Experimental determination of the photon-energy dependent dose-to-water response of TLD600 and TLD700 (LiF:Mg,Ti) thermoluminescence detectors.

The aim of this study has been the experimental determination of the energy dependent dose-to-water response of TLD600 and TLD700 thermoluminescent detectors (Harshaw) in X-ray beams with mean photon energies from about 20 to 200keV in comparison with Co gamma rays and 6MV X-rays. Experiments were carried out in collaboration with the German secondary standard laboratory PTW Freiburg. The energy dependent relative responses of TLD600 and TLD700 thermoluminescence detectors were determined at radiation qualities between 30kV and 280kV.

Development, physical properties and clinical applicability of a mechanical Multileaf Collimator for the use in Cobalt-60 radiotherapy.

According to the Directory of Radiotherapy Centres (DIRAC) there are 2348 Cobalt-60 (Co-60) teletherapy units worldwide, most of them in low and middle income countries, compared to 11046 clinical accelerators. To improve teletherapy with Co-60, a mechanical Multi-Leaf Collimator (MLC) was developed, working with pneumatic pressure and thus independent of electricity supply. Instead of tungsten, brass was used as leaf material to make the mechanical MLC more affordable.

Dosimetric robustness against setup errors in charged particle radiotherapy of skull base tumors.

Background: It is expected that physical dose deposition properties render charged particle dose distributions sensitive to targeting uncertainties. Purpose of this work was to investigate the robustness of scanned-beam particle therapy plans against setup errors for different optimization modalities, beam setups and ion species.

Material And Methods: For 15 patients with skull base tumors, localized in regions of severe tissue density heterogeneity, scanned lateral-opposed-beam treatment plans were prepared with the treatment planning system TRiP98, employing different optimization settings (single- and multiple-field modulation) and ion species (carbon ions and protons).

Independent calculation of dose distributions for helical tomotherapy using a conventional treatment planning system.

Purpose: The dosimetric verification of treatment plans in helical tomotherapy usually is carried out via verification measurements. In this study, a method for independent dose calculation of tomotherapy treatment plans is presented, that uses a conventional treatment planning system with a pencil kernel dose calculation algorithm for generation of verification dose distributions based on patient CT data.

Methods: A pencil beam algorithm that directly uses measured beam data was configured for dose calculation for a tomotherapy machine.

Proposal for a new prognostic score for linac-based radiosurgery in cerebral arteriovenous malformations.

Purpose: We evaluate patient-, angioma-, and treatment-specific factors for successful obliteration of cerebral arteriovenous malformations (AVM) to develop a new appropriate score to predict patient outcome after linac-based radiosurgery (RS).

Methods And Materials: This analysis in based on 293 patients with cerebral AVM. Mean age at treatment was 38.

Repeated linac-based radiosurgery in high-grade cerebral arteriovenous-malformations (AVM) Spetzler-Martin grade III to IV previously treated with radiosurgery.

Background: Aim was to access outcome and toxicity of repeated linac-based radiosurgery in incompletely obliterated cerebral AVM.

Patients And Methods: Between 1998 and 2008, 11 patients were treated with repeated radiosurgery. The median dose to the 80%-isodose was 15 Gy (range, 12-18 Gy).

Reirradiation with intensity-modulated radiotherapy in recurrent head and neck cancer.

Background: In this retrospective investigation we analyzed outcome and toxicity after intensity-modulated reirradiation of recurrent head and neck cancer.

Methods: Thirty-eight patients with local recurrent head and neck cancer were evaluated. The median dose of initial radiotherapy was 61 Gy.

Intensity modulated radiotherapy in the management of sacral chordoma in primary versus recurrent disease.

Purpose: To investigate treatment outcome in patients suffering from sacral chordoma after intensity modulated radiotherapy (IMRT) for primary versus recurrent disease.

