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ABSTRACT: Despite enormous efforts to improve therapeutic strategies for patients with advanced ovarian carcinoma, outcome remains poor even with the advent cisplatinum-based chemotherapy regimen or taxanes with over 70% of patients developing local failure. Several trials were able to establish the potential benefit of adjuvant whole abdominal RT (WAI) though at the cost of sometimes marked side-effects. New technologies like IMRT have the potential of sparing normal tissues thus also potentially limiting treatment-related toxicity, hence a phase I trial was initiated to evaluate potential clinical benefit of WAI with IMRT. We intended to demonstrate that whole-abdominal IMRT is feasible and can be used in a routine clinical setting.
A water-equivalent phantom containing OARs was created simulating organ shape of the upper abdomen to investigate the necessary number of beams for the upper abdominal target irrespective of the number of segments and hence treatment times. We prescribed a total dose of 30 Gy in 1.5 Gy fractions to the median of the target. IMRT treatment plans for three patients with advanced ovarian cancer were created using 2 isocentres and between 12 and 14 beams while restricting the number of segments so as to restrict treatment times to less than 45 min. Dose to OARs such as kidneys and liver was strictly limited even below established maxima.
In the phantom plans, no clear indication as to the optimum number of beams could be shown though there seems to be a slight trend toward a higher number of beams yielding better results. Examples demonstrating clinically inacceptable dose distributions for plans using only 9 beams. Acceptable treatment plans for real patients could be achieved using 12-14 beams and 2 isocentres. Treatment plans consisted of 264-286 segments resulting in an overall treatment time of approximately 37-45 min. Mean doses to the kidneys could be limited to 29.3% [23.1-33.2%] (right), and 26.8% [21-30.4%] (left). 50% of the liver received less than 72.4% [61-83%].
IMRT for whole abdominal irradiation in patients with advanced ovarian carcinoma is applicable and feasible though treatment planning is complex and time-consuming. There is a significant reduction of dose to critical organs by using IMRT while maintaining target volume coverage.
Physica Medica 01/2011; 27(4):194-202. · 1.07 Impact Factor
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ABSTRACT: Respiratory motion limits the potential of modern high-precision radiotherapy techniques such as IMRT and particle therapy. Due to the uncertainty of tumour localization, the ability of achieving dose conformation often cannot be exploited sufficiently, especially in the case of lung tumours. Various methods have been proposed to track the position of tumours using external signals, e.g. with the help of a respiratory belt or by observing external markers. Retrospectively gated time-resolved x-ray computed tomography (4D CT) studies prior to therapy can be used to register the external signals with the tumour motion. However, during treatment the actual motion of internal structures may be different. Direct control of tissue motion by online imaging during treatment promises more precise information. On the other hand, it is more complex, since a larger amount of data must be processed in order to determine the motion. Three major questions arise from this issue. Firstly, can the motion that has occurred be precisely determined in the images? Secondly, how large must, respectively how small can, the observed region be chosen to get a reliable signal? Finally, is it possible to predict the proximate tumour location within sufficiently short acquisition times to make this information available for gating irradiation? Based on multiple studies on a porcine lung phantom, we have tried to examine these questions carefully. We found a basic characteristic of the breathing cycle in images using the image similarity method normalized mutual information. Moreover, we examined the performance of the calculations and proposed an image-based gating technique. In this paper, we present the results and validation performed with a real patient data set. This allows for the conclusion that it is possible to build up a gating system based on image data, solely, or (at least in avoidance of an exceeding exposure dose) to verify gates proposed by the various external systems.
