Barajas O, Ballangrud A M, Miller G G, Moore R B, Tulip J
Department of Surgery, Cross Cancer Institute, Edmonton, Alberta, Canada.
Phys Med Biol. 1997 Sep;42(9):1675-87. doi: 10.1088/0031-9155/42/9/001.
Photodynamic therapy (PDT) is a promising technique for destroying tumours. Photosensitizing drugs presently available are not sufficiently tumour specific; hence, light dosimetry is required in order to control light exposure and thereby restrict cell kill to the target tissue to avoid damage to healthy tissue. Current light dosimetry methods rely on tissue optical characterization by fluence measurements at several points. Fluence-based tissue characterization is impractical for tumours in organs such as prostate where access by optical probes is limited and the tumours are highly optically inhomogeneous. This paper explores the potential of radiance-based light dosimetry as an alternative. Correlation is found between Monte Carlo simulation of radiance in a tissue phantom and radiance measurements made using a new radiance probe. Radiance is sensitive to variations in the tissue optical parameters, absorption coefficient mu(a), scattering coefficient mu(s), and anisotropy factor g, and therefore is potentially useful for tissue characterization. Radiance measurements have several advantages over fluence measurements. Radiance measurements provide more information from a single location, better spatial resolution of the tissue optical parameters, and higher sensitivity in discriminating between different media. However, the Monte Carlo method is too slow to be of practical value for tissue characterization by correlation of measured and simulated radiance. An analytical solution to the transport equation for radiance would be desirable as this would facilitate and increase the speed of tissue characterization.
光动力疗法（PDT）是一种很有前景的肿瘤治疗技术。目前可用的光敏药物对肿瘤的特异性不足；因此，需要进行光剂量测定，以控制光照射，从而将细胞杀伤限制在目标组织，避免对健康组织造成损伤。当前的光剂量测定方法依赖于通过在多个点测量通量来对组织进行光学表征。基于通量的组织表征对于前列腺等器官中的肿瘤来说并不实用，因为在这些器官中，光学探头的接入受限，而且肿瘤的光学性质高度不均匀。本文探讨了基于辐亮度的光剂量测定作为一种替代方法的潜力。在组织模型中辐亮度的蒙特卡罗模拟与使用新型辐亮度探头进行的辐亮度测量之间发现了相关性。辐亮度对组织光学参数、吸收系数μ(a)、散射系数μ(s)和各向异性因子g的变化敏感，因此有可能用于组织表征。辐亮度测量相对于通量测量具有多个优点。辐亮度测量能从单个位置提供更多信息、对组织光学参数具有更好的空间分辨率，并且在区分不同介质时具有更高的灵敏度。然而，蒙特卡罗方法对于通过测量辐亮度与模拟辐亮度的相关性来进行组织表征而言太慢，不具有实际价值。如果能得到辐亮度输运方程的解析解将是很理想的，因为这将便于并提高组织表征的速度。
