Evaluation of two-dimensional electronic portal imaging device using integrated images during volumetric modulated arc therapy for prostate cancer

Abstract

background:The aim of the study was to evaluate analysis criteria for the identification of the presence of rectal gas during volumetric modulated arc therapy (VMaT) for prostate cancer patients by using electronic portal imaging device (epID)-based in vivo dosimetry (IVD).Materials and methods: all measurements were performed by determining the cumulative epID images in an integrated acquisition mode and analyzed using perFracTION commercial software. systematic setup errors were simulated by moving the anthropomorphic phantom in each translational and rotational direction. The inhomogeneity regions were also simulated by the I'mrT phantom attached to the Quasar phantom. The presence of small and large air cavities (12 and 48 cm 3 ) was controlled by moving the Quasar phantom in several timings during VMaT. sixteen prostate cancer patients received epID-based IVD during VMaT.results: In the phantom study, no systematic setup error was detected in the range that can happen in clinical (< 5-mm and < 3 degree). The pass rate of 2% dose difference (DD2%) in small and large air cavities was 98.74% and 79.05%, respectively, in the appearance of the air cavity after irradiation three quarter times. In the clinical study, some fractions caused a sharp decline in the DD2% pass rate. The proportion for DD2% < 90% was 13.4% of all fractions. rectal gas was confirmed in 11.0% of fractions by acquiring kilo-voltage X-ray images after the treatment. conclusions: Our results suggest that analysis criteria of 2% dose difference in epID-based IVD was a suitable method for identification of rectal gas during VMaT for prostate cancer patients.

Analysis of dose distribution reproducibility based on a fluence map of in vivo transit dose using an electronic portal imaging device

“…However, only four subjects had a significant correlation (p < 0.05) between body weight and GPR. This situation in line with Inui study which stated that the changes in rectal gas volume have contributed to the GPR value [31]. The correlation between body weight and GPR values in cervical cases found here is similar to the result of Kim's study on the relationship between GPR and separation [4].…”

“…Based on figure 2, each subject has a variation of correlation value between GPR and irradiation fraction. This is in line with Inui's study of prostate cases, with subjects without changes in GPR and subjects with major changes [31]. In addition, Purwati, Suhaimi [32] research by in cases of the nasopharynx showed a dominant decrease in GPR during treatment.…”

Machine log file-based dose verification using novel iterative CBCT reconstruction algorithm in commercial software during volumetric modulated arc therapy for prostate cancer patients

“…Previous studies reported that 2D EPID-based in vivo dosimetry can detect rectum and bladder fillings during VMAT for prostate cancer patients [27,28]; however, this method is unable to show 3D dosimetric changes due to rectum and bladder fillings. Accordingly, it is important to assess the dose actually delivered to the target as well as OARs by using machine log file-based CBCT calculation.…”