The Experts below are selected from a list of 13386 Experts worldwide ranked by ideXlab platform

Jan J W Lagendijk - One of the best experts on this subject based on the ideXlab platform.

  • integrating a mri scanner with a 6 mv radiotherapy accelerator dose increase at tissue air interfaces in a lateral magnetic field due to returning electrons
    Physics in Medicine and Biology, 2005
    Co-Authors: Aje Raaijmakers, B W Raaymakers, Jan J W Lagendijk
    Abstract:

    In the framework of the development of the integration of a MRI-scanner with a linear accelerator, the influence of a lateral, magnetic field on the dose distribution has to be determined. Dose increase is expected at tissue-air boundaries, due to the electron return effect (ERE): electrons entering air will describe a Circular Path and return into the phantom causing extra dose deposition. Using IMRT with many beam directions, this exit dose will not constitute a problem. Dose levels behind air cavities will decrease because of the absence of electrons crossing the cavity. The ERE has been demonstrated both by simulation and experiment. Monte Carlo simulations are performed with GEANT4, irradiating a water-air-water phantom in a lateral magnetic field. Also an air tube in water has been simulated, resulting in slightly twisted regions of dose increase and decrease. Experimental demonstration is achieved by film measurement in a perspex-air-perspex phantom in an electromagnet. Although the ERE causes dose increase before air cavities, relatively flat dose profiles can be obtained for the investigated cases using opposite beam configurations. More research will be necessary whether this holds for more realistic geometries with the use of IMRT and whether the ERE can be turned to our advantage when treating small tumour sites at air cavities.

  • integrating a mri scanner with a 6 mv radiotherapy accelerator dose increase at tissue air interfaces in a lateral magnetic field due to returning electrons
    Physics in Medicine and Biology, 2005
    Co-Authors: Aje Raaijmakers, B W Raaymakers, Jan J W Lagendijk
    Abstract:

    In the framework of the development of the integration of a MRI-scanner with a linear accelerator, the influence of a lateral, magnetic field on the dose distribution has to be determined. Dose increase is expected at tissue-air boundaries, due to the electron return effect (ERE): electrons entering air will describe a Circular Path and return into the phantom causing extra dose deposition. Using IMRT with many beam directions, this exit dose will not constitute a problem. Dose levels behind air cavities will decrease because of the absence of electrons crossing the cavity. The ERE has been demonstrated both by simulation and experiment. Monte Carlo simulations are performed with GEANT4, irradiating a water–air–water phantom in a lateral magnetic field. Also an air tube in water has been simulated, resulting in slightly twisted regions of dose increase and decrease. Experimental demonstration is achieved by film measurement in a perspex–air–perspex phantom in an electromagnet. Although the ERE causes dose increase before air cavities, relatively flat dose profiles can be obtained for the investigated cases using opposite beam configurations. More research will be necessary whether this holds for more realistic geometries with the use of IMRT and whether the ERE can be turned to our advantage when treating small tumour sites at air cavities.

Aje Raaijmakers - One of the best experts on this subject based on the ideXlab platform.

  • integrating a mri scanner with a 6 mv radiotherapy accelerator dose increase at tissue air interfaces in a lateral magnetic field due to returning electrons
    Physics in Medicine and Biology, 2005
    Co-Authors: Aje Raaijmakers, B W Raaymakers, Jan J W Lagendijk
    Abstract:

    In the framework of the development of the integration of a MRI-scanner with a linear accelerator, the influence of a lateral, magnetic field on the dose distribution has to be determined. Dose increase is expected at tissue-air boundaries, due to the electron return effect (ERE): electrons entering air will describe a Circular Path and return into the phantom causing extra dose deposition. Using IMRT with many beam directions, this exit dose will not constitute a problem. Dose levels behind air cavities will decrease because of the absence of electrons crossing the cavity. The ERE has been demonstrated both by simulation and experiment. Monte Carlo simulations are performed with GEANT4, irradiating a water-air-water phantom in a lateral magnetic field. Also an air tube in water has been simulated, resulting in slightly twisted regions of dose increase and decrease. Experimental demonstration is achieved by film measurement in a perspex-air-perspex phantom in an electromagnet. Although the ERE causes dose increase before air cavities, relatively flat dose profiles can be obtained for the investigated cases using opposite beam configurations. More research will be necessary whether this holds for more realistic geometries with the use of IMRT and whether the ERE can be turned to our advantage when treating small tumour sites at air cavities.

  • integrating a mri scanner with a 6 mv radiotherapy accelerator dose increase at tissue air interfaces in a lateral magnetic field due to returning electrons
    Physics in Medicine and Biology, 2005
    Co-Authors: Aje Raaijmakers, B W Raaymakers, Jan J W Lagendijk
    Abstract:

    In the framework of the development of the integration of a MRI-scanner with a linear accelerator, the influence of a lateral, magnetic field on the dose distribution has to be determined. Dose increase is expected at tissue-air boundaries, due to the electron return effect (ERE): electrons entering air will describe a Circular Path and return into the phantom causing extra dose deposition. Using IMRT with many beam directions, this exit dose will not constitute a problem. Dose levels behind air cavities will decrease because of the absence of electrons crossing the cavity. The ERE has been demonstrated both by simulation and experiment. Monte Carlo simulations are performed with GEANT4, irradiating a water–air–water phantom in a lateral magnetic field. Also an air tube in water has been simulated, resulting in slightly twisted regions of dose increase and decrease. Experimental demonstration is achieved by film measurement in a perspex–air–perspex phantom in an electromagnet. Although the ERE causes dose increase before air cavities, relatively flat dose profiles can be obtained for the investigated cases using opposite beam configurations. More research will be necessary whether this holds for more realistic geometries with the use of IMRT and whether the ERE can be turned to our advantage when treating small tumour sites at air cavities.

