Gokcen Inan

Objective: The present study aims to compare field-in-field (FIF) radiation therapy, static intensity-modulated radiation therapy (S-IMRT), and dynamic static intensity-modulated radiation therapy (D-IMRT) techniques concerning dosimetric benefits for the treatment of pancreatic cancers. Materials and Methods: Sixteen pancreatic cancer patients who had undergone radiotherapy were selected for this study FIF, D-IMRT and S-IMRT plans were compared with respect to the planning target volume (PTV) and organs at risk (OARs). All plans were designed to cover 95% of the dose in the target. Also, homogeneity index (HI), conformity index (CI) and the monitor unit counts (MUs) were evaluated for all plans. Paired sample t-test was used for statistical analyses. Results: The CI and HI for D-IMRT and S-IMRT plans showed significant positive results than FIF plans. S-IMRT resulted in significantly reduced bilateral kidney V10 and V20 doses relative to FIF and D-IMRT plans (p

Aim: The purpose of this study is to compare plans for bladder cancer using field-in-field (FIF), intensity modulated radiotherapy (IMRT) and simultaneous integrated boost (SIB) technique.Method: FIF, IMRT and SIB treatment plans were created using tomography images of 20 patients diagnosed with bladder cancer. Two separate planning target volume (PTV) were defined for each patient: PTV1 and PTV2. For the FIF and IMRT plans, PTV1 and PTV2 received treatment doses of 50.4 Gray (Gy) and 60 Gy in 33 fractions, respectively. In 28 daily fractions, the SIB method was used in which different doses were delivered simultaneously in the target volumes. In the SIB technique, the daily treatment dose was determined as 2.14 Gy. The plans were compared in terms of PTV, organs at risk (OARs) such as rectum, bowel, femoral heads, homogeneity index (HI), conformity index (CI) and monitor unit values (MU).Results: All plans were designed to cover 95% of the dose in the target volume. The CI for SIB plans showed significantly favourable results compared to FIF and IMRT plans. The V45 and V30 doses for the rectum in the SIB plans were statistically significantly lower compared to the FIF (p<0.05). The biologically effective doses (BED) values of rectum V30 were found to be 57.01±11.94 in SIB plans and 56.37±10.95 in IMRT plans. MU counts were significantly lower in FIF plans (p<0.05).Conclusion: The SIB technique demonstrated better sparing of critical organs compared with FIF and IMRT in bladder radiotherapy. BED analysis, however, indicated higher doses with SIB. Overall, SIB appears to be a feasible option for appropriate patients, provided that dose to critical organs is carefully monitored.

Objectives: In this study, we aimed to determine the incidence and clinical features of uterine perforation during our 3-dimensional image-guided adaptive brachytherapy applications in patients with cervical cancer. Materials and Methods: Between 2010 and 2017, 155 patients with the diagnosis of stage IB1-IVA cervical cancer were retrospectively evaluated. All patients received 40 mg/m2 cisplatin concurrent with external-beam radiotherapy to 50.4 Gy in 28 fractions, followed by intracavitary brachytherapy (BRT) to 28 Gy in 4 fractions. BRT was performed using tandem-based intracavitary BRT with ovoids, with a computed tomography (CT) based image-guided adaptive BRT method. Seventy-four (47.7%) patients had magnetic resonance imaging (MRI) just after EBRT, before BRT application. Results: Of the 155 patients, nine (5.8%) had uterine perforation, and among 620 applications, 12 (1.9%) resulted in uterine perforation. The median age of patients with perforation was higher (63 years; range 44-84 years) than that of patients without perforation (52 years; range 29-85 years). The median pre-treatment tumor size, based on CT and/or positron emission tomography (PET)-CT imaging before EBRT, was 6.5 cm for patients with perforation and 5.0 cm for those without perforation. Five of the perforations were in retroverted uterine position (55.6%), and two were in anteverted uterine position (22.2%). The retroflexed case was included in the retroverted group. The Pearson chi-square test showed that older age (p=0.026), larger tumors (p=0.024), and a retroverted uterine position (p

We investigated dosimetrically lymphopenia concerning radiotherapy (RT) in patients receiving pelvic RT due to locally advanced prostate cancer (LAPCA). A total of 195 patients with lymph node-positive LAPCA were retrospectively evaluated and included in this single-center study. The relationship among absolute lymphocyte count (ALC), treatment modality, clinical stage, RT dose, and existence of pre-RT and post-RT lymphopenia (Grade≥2) was evaluated. Dependent McNemar analyses revealed significant relationship in pre-RT and post-RT (p<0.001). Of those with Grade<2, 108 (56.5%) developed Grade≥2 post-RT lymphopenia (p<0.001). V20-whole pelvic bone marrow (WPBM) (p=0.036), V30-WPBM (p=0.025), and V50-WPBM (p=0.008) values were significantly higher in Grade≥2 lymphopenia group. Also, V5-lumbo-sacral BM (LSBM) (p=0.013), V10-LSBM (p=0.041), V20-LSBM (p=0.015), and V30-LSBM (p=0.007) values were significant in Grade≥2 lymphopenia group. However, V30-lower-pelvis BM (LPBM) (p=0.024) and V50-LPBM (p<0.001) values were significant in Grade≥2 lymphopenia group. ROC analysis showed a significant effect on the development of Grade≥2 lymphopenia post-RT. Pre-RT baseline ALC values were associated with the development of Grade≥2 lymphopenia at a cut-off value of ≤1805 (p<0.001). Additionally, cut-off values of ≥76.1% for V20-WPBM (p=0.036), ≥47.3% for V30-WPBM (p=0.021), ≥7.3% for V50-WPBM (p=0.008), ≥68.5% for V30-WPBM (p=0.007), ≥41.2% for V30-LPBM (p=0.023), and ≥4.3% for V50-LPBM (p=0.001) were associated with development of Grade≥2 lymphopenia. Among all dosimetric parameters, V50-LPBM emerged as the strongest predictor of Grade ≥2 lymphopenia after RT. In clinical evaluations, no significant difference was seen in OS or PFS between Grades ≥2 and <2 groups (OS: p=0.194; PFS: p=0.489). This study demonstrated the clinical importance of pre-RT hematologic status and BM dosimetry, demonstrating that low pre-RT ALC and V50-LPBM values were the most significant predictors of Grade ≥2 lymphopenia after PNRT. These findings highlight importance of considering BM as an organ at risk and considering appropriate BM-sparing strategies in PNRT planning.

