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Lydia Laschinsky,
Michael Baumann,
Elke Beyreuther, Wolfgang Enghardt,
Malte Kaluza,
Leonhard Karsch,
Elisabeth Lessmann,
Doreen Naumburger,
Maria Nicolai,
Christian Richter,
Roland Sauerbrey,
Hans-Peter Schlenvoigt,
Jörg Pawelke
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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. · 1.68 Impact Factor
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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
GyE).
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. · 3.56 Impact Factor
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ABSTRACT: An independent assessment of the dose delivery in ion therapy can be performed using positron emission tomography (PET). For that a distribution of positron emitters which appear as the result of interaction between ions of the therapeutic beam and the irradiated tissue is measured during or after the irradiation. Three concepts for PET monitoring implemented in various therapy facilities are considered in this paper. The in-beam PET concept relies on the PET measurement performed simultaneously to the irradiation by means of a PET scanner which is completely integrated into the irradiation site. The in-room PET concept allows measurement immediately after irradiation by a standalone PET scanner which is installed very close to the irradiation site. In the off-line PET scenario the measurement is performed by means of a standalone PET/CT scanner 10-30 min after the irradiation. These three concepts were evaluated according to image quality criteria, integration costs, and their influence onto the workflow of radiotherapy. In-beam PET showed the best performance. However, the integration costs were estimated as very high for this modality. Moreover, the performance of in-beam PET depends heavily on type and duty cycle of the accelerator. The in-room PET is proposed for planned therapy facilities as a good compromise between the quality of measured data and integration efforts. For facilities which are close to the nuclear medicine departments off-line PET can be suggested under several circumstances.
Physics in Medicine and Biology 03/2011; 56(5):1281-98. · 2.83 Impact Factor
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Elke Beyreuther, Wolfgang Enghardt,
Malte Kaluza,
Leonhard Karsch,
Lydia Laschinsky,
Elisabeth Lessmann,
Maria Nicolai,
Jörg Pawelke,
Christian Richter,
Roland Sauerbrey,
Hans-Peter Schlenvoigt,
Michael Baumann
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ABSTRACT: Purpose: In recent years, laser-based acceleration of charged particles has rapidly progressed and medical applications, e.g. in radiotherapy, might become feasible in the coming decade. Requirements are monoenergetic particle beams with long-term stable and reproducible properties as well as sufficient particle intensities and a controlled delivery of prescribed doses at the treatment site. Although conventional and laser-based particle accelerators will administer the same dose to the patient, their different time structures could result in different radiobiological properties. Therefore, the biological response to the ultra-short pulse durations and the resulting high peak dose rates of these particle beams have to be investigated. The technical prerequisites, i.e. a suitable cell irradiation setup and the precise dosimetric characterization of a laser-based particle accelerator, have to be realized in order to prepare systematic cell irradiation experiments.
Methods: The Jena Titanium:Sapphire laser system (JETI) was customized in preparation for cell irradiation experiments with laser-accelerated electrons. The delivered electron beam was optimized with regard to its spectrum, diameter, dose rate and dose homogeneity. A custom-designed beam and dose monitoring system, consisting of a Roos ionization chamber, a Faraday cup and EBT-1 dosimetry films, enables real-time monitoring of irradiation experiments and precise determination of the dose delivered to the cells. Finally, as proof-of-principle experiment cell samples were irradiated using this setup.
Results: Laser-accelerated electron beams, appropriate for in vitro radiobiological experiments, were generated with a laser shot frequency of 2.5 Hz and a pulse length of 80 fs. After laser-acceleration in the helium gas jet, the electrons were filtered by a magnet, released from the vacuum target chamber and propagated in air for a distance of 220 mm. Within this distance a lead collimator was introduced leading, along with the optimized setup, to a beam diameter of 35 mm, sufficient for the irradiation of common cell culture vessels. The corresponding maximum dose inhomogeneity over the beam spot was less than 10 % for all irradiated samples. At cell position, the electrons posses a mean kinetic energy of 13.6 MeV, a bunch length of about 5 ps (FWHM) and a mean pulse dose of 1.6 mGy per bunch. Cross correlations show clear linear dependencies for the online recorded accumulated bunch charges, pulse doses and pulse numbers on absolute doses determined with EBT-1 films. Hence, the established monitoring system is suitable for beam control and a dedicated dose delivery. Additionally, reasonable day-to-day stable and reproducible properties of the electron beam were achieved.
