[show abstract][hide abstract] ABSTRACT: Therapeutic irradiation with protons and ions is advantageous over radiotherapy with photons due to its favorable dose deposition. Additionally, ion beams provide a higher relative biological effectiveness than photons. For this reason, an improved treatment of deep-seated tumors is achieved and normal tissue is spared. However, small deviations from the treatment plan can have a large impact on the dose distribution. Therefore, a monitoring is required to assure the quality of the treatment. Particle therapy positron emission tomography (PT-PET) is the only clinically proven method which provides a non-invasive monitoring of dose delivery. It makes use of the β(+)-activity produced by nuclear fragmentation during irradiation. In order to evaluate these PT-PET measurements, simulations of the β(+)-activity are necessary. Therefore, it is essential to know the yields of the β(+)-emitting nuclides at every position of the beam path as exact as possible. We evaluated the three-dimensional Monte-Carlo simulation tool PHITS (version 2.30) [ 1] and the 1D deterministic simulation tool HIBRAC [ 2] with respect to the production of β(+)-emitting nuclides. The yields of the most important β(+)-emitting nuclides for carbon, lithium, helium and proton beams have been calculated. The results were then compared with experimental data obtained at GSI Helmholtzzentrum für Schwerionenforschung Darmstadt, Germany. GEANT4 simulations provide an additional benchmark [ 3]. For PHITS, the impact of different nuclear reaction models, total cross-section models and evaporation models on the β(+)-emitter production has been studied. In general, PHITS underestimates the yields of positron-emitters and cannot compete with GEANT4 so far. The β(+)-emitters calculated with an extended HIBRAC code were in good agreement with the experimental data for carbon and proton beams and comparable to the GEANT4 results, see [ 4] and Fig. 1. Considering the simulation results and its speed compared with three-dimensional Monte-Carlo tools, HIBRAC is a good candidate for the implementation in clinical routine PT-PET. Fig 1.Depth-dependent yields of the production of (11)C and (15)O during proton irradiation of a PMMA target with 140 MeV [ 4].
Journal of Radiation Research 03/2014; 55 Suppl 1:i143-i144. · 1.45 Impact Factor
[show abstract][hide abstract] ABSTRACT: Identifying those patients who have a higher chance to be cured with fewer side effects by particle beam therapy than by state-of-the-art photon therapy is essential to guarantee a fair and sufficient access to specialized radiotherapy. The individualized identification requires initiatives by particle as well as non-particle radiotherapy centers to form networks, to establish procedures for the decision process, and to implement means for the remote exchange of relevant patient information. In this work, we want to contribute a practical concept that addresses these requirements.
We proposed a concept for individualized patient allocation to photon or particle beam therapy at a non-particle radiotherapy institution that bases on remote treatment plan comparison. We translated this concept into the web-based software tool ReCompare (REmote COMparison of PARticlE and photon treatment plans).
We substantiated the feasibility of the proposed concept by demonstrating remote exchange of treatment plans between radiotherapy institutions and the direct comparison of photon and particle treatment plans in photon treatment planning systems. ReCompare worked with several tested standard treatment planning systems, ensured patient data protection, and integrated in the clinical workflow.
Our concept supports non-particle radiotherapy institutions with the patient-specific treatment decision on the optimal irradiation modality by providing expertise from a particle therapy center. The software tool ReCompare may help to improve and standardize this personalized treatment decision. It will be available from our website when proton therapy is operational at our facility.
