ECE532 Biomedical Optics
© 1998 Steven L. Jacques, Scott A. Prahl
Oregon Graduate Institute

Time-resolved Monte Carlo

Relative concentration and fluence rate

In time-resolved Monte Carlo simulations, we record the time-resolved spatial distribution of photons expressed as either an energy concentration (C [J/cm³]) or an instantaneous fluence rate (F [W/cm²]) relative to the impulse energy (U_o [J]) of the source at time zero:

If one wishes to do bookkeeping of C as [photons cm^-3] or F as [photons cm^-2 s^-1], then one simply multiplies the Monte Carlo result, C/U_o or F/U_o, by the value of one's source expressed as number of photons, for example, a 1-J impulse at 532 nm wavelength:

U_o = (1 J) / ( hc/λ )

= (1 J) / ( (6.626x10^-34 Js)(2.998x10⁸ m/s) / (532x10^-9 m) )

= 2.7x10¹⁸ photons.

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