Comparative evaluation of Kodak EDR2 and XV2 films for verification of intensity modulated radiation therapy

Abstract

Film dosimetry provides a convenient tool to determine dose distributions, especially for verification of IMRT plans. However, the film response to radiation shows a significant dependence on depth, energy and field size that compromise the accuracy of measurements. Kodak's XV2 film has a low saturation dose (approximately 100 cGy) and, consequently, a relatively short region of linear dose-response. The recently introduced Kodak extended range EDR2 film was reported to have a linear dose-response region extending to 500 cGy. This increased dose range may be particularly useful in the verification of IMRT plans. In this work, the dependence of Kodak EDR2 film's response on the depth, field size and energy was evaluated and compared with Kodak XV2 film. Co-60, 6 MV, 10 MV and 18 MV beams were used. Field sizes were 2 x 2, 6 x 6, 10 x 10, 14 x 14, 18 x 18 and 24 x 24 cm2. Doses for XV2 and EDR2 films were 80 cGy and 300 cGy, respectively. Optical density was converted to dose using depth-corrected sensitometric (Hurter and Driffield, or H&D) curves. For each field size, XV2 and EDR2 depth-dose curves were compared with ion chamber depth-dose curves. Both films demonstrated similar (within 1%) field size dependence. The deviation from the ion chamber for both films was small forthe fields ranging from 2 x 2 to 10 x 10 cm2: < or =2% for 6, 10 and 18 MV beams. No deviation was observed for the Co-60 beam. As the field size increased to 24 x 24 cm2, the deviation became significant for both films: approximately 7.5% for Co-60, approximately 5% for 6 MV and 10 MV, and approximately 6% for 18 MV. During the verification of IMRT plans, EDR2 film showed a better agreement with the calculated dose distributions than the XV2 film.

Comparison of two-dimensional transmitted dose maps: evaluation of existing algorithms

“…Due to the much smaller grain size, used in the EDR2 film structure, it is a very slow speed film and nearly energy independent for dose values of less than 5 Gy 13, [16][17][18][19][20][21] . Dose values obtained from EDR2 film measurements have been reported to agree with ion chamber measurements within 1-2% [11][12][13] . Pinnacle 3 treatment planning system version 6.2b (Philips Radiation Oncology Systems, ADAC Laboratories, Milpitas, CA, USA) was used to calculate the transmitted dose in an EPID modelled below an inhomogeneous phantom.…”

“…The degree of agreement between two dose maps, acquired for the same irradiation conditions, was identified using the composite and gamma function algorithms. The reference radiation dose maps were acquired using EDR2 film (Kodak Extended Dose Range 2, Eastman Kodak Co., Rochester, NY, USA) (due to its near energy independence [11][12][13] ). Electronic Portal Images (EPIs) of a homogeneous phantom were acquired using a Scanning Liquid filled Ionization Chamber Electronic Portal Imaging Device (SLIC-EPID).…”

Quantitative megavoltage radiation therapy dosimetry using the storage phosphor KCl:Eu2+

“…3,4 Radiographic film has become the de facto standard for two-dimensional ͑2D͒ dose distribution measurements, with three-dimensional dose distribution validation conducted using stacked film measurements. [3][4][5][6][7][8][9][10][11][12][13][14][15][16] As diagnostic radiology and radiation oncology clinics move toward electronic imaging, the reduced availability of radiographic film and film processors is becoming increasingly problematic. Furthermore, since film is fundamentally a single use detector, it cannot be reliably calibrated.…”

Rounded leaf end modeling in Pinnacle VMAT treatment planning for fixed jaw linacs

“…Kodak EDR2 film calibration was also conducted by irradiating separate sheets of film with a $10.4\times 10.4\hspace{0.17em}\text{cm}$ field size at a depth of 10 cm depth in solid water, aligned to 100 cm SAD on central axis (CAX) of the linac. Published work evaluating the use of EDR2 film for IMRT quality assurance have shown minimal field size related changes in optical density (OD) response for square fields between 2 and 14 cm in size 19 , 20 , 21 . Monitor units (MU) were calculated and delivered under standard conditions for 20, 50, 100, and 150 cGy to determine irradiated dose based on the optical density (OD) of the film.…”