Researcher: Atasoy, Ali İhsan
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Atasoy, Ali İhsan
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Publication Metadata only Case presentation: the effect of volumetric image guidance and adaptive radiotherapy on cardiac dose in a patient with esophageal cancer(Kare Publ, 2018) Sağlam, Yücel; Alpan, Vildan; N/A; N/A; N/A; N/A; N/A; Sezen, Duygu; Bölükbaşı, Yasemin; Durankuş, Nilüfer Kılıç; Atasoy, Ali İhsan; Selek, Uğur; Faculty Member; Faculty Member; Teaching Faculty; Other; Faculty Member; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; 170535; 216814; 148139; N/A; N/A; N/A; 27211We present the case of a patient with esophageal cancer whose tumor size regression prompted re-planning to decrease the cardiac dose. A 68-year-old male presented at our outpatient clinic with dysphagia. He was diagnosed with clinical T3N1 M0 adenocarcinoma located at the distal esophagus-esophagogastric junction. He was decided to have surgery after receiving neoadjuvant chemoradiotherapy. Following 4-D CT simulation, IG-IMRT with SIB technique was planned as 50 Gy in 25 fractions to iGTV and as 45 Gy to the area identified as the CIV. Daily kV and weekly CBCI were planned at the beginning of the treatment. Concurrent CT with weekly paclitaxel-carboplatin was administered. At the simulation and start of the treatment, the heart was pushed anteriorly due to the mass effect and dilatation in the mid-lower esophagus. The mass and dilatation regressed at the weekly CBCT of the patient. The third-week CBCT evaluation revealed the movement of the heart posteriorly into the PTV. Re-simulation was performed to continue with the adaptive planning for the last 10 treatment fractions. The cumulative dose received by the heart was reduced from 96% to 93% for V5Gy, from 79% to 60.8% for V10Gy, from 60% to 43.2% for V15Gy, from 35% to 21% for V20Gy, and from 29.6 to 28 Gy for the mean cardiac dose with the volumetric image-guided adaptive planning. If tumor regression is predicted during radiotherapy to possibly change doses of organs at risk, volumetric image guidance should be encouraged once per week, at least, to consider adaptive treatment when required to ensure the critical organ doses within safe limits.Publication Metadata only Hypofractionated frameless gamma knife radiosurgery for large metastatic brain tumors(Springer, 2021) Samancı, Mustafa Yavuz; Şişman, Uluman; Altıntaş, Alara; Sarıoğlu, Sebile; Sharifi, Samira; Atasoy, Ali İhsan; Bölükbaşı, Yasemin; Peker, Selçuk; Faculty Member; Undergraduate Student; Undergraduate Student; Undergraduate Student; Undergraduate Student; Other; Faculty Member; Faculty Member; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; Koç University Hospital; 275252; N/A; N/A; N/A; N/A; N/A; 216814; 11480Hypofractionated stereotactic radiosurgery has become an alternative for metastatic brain tumors (METs). We aimed to analyze the efficacy and safety of frameless hypofractionated Gamma Knife radiosurgery (hfGKRS) in the management of unresected, large METs. All patients who were managed with hfGKRS for unresected, large METs (> 4 cm(3)) between June 2017 and June 2020 at a single center were reviewed in this retrospective study. Local control (LC), progression-free survival (PFS), overall survival (OS), and toxicities were investigated. A total of 58 patients and 76 METs with regular follow-up were analyzed. LC rate was 98.5% at six months, 96.0% at one year, and 90.6% at 2 years during a median follow-up of 12 months (range, 2-37). The log-rank test indicated no difference in the distribution of LC for any clinical or treatment variable. PFS was 86.7% at 6 months, 66.6% at 1 year, and 58.5% at 2 years. OS was 81% at 6 months, 63.6% at one year, and 50.7% at 2 years. On the log-rank test, clinical parameters such as control status