Physics in Medicine and Biology 07/2008; 53(12):3129-45. · 2.83 Impact Factor
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ASTRO 49th Annual Meeting; 01/2007
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International Journal of Radiation OncologyBiologyPhysics 01/2007; 69:371-372. · 4.11 Impact Factor
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ABSTRACT: Image registration has many medical applications in diagnosis, therapy planning and therapy. Especially for time-adaptive radiotherapy, an efficient and accurate elastic registration of images acquired for treatment planning, and at the time of the actual treatment, is highly desirable. Therefore, we developed a fully automatic and fast block matching algorithm which identifies a set of anatomical landmarks in a 3D CT dataset and relocates them in another CT dataset by maximization of local correlation coefficients in the frequency domain. To transform the complete dataset, a smooth interpolation between the landmarks is calculated by modified thin-plate splines with local impact. The concept of the algorithm allows separate processing of image discontinuities like temporally changing air cavities in the intestinal track or rectum. The result is a fully transformed 3D planning dataset (planning CT as well as delineations of tumour and organs at risk) to a verification CT, allowing evaluation and, if necessary, changes of the treatment plan based on the current patient anatomy without time-consuming manual re-contouring. Typically the total calculation time is less than 5 min, which allows the use of the registration tool between acquiring the verification images and delivering the dose fraction for online corrections. We present verifications of the algorithm for five different patient datasets with different tumour locations (prostate, paraspinal and head-and-neck) by comparing the results with manually selected landmarks, visual assessment and consistency testing. It turns out that the mean error of the registration is better than the voxel resolution (2 x 2 x 3 mm(3)). In conclusion, we present an algorithm for fully automatic elastic image registration that is precise and fast enough for online corrections in an adaptive fractionated radiation treatment course.
Physics in Medicine and Biology 11/2006; 51(19):4789-806. · 2.83 Impact Factor
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ABSTRACT: Modern radiotherapy techniques such as intensity modulation are capable of generating complex dose distributions whose high dose areas tightly conform to the tumour target volume, sparing critical organs even when they are located in close proximity. This potential can only be exploited to its full extent when the accumulated dose actually delivered over the complete treatment course is sufficiently close to the dose computed on the initial CT scan used for treatment planning. Exact patient repositioning is mandatory, but also other sources of error, e.g. changes of the patient's anatomy under therapy, should be taken into account. At the German Cancer Research Center, we use a combination of a linear accelerator and a CT scanner installed in one room and sharing the same couch. It allows the quantification and correction of interfractional variations between planning and treatment delivery. In this paper, we describe treatments of prostate, paraspinal and head and neck tumours. All patients were immobilized by customized fixation devices and treated in a stereotactic setup. For each patient, frequent CT scans were taken during the treatment course. Each scan was compared with the original planning CT using manual checks and automatic rigid matching algorithms. Depending on the individual case, the adaptation to variations was carried out offline after several fractions or in real-time between the CT scan and linac irradiation. We discuss the techniques for detecting and correcting interfractional errors and outline the procedural steps of a linac-CT scanner-supported radiation treatment course.
The British journal of radiology 10/2006; 79 Spec No 1:S79-86. · 2.11 Impact Factor
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ABSTRACT: Planning of radiotherapy is often difficult due to restrictions on morphological images. New imaging techniques enable the integration of biological information into treatment planning and help to improve the detection of vital and aggressive tumour areas. This might improve clinical outcome. However, nowadays morphological data sets are still the gold standard in the planning of radiotherapy. In this paper, we introduce an in-house software platform enabling us to combine images from different imaging modalities yielding biological and morphological information in a workflow driven approach. This is demonstrated for the combination of morphological CT, MRI, functional DCE-MRI and PET data. Data of patients with a tumour of the prostate and with a meningioma were examined with DCE-MRI by applying pharmacokinetic two-compartment models for post-processing. The results were compared with the clinical plans for radiation therapy. Generated parameter maps give additional information about tumour spread, which can be incorporated in the definition of safety margins.
Physics in Medicine and Biology 10/2005; 50(17):4209-23. · 2.83 Impact Factor
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ABSTRACT: A new real-time dose calculation and visualization was developed as part of the new 3D treatment planning tool OCTOPUS for proton therapy of ocular tumours within a national research project together with the Hahn-Meitner Institut Berlin. The implementation resolves the common separation between parameter definition, dose calculation and evaluation and allows a direct examination of the expected dose distribution while adjusting the treatment parameters. The new tool allows the therapist to move the desired dose distribution under visual control in 3D to the appropriate place. The visualization of the resulting dose distribution as a 3D surface model, on any 2D slice or on the surface of specified ocular structures is done automatically when adapting parameters during the planning process. In addition, approximate dose volume histograms may be calculated with little extra time. The dose distribution is calculated and visualized in 200 ms with an accuracy of 6% for the 3D isodose surfaces and 8% for other objects. This paper discusses the advantages and limitations of this new approach.