[show abstract][hide abstract] ABSTRACT: Purpose: To investigate the possibility of detecting patient mispositioning in carbon-ion therapy with particle therapy positron emission tomography (PET) in an automated image registration based manner.Methods: Tumors in the head and neck (H&N), pelvic, lung, and brain region were investigated. Biologically optimized carbon ion treatment plans were created with TRiP98. From these treatment plans, the reference β(+)-activity distributions were calculated using a Monte Carlo simulation. Setup errors were simulated by shifting or rotating the computed tomography (CT). The expected β(+) activity was calculated for each plan with shifts. Finally, the reference particle therapy PET images were compared to the "shifted" β(+)-activity distribution simulations using the Pearson's correlation coefficient (PCC). To account for different PET monitoring options the inbeam PET was compared to three different inroom scenarios. Additionally, the dosimetric effects of the CT misalignments were investigated.Results: The automated PCC detection of patient mispositioning was possible in the investigated indications for cranio-caudal shifts of 4 mm and more, except for prostate tumors. In the rather homogeneous pelvic region, the generated β(+)-activity distribution of the reference and compared PET image were too much alike. Thus, setup errors in this region could not be detected. Regarding lung lesions the detection strongly depended on the exact tumor location: in the center of the lung tumor misalignments could be detected down to 2 mm shifts while resolving shifts of tumors close to the thoracic wall was more challenging. Rotational shifts in the H&N and lung region of +6° and more could be detected using inroom PET and partly using inbeam PET. Comparing inroom PET to inbeam PET no obvious trend was found. However, among the inroom scenarios a longer measurement time was found to be advantageous.Conclusions: This study scopes the use of various particle therapy PET verification techniques in four indications. The automated detection of patients' setup errors was investigated in a broad accumulation of data sets. The evaluation of introduced setup errors is performed automatically, which is of utmost importance to introduce highly required particle therapy monitoring devices into the clinical routine.
Medical Physics 12/2013; 40(12):121718. · 2.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: The HADES (High Acceptance Di-Electron Spectrometer) is a tool designed for lepton pair (e+e−) spectroscopy in pion, proton and heavy ion induced reactions in the 1–2AGeV energy range. One of the goals of the HADES experiment is to study in-medium modifications of hadron properties like effective masses, decay widths, electromagnetic form factors etc. Such effects can be probed with vector mesons ( ρ,ω,ɸ ) decaying into e+e− channel. The identification of vector mesons by means of a HADES spectrometer is based on invariant mass reconstruction of e+e− pairs. The combined information from all spectrometer sub-detectors is used to reconstruct the di-lepton signal. The recent results from 2.2GeV p + p, 1AGeV and 2AGeV C+C experiments are presented. Diaz Medina, Jose, Jose.Diaz@uv.es
[show abstract][hide abstract] ABSTRACT: To investigate scanned-beam proton dose distribution reproducibility in the lung under high frequency jet ventilation (HFJV).
For 11 patients (12 lesions), treated with single-fraction photon stereotactic radiosurgery under HFJV, scanned-beam proton plans were prepared with the TRiP98 treatment planning system using 2, 3-4 and 5-7 beams. The planning objective was to deliver at least 95% of the prescription of 33Gy (RBE) to 98% of the PTV. Plans were subsequently recomputed on localization CT scans. Additionally, for selected cases, the effects of range uncertainties were investigated.
Median GTV V98% was 98.7% in the original 2-field plans and 93.7% in their recomputation (p=0.039). The respective values were 99.0% and 98.0% (p=0.039) for the 3-4-field plans and 100.0% and 99.6% (p=0.125) for the 5-7-field plans. CT calibration uncertainties of ±3.5% led to a GTV V98% reduction below 1.5 percentual points in most cases and reaching 3 percentual points for 2-field plans with beam undershoot.
Through jet ventilation, reproducible tumor fixation for proton radiotherapy of lung lesions is achievable, ensuring excellent target coverage in most cases. In few cases, non-optimal patient setup reproducibility induced density changes across beam entrance channels, leading to dosimetric deterioration between planning and delivery.
Radiotherapy and Oncology 10/2013; · 4.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: For quality assurance in particle therapy, a non-invasive, in vivo range verification is highly desired. Particle therapy positron-emission-tomography (PT-PET) is the only clinically proven method up to now for this purpose. It makes use of the β(+)-activity produced during the irradiation by the nuclear fragmentation processes between the therapeutic beam and the irradiated tissue. Since a direct comparison of β(+)-activity and dose is not feasible, a simulation of the expected β(+)-activity distribution is required. For this reason it is essential to have a quantitatively reliable code for the simulation of the yields of the β(+)-emitting nuclei at every position of the beam path. In this paper results of the three-dimensional Monte-Carlo simulation codes PHITS, GEANT4, and the one-dimensional deterministic simulation code HIBRAC are compared to measurements of the yields of the most abundant β(+)-emitting nuclei for carbon, lithium, helium, and proton beams. In general, PHITS underestimates the yields of positron-emitters. With GEANT4 the overall most accurate results are obtained. HIBRAC and GEANT4 provide comparable results for carbon and proton beams. HIBRAC is considered as a good candidate for the implementation to clinical routine PT-PET.