Aim: This study investigated the dose calculation accuracy of different treatment planning algorithms used in radiotherapy patients with hip prostheses. Method: The current research produced a tissue-equivalent cylindrical phantom that imitates a leg using a 3D printer. Co-Cr-Mo alloy and Ti-6AI-4V alloy prostheses were placed in the centre of the phantom, respectively. Both prostheses' dose measurements were taken with thermoluminescent dosimeters (TLD) at 92 points. The dose calculation accuracy of the Analytical Anisotropic Algorithm (AAA) and Pencil Beam Convolution (PBC) algorithms, widely used in radiotherapy, were compared with the measurement results. Results: Since the Co-Cr-Mo hip prosthesis has a high density, the number of backscattered photons around it was higher than the Ti-6AI-4V hip prosthesis. The average surface dose of the Co-Cr-Mo alloy was 364.05 cGy, while the average surface dose of the Ti-6AI-4V alloy was 347.79 cGy. Conclusion: It was observed that the dose estimation abilities of the AAA and PBC algorithms decreased as the density of the hip replacement increased. In addition, the AAA algorithm predicted the surface dose in the phantom better than the PBC algorithm.

Background/Aims: Different optimization methods in brachytherapy treatment planning is used. The aim of this study is to evaluate dosimetric differences between manual optimization (MO) and inverse planning simulated annealing (IPSA) planning techniques commonly used in brachytherapy of cervical cancer. Methods: Fifteen cervical cancer patients were included in this study. Nucletron standard tandem-ovoid (TO) applicators were used for treatment. High-risk clinical tumor volume (HR-CTV), bladder, rectum, and sigmoid contouring were performed according to GEC-ESTRO recommendations. Two plans were created for each patient using IPSA and MO techniques. While a dose of 700 cGy was prescribed to the target volume during the planning phase, an effort was made to protect the organs at risk in the best way possible. IPSA and MO planning techniques were compared via dose volume histogram (DVH). Results: There was no significant difference between HR-CTV and CI values for MO and IPSA techniques. There was a significant difference between IPSA and MO techniques for the 2cm3 volume of the rectum (p= 0.002). It was observed that the bladder was better protected by the IPSA technique. There was a 6.26% dose difference between IPSA and MO for the bladder. A significant difference was found between IPSA and MO techniques for the 2cm3 volume of the sigmoid (p= 0.002). The IPSA technique was superior to the MO technique in terms of time. Conclusions: The IPSA technique was superior to the MO technique in terms of protecting organs at risk (OARs). IPSA provides a faster and higher quality plan in cervical brachytherapy.

Amaç: Meme kanserinde radyoterapi (RT) uygulaması hastalığın kontrolünde ve sağkalımında önemli bir yere sahiptir. Genel sağkalım sürelerinin artmasına bağlı olarak meme kanseri tedavisinde görülen yan etkilerin önemi artmıştır. Bu çalışmada RT uygulanan meme kanseri olgularda, brakial pleksus, karotis arter ve tiroid dozlarının değerlendirilmesi amaçlandı. Yöntem: Çalışmamızda radikal mastektomi yapılmış 15 sol meme kanseri hastaya, alan içinde alan (Field in Field (FinF)), statik yoğunluk ayarlı radyoterapi (S-YART) ve dinamik yoğunluk ayarlı radyoterapi (D-YART) teknikleri ile üç farklı radyoterapi planları hazırlandı. Planlar planlanan hedef hacim (Planned Target Volume-(PTV)) dozları, konformite indeksi (CI) ve homojenite indeksi (HI) açısından değerlendirildi. Kritik organlar olarak brakial pleksus, sol karotis arter ve tiroid dozları karşılaştırıldı. Bulgular: PTV’ nin aldığı ortalama dozlar üç teknik içinde benzer bulundu. Tiroidin Dort, V20, V30 (Gy) doz değerleri S-YART tekniğinde, FinF ve D-YART tekniklerine göre anlamlı olarak azaldı (p<0.05). Tiroidin V45 (Gy) değeri ise D-YART ve S-YART tekniklerinde anlamlı olarak azaldığı görüldü (p değerleri sırasıyla 0.006, 0.005). Brakial pleksus Dort (Gy) ve V45 (Gy) değerleri D-YART ve S-YART tekniklerinde FinF tekniğine göre anlamlı olarak daha düşük bulundu (p<0.05). Sol karotis arter Dort değeri S-YART tekniğinde anlamlı olarak azaldı (p=0.012). Sonuç: Radikal mastektomi uygulanmış sol memeye yönelik radyoterapi tedavisinde brakial pleksus, sol karotis arter ve tiroid dozlarının S-YART ve D-YART tekniklerinde daha iyi korunduğu bulundu. Hastalara tedavi planı seçimlerinde bu kritik yapıların aldığı dozlara bakılarak kişiye uygun planlama tercih edilmelidir.