The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform

Stephanie E Combs - One of the best experts on this subject based on the ideXlab platform.

  • clinical implementation and range evaluation of in vivo pet dosimetry for particle irradiation in patients with primary glioma
    Radiotherapy and Oncology, 2015
    Co-Authors: Sebastian P Nischwitz, Jurgen Debus, Julia Bauer, Thomas Haberer, Oliver Jakel, Thomas Welzel, Harald Rief, K Frey, Katia Parodi, Stephanie E Combs
    Abstract:

    Abstract Purpose The physical and biological properties of ion-beams offer various advantages in comparison to conventional radiotherapy, though uncertainties concerning quality assurance are still left. Due to the inverted depth Dose Profile, range accuracy is of paramount importance. We investigated the range deviations between planning simulation and post-fractional PET/CT measurement from particle therapy in primary glioblastoma. Methods and materials 20 patients with glioblastoma undergoing particle therapy at our institution were selected. 10 received a proton-boost, 10 a carbon-ion-boost in addition to standard treatment. After two fractions, we performed a PET/CT-scan of the brain. We compared the resulting range deviation based on the Most-likely-shift method between the two measurements, and the measurements with corresponding expectations, calculated with the Monte-Carlo code FLUKA. Results A patient's two measurements deviated by 0.7mm (±0.7mm). Overall comparison between measurements and simulation resulted in a mean range deviation of 3.3mm (±2.2mm) with significant lower deviations in the 12 C-arm. Conclusion The used planning concepts display the actual Dose distributions adequately. The carbon ion group's results are below the used PTV safety margins (3mm). Further adjustments to the simulation are required for proton irradiations. Some anatomical situations require particular attention to ensure highest accuracy and safety.

  • phase i study evaluating the treatment of patients with hepatocellular carcinoma hcc with carbon ion radiotherapy the prometheus 01 trial
    BMC Cancer, 2011
    Co-Authors: Stephanie E Combs, Daniel Habermehl, Tom M Ganten, Thomas Haberer, Oliver Jakel, J Schmidt, Lutz Edler, Iris Burkholder, Jurgen Debus
    Abstract:

    Background Treatment options for patients with advanced hepatocellular carcinoma (HCC) are often limited. In most cases, they are not amenable to local therapies including surgery or radiofrequency ablation. The multi-kinase inhibitor sorafenib has shown to increase overall survival in this patient group for about 3 months. Radiation therapy is a treatment alternative, however, high local Doses are required for long-term local control. However, due to the relatively low radiation tolerance of liver normal tissue, even using stereotactic techniques, delivery of sufficient Doses for successful local tumor control has not be achieved to date. Carbon ions offer physical and biological characteristics. Due to their inverted Dose Profile and the high local Dose deposition within the Bragg peak precise Dose application and sparing of normal tissue is possible. Moreover, in comparison to photons, carbon ions offer an increased relative biological effectiveness (RBE), which can be calculated between 2 and 3 depending on the HCC cell line as well as the endpoint analyzed. Japanese Data on the evaluation of carbon ion radiation therapy showed promising results for patients with HCC.

  • randomized phase ii study evaluating a carbon ion boost applied after combined radiochemotherapy with temozolomide versus a proton boost after radiochemotherapy with temozolomide in patients with primary glioblastoma the cleopatra trial
    BMC Cancer, 2010
    Co-Authors: Stephanie E Combs, Daniel Habermehl, Thomas Haberer, Oliver Jakel, Meinhard Kieser, Stefan Rieken, Anna Nikoghosyan, Renate Haselmann, Andreas Unterberg, Wolfgang Wick
    Abstract:

    Background Treatment standard for patients with primary glioblastoma (GBM) is combined radiochemotherapy with temozolomide (TMZ). Radiation is delivered up to a total Dose of 60 Gy using photons. Using this treatment regimen, overall survival could be extended significantly however, median overall survival is still only about 15 months. Carbon ions offer physical and biological advantages. Due to their inverted Dose Profile and the high local Dose deposition within the Bragg peak precise Dose application and sparing of normal tissue is possible. Moreover, in comparison to photons, carbon ions offer an increase relative biological effectiveness (RBE), which can be calculated between 2 and 5 depending on the GBM cell line as well as the endpoint analyzed. Protons, however, offer an RBE which is comparable to photons. First Japanese Data on the evaluation of carbon ion radiation therapy showed promising results in a small and heterogeneous patient collective.