Physics in Medicine and Biology 09/2013; 58(18):6355-6368. · 2.70 Impact Factor
[show abstract][hide abstract] ABSTRACT: Purpose: Particle Therapy Positron Emission Tomography (PT-PET) is a suitable method for verification of therapeutic dose delivery by measurements of irradiation-induced β(+)-activity. Due to metabolic processes in living tissue β(+)-emitters can be removed from the place of generation. This washout is a limiting factor for image quality. The purpose of this study is to investigate whether a washout model obtained by animal experiments is applicable to patient data.Methods: A model for the washout has been developed by Mizuno et al. [Phys. Med. Biol. 48(15), 2269-2281 (2003)] and Tomitani et al. [Phys. Med. Biol. 48(7), 875-889 (2003)]. It is based upon measurements in a rabbit in living and dead conditions. This model was modified and applied to PET data acquired during the experimental therapy project at GSI Helmholtzzentrum für Schwerionenforschung Darmstadt, Germany. Three components are expected: A fast one with a half life of 2 s, a medium one in the range of 2-3 min, and a slow component of the order of 2-3 h. Ten patients were selected randomly for investigation of the fast component. To analyze the other two components, 12 one-of-a-kind measurements from a single volunteer patient are available.Results: A fast washout on the time scale of a few seconds was not observed in the patient data. The medium processes showed a mean half life of 155.7 ± 4.6 s. This is in the expected range. Fractions of the activity not influenced by the washout were found.Conclusions: On the time scale of an in-beam or in-room measurement only the medium-time washout processes play a remarkable role. A slow component may be neglected if the measurements do not exceed 20 min after the end of the irradiation. The fast component is not observed due to the low relative blood filled volume in the brain.
Medical Physics 09/2013; 40(9):091918. · 2.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: In-beam positron emission tomography (PET) has been proven to be a reliable technique in ion beam radiotherapy for the in situ and non-invasive evaluation of the correct dose deposition in static tumour entities. In the presence of intra-fractional target motion an appropriate time-resolved (four-dimensional, 4D) reconstruction algorithm has to be used to avoid reconstructed activity distributions suffering from motion-related blurring artefacts and to allow for a dedicated dose monitoring. Four-dimensional reconstruction algorithms from diagnostic PET imaging that can properly handle the typically low counting statistics of in-beam PET data have been adapted and optimized for the characteristics of the double-head PET scanner BASTEI installed at GSI Helmholtzzentrum Darmstadt, Germany (GSI). Systematic investigations with moving radioactive sources demonstrate the more effective reduction of motion artefacts by applying a 4D maximum likelihood expectation maximization (MLEM) algorithm instead of the retrospective co-registration of phasewise reconstructed quasi-static activity distributions. Further 4D MLEM results are presented from in-beam PET measurements of irradiated moving phantoms which verify the accessibility of relevant parameters for the dose monitoring of intra-fractionally moving targets. From in-beam PET listmode data sets acquired together with a motion surrogate signal, valuable images can be generated by the 4D MLEM reconstruction for different motion patterns and motion-compensated beam delivery techniques.
