Original paper| Volume 44, P227-231, December 2017

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Method for determining the half-value layer in computed tomography scans using a real-time dosimeter: Application to dual-source dual-energy acquisition

  • Kosuke Matsubara
    Corresponding author.
    Department of Quantum Medical Technology, Faculty of Health Sciences, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, Ishikawa 9200942, Japan
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  • Hiroji Nagata
    Section of Radiological Technology, Department of Medical Technology, Kanazawa Medical University Hospital, 1-1 Daigaku, Uchinada, Kahoku, Ishikawa 9200293, Japan
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  • Rena Okubo
    Department of Quantum Medical Technology, Graduate Course of Medical Science and Technology, Division of Health Sciences, Graduate School of Medical Science, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, Ishikawa 9200942, Japan
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  • Tadanori Takata
    Department of Radiological Technology, Kanazawa University Hospital, 13-1 Takaramachi, Kanazawa, Ishikawa 9208641, Japan
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  • Masanao Kobayashi
    Faculty of Radiological Technology, School of Health Sciences, Fujita Health University, 1-98 Dengakugakubo, Kutsukake, Toyoake, Aichi 4701192, Japan
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Published:October 27, 2017DOI:


      • A modified lead-covered case method can determines the half-value layers.
      • The method does not require X-ray tubes to be fixed during measurements.
      • The method can be applied to dual-source dual-energy computed tomography scans.
      • The peak method shows a more accurate half-value layer than the integrated method.
      • A combination of a 1.0-cm aperture of the case and the peak method is adequate.



      We have proposed a method for determining the half-value layers (HVL) in dual-source dual-energy computed tomography (DS-DECT) scans without the need for the X-ray tubes to be fixed.


      A custom-made lead-covered case and an ionizing chamber connected with a multi-function digitizer module (a real-time dosimeter) were used. The chamber was placed in the center of the case, and aluminum or copper filters were placed in front of the aperture. The HVL was measured using aperture widths of 1.0, 2.0, and 3.0 cm for tube potentials of 80, 120, and 150 kV in single-source single-energy CT (SS-SECT) scans and was calculated from the peak air kerma rate (peak method) and the integrated air kerma rate (integrating method); the obtained values were compared with those from a conventional non-rotating method performed using the same procedure. The HVL was then measured using an aperture width of 1.0 cm for tube potential combinations of 70/Sn150 kV and 100/Sn150 kV in DS-DECT scans using the peak method.


      In the SS-SECT scans, the combination of a 1.0-cm aperture and the peak method was adequate due to the small differences in the HVL values obtained for the conventional non-rotating method. The method was also found to be applicable for the DS-DECT scans.


      Our proposed method can determine the HVL in SS-SE and DS-DECT scans to a good level of accuracy without the need for the X-ray tubes to be fixed. The combination of a 1.0-cm aperture and the peak method was adequate.


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        • Kruger R.L.
        • McCollough C.H.
        • Zink F.E.
        Measurement of half-value layer in X-ray CT: a comparison of two noninvasive techniques.
        Med Phys. 2000; 27: 1915-1919
        • Nagashima H.
        • Sunaga S.
        • Mitome T.
        • Koya E.
        • Takei H.
        • Matsubara K.
        • et al.
        New method of estimating effective energy for X-ray CT scanners.
        Nihon Hoshasen Gijutsu Gakkai Zasshi. 2005; 61: 385-391
        • Maia A.F.
        • Caldas L.V.
        A simple method for evaluation of half-value layer variation in CT equipment.
        Phys Med Biol. 2006; 51: 1595-1601
        • Iida H.
        • Noto K.
        • Mitsui W.
        • Takata T.
        • Yamamoto T.
        • Matsubara K.
        New method of measuring effective energy using copper-pipe absorbers in X-ray CT.
        Nihon Hoshasen Gijutsu Gakkai Zasshi. 2011; 67: 1183-1191
        • Matsubara K.
        • Ichikawa K.
        • Murasaki Y.
        • Hirosawa A.
        • Koshida K.
        Accuracy of measuring half- and quarter-value layers and appropriate aperture width of a convenient method using a lead-covered case in X-ray computed tomography.
        J Appl Clin Med Phys. 2014; 15: 309-316
        • Kondo H.
        • Matsubara K.
        • Hirosawa A.
        • Koshida K.
        A comparison of several convenient methods of estimating effective energy in X-ray computed tomography.
        Nihon Hoshasen Gijutsu Gakkai Zasshi. 2014; 70: 453-460
        • Johnson T.R.
        Dual-energy CT: general principles.
        AJR Am J Roentgenol. 2012; 199: S3-S8
        • Zhang G.M.
        • Sun H.
        • Xue H.D.
        • Xiao H.
        • Zhang X.B.
        • Jin Z.Y.
        Prospective prediction of the major component of urinary stone composition with dual-source dual-energy CT in vivo.
        Clin Radiol. 2016; 71: 1178-1183
        • Li X.
        • Chen G.Z.
        • Zhao Y.E.
        • Schoepf U.J.
        • Albrecht M.H.
        • Bickford M.W.
        • et al.
        Radiation optimized dual-source dual-energy computed tomography pulmonary angiography: intra-individual and inter-individual comparison.
        Acad Radiol. 2017; 24: 13-21
        • Almeida I.P.
        • Schyns L.E.
        • Öllers M.C.
        • van Elmpt W.
        • Parodi K.
        • Landry G.
        • et al.
        Dual-energy CT quantitative imaging: a comparison study between twin-beam and dual-source CT scanners.
        Med Phys. 2017; 44: 171-179
        • McKenney S.E.
        • Seibert J.A.
        • Burkett G.W.
        • Gelskey D.
        • Sunde P.B.
        • Newman J.D.
        • et al.
        Real-time dosimeter employed to evaluate the half-value layer in CT.
        Phys Med Biol. 2014; 59: 363-377
        • Matscheko G.
        • Carlsson G.A.
        Measurement of absolute energy spectra from a clinical CT machine under working conditions using a Compton spectrometer.
        Phys Med Biol. 1989; 34: 209-222
      1. International Commission on Radiation Units and Measurements (ICRU) report 44: tissue substitutes in radiation dosimetry and measurement.
        ICRU, Bethesda1989
      2. International Commission on Radiation Units and Measurements (ICRU) report 46: photon, electron, proton and neutron interaction data for body tissues.
        ICRU, Bethesda1992
        • Mahesh M.
        MDCT physics: the basics—technology, image quality and radiation dose.
        Lippincott Williams & Wilkins, Philadelphia2009
        • Johnson T.R.
        • Krauss B.
        • Sedlmair M.
        • Grasruck M.
        • Bruder H.
        • Morhard D.
        • et al.
        Material differentiation by dual energy CT: initial experience.
        Eur Radiol. 2007; 17: 1510-1517
        • McKetty M.H.
        The AAPM/RSNA physics tutorial for residents. X-ray attenuation.
        Radiographics. 1998; 18: 151-163