Patel I, Glendinning A G, Kirby M C
North Western Medical Physics, Radiotherapy Department, Rosemere Cancer Centre, Royal Preston Hospital, UK.
Phys Med Biol. 2005 Dec 7;50(23):5479-92. doi: 10.1088/0031-9155/50/23/004. Epub 2005 Nov 8.
The dosimetric characteristics of a production pilot multi-leaf collimator (Elekta Beam Modulator, Elekta Oncology Systems, Crawley, UK) having a 4 mm leaf width (at isocentre) have been investigated. Characteristics explored included leaf bank set-up, penumbra width (80-20%) as a function of leaf position, leaf positioning reproducibility, interleaf leakage and leaf transmission. The penumbra values for leaf ends were measured to be between 4.2 and 4.8 mm for various large rectangular fields studied using Kodak X-omat V film at isocentre (1.5 cm deep). Similar films were taken with a standard 1 cm width multi-leaf collimator (MLC) and the penumbra for leaf ends was found to range from 4.3 to 5.2 mm. Other results showed that the rounded leaf tip provided tight control of the penumbra across the leaves' full range of travel. The positioning of the leaves was within a 0.5 mm range when approaching from the same direction. The maximum interleaf leakage was found to be 1.7% and the average leaf transmission less than 1.0%. No major differences were observed in leakage and transmission with changing gantry angle.
已对一款生产试用型多叶准直器（医科达射束调制器，医科达肿瘤系统公司，英国克劳利）的剂量学特性进行了研究，该多叶准直器在等中心处的叶片宽度为4毫米。所探究的特性包括叶片组设置、半值层宽度（80%-20%）随叶片位置的变化、叶片定位重复性、叶片间漏射及叶片透射。使用柯达X-omat V胶片在等中心（深度1.5厘米）对各种大的矩形射野进行研究，测得叶片末端的半值层值在4.2至4.8毫米之间。使用标准的1厘米宽度多叶准直器（MLC）拍摄了类似的胶片，发现叶片末端的半值层范围为4.3至5.2毫米。其他结果表明，圆形叶片尖端在叶片的整个行程范围内对半值层提供了精确控制。当从同一方向接近时，叶片的定位在0.5毫米范围内。发现最大叶片间漏射为1.7%，平均叶片透射率小于1.0%。随着机架角度的变化，在漏射和透射方面未观察到重大差异。
