A method for conversion of Hounsfield number to electron density and prediction of macroscopic pair production cross-sections.

A method for the determination of electron density using a narrow beam attenuation geometry is described. The method does not require that the elemental composition of the phantom materials is known. The Hounsfield numbers for the phantom materials used were determined using five different CT scanners. A relationship between Hounsfield number and electron density can thus be established, which is of considerable value in radiation therapy treatment planning procedures. Measurements of the ratio coherent/incoherent scattering of low energy photons in a certain geometry has proven valuable for determination of atomic number, which in its turn can be used for estimation of macroscopic pair production coefficients for high energy photons. The combination of knowledge of electron density with methods for determination of processes, dependent on atomic number, can form a base for adequate composition of phantom materials for purposes of testing dose calculation algorithms for photons and electrons.

[1]  Lellery Storm,et al.  Photon cross sections from 1 keV to 100 MeV for elements Z=1 to Z=100 , 1970 .

[2]  K. B. Larson,et al.  Absorbed-Dose Computations For Inhomogeneous Media In Radiation-Treatment Planning Using Differential Scatter-Air Ratios , 1978 .

[3]  J. H. Hubbell,et al.  Photon cross sections, attenuation coefficients, and energy absorption coefficients from 10 keV to 100 GeV , 1969 .

[4]  M. E. Masterson,et al.  Epoxy-resin-based tissue substitutes. , 1977, Medical physics.

[5]  O. Klein,et al.  Über die Streuung von Strahlung durch freie Elektronen nach der neuen relativistischen Quantendynamik von Dirac , 1929 .

[6]  M. E. Young,et al.  Experimental tests of corrections for tissue inhomogeneities in radiotherapy. , 1970, The British journal of radiology.

[7]  D F Jackson,et al.  The relation between X-ray CT numbers and charged particle stopping powers and its significance for radiotherapy treatment planning. , 1983, Physics in medicine and biology.

[8]  J. H. Hubbell,et al.  Pair, Triplet, and Total Atomic Cross Sections (and Mass Attenuation Coefficients) for 1 MeV-100 GeV Photons in Elements Z=1 to 100, , 1980 .

[9]  Batho Hf,et al.  LUNG CORRECTIONS IN COBALT-60 BEAM THERAPY , 1964 .

[10]  M R Sontag,et al.  Corrections to absorbed dose calculations for tissue inhomogeneities. , 1977, Medical physics.

[11]  C. Orton.  Progress in medical radiation physics , 1982 .

[12]  M R Sontag,et al.  The equivalent tissue-air ratio method for making absorbed dose calculations in a heterogeneous medium. , 1978, Radiology.

[13]  A. H. Wapstra,et al.  Nuclear Data Tables , 1961 .