Dose Optimization of Electron Arc Treatment Technique in Chest Wall Beams after Mastectomy

In breast cancer, electron energies are preferred over photon energies because they provide minimal lung exposure when conditions allow for thin chest wall irradiation after mastectomy. In patients with irregular chest wall, it is difficult to perform a homogeneous irradiation with fixed electron beam therapy due to reasons such as thickness differences, irregular contour and lack of tissue, long scar and area joint problems. Electron arc therapy is propose as an alternative method in such patients. The study was carried out with electron energies of 6, 9, 12, 13.5 and 16 MeV. First, in order to be able to use it in electron arc planning in the planning system, after determining the dose characteristics of all available electron energies of the electron arc technique, the accuracy of these dose distributions was verified with film and TLD dosimetry. After the suitability was determined, electron arc plans were made on the CT simulation image of 20 patients selected due to the difficulty of homogeneous irradiation with the classical method. While the chosen reference dose of 85%25 covered the PTV homogeneously, it was found that the dose was decreased by an average of 50%25 compared to photon and classical electron therapy in the examination performed in terms of radiation dose to which the lung volume was exposed. During the planning, a homogeneous dose and bolus of different thicknesses were required depending on the energy in most patients to regulate the reduction in surface dose depending on the arc angle. Bolus prevents the lung and heart from overdosing while ensuring that the dose in the deeper parts of the target volume is more uniform. The use of tertiary block in electron-arc dose distributions prevented unwanted dose reduction in the field edges and provided a more homogeneous dose distribution at 85%25 reference isodose. If the structure of the patient%252339%253Bs contour is very irregular, the dose distribution is not smooth due to the depth difference. In this context, it has been determined that during optimization, the isocenter depth should be chosen for the homogeneity of the dose distribution and to be as equal as possible from the surface at all beam angles. In addition, in the study, it was determined that more appropriate dose distributions were obtaine when the isocenter depth is greater than the maximum reach of electrons. Even if multiple electron fields of different energies are used, more homogeneous dose distributions have been achieve by eliminating field combination problems with the use of electron arc therapy

Determining The Accuracy of Dwell Position by Using Electron Energy with Gafchromic Film in High Dose Rate Brachytherapy Systems

Due to the general lack of darkroom and film processing equipment in many clinics, it is no longer possible to use radiation sensitive Xomat V radiographic film for High Dose Rate brachytherapy quality assurance. An alternative is to use radio chromic film that does not require processing. The aim of this study is to develop and clinically test the GafChromic film-based brachytherapy Quality Assurance (QA) system using different electron energies. As an electron source (6 MeV-9 MeV-12 MeV -15 MeV -18 MeV) (Elekta Synergyreg%253B Platform linear accelerator, Varian GM plus IX (Varian Medical Systems, Inc.USA), Varian brand cylinder, ring and tandem double ovoid applicators, RTQA2 and EBT3 GafChromic film were used. In RTQA2 films, images are obtained at high electron energies (12 MeV and above) at 300 Monitor Unit (MU), while images are obtained at all energies at 700 MU in irradiation using different electron energies and MUs. For the desired image quality depending on the material of the applicator used, it was determined that the image clarity increased as the energy, field size and MUs increased. In EBT3, the desired image could be obtained at 18 MeV and 2500 MU. It is possible to obtain the desired image quality by using high-energy electrons, especially RTQA2 Gafchromic film, in determining the accuracy of the dwell position in brachytherapy. Since it has been determined that this method can be used easily in quality control tests, we think that this method is suitable for clinical use when necessary

A Rare Mimicker of an Adrenal Carcinoma: Co-occurrence of Hemorrhagic Pseudocyst and Myelolipoma

Adrenal collision tumors are rare tumors composed of two different benign or malignant tumors in the adrenal gland. Radiological features are very helpful in the diagnosis, however it is not always possible to make a definite diagnosis with imaging findings alone because the coexisting masses contain different tissue components. In this paper, we report the imaging findings of an adrenal lesion with pseudocyst and myelolipoma mimicking an adrenocortical carcinoma in a 42-year-old female patient. To the best of our knowledge, this is the first reported case of an adrenal lesion containing myelolipoma and hemorrhagic pseudocyst mimicking an adrenal carcinoma in the literature

ELEKTRON ARK IŞINLAMASINDA X-IŞINI KONTAMİNASYONU

Mastektomi sonrası toraks cidarı düzensiz olan hastalarda kalınlık farklılıkları, düzensiz kontur, doku eksikliği, uzun skar ile birlikte alan birleşim problemleri gibi nedenlerden dolayı sabit elektron huzme tedavisi ile homojen bir ışınlama yapmak zordur. Bu gibi hastalarda elektron ark tedavisi alternatif bir yöntemdir. Elektron ark tedavisi sırasında hastaya istenmeyen foton dozu verilir. Bu çalışmada, elektron ark ışınlaması sırasında enerjiye ve ark açısına bağlı olarak oluşan foton dozu (x-ışını kontaminasyonu) araştırılmıştır. Çalışmada 6-16 MeV elektron enerji kademelerine sahip Saturne 41 lineer hızlandırıcı, X-OMAT-V verifikasyon filmi, silindirik fantom, piksel manuel dansitometre kullanıldı. 5x30 cm2 alanda 0°, 60°, 90°, 120°, 180° ark açılarında, 6, 9, 13.5, 16 MeV enerjileri için silindirik fantomda, izosantrik olarak ışınlanan verifikasyon filmlerinde x-ışını kontaminasyonu dansitometre yardımıyla değerlendirildi, izosantır derinliği 15 cm olarak alındı. Film dozimetrisi ile elde edilen %DD eğrilerinde, izosantır derinliği civarında dozun yükselme eğiliminde olduğu gözlendi. Bu yükselme enerji ve ark açısı ile artmakta ve maksimum doz noktasına göre %26.5'lere kadar çıkmaktadır. 6 MeV elektron enerjisinde bu değer 0° ark açısında %5.5 iken, ark açısı arttıkça yükselmekte ve 180° ark açısında %22.5 olmaktadır. Benzer şekilde 16 MeV elektron enerjisinde 0° ark açısında %10 iken, 180° ark açısında %26.5'lere ulaşmaktadır. Dozdaki bu artış bremss ışınlarının (x-ışını) kontaminasyonundan kaynaklanmaktadır. Elektron ark tedavisi, eğri yüzeyleri takip eden geniş yüzeyel tümörlerin tedavisinde önemli rol oynamaktadır. Bu tedavi sırasında izosantır çevresindeki x-ışını kontaminasyonu arttığından, izosantırın yerleşiminde kritik organlara dikkat edilmesi ve tedavi planlaması sırasında x-ışını kontaminasyonunun dikkate alınması gerekmektedir