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    Dosimetric evaluation of PLA and ABS materials produced by two different production techniques
    (Springernature, 2024) Karacam, Songuel Cavdar; Tuncman, Duygu; Sahin, Tulin; Sahin, Senol; Ergen, Sefika Arzu; Dagdelen, Meltem; Uzel, Omer Erol
    In radiotherapy applications, with the aim of accurately delivering the prescribed dose in-patient treatments, a wide variety of organic and/or inorganic materials can be utilized as bolus material. In recent years, polymer materials have become a wide range of scientific research in radiotherapy. Especially, PLA (polylactic acid) and acrylonitrile butadiene styrene (ABS) materials are widely utilized in various applications within the field of radiotherapy. While three-dimensional (3D) printing, especially using fused deposition modeling (FDM) technology, was among the first techniques adopted, plastic injection molding (IM) has also been a well-established manufacturing method for many years. Initially, ABS and PLA materials were 3D-printed on an FDM 3D printer as square prisms measuring 12 x 12 x 1 cm3. These were specifically designed for use as measurement instruments in radiation assessments. Subsequently, identical test materials were produced through IM in an ISO D2-type mold made of S235JR steel (material number 1.0038) with the same dimensions. In radiotherapy applications, it is important for clinical use to evaluate the material of dosimetric properties as well as tissue equivalence. The goal was to dosimetrically evaluate the response of these materials to radiation produced by both FDM and IM techniques. Hounsfield units (HU) values were determined with the CT simulator device for all materials. Dosimetric measurements were performed using a 6-MV nominal photon energy. Percentage depth doses, dose profiles, and radio transmittance measurements of the materials were conducted in a water phantom and solid water phantom. All measurements were also conducted for commercially available bolus materials used in patients. Commercial bolus was used as a reference due to its routine use in the clinic. Although the dosimetric parameters for materials produced through 3D printing and plastic injection molding yielded similar results among themselves and with bolus material, it is advisable to evaluate the material dosimetrically before its use as a personal material on a patient due to printing characteristics and material variability.
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    Investigation of Radiochromic Film Use for Source Position Verification through a LINAC On-Board Imager (OBI)
    (Mdpi, 2023) Karacam, Songul Cavdar; Tuncman, Duygu; ALMisned, Ghada; Ene, Antoaneta; Tekin, Huseyin Ozan
    Background and Objectives: Quality assurance is an integral part of brachytherapy. Traditionally, radiographic films have been used for source position verification, however, in many clinics, computerized tomography simulators have replaced conventional simulators, and computerized radiography systems have replaced radiographic film processing units. With these advances, the problem of controlling source position verification without traditional radiographic films and conventional simulators has appeared. Materials and Methods: In this study, we investigated an alternative method for source position verification for brachytherapy applications. Source positions were evaluated using Gafchromic (TM) RTQA2 and EBT3 film and visually compared to exposed RTQA radiochromic film when using a Nucletron Oldelft Simulix HP conventional simulator and a Gammamed 12-i brachytherapy device for performance evaluation. Gafchromic film autoradiography was performed with a linear accelerator (LINAC) on-board imager (OBI). Radiochromic films are very suitable for evaluation by visual inspection with a LINAC OBI. Results: The results showed that this type of low-cost, easy-to-find material can be used for verification purposes under clinical conditions. Conclusions: It can be concluded that source-position quality assurance may be performed through a LINAC OBI device.