AbstractID: 7628 Title: Radius and depth dependence of light in turbid medium for wavelengths between
532-730nm
For collimated laser light with finite radius, the light fluence at tissue surface and its penetration depth are dependent on the radius. In
this study, depth and radius dependence of laser under uniform light irradiation with λ (532, 630 and 730 nm) was measured in 0.5, 1
and 1.5 % intralipid, a tissue simulating medium. The fluence rate was measured by a 1-mm diameter isotropic detector, with
scattering tip, for circular fields with radii of 0.5, 1, 2, 3, 4, 6 and 11.8 cm at phantom surface. The half-value layer (HVL), defined as
the depth where fluence rate is 50% of that at d = 0 cm, increases for a fixed wavelength with the field size (from 3.1 cm for the 0.5
cm field size to 7.4 cm for the largest field size for 730 nm). For diameter larger than 5 cm the HVL doesn’t change significantly
(there is a 1% change when the diameter doubles from 6 cm to 12 cm). Depth of maximum dose decreases significantly for field
radius less than 0.5 cm for all wavelengths. The fluence rate, at a fixed depth (d = 0 cm), increases with field sizes from 0.6 to 1.0 for
field radius 0.5 to 11.8 cm, for all wavelengths, and saturates for field sizes larger than 2.5 cm in radius. Monte-Carlo simulations are
performed to analyze the results.