Reduction of the unnecessary dose from the over-range area with a spiral dynamic z-collimator: Comparison of beam pitch and detector coverage with 128-detector row CT

Takashi Shirasaka, Yoshinori Funama, Mutsukazu Hayashi, Shinichi Awamoto, Masatoshi Kondo, Yasuhiko Nakamura, Masamitsu Hatakenaka, Hiroshi Honda

    Research output: Contribution to journalArticle

    6 Citations (Scopus)

    Abstract

    Our purpose in this study was to assess the radiation dose reduction and the actual exposed scan length of over-range areas using a spiral dynamic z-collimator at different beam pitches and detector coverage. Using glass rod dosimeters, we measured the unilateral over-range scan dose between the beginning of the planned scan range and the beginning of the actual exposed scan range. Scanning was performed at detector coverage of 80.0 and 40.0 mm, with and without the spiral dynamic z-collimator. The dose-saving ratio was calculated as the ratio of the unnecessary over-range dose, with and without the spiral dynamic z-collimator. In 80.0 mm detector coverage without the spiral dynamic z-collimator, the actual exposed scan length for the over-range area was 108, 120, and 126 mm, corresponding to a beam pitch of 0.60, 0.80, and 0.99, respectively. With the spiral dynamic z-collimator, the actual exposed scan length for the over-range area was 48, 66, and 84 mm with a beam pitch of 0.60, 0.80, and 0.99, respectively. The dose-saving ratios with and without the spiral dynamic z-collimator for a beam pitch of 0.60, 0.80, and 0.99 were 35.07, 24.76, and 13.51%, respectively. With 40.0 mm detector coverage, the dose-saving ratios with and without the spiral dynamic z-collimator had the highest value of 27.23% with a low beam pitch of 0.60. The spiral dynamic z-collimator is important for a reduction in the unnecessary over-range dose and makes it possible to reduce the unnecessary dose by means of a lower beam pitch.

    Original languageEnglish
    Pages (from-to)53-58
    Number of pages6
    JournalRadiological physics and technology
    Volume5
    Issue number1
    DOIs
    Publication statusPublished - Jan 2012

    All Science Journal Classification (ASJC) codes

    • Radiation
    • Physical Therapy, Sports Therapy and Rehabilitation
    • Radiology Nuclear Medicine and imaging

    Fingerprint Dive into the research topics of 'Reduction of the unnecessary dose from the over-range area with a spiral dynamic z-collimator: Comparison of beam pitch and detector coverage with 128-detector row CT'. Together they form a unique fingerprint.

  • Cite this