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Choosing interaction site.
The probability that a photon interacts within dx after travelling a distance x is
μexp(-μx) so that:
Choosing interaction type.
Interaction type is a discrete
random variable of i values so that
P
i
=μ
i
/μ
total
.
So given r, I choose interaction j so that:
j= min{ j:
}
Figure from: Venselaar, Baltas, Meigooni, Hoskin
(Eds), Comprehensive Brachytehrapy: physical and
clinical aspects. CRC Press, Taylor & Francis, © 2013
The MC method …