Evaluation of triple channel correction acquisition method for radiochromic film dosimetry

Abstract

The purpose of this study was to evaluate the triple channel correction acquisition (TCCA) method for radiochromic film dosimetry performed with a flatbed scanner. The study had two parts: a fundamental and a clinical examination. In the fundamental examination, we evaluated the accuracy of calibration curves for Gafchromic EBT2 (EBT2). The films were calibrated using a field-by-field method with 13 dose steps. Seven calibration curves obtained by TCCA were compared with those produced by a single channel acquisition (SCA) method. For the clinical examination, we compared relative dose distributions obtained by TCCA and SCA for four cases of intensity-modulated radiation therapy (IMRT) and intensity-modulated arc therapy (IMAT). The fundamental examination showed that the consistency of the calibration curves was better for TCCA than for SCA, particularly for the dose range between 0.25 Gy and 1.00 Gy. The clinical examination showed that the dose differences between the measured and calculated doses in high-gradient regions were smaller with TCCA than with SCA. The average pass rates in gamma analysis for the TCCA and SCA methods were 97.2 ± 0.8% (n = 20) and 93.0 ± 1.2% (n = 20), respectively. In conclusion, TCCA can acquire accurate average dose values when creating the calibration curve. The potential advantage of TCCA for EBT2 film dosimetry was seen in high-gradient regions in clinically relevant IMRT and IMAT cases. TCCA is useful to verify dose distribution.

Evaluation of a single‐scan protocol for radiochromic film dosimetry

“…Van Hoof et al (15) assessed the multichannel method using EBT2 film and reported that the dose discrepancies from the TPS were small, in the order of 0 to 5 cGy for a single square beam. Hayashi et al (14) also performed a similar assessment and reported that the average gamma pass rates in the IMRT and VMAT dose verification were 97.2% ± 0.8%. The results from the multichannel method in this study showed a similar trend.…”

“…This method allows the separation of the dose‐dependent and dose‐independent parts of the scanned signal, and the multichannel method shows a significant improvement in spatial homogeneity. Hayashi et al (14) and Van Hoof et al (15) reported on the usefulness of the multichannel method compared to the single‐channel method. Moreover, Pevez Azorin et al (16) developed an improved multichannel method by considering the information on unirradiated film.…”

Dosimetric characteristics of intensity-modulated radiation therapy and RapidArc® therapy using a 3D N-isopropylacrylamide gel dosimeter

“…15 In 2014, Hayashi et al used three types of dosimeters, namely, MapCHECK® diode array detector, radiochromic EBT2 films, and BANG3 RPGD, to verify RapidArc TPS for irradiation of patients with prostate cancer. 16 The results indicated that the BANG3 RPGD dosimeter showed discrepancies between calculated and measured doses, particularly in low regions outside the target volume. Further improvement of the BANG3 RPGD dosimeter is thus needed.…”

Radiochromic film calibration for low-energy seed brachytherapy dose measurement

“…22 The triple-channel method has been found to produce results equivalent to the more conventional netOD method, with a simplified scanning procedure and reduced potential sources of uncertainty arising from image manipulation and noise amplification when subtracting the two images from each other. 30,31 However, it does not correct well for artifacts introduced during film scanning, and the goodness of curve fitting worsens over larger dose ranges. 30 Many other methods have also been studied which use slight variations of the aforementioned methods.…”