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Monte Carlo simulation of the effect of focal spot size on contrast-detail detectability

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Abstract

A contrast-detail experiment was simulated using Monte Carlo methods, to test the hypothesis that quantum limitations lead to an optimum minimum focal spot size below which no further improvement in image quality may be obtained. The simulation included a variable X-ray tube focal spot size, patient equivalent water phantom, X-ray couch, automatic exposure control, anti-scatter grid and indirect digital radiography detector. A number of simplifications were necessary in order to limit the calculation time to 8 days per image. Four images were produced for each focal spot size and these were scored by eight experienced observers. The contrast-detail curves were found to improve monotonically as focal spot size was reduced, with the best images produced by a point source. This contradicts the hypothesis of quantum limitation of focal spot size. We conclude that further work is required on the optimization of focal spot size. To assist with this, a new definition of system detective quantum efficiency is suggested, that includes the focal spot modulation transfer function, but does not include scattered radiation from the patient.

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Notes

  1. User applications for complex geometry are now much easier thanks to the relatively new C++ class libraries, Kawrakow, I., Mainegra-Hing, E., Tessier, F. and Walters, B.

    PIRS898, http://irs.inms.nrc.ca/software/egsnrc/documentation/pirs898/index.html.

References

  1. Wolbarst AB (2000) The physics of radiology. Medical Physics Publishing, Madison

    Google Scholar 

  2. Kratzat M (1990) Evaluating the importance of focal spot sizes in mammography. Medicamundi 33(2):74

    Google Scholar 

  3. Samei E, Ranger NT, Mackenzie A, Honey ID, Dobbins JT III, Ravin CE (2008) Detector or system? Extending the concept of DQE to characterize the performance of digital radiographic systems. Radiology 249(3):926–937

    Article  PubMed  Google Scholar 

  4. Poletti JL (2009) Optimisation of source to image distance in diagnostic radiology: a study using Monte Carlo simulation. VDM Verlag Dr. Müller, Saabrücken

    Google Scholar 

  5. Kawrakow I, Rogers DWO (2002) The EGSnrc code system: Monte Carlo simulation of electron and photon transport. National Research Council of Canada, Ottawa

    Google Scholar 

  6. Kawrakow I (2000) Accurate condensed history Monte Carlo simulation of electron transport. I. EGSnrc, the new EGS4 version. Med Phys 27:485–498

    Article  PubMed  CAS  Google Scholar 

  7. Kawrakow I, Mainegra-Hing E, Rogers DWO (2006) EGSnrcMP: the multi-platform environment for EGSnrc. National Research Council of Canada, Ottawa

    Google Scholar 

  8. Spelic DC, Kaczmarek RV, Suleiman OH (2004) Nationwide evaluation of X-ray trends survey of abdomen and lumbosacral spine radiography. Radiology 232:115–125

    Article  PubMed  Google Scholar 

  9. Chan H-P, Doi K (1982) Investigation of the performance of anti-scatter grids: Monte Carlo simulation studies. Phys Med Biol 27(6):785–803

    Article  PubMed  CAS  Google Scholar 

  10. Court L, Yamazaki T (2004) Technical note: a comparison of antiscatter grids for digital radiography. Br J Radiol 77(1–3):950–952

    Article  PubMed  CAS  Google Scholar 

  11. Samei E (2003) Image quality in two phosphor-based flat panel digital radiographic detectors. Med Phys 30(7):1747–1757

    Article  PubMed  Google Scholar 

  12. Arnold BA, Bjangard BE (1979) The effect of phosphor K X-rays on the MTF of rare-earth screens. Med Phys 6(6):500–503

    Article  PubMed  CAS  Google Scholar 

  13. Chan H-P, Doi K (1984) Physical characteristics of scattered radiation in diagnostic radiology: Monte Carlo simulation studies. Med Phys 12(2):152–165

    Article  Google Scholar 

  14. Chan H-P, Doi K (1983) The validity of Monte Carlo simulation in studies of scattered radiation in diagnostic radiology. Phys Med Biol 28(2):109–129

    Article  PubMed  CAS  Google Scholar 

  15. Poletti JL, McLean D (2004) The effect of source to image distance on scattered radiation to the image receptor. Australas Phys Eng Sci Med 27(4):180–188

    Article  PubMed  CAS  Google Scholar 

  16. Tucker DM, Barnes GT, Chakraborty DP (1991) Semiempirical model for generating tungsten target X-ray spectra. Med Phys 18(2):211–218

    Article  PubMed  CAS  Google Scholar 

  17. Caon M, Bibbo G, Pattison J, Bhat M (1998) The effect on dose to computed tomography phantoms of varying the theoretical X-ray spectrum: a comparison of four diagnostic X-ray spectrum calculating codes. Med Phys 25(6):1021–1027

    Article  PubMed  CAS  Google Scholar 

  18. International Electrotechnical Commission (1993) X-ray tube assemblies for medical diagnosis—characteristics of focal spots. International Electrotechnical Commission, Geneva

  19. Doi K, Loo L-N, Chan H-P (1992) X-ray tube focal spot sizes: comprehensive studies of their measurement and effect of measured size in angiography. Radiology 144(2):383–393

    Google Scholar 

  20. Doi K (1977) Field characteristics of geometric unsharpness due to the X-ray tube focal spot. Med Phys 4(1):15–20

    Article  PubMed  CAS  Google Scholar 

  21. Katz MC, Nickoloff EL (1992) Radiographic detail and variation of the nominal focal spot size: the “focal effect”. Radiographics 12(4):753–761

    PubMed  CAS  Google Scholar 

  22. Trajtenberg M (1984) The use of multivariate regression analysis in contrast-detail studies of CT scanners. Med Phys 11(4):456–464

    Article  PubMed  CAS  Google Scholar 

  23. Boone JM, Seibert JA (1997) An accurate method for computer-generating tungsten anode X-ray spectra from 30 to 140 kV. Med Phys 24(11):1661–1670

    Article  PubMed  CAS  Google Scholar 

  24. Lu ZF, Nickoloff EL, So JC, Dutta AK (2003) Comparison of computed radiography and film/screen combination using a contrast-detail phantom. J Appl Clin Med Phys 4(1):91–98

    Article  PubMed  CAS  Google Scholar 

  25. De Hauwere A, Bacher K, Smeets P, Verstraete K, Thierens H (2005) Analysis of image quality in digital chest imaging. Radiat Prot Dosim 117(1–3):174–177

    Google Scholar 

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Authors and Affiliations

  1. Department of Medical Imaging, Unitec New Zealand, Private Bag 92025, Auckland, New Zealand

    John Poletti

  2. IAEA, Vienna, Austria

    Donald McLean

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  1. John Poletti
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  2. Donald McLean
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Correspondence to John Poletti.

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Poletti, J., McLean, D. Monte Carlo simulation of the effect of focal spot size on contrast-detail detectability. Australas Phys Eng Sci Med 35, 41–48 (2012). https://doi.org/10.1007/s13246-011-0118-9

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  • DOI: https://doi.org/10.1007/s13246-011-0118-9

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