Tıp Fakültesi / Faculty of Medicine

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Author: search.filters.author.Dolek, YemlihaHas files: Yes

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    The role of delineation education programs for improving interobserver variability in target volume delineation in gastric cancer
    (2017) Onal, Cem; Cengiz, Mustafa; Guler, Ozan C.; Dolek, Yemliha; Ozkok, Serdar; 0000-0002-2742-9021; 0000-0001-6908-3412; 28339289; D-5195-2014; AAC-5654-2020
    Objective: To assess whether delineation courses for radiation oncologists improve interobserver variability in target volume delineation for post-operative gastric cancer radiotherapy planning. Methods: 29 radiation oncologists delineated target volumes in a gastric cancer patient. An experienced radiation oncologist lectured about delineation based on contouring atlas and delineation recommendations. After the course, the radiation oncologists, blinded to the previous delineation, provided delineation for the same patient. Results: The difference between delineated volumes and reference volumes for pre-and post-course clinical target volume (CTV) were 19.8% (-42.4 to 70.6%) and 12.3% (-12.0 to 27.3%) (p = 0.26), respectively. The planning target volume (PTV) differences pre-and post-course according to the reference volume were 20.5% (-40.7 to 93.7%) and 13.1% (-10.6 to 29.5%) (p = 0.30), respectively. The concordance volumes between the pre-and post-course CTVs and PTVs were 467.1 +/- 89.2 vs 597.7 +/- 54.6cm(3) (p < 0.001) and 738.6 +/- 135.1 vs 893.2 +/- 144.6 cm(3) (p < 0.001), respectively. Minimum and maximum observer variations were seen at the cranial part and splenic hilus and at the caudal part of the CTV. The kappa indices compared with the reference contouring at pre- and post-course delineations were 0.68 and 0.82, respectively. Conclusion: The delineation course improved interobserver variability for gastric cancer. However, impact of target volume changes on toxicity and local control should be evaluated for further studies. Advances in knowledge: This study demonstrated that a delineation course based on current recommendations helped physicians delineate smaller and more homogeneous target volumes. Better target volume delineation allows proper target volume irradiation and preventing unnecessary normal tissue irradiation.
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    Effects of vaginal cylinder position on dose distribution in patients with endometrial carcinoma in treatment of vaginal cuff brachytherapy
    (2017) Ozdemir, Yurday; Dolek, Yemliha; Onal, Cem; 0000-0002-2218-2074; 0000-0002-2742-9021; 28725246; AAG-5629-2021; D-5195-2014
    Purpose: To investigate the impact of different cylinder positions on dosimetry of critical structures in patients with endometrial carcinoma undergoing three-dimensional image-based vaginal cuff brachytherapy (VCB). Material and methods: We delivered VCB at a dose of 4 Gy to a depth of 5 mm in the vaginal cuff of 15 patients using three different cylinder positions (neutral [N], parallel [P], and angled [A]) according to the longitudinal axis of the patient. We analyzed the dose-volume distribution and volumetric variability of the rectum and bladder. We converted the total doses to equivalent doses in 2 Gy (EQD(2)) using a linear-quadratic model (a/b = 3 Gy). Results: The mean rectum volume for the N, P, and A positions was 68.2 +/- 22.7 cc, 79.3 +/- 33.7 cc, and 74.2 +/- 29.6 cc, respectively. The mean rectum volume for the P position was significantly larger than that for the N position (p = 0.03). Relative to the N position, the A position resulted in a lower total EQD(2) in the highest irradiated 2 cc (D-2cc; p = 0.001), 1 cc (D-1cc; p = 0.004), and 0.1 cc (D-0.1cc; p = 0.047) of the rectum. Similarly, the P position resulted in a lower EQD(2) in the D-2cc (p = 0.018) and D-1cc (p = 0.024) of the rectum relative to the N position. In the bladder, the P position resulted in a higher EQD(2) in the D-2cc, relative to the N position (p = 0.02). There was no dosimetric difference between the P and A positions in either the rectum or the bladder. Conclusions: Vaginal cuff brachytherapy in the P and A positions is significantly superior to that in the N position in terms of rectum dosimetry. The bladder dose in the N position is considerably lower than that in the other positions.