Richard A Britten - One of the best experts on this subject based on the ideXlab platform.

  • variations in the rbe for cell killing along the depth Dose Profile of a modulated proton therapy beam
    Radiation Research, 2013
    Co-Authors: Richard A Britten, Vahagn Nazaryan, Leslie K Davis, Susan B Klein, D Nichiporov, Marc S Mendonca, Mark Wolanski, Xiliang Nie, Jerry George
    Abstract:

    Considerable evidence now exists to show that that the relative biological effectiveness (RBE) changes considerably along the proton depth-Dose distribution, with progressively higher RBE values at the distal part of the modulated, or spread out Bragg peak (SOBP) and in the distal Dose fall-off (DDF). However, the highly variable nature of the existing studies (with regards to cell lines, and to the physical properties and dosimetry of the various proton beams) precludes any consensus regarding the RBE weighting factor at any position in the depth-Dose Profile. We have thus conducted a systematic study on the variation in RBE for cell killing for two clinical modulated proton beams at Indiana University and have determined the relationship between the RBE and the Dose-averaged linear energy transfer (LETd) of the protons at various positions along the depth-Dose Profiles. Clonogenic assays were performed on human Hep2 laryngeal cancer cells and V79 cells at various positions along the SOBPs of beams with incident energies of 87 and 200 MeV. There was a marked variation in the radiosensitivity of both cell lines along the SOBP depth-Dose Profile of the 87 MeV proton beam. Using Hep2 cells, the D(0.1) isoeffect Dose RBE values (normalized against (60)Co) were 1.46 at the middle of SOBP, 2.1 at the distal end of the SOBP and 2.3 in the DDF. For V79 cells, the D(0.1) isoeffect RBE for the 87 MEV beam were 1.23 for the proximal end of the SOBP: 1.46 for the distal SOBP and 1.78 for the DDF. Similar D(0.1) isoeffect RBE values were found for Hep2 cells irradiated at various positions along the depth-Dose Profile of the 200 MeV beam. Our experimentally derived RBE values were significantly correlated (P = 0.001) with the mean LETd of the protons at the various depths, which confirmed that proton RBE is highly dependent on LETd. These in vitro data suggest that the RBE of the proton beam at certain depths is greater than 1.1, a value currently used in most treatment planning algorithms. Thus, the potential for increased cell killing and normal tissue damage in the distal regions of the proton SOBP may be greater than originally thought.

  • variations in the rbe for cell killing along the depth Dose Profile of a modulated proton therapy beam
    Radiation Research, 2013
    Co-Authors: Richard A Britten, Vahagn Nazaryan, Leslie K Davis, Susan B Klein, D Nichiporov, Marc S Mendonca, Mark Wolanski, Xiliang Nie, Jerry George
    Abstract:

    Considerable evidence now exists to show that that the relative biological effectiveness (RBE) changes considerably along the proton depth-Dose distribution, with progressively higher RBE values at the distal part of the modulated, or spread out Bragg peak (SOBP) and in the distal Dose fall-off (DDF). However, the highly variable nature of the existing studies (with regards to cell lines, and to the physical properties and dosimetry of the various proton beams) precludes any consensus regarding the RBE weighting factor at any position in the depth-Dose Profile. We have thus conducted a systematic study on the variation in RBE for cell killing for two clinical modulated proton beams at Indiana University and have determined the relationship between the RBE and the Dose-averaged linear energy transfer (LETd) of the protons at various positions along the depth-Dose Profiles. Clonogenic assays were performed on human Hep2 laryngeal cancer cells and V79 cells at various positions along the SOBPs of beams with ...

K Willbo - One of the best experts on this subject based on the ideXlab platform.

