AbstractID: 9389 Title: A double-exposure technique using EDR2 to automate IMRT QA
A novel protocol is proposed that employs a double-exposure technique using the recently introduced radiographic film Kodak EDR2
film to automate dose verification of intensity modulated radiation therapy (IMRT) fields. The protocol is described as follows: Films
are irradiated at a source-to-surface distance of 95 cm at a depth of 5 cm in a solid water phantom under a special phantom template.
For the first exposure, the films are each irradiated in an open field of 20x20 cm2. In the second-exposure the appropriate patient
specific IMRT leaf-sequence is delivered to central portion of the pre-irradiated film. For calibration to absolute dose, we also
irradiate well-defined intensity patterns using the same double-exposure technique along with corresponding background films that
receive only the first exposure, these films are made two (or more) sets. During processing, we process one set at beginning and
another set at end of the processor cycle with the patient specific IMRT fields processed in between. This allows us to correct for slow
variation of the developing condition, which variation can be as high as 10-15% when processing multiple films over an extended
period. The digitized films along with the calculated dose distribution are imported into our in-house DoseQA 3D verification
software package which then automates the registration (using the first-exposure) and conversion of films to dose (using calibration
exposures.) With this double-exposure protocol, a typical 7-field IMRT plan can be verified in less than 1 hour.