Conclusions: Basic technical prerequisites for future cell irradiation experiments with ultrashort pulsed laser-accelerated electrons were established at the JETI laser system. The implemented online control system is suitable to compensate beam intensity fluctuations and the achieved accuracy of dose delivery to the cells is sufficient for radiobiological cell experiments. Hence, systematic in vitro cell irradiation experiments can be performed, being the first step towards clinical application of laser accelerated particles. Further steps, that are the transfer of the established methods to experiments on higher biological systems or to other laser-based particle accelerators, will be prepared.
Medical Physics 04/2010; 37(4):1392-1401. · 2.83 Impact Factor
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ABSTRACT: At present, in-beam positron emission tomography (PET) is the only method for in vivo and in situ range verification in ion therapy. At the GSI Helmholtzzentrum für Schwerionenforschung GmbH (GSI) Darmstadt, Germany, a unique in-beam PET installation has been operated from 1997 until the shut down of the carbon ion therapy facility in 2008. Therapeutic irradiation by means of (12)C ion beams of more than 400 patients have been monitored. In this paper a first quantitative study on the accuracy of the in-beam PET method to detect range deviations between planned and applied treatment in clinically relevant situations using simulations based on clinical data is presented. Patient treatment plans were used for performing simulations of positron emitter distributions. For each patient a range difference of + or - 6 mm in water was applied and compared to simulations without any changes. The comparisons were performed manually by six experienced evaluators for data of 81 patients. The number of patients required for the study was calculated using the outcome of a pilot study. The results indicate a sensitivity of (91 + or - 3)% and a specificity of (96 + or - 2)% for detecting an overrange, a reduced range is recognized with a sensitivity of (92 + or - 3)% and a specificity of (96 + or - 2)%. The positive and the negative predictive value of this method are 94% and 87%, respectively. The interobserver coefficient of variation is between 3 and 8%. The in-beam PET method demonstrated a high sensitivity and specificity for the detection of range deviations. As the range is a most indicative factor of deviations in the dose delivery, the promising results shown in this paper confirm the in-beam PET method as an appropriate tool for monitoring ion therapy.
Physics in Medicine and Biology 03/2010; 55(7):1989-98. · 2.83 Impact Factor
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ABSTRACT: Human tumour xenografts in a nude rat model have consistently been used as an essential part of preclinical studies for anticancer drugs activity in human. Commonly, these animals receive whole body irradiation to assure immunosuppression. But whole body dose delivery might be inhomogeneous and the resulting incomplete bone marrow depletion may modify tumour behaviour. To improve irradiation-mediated immunosuppression of human non-small cell lung cancer (NSCLC) xenografts in a nude rat model irradiation (2 + 2 Gy) from opposite sides of animals has been performed using a conventional X-ray tube. The described modification of whole body irradiation improves growth properties of human NSCLC xenografts in a nude rat model. The design of the whole body irradiation mediated immunosuppression described here for NSCLC xenografts may be useful for research applications involving other types of human tumours.
Journal of Biomedicine and Biotechnology 01/2010; 2010:580531. · 2.44 Impact Factor
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ABSTRACT: Clinically safe and effective treatment of intrafractionally moving targets with scanned ion beams requires dedicated delivery techniques such as beam tracking. Apart from treatment delivery, also appropriate methods for validation of the actual tumor irradiation are highly desirable, In this contribution the feasibility of four-dimensionally (space and time) resolved, motion-compensated in-beam positron emission tomography (4DibPET) was addressed in experimental studies with scanned carbon ion beams.
