Our objective was to investigate the operating characteristics of tube current modulation (TCM) in computed tomography (CT) when scanning two types of simple-shaped phantoms. A tissueequivalent elliptical phantom and a homogeneous cylindrical step phantom comprising 16-, 24-, and 32-cm-diameter polymethyl methacrylate (PMMA) phantoms were scanned by using an automatic exposure control system with longitudinal (z-) and angular-longitudinal (xyz-) TCM and with a fixed tube current. The axial dose distribution throughout the elliptical phantom and the longitudinal dose distribution at the center of the cylindrical step phantom were measured by using a solid-state detector. Image noise was quantitatively measured at eight regions in the elliptical phantom and at 90 central regions in contiguous images over the full z extent of the cylindrical step phantom. The mean absorbed doses and the standard deviations in the elliptical phantom with z- and xyz-TCM were 12.3’ 3.7 and 11.3’ 3.5 mGy, respectively. When TCM was activated, some differences were observed in the absorbed doses of the left and the right measurement points. The average image noises in Hounsfield units (HU) and the standard deviations were 15.2’ 2.4 and 15.9’ 2.4 HU when using z- and xyz-TCM, respectively. With respect to the cylindrical step phantom under z-TCM, there were sudden decreases followed by increases in image noise at the interfaces with the 24- and 16-cm-diameter phantoms. The image noise of the 24-cm-diameter phantom was, relatively speaking, higher than those of the 16- and 32-cm-diameter phantoms. The simple-shaped phantoms used in this study can be employed to investigate the operating characteristics of automatic exposure control systems when specialized phantoms designed for that purpose are not available.
This is a preview of subscription content, access via your institution.
Buy single article
Instant access to the full article PDF.
Tax calculation will be finalised during checkout.
F. A. Mettler, Jr., B. R. Thomadsen, M. Bhargavan, D. B. Gilley, J. E. Gray, J. A. Lipoti, J. McCrohan, T. T. Yoshizumi and M. Mahesh. Health Phys. 95, 502 (2008).
National Council on Radiation Protection and Measurements (NCRP), NCRP Report No. 160, 2009.
D. Tack, V. De Maertelaer and P. A. Gevenois. AJR Am. J. Roentgenol. 181, 331 (2003).
M. Kalra, M. Maher, T. Toth, R. Kamath, E. Halpern and S. Saini. Radiology 232, 347 (2004).
E. Angel et al., AJR Am. J. Roentgenol. 193, 1340 (2009).
Y. Muramatsu, S. Ikeda, K. Osawa, R. Sekine, N. Niwa, M. Terada, N. Keat and S. Miyazaki, Nippon Hoshasen Gijutsu Gakkai Zasshi 63, 534 (2007).
A. E. Papadakis, K. Perisinakis and J. Damilakis. Med. Phys. 35, 4567 (2008).
M. Söderberg and M. Gunnarsson. Acta Radiol. 51, 625 (2010).
O. Rampado, F. Marchisio, A. Izzo, E. Garelli, C. C. Bianchi, G. Gandini and R. Ropolo, Eur. J. Radiol. 72, 181 (2009).
K. Matsubara, P. J. Lin, A. Fukuda and K. Koshida, Radiol. Phys. Technol. 7, 316 (2014).
I. A. Tsalafoutas, A. Varsamidis, S. Thalassinou and E. P. Efstathopoulos. Med. Phys. 40, 111918 (2013).
S. Sookpeng, C. J.Martin and D. J. Gentle. Radiat. Prot. Dosimetry 163, 521 (2015).
C. H. McCollough, M. R. Bruesewitz and J. M. Kofler, Jr., Radiographics 26, 503 (2006).
Discovery CT750 HD Technical Reference Manual, 5317222-1EN, Rev. 5, GE Healthcare (Waukesha, WI, USA, 2009).
L. Herrnsdorf, M. Björk, B. Cederquist, C. G. Mattsson, G. Thungström and C. Fröjdh, Nucl. Instrum. Meth. Phys. Res. Sect. A 607, 223 (2009).
J. H. Hubbell and S. M. Seltzer, Tables of X-ray mass attenuation coefficients and mass energy-absorption coefficients from 1 keV to 20 MeV for elements Z = 1 to 92 and 48 additional substances of dosimetric interest, Report NISTIR 5632. National Institute of Standards and Technology, Gaithersburg, MD, USA, 1996.
International Commission on Radiation Units and Measurements (ICRU), ICRP Report No. 44, 1989.
K. Matsubara, K. Koshida, M. Suzuki, H. Tsujii, T. Yamamoto and O. Matsui, Radiat. Prot. Dosimetry 128, 106 (2008).
M. Söderberg and M. Gunnarsson, Acta. Radiol. 51, 625 (2010).
About this article
Cite this article
Matsubara, K., Koshida, K., Lin, PJ.P. et al. Operating characteristics of tube-current-modulation techniques when scanning simple-shaped phantoms. Journal of the Korean Physical Society 67, 82–88 (2015). https://doi.org/10.3938/jkps.67.82
- Computed tomography
- Tube current modulation
- Image noise