Penumbral Dose Characteristics of Physical and Virtual Wedge Profiles

作     者：Salman Farrukh Nasir Ilyas Muhammad Naveed Abdul Haseeb Muhammad Bilal Dr Najamuddin Javed Iqbal 

作者机构：Atomic Energy Medical Centre JPMC Karachi Pakistan Institute of Space and Planetary Astrophysics University of Karachi Karachi Pakistan 

出 版 物：《International Journal of Medical Physics, Clinical Engineering and Radiation Oncology》 (医学物理学、临床工程、放射肿瘤学（英文）)

年 卷 期：2017年第6卷第2期

页      面：216-224页

学科分类：1002[医学-临床医学] 100214[医学-肿瘤学] 10[医学] 

主　　题：Physical Wedge Virtual Wedge Penumbra and Deviations 

摘      要：Purpose: Both physical and virtual wedges are used in radiotherapy to get uniform and desired dose distribution in clinical setting. All linear accelerators of different venders have computer controlled dynamic wedges called virtual wedge filters. Penumbra is one of the important photon beam characteristics needed to be understood in radiation therapy at the time of commissioning of Treatment Planning system (TPS) as well as applying various treatment planning algorithms in clinical applications. In this study we measured the dose profiles of open field, physical wedges (PW) and virtual wedges (VW) for energies (6 MV & 15 MV), various field sizes (10 × 10, 15 × 15 & 20 × 20 cm2), depths (dmax, 10 cm, 20 cm) and wedge angles (15°, 30°, 45° and 60°). From beam profile we calculated the penumbral width for open and wedged fields. The study was carried out on Siemens ONCOR IMRT Plus linear accelerator. The obtained penumbral width of PW and VW of all wedge angles was subtracted from the penumbral width of open field. The deviations in penumbral width were compared and statistically analyzed as a function of energy, depth, field size and wedge angles. Material and Method: The penumbral width was measured using IBA CC13 ion chamber in IBA Blue phantom (a 3D water phantom). The source to surface distance (SSD) during our study was kept 100cm and measurement was taken for 10 × 10, 15 × 15, 20 × 20 cm2 field sizes and for 15°, 30°, 45°, 60° wedges. These measurements were taken for both 6 MV and 15 MV photon energies. Virtual wedge profiles were acquired using LDA-99 linear detector array (IBA, Germany). The deviations in penumbral width for both PW and VW were calculated by subtracting the penumbral width from open field penumbral width in gun direction (in-plane) and deviation in VW penumbral width, and were obtained by subtracting the open field penumbral width in left-right direction (cross-plane) direction. The measured deviations were plotted for both PW and VW. Statis