A polymethyl methracrylate block sinusoidally moving left-right in beam's eye view was used as target. Radiological depth changes were introduced by placing a stationary ramp-shaped absorber proximal of the moving target. Treatment delivery was compensated for motion by beam tracking. Time-resolved, motion-correlated in-beam PET data acquisition was performed during beam delivery with tracking the moving target and prolonged after beam delivery first with the activated target still in motion and, finally, with the target at rest. Motion-compensated 4DibPET imaging was implemented and the results were compared to a stationary reference irradiation of the same treatment field. Data were used to determine feasibility of 4DibPET but also to evaluate offline in comparison to in-beam PET acquisition.
4D in-beam as well as offline PET imaging was found to be feasible and offers the possibility to verify the correct functioning of beam tracking. Motion compensation of the imaged beta(+)-activity distribution allows recovery of the volumetric extension of the delivered field for direct comparison with the reference stationary condition. Observed differences in terms of lateral field extension and penumbra in the direction of motion were typically less than 1 mm for both imaging strategies in comparison to the corresponding reference distributions. However, in-beam imaging retained a better spatial correlation of the measured activity with the delivered dose.
4DibPET is a feasible and promising method to validate treatment delivery of scanned ion beams to moving targets. Further investigations will focus on more complex geometries and treatment planning studies with clinical data.
Medical Physics 09/2009; 36(9):4230-43. · 2.83 Impact Factor
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Bildverarbeitung für die Medizin 2009: Algorithmen - Systeme - Anwendungen, Proceedings des Workshops vom 22. bis 25. März 2009 in Heidelberg; 01/2009
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ABSTRACT: We proposed the reconstruction scheme for the subsets based RFS-EM algorithm. The scheme includes 4 iterations only, the number of subsets decreases from iteration to iteration and equals to 8, 6, 4, and 2 subsets, respectively. The images reconstructed with this scheme are of similar quality as those reconstructed with the reference 50 iterations of ML-EM. High quality of the system matrix is required for RFS-EM reconstructions of large fields.
Nuclear Science Symposium Conference Record, 2008. NSS '08. IEEE; 11/2008
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ABSTRACT: In-beam PET is a valuable method for a beam-delivery independent dose monitoring in radiation therapy with ion beams. The clinical feasibility of in-beam PET has been demonstrated for carbon and proton beams up to now. From radiobiological point of view it is highly desirable to perform tumor irradiation also with other ions. To extend the application of in-beam PET also to these ions, extensive knowledge about positron emitter production via nuclear fragmentation reactions during ion irradiation is necessary. To model the positron emitter production correctly, cross sections for all possible nuclear reactions occurring in the tissue during irradiation and leading to positron emitters are required. Since for many ions of therapeutic interest these cross sections are not available in the required energy range, a novel approach for estimating the positron emitter production from experimental data is introduced. The prediction of positron emitter distributions is based on depth dependent thick target yields, which are deduced by linear super-position of measured yields in water, graphite and polyethylene as reference materials. First results on the prediction of positron emitter distributions in polymethyl methacrylate (PMMA) targets induced by Li and C irradiation are presented. By comparison with data deduced from experiments, it is shown that a rather accurate prediction of positron emitter distribution in PMMA is possible with this method.
Nuclear Science Symposium Conference Record, 2008. NSS '08. IEEE; 11/2008
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ABSTRACT: Respiratory motion can introduce image artefacts not only in 3D PET but also in 4D PET due to incorrect attenuation correction. In this work the influence of different attenuation correction strategies on 3D and 4D PET has been investigated. An extensive phantom study was carried out, using a normal 3D CT (pitch 1.5), a slow 3D CT (pitch 0.5), an ultraslow 3D CT (pitch 0.15), an average CT and a maximum intensity projection calculated from a 4D CT (pitch 0.1) for attenuation correction of both a 3D and 4D PET of a respiratory motion phantom. Additionally, the 4D PET was corrected phase-wise with a 4D CT (phase-correlated attenuation correction). The reconstructed PET images were analyzed concerning the reconstructed volume, motion amplitude (for 4D PET), activity concentration and activity distribution. Moreover a patient study was carried out investigating the influence of the different attenuation correction strategies for 4D PET to patient data. Therefore 4D PET data from six patients with non-small cell lung cancer (NSCLC) was alternatively attenuation corrected with a normal 3D CT, an average CT and with phase-correlated attenuation correction. The tumor volume was analyzed and the motion amplitude of the tumor was obtained from the 4D PET data sets. For the phantom data the attenuation correction with the slow CT results in the best agreement between expected and measured values of the examined quantities in 3D PET, whereas in 4D PET this was the case for the phase-correlated attenuation correction. In the patient study only small differences between the 4D PET attenuation correction methods were found. This can be explained by the relative small tumor motion in the patient population investigated (peak to peak amplitude below 5 mm except for one patient).