Physics in Medicine and Biology 07/2013; 58(15):5085-5111. · 2.70 Impact Factor
[show abstract][hide abstract] ABSTRACT: Particle therapy positron emission tomography (PT-PET) allows for an in vivo and in situ verification of applied dose distributions in ion beam therapy. Since the dose distribution cannot be extracted directly from the β(+)-activity distribution gained from the PET scan the validation is done by means of a comparison between the reconstructed β(+)-activity distributions from a PT-PET measurement and from a PT-PET simulation. Thus, the simulation software for generating PET data predicted from the treatment planning is an essential part of the dose verification routine. For the dose monitoring of intra-fractionally moving target volumes the PET data simulation needs to be upgraded by using time resolved (4D) algorithms to account correctly for the motion dependent displacement of the positron emitters. Moreover, it has to consider the time dependent relative movement between target volume and scanned beam to simulate the accurate positron emitter distribution generated during irradiation. Such a simulation program is presented which properly proceeds with motion compensated dose delivery by scanned ion beams to intra-fractionally moving targets. By means of a preclinical phantom study it is demonstrated that even the sophisticated motion-mitigated beam delivery technique of range compensated target tracking can be handled correctly by this simulation code. The new program is widely based on the 3D PT-PET simulation program which had been developed at the Helmholtz-Zentrum Dresden-Rossendorf, Germany (HZDR) for application within a pilot project to simulate in-beam PET data for about 440 patients with static tumor entities irradiated at the former treatment facility of the GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany (GSI). A simulation example for a phantom geometry irradiated with a tracked (12)C-ion beam is presented for demonstrating the proper functionality of the program.
Physics in Medicine and Biology 01/2013; 58(3):513-533. · 2.70 Impact Factor
[show abstract][hide abstract] ABSTRACT: Purpose: Positron emission tomography (PET) is considered to be the state of the art technique to monitor particle therapy in vivo. To evaluate the beam delivery the measured PET image is compared to a predicted β(+)-distribution. Nowadays the range assessment is performed by a group of experts via visual inspection. This procedure is rather time consuming and requires well trained personnel. In this study an approach is presented to support human decisions in an automated and objective way.Methods: The automated comparison presented uses statistical measures, namely, Pearson's correlation coefficient (PCC), to detect ion beam range deviations. The study is based on 12 in-beam PET patient data sets recorded at GSI and 70 artificial beam range modifications per data set. The range modifications were 0, 4, 6, and 10 mm water equivalent path length (WEPL) in positive and negative beam directions. The reference image to calculate the PCC was both an unmodified simulation of the activity distribution (Test 1) and a measured in-beam PET image (Test 2). Based on the PCCs sensitivity and specificity were calculated. Additionally the difference between modified and unmodified data sets was investigated using the Wilcoxon rank sum test.Results: In Test 1 a sensitivity and specificity over 90% was reached for detecting modifications of ±10 and ±6 mm WEPL. Regarding Test 2 a sensitivity and specificity above 80% was obtained for modifications of ±10 and -6 mm WEPL. The limitation of the method was around 4 mm WEPL.Conclusions: The results demonstrate that the automated comparison using PCC provides similar results in terms of sensitivity and specificity compared to visual inspections of in-beam PET data. Hence the method presented in this study is a promising and effective approach to improve the efficiency in the clinical workflow in terms of particle therapy monitoring by means of PET.
Medical Physics 10/2012; 39(10):5874-81. · 2.91 Impact Factor
[show abstract][hide abstract] ABSTRACT: The notable progress in laser particle acceleration technology promises potential medical application in cancer therapy through compact and cost effective laser devices that are suitable for already existing clinics. Previously, consequences on the radiobiological response by laser driven particle beams characterised by an ultra high peak dose rate have to be investigated. Therefore, tumour and non-malignant cells were irradiated with pulsed laser accelerated electrons at the JETI facility for the comparison with continuous electrons of a conventional therapy LINAC. Dose response curves were measured for the biological endpoints clonogenic survival and residual DNA double strand breaks. The overall results show no significant differences in radiobiological response for in vitro cell experiments between laser accelerated pulsed and clinical used electron beams. These first systematic in vitro cell response studies with precise dosimetry to laser driven electron beams represent a first step toward the long term aim of the application of laser accelerated particles in radiotherapy.
