Vaarkamp J, Malde R, Dixit S, Hamilton C S
Radiation Physics, Princess Royal Hospital, Hull and East Yorkshire Hospitals NHS Trust, Hull, UK.
J Med Imaging Radiat Oncol. 2009 Jun;53(3):310-7. doi: 10.1111/j.1754-9485.2009.02078.x.
The aim of this article was to quantify improvements in external beam treatment plans for early prostate cancer, going from standard four-field conformal radiotherapy (CRT4) to multi-segment, inverse-planned intensity-modulated radiotherapy (IMRTinv). We selected 18 low-, medium- and high-risk early prostate cancer patients requiring external beam radiotherapy and generated standard CRT4 plans. We compared this with five-field conformal radiotherapy (CRT5) plans with beam angles 45 degrees, 100 degrees, 180 degrees, 260 degrees and 315 degrees, five-field plans combining an open beam and rectal shielding segment (forward-planned IMRT (IMRT(for))) and a five-field inverse-planned multi-segment solution (IMRT(inv)) with planning target volume and bladder dose volume histogram characteristics similar to IMRT(for). The CRT5 plans showed significant rectal sparing compared with CRT4 producing 10-22% reductions in rectal volume receiving 95, 85, 67 and 55% prescription dose (V(95), V(85), V(67) and V(55)) depending on patient risk group and conforming better to the planning target volume. The IMRT(for) plans showed a concave dose distribution, further reducing rectal V(95), V(85), V(67) and V(55) between 6 and 50%. We did not find further reductions in rectal doses with IMRT(inv) compared with IMRT(for). The benefit of IMRT over CRT was achieved by increasing the number of beams, changing beam weights and adding a rectal shielding segment to each beam.
本文旨在量化早期前列腺癌外照射治疗计划从标准的四野适形放疗（CRT4）到多段逆向计划调强放疗（IMRTinv）的改善情况。我们选取了18例需要外照射放疗的低、中、高危早期前列腺癌患者，并生成了标准的CRT4计划。我们将其与五野适形放疗（CRT5）计划进行比较，CRT5计划的射束角度为45度、100度、180度、260度和315度，还有结合了开放射束和直肠屏蔽段的五野计划（正向计划调强放疗（IMRT(for)））以及具有与IMRT(for)相似的计划靶体积和膀胱剂量体积直方图特征的五野逆向计划多段方案（IMRT(inv)）。与CRT4相比，CRT5计划显示出显著的直肠保护作用，根据患者风险组的不同，接受95%、85%、67%和55%处方剂量（V(95)、V(85)、V(67)和V(55)）的直肠体积减少了10% - 22%，并且与计划靶体积的符合度更好。IMRT(for)计划显示出凹形剂量分布，进一步使直肠V(95)、V(85)、V(67)和V(55)降低了6%至50%。与IMRT(for)相比，我们未发现IMRT(inv)能进一步降低直肠剂量。调强放疗相对于适形放疗的优势是通过增加射束数量、改变射束权重以及在每个射束上添加直肠屏蔽段来实现的。
