Norrgård F S, Sipilä P M, Kulmala J A, Minn H R
Department of Oncology and Radiotherapy, University of Turku, Finland.
Phys Med Biol. 1998 Jun;43(6):1545-56. doi: 10.1088/0031-9155/43/6/013.
Dose characteristics of a stereotactic radiotherapy unit based on a standard Varian Clinac 4/100 4 MV linear accelerator, in-house-built Lipowitz collimators and the SMART stereotactic radiotherapy treatment planning software have been determined. Beam collimation is constituted from the standard collimators of the linear accelerator and a tertiary collimation consisting of a replaceable divergent Lipowitz collimator. Four collimators with isocentre diameters of 15, 25, 35 and 45 mm, respectively, were constructed. Beam characteristics were measured in air, acrylic or water with ionization chamber, photon diode, electron diode, diamond detector and film. Monte Carlo simulation was also applied. The radiation leakage under the collimators was less than 1% at 50 mm depth in water. Specific beam characteristics for each collimator were imported to SMART and dose planning with five non-coplanar converging 140 degrees arcs separated by 36 degrees angles was performed for treatment of a RANDO phantom. Dose verification was made with TLD and radiochromic film. The in-house-built collimators were found to be suitable for stereotactic radiotherapy and patient treatments with this system are in progress.
基于标准瓦里安Clinac 4/100 4兆伏直线加速器、自制的利波维兹准直器和SMART立体定向放射治疗治疗计划软件的立体定向放射治疗设备的剂量特性已被确定。束流准直由直线加速器的标准准直器和由可更换的发散型利波维兹准直器组成的三级准直构成。构建了四个等中心直径分别为15、25、35和45毫米的准直器。使用电离室、光子二极管、电子二极管、金刚石探测器和胶片在空气、丙烯酸或水中测量束流特性。还应用了蒙特卡罗模拟。在水中50毫米深度处，准直器下方的辐射泄漏小于1%。将每个准直器的特定束流特性输入到SMART中，并对RANDO体模进行治疗，采用五个非共面会聚140度弧，间隔36度角进行剂量规划。使用热释光剂量计和放射变色胶片进行剂量验证。发现自制的准直器适用于立体定向放射治疗，使用该系统的患者治疗正在进行中。
