微血管色素封装对体内漫反射光谱影响的实验验证
Experimental validation of the effects of microvasculature pigment packaging on in vivo diffuse reflectance spectroscopy.
作者信息
Rajaram Narasimhan, Gopal Ashwini, Zhang Xiaojing, Tunnell James W
机构信息
Department of Biomedical Engineering, The University of Texas at Austin, Austin, Texas 78712, USA.
出版信息
Lasers Surg Med. 2010 Sep;42(7):680-8. doi: 10.1002/lsm.20933.
BACKGROUND
Diffuse reflectance spectroscopy (DRS) uses the steady-state diffuse reflectance measured from the tissue surface to determine absorption and scattering properties of sampled tissue. Many inverse models used to determine absorber properties have assumed a homogeneous distribution of blood. However, blood in tissue is confined to blood vessels that occupy a small fraction of the overall volume. This simplified assumption can lead to large errors when measuring optical properties. The objective of this study was to examine the effect of confining absorbers to small volumes, such as the microvasculature, on in vivo DRS.
STUDY DESIGN
We fabricated multi-layer microfluidic devices to mimic blood vessels with a size similar to skin microvasculature. We studied the effect of varying channel size (diameter = 22 and 44 microm) and absorber concentration (10-80% food color dye in water) on diffuse reflectance measurements. We also examined the in vivo reflectance from normal skin and non-melanoma skin cancer on 14 patients.
RESULTS
Our results demonstrate that both absorption coefficient and vessel diameter affect the diffuse reflectance spectra. An empirically calculated packaging correction factor based on our experiments shows good agreement with previous theoretical derivations of the same factor. In vivo measurements on normal skin and basal cell carcinoma show that incorporating a correction factor greatly improves the fit of the inverse model to the spectra. In addition, there were statistically significant differences in measured mean vessel diameter and blood volume fraction between normal skin and basal cell carcinoma.
CONCLUSION
We have demonstrated experimentally the effect of pigment packaging in blood vessels over a physiologically relevant range of blood vessel size and absorption. The correction factors implemented to account for the packaging effect could potentially be used as diagnostic parameters for diagnosing skin cancers.
背景
漫反射光谱法（DRS）利用从组织表面测得的稳态漫反射来确定所采样组织的吸收和散射特性。许多用于确定吸收体特性的反演模型都假定血液呈均匀分布。然而，组织中的血液局限于仅占总体积一小部分的血管中。这种简化假设在测量光学特性时可能会导致较大误差。本研究的目的是检验将吸收体限制在小体积（如微脉管系统）中对活体DRS的影响。
研究设计
我们制作了多层微流控装置，以模拟尺寸与皮肤微脉管系统相似的血管。我们研究了不同通道尺寸（直径 = 22和44微米）和吸收体浓度（水中10 - 80%食用色素染料）对漫反射测量的影响。我们还检测了14名患者正常皮肤和非黑色素瘤皮肤癌的活体反射率。
结果
我们的结果表明，吸收系数和血管直径都会影响漫反射光谱。基于我们实验经验计算出的封装校正因子与先前对同一因子的理论推导结果吻合良好。对正常皮肤和基底细胞癌的活体测量表明，纳入校正因子可大大改善反演模型与光谱的拟合度。此外，正常皮肤和基底细胞癌之间在测量的平均血管直径和血容量分数上存在统计学显著差异。
结论
我们通过实验证明了在生理相关的血管尺寸和吸收范围内，血管中色素封装的影响。为考虑封装效应而实施的校正因子有可能用作诊断皮肤癌的诊断参数。
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