Furuya Tomohisa, Lee Young K, Archibald-Heeren Ben R, Byrne Mikel, Bosco Bruno, Phua Jun H, Shimizu Hidetoshi, Hashimoto Shimpei, Tanaka Hiroshi, Sahgal Arjun, Karasawa Katsuyuki
Department of Radiology, Tokyo Metropolitan Cancer and Infectious Diseases Center Komagome Hospital, 1138677 Tokyo, Japan.
Department of Radiation Oncology, Sunnybrook Odette Cancer Center, University of Toronto, M4N 3M5 Toronto, Ontario, Canada.
Phys Imaging Radiat Oncol. 2020 Oct 14;16:61-68. doi: 10.1016/j.phro.2020.09.005. eCollection 2020 Oct.
Post-operative spine stereotactic body radiation therapy (SBRT) represents a significant challenge as there are many restrictions on beam geometry to avoid metal hardware as it surrounds the target volume. In this study, an international multi-institutional end-to-end test using an in-house spine phantom was developed and executed. The aim was to evaluate the impact of titanium spine hardware on planned and delivered dose for post-operative spine SBRT.
Five centers performed simulation, planning and irradiation of the spine phantom, with/without titanium metal hardware (MB/B), following our pre-specified protocol. The doses were calculated using the centers' treatment planning system (TPS) and measured with radiophotoluminescent glass dosimeters (RPLDs) embedded within each phantom.
The dose differences between the RPLD measured and calculated doses in the target region were within ± 5% for both phantoms studied. Differences greater than 5% were observed for the spinal cord and the out-of-the target regions due to steeper dose gradient regions that are created in these plans. Dose measurements within ± 3% were observed between RPLDs that were embedded in MB and B inserts. For the spinal cord and the out-of-target regions surrounded by metal hardware, the dose measured using RPLDs was within 3% different near the titanium screws compared to the dose measured near only the metal rods.
We have successfully performed the first multi-institutional end-to-end dose analysis using an in-house phantom built specifically for post-operative spine SBRT. The differences observed between the measured and planned doses in the presence of metal hardware were clinically insignificant.
术后脊柱立体定向体部放疗（SBRT）是一项重大挑战，因为在射束几何形状方面存在诸多限制，以避免金属植入物，因为它环绕着靶区。在本研究中，开发并实施了一项使用内部脊柱体模的国际多机构端到端测试。目的是评估钛制脊柱植入物对术后脊柱SBRT计划剂量和实际交付剂量的影响。
五个中心按照我们预先指定的方案，对带有/不带有钛金属植入物（MB/B）的脊柱体模进行模拟、计划和照射。使用各中心的治疗计划系统（TPS）计算剂量，并使用嵌入每个体模内的放射性光致发光玻璃剂量计（RPLD）进行测量。
对于所研究的两种体模，靶区内RPLD测量剂量与计算剂量之间的差异均在±5%以内。由于这些计划中创建的剂量梯度较陡的区域，在脊髓和靶区外区域观察到大于5%的差异。在MB和B插入物中嵌入的RPLD之间观察到±3%以内的剂量测量差异。对于被金属植入物包围的脊髓和靶区外区域，与仅在金属棒附近测量的剂量相比，使用RPLD测量的剂量在钛螺钉附近相差3%以内。
我们成功地使用专门为术后脊柱SBRT构建的内部体模进行了首次多机构端到端剂量分析。在存在金属植入物的情况下，测量剂量与计划剂量之间观察到的差异在临床上无显著意义。
