Radiochromic film dosimetry with flatbed scanners: A fast and accurate method for dose calibration and uniformity correction with single film exposure.

Film dosimetry is an attractive tool for dose distribution verification in intensity modulated radiotherapy (IMRT). A critical aspect of radiochromic film dosimetry is the scanner used for the readout of the film: the output needs to be calibrated in dose response and corrected for pixel value and spatial dependent nonuniformity caused by light scattering; these procedures can take a long time. A method for a fast and accurate calibration and uniformity correction for radiochromic film dosimetry is presented: a single film exposure is used to do both calibration and correction. Gafchromic™ EBT films were read with two flatbed charge coupled device scanners (Epson V750 and 1680Pro). The accuracy of the method is investigated with specific dose patterns and an IMRT beam. The comparisons with a two-dimensional array of ionization chambers using a 18×18 cm2 open field and an inverse pyramid dose pattern show an increment in the percentage of points which pass the gamma analysis (tolerance parameters of 3% and 3 mm), passing from 55% and 64% for the 1680Pro and V750 scanners, respectively, to 94% for both scanners for the 18×18 open field, and from 76% and 75% to 91% for the inverse pyramid pattern. Application to an IMRT beam also shows better gamma index results, passing from 88% and 86% for the two scanners, respectively, to 94% for both. The number of points and dose range considered for correction and calibration appears to be appropriate for use in IMRT verification. The method showed to be fast and to correct properly the nonuniformity and has been adopted for routine clinical IMRT dose verification.

[1]  Martin J Butson,et al.  Weak energy dependence of EBT gafchromic film dose response in the 50 kVp-10 MVp X-ray range. , 2006, Applied radiation and isotopes : including data, instrumentation and methods for use in agriculture, industry and medicine.

[2]  M. Butson,et al.  Post-irradiation colouration of Gafchromic EBT radiochromic film , 2005, Physics in medicine and biology.

[3]  D. Huyskens,et al.  A quantitative evaluation of IMRT dose distributions: refinement and clinical assessment of the gamma evaluation. , 2002, Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology.

[4]  M. Bucciolini,et al.  Verification of IMRT fields by film dosimetry. , 2003, Medical physics.

[5]  J. Dempsey,et al.  Important considerations for radiochromic film dosimetry with flatbed CCD scanners and EBT GAFCHROMIC® film. , 2006, Medical physics.

[6]  J. Galvin,et al.  Radiochromic film dosimetry: recommendations of AAPM Radiation Therapy Committee Task Group 55. American Association of Physicists in Medicine. , 1998, Medical physics.

[7]  S. Chiu‐Tsao,et al.  Energy dependence of response of new high sensitivity radiochromic films for megavoltage and kilovoltage radiation energies. , 2005, Medical physics.

[8]  C Ross Schmidtlein,et al.  Precise radiochromic film dosimetry using a flat-bed document scanner. , 2005, Medical physics.

[9]  David A Jaffray,et al.  Characterization and real-time optical measurements of the ionizing radiation dose response for a new radiochromic medium. , 2005, Medical physics.

[10]  Elisa Calamia,et al.  Clinical use of EBT model Gafchromic™ film in radiotherapy. , 2006, Medical physics.

[11]  J. Dempsey,et al.  Evaluation of the gamma dose distribution comparison method. , 2003, Medical physics.

[12]  D. Low,et al.  A technique for the quantitative evaluation of dose distributions. , 1998, Medical physics.

[13]  C. De Wagter,et al.  Precautions and strategies in using a commercial flatbed scanner for radiochromic film dosimetry , 2007, Physics in medicine and biology.

[14]  E. Wilcox,et al.  Comparison of the epson expression 1680 flatbed and the vidar VXR-16 dosimetry PRO film scanners for use in IMRT dosimetry using gafchromic and radiographic film. , 2006, Medical physics.

[15]  M. Butson,et al.  Scanning orientation effects on Gafchromic EBT film dosimetry , 2006, Australasian Physics & Engineering Sciences in Medicine.

[16]  A. L. Angelini,et al.  Characterization of a 2D ion chamber array for the verification of radiotherapy treatments , 2005, Physics in medicine and biology.

[17]  E. Podgoršak,et al.  Sensitivity of linear CCD array based film scanners used for film dosimetry. , 2006, Medical physics.