Physics in Medicine and Biology 04/2001; 46(3):671-86. · 2.83 Impact Factor
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ABSTRACT: The intraoperative shift of neuroanatomical landmarks that serve as reference points is an unsolved problem in current neuronavigation. Monitoring the position of these landmarks requires repeated intraoperative imaging. We analyzed the effectiveness of a 3-D ultrasound system for imaging through a bore-hole trepanation. A tissue-mimicking ultrasound phantom and plastic pads with bore-holes were utilized for in vitro tests of the system. Reducing the diameter of the simulated bore-hole decreased the image quality and reduced the field of view. The multiple plane mode of the 3-D ultrasound system allows reconstruction of images in arbitrary imaging planes on the basis of intraoperatively acquired 3-D datasets. Selecting planes that are coplanar with preoperative MRI scans, we were able to identify neuroanatomical landmarks in the reconstructed ultrasound images. Repeated 3-D ultrasound during a procedure might, therefore, allow recognition of a shift of these landmarks.
Ultrasound in Medicine & Biology 07/1998; 24(5):663-71. · 2.29 Impact Factor
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ABSTRACT: Three-dimensional inverse treatment planning with modulated beams was applied for dosimetric optimization of a lengthy (22 cm) and complex (concave-convex) shaped planning target volume (PTV) in the cervical and upper mediastinal regions.
The planning was done for 9 coplanar beams spaced evenly at 40 intervals. Properties of 15 MV photons from a linear accelerator were simulated. The optimization of the fluence modulation profiles for each beam was based on a definition of the desired/permitted relative dose levels in the PTV and organs at risk, and a definition of the strengths of the constraints to achieve these objectives.
An adequate dose delivery to the PTV and protection of the spinal cord are completely achievable. The dose delivered to the lungs is clinically acceptable with respect to the risk of radiation-induced pneumonitis. For reasons of physics, no further decrease in the radiation burden on the lungs can be attained with X-rays without compromising the PTV coverage. The radiation burden on some critical part of normal tissues was effectively reduced by application of a dummy organ at risk.
The inverse planning is an effective method for conformal radiotherapy of large tumors as well. However, the power of the technique is insufficient when the tolerance dose of the neighbouring normal tissue is too low and its volume effect is high. Although requiring further operator interactions, introduction of dummy organs at risk may be of help in reducing the radiation burden on normal tissues.
Strahlentherapie und Onkologie 05/1997; 173(4):193-200. · 3.56 Impact Factor
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ABSTRACT: AimThree-dimensional inverse treatment planning with modulated beams was applied for dosimetric optimization of a lengthy (22
cm) and complex (concave-convex) shaped planning target volume (PTV) in the cervical and upper mediastinal regions.
Material and MethodThe planning was done for 9 coplanar beams spaced evenly at 40° intervals. Properties of 15 MV photons from a linear accelerator
were simulated. The optimization of the fluence modulation profiles for each beam was based on a definition of the desired/permitted
relative dose levels in the PTV and organs at risk, and a definition of the strengths of the constraints to achieve these
objectives.
ResultsAn adequate dose delivery to the PTV and protection of the spinal cord are completely achievable. The dose delivered to the
lungs is clinically acceptable with respect to the risk of radiation-induced pneumonitis. For reasons of physics, no further
decrease in the radiation burden on the lungs can be attained with X-rays without compromising the PTV coverage. The radiation
burden on some critical part of normal tissues was effectively reduced by application of a dummy organ at risk.
ConclusionThe inverse planning is an effective method for conformal radiotherapy of large tumors as well. However, the power of the
technique is insufficient when the tolerance dose of the neighbouring normal tissue is too low and its volume effect is high.
Although requiring further operator interactions, introduction of dummy organs at risk may be of help in reducing the radiation
burden on normal tissues.