of primary cancer, presence of extracranial metastases, RTOG-RPA class, GPA group, and ds-GPA group were significantly associated with PFS and OS. Patients presented with grade 1 (19.0%), grade 2 (3.5%) and grade 3 (5.2%) side effects. Radiation necrosis was not observed in any patients. Our current results suggest that frameless hfGKRS for unresected, large METs is a rational alternative in selected patients with promising results.Publication Metadata only The use of treatment response assessment maps in discriminating between radiation effect and persistent tumoral lesion in metastatic brain tumors treated with gamma knife radiosurgery(Elsevier Science Inc, 2021) N/A; N/A; Peker, Selçuk; Samancı, Mustafa Yavuz; Aygün, Murat Serhat; Yavuz, Furkan; Erden, Mert Emre; Nokay, Aziz Emre; Atasoy, Ali İhsan; Bölükbaşı, Yasemin; Faculty Member; Faculty Member; Teaching Faculty; Undergraduate Student; Undergraduate Student; Undergraduate Student; Other; Faculty Member; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; School of Medicine; N/A; Koç University Hospital; N/A; N/A; N/A; N/A; Koç University Hospital; N/A; 11480; 275252; 291692; N/A; N/A; N/A; N/A; 216814BACKGROUND: Traditional imaging modalities are not useful in the follow-up of irradiated metastatic brain tumors, because radiation can change imaging characteristics. We aimed to assess the ability of treatment response assessment maps (TRAMs) calculated from delayed-contrast magnetic resonance imaging (MRI) in differentiation between radiation effect and persistent tumoral tissue. METHODS: TRAMs were calculated by subtracting three-dimensional T1 MRIs acquired 5 minutes after contrast injection from the images acquired 60-105 minutes later. Red areas were regarded as radiation effect and blue areas as persistent tumoral lesion. Thirty-seven patients with 130 metastatic brain tumors who were treated with Gamma Knife radiosurgery and who underwent TRAMs perfusion-weighted MRI were enrolled in this retrospective study. RESULTS: The median age was 58 years and the most common primary diagnosis was lung cancer (n = 21). The median follow-up period of patients was 12 months. The overall local control rate was 100% at 1 year and 98.9% at 2 years. The median progression-free survival was 12 months. The mean overall survival was 27.3 months. The radiologic and clinical follow-up showed a clinicoradio-logic diagnosis of a persistent tumoral lesion in 3 tumors (2.3%) and radiation effect in 127 tumors (97.7%). There was a fair agreement between clinicoradiologic diagnosis and TRAMs analysis (k = 0.380). The sensitivity and positive predictive value of TRAMs in diagnosing radiation effect were 96.06% and 99.2%, respectively. TRAMs showed comparable results to perfusion-weighted MRI, with a diagnostic odds ratio of 27.4 versus 20.7, respectively. CONCLUSIONS: The presented results show the ability of TRAMs in differentiating radiation effect and persistent tumoral lesions.Publication Open Access Double isocenter optimization with HD-MLC linear accelerator to treat extended fields in patients with head and neck cancers(Bakis Productions LTD, 2021) Küçük, Ahmet; Topkan, Erkan; Selek, Uğur; Bölükbaşı, Yasemin; Durankuş, Nilüfer Kılıç; Sezen, Duygu; Sağlam, Yücel; Atasoy, Ali İhsan; Karaköse, Fatih; Alpan, Vildan; Akdemir, Eyüb Yaşar; Şenyürek, Şükran; Faculty Member; Faculty Member; Faculty Member; Doctor; Doctor; School of Medicine; Koç University Hospital; 27211; 216814; N/A; 170535; N/A; N/A; N/A; N/A; N/A; N/APurpose: for departments with a congested patient burden or with a limited number of eligible LINACs, we investigated whether LINACS dedicated for SRS-SBRT with limited field high-definition (HD) multi-leaf collimator (MLC) could help to carry this load, and utilized a double-isocenter (DI) optimization with a limited field size of HD-MLC to defeat