Journal of Radiation Research 06/2012; 53(3):395-403. · 1.45 Impact Factor
[show abstract][hide abstract] ABSTRACT: Strahlenbiologische und medizinphysikalische Untersuchungen versprechen Vorteile bei der Patientenbestrahlung mit schweren
Ionen. Die vorliegende Arbeit berichtet über die ersten klinischen Ergebnisse bei 45 Patienten mit Schädelbasistumoren, die
zwischen Dezember 1997 und September 1999 am Schwerionensynchroton der Gesellschaft für Schwerionenforschung (GSI), Darmstadt,
mit Kohlenstoffionen bestrahlt wurden.
Patienten und Methode: Die Patienten (23 Frauen, 22 Männer) waren im Mittel 48 (18 bis 80) Jahre alt und litten an Chordomen (17), Chondrosarkomen
(zehn) und anderen Tumoren der Schädelbasis. Erstmalig kamen das intensitätsmodulierte Rasterscan-Verfahren und die Online-Therapiekontrolle
mittels Positronenmissionstomographie am Patienten zum Einsatz. Computertomographische Aufnahmen waren Grundlage für die dreidimensionale
Strahlentherapieplanung. Patienten mit Chordomen und Chondrosarkomen erhielten eine fraktionierte Bestrahlung mit Kohlenstoffionen
(mediane Gesamtdosis 60 GyE) an 20 konsekutiven Tagen. Bei den anderen Tumorhistologien wurde nach fraktionierter stereotaktischer
Radiotherapie ein Kohlenstoffionenboost von 15 bis 18 GyE auf den makroskopischen Tumor appliziert (mediane gesamtdosis 63
Ergebnisse: Der mittlere Nachbeobachtungszeitraum betrug neun Monate. Die Bestrahlung wurde gut toleriert. Die lokale Kontrollrate über
alle Histologien hinweg lag nach einem Jahr bei 94%. Zur partiellen Tumorremission kam es bei sieben Patienten (15,5%). Ein
Patient (2,2%) ist verstorben. Es wurden bei keinem Patienten schwere radiogene Nebenwirkungen (> II° Common Toxicity Criteria)
beobachtet. Bislang ist bei keinem Patienten ein Rezidiv im Behandlungsvolumen aufgetreten.
Schlussfolgerung: Die klinische Wirksamkeit und die technische Durchführbarkeit diese neuen Therapieverfahrens konnten eindeutig belegt werden.
Um den klinische Stellenwert der Bestrahlungsmodalitäten mit Protonen und Ionen weiter zu beleuchten, sind Untersuchungen
mit größeren Patientenzahlen notwendig. Als konsequente Fortführung des Projektes ist der Bau eines ausschließlich klinisch
genutzten Teilchenbeschleunigers in Heidelberg geplant.
Radiobiological and physical examinations suggest clinical advantages of heavy ion irradiation. We report the result of 23
women and 22 men (median age 48 years) with skull base tumors irradiated with carbon ion beams at the Gesellschaft für Schwerionenforschung
(GSI), Darmstadt, from December 1997 until September 1999.
Patients and Methods: The study included patients with chordomas (17), chondrosarcomas (10) and other skull base tumors (Table 1). It is the first
time that the intensity-controlled rasterscan-technique and the application of positron-emission tomography (PET) for quality
assurance was used. All patients had computed tomography for three-dimensional-treatment planning (Figure 1). Patients with
chordomas and chondrosarcomas underwent fractionated carbon ion irradiation in 20 consecutive days (median total dose 60 GyE).
Other histologies were treated with carbon ion boost of 15 to 18 GyE delivered to the macroscopeic tumor after fractionated
stereotatic radiotherapy (median total dose 63 GyE).
Results: Mean follow-up was 9 months. Irradiation was well tolerated by all patients. Partial tumor remission was seen in 7 patients
(15,5%) (Figure 2). One-year local control rate was 94%. One patient (2,2%) deceased. No severe toxicity and no local recurrence
within the treated volume were observed.
Conclusion Clinical effectiveness and technical feasibility of this modality could clearly be demonstrated in our study. To evaluate
the clinical relevance of the different beam modalities studies with larger patient numbers are necessary. To continue our
project a new heavy ion acclerator exclusively for clinical use is planed to be constructed in Heidelberg.
