z-logo
open-access-imgOpen Access
Estimation of primary radiation output for wide‐beam computed tomography scanner
Author(s) -
Fukuda Atsushi,
Lin PeiJan P.,
Ichikawa Nao,
Matsubara Kosuke
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/acm2.12598
Subject(s) - isocenter , kerma , beam (structure) , ionization chamber , nuclear medicine , percentage depth dose curve , scanner , optics , beam diameter , materials science , aperture (computer memory) , physics , radiation , dosimetry , ionization , imaging phantom , medicine , ion , laser , quantum mechanics , laser beams , acoustics
Purpose To estimate in‐air primary radiation output in a wide‐beam multidetector computed tomography (CT) scanner. Materials and methods A 6‐cc ionization chamber was placed free‐in‐air at the isocenter, and two sheets of lead (1‐mm thickness) were placed on the bottom of the gantry cover, forming apertures of 40–80 mm in increments of 8 mm. The air‐kerma rate profiles were measured with and without the apertures ( K ˙ w - A ,K ˙ w / o - A ) for 4.8 s at tube potentials of 80, 100, 120, and 135 kVp, tube current of 50 mA, and rotation time of 0.4 s. The nominal beam width was varied from 40 to 160 mm in increments of 40 mm. Upon completion of data acquisition, theK ˙ w / o - Awere plotted as a function of the measured beam width, and the extrapolated dose rates ( K ˙ 0 - w / o - A ) at zero beam width were calculated by second‐order least‐squares estimation. Similarly, theK ˙ w - Awere plotted as a function of the radiation field (measured beam width × aperture size at the isocenter), and the extrapolated dose rates ( K ˙ 0 - w - A ) were compared with theK ˙ 0 - w / o - A . Results The means and standard errors of theK ˙ w / o - Awith 40‐, 80‐, 120‐, and 160‐mm nominal beam widths at 120 kVp were 10.94 ± 0.01, 11.13 ± 0.01, 11.22 ± 0.01, and 11.31 ± 0.01 mGy/s, respectively, and theK ˙ 0 - w / o - Awas reduced to 10.67 ± 0.02 mGy/s. TheK ˙ 0 - w - Aof 40‐, 80‐, 120‐, and 160‐mm beam widths were reduced to 10.6 ± 0.1, 10.6 ± 0.2, 10.5 ± 0.1, and 10.6 ± 0.1 mGy/s and were not significantly different from theK ˙ 0 - w / o - A . Conclusions A method for describing the in‐air primary radiation output in a wide‐beam CT scanner was proposed that provides a means to characterize the scatter‐to‐primary ratio of the CT scanner.

The content you want is available to Zendy users.

Already have an account? Click here to sign in.
Having issues? You can contact us here