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  • Küçük Resim Yok
    Öğe
    Current practices of craniospinal irradiation techniques in Turkey: a comprehensive dosimetric analysis
    (Bmc, 2024) Senkesen, Oeznur; Tezcanli, Evrim; Alkaya, Fadime; Ispir, Burcin; Catli, Serap; Yesil, Abdullah; Bezirganoglu, Ebrar
    Objective This study evaluates various craniospinal irradiation (CSI) techniques used in Turkish centers to understand their advantages, disadvantages and overall effectiveness, with a focus on enhancing dose distribution. Methods Anonymized CT scans of adult and pediatric patients, alongside target volumes and organ-at-risk (OAR) structures, were shared with 25 local radiotherapy centers. They were tasked to develop optimal treatment plans delivering 36 Gy in 20 fractions with 95% PTV coverage, while minimizing OAR exposure. The same CT data was sent to a US proton therapy center for comparison. Various planning systems and treatment techniques (3D conformal RT, IMRT, VMAT, tomotherapy) were utilized. Elekta Proknow software was used to analyze parameters, assess dose distributions, mean doses, conformity index (CI), and homogeneity index (HI) for both target volumes and OARs. Comparisons were made against proton therapy. Results All techniques consistently achieved excellent PTV coverage (V95 > 98%) for both adult and pediatric patients. Tomotherapy closely approached ideal Dmean doses for all PTVs, while 3D-CRT had higher Dmean for PTV_brain. Tomotherapy excelled in CI and HI for PTVs. IMRT resulted in lower pediatric heart, kidney, parotid, and eye doses, while 3D-CRT achieved the lowest adult lung doses. Tomotherapy approached proton therapy doses for adult kidneys and thyroid, while IMRT excelled for adult heart, kidney, parotid, esophagus, and eyes. Conclusion Modern radiotherapy techniques offer improved target coverage and OAR protection. However, 3D techniques are continued to be used for CSI. Notably, proton therapy stands out as the most efficient approach, closely followed by Tomotherapy in terms of achieving superior target coverage and OAR protection.
  • Küçük Resim Yok
    Öğe
    Düzensiz toraks ve mediasten alanlarına kobalt-60 ile teleterapi uygulamalarında koruma bloklarının doz parametrelerine etkisi
    (2000) Gürsoy, Tamer Oğuz; Alkaya, Fadime; Kemikler, Gönül; Baş, Murat
    RT'de kritik organların korunması amacıyla ışın alanı içine konulan bloklar, korunmuş volümden ışın saçılmasını azaltarak, açık alanın doz dağılımlarının değişmesine neden olurlar. Düzensiz alanların % DD (Derindoz) değerlerinin bulunmasına ilişkin çeşitli metodlar geliştirilmiştir. Rutinde kııllanılan bıı metodların ölçümlerle geçerliliğinin incelenmesi gereklidir. Bu çalışmada çeşitli düzensiz alanların ölçülen %DD'ları, KE (negatif alan ) ve [4x(A/P)] yönterniyle bulunan alanların % DD değerleri ile karşılaştırılmış,bloklu ve açık alan doz verimleri ölçülmüştür. Ayrıca üç derinlikte (05 , 5 ve 10 cm derinlikler için) açık ve bloklu alanların doz profilleri çizdirilmiş ve bloklamanın açık alan doz profiline olan etki s i incelenmiştir. Seçilen düzensiz alanlarda yapılan DD % ölçümleri ile yoğurı bloklamanın yapıldığı akciğer ve mediasten alanında, [4x(A/P)] yöntemi, KE yöntemine göre daha iyi sonıuç vermiştir. Ancak, her iki hesaplama yöntemi de blok kenarındaki noktalar hariç DD% 'leri için uygundur. Her kliniğin kendi hesaplama yöntemini kendi koşullarında belirmesi uygun olacaktır. Bu çalışrmada kullanılan alanlarda blok altındaki dozlar, tüm alanlar için d max'ın '% 10'u civarındadır.
  • Küçük Resim Yok
    Öğe
    The Effects of Micronuclei with Whole Chromosome on Biological Dose Estimation
    (Tubitak Scientific & Technological Research Council Turkey, 2008) Pala, Funda S.; Alkaya, Fadime; Tabakcioglu, Kiymet; Tokatli, Fuesun; Uzal, Cem; Parlar, Sule; Alguenes, Cetin
    The total micronucleus (MN) assay has been used for purposes of biological dosimetry for many years. The variable spontaneous incidence of micronuclei in peripheral blood lymphocytes affects the sensitivity of biological dose estimations at low doses. It has been suggested that this problem could be solved by using the micronuclei-centromere assay. In this study. Co-60 gamma ray dose response curves for micronuclei (MN) and micronuclei without centromeres (MNC-) in the range of 0-5.0 Gy were established using a pancentromeric FISH probe on cultured binucleate lymphocytes from 2 donors. There were no significant inter-donor differences in the dose responses for either MN or MNC-. The relative proportions of MN that contained centromeres (MNC+) decreased with radiation dose, which is in line with the proposition that radiation predominately causes chromosomal breakage rather than whole chromosome loss. The a coefficients of MNC- curves decreased to 62% of the values for total MN whilst the beta coefficients were unchanged. MN and MNC+ frequencies of 60 control smoker and 40 non-smoker donors were also compared. No effect of smoking was observed. However the MNC+ spontaneous frequencies showed an age and gender effect with the highest frequencies in older women.