1. A protocol for accurate radiochromic film dosimetry using Radiochromic.comIgnasi Méndez Carot, Juan José Rovira-Escutia, Božidar Casar, 2021, izvirni znanstveni članek Povzetek: Radiochromic films have many applications in radiology and radiation therapy. Generally, the dosim-etry system for radiochromic film dosimetry is composed of radiochromic films, flatbed scanner, and film analysis soft-ware. The purpose of this work is to present the effectiveness of a protocol for accurate radiochromic film dosimetry using Radiochromic.com as software for film analysis.Materials and methods. Procedures for image acquisition, lot calibration, and dose calculation are explained and analyzed. Radiochromic.com enables state-of-the-art models and corrections for radiochromic film dosimetry, such as the Multigaussian model for multichannel film dosimetry, and lateral, inter-scan, and re-calibration corrections of the response.Results. The protocol presented here provides accurate dose results by mitigating the sources of uncertainty that affect radiochromic film dosimetry. Conclusions. Appropriate procedures for film and scanner handling in combination with Radiochromic.com as software for film analysis make easy and accurate radiochromic film dosimetry feasible.
Ključne besede: radiochromic film, dosimetry, protocol
Objavljeno v DiRROS: 22.07.2024; Ogledov: 520; Prenosov: 281
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2. Experimental validation of Monte Carlo based treatment planning system in bone density equivalent mediaĐeni Smilović Radojčić, Božidar Casar, David Rajlić, Manda Švabić Kolacio, Ignasi Méndez Carot, Nevena Obajdin, Dea Dundara Debeljuh, Slaven Jurković, 2020, izvirni znanstveni članek Objavljeno v DiRROS: 16.07.2024; Ogledov: 470; Prenosov: 122
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3. Evaluation of two-dimensional dose distributions for pre-treatment patient-specific IMRT dosimetryĐeni Smilović Radojčić, David Rajlić, Božidar Casar, Manda Švabić Kolacio, Nevena Obajdin, Dario Faj, Slaven Jurković, 2018, izvirni znanstveni članek Povzetek: The accuracy of dose calculation is crucial for success of the radiotherapy treatment. One of the methods that represent the current standard for patient-specific dosimetry is the evaluation of dose distributions measured with an ionization chamber array inside a homogeneous phantom using gamma method. Nevertheless, this method does not replicate the realistic conditions present when a patient is undergoing therapy. Therefore, to more accurately evaluate the treatment planning system (TPS) capabilities, gamma passing rates were examined for beams of different complexity passing through inhomogeneous phantoms. Materials and methods The research was performed using Siemens Oncor Expression linear accelerator, Siemens Somatom Open CT simulator and Elekta Monaco TPS. A 2D detector array was used to evaluate dose distribution accuracy in homogeneous, semi-anthropomorphic and anthropomorphic phantoms. Validation was based on gamma analysis with 3%/3mm and 2%/2mm criteria, respectively. Results Passing rates of the complex dose distributions degrade depending on the thickness of non-water equivalent material. They also depend on dose reporting mode used. It is observed that the passing rate decreases with plan complexity. Comparison of the data for all set-ups of semi-anthropomorphic and anthropomorphic phantoms shows that passing rates are higher in the anthropomorphic phantom. Conclusions Presented results raise a question of possible limits of dose distribution verification in assessment of plan delivery quality. Consequently, good results obtained using standard patient specific dosimetry methodology do not guarantee the accuracy of delivered dose distribution in real clinical cases
Ključne besede: IMRT, 2D dose verification, gamma method, antropomorphic phantom
Objavljeno v DiRROS: 10.06.2024; Ogledov: 583; Prenosov: 291
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5. Evaluation of water equivalency of Plastic waterTM for high-energy electron beams using IAEA TRS-398 code of practiceBožidar Casar, Urban Zdešar, Vlado Robar, 2004, izvirni znanstveni članek Povzetek: Electrochemotherapy (ECT) is a novel method for efficient tumor treatment in clinical environment. It combines local drug delivery and application of shorthigh voltage pulses, which permeabilize the plasma membrane by electroporation. Drug can enter only the cells with permeabilzed membrane. Recently, medical device CliniporatorTM for controlled electroporation was developed. Here, we present a web-application that extends the functionality of this medical device. The aim of the application is to collect, store and toallow the analysis of every ECT application using this medical device. The application helps transferring data collected by dev;ce during the electroporation process to the central database, and enables filling of medical records through the web forms. The application is based on technologies ASP, HTML, Flash, JavaScript, XML and others. The application main advantages are easy and rapid data access, scalability and independence of client computer operating system as well as easy application debugging and upgrading.
