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    Dosimetric comparison of helical tomotherapy and hybrid (3DCRT-VMAT) technique for locally advanced non-small cell lung cancer
    (Cambridge Univ Press, 2021) Temelli, Oztun; Demirtas, Mehmet; Ugurlu, Berat Tugrul
    Aim: The purpose of the present study is to compare hybrid [three-dimensional conformal radiation therapy-volumetric-modulated arc therapy (3DCRT-VMAT)] and helical tomotherapy (HT) techniques in terms of both planning target volume (PTV) and organs at risk (OARs) in the plans we made in locally advanced non-small cell lung cancer (NSCLC) patients Material and methods: Radiotherapy was planned for 15 locally advanced NSCLC patients with 2 different techniques. Large tumours with positive mediastinal lymph nodes were preferred. The prescription dose was determined as 60 Gy at 30 fractions. Results: Mean PTV volume was 602 center dot 5 cc (range: 265-1461). Mean total lung volume was 4264 cc (range: 1885-6803). Homogeneity index, D-mean, D-max, D-2 and V-105 were found to be lower in HT, V-100, total monitor units (MU) and total beam on time were found to be lower in the hybrid plan. Total lung D-mean was found to be 17 Gy in both techniques. V-10 value was 42 center dot 85 in the hybrid plan and 48 center dot 67 in HT (p = 0 center dot 037). Heart D-mean was 14 center dot 5 Gy in the hybrid plan and 18 center dot 7 in HT (p < 0 center dot 001), and V-30 values were 18 center dot 1 and 22 center dot 9, respectively (p = 0 center dot 009). Conclusion: Suitable dose coverage and OAR doses can be provided with both techniques. Especially the opposite lung, heart and oesophagus doses can be kept lower with the hybrid plan, and lower MU and shorter beam on time can be provided.
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    Dosimetric Evaluation of Deep Inspiration Breath-Hold Technique for Breast Cancer Radiotherapy: A Single-Center Experience
    (Kare Publ, 2020) Temelli, Oztun; Demirtas, Mehmet; Ugurlu, Berat Tugrul; Pepele, Eda Kaya; Yaprak, Bahaddin; Gulbas, Hulya; Eraslan, Fatma Aysun
    OBJECTIVE To retrospectively evaluate the absorbed doses of organs at risk, such as lungs and the heart of the patients who underwent radiotherapy (RT) using the voluntary deep inspiration breath-hold (vDIBH) technique, and to compare the results with the literature. METHODS In this study, 102 patients who underwent adjuvant RT for the treatment of breast cancer in our clinic between November 2018 and December 2019 were included. A breast and/or chest wall, and/or lymph node RT of 50 Gy in 25 fractions was planned for all patients, and an additional boost of 10 Gy in five fractions was planned for patients requiring an RT boost. The treatment plans included 3DCRT, Field in Field (FIF), IMRT and VMAT approaches. RESULTS In the group undergoing supraclavicular fossa RT, the mean V20Gy was found to be 24.8%, compared to 16% in the group not undergoing supraclavicular fossa RT (p<0.01). In the group undergoing mammaria interna RT, the mean heart dose was 3.1 Gy, compared to 2.1 Gy in the group not undergoing mammaria interna RT (p=0.04). CONCLUSION Respiratory motion control techniques can reduce uncertainties in the target related to respiratory motion. The irradiated volume doses of the ipsilateral lung, heart reduce.
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    The impact of the field width on VMAT plan quality and the assessment of half field method
    (Wiley, 2020) Ugurlu, Berat Tugrul; Temelli, Oztun
    Purpose The goal of this work is to investigate the field width dependence of the volumetric modulated arc therapy (VMAT) plan quality and to propose a half field method to irradiate large volumes effectively with VMAT. Materials and methods We compared four different VMAT methods; namely three full field (3ff), four full field (4ff), three half field (3hf), four half field (4hf). To evaluate the impact of the field width on VMAT plan quality, 12 different size PTVs were created in the virtual phantom and treatment plans generated for each PTV were compared. The effectiveness of our half field method was tested using computed tomography (CT) data of 10 nasopharyngeal carcinoma patients. Results In the virtual phantom study, organs at risk (OAR) mean dose, the maximum point dose, and Homogeneity Index (HI) were found to be field width dependent. Conformation Number (CN) was not significantly affected. In the clinical study, 4hf plans obtained statistically significant dose reduction at brainstem (P < 0.001), right parotid (P = 0.034), oral cavity (P < 0.001), larynx (P = 0.003), cochlea (P = 0.017), lips (P = 0.024), and Body-PTV (P = 0.04) compared to 4ff plans. Conclusion Our results indicate that VMAT plan quality is dependent on the field width. Half field VMAT method, with the help of reduced field width, shows a clear advantage for the irradiation of large size targets compared to traditionally used full field VMAT plans.