Open AccessOverranging and overbeaming measurement in area detector computed tomography: A method for simultaneous measurement in volume helical acquisition
Author(s) -
Urikura Atsushi,
Hara Takanori,
Yoshida Tsukasa,
Nishimaru Eiji,
Hoshino Takashi,
Nakaya Yoshihiro,
Endo Masahiro
Publication year - 2019
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1002/acm2.12650
Subject(s) - collimator , collimated light , optics , nuclear medicine , detector , beam (structure) , materials science , physics , medicine , laser
Purpose We propose a novel method to assess overbeaming and overranging, as well as the effect of reducing longitudinal exposure range, by using a dynamic z‐collimator in area detector computed tomography. Methods and materials A 500‐mm diameter cylindrical imaging plate was exposed by helical scanning in a dark room. The beam collimation of the helical acquisitions was set at 32 and 80 mm. Overbeaming and overranging with the dynamic z‐collimator were measured. Results The actual beam widths were approximately 39 and 88 mm at 32 and 80 mm collimation, respectively, and were relatively reduced owing to increased beam collimation. Overranging was 27.0 and 48.2 mm with a pitch of 0.83 and 1.49 at 32 mm collimation and 72.5 and 83.1 mm with a pitch of 0.87 and 0.99 at 80 mm collimation. The dynamic z‐collimator relatively reduced the overranging by 17.3% and 17.1% for the 32 and 80 mm collimation, respectively. Conclusion We devised a method to simultaneously measure overbeaming and overranging with only one helical acquisition. Although the dynamic z‐collimator reduced the overranging by approximately 17%, wider collimation widths and higher pitch settings would increase the exposure dose outside the scan range.