Arnfield M R, Tulip J, McPhee M S
Department of Surgery, Cross Cancer Institute, Edmonton, Alberta, Canada.
Photochem Photobiol. 1990 Jun;51(6):667-74.
Dosimetry in photodynamic therapy as currently practiced is empirical in that it does not account for optical properties of the target lesion. However, since light attenuation in tissue is unpredictable, measurements of optical properties are needed to ensure optimal light dose delivery. Further improvements in the uniformity of light dose distribution in tumors can be afforded by implanting multiple light sources. A technique is described in which the use of multiple cylindrical sources was combined with measurements of light energy fluence rate in the tumor. Six sources were placed within translucent plastic needles, which were inserted into tumors in a parallel array. Tumor attenuation characteristics were measured by placing a miniature light detector in one needle, while illuminating a cylindrical source in another, nearby, needle. This process was repeated for different needle pairs. In one postmortem and two in vivo tumors the absorption coefficient, transport scattering coefficient and penetration depth ranged from 0.56-0.81 cm-1, 9.4-15.2 cm-1 and 1.7-2.3 mm, respectively. Apparent penetration depths for in vivo tumors changed with time, during experiments. Predictions of dosimetry were generally consistent with direct measurements of light in tumors. Somewhat better agreement was observed in an optical phantom.
目前光动力疗法中的剂量测定是经验性的，因为它没有考虑靶病变的光学特性。然而，由于组织中的光衰减不可预测，因此需要测量光学特性以确保最佳的光剂量传递。通过植入多个光源，可以进一步提高肿瘤内光剂量分布的均匀性。本文描述了一种技术，其中多个圆柱形光源的使用与肿瘤内光能注量率的测量相结合。六个光源放置在半透明塑料针内，这些针以平行阵列插入肿瘤中。通过将微型光探测器放置在一根针中，同时照亮附近另一根针中的圆柱形光源来测量肿瘤的衰减特性。对不同的针组重复此过程。在一个尸检肿瘤和两个活体肿瘤中，吸收系数、输运散射系数和穿透深度分别为0.56 - 0.81 cm⁻¹、9.4 - 15.2 cm⁻¹和1.7 - 2.3 mm。在实验过程中，活体肿瘤的表观穿透深度随时间变化。剂量测定的预测结果通常与肿瘤内光的直接测量结果一致。在光学模型中观察到的一致性稍好一些。