the craniocaudal field size restriction to match treated plans in a wide-field MLC LINAC for head and neck cancer patients. Methods: fourteen patients with locally advanced head and neck cancers were included, previously treated with simultaneous integrated boost volumetric modulated arc treatment (VMAT) in 33 fractions of clinical target volumes (CTV) of 70Gy, 63Gy, and 57Gy, via single isocenter (SI) plans in Millennium MLC-120 of Varian Trilogy. The DI plans were generated on Pinnacle TPS to be delivered in HD 120 leaves MLC on Varian TrueBeam. The organs at risk (OAR) doses and the prescription volume parameters were compared. Results: DI plans in HD-MLC LINACs were successfully matching the previously treated plans for OAR and CTV constraints. The CI (1.18 versus 1.26; p=0.004) and HI (0.23 versus 0.29; p<0.001) were significantly improved with DI, while the MUs (1321.5 versus 800.3; p<0.001) and the treatment delivery times (6.1 versus 3.7 min; p<0.001) per fraction increased modestly with DI compared to SI, respectively. Conclusions: we revealed that DI optimization plans prepared for HD-MLC could effectively accomplish our goal dosimetrically in locoregionally advanced head and neck cases, despite a modest increase in the MU and treatment delivery times per fraction. This technique may provide an alternative in case of downtimes of standard MLC systems or a standalone treatment machine in case of high volumes requiring extended-field IMRT procedures, or possibly shorten the lengthy waiting times in facilities with limited SRS or SBRT patients.Publication Open Access Novel clinically weight-optimized dynamic conformal arcs (WO-DC A) for liver SBRT: a comparison with volumetric modulated arc therapy (VMAT)(Dove Medical Press, 2021) Topkan, Erkan; Selek, Uğur; Bölükbaşı, Yasemin; Sağlam, Yücel; Atasoy, Ali İhsan; Karaköse, Fatih; Budak, Mustafa; Alpan, Vildan; Faculty Member; Faculty Member; Doctor; Medical Physicist; School of Medicine; Koç University Hospital; 27211; 216814; N/A; N/A; N/A; N/A; N/APurpose: to evaluate the feasibility of shortening the duration of liver stereotactic radiotherapy (SBRT) without jeopardizing dosimetry or conformity by utilizing weight-optimized dynamic conformal arcs (WO-DCA) as opposed to volumetric modulated arc therapy (VMAT) for tumors away from critical structures. Methods: nineteen patients with liver metastasis were included, previously treated with 50 Gy in 4 fractions with VMAT technique using two partial coplanar arcs of 6 MV beams delivered in high-definition multi-leaf collimator (HD-MLC). Two coplanar partial WODCA were generated on Pinnacle treatment planning system (TPS) for each patient; and MLC aperture around the planning target volume (PTV) was automatically generated at different margins for both arcs and maintained dynamically around the target during arc rotation. Weight of the two arcs using optimization method was adjusted between the arcs to maximize tumor coverage and protect organs at risk (OAR) based on the RTOG-0438 protocol. Results: the WO-DCA plans successfully ""agreed"" with the standard VMAT for OAR (liver, spinal cord, stomach, duodenum, small bowel, and heart) and PTV (D-mean, D-98%, D-2%, CI, and GI), with superior mean quality assurance (QA) pass rate (97.06 vs 93.00 for VMAT; P < 0.001 and t = 8.87). Similarly, the WO-DCA technique additionally reduced the beam-on time (3.26 vs 4.43; P < 0.001) and monitor unit (1860 vs 2705 for VMAT; P < 0.001) values significantly. Conclusion: the WO-DCA plans might minimize small-field dosimetry errors and defeat patient-specific VMAT QA requirements due to the omission of MLC beam modulation through the target volume. The WO-DCA plans may additionally enable faster treatment delivery times and lower OAR without sacrificing target doses in SBRT of liver tumors away from critical structures.