Material/methods: We report on 34 patients with histologically proven sacral chordoma. Seventeen patients were treated at time of initial diagnosis with post-operative IMRT (n=13) or with IMRT alone (n=4).

Patterns of failure after stereotactic radiotherapy of intracranial meningioma.

The aim of this work is to evaluate patterns of failure in patients with recurrent meningioma after stereotactic radiotherapy. Of 411 patients with intracranial meningioma treated with radiotherapy at our institution, 22 patients with local tumor progression diagnosed by magnetic resonance imaging (MRI) after radiotherapy (RT) were identified and further investigated. The histologic grade of the meningiomas was World Health Organization (WHO) grade I in 54.

Fractionated stereotactic radiation therapy in the management of primary optic nerve sheath meningiomas.

We analysed our long-term results after fractionated stereotactic radiotherapy (FSRT) in patients with primary optic nerve sheath (pONSM) meningioma, as a rare subtype of meningiomas. Between 01/1995 and 12/2007, 32 patients with pONSM were treated with FSRT. Fifteen patients received radiotherapy as primary treatment, four after biopsy, and six patients after surgical resection.

4D-Imaging of the lung: reproducibility of lesion size and displacement on helical CT, MRI, and cone beam CT in a ventilated ex vivo system.

Purpose: Four-dimensional (4D) imaging is a key to motion-adapted radiotherapy of lung tumors. We evaluated in a ventilated ex vivo system how size and displacement of artificial pulmonary nodules are reproduced with helical 4D-CT, 4D-MRI, and linac-integrated cone beam CT (CBCT).

Methods And Materials: Four porcine lungs with 18 agarose nodules (mean diameters 1.

Accuracy of a commercial optical 3D surface imaging system for realignment of patients for radiotherapy of the thorax.

Accurate and reproducible patient setup is a prerequisite to fractionated radiotherapy. To evaluate the applicability and technical performance of a commercial 3D surface imaging system for repositioning of breast cancer patients, measurements were performed in a rigid anthropomorphic phantom as well as in healthy volunteers. The camera system records a respiration-gated surface model of the imaged object, which may be registered to a previously recorded reference model.

Risk of hemorrhage and obliteration rates of LINAC-based radiosurgery for cerebral arteriovenous malformations treated after prior partial embolization.

Purpose: We investigate patient outcome, risk of hemorrhage, and factors affecting obliteration after LINAC-based radiosurgery (RS) for cerebral arteriovenous malformations (AVM) treated after partial embolization.

Methods And Materials: This analysis is based on 50 patients treated after prior embolization. According to the Spetzler-Martin criteria the AVM classification was as follows: 9 patients, Grade I (18%); 19, Grade II (38%); 18, Grade III (36%); and 4, Grade IV (8%).

Intensity-modulated radiotherapy for complex-shaped meningioma of the skull base: long-term experience of a single institution.

Purpose: We analyzed our long-term experience with intensity-modulated radiotherapy (IMRT) in patients with complex-shaped meningioma of the skull base.

Patients And Methods: Between January 1998 and December 2004, 94 patients with complex-shaped meningioma were treated using IMRT at our institution. Tumor distribution was: World Health Organization (WHO) Grade 1 in 54.

Prediction of radiation-induced changes in the lung after stereotactic body radiation therapy of non-small-cell lung cancer.

Purpose: To estimate the risk of radiation-induced changes in the lung before single-dose treatment (stereotactic body radiation therapy [SBRT]) of lung cancer, the quantitative dose-response and volume-response relations must be known.

Methods And Materials: A total of 64 patients treated for non-small-cell lung cancer with single doses of 20-30 Gy were classified according to the occurrence or nonoccurrence of perifocal changes in the lung detected by CT. Patients without toxic events in the lung were required to have >or=6 months of follow-up.

Fractionated stereotactic radiation therapy in the management of benign cavernous sinus meningiomas : long-term experience and review of the literature.