  • su ff t 414 the Dose area product in radiation therapy a new concept for the parameterisation of small fields
    Medical Physics, 2006
    Co-Authors: Armand Djouguela, Anja Rubach, D Harde, K Willbo
    Abstract:

    Purpose: To establish a new parameterisation of small fields. Material and Methods: The traditional parameterisation of a narrow photon field via the central axis Dose and the relative transversal Dose Profile has met considerable methodical complications. These difficulties are to find a sufficiently small detector, to adjust the detector accurately on the axis of the narrow beam and to find a detector material not responding to lateral changes of the electron spectrum within the small field. These obstacles can be avoided by reconsidering the parameterisation of the narrow‐field Dose distribution. The new parameter recommended for characterising the absolute Dose values in a plane perpendicular to the beam axis is the Dose‐area product DAP (the area integral of the Dose in this plane). It can be measured with a flat ionisation chamber of large cross section of the sensitive volume. Results and Conclusions: The radial adjustment of the large area chamber is by no means critical. The Dose‐area product provides a simple normalisation of the relative transversal Dose distribution which can be measured with radiochromic film. We have investigated the abilities of a large‐area flat ionisation chamber of PTW Freiburg (PTW TM 34070‐2,5) of 8,1 cm diameter and 2 mm thickness of the sensitive volume to measure the DAP of narrow photon beams with side lengths up to 5 cm. A modified output factor has been defined as the quotient of the DAP, measured at 5 cm phantom depth for SSD 100 cm distance of the phantom, and the monitor reading. Besides the useful feature of the DAP is its direct measurability during patient treatment by means of the DAVID chamber, an on‐line monitor arranged in the accessory holder, so that non‐negligible deviations of the actual from the chosen field size of narrow photon fields can be immediately detected.

  • the Dose area product a new parameter for the dosimetry of narrow photon beams
    Zeitschrift Fur Medizinische Physik, 2006
    Co-Authors: Armand Djouguela, A Ruhma, K Willbo, D Harde, Ralf Kollhoff, Jo Poppe
    Abstract:

    Abstract In the dosimetry of narrow photon fields with side lengths of the order of 1 cm, the traditional parametrisation via the absolute Dose on the beam axis and the relative lateral Dose distribution has to deal with the difficulty to find sufficiently small detectors and to adjust them accurately on the narrow-beam axis. This can be avoided by reconsidering the parametrisation, using as normalization factor the surface integral of the Dose in the plane perpendicular to the beam axis, abbreviated as the “Dose-area product” (DAP). We investigated and confirmed the ability of a large-area parallel-plate ionisation chamber, with a sensitive volume shaped as a flat cylinder of 81.6 mm diameter and 2 mm thickness, to perform the integration over the full lateral Dose Profile of narrow photon beams with side lengths up to 5 cm. The lateral adjustment of this large-area detector relative to a narrow photon beam is not critical. The large-area ionisation chamber was calibrated in terms of the DAP by reference to a 0.3 cm 3 ionisation chamber. A field-size dependent “modified output factor” was defined as the ratio of the DAP, measured at 5 cm phantom depth for 100 cm SSD, and the monitor reading. A prominent phenomenon of narrow photon fields is the field-size and source-distance independence of the relative axial Profile of the DAP as function of the thickness of a pre-absorber or of the depth in a phantom. For narrow-beam treatment planning in IMRT, the DAP is combined with the energy- and field size-dependent relative lateral Dose distribution which is represented, for example, by a Gaussian convolution kernel. Another useful feature of the DAP is the possibility of its direct control during patient irradiation by means of an on-line monitor with spatial resolution, arranged in the accessory holder.

David J Gladstone - One of the best experts on this subject based on the ideXlab platform.