Schlüsselwörter: Schädelbasis–Kohlenstoffionen–Schwerionentherapie–Strahlentherapie–GSIKey Words: Skull base–Carbon ion–Heavy ion Therapy–Radiotherapy–GSI
Strahlentherapie und Onkologie 04/2012; 176(5):211-216. · 4.16 Impact Factor
[show abstract][hide abstract] ABSTRACT: In-beam PET is a clinically proven method for monitoring ion beam cancer treatment. The objective is predominantly the verification of the range of the primary particles. Due to different processes leading to dose and activity, evaluation is done by comparing measured data to simulated. Up to now, the comparison is performed by well-trained observers (clinicians, physicists). This process is very time consuming and low in reproducibility. However, an automatic method is desirable. A one-dimensional algorithm for range comparison has been enhanced and extended to three dimensions. System-inherent uncertainties are handled by means of a statistical approach. To test the method, a set of data was prepared. Distributions of β(+)-activity calculated from treatment plans were compared to measurements performed in the framework of the German Heavy Ion Tumor Therapy Project at GSI Helmholtz Centre for Heavy Ion Research, Darmstadt, Germany. Artificial range deviations in the simulations served as test objects for the algorithm. Range modifications of different depth (4, 6 and 10 mm water equivalent path length) can be detected. Even though the sensitivity and specificity of a visual evaluation are higher, the method is feasible as the basis for the selection of patients from the data pool for retrospective evaluation of treatment and treatment plans and correlation with follow-up data. Furthermore, it can be used for the development of an assistance tool for a clinical application.
Physics in Medicine and Biology 03/2012; 57(5):1387-97. · 2.70 Impact Factor
[show abstract][hide abstract] ABSTRACT: Recent experiments in the Trident laser facility (Los Alamos National Laboratory) have shown that hollow conical targets with a flat top at the tip can enhance the maximum energy of proton beams created during the interaction of an ultra-intense short laser pulse with the target (Gaillard S A et al 2011 Phys. Plasmas 18 056710). The proton energies that have been seen in these experiments are the highest energies observed so far in laser-driven proton acceleration. This is attributed to a new acceleration mechanism, direct light pressure acceleration of electrons (DLLPA), which increases the number and energy of hot electrons that drive the proton acceleration. This acceleration process of protons due to a two-temperature sheath formed at the flat-top rear side is very robust and produces a large number of protons per shot, similar to what is regularly observed in target normal sheath acceleration (Hatchett S P et al 2000 Phys. Plasmas 7 2076, Maksimchuk A et al 2000 Phys. Rev. Lett. 84 4108, Snavely R A et al 2000 Phys. Rev. Lett. 85 2945) with flat foils. In this paper, we investigate the electron kinetics during DLLPA, showing that they are governed by two mechanisms, both of which lead to continuous electron acceleration along the inner cone wall. Based on our model, we predict the scaling of the hot electron temperature and ion maximum energy with both laser and target geometrical parameters. The scaling of T-DLLPA(hot) = m(e)c(0)(2)a(0)(2)/4 with the laser strength parameter a(0) leads to an ion energy scaling that surpasses that of some recently proposed acceleration mechanisms such as radiation pressure acceleration (RPA), while in addition the maximum electron energy is found to scale linearly with the length of the cone neck. We find that when optimizing parameters, high proton energies suitable for applications can be reached using compact short- pulse laser systems with pulse durations of only a few tens to hundreds of laser periods.
