Browsing by Author "Yapici, Bulent"

Now showing 1 - 6 of 6

First 500 Fractions Delivered with a Magnetic Resonance-guided Radiotherapy System: Initial Experience
(CUREUS INC, 2019-01-01) Sahin, Bilgehan; Mustafayev, Teuta Zoto; Gungor, Gorkem; Aydin, Gokhan; Yapici, Bulent; Atalar, Banu; Ozyar, Enis
Objectives Improved soft-tissue visualization, afforded by magnetic resonance imaging integrated into a radiation therapy linear accelerator-based radiation delivery system (MR-linac) promises improved image-guidance. The availability of MR-imaging can facilitate on-table adaptive radiation planning and enable real-time intra-fraction imaging with beam gating without additional exposure to radiation. However, the novel use of magnetic resonance-guided radiation therapy (MRgRT) in the field of radiation oncology also potentially poses challenges for routine clinical implementation. Herein the early experience of a single institution, implementing the first MRgRT system in the country is reported. We aim to describe the workflow and to characterize the clinical utility and feasibility of routine use of an MR-linac system. Methods The ViewRay MRIdian MR-linac system consists of a split-magnet 0.35 T MR-imaging scanner with a double focused multi-leaf collimator (MLC) equipped 6MV linear accelerator. Unique to the system are the control console integrated on-table adaptive radiation therapy (oART) planning capabilities as well as automated beam gating based on real-time intra-fraction MR imaging. From the first day of clinical implementation, oART was performed according to physicians' discretion when medically indicated. All fractions were delivered under real-time imaging with soft tissue-based automated beam gating with individualized gating boundary settings. Patients actively assisted in breath-hold beam gating with the help of custom designed prismatic glasses allowing sight of a computer monitor mounted on the back wall just behind the MRI system bore. Patient demographics and treatment experience, indications for MRgRT including diagnosis and disease site, radiation dose prescribed and fractionation scheme, utilization of oART, respiratory gating settings, as well as duration of each treatment phase were analyzed. Results Between September 2018 and May 2019, 72 patients with 84 tumor sites were treated with MRgRT in 500 total fractions. Median patient age was 66 years (range: 28-83 years). Among 84 tumor sites, the most frequently treated regions were upper abdominal and pelvic (n = 36, 43\% and n = 29, 34\%, respectively). The most common diagnosis was prostate cancer, with 14 patients treated. In 69 patients (93.2\%) oART was used at least once during a treatment course. Twenty-nine targets (43.1\%) with significant breathing-related motion were treated in breath-hold with patient visual feedback. Median prescribed dose was 36.25 Gy (range: 24-70 Gy) in median five fractions (range: 3-28 fractions). A gating boundary of 3 mm around a gating region of interest (gROI) was most commonly used (range: 3-5 mm) with 95\% of the gROI (range: 93-97\%) required to be within the gating boundary for the beam to automatically engage. Mean total treatment time was 47 min (range: 21-125 min) and mean beam-on time was 16.7 min (range: 6-62 min). Conclusions MRgRT afforded by an MR-linac system has been successfully implemented into routine clinical use at our institution as the first system of its kind in Turkey. While the overall number of patients treated and fractions delivered is still limited, we have demonstrated the feasibility of both on-table adaptive radiation therapy as well as automated real-time beam gating on a daily basis in acceptable time schedules.
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)
Long-term toxicity and survival outcomes after stereotactic ablative radiotherapy for patients with centrally located thoracic tumors
(WALTER DE GRUYTER GMBH, 2020-01-01) Atalar, Banu; Mustafayev, Teuta Zoto; Sio, Terence T.; Sahin, Bilgehan; Gungor, Gorkem; Aydin, Gokhan; Yapici, Bulent; Ozyar, Enis
Background. Stereotactic ablative radiotherapy (SABR) is effective for thoracic cancer and metastases
Multichannel Film Dosimetry for Quality Assurance of Intensity Modulated Radiotherapy Treatment Plans Under 0.35 T Magnetic Field
(CUREUS INC, 2020-01-01) Gungor, Gorkem; Korkmaz, Latif; Kayalilar, Namik; Aydin, Gokhan; Yapici, Bulent; Mustafayev, Teuta Zoto; Atalar, Banu; Ozyar, Enis
Purpose To evaluate the intensity modulated radiotherapy (IMRT) quality assurance (OA) results of the multichannel film dosimetry analysis with single scan method by using Gafchromic (TM) EBT3 (Ashland Inc., Covington, KY, USA) film under 0.35 T magnetic field. Methods Between September 2018 and June 2019, 70 patients were treated with ViewRay MRldian (R) (ViewRay Inc., Mountain View, CA) linear accelerator (Linac). Film dosimetry OA plans were generated for all IMRT treatments. Multichannel film dosimetry for red, green and blue (RGB) channels were compared with treatment planning system (TPS) dose maps by gamma evaluation analysis. Results The mean gamma passing rates of RGB channels are 97.3\% +/- 2.26\%, 96.0\% +/- 3.27\% and 96.2\% +/- 3.14\% for gamma evaluation with 2\% DD/2 mm distance to agreement (DTA), respectively. Moreover, the mean gamma passing rates of RGB channels are 99.7\% +/- 0.41\%, 99.6\% +/- 0.59\% and 99.5\% +/- 0.67\% for gamma evaluation with 3\% DD/3 mm DTA, respectively. Conclusion The patient specific QA using Gafchromic (TM) EBT3 film with multichannel film dosimetry seems to he a suitable tool to implement for MR-guided IMRT treatments under 0.35 T magnetic field. Multichannel film dosimetry with Gafchromic (TM) EBT3 is a consistent QA tool for gamma evaluation of the treatment plans even with 2\% DD/2 mm DTA under 0.35 T magnetic field presence.
Radiotherapy Equipment and Workforce in Turkey
(KARE PUBL, 2021-01-01) BecerIr, Hatice Bilge; Gurdalli, Salih; Yapici, Bulent; Alkaya, Fadime; cakir, Aydin; Yaray, Kadir; Gursoy, Tamer Oguz
OBJECTIVE Radiotherapy is a costly treatment that requires the proper use of human and financial resources. In any country, the radiation therapy equipment and workforce should be well planned for the appropriate use of resources and radiotherapy treatments. For proper planning, the current situation should be assessed and prepared for the targets to be achieved. This study aims to determine the current status of radiotherapy devices and the workforce in Turkey. METHODS Questions were sent to 141 centers to evaluate the number of devices, technical specifications, date of manufacture and the number of radiation oncologists, medical physicists, and radiotherapy technicians by Turkish Medical Physics Association. The responses from the centers were analyzed by region and compared with the situation in other countries. RESULTS The data collected in the study are from December 2019. The rate of radiotherapy devices in Turkey according to population is estimated to be 3.14 megavoltage (MV) external devices per 1 million people. The distribution is not homogeneous in all regions. The highest value is 4.59 in the Central Anatolia region, and the lowest is 0.78 in the Eastern Anatolia region. For each MV device, on average, there are 1.58 specialists in medical physics. CONCLUSION Our study has shown that Turkey has made significant progress in terms of radiotherapy equipment and workforce in the past decade. Nevertheless, although Turkey did not reach the standards of high-income European countries, it is comparable to middle-income countries.
Re-Irradiation of Non-Small Cell Lung Cell Cancer Recurrences with Stereotactic Body Radiotherapy
(2016-01-01) Atalar, Banu; Sahin, Bilgehan; Gungor, Gorkem; Aydin, Gokhan; Yapici, Bulent; Ozyar, Enis