Nuclear Science Symposium Conference Record, 2008. NSS '08. IEEE; 11/2008
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ABSTRACT: The size of image elements influences significantly the quality of the image. A small voxel size increases the resolution but produces high oscillations of a signal. Large voxels produce homogeneous images, however, with low spatial resolution. The size of the voxel is always a compromise between suppressing signal noise which requires larger voxel size, and covering small imaging details which requires smaller voxel size. For the in-beam PET scanner BASTEI the size of the voxel can be enlarged for typical irradiation fields from the standard (1.6875 mm)<sup>3</sup> to 2 × 2 × 3 mm<sup>3</sup> without compromising the image quality. The images reconstructed with larger voxel are less noisy and still contain enough information about activity in small cavities and range deviations. Reconstruction is two times faster for the 2 × 2 × 3 mm<sup>3</sup> voxel, as compared to the standard (1.6875 mm)<sup>3</sup>.
Nuclear Science Symposium Conference Record, 2008. NSS '08. IEEE; 11/2008
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ABSTRACT: The image quality in a conventional positron emission tomography (PET)/computed tomography (CT) scanner is degraded by respiratory motion because of erroneous attenuation correction when three-dimensional image acquisition is used. To overcome this problem, time-resolved data acquisition (4D) is required. For this, a Siemens Biograph 16 PET/CT scanner has been modified and its normal capability has been extended to a true 4D-PET/4D-CT imaging device including phase-correlated attenuation correction. To verify the correct functionality of this device, experiments on a respiratory motion phantom that allowed movement in two dimensions have been performed. The measurements showed good spatial correlation as well as good time synchronization between the PET and CT data. Furthermore, the motion pattern of the phantom and the shape of the activity distribution have been examined, and the volume of the reconstructed PET images has been analyzed. The results demonstrate the feasibility of such a procedure, and we therefore recommend that 4D-PET data should be reconstructed using 4D-CT data, which can be acquired on the same machine.
Physics in Medicine and Biology 08/2008; 53(13):N259-68. · 2.83 Impact Factor
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Charles Gillham,
Daniel Zips,
Falk Pönisch,
Carsten Evers, Wolfgang Enghardt,
Nasreddin Abolmaali,
Klaus Zöphel,
Steffen Appold,
Tobias Hölscher,
Jörg Steinbach,
Jörg Kotzerke,
Thomas Herrmann,
Michael Baumann
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ABSTRACT: Loco-regional failure after radiotherapy with total doses of 60-70 Gy for non-small cell lung cancer (NSCLC) remains a major clinical problem. Escalation of radiation dose is often limited because of exceeding normal tissue constraints. The present study was designed to test the hypothesis that a reduction in disease volume during radiotherapy detected by FDG PET/CT would facilitate radiation dose escalation, whilst remaining within normal tissue constraints.
Ten patients with localised inoperable NSCLC were prospectively enrolled. Each received standard 3D-conformally planned radiotherapy to a dose of 66 Gy in 33 fractions over 6.5 weeks. FDG PET/CT imaging in the treatment position was performed prior to treatment and repeated following 50 or 60 Gy. CT and PET-delineated gross tumour volumes were generated and a composite created. A margin of 15mm was added in all planes to form the planning target volume (PTV). Treatment planning was performed to compare two dose escalation strategies: 78 Gy delivered to the initial PTV with treatment in two phases (shrinking field), i.e., 66 Gy to the initial PTV with a 12 Gy-boost to the PTV after 50/60 Gy. As an alternative planning approach the maximal dose without exceeding normal tissue constraints was evaluated for each patient (individualized dose prescription).
