Arnfield M R, Tulip J, Chetner M, McPhee M S
Department of Surgery, Cross Cancer Institute, Edmonton, Alberta, Canada.
Med Phys. 1989 Jul-Aug;16(4):602-8. doi: 10.1118/1.596361.
An approach to photodynamic treatment of tumors is the interstitial implantation of fiber optic light sources. Dosimetry is critical in identifying regions of low light intensity in the tumor which may prevent tumor cure. We describe a numerical technique for calculating light distributions within tumors, from multiple fiber optic sources. The method was tested using four translucent plastic needles, which were placed in a 0.94 X 0.94 cm grid pattern within excised Dunning R3327-AT rat prostate tumors. A cylindrical diffusing fiber tip, illuminated by 630 nm dye laser light was placed within one needle and a miniature light detector was placed within another. The average penetration depth in the tumor region between the two needles was calculated from the optical power measured by the detector, using a modified diffusion theory. Repeating the procedure for each pair of needles revealed significant variations in penetration depth within individual tumors. Average values of penetration depth, absorption coefficient, scattering coefficient, and mean scattering cosine were 0.282 cm, 0.469 cm-1, 250 cm-1 and 0.964, respectively. Calculated light distributions from four cylindrical sources in tumors gave reasonable agreement with direct light measurements using fiber optic probes.
一种肿瘤光动力治疗方法是光纤光源的间质植入。剂量测定对于识别肿瘤中可能妨碍肿瘤治愈的低光强区域至关重要。我们描述了一种用于计算来自多个光纤源的肿瘤内光分布的数值技术。该方法使用四根半透明塑料针进行测试，这些针以0.94×0.94厘米的网格模式放置在切除的邓宁R3327 - AT大鼠前列腺肿瘤内。将一根由630纳米染料激光照射的圆柱形漫射光纤尖端置于一根针内，一个微型光探测器置于另一根针内。利用修正的扩散理论，根据探测器测量的光功率计算两根针之间肿瘤区域的平均穿透深度。对每对针重复该过程揭示了单个肿瘤内穿透深度的显著变化。穿透深度、吸收系数、散射系数和平均散射余弦的平均值分别为0.282厘米、0.469厘米⁻¹、250厘米⁻¹和0.964。计算得到的肿瘤中四个圆柱形源的光分布与使用光纤探头的直接光测量结果合理吻合。
