Petoukhova Anna L, Terhaard Chris H J, Welleweerd Hans
Department of Radiation Oncology, University Medical Center Utrecht, Utrecht, The Netherlands.
Radiother Oncol. 2006 May;79(2):203-7. doi: 10.1016/j.radonc.2006.04.002. Epub 2006 May 15.
The underdose near air cavities in the head and neck region at photon energies of 4 MV and 6 MV was studied in search for clinical advantages of the 4 MV over 6 MV treatments.
The on-axis and off-axis dose distributions were measured with a parallel-plate ionization chamber and films in polystyrene phantoms containing an air cavity of appropriate size based on the results of computed tomography scans.
Although most results are similar for both energies, the 4 MV photon beams give a somewhat smaller underdose effect and a faster re-build up than the 6 MV. For both energies a significant underdose effect was observed at the edge of the field in the larynx phantom. This proved to be true for small and large fields, for smaller and larger cavities, for one-beam as well as parallel-opposed beams.
For most clinically relevant situations there is no remarkable benefit in the use of either of the two energies.
研究了头部和颈部区域在4兆伏和6兆伏光子能量下靠近气腔处的剂量不足情况，以探寻4兆伏治疗相对于6兆伏治疗的临床优势。
根据计算机断层扫描结果，在含有适当尺寸气腔的聚苯乙烯体模中，使用平行板电离室和胶片测量了轴上和离轴剂量分布。
尽管两种能量下的大多数结果相似，但4兆伏光子束产生的剂量不足效应略小，且重建速度比6兆伏光子束快。对于两种能量，在喉部体模的射野边缘均观察到显著的剂量不足效应。对于小射野和大射野、较小和较大的气腔、单束以及对穿束，均证明如此。
对于大多数临床相关情况，使用这两种能量中的任何一种均无显著益处。