Purpose: To analyze own long-term results with fractionated stereotactic radiotherapy (FSRT) in patients with benign meningiomas of the cavernous sinus and to review the literature on these rare lesions.

Patients And Methods: 57 patients were treated with FSRT for benign meningiomas of the cavernous sinus between 01/1990 and 12/2003 at the authors' institution. Histology was WHO grade I in 28/57 lesions, and undetermined in 29/57 lesions.

Radiation therapy with charged particles.

Charged particle beams can offer an improved dose conformation to the target volume as compared with photon radiotherapy, with better sparing of normal tissue structures close to the target. In addition, beams of ions heavier than (4)He exhibit a strong increase of the linear energy transfer in the Bragg peak as compared with the entrance region. These physical and biological properties are much more favorable than in photon radiotherapy.

Pediatric cerebral arteriovenous malformations: the role of stereotactic linac-based radiosurgery.

Purpose: To evaluate retrospectively clinical outcome and obliteration rates after linac-based radiosurgery (RS) in children with cerebral arteriovenous malformations (AVM).

Methods And Materials: Between 1996 and 2002, 22 children with cerebral AVM were treated at our institution. Mean age at treatment was 11.

Linac-based radiosurgery or hypofractionated stereotactic radiotherapy in the treatment of large cerebral arteriovenous malformations.

Purpose: We investigate retrospectively clinical outcome after radiosurgery (RS) or hypofractionated stereotactic radiotherapy (HSRT) in patients with large cerebral arteriovenous malformations (AVMs).

Methods And Materials: This analysis is based on 48 patients with cerebral AVM greater than 4 cm treated with HSRT or RS at our institution. Fifteen patients received HSRT, with 26 Gy median total dose in 4 to 5 fractions, and 33 patients received RS with 17 Gy median total dose in 4 to 5 fractions.

Stereotactic linac-based radiosurgery in the treatment of cerebral arteriovenous malformations located deep, involving corpus callosum, motor cortex, or brainstem.

Purpose: To evaluate patient outcome and obliteration rates after radiosurgery (RS) for cerebral arteriovenous malformations (AVM) located deep, in the motor cortex or brainstem and those involving corpus callosum.

Methods And Materials: This analysis is based on 65 patients. AVM classification according to Spetzler-Martin was 13 patients Grade 2, 39 Grade 3, 12 Grade 4, and 1 Grade 5.

[Evaluation and optimization of an image-subtraction method for the analysis of the repositioning accuracy of female patients with breast cancer].

To analyze the repositioning accuracy in female patients with breast carcinoma, two different setups of an image-subtraction system (Positioning System FIVE) were devised using different numbers and alignments of lasers. The applicability of the system was tested for repositioning of the breast in normal volunteers. Horizontal translations as well as breathing-related movements in the vertical direction were measured.

Treatment outcome after linac-based radiosurgery in cerebral arteriovenous malformations: retrospective analysis of factors affecting obliteration.

Purpose: We investigated patient outcome and factors affecting obliteration rate after radiosurgery in cerebral arteriovenous malformations (AVM).

Material And Methods: We have treated 110 patients with cerebral AVM with linac-based radiosurgery (RS). AVM classification according Spetzler-Martin was 17 patients grade I (15%), 39 grade II (36%), 41 grade III (37%), 12 grade IV (11%) and 1 grade V (1%).

Influence of different breathing maneuvers on internal and external organ motion: use of fiducial markers in dynamic MRI.

Purpose: To investigate, with dynamic magnetic resonance imaging (dMRI) and a fiducial marker, the influence of different breathing maneuvers on internal organ and external chest wall motion.

Methods And Materials: Lung and chest wall motion of 16 healthy subjects (13 male, 3 female) were examined with real-time trueFISP (true fast imaging with steady-state precession) dMRI and a small inductively coupled marker coil on either the abdomen or thorax. Three different breathing maneuvers were performed (predominantly "abdominal breathing," "thoracic breathing," and unspecific "normal breathing").