There was a median PTV reduction after 50/60 Gy of 20%. Delivering 78 Gy to the initial PTV could have been achieved in 4/10 patients. Of the remaining 6, delivering 78 Gy to the initial PTV would have exceeded normal tissue constraints and no benefit was seen when delivered in two phases. The results from the individualized dose prescription indicated a higher median maximal dose when treatment would be given in two phases compared to one phase resulting in a modest increase of calculated tumour control probability.
Our data suggest that despite tumour shrinkage determined by subsequent FDG PET/CT during treatment the tested adaptive targeting strategy would result only in a modest improvement in the context of dose escalation. Further studies on the optimal use of FDG PET/CT and other approaches for dose escalation in loco-regionally advanced NSCLC are warranted.
Radiotherapy and Oncology 06/2008; 88(3):335-41. · 5.58 Impact Factor
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ABSTRACT: One of the long-standing problems in carbon-ion therapy is the monitoring of the treatment, i.e. of the delivered dose to a given tissue volume within the patient. Over the last 8 years, in-beam positron emission tomography (PET) has been used at the experimental carbon ion treatment facility at the Gesellschaft fur Schwerionenforschung (GSI) Darmstadt and has become a valuable quality assurance tool. In order to determine and evaluate the correct delivery of the patient dose, a simulation of the positron emitter distribution has been compared to the measurement. One particular effect is the blurring as well as the reduction of the measured activity distribution via washout. The objective of this study is the investigation of tissue dependent effective half-lives from patient data. We find no significant dependence of the effective half-life on the Hounsfield unit but on the local dose. The biological half-life within the high dose region is longer than in the low dose region. Furthermore, the influence of the overall treatment time on the kinetics of the positron emitter is reported. There are indications for a metabolic response of the tissue on the irradiation. Taking into account the biological half-life in the simulation leads to an improvement of the quality of the PET-images in some cases.
Acta oncologica (Stockholm, Sweden) 02/2008; 47(6):1077-86. · 2.27 Impact Factor
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ABSTRACT: We extrapolate the impact of recent detector and scintillator developments, enabling sub-nanosecond coincidence timing resolution (tau), onto in-beam positron emission tomography (in-beam PET) for monitoring charged-hadron radiation therapy. For tau < or = 200 ps full width at half maximum, the information given by the time-of-flight (TOF) difference between the two opposing gamma-rays enables shift-variant, artefact-free in-beam tomographic imaging by means of limited-angle, dual-head detectors. We present the corresponding fast, TOF-based and backprojection-free, 3D reconstruction algorithm that, coupled with a real-time data acquisition and a fast detector encoding scheme, allows the sampled beta+-activity to be visualized in the object during the course of the irradiation. Despite the very low statistics scenario typical of in-beam PET, real-treatment simulations show that in-beam TOF-PET enables high-precision images to be obtained in real-time, either with closed-ring or with fixed, dual-head in-beam TOF-PET systems. The latter greatly alleviates the installation of in-beam PET at radiotherapeutic sites.
Physics in Medicine and Biology 12/2007; 52(23):6795-811. · 2.83 Impact Factor
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ABSTRACT: Positron emission tomography (PET) has become a key technology for molecular imaging in clinical practice, as well as in medical, biological and pharmaceutical research. This increases the necessity for a practical introduction to PET in students with a corresponding specialization. For this purpose, the PET scanner 'PET-TW 05' was set up to demonstrate both the principles of computer tomography (CT) as well as the basics of PET. Moreover, the technical requirements and the signal processing needed for a PET system are shown in a simplified but comprehensive way. This article illustrates the layout of the tomography and provides an overview on the signal processing, as well as on the details of data acquisition and processing. The measuring procedure is described. The results for a measurement with a simple source configuration (five 22Na sources) are also presented. Finally, the characteristic parameters and the educational goals of the tomograph are summarized.