Objavljeno v DiRROS: 13.02.2024; Ogledov: 727; Prenosov: 152
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6. Tertiary collimator system for stereotactic radiosurgery with linear acceleratorBožidar Casar, 1998, izvirni znanstveni članek Povzetek: In the last decade, stereotactic radiosurgery (SRS) with linear accelerator (linac) has become an important irradiation technique for a variety of malignant and benign intracranial lesions. Although there exist some other radiosurgery techniques, linac based SRS meets the requirements needed for SRSwith low cost modifications. On of the most important additional parts of the equipment is tertiary collimator system which can be attached onto the linac head. We designed and built such system that can be easily fixed onto linac PHILIPS SL - 75/5 with 5 MV photon energy. In our department, we alreadyuse this linac for conventional radiation therapy. Our tertiary collimator system meets all the requirements important for this special modality of radiation therapy. It allows fine centering of the system and has ten various collimators with divergent circular openings having a nominal field diameter ranging from 1.0 cm to 4.0 cm at the isocenter. The accuracy ofthe system was checked by exposing x - ray films at various gantry positions, and recording misalignment of the beams. The width of penumbra was determined using two different dosimetry techniques (film dosimetry and diode measurements).
Objavljeno v DiRROS: 19.01.2024; Ogledov: 606; Prenosov: 165
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7. A novel approach for the definition of small-field sizes using the concept of superellipseIgnasi Méndez Carot, Božidar Casar, 2021, izvirni znanstveni članek Povzetek: In radiotherapy, field sizes are defined in terms of the dimensions of the irradiation area. However, geometric square fields result in irradiation areas with rounded corners, which become almost elliptical for small fields. Superellipses are a family of curves encompassing shapes lying between ellipses and rectangles. The purpose of this work was to analyze the advantages and disadvantages of a novel approach that describes small-field sizes with superellipses. Square fields with nominal side lengths ranging from 0.5 to 10 cm were irradiated with two different linacs using 6 and 10 MV photon beams with and without flattening filters. Field size dimensions and output factors were measured by employing radiochromic films and the Radiochromic.com software. An alternative definition of equivalent square small-field size based on the superellipse (Sse) was introduced. The degree n of the superellipse for 10 cm nominal fields measured between 14.8 % 1.0 to 27.7 % 1.9. However, it decreased with the field size, down to between 2.26 % 0.10 and 2.64 % 0.15 for 0.5 cm nominal side lengths. A relation between the degree n and the equivalent square small-field size (Sclin) as defined by Cranmer-Sargison et al. [%A methodological approach to reporting corrected small field relative outputs,% Radiotherapy and Oncology 109, 350%355 (2013)] was found. For nominal side lengths of 10 cm, Sse was between 0.34 % 0.04% and 0.10 % 0.01% smaller than Sclin, while for 0.5 cm nominal side length Sse was between 9.5 % 0.6% and 7.4 % 0.7% smaller than Sclin. There was no significant difference in the goodness of the regression between using Sse or Sclin to fit field output factors with the function proposed by Sauer and Wilbert. Small fields were found to be more accurately characterized with superellipses. The advantages and disadvantages of describing field sizes with superellipses were examined. Field output factors can be derived with equivalent square small-field sizes based on the superellipse approach.
Ključne besede: superellipsa, small fields, dosimetry, radiotherapy
Objavljeno v DiRROS: 07.09.2022; Ogledov: 909; Prenosov: 576
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8. Učinki obsevanja dela tumorja na imunske populacije na tumorskem modelu mišjega karcinoma dojke 4T1Tanja Jesenko, Živa Pišljar, Tim Božič, Simona Kranjc Brezar, Ilija Vojvodić, Božidar Casar, Ignasi Méndez Carot, Maja Čemažar, Gregor Serša, Boštjan Markelc, 2022, objavljeni povzetek znanstvenega prispevka na konferenci Ključne besede: radioterapija, tumorski modeli, eksperimentalna onkologija
Objavljeno v DiRROS: 17.06.2022; Ogledov: 1328; Prenosov: 357
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