Porcine brain tissue is a model for human brain structures in laser induced thermo-therapy. However, its optical properties including possible heat-related changes were basically unknown so far. To simulate laser coagulation, 12 specimens (6 grey and 6 white matter) were heated in a saline bath (80°C, 2 hours) and compared to 11 untreated samples (5 grey and 6 white matter). The optical constants were obtained from transmission (total and collimated) and reflection (diffuse) measurements using the inverse Monte-Carlo method. The absorption coefficient ((mu) _a) of untreated grey substance decreased from 0.35 +/- 0.06/mm (340 nm) to 0.03 +/- 0.02/mm (800 nm). The scattering coefficient ((mu) _s) varied between 20.42 +/- 3.65/mm (340 nm) and 6.85 +/- 2.07/mm (800 nm). The anisotropy factor (g) increased from 0.848 +/- 0.013 (340 nm) to 0.889 +/- 0.009 (800 nm). Coagulation increased (mu) _a up to a factor of 2 (340-540 nm; p < 0.05), and (mu) _s by a factor up to 3 (340-800 nm, all data p < 0.001) while g was decreased up to 18% (340-560 nm; p < 0.05). White substance exhibited a (mu) _a between 0.24 +/- 0.07/mm (340 nm) and 0.04 +/- 0.02/mm (800 nm) while (mu) _s varied between 26.72 +/- 9.10/mm (340 nm) and 21.78 +/- 3.88/mm (800 nm). The g-value increased from 0.561 +/- 0.180 (340 nm) to 0.834 +/- 0.068 (800 nm). Coagulation increased (mu) _a by a factor up to 2 (340-800 nm; all data p < 0.05) while (mu) _s and g remained unchanged. Thermal denaturation changes the absorption and scattering properties of porcine brain significantly.

Date Published: 22 May 1995
PDF: 7 pages
Proc. SPIE 2391, Laser-Tissue Interaction VI, (22 May 1995); doi: 10.1117/12.209912

Published in SPIE Proceedings Vol. 2391:
Laser-Tissue Interaction VI
Steven L. Jacques, Editor(s)