  • improving treatment geometries in total skin electron therapy experimental investigation of linac angles and floor scatter Dose contributions using cherenkov imaging
    Medical Physics, 2018
    Co-Authors: Jacqueline M Andreozzi, Petr Brůža, Irwin I Tendler, K Mooney, Lesley A Jarvis, Jochen Cammin, Brian W Pogue, David J Gladstone
    Abstract:

    PURPOSE The purpose of this study was to identify the optimal treatment geometry for total skin electron therapy (TSET) using a new optimization metric from Cherenkov image analysis, and to investigate the sensitivity of the Cherenkov imaging method to floor scatter effects in this unique treatment setup. METHODS Cherenkov imaging using an intensified charge coupled device (ICCD) was employed to measure the relative surface Dose distribution as a 2D image in the total skin electron treatment plane. A 1.2 m × 2.2 m × 1 cm white polyethylene sheet was placed vertically at a source to surface distance (SSD) of 300 cm, and irradiated with 6 MeV high Dose rate TSET beams. The linear accelerator coordinate system used stipulates 0° is the bottom of the gantry arc, and progresses counterclockwise so that gantry angle 270° produces a horizontal beam orthogonal to the treatment plane. First, all unique pairs of treatment beams were analyzed to determine the performance of the currently recommended symmetric treatment angles (±20° from the horizontal), compared to treatment geometries unconstrained to upholding gantry angle symmetry. This was performed on two medical linear accelerators (linacs). Second, the extent of the floor scatter contributions to measured surface Dose at the extended SSD required for TSET were imaged using three gantry angles of incidence: 270° (horizontal), 253° (-17°), and 240° (-30°). Images of the surface Dose Profile at each angle were compared to the standard concrete floor when steel plates, polyvinyl chloride (PVC), and solid water were placed on the ground at the base of the treatment plane. Postprocessing of these images allowed for comparison of floor material-based scatter Profiles with previously published simulation results. RESULTS Analysis of the symmetric treatment geometry (270 ± 20°) and the identified optimal treatment geometry (270 + 23° and 270 - 17°) showed a 16% increase in the 90% isoDose area for the latter field pair on the first linac. The optimal asymmetric pair for the second linac (270 + 25° and 270 - 17°) provided a 52% increase in the 90% isoDose area when compared to the symmetric geometry. Difference images between Cherenkov images captured with test materials (steel, PVC, and solid water) and the control (concrete floor) demonstrated relative changes in the two-dimensional (2D) Dose Profile over a 1 × 1.9 m region of interest (ROI) that were consistent with published simulation data. Qualitative observation of the residual images demonstrates localized increases and decreases with respect to the change in floor material and gantry angle. The most significant changes occurred when the beam was most directly impinging the floor (gantry angle 240°, horizontal -30°), where the PVC floor material decreased scatter Dose by 1-3% in 7.2% of the total ROI area, and the steel plate increased scatter Dose by 1-3% in 7.0% of the total ROI area. CONCLUSIONS An updated Cherenkov imaging method identified asymmetric, machine-dependent TSET field angle pairs that provided much larger 90% isoDose areas than the commonly adopted symmetric geometry suggested by Task Group 30 Report 23. A novel demonstration of scatter Dose Cherenkov imaging in the TSET field was established.

Oliver Jakel - One of the best experts on this subject based on the ideXlab platform.

  • clinical implementation and range evaluation of in vivo pet dosimetry for particle irradiation in patients with primary glioma
    Radiotherapy and Oncology, 2015
    Co-Authors: Sebastian P Nischwitz, Jurgen Debus, Julia Bauer, Thomas Haberer, Oliver Jakel, Thomas Welzel, Harald Rief, K Frey, Katia Parodi, Stephanie E Combs
    Abstract:

    Abstract Purpose The physical and biological properties of ion-beams offer various advantages in comparison to conventional radiotherapy, though uncertainties concerning quality assurance are still left. Due to the inverted depth Dose Profile, range accuracy is of paramount importance. We investigated the range deviations between planning simulation and post-fractional PET/CT measurement from particle therapy in primary glioblastoma. Methods and materials 20 patients with glioblastoma undergoing particle therapy at our institution were selected. 10 received a proton-boost, 10 a carbon-ion-boost in addition to standard treatment. After two fractions, we performed a PET/CT-scan of the brain. We compared the resulting range deviation based on the Most-likely-shift method between the two measurements, and the measurements with corresponding expectations, calculated with the Monte-Carlo code FLUKA. Results A patient's two measurements deviated by 0.7mm (±0.7mm). Overall comparison between measurements and simulation resulted in a mean range deviation of 3.3mm (±2.2mm) with significant lower deviations in the 12 C-arm. Conclusion The used planning concepts display the actual Dose distributions adequately. The carbon ion group's results are below the used PTV safety margins (3mm). Further adjustments to the simulation are required for proton irradiations. Some anatomical situations require particular attention to ensure highest accuracy and safety.

