TUTORIALS IN RADIOTHERAPY PHYSICS by Patrick N. McDermott

Author:Patrick N. McDermott
Language: eng
Format: epub
Publisher: CRC Press

(3.37)

where:

Es is the energy of the scattered photon

(μen−s/ρ) is the mass energy absorption coefficient for the scattered photons

The dose at the observation point due to the scattering element is therefore

(3.38)

For a monoenergetic primary beam of energy E0, the terma is given by

(3.39)

Using Equations 3.31, 3.38, and 3.39, we can now write an expression for the scatter kernel (for singly scattered photons) in the homogeneous case:

(3.40)

where subscript sh refers to scattered photons in a homogeneous medium. The quantities Es, μen−s, and μs are functions of θ.

The scattering kernel in Equation 3.40 is of the form suggested by Ahnesjö (1989) (see Equation 3.29), where Bθ and bθ are functions of θ. Contour lines of the scattering kernel given by Equation 3.40 are plotted in Figure 3.10 for 1.25 MeV monoenergetic photons. It is assumed that

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