Chetty Indrin J, Charland Paule M
Department of Radiation Oncology, The University of Michigan, Ann Arbor 48109-0010, USA.
Phys Med Biol. 2002 Oct 21;47(20):3629-41. doi: 10.1088/0031-9155/47/20/305.
We have investigated the dependence of the measured optical density on the incident beam energy, field size and depth for a new type of film, Kodak extended dose range (Kodak EDR). Film measurements have been conducted over a range of field sizes (3 x 3 cm2 to 25 x 25 cm2) and depths (d(max) to 15 cm), for 6 MV and 15 MV photons within a solid water phantom, and the variation in sensitometric response (net optical density versus dose) has been reported. Kodak EDR film is found to have a linear response with dose, from 0 to 350 cGy, which is much higher than that typically seen for Kodak XV film (0-50 cGy). The variation in sensitometric response for Kodak EDR film as a function of field size and depth is observed to be similar to that of Kodak XV film; the optical density varied in the order of 2-3% for field sizes of 3 x 3 cm2 and 10 x 10 cm2 at depths of d(max), 5 cm and 15 cm in the phantom. Measurements for a 25 x 25 cm2 field size showed consistently higher optical densities at depths of d(max), 5 cm and 15 cm, relative to a 10 x 10 cm2 field size at 5 cm depth, with 4-5% differences noted at a depth of 15 cm. Fractional depth dose and profiles conducted with Kodak EDR film showed good agreement (2%/2 mm) with ion chamber measurements for all field sizes except for the 25 x 25 cm2 at depths greater than 15 cm, where differences in the order of 3-5% were observed. In addition, Kodak EDR film measurements were found to be consistent with those of Kodak XV film for all fractional depth doses and profiles. The results of this study indicate that Kodak EDR film may be a useful tool for relative dosimetry at higher dose ranges.
我们研究了一种新型胶片——柯达扩展剂量范围（Kodak EDR）胶片的测量光密度对入射束能量、射野大小和深度的依赖性。在固体水模体中，针对6兆伏和15兆伏光子，在一系列射野大小（3×3平方厘米至25×25平方厘米）和深度（最大深度至15厘米）范围内进行了胶片测量，并报告了感光响应（净光密度与剂量）的变化情况。发现柯达EDR胶片在0至350厘戈瑞的剂量范围内与剂量呈线性响应，这比柯达XV胶片（0 - 50厘戈瑞）通常所见的线性响应范围高得多。观察到柯达EDR胶片的感光响应随射野大小和深度的变化与柯达XV胶片相似；在模体中，对于3×3平方厘米和10×10平方厘米的射野大小，在最大深度、5厘米和15厘米深度处，光密度变化约为2 - 3%。对于25×25平方厘米的射野大小，在最大深度、5厘米和15厘米深度处的测量显示，相对于5厘米深度处10×10平方厘米的射野大小，光密度始终更高，在15厘米深度处差异为4 - 5%。使用柯达EDR胶片进行的百分深度剂量和剂量分布测量结果与电离室测量结果在除25×25平方厘米且深度大于15厘米以外的所有射野大小下均显示出良好的一致性（2%/2毫米），在该情况下观察到差异约为3 - 5%。此外，发现柯达EDR胶片测量结果在所有百分深度剂量和剂量分布方面与柯达XV胶片的测量结果一致。本研究结果表明，柯达EDR胶片可能是在较高剂量范围内进行相对剂量测定的有用工具。
