Araştırma Çıktıları

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Author: search.filters.author.Ozyar, EnisSubject: search.filters.subject.SBRT

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    Clinical adoption patterns of 0.35 Tesla MR-guided radiation therapy in Europe and Asia
    (BMC, 2022-01-01) Slotman, Berend J.; Clark, Mary Ann; Ozyar, Enis; Kim, Myungsoo; Itami, Jun; Tallet, Agnes; Debus, Juergen; Pfeffer, Raphael; Gentile, PierCarlo; Hama, Yukihiro; Andratschke, Nicolaus; Riou, Olivier; Camilleri, Philip; Belka, Claus; Quivrin, Magali; Kim, BoKyong; Pedersen, Anders; Felter, Mette van Overeem; Kim, Young Il; Kim, Jin Ho; Fuss, Martin; Valentini, Vincenzo
    Background Magnetic resonance-guided radiotherapy (MRgRT) utilization is rapidly expanding, driven by advanced capabilities including better soft tissue imaging, continuous intrafraction target visualization, automatic triggered beam delivery, and the availability of on-table adaptive replanning. Our objective was to describe patterns of 0.35 Tesla (T)-MRgRT utilization in Europe and Asia among early adopters of this novel technology. Methods Anonymized administrative data from all 0.35T-MRgRT treatment systems in Europe and Asia were extracted for patients who completed treatment from 2015 to 2020. Detailed treatment information was analyzed for all MR-linear accelerators (linac) and -cobalt systems. Results From 2015 through the end of 2020, there were 5796 completed treatment courses delivered in 46,389 individual fractions. 23.5\% of fractions were adapted. Ultra-hypofractionated (UHfx) dose schedules (1-5 fractions) were delivered for 63.5\% of courses, with 57.8\% of UHfx fractions adapted on-table. The most commonly treated tumor types were prostate (23.5\%), liver (14.5\%), lung (12.3\%), pancreas (11.2\%), and breast (8.0\%), with increasing compound annual growth rates (CAGRs) in numbers of courses from 2015 through 2020 (pancreas: 157.1\%
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    Improvement of conformal arc plans by using deformable margin delineation method for stereotactic lung radiotherapy
    (WILEY, 2018-01-01) Gungor, Gorkem; Demir, Melek; Aydin, Gokhan; Yapici, Bulent; Atalar, Banu; Ozyar, Enis
    Purpose: Stereotactic body radiotherapy (SBRT) is an established treatment technique in the management of medically inoperable early stage non-small cell lung cancer (NSCLC). Different techniques such as volumetric modulated arc (VMAT) and three-dimensional conformal arc (DCA) can be used in SBRT. Previously, it has been shown that VMAT is superior to DCA technique in terms of plan evaluation parameters. However, DCA technique has several advantages such as ease of use and considerable shortening of the treatment time. DCA technique usually results in worse conformity which is not possible to ameliorate by inverse optimization. In this study, we aimed to analyze whether a simple method-deformable margin delineation (DMD)-improves the quality of the DCA technique, reaching similar results to VMAT in terms of plan evaluation parameters. Methods: Twenty stage I-II (T1-2, N0, M0) NSCLC patients were included in this retrospective dosimetric study. Noncoplanar VMAT and conventional DCA plans were generated using 6 MV and 10 MV with flattening filter free (FFF) photon energies. The DCA plan with 6FFF was calculated and 95\% of the PTV was covered by the prescription isodose line. Hot dose regions (receiving dose over 100\% of prescription dose) outside PTV and cold dose regions (receiving dose under 100\% of prescription dose) inside PTV were identified. A new PTV (PTV-DMD) was delineated by deforming PTV margin with respect to hot and cold spot regions obtained from conventional DCA plans. Dynamic multileaf collimators (MLC) were set to PTV-DMD beam eye view (BEV) positions and the new DCA plans (DCA-DMD) with 6FFF were generated. Three-dimensional (3D) dose calculations were computed for PTV-DMD volume. However, the prescription isodose was specified and normalized to cover 95\% volume of original PTV. Several conformity indices and lung doses were compared for different treatment techniques. Results: DCA-DMD method significantly achieved a superior conformity index (CI), conformity number (CIPaddick), gradient index (R-50\%), isodose at 2 cm (D-2 (cm)) and external index (CD) with respect to VMAT and conventional DCA plans (P < 0.05 for all comparisons). CI ranged between 1.00-1.07 (Mean: 1.02)