Physical Background

Part of the Medical Radiology book series (MEDRAD)


There had been attempts to utilize spectral information for tissue characterization soon after the invention of Computed Tomography, but only recently Dual Energy CT has achieved a significant role in clinical radiology.

To perform Dual Energy CT, it is necessary to generate x-rays with different energies, mostly as polychromatic spectra. On the other hand, the detector has to be capable to differentiate x-ray quanta of different energies. There are four technical approaches to meet these requirements, of which the Dual Source CT, the rapid voltage switching and the layer detector technology are available or being implemented.

To obtain relevant diagnostic information, there have to be substances with spectral properties which reflect the pathology by their presence or distribution. Most important is the photoelectric effect of elements like uric acid, iron, calcium, iodine or xenon gas, which are present in pathological structures or can be administered as contrast material. The identification and quantification of these elements can be used to diagnose several diseases.


Tube Voltage Hardware Effort Layer Detector Lower Energy Spectrum Tungsten Anode 


  1. Alvarez RE, Macovski A (1976) Energy-selective reconstructions in X-ray computerized tomography. Phys Med Biol 21:733–744PubMedCrossRefGoogle Scholar
  2. Avrin DE, Macovski A, Zatz LE (1978) Clinical application of Compton and photo-electric reconstruction in computed tomography: preliminary results. Invest Radiol 13:217–222PubMedCrossRefGoogle Scholar
  3. Cann CE, Gamsu G, Birnberg FA, Webb WR (1982) Quantification of calcium in solitary pulmonary nodules using single- and dual-energy CT. Radiology 145:493–496PubMedGoogle Scholar
  4. Chae EJ, Seo JB, Goo HW et al (2008) Xenon ventilation CT with a dual-energy technique of dual-source CT: initial experience. Radiology 248:615–624PubMedCrossRefGoogle Scholar
  5. Chiro GD, Brooks RA, Kessler RM et al (1979) Tissue signatures with dual-energy computed tomography. Radiology 131:521–523PubMedGoogle Scholar
  6. Flohr TG, McCollough CH, Bruder H et al (2006) First performance evaluation of a dual-source CT (DSCT) system. Eur Radiol 16:256–268PubMedCrossRefGoogle Scholar
  7. Genant HK, Boyd D (1977) Quantitative bone mineral analysis using dual energy computed tomography. Invest Radiol 12:545–551PubMedCrossRefGoogle Scholar
  8. Graser A, Johnson TR, Bader M et al (2008) Dual energy CT characterization of urinary calculi: initial in vitro and clinical experience. Invest Radiol 43:112–119PubMedCrossRefGoogle Scholar
  9. Graser A, Johnson TR, Hecht EM et al (2009) Dual-energy CT in patients suspected of having renal masses: can virtual nonenhanced images replace true nonenhanced images? Radiology 252:433–440PubMedCrossRefGoogle Scholar
  10. Grasruck M, Kappler S, Reinwand M, Stierstorfer K (2009) Dual energy with dual source CT and kVp switching with single source CT: a comparison of dual energy performance. Proc SPIE 7258:72583RCrossRefGoogle Scholar
  11. Ho LM, Yoshizumi TT, Hurwitz LM et al (2009) Dual energy versus single energy MDCT: measurement of radiation dose using adult abdominal imaging protocols. Acad Radiol 16:1400–1407PubMedCrossRefGoogle Scholar
  12. Holmes DR III, Fletcher JG, Apel A et al (2008) Evaluation of non-linear blending in dual-energy computed tomography. Eur J Radiol 68:409–413PubMedCrossRefGoogle Scholar
  13. Johnson TR, Krauss B, Sedlmair M et al (2007a) Material differentiation by dual energy CT: initial experience. Eur Radiol 17:1510–1517PubMedCrossRefGoogle Scholar
