Bill is right to push specular reflection well down the list of possible
hazards, for most clinical laser systems in use today, at least. Virtually
all of them use mildly divergent beams which lose their power rapidly over
shortish distances of a metre or two, and the power in the reflected beam
is only a small fraction of the incident power.
There could be a few exceptions to this, one of which we often use at Gloucester,
that of an unenclosed fibre with a microlens on the tip. This is fairly
safe to use under normal circumstances, for the reasons given above, but
the situation becomes different if the fibre is accidently sheared off,
and the end happens to be fairly flat. This could be similar to laboratory
accident circumstances (the site of most laser accidents), where coherent
parallel beams can be propagated over large distances.
The arrangement of the beam and the target site within the room will normally
safeguard those who might come into the theatre or look through the doors
briefly, and these can be incorporated into the local rules, as Bill says.
David Taylor, Clinical Scientist
Medical Physics Department
Gloucestershire Royal Hospital
Great Western Road, GLOUCESTER, GL1 3NN, UK.
+44 (0)1452 394189 tel, 394490 fax
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