New Journal of Physics 02/2012; 14:21. · 4.06 Impact Factor
[show abstract][hide abstract] ABSTRACT: Therapeutic irradiation with ions and protons is superior to a treatment with gammas with respect to tumour conformity of dose and damage of normal tissue. On the other hand, mispositioning of the patient or density changes in the treated volume may easily compromise the success of treatment. For this reason, non-invasive, in-situ dose verification is necessary. The only clinically proven method up to now is Positron Emission Tomography [Eng04]. This method does not allow direct dose quantification due to limited angle artefacts and washout in the patient. Another promising approach is in-beam SPECT: the detection of prompt gamma-rays following nuclear interaction between the ions and the atoms of the penetrated tissue. Detection systems based on Compton-scattering and pair-conversion are now under investigation. So far, Compton-cameras have been used for diagnostic imaging in nuclear medicine and astronomy. In telescopes also pair-creation cameras are established [Zog04]. In contrast to this, in-beam dose verification systems have to manage the specific energy range and low count rates due to the patient dose. A prototype of a Compton-camera is under construction at OncoRay [Kor10, Fie11, Kor11]. It consists of a scatter layer made from CZT and an absorption layer (LSO). From the energy deposited in the detector planes a cone surface of all possible directions of the incident photon can be reconstructed [Sch11]. The expected energy distribution of the prompt gammas is calculated by means of simulations based on treatment plan data [Fie11]. To optimize the setup simulations are required. Therefore, the Monte-Carlo framework GEANT4 is used for: (1) Analysis of the efficiency in dependence of the geometry; (2) Study of background caused by backscattered photons and other secondary particles; (3) Development of filters for event selection; (4) Study parameters influencing the spatial resolution of the reconstructed image (multiple Compton-scattering inside a detector layer, escape of energy, intrinsic radioactivity of the detector material, Doppler-broadening); (5) Creation of test data sets as input for the reconstruction. For photon energies above 7 MeV the pair production is the dominant electromagnetic process in CZT. To use these events the Compton-camera might be combined with a pair-conversion camera by adding thin silicon layers in between to track the path of the electron and the positron produced during pair conversion. Exploiting this information the direction of the incident photon can be deduced. Unfortunately, the angular resolution is heavily degraded especially for photons with rather low incident energies by small-angle scattering of the secondary particles and by the recoil of the nuclei when a pair production takes place [Gol11]. Both effects were studied whereas the latter is not included in the GEANT4 code version 9.3. This simulation serves as basis for the development of an iterative reconstruction algorithm dedicated to in-beam SPECT with a pair production camera. Apart from the analysis of efficiency, angular resolution and noise, the combination of a pair production and a Compton-camera is a challenging task. Results on simulations for optimizing the setup and the refinement of the reconstruction algorithm for a clinical dose verification system will be presented. [Eng04] W. Enghardt et al., Nucl. Instr. and Meth. A 525 (2004) [Fie11] F. Fiedler et al., Nucl. Sci. Symp. IEEE (2011), accepted [Gol11] C. Golnik et al., Nucl. Sci. Symp. IEEE (2011), accepted [Kor10] T. Kormoll et al., Nucl. Instr. and Meth. A (2010) [Kor11] T. Kormoll et al., Nucl. Sci. Symp. IEEE (2011), accepted [Ric10] M.-H. Richard et al., IEEE Transactions on Nuclear Science (2010) [Sch11] S. Schöne et al., Proc. Fully 3D Meeting (2011) [Zog04] A. Zoglauer et al., Nucl. Sci. Symp. Conf. Rec. IEEE (2004)
[show abstract][hide abstract] ABSTRACT: Proton beams are a promising tool for the improvement of radiotherapy of cancer, and compact laser-driven proton radiation (LDPR) is discussed as an alternative to established large-scale technology facilitating wider clinical use. Yet, clinical use of LDPR requires substantial development in reliable beam generation and transport, but also in dosimetric protocols as well as validation in radiobiological studies. Here, we present the first dose-controlled direct comparison of the radiobiological effectiveness of intense proton pulses from a laser-driven accelerator with conventionally generated continuous proton beams, demonstrating a first milestone in translational research. Controlled dose delivery, precisely online and offline monitored for each out of ∼4,000 pulses, resulted in an unprecedented relative dose uncertainty of below 10 %, using approaches scalable to the next translational step toward radiotherapy application.
[show abstract][hide abstract] ABSTRACT: Positron emission tomography (PET) is a dedicated tool for quality assurance in ion beam therapy. By measuring the spatial distribution of positron emitters generated via nuclear interactions between projectiles and atomic nuclei of the tissue during the therapeutic irradiation, conclusions on the accuracy of the dose localization can be drawn. In the following, the physical background as well as the technical realization of PET is depicted. Furthermore, current PET installations for quality assurance of proton and ion beam therapy are presented.