon ion beam irradiation on PMMA

Proton and carbon ion therapy is an emerging technique used for the treatment of solid cancers. The monitoring of the dose delivered during such treatments and the on-line knowledge of the Bragg peak position is still a matter of research. A possible technique exploits the collinear 511\ \kilo\electronvolt photons produced by positrons annihilation from $\beta^+$ emitters created by the beam. This paper reports rate measurements of the 511\ \kilo\electronvolt photons emitted after the interactions of a 80\ \mega\electronvolt / u fully stripped carbon ion beam at the Laboratori Nazionali del Sud (LNS) of INFN, with a Poly-methyl methacrylate target. The time evolution of the $\beta^+$ rate was parametrized and the dominance of $^{11}C$ emitters over the other species ($^{13}N$, $^{15}O$, $^{14}O$) was observed, measuring the fraction of carbon ions activating $\beta^+$ emitters $A_0=(10.3\pm0.7)\cdot10^{-3}$. The average depth in the PMMA of the positron annihilation from $\beta^+$ emitters was also measured, D_{\beta^+}=5.3\pm1.1\ \milli\meter, to be compared to the expected Bragg peak depth D_{Bragg}=11.0\pm 0.5\ \milli\meter obtained from simulations

Entwicklung kompakter, gepulster Elektro-Dipolmagnete für die laserbasierte Protonentherapie

Hintergrund Die strahlentherapeutische Behandlung von Krebserkrankungen erfolgt zurzeit hauptsächlich durch eine Bestrahlung mit hochenergetischen Photonen und Elektronen aus kompakten Therapie-Linearbeschleunigern. Seltener werden auch Protonenstrahlen eingesetzt. Diese besitzen gegenüber Photonen und Elektronen vorteilhaftere physikalische und strahlenbiologische Eigenschaften, die besonders bei der Bestrahlung von tiefliegenden Tumoren in der Nähe von lebenswichtigen, strahlenempfindlichen Organen von Bedeutung sind. Die Behandlung mit Protonen erfordert jedoch sehr große und teure Bestrahlungsanlagen, weshalb es weltweit bisher nur ca. 50 solcher Anlagen an großen Zentren gibt. In den letzten Jahren wurde das völlig neuartige Prinzip der Teilchenbeschleunigung durch Hochleistungslaser soweit entwickelt, dass eine medizinische Anwendung zur Krebstherapie vorstellbar ist. Die laserbasierte Teilchenbeschleunigung verspricht deutlich kompaktere und kostengünstigere Protonenbeschleuniger, erzeugt jedoch im Unterschied zu herkömmlichen Beschleunigern sehr kurze (~ps) hochintensive Protonenpulse mit großer Strahldivergenz und breitem Energiespektrum. Im Rahmen des Verbundprojektes onCOOPtics wird die klinische Anwendbarkeit derartiger laserbeschleunigter Protonenstrahlen untersucht, was nicht nur die Entwicklung des notwendigen Laser-Teilchen-Beschleunigers, sondern auch die Entwicklung eines geeigneten Strahlführungssystems beinhaltet