Comment on "Excitation with a focused, pulsed optical beam in scattering media: diffraction effects".

To incorporate the wave properties of light, it was recently proposed to modify the Monte Carlo-based photon transport model to a semi-quantum-mechanical representation by considering each ray as a photon wave packet [Appl. Opt. 39, 5244 (2000)]. It is not clear from the paper whether each photon wave packet is considered representative of an entire plane wave or if each is spatially localized. However, for each interpretation we identify problems with the approach suggested for combining the wave-packet contributions. These include violation of the principle of conservation of energy and the use of a scattering phase function that is incompatible with the suggested way of calculating the intensity values. These issues render the approach impractical.