The international calibration procedure for B3 film dosimetry system to ensure the quality irradiated products by 10 MeV electron beam accelerators at VINAGAMMA

We performed an in-plant calibration of dosimetry system by electron beam (EB)irradiating the B3 film dosimeters at VINAGAMMA, and inter-compared with the alanine dosimetry, which were supplied and analyzed by Risø High Dose Reference Laboratory (HDRL) as the reference standard. The results revealed that the relative deviation between the values of absorbed doses obtained with our dosimeter and the transfer standards dosimeter measured by HDRL was within the acceptable limitation (about ± 3.0 % in the target range of 2.0-10.0 kGy). And post-irradiation stability of B3 film dosimeters was still maintained after 180 days storage. It is suggested that the B3 filmdosimetry could be used in routine radiation processing at VINAGAMMA with the investigated dose range for quality assurance of the irradiated products, specially are foods and foodstuffs processed under the 10 MeV EB accelerator at VINAGAMMA.

A protocol for accurate radiochromic film dosimetry using Radiochromic.com

Background Radiochromic films have many applications in radiology and radiation therapy. Generally, the dosimetry system for radiochromic film dosimetry is composed of radiochromic films, flatbed scanner, and film analysis software. The purpose of this work is to present the effectiveness of a protocol for accurate radiochromic film dosimetry using Radiochromic.com as software for film analysis. Materials and methods Procedures for image acquisition, lot calibration, and dose calculation are explained and analyzed. Radiochromic.com enables state-of-the-art models and corrections for radiochromic film dosimetry, such as the Multigaussian model for multichannel film dosimetry, and lateral, inter-scan, and re-calibration corrections of the response. Results The protocol presented here provides accurate dose results by mitigating the sources of uncertainty that affect radiochromic film dosimetry. Conclusions Appropriate procedures for film and scanner handling in combination with Radiochromic.com as software for film analysis make easy and accurate radiochromic film dosimetry feasible.

Rebuild-up Effect on Superficial Cardiac Lesion Surrounded by Low-density Lungs: Volumetric Modulated Arc Therapy (VMAT) Planning Study Using 3-D Printed Phantom for Ventricular Tachycardia (VT)

The study aimed to evaluate dose distributions on the superficial cardiac lesion surrounded by low-density lungs. We fabricated the 3-D printed cardiac phantom to insert in a multipurpose lungman phantom (KYOTO KAGAKU, Japan) for simulating a stereotactic body radiation therapy (SBRT) in ventricular tachycardia (VT) treatment. The cardiac phantom consists of 11 slabs with 1-cm intervals and is designed to insert radiochromic film (Gafchromic EBT3, Ashland Advanced Materials, Bridgewater, NJ) for film dosimetry. We used film dosimetry scanners (DosimetryPRO Advantage Red, Vidar Systems Corporation, Herndon, VA) with dedicated film dosimetry software (OP-IMRT, ver.1.6, IBA dosimetry, Germany). Volumetric modulated arc therapy (VMAT) technique was applied to optimize the dose distribution using the anisotropic analytic algorithm (AAA) in a radiation treatment planning (RTP) system (Eclipse v. 13.6, Varian, Palo Alto, CA). We used the 6-MV and 15-MV photon energies from a LINAC (Clinac iX, Varian, Palo Alto, CA) to investigate the planning target volume (PTV) under-dose effects due to the inner dose rebuild-up by energy dependence. The dose distributions in the VMAT plans with 6-MV and 15-MV showed good competitive coverages of the cardiac lesion without any severe underdose pattern. On the other side, the film dosimetry results showed significant dose variations near the interface of the cardiac lesion surrounded by low-density lung. The differences between the planning and the film dosimetry results revealed pretty well in both photon energies. The maximum dose differences in the cardiac PTV were ranged from 4.1–7.7% and 4.1–8.1% for 6-MV photon beams and 15-MV photon beams. Furthermore, EBT3 film measurements showed that the widths of 50% of profiles were reduced by 1.3 cm and 2.3 cm on 6-MV photon beams and 15-MV photon beams, respectively. In addition, 3-D printing techniques enabled quite challengeable dose measurements to reveal this kind of dose discrepancies in humanoid structures. This study showed that clinical cases like VT SBRT surrounded by severe inhomogeneous matter could induce wrongly to estimate appropriate dose delivery and to evaluate reasonable clinical outcomes.

Validation of an Individualized Home-Made Superficial Brachytherapy Mould Applied for Non-Melanoma Skin Cancer

Purpose: This study was conducted to evaluate the effect of a Brachytherapy (BT) customized mold (Condensation silicone elastomer (Protesil TM )) thickness ,on dose distribution pattern in deeper lesions used for nonmelanoma skin cancers (NMSC).Material and Method: MOSFET TM and GAFCHROMIC TM EBT3 film dosimeters were used for the different thicknesses of a Brachytherapy (BT) customized mold (up to 20 mm), skin dose and dose in different depths were evaluated.Result: The received dose to the surface is overestimated by TPS.Skin dose can be reduced from 250 to 150% of prescription dose by increasing mold thickness from 5 mm to 20 mm. There was a 7.7% difference in calculated dose by TPS and measured dose by MOSFET. Film dosimetry data was unreliable. There was a good agreement between film dosimetry, MOSFET detector, and TPS results, in the depth of 5mm<.Conclusion: Any individualized material chosen to use for making the customized surface BT mold should be validated at BT departments. Protesil TM can be selected as feasible material to make any form of superficial molds. For thicker NMSC lesions up to 20 mm using thicker molds up to 20 mm can be. Even for 10 mm lesions, by changing mold thickness from 5 mm to 20 mm, skin dose would reduce. Protesil TM can be used to make an individualized superficial BT mold. By increasing the mold thickness, lesions can be treated without overexposing the skin surface and skin dose reduced by increasing mold thickness. So, superficial BT can be recommended as an appropriate treatment option for NMSC lesions with some consideration.