Zeitschrift für Medizinische Physik 02/2007; 17(3):212-7. · 1.21 Impact Factor
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ABSTRACT: In-beam positron emission tomography (PET) is currently used for monitoring the dose delivery at the heavy ion therapy facility at GSI Darmstadt. The method is based on the fact that carbon ions produce positron emitting isotopes in fragmentation reactions with the atomic nuclei of the tissue. The relation between dose and beta(+)-activity is not straightforward. Hence it is not possible to infer the delivered dose directly from the PET distribution. To overcome this problem and enable therapy monitoring, beta(+)-distributions are simulated on the basis of the treatment plan and compared with the measured ones. Following the positive clinical impact, it is planned to apply the method at future ion therapy facilities, where beams from protons up to oxygen nuclei will be available. A simulation code capable of handling all these ions and predicting the irradiation-induced beta(+)-activity distributions is desirable. An established and general purpose radiation transport code is preferred. FLUKA is a candidate for such a code. For application to in-beam PET therapy monitoring, the code has to model with high accuracy both the electromagnetic and nuclear interactions responsible for dose deposition and beta(+)-activity production, respectively. In this work, the electromagnetic interaction in FLUKA was adjusted to reproduce the same particle range as from the experimentally validated treatment planning software TRiP, used at GSI. Furthermore, projectile fragmentation spectra in water targets have been studied in comparison to available experimental data. Finally, cross sections for the production of the most abundant fragments have been calculated and compared to values found in the literature.
Physics in Medicine and Biology 10/2006; 51(17):4385-98. · 2.83 Impact Factor
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ABSTRACT: In-beam positron emission tomography (in-beam PET) is currently the only method for an in situ monitoring of highly tumour-conformed charged hadron therapy. At the experimental carbon ion tumour therapy facility, running at the Gesellschaft für Schwerionenforschung, Darmstadt, Germany, all treatments have been monitored by means of a specially adapted dual-head PET scanner. The positive clinical impact of this project triggered the construction of a hospital-based hadron therapy facility, with in-beam PET expected to monitor more delicate radiotherapeutic situations. Therefore, we have studied possible in-beam PET improvements by optimizing the arrangement of the gamma-ray detectors. For this, a fully 3D, rebinning-free, maximum likelihood expectation maximization algorithm applicable to several closed-ring or dual-head tomographs has been developed. The analysis of beta(+)-activity distributions simulated from real-treatment situations and detected with several detector arrangements allows us to conclude that a dual-head tomograph with narrow gaps yields in-beam PET images with sufficient quality for monitoring head and neck treatments. For monitoring larger irradiation fields, e.g. treatments in the pelvis region, a closed-ring tomograph was seen to be highly desirable. Finally, a study of the space availability for patient and bed, tomograph and beam portal proves the implementation of a closed-ring detector arrangement for in-beam PET to be feasible.
Physics in Medicine and Biology 06/2006; 51(9):2143-63. · 2.83 Impact Factor
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ABSTRACT: At the carbon ion therapy facility of GSI Darmstadt in-beam positron emission tomography (PET) is used for imaging the beta+-activity distributions which are produced via nuclear fragmentation reactions between the carbon ions and the atomic nuclei of the irradiated tissue. On the basis of these PET images the quality of the irradiation, i.e. the position of the field, the particle range in vivo and even local deviations between the planned and the applied dose distribution, can be evaluated. However, for such an evaluation the measured beta+-activity distributions have to be compared with those predicted from the treatment plan. The predictions are calculated as follows: a Monte Carlo event generator produces list mode data files of the same format as the PET scanner in order to be processed like the measured ones for tomographic reconstruction. The event generator models the whole chain from the interaction of the projectiles with the target, i.e. their stopping and nuclear reactions, the production and the decay of positron emitters, the motion of the positrons as well as the propagation and the detection of the annihilation photons. The steps of the modelling, the experimental validation and clinical implementation are presented.
Physics in Medicine and Biology 01/2005; 49(23):5217-32. · 2.83 Impact Factor
