Chen Z, Yue N, Wang X, Roberts K B, Peschel R, Nath R
Department of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT 06504, USA.
Int J Radiat Oncol Biol Phys. 2000 Jul 15;47(5):1405-19. doi: 10.1016/s0360-3016(00)00549-6.
To derive a rigorous analytic solution to the dosimetric effects of prostate edema so that its impact on the conventional pre-implant and post-implant dosimetry can be studied for any given radioactive isotope and edema characteristics.
The edema characteristics observed by Waterman et al (Int. J. Rad. Onc. Biol. Phys, 41:1069-1077; 1998) was used to model the time evolution of the prostate and the seed locations. The total dose to any part of prostate tissue from a seed implant was calculated analytically by parameterizing the dose fall-off from a radioactive seed as a single inverse power function of distance, with proper account of the edema-induced time evolution. The dosimetric impact of prostate edema was determined by comparing the dose calculated with full consideration of prostate edema to that calculated with the conventional dosimetry approach where the seed locations and the target volume are assumed to be stationary.
A rigorous analytic solution on the relative dosimetric effects of prostate edema was obtained. This solution proved explicitly that the relative dosimetric effects of edema, as found in the previous numerical studies by Yue et. al. (Int. J. Radiat. Oncol. Biol. Phys. 43, 447-454, 1999), are independent of the size and the shape of the implant target volume and are independent of the number and the locations of the seeds implanted. It also showed that the magnitude of relative dosimetric effects is independent of the location of dose evaluation point within the edematous target volume. It implies that the relative dosimetric effects of prostate edema are universal with respect to a given isotope and edema characteristic. A set of master tables for the relative dosimetric effects of edema were obtained for a wide range of edema characteristics for both (125)I and (103)Pd prostate seed implants.
A rigorous analytic solution of the relative dosimetric effects of prostate edema has been derived for a class of edema characterized by Waterman et al. The solution proved that the dosimetric effects caused by the edema are universal functions of edema characteristics for a given isotope. It provides an efficient tool to examine the relative dosimetric effects of edema for any given edema characteristics and for any isotopes that may be considered for prostate implants.
推导前列腺水肿剂量学效应的精确解析解，以便针对任何给定的放射性同位素和水肿特征，研究其对传统植入前和植入后剂量学的影响。
采用沃特曼等人（《国际放射肿瘤学、生物学、物理学杂志》，41:1069 - 1077；1998年）观察到的水肿特征，对前列腺和籽源位置的时间演变进行建模。通过将来自放射性籽源的剂量衰减参数化为距离的单一反幂函数，并适当考虑水肿引起的时间演变，解析计算前列腺组织任何部分从籽源植入获得的总剂量。通过比较充分考虑前列腺水肿时计算的剂量与采用传统剂量学方法（假设籽源位置和靶体积固定）计算的剂量，确定前列腺水肿的剂量学影响。
获得了前列腺水肿相对剂量学效应的精确解析解。该解明确证明，岳等人（《国际放射肿瘤学、生物学、物理学杂志》，43, 447 - 454, 1999年）先前数值研究中发现的水肿相对剂量学效应，与植入靶体积的大小和形状无关，也与植入的籽源数量和位置无关。它还表明，相对剂量学效应的大小与水肿靶体积内剂量评估点的位置无关。这意味着对于给定的同位素和水肿特征，前列腺水肿的相对剂量学效应具有普遍性。针对¹²⁵I和¹⁰³Pd前列腺籽源植入，获得了一系列涵盖广泛水肿特征的水肿相对剂量学效应主表。
针对沃特曼等人所描述的一类水肿，推导了前列腺水肿相对剂量学效应的精确解析解。该解证明，对于给定的同位素而言，水肿引起的剂量学效应是水肿特征的通用函数。它为检查任何给定水肿特征以及任何可能用于前列腺植入的同位素的水肿相对剂量学效应提供了一种有效工具。
