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Title: SU-F-I-05: Dose Symmetry for CTDI Equivalent Measurements with Limited Angle CBCT

Abstract

Purpose: CTDI measurements, useful for characterizing the x-ray output for multi-detector CT (MDCT), require a 360° rotation of the gantry; this presents a problem for cone beam CT (CBCT) due to its limited angular rotation. The purpose of this work is to demonstrate a methodology for overcoming this limited angular rotation so that CTDI measurements can also be made on CBCT systems making it possible to compare the radiation output from both types of system with a common metric. Methods: The symmetry of the CTDI phantom allows a 360° CTDI measurement to be replaced with two 180° measurements. A pencil chamber with a real-time digitizer was placed at the center of the head phantom (16 cm, PMMA) and the resulting exposure measurement from a 180° acquisition was doubled. A pair of edge measurements, each obtained with the gantry passing through the same 180 arc, was obtained with the pencil chamber at opposite edges of the diameter of the phantom and then summed. The method was demonstrated on a clinical CT scanner (Philips, Brilliance6) and then implemented on an interventional system (Siemens, Axiom Artis). Results: The equivalent CTDI measurement agreed with the conventional CTDI measurement within 8%. The discrepancy in themore » two measurements is largely attributed to uncertainties in cropping the waveform to a 180°acquisition. (Note: Because of the reduced fan angle in the CBCT, CTDI is not directly comparable to MDCT values when a 32 cm phantom is used.) Conclusion: The symmetry-based CTDI measurement is an equivalent measurement to the conventional CTDI measurement when the fan angle is large enough to encompass the phantom diameter. This allows a familiar metric of radiation output to be employed on systems with a limited angular rotation.« less

Authors:
 [1];  [2];  [3];  [4];  [5]
  1. Henry Ford Hospital, Detroit, MI (United States)
  2. Children’s National Medical Center, Washington, DC (United States)
  3. Radcal, Inc, Monrovia, CA (United States)
  4. New York Presbyterian Hospital, Tenafly, NJ (United States)
  5. Henry Ford Health System, Detroit, MI (United States)
Publication Date:
OSTI Identifier:
22626778
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; COMPUTERIZED TOMOGRAPHY; DIGITIZERS; PHANTOMS; PMMA; RADIATION DOSES; WAVE FORMS

Citation Formats

Singh, V, McKenney, S, Sunde, P, Feng, W, and Bakalyar, D. SU-F-I-05: Dose Symmetry for CTDI Equivalent Measurements with Limited Angle CBCT. United States: N. p., 2016. Web. doi:10.1118/1.4955833.
Singh, V, McKenney, S, Sunde, P, Feng, W, & Bakalyar, D. SU-F-I-05: Dose Symmetry for CTDI Equivalent Measurements with Limited Angle CBCT. United States. doi:10.1118/1.4955833.
Singh, V, McKenney, S, Sunde, P, Feng, W, and Bakalyar, D. Wed . "SU-F-I-05: Dose Symmetry for CTDI Equivalent Measurements with Limited Angle CBCT". United States. doi:10.1118/1.4955833.
@article{osti_22626778,
title = {SU-F-I-05: Dose Symmetry for CTDI Equivalent Measurements with Limited Angle CBCT},
author = {Singh, V and McKenney, S and Sunde, P and Feng, W and Bakalyar, D},
abstractNote = {Purpose: CTDI measurements, useful for characterizing the x-ray output for multi-detector CT (MDCT), require a 360° rotation of the gantry; this presents a problem for cone beam CT (CBCT) due to its limited angular rotation. The purpose of this work is to demonstrate a methodology for overcoming this limited angular rotation so that CTDI measurements can also be made on CBCT systems making it possible to compare the radiation output from both types of system with a common metric. Methods: The symmetry of the CTDI phantom allows a 360° CTDI measurement to be replaced with two 180° measurements. A pencil chamber with a real-time digitizer was placed at the center of the head phantom (16 cm, PMMA) and the resulting exposure measurement from a 180° acquisition was doubled. A pair of edge measurements, each obtained with the gantry passing through the same 180 arc, was obtained with the pencil chamber at opposite edges of the diameter of the phantom and then summed. The method was demonstrated on a clinical CT scanner (Philips, Brilliance6) and then implemented on an interventional system (Siemens, Axiom Artis). Results: The equivalent CTDI measurement agreed with the conventional CTDI measurement within 8%. The discrepancy in the two measurements is largely attributed to uncertainties in cropping the waveform to a 180°acquisition. (Note: Because of the reduced fan angle in the CBCT, CTDI is not directly comparable to MDCT values when a 32 cm phantom is used.) Conclusion: The symmetry-based CTDI measurement is an equivalent measurement to the conventional CTDI measurement when the fan angle is large enough to encompass the phantom diameter. This allows a familiar metric of radiation output to be employed on systems with a limited angular rotation.},
doi = {10.1118/1.4955833},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}