Application of the IEC3.1 standard of CTDI100 to a supine CBCT device

Benyameen Keelson, Dimitri Buytaert, Gert Van Gompel, Jan Casselman, Klaus Bacher, Yannick De Brucker, Nico Buls

Research output: Chapter in Book/Report/Conference proceedingMeeting abstract (Book)

Abstract

Purpose: To investigate the feasibility of extending the IEC 3.1 CTDI100 as
defined by the IAEA to CBCT and compare with device indicated CTDI and an
approximation of the "true" CTDI.

Methods and Materials: Weighted CTDI (CTDIw) measurements of a 16cm
diameter dosimetry phantom were obtained on a Newtom 5G (Newtom,
Verona, Italy) CBCT using a 15x5 cm and 15x12 cm field-of-view (indicated as
diameter by height).CTDIw following the IEC 3.1 definition was computed by
multiplying the CTDIw of a reference collimation (15x5) with the quotient of
free-in-air CTDI measurements at the collimation of interest (15x12) and the
reference collimation. In addition, to approximate CTDI∞ ("true" CTDI), CTDI measurements were performed in a 32 cm long phantom, constructed as a
longitudinal combination of two 16 cm diameter phantoms. For the latter
measurements, referred to as CTDI300, an integration length of 30 cm was
used i.e. integrated dose over three adjacent positions with the pencil
chamber.

Results: True CTDIw values were 22mGy/100mAs and 25,8mGy/100mAs for
the 15X5 and 15X12 protocols respectively. These values corresponded to an
underestimation by the device Indicated CTDIw values of 57% and 31% for the
15x12 and 15 x 5 protocols respectively. The IEC 3.1 definition however
resulted in underestimations of 18 and 14 % for the 15x12 and 15x5 protocols
respectively relative to the true CTDIw.

Conclusion: CTDI using the IEC 3.1 method resulted in reasonable deviations
from the "true" CTDI and is recommended to allow for comparison of doses
between conventional CT and CBCT.
Original languageEnglish
Title of host publication Abstract book of European Congress of Radiology (ECR 2019)
PublisherSpringer
ChapterS
Pages530-530
Number of pages1
Publication statusPublished - 2019

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