Precautions and strategies in using a commercial flatbed scanner for radiochromic film dosimetry

Abstract

The purpose of this study was to investigate the value of a commercially available flatbed scanner for film dosimetry with radiochromic film for external radiotherapy. The EPSON Pro 1680 Expression scanner was examined as a densitometer for two-dimensional film dosimetry with Gafchromic EBT film. An accurate and efficient scanning procedure was established. Possible drift and warm-up effects of the scanner were studied and the direct physical influence of the scanner light on the radiochromic film was assessed. Next, we investigated the scan field uniformity. Also, we examined if the accuracy of radiochromic film was improved by subtracting the optical density of the unirradiated blank film from the optical density of the irradiated film. To assess the accuracy of Gafchromic EBT film when the EPSON scanner was used as a densitometer, the depth dose of a 2 x 15 cm(2) field and the in-plane and cross-plane profiles of a 15 x 15 cm(2) field were measured and compared with diamond detector measurements. When taking consecutive scans, we found that the optical density taken from the first scan was about 1% higher than the optical density taken from subsequent scans. We attribute this to the warming up of the lamp of the scanner. Longer-term drift of the scanner was found to be absent. We found that the use of a correction matrix was necessary to correct for the non-uniform scanner response over the scan field. Subtracting the optical density of the unirradiated blank film from the irradiated film improves the precision of the Gafchromic EBT film. Depth dose and profile measurements with Gafchromic EBT film and the diamond detector are in agreement within 2.5%. The EPSON Pro 1680 Expression scanner is an excellent tool for accurate two-dimensional film dosimetry with Gafchromic EBT film provided that some precautions and corrections are taken into account.

Evaluation of the dosimetric properties of a diode detector for small field proton radiosurgery

“…Furthermore, protons have the added complication of varying LET as a function of depth (or energy) that can strongly impact detector response. Radiochromic film provides high‐resolution measurements, but exhibit a LET dependent response, requires postprocessing, special handling, and supporting data acquisitions for calibration and to control for artifacts 1 , 2 , 3 , 4 , 5 . A promising alternative is provided by diode detectors with small rugged sensitive volumes (SV) that are capable of high resolution and real‐time dose acquisition, and that are now commercially available.…”

NCS Report 22: Code of practice for the quality assurance and control for intensity modulated radiotherapy

“…In the past, radiochromic films were successfully used to perform gamma analysis with a 3%/3mm gamma criterion (103).…”

Dosimetric evaluation of internal shielding in a high-dose-rate skin applicator

“…A flatbed scanner (EPSON 10000XL) was used to scan the films following the recommendations found in a literature [19][20][21]. Briefly, each film was scanned prior to the irradiation and 24 h after the irradiation [22] in order to subtract the background [23]. The films were located at the centre of the scan bed in order to minimize the effect of the scanner heterogeneity, scanned 4 times and digitized in a consistent orientation.…”