Taizo Motomura - One of the best experts on this subject based on the ideXlab platform.

  • Flagellar waveforms of gametes in the brown alga Ectocarpus siliculosus
    European Journal of Phycology, 2015
    Co-Authors: Nana Kinoshita, Chikako Nagasato, Kogiku Shiba, Kazuo Inaba, Taizo Motomura
    Abstract:

    AbstractBrown algae are members of the Stramenopiles and their gametes generally have two heterogeneous flagella: a long anterior flagellum (AF) with mastigonemes and a short posterior flagellum (PF). In this study, swimming Paths and flagellar waveforms in free-swimming and thigmotactic-swimming male and female gametes and in male gametes during chemotaxis, were quantitatively analysed in the model brown alga Ectocarpus siliculosus. This analysis was performed using a high-speed video camera. It was revealed that the AF plays a role in changing the locomotion of male and female gametes from free-swimming to thigmotactic-swimming and also in changing the swimming Path of male gametes from linear to Circular during chemotaxis. In the presence of a sex pheromone, male gametes changed their swimming Path from linear (swimming Path curvature, 0–0.02 µm–1) to middle and small Circular Path (swimming Path curvature, 0.04–0.20 µm–1). The flagellar asymmetry and the deflection angle of the AF became larger, where...

B W Raaymakers - One of the best experts on this subject based on the ideXlab platform.

  • integrating a mri scanner with a 6 mv radiotherapy accelerator dose increase at tissue air interfaces in a lateral magnetic field due to returning electrons
    Physics in Medicine and Biology, 2005
    Co-Authors: Aje Raaijmakers, B W Raaymakers, Jan J W Lagendijk
    Abstract:

    In the framework of the development of the integration of a MRI-scanner with a linear accelerator, the influence of a lateral, magnetic field on the dose distribution has to be determined. Dose increase is expected at tissue-air boundaries, due to the electron return effect (ERE): electrons entering air will describe a Circular Path and return into the phantom causing extra dose deposition. Using IMRT with many beam directions, this exit dose will not constitute a problem. Dose levels behind air cavities will decrease because of the absence of electrons crossing the cavity. The ERE has been demonstrated both by simulation and experiment. Monte Carlo simulations are performed with GEANT4, irradiating a water-air-water phantom in a lateral magnetic field. Also an air tube in water has been simulated, resulting in slightly twisted regions of dose increase and decrease. Experimental demonstration is achieved by film measurement in a perspex-air-perspex phantom in an electromagnet. Although the ERE causes dose increase before air cavities, relatively flat dose profiles can be obtained for the investigated cases using opposite beam configurations. More research will be necessary whether this holds for more realistic geometries with the use of IMRT and whether the ERE can be turned to our advantage when treating small tumour sites at air cavities.

  • integrating a mri scanner with a 6 mv radiotherapy accelerator dose increase at tissue air interfaces in a lateral magnetic field due to returning electrons
    Physics in Medicine and Biology, 2005
    Co-Authors: Aje Raaijmakers, B W Raaymakers, Jan J W Lagendijk
    Abstract:

    In the framework of the development of the integration of a MRI-scanner with a linear accelerator, the influence of a lateral, magnetic field on the dose distribution has to be determined. Dose increase is expected at tissue-air boundaries, due to the electron return effect (ERE): electrons entering air will describe a Circular Path and return into the phantom causing extra dose deposition. Using IMRT with many beam directions, this exit dose will not constitute a problem. Dose levels behind air cavities will decrease because of the absence of electrons crossing the cavity. The ERE has been demonstrated both by simulation and experiment. Monte Carlo simulations are performed with GEANT4, irradiating a water–air–water phantom in a lateral magnetic field. Also an air tube in water has been simulated, resulting in slightly twisted regions of dose increase and decrease. Experimental demonstration is achieved by film measurement in a perspex–air–perspex phantom in an electromagnet. Although the ERE causes dose increase before air cavities, relatively flat dose profiles can be obtained for the investigated cases using opposite beam configurations. More research will be necessary whether this holds for more realistic geometries with the use of IMRT and whether the ERE can be turned to our advantage when treating small tumour sites at air cavities.

Nana Kinoshita - One of the best experts on this subject based on the ideXlab platform.

  • Flagellar waveforms of gametes in the brown alga Ectocarpus siliculosus
    European Journal of Phycology, 2015
    Co-Authors: Nana Kinoshita, Chikako Nagasato, Kogiku Shiba, Kazuo Inaba, Taizo Motomura
    Abstract:

    AbstractBrown algae are members of the Stramenopiles and their gametes generally have two heterogeneous flagella: a long anterior flagellum (AF) with mastigonemes and a short posterior flagellum (PF). In this study, swimming Paths and flagellar waveforms in free-swimming and thigmotactic-swimming male and female gametes and in male gametes during chemotaxis, were quantitatively analysed in the model brown alga Ectocarpus siliculosus. This analysis was performed using a high-speed video camera. It was revealed that the AF plays a role in changing the locomotion of male and female gametes from free-swimming to thigmotactic-swimming and also in changing the swimming Path of male gametes from linear to Circular during chemotaxis. In the presence of a sex pheromone, male gametes changed their swimming Path from linear (swimming Path curvature, 0–0.02 µm–1) to middle and small Circular Path (swimming Path curvature, 0.04–0.20 µm–1). The flagellar asymmetry and the deflection angle of the AF became larger, where...