ZielDie dreidimensionale inverse Bestrahlungsplanung mit einem intensitätsmodulierten Strahl wurde zur Optimierung der Dosisverteilung
eingesetzt. Dieses Verfahren wurde bei einem länglichen (22 cm) und komplex (konvex-konkav) geformten Planungszielvolumen
(PTV) im Halsbereich und im oberen Mediastinum angewandt.
Material und MethodeDie Bestrahlungsplanung erfolgte für neun koplanare Felder, die gleichmäßig im 40°-Winkelabstand angeordnet waren. Zur Simulation
wurden 15-MV-Photonen eines Linearbeschleunigers angenommen. Die Optimierung der Modulationsprofile für jedes Feld erfolgte
aufgrund der Vorgabe der gewünschten bzw. erlaubten Dosis im Planungszielvolumen und den Risikoorganen sowie der Definition
der Randbedingungen, um diese Ziele zu erreichen.
ErgebnisseEs ist möglich, eine adäquate Dosis im PTV bei ausreichendem Schutz des Rückenmarks zu applizieren. Die Bestrahlungsdosis
im Bereich der Lunge ist klinisch annehmbar unter Berücksichtigung des Risikos einer radiogenen Pneumonitis. Aus physikalischen
Gründen kann keine weitere Reduktion der Strahlenbelastung der Lungen erreicht werden, ohne daß Kompromisse hinsichtlich der
Erfassung des PTV zu akzeptieren sind. Die Strahlenbelastung einiger empfindlicher Teile des Normalgewebes konnte durch die
Anwendung eines “dummy organ at risk” deutlich reduziert werden.
SchlußfolgerungDie inverse Bestrahlungsplanung ist eine wirkungsvolle Methode zur konformierenden Bestrahlungsplanung auch großvolumiger
Tumoren. Jedoch sind die Ergebnisse dieser Technik unbefriedigend, wenn die Toleranzdosis der benachbarten Organe zu niedrig
und der Volumeneffekt groß ist. Die Einführung von “dummy organ at risk” könnte hilfreich sein, um die Strahlenbelastung des
Normalgewebes zu reduzieren, auch wenn damit die Bestrahlungsplanung aufwendiger wird.
Strahlentherapie und Onkologie 04/1997; 173(4):193-200. · 3.56 Impact Factor
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ABSTRACT: A treatment planning system for stereotactical neurosurgery has been developed. A modular system has been designed which is readily extendable. Different modalities of tomography (CT, MRI) can be correlated and presented simultaneously in transverse, frontal and sagittal reconstructions. The volumes of interest are segmented with respect to the different modalities, and the positions of the catheters are defined. The calculation of dose must be adapted to the physical requirements of the therapy and is designed as an independent process. The calculated data are shown in various presentations. The treatment planning system is applied to intratumoral chemotherapy. The drug is encapsulated in small carriers for prolonged release and injected via catheters directly into the tumor interstitium, bypassing the blood-brain barrier. The dose is calculated using the time-dependent, three-dimensional finite elements method. To achieve homogeneous temporal and spatial drug distribution it is necessary to use a great number of catheters due to the limited diffusion of drug, which is not practical in neurosurgery. Therefore this therapy concept is useful for small volumes only. Interstitial hyperthermia and brachytherapy, in contrast to intratumoral chemotherapy, show successful clinical results.
Der Radiologe 10/1996; 36(9):737-43. · 0.61 Impact Factor
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ABSTRACT: In dieser Arbeit wird ein Therapieplanungssystem für stereotaktische Anwendungen in der Neurochirurgie vorgestellt. Das Planungssystem
ist als ein modulares, leicht erweiterbares Programmpaket realisiert, mit dem man Tomographieaufnahmen verschiedener Modalitäten
(CT, MRT) korreliert und darstellt, Tumor und Risikoorgane segmentiert und Katheterpositionen definiert. Für unterschiedliche
Therapieformen wie interstitielle Hyperthermie, intratumorale Chemotherapie oder Brachytherapie sind die Dosisberechnungen
als ein eigenständiges Programm konzipiert worden. Die berechneten Ergebnisse werden in verschiedenen Darstellungen präsentiert.
