title: A new method of readout in radiochromic film dosimetry.
abstract: Radiochromic film as a dosimetry medium offers several advantages in high-resolution radiography. A new technique of readout was developed to measure the optical density distributions of the film in purely directed light. This technique implements radiochromic film dosimetry near the film's absorption maximum by using a single-mode top-surface emitting laser diode (675.2 nm). The effective sensitivity of the film, compared with a helium-neon laser densitometer (632.8 nm), is increased approximately threefold. Good accuracy, high spatial resolution and simple assembly of the readout system is achieved. Beam profiles of the four final collimator helmets of a Leksell Gamma Knife (Elekta Inc., Sweden) were experimentally determined. Measured profiles and full-widths at half maximum are consistent with the computer generated data of the dose planning system (Kula 4.4, Elekta Inc., Sweden). The output factor of the 4 mm collimator (the smallest collimator with the steepest dose gradient), essential for the application of well defined doses, was checked. The measurements established an output factor of 826 +/- 9 that lies 9 +/- 1% lower than the adjusted one.
authors.affiliation: Institute of Solid State Electronics, Technical University of Vienna, Austria.
authors.forename: P O
authors.initials: PO
authors.lastname: Kellermann
authors.forename: A
authors.initials: A
authors.lastname: Ertl
authors.forename: E
authors.initials: E
authors.lastname: Gornik
mesh_terms: D002138:Calibration; D003037:Cobalt Radioisotopes; D004867:Equipment Design; D005373:Film Dosimetry / Q000295:instrumentation* / Q000379:methods*; D008027:Light; D019047:Phantoms, Imaging; D011137:Polystyrenes; D016634:Radiosurgery / Q000295:instrumentation / Q000379:methods; D011878:Radiotherapy / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013053:Spectrophotometry
chemical_list: D003037:Cobalt Radioisotopes; D011137:Polystyrenes