![]() 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). ![]() Research has also focused on the influence of scatter on the film sensitometric response, caused by changing the field size and depth of the measurement (Williamson et al 1981, Evans and Schreiner 1992, Hale et al 1994, van Bree et al 1994, van Battum and Heijmen 1995, Cheng and Das 1996, Burch et al 1997, Cadman 1998, Robar and Clark 1999, Suchowerska et al 1999, Sykes et al 1999, Danciu et al 2001. Several investigators have reported on differences in film response when the film is positioned parallel versus perpendicular to the radiation beam (Williamson et al 1981, Cheng and Das 1996, Burch et al 1997, Robar and Clark 1999, Suchowerska et al 1999, Danciu et al 2001. Studies since the early 1980s have shown that the response of film (optical density versus dose) is sensitive to many factors, such as the photon beam energy, the film orientation relative to the beam direction, air pockets within the film envelope, processing conditions and readout method, as well as intra-and inter-film variation in crystal sizes and orientation. The limited field size and depth dependence of sensitometric data measured using EDR2 film, along with the inherently wide linear dose-response range of EDR2 film, makes it better suited to the verification of IMRT dose distributions. For the larger field size, the sensitometric curve for EDR2 film is superior to XV film in regions where the dose falls below 20% of the central axis dose, due to the effects that the increased low energy scattered photon contributions have on film response. For a field size of 4x4 cm2, a single sensitometric curve for either EDR2 and XV film can be used for the determination of relative dose profiles. For the combinations of photon beam energy, depth, and field size investigated here, our results indicate that the sensitometric curves are nearly independent of field size and depth of calibration. This analysis involved the determination of sensitometric curves for XV and EDR2 films, the determination of dose profiles from exposed XV and EDR2 films, and comparison of the film-generated dose profiles to ionization chamber measurements. The dose responses of both film types to 6 MV and 18 MV photon beams were investigated for depths of 5 cm, 10 cm, and 15 cm and field sizes of 4x4 cm2 and 15x15 cm2. The dosimetric properties of the recently developed Kodak EDR2 film were investigated and compared to those of Kodak XV film. However, the photon energy response of film is known to be a function of depth, field size, and photon beam energy, potentially reducing the accuracy of dose distribution measurements. ![]() High resolution, two-dimensional dose distributions can be measured using radiographic film. Good dosimetric results can be obtained if films from the same batch are irradiated with small to moderate field sizes (up to about 15 cm x 15 cm), at moderate depths (up to about 15 cm), using a single calibration curve, e.g., for a 10 cm x 10 cm field.įor intensity modulated radiation therapy (IMRT) dose distribution verification, multidimensional measurements are required to quantify the steep dose-gradient regions. For Co-60 and for the same dose, the Kodak and Agfa films gave at dose maximum an OD lower by 4% and 6%, respectively, for the parallel compared to the perpendicular geometry. The sensitometric curves of both types of film are almost independent of the film plane orientation, except for shallow depths. The slope of the sensitometric curve of the Agfa film is somewhat more dependent on photon beam energy, depth and field size. For the Kodak film the differences in OD with depth are less than 2%, except for the Co-60 beam, where the difference is about 4% at 10 cm depth for a 15 cm x 15 cm field. It was found that the sensitometric curves of the Kodak film derived at different depths are almost identical for the four x-ray beams. Films were positioned in a solid phantom, either perpendicular or (almost) parallel to the beam axis, and irradiated to different dose levels using various photon beams (Co-60, 6 MV, 15 MV, 18 MV, 45 MV). This variation, as well as the effect of beam energy and film plane orientation on OD, was therefore investigated for two types of film, Kodak X-Omat V and Agfa Structurix D2. ![]() In particular the variation of optical density, OD, with field size and depth in a phantom shows large differences in magnitude between various authors. Existing data concerning the influence of irradiation geometry on the sensitometric curve are conflicting. The shape of the sensitometric curve depends on the type of film as well as on the irradiation and processing conditions. Film dosimetry is an important tool for the verification of irradiation techniques.
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