  14. Johnson TR, Weckbach S, Kellner H, Reiser MF, Becker CR (2007b) Clinical image: dual-energy computed tomographic molecular imaging of gout. Arthritis Rheum 56:2809PubMedCrossRefGoogle Scholar
  15. Kappler S, Grasruck M, Niederloehner D, Strassburg M, Wirth S (2009) Dual-energy performance of dual kVp in comparison to dual-layer and quantum-counting CT system concepts. Proc SPIE 7258:725842CrossRefGoogle Scholar
  16. Kelcz F, Joseph PM, Hilal SK (1979) Noise considerations in dual energy CT scanning. Med Phys 6:418–425PubMedCrossRefGoogle Scholar
  17. Kruger RA, Riederer SJ, Mistretta CA (1977) Relative properties of tomography, K-edge imaging, and K-edge tomography. Med Phys 4:244–249PubMedCrossRefGoogle Scholar
  18. Li B, Yadava G, Hsieh J (2010) Head and body CTDIw of dual energy x-ray CT with fast-kVp switching. In: SPIE Medical Imaging, San Diego, CA, paper 7622–7669Google Scholar
  19. McCullough EC (1975) Photon attenuation in computed tomography. Med Phys 2:307–320PubMedCrossRefGoogle Scholar
  20. Michael GJ (1992) Tissue analysis using dual energy CT. Australas Phys Eng Sci Med 15:75–87PubMedGoogle Scholar
  21. Millner MR, McDavid WD, Waggener RG, Dennis MJ, Payne WH, Sank VJ (1979) Extraction of information from CT scans at different energies. Med Phys 6:70–71PubMedCrossRefGoogle Scholar
  22. Morhard D, Fink C, Graser A, Reiser MF, Becker C, Johnson TR (2009) Cervical and cranial computed tomographic angiography with automated bone removal: dual energy computed tomography versus standard computed tomography. Invest Radiol 44:293–297PubMedCrossRefGoogle Scholar
  23. Nakayama Y, Awai K, Funama Y et al (2005) Abdominal CT with low tube voltage: preliminary observations about radiation dose, contrast enhancement, image quality, and noise. Radiology 237:945–951PubMedCrossRefGoogle Scholar
  24. Riederer SJ, Mistretta CA (1977) Selective iodine imaging using K-edge energies in computerized x-ray tomography. Med Phys 4:474–481PubMedCrossRefGoogle Scholar
  25. Schenzle JC, Sommer WH, Neumaier K et al (2010) Dual energy CT of the chest: how about the dose? Invest Radiol 45:347–353Google Scholar
  26. Sommer WH, Johnson TR, Becker CR et al (2009) The value of dual-energy bone removal in maximum intensity projections of lower extremity computed tomography angiography. Invest Radiol 44:285–292PubMedCrossRefGoogle Scholar
  27. Svendsen OL, Hassager C, Bergmann I, Christiansen C (1993) Measurement of abdominal and intra-abdominal fat in postmenopausal women by dual energy X-ray absorptiometry and anthropometry: comparison with computerized tomography. Int J Obes Relat Metab Disord 17:45–51PubMedGoogle Scholar
  28. Thieme SF, Becker CR, Hacker M, Nikolaou K, Reiser MF, Johnson TR (2008) Dual energy CT for the assessment of lung perfusion–correlation to scintigraphy. Eur J Radiol 68:369–374PubMedCrossRefGoogle Scholar
  29. Thieme SF, Johnson TR, Lee C et al (2009) Dual-energy CT for the assessment of contrast material distribution in the pulmonary parenchyma. AJR Am J Roentgenol 193:144–149PubMedCrossRefGoogle Scholar
  30. Voit H, Krauss B, Heinrich MC et al (2009) Dual-source CT: in vitro characterization of gallstones using dual energy analysis. Rofo 181:367–373PubMedCrossRefGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2011

Authors and Affiliations

  1. 1.Department of Clinical RadiologyUniversity of Munich, Grosshadern HospitalMunichGermany
  2. 2.Institute of Medical PhysicsUniversity of ErlangenErlangenGermany

Personalised recommendations