Measurement of tissue optical properties in the 400 to 700 nm range to assess light penetration depths for laser treatment of upper tract urothelial carcinomas

Abstract

Significance: For therapeutic approaches for upper tract urothelial carcinomas, the absorption ${\mu }_a$ and reduced scattering ${\mu }_s^{\text{'}}$ coefficients of these tissues are essential parameters to quantitatively evaluate the distribution of light treatment effects.

Aim: The ${\mu }_a$ and ${\mu }_s^{\text{'}}$ spectra of the human ureter, fatty tissue, ureteral and renal pelvic carcinomas, and porcine ureter and fatty tissue are measured over 400 to 700 nm to evaluate projected light penetration depths $\delta$ .

Approach: The optical properties were determined with a double integrating sphere optical system and inverse Monte Carlo methods. $\delta$ was calculated and compared between normal and cancerous human tissues as well as between normal human and porcine tissues.

Results: ${\mu }_a$ and ${\mu }_s^{\text{'}}$ spectra of each tissue were determined. The $\delta$ of the normal human ureter was less than those of the ureteral and renal pelvic carcinomas, whereas that of the porcine ureter was similar to that of the human ureter over 400 to 600 nm and $\sim 0.2$ times smaller above 600 nm.

Conclusion: Optical properties of human and porcine upper urinary tracts provide insights into light distributions and the validity of ex vivo porcine models in preclinical evaluations of laser treatments.

Keywords: human tissue; laser treatment; light penetration depth; optical properties; upper tract urothelial carcinoma; upper urinary tract.

Fig. 1

Hematoxylin and eosin stained images of (a) normal ureter, (b) ureteral carcinoma, and (c) renal pelvic carcinoma. Scale bars: $300\mu \mathrm{m}$.

Fig. 2

Schematic of the double integrating sphere optical setup. A, aperture; IS, integrating sphere; L1, L2, L3, lenses; M1, M2, mirrors; S, sample.

Fig. 3

Absorption and reduced scattering coefficient spectra of human [(a), (c)] ureter and [(b), (d)] fatty tissue. The shaded areas represent standard deviations.

Fig. 4

Absorption and reduced scattering coefficient spectra of human [(a), (c)] ureteral carcinoma and [(b), (d)] renal pelvic carcinoma. The shaded areas represent standard deviations.

Fig. 5

Absorption and reduced scattering coefficient spectra of porcine (a), (c) ureter and (b), (d) fatty tissue. The shaded areas represent standard deviations.

Fig. 6

Comparison of projected light penetration depths between (a) human ureter and ureteral carcinoma, (b) human fatty tissue and ureteral carcinoma, (c) human ureter and renal pelvic carcinoma, and (d) human fatty tissue and renal pelvic carcinoma.

Fig. 7

Comparison of projected light penetration depths between (a) human and porcine ureters and (b) human and porcine fatty tissues.

Fig. 8

(a) Absorption; (b) reduced scattering coefficient spectra of human ureter obtained for $g=0.8$, 0.9, 0.95, and $n=1.4$; (c) absorption; and (d) reduced scattering coefficient spectra of human ureter obtained for $g=0.9$ and $n=1.3$, 1.4, and 1.5. The shaded areas represent standard deviations for $g=0.9$ and $n=1.4$.