Evaluation of effective energy using radiochromic film and a step-shaped aluminum filter

J Applied Clin Med Phys

et al. 2016

This study investigates an X‐ray dose measurement method for computed tomography using Gafchromic films. Nonuniformity of the active layer is a major problem in Gafchromic films. In radiotherapy, nonuniformity error is reduced by applying the double‐exposure technique, but this is impractical in diagnostic radiology because of the heel effect. Therefore, we propose replacing the X‐rays in the double‐exposure technique with ultraviolet (UV)‐A irradiation of Gafchromic EBT2 and EBT3. To improve the reproducibility of the scan position, Gafchromic EBT2 and EBT3 films were attached to a 3‐mm‐thick acrylic plate. The samples were then irradiated with a 10 W UV‐A fluorescent lamp placed at a distance of 72 cm for 30, 60, and 90 minutes. The profile curves were evaluated along the long and short axes of the film center, and the standard deviations of the pixel values were calculated over large areas of the films. Paired t‐test was performed. UV‐A irradiation exerted a significant effect on Gafchromic EBT2 (paired t‐test; p=0.0275) but not on EBT3 (paired t‐test; p=0.2785). Similarly, the homogeneity was improved in Gafchromic EBT2 but not in EBT3. Therefore, the double‐exposure technique under UV‐A irradiation is suitable only for EBT2 films.PACS number(s): 87.53 Bn

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Correction of nonuniformity error of Gafchromic EBT2 and EBT3

J Applied Clin Med Phys

et al. 2016

“…After each exposure, scanning was done with a flatbed scanner (EpsonES‐10000G, Seiko Epson Corp. Nagano, Japan) and images were acquired using Adobe Photoshop CS2 (Adobe Systems Inc., San Jose, CA). Scanning was done with 48 bit, 100 dpi resolution, and RGB mode with a PPC film (CR‐PP686) (3M Co., St. Paul, MN), using a liquid‐crystal protective film (LCD‐230W) (Sanwa Supply Inc., Okayama, Japan) to prevent moiré artifacts (Newton's rings) (15) . The Gafchromic films were always scanned in the same direction (portrait).…”

Section: Methodsmentioning

confidence: 99%

Comparing three UV wavelengths for pre‐exposing Gafchromic EBT2 and EBT3 films

J Applied Clin Med Phys

et al. 2015

Gafchromic films are used for X‐ray dose measurements during diagnostic examinations and have begun to be used for three‐dimensional X‐ray dose measurements using the high‐resolution characteristics of Gafchromic films for computed tomography. However, the problem of unevenness in Gafchromic film active layers needs to be resolved. Double exposures using X‐rays are performed during therapeutic radiology, although this is difficult for a diagnostic examination because of a heel effect. Thus, it has been suggested that ultraviolet (UV) radiation be used as a substitute for X‐rays. However, the appropriate UV wavelength has not been determined. Thus, we conducted this study to decide an appropriate UV wavelength. UV peak wavelengths of 245 nm (UV‐A), 310 nm (UV‐B), and 365 nm (UV‐C) were used to irradiate EBT2 and EBT3 films. Each UV wavelength was irradiated for 5, 15, 30, and 60 min, and irradiation was then repeated every 60 min up to 360 min. Gafchromic films were scanned after every irradiation using a flatbed scanner. Images were split into RGB images, and red images were analyzed using ImageJ, version 1.44, image analysis software. A region of interest (ROI) one‐half inch in diameter was placed in the center of subtracted Gafchromic film images, and UV irradiation times were plotted against mean pixel values. There were reactions in the front and back of Gafchromic EBT3 and the back of Gafchromic EBT2 with UV‐A and UV‐B. However, UV‐C resulted in some reactions in both sides of Gafchromic EBT2 and EBT3. The UV‐A and UV‐B wavelengths should be used.PACS number(s): 87.53 Bn

“…Therefore, they are used in HVL measurement techniques [4][5][6]. One of the main characteristics of radiochromic film that sets it apart from the IC dosimeter is that it can be used to measure two-dimensional dose distributions, as well as serving as a general X-ray film.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, it is logical to consider that the calibration curve would be a straight line in the low range for HVL measurement. It is not necessary for film density to be converted into an absorbed dose, because the calibration curve is a straight line in the low dose range for HVL measurements of X-rays in the diagnostic range [6]. Therefore, the HVL can be evaluated using only the ratio of the density distribution in the radiochromic film [4].…”

Section: Introductionmentioning

confidence: 99%

Effective energy measurement using radiochromic film: application of a mobile scanner

Polish Journal of Medical Physics and Engineering

et al. 2016

The effective energy calculated using the half-value layer (HVL) is an important parameter for quality assurance (QA) and quality control (QC). However constant monitoring has not been performed because measurements using an ionization chamber (IC) are time-consuming and complicated. To solve these problems, a method using radiochromic film (GAFCHROMIC EBT2 dosimetry film (GAF-EBT2) with slight energy dependency errors), a mobile scanner and step-shaped aluminum (SSAl) filter is developed. The results of the method using a mobile scanner were compared with those of the recommended method using an IC in order to evaluate its applicability. The difference ratios of the effective energies by each method using a mobile scanner with GAF-EBT2 were less than 5% compared with results of an IC. It is considered that this method offers a simple means of determining HVL for QA and QC consistently and quickly without the need for an IC dosimeter.