Treuer Harald, Kocher Martin, Hoevels Moritz, Hunsche Stefan, Luyken Klaus, Maarouf Mohammad, Voges Jürgen, Müller Rolf-Peter, Sturm Volker
Department of Stereotaxy and Functional Neurosurgery, University of Cologne, Germany.
Radiother Oncol. 2006 Oct;81(1):25-32. doi: 10.1016/j.radonc.2006.08.022. Epub 2006 Sep 26.
Determination of the impact of inaccuracies in the determination and setup of the target point in stereotactic radiosurgery (SRS) on the expectable complication and control probabilities.
Two randomized samples of patients with arteriovenous malformation (AVM) (n=20) and with brain metastases (n=20) treated with SRS were formed, and the probability for complete obliteration (COP) or complete remission (CRP), the size of the 10 Gy-volume in the brain tissue (VOI10), and the probability for radiation necrosis (NTCP) were calculated. The dose-effect relations for COP and CRP were fitted to clinical data. Target point deviations were simulated through random vectors and the resulting probabilities and volumes were calculated and compared with the values of the treatment plan.
The decrease of the relative value of the control probabilities at 1mm target point deviation was up to 4% for AVMs and up to 10% for metastases. At 2 mm the median decrease was 5% for AVMs and 9% for metastases. The value for the target point deviation, at which COP and CRP decreased about 0.05 in 90% of the cases, was 1.3 mm. The increase of NTCP was maximally 0.0025 per mm target point deviation for AVMs and 0.0035/mm for metastases. The maximal increase of VOI10 was 0.7 cm(3)/mm target point deviation in both patient groups.
The upper limit for tolerable target point deviations is at 1.3mm. If this value cannot be achieved during the system test, a supplementary safety margin should be applied for the definition of the target volume. A better accuracy level is desirable, in order to ensure optimal chances for the success of the treatment. The target point precision is less important for the minimization of the probability of radiation necroses.
确定立体定向放射外科治疗（SRS）中靶点确定和设置不准确对预期并发症及控制概率的影响。
形成两个接受SRS治疗的随机样本，分别为患有动静脉畸形（AVM）的患者（n = 20）和患有脑转移瘤的患者（n = 20），计算完全闭塞概率（COP）或完全缓解概率（CRP）、脑组织中10 Gy体积（VOI10）的大小以及放射性坏死概率（NTCP）。将COP和CRP的剂量效应关系拟合到临床数据。通过随机向量模拟靶点偏差，并计算由此产生的概率和体积，然后与治疗计划的值进行比较。
靶点偏差1mm时，AVM的控制概率相对值下降高达4%，转移瘤高达10%。2mm时，AVM的中位数下降为5%，转移瘤为9%。在90%的病例中，COP和CRP下降约0.05时的靶点偏差值为1.3mm。对于AVM，NTCP每毫米靶点偏差最大增加0.0025，对于转移瘤为0.0035/mm。两组患者中VOI10的最大增加均为每毫米靶点偏差0.7 cm³。
可耐受的靶点偏差上限为1.3mm。如果在系统测试期间无法达到该值，则应在定义靶体积时应用额外的安全裕度。为确保治疗成功的最佳机会，需要更高的精度水平。靶点精度对于将放射性坏死概率降至最低不太重要。