Eine Anwendung für das Therapieplanungssystem ist die intratumorale Chemotherapie. Bei dieser Therapie ist der Wirkstoff in
Carrier verkapselt und wird über Katheter direkt in das Tumorgewebe appliziert. Die Dosisberechnung erfolgt mit der zeitabhängigen,
dreidimensionalen Finite-Elemente-Methode. Die zeitliche und räumliche Darstellung der Wirkstoffverteilung zeigt, daß die
intratumorale Chemotherapie aufgrund der großen Zahl an Kathetern nicht bei größeren Tumoren anwendbar ist. Im Gegensatz dazu
zeigt die interstitielle Hyperthermie und die Brachytherapie auch bei größeren Tumoren gute klinische Ergebnisse.
A treatment planning system for stereotactical neurosurgery has been developed. A modular system has been designed which is
readily extendable. Different modalities of tomography (CT, MRI) can be correlated and presented simultaneously in transverse,
frontal and sagittal reconstructions. The volumes of interest are segmented with respect to the different modalities, and
the positions of the catheters are defined. The calculation of dose must be adapted to the physical requirements of the therapy
and is designed as an independent process. The calculated data are shown in various presentations. The treatment planning
system is applied to intratumoral chemotherapy. The drug is encapsulated in small carriers for prolonged release and injected
via catheters directly into the tumor interstitium, bypassing the blood-brain barrier. The dose is calculated using the time-dependent,
three-dimensional finite elements method. To achieve homogeneous temporal and spatial drug distribution it is necessary to
use a great number of catheters due to the limited diffusion of drug, which is not practical in neurosurgery. Therefore this
therapy concept is useful for small volumes only. Interstitial hyperthermia and brachytherapy, in contrast to intratumoral
chemotherapy, show successful clinical results.
Der Radiologe 04/1996; 36(9):737-743. · 0.61 Impact Factor
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ABSTRACT: The aim of 3D radiotherapy treatment planning is to match the dose as closely as possible to the target volume, thus avoiding side effects in healthy tissue and radiosensitive organs at risk. A virtual radiotherapy simulator designed for the definition of treatment parameters and the analysis of precalculated dose distributions enables iterative optimization of treatment plans.
VOXELPLAN is a software package for 3D radiotherapy treatment planning developed at the German Cancer Research Center; it consists of user interfaces for image segmentation, virtual therapy simulation, dose calculation, plan evaluation and patient documentation. It is written in C and FORTRAN and runs on VAXstation 4000, IBM RS/6000 and DEC ALPHA hardware.
Since 1990 a pilot installation of VOXELPLAN has been applied in clinical routine at the Center and at the University Clinic for Radiology, Heidelberg. Treatment for more than 1500 patients has been planned and carried out using the system, proving its technical and organizational applicability.
We expect better acceptance and further dissemination of the techniques described, conformation therapy as well as (after its technical realization) inverse planning, from continuous optimization of the planning process.
Der Radiologe 10/1995; 35(9):583-6. · 0.61 Impact Factor
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ABSTRACT: Three-dimensional radiotherapy planning is a complex and time-consuming optimization process which requires much experience. To simplify and to speed up the process of treatment planning as well as to exchange experience and therapeutic knowledge, the department of Medical Physics at the German Cancer Research Centre (DKFZ) in Heidelberg is developing an Internet-based 3D Radiotherapy planning and Information System (IRIS). IRIS designed internet-based client-server application, implemented using Java, CORBA and PVM. The concept of IRIS combines the functionality of an interactive tutorial with a discussion forum, teleconferencing tool and an atlas of dose distributions. Furthermore an integral knowledge-based system provides automatically generated, preoptimized treatment plans. This paper explains the technical design of the system and gives an overview of experiences gained by the technical realization of a first prototype using currently available internet technology. The prototype is currently running for testing in the intranet of DKFZ.
Medical Informatics and the Internet in Medicine 26(4):265-81. · 1.04 Impact Factor
