Robustness and precision of an automatic marker detection algorithm for online prostate daily targeting using a standard V-EPID

Authors

  • Aubin S.,

    1. Centre Hospitalier Universitaire de Québec (L'Hôtel-Dieu) and Centre de Recherche en Cancérologie de l'Université Laval, 11 Côte du Palais, Québec, QC, G1R 2J6, Canada
    2. Département de Physique, de Génie Physique et d'Optique, Université Laval, Ste-Foy, QC, G1K 7P4, Canada
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  • Beaulieu L.,

    1. Centre Hospitalier Universitaire de Québec (L'Hôtel-Dieu) and Centre de Recherche en Cancérologie de l'Université Laval, 11 Côte du Palais, Québec, QC, G1R 2J6, Canada
    2. Département de Physique, de Génie Physique et d'Optique, Université Laval, Ste-Foy, QC, G1K 7P4, Canada
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  • Pouliot S.,

    1. Centre Hospitalier Universitaire de Québec (L'Hôtel-Dieu) and Centre de Recherche en Cancérologie de l'Université Laval, 11 Côte du Palais, Québec, QC, G1R 2J6, Canada
    2. Department of Radiation Oncology, University of California in San Francisco (UCSF), 505 Parnassus Avenue, San Francisco, California 94143
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  • Pouliot J.,

    1. Centre Hospitalier Universitaire de Québec (L'Hôtel-Dieu) and Centre de Recherche en Cancérologie de l'Université Laval, 11 Côte du Palais, Québec, QC, G1R 2J6, Canada
    2. Department of Radiation Oncology, University of California in San Francisco (UCSF), 505 Parnassus Avenue, San Francisco, California 94143
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  • Roy R.,

    1. Département de Physique, de Génie Physique et d'Optique, Université Laval, Ste-Foy, QC, G1K 7P4, Canada
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  • Girouard L.-M.,

    1. Centre Hospitalier Universitaire de Québec (L'Hôtel-Dieu), 11 Côte du Palais, Québec, QC, G1R 2J6, Canada
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  • Martel-Brisson N.,

    1. Centre Hospitalier Universitaire de Québec (L'Hôtel-Dieu), 11 Côte du Palais, Québec, QC, G1R 2J6, Canada
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  • Vigneault E.,

    1. Centre Hospitalier Universitaire de Québec (L'Hôtel-Dieu), 11 Côte du Palais, Québec, QC, G1R 2J6, Canada
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  • Laverdière J.

    1. Centre Hospitalier Universitaire de Québec (L'Hôtel-Dieu), 11 Côte du Palais, Québec, QC, G1R 2J6, Canada
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Abstract

An algorithm for the daily localization of the prostate using implanted markers and a standard video-based electronic portal imaging device (V-EPID) has been tested. Prior to planning, three gold markers were implanted in the prostate of seven patients. The clinical images were acquired with a BeamViewPlus 2.1 V-EPID for each field during the normal course radiotherapy treatment and are used off-line to determine the ability of the automatic marker detection algorithm to adequately and consistently detect the markers. Clinical images were obtained with various dose levels from ranging 2.5 to 75 MU. The algorithm is based on marker attenuation characterization in the portal image and spatial distribution. A total of 1182 clinical images were taken. The results show an average efficiency of 93% for the markers detected individually and 85% for the group of markers. This algorithm accomplishes the detection and validation in 0.20–0.40 s. When the center of mass of the group of implanted markers is used, then all displacements can be corrected to within 1.0 mm in 84% of the cases and within 1.5 mm in 97% of cases. The standard video-based EPID tested provides excellent marker detection capability even with low dose levels. The V-EPID can be used successfully with radiopaque markers and the automatic detection algorithm to track and correct the daily setup deviations due to organ motions.

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