van der Geld Ylanga G, Senan Suresh, van Sörnsen de Koste John R, Verbakel Wilko F A R, Slotman Ben J, Lagerwaard Frank J
Department of Radiation Oncology, VU University Medical Center, Amsterdam, The Netherlands.
Int J Radiat Oncol Biol Phys. 2007 Nov 1;69(3):903-9. doi: 10.1016/j.ijrobp.2007.06.062.
To evaluate three-dimensional conformal (3D-CRT), intensity-modulated (IMRT) and respiration-gated radiotherapy (RGRT) techniques for gastric irradiation for target coverage and minimization of renal doses. All techniques were four-dimensional (4D)-CT based, incorporating the intrafractional mobility of the target volume and organs at risk (OAR).
The stomach, duodenal C-loop, and OAR (kidneys, liver, and heart) were contoured in all 10 phases of planning 4D-CT scans for five patients who underwent abdominal radiotherapy. Planning target volumes (PTVs) encompassing all positions of the stomach (PTV(all phases)) were generated. Three respiratory phases for RGRT in inspiration and expiration were identified, and corresponding PTV(inspiration) and PTV(expiration) and OAR volumes were created. Landmark-based fields recommended for the Radiation Therapy Oncology Group (RTOG) 99-04 study protocol were simulated to assess PTV coverage. IMRT and 3D-CRT planning with and without additional RGRT planning were performed for all PTVs, and corresponding dose volume histograms were analyzed.
Use of landmark-based fields did not result in full geometric coverage of the PTV(all phases) in any patient. IMRT significantly reduced mean renal doses compared with 3D-CRT (15.0 Gy +/- 0.9 Gy vs. 20.1 Gy +/- 9.3 Gy and 16.6 Gy +/- 1.5 Gy vs. 32.6 Gy +/- 7.1 Gy for the left and right kidneys, respectively; p = 0.04). No significant increase in renal sparing was seen when adding RGRT to either 3D-CRT or IMRT. Tolerance doses to the other OAR were not exceeded.
Individualized field margins are essential for gastric irradiation. IMRT plans significantly reduce renal doses, but the benefits of RGRT in gastric irradiation appear to be limited.
评估三维适形放疗（3D-CRT）、调强放疗（IMRT）和呼吸门控放疗（RGRT）技术在胃部照射中对靶区的覆盖情况以及肾脏剂量的最小化。所有技术均基于四维（4D）-CT，纳入了靶区体积和危及器官（OAR）的分次内移动性。
对5例接受腹部放疗的患者的所有10个计划4D-CT扫描期相进行胃部、十二指肠C袢和OAR（肾脏、肝脏和心脏）的轮廓勾画。生成包含胃部所有位置的计划靶区（PTV）（PTV（所有期相））。确定了RGRT在吸气和呼气时的三个呼吸期相，并创建了相应的PTV（吸气）和PTV（呼气）以及OAR体积。模拟了放射治疗肿瘤学组（RTOG）99-04研究方案推荐的基于标志物的射野，以评估PTV覆盖情况。对所有PTV进行了有无额外RGRT计划的IMRT和3D-CRT计划，并分析了相应的剂量体积直方图。
使用基于标志物的射野在任何患者中均未实现PTV（所有期相）的完全几何覆盖。与3D-CRT相比，IMRT显著降低了平均肾脏剂量（左肾分别为15.0 Gy±0.9 Gy vs. 20.1 Gy±9.3 Gy，右肾为16.6 Gy±1.5 Gy vs. 32.6 Gy±7.1 Gy；p = 0.04）。在3D-CRT或IMRT中添加RGRT时，未观察到肾脏保护有显著增加。其他OAR的耐受剂量未被超过。
个体化的射野边界对于胃部照射至关重要。IMRT计划显著降低了肾脏剂量，但RGRT在胃部照射中的益处似乎有限。