  • hypofractionated carbon ion therapy delivered with scanned ion beams for patients with hepatocellular carcinoma feasibility and clinical response
    Radiation Oncology, 2013
    Co-Authors: Daniel Habermehl, Jurgen Debus, Tom M Ganten, Mariakatharina Ganten, Julia Bauer, Ingo C Brecht, S Brons, Thomas Haberer, Martin Haertig, Oliver Jakel
    Abstract:

    Purpose Photon-based radiation therapy does currently not play a major role as local ablative treatment for hepatocellular carcinoma (HCC). Carbon ions offer distinct physical and biological advantages. Due to their inverted Dose Profile and the high local Dose deposition within the Bragg peak, precise Dose application and sparing of normal tissue is possible. Furthermore, carbon ions have an increased relative biological effectiveness (RBE) compared to photons.

  • phase i study evaluating the treatment of patients with hepatocellular carcinoma hcc with carbon ion radiotherapy the prometheus 01 trial
    BMC Cancer, 2011
    Co-Authors: Stephanie E Combs, Daniel Habermehl, Tom M Ganten, Thomas Haberer, Oliver Jakel, J Schmidt, Lutz Edler, Iris Burkholder, Jurgen Debus
    Abstract:

    Background Treatment options for patients with advanced hepatocellular carcinoma (HCC) are often limited. In most cases, they are not amenable to local therapies including surgery or radiofrequency ablation. The multi-kinase inhibitor sorafenib has shown to increase overall survival in this patient group for about 3 months. Radiation therapy is a treatment alternative, however, high local Doses are required for long-term local control. However, due to the relatively low radiation tolerance of liver normal tissue, even using stereotactic techniques, delivery of sufficient Doses for successful local tumor control has not be achieved to date. Carbon ions offer physical and biological characteristics. Due to their inverted Dose Profile and the high local Dose deposition within the Bragg peak precise Dose application and sparing of normal tissue is possible. Moreover, in comparison to photons, carbon ions offer an increased relative biological effectiveness (RBE), which can be calculated between 2 and 3 depending on the HCC cell line as well as the endpoint analyzed. Japanese Data on the evaluation of carbon ion radiation therapy showed promising results for patients with HCC.

  • randomized phase ii study evaluating a carbon ion boost applied after combined radiochemotherapy with temozolomide versus a proton boost after radiochemotherapy with temozolomide in patients with primary glioblastoma the cleopatra trial
    BMC Cancer, 2010
    Co-Authors: Stephanie E Combs, Daniel Habermehl, Thomas Haberer, Oliver Jakel, Meinhard Kieser, Stefan Rieken, Anna Nikoghosyan, Renate Haselmann, Andreas Unterberg, Wolfgang Wick
    Abstract:

    Background Treatment standard for patients with primary glioblastoma (GBM) is combined radiochemotherapy with temozolomide (TMZ). Radiation is delivered up to a total Dose of 60 Gy using photons. Using this treatment regimen, overall survival could be extended significantly however, median overall survival is still only about 15 months. Carbon ions offer physical and biological advantages. Due to their inverted Dose Profile and the high local Dose deposition within the Bragg peak precise Dose application and sparing of normal tissue is possible. Moreover, in comparison to photons, carbon ions offer an increase relative biological effectiveness (RBE), which can be calculated between 2 and 5 depending on the GBM cell line as well as the endpoint analyzed. Protons, however, offer an RBE which is comparable to photons. First Japanese Data on the evaluation of carbon ion radiation therapy showed promising results in a small and heterogeneous patient collective.