Evaluation of the dose distribution of half-beam abutted fields in head and neck cancer by film dosimeter and computer based planning system [Baş-boyun bölgesi kanserlerinde yari{dotless}m demet bitişik alan doz dagi{dotless}li{dotless}mlari{dotless}ni{dotless}n film dozimetrisi ve bilgisayarli{dotless} planlama sistemi ile degerlendirilmesi]

OBJECTIVES The aim of this study is to determine the dose inhomogenity in abutted fields-formed by using single isocentre and asymmetric collimators by film dosimetry and TPS in the radiotherapy of HN cancer. METHODS Using different SSD's for supraclavicular and lateral fields asymmetric collimators were set to 0 mm, 1 mm, 2 mm position and treatment planning was done for 45 different situations. Films were irradiated, dose distribution along the junction were determined. RESULTS 2 mm and 1 mm overlap and gap produced 22% and 13% overdose, 21% and 15% underdose respectively. 0 mm the dose nonuniformity is about 2%. The difference in dose profiles along the junction obtained from films and TPS wasn't statistically significant. TPS and linear accelerator were in accordance with each other. Besides the penumbra and scattered radiation also contributed to the uniformity of dose distribution along the junction point. CONCLUSION Single-isocentre technique produces a dose similar to the prescribed tumor dose along the field junction. The dose distribution is homogeneous at 0 mm and treatments were delivered with accuracy. © 2013 Association of Oncology

Evaluation of the dose distribution behind the prostheses in prostate cancer patients with hip prostheses using film dosimetry and specially designed phantom [Kalça protezli prostat kanseri hastalari{dotless} için protez arkasi{dotless}ndaki doz dagi{dotless}li{dotless}mi{dotless}ni{dotless}n film dozimetre ve özel olarak tasarlanmi{dotless}ş fantom kullani{dotless}larak degerlendirilmesi]

OBJECTIVES: We aimed to investigate the effect of hip prostheses on dose distribution in radiotherapy patients. METHODS: Solid Water phantom-containing prostheses (cobalt-chromium-molybdenum and cobalt-chromium-molybdenum-titanium) were placed between the phantoms used for the measurements. Films at 10, 20 and 30 cm depths were irradiated for 6 and 18 MV with 50 cGy dose in the presence or not of prosthesis. Dose profiles were evaluated statistically. RESULTS: For 6 and 18 MV photon energies, significant differences was found along the thick and vertical axes of both prostheses at 10 and 20 cm depths and along the middle, thick and vertical axis at 30 cm depth (p<0.05). CONCLUSION: Hip prostheses affect radiotherapy dose distribution, and this should be considered when planning a treatment. © 2012 Association of Oncology

Three-dimensional planning techniques

Breast cancer is the leading type of cancer found in women. Radiotherapy is commonly administered in this type of cancer, as well as surgery, chemotherapy, and hormone therapy. Conventionally, two-dimensional (2D) wedge compensators have been used for many years; however, in parallel with the advancement of medical technologies, they have been upgraded and replaced by more advanced three-dimensional conformal radiotherapy (3D-CRT) technique. Particularly with the use of computed tomography (CT) in radiotherapy treatment simulation and planning, tumor location can be determined more confidently, and highly homogenous and conformal radiation dose distributions can be obtained. Thus, unintended high radiation doses can be reduced in the critical structures such as the skin, lung, and hear, so that early and late adverse effects are ensured to be decreased. Planning and implementation of the 3D-CRT have improved over the course of time through developments concerning medical technology and expert-level experience. Through developing different techniques, improved patient comfort, accurate applicability, and further reduction in the adverse effects are ensured [1]. © Springer Science+Business Media New York 2013

The effect of CT-MR image registration on target volume delineation and dose distribution in radiotherapy planning of brain tumors [Beyin tu;mo;rlerinin radyoterapi planlamasi{dotless}nda, bt ve mrg go;ru;ntu; eş leştirilmesinin hedef volu;m belirlenmesine vedoz dagi{dotless}li{dotless}mi{dotless}na etkisi]

OBJECTIVES To determine the accuracy of computed tomography (CT)/ magnetic resonance imaging (MRI) image registration performed using tomography system and software present in our department and discover the magnitude of error during the process. METHODS First, calibration data of the CT was reviewed. Following image registration, done using four anatomic landmarks, deliniation of eyeballs and target volume took place. RESULTS The registration score was 9.51±0.11 out of 10 and mean distance was 1.92±0.51 mm. Center coordinates of the eyeballs, contoured using MRI and CT images were compared. Maximum difference was 2.25 mm for the right eye and 2.11 mm for the left eye. Volumes of tumor contours produced from registered images were bigger (75.37 cmsup3/sup vs. 44.81 cmsup3/sup). But in the treatment plans without image registration, the tumor volume received 95-107% of presicribed dose. CONCLUSION Image registration process found to be applicable and repro-ducable for our clinic. It has seen that image registration improves target volume delineation. © 2011 Association of Oncology

Repositining of prostate cancer patients, using implanted gold seeds into prostate and electronic portal imaging device [Prostat bezine implant edilmiş alti{dotless}n çekirdekleri ve elektronik portal görüntüleme cihazi{dotless} kullanarak prostat kanseri hastalari{dotless}ni{dotless}n yeniden pozisyonlandi{dotless}ri{dotless}lmasi{dotless}]

OBJECTIVES To investigate the feasibility of target focused treatment and it's advantages on standard treatment position verifying tecniques using gold markers and electronic portal imaging device (EPID). METHODS Marker placed 10 patient's films were taken, transferred to planning system and distance between markers was measured. Port images were taken by EPID and Template Matching option was used for matching ports with digitally reconstructed radiograph. The distance between markers and the changes were determined with analytic process. Systematical and random set-up errors were determined. RESULTS No important changes on marker positions and no radiation toxicity was observed. Verifying the treatment positions according to markers in terms of position correction gain was better compared to verifying according to bone anatomy (p<0.05). Target focused position verifying was the best way for reducing both systematical and random set-up errors. CONCLUSION The decrease in standard deviation of systematical and random errors provides statistically meaningful decrease in minimum PTV margins. © 2013 Association of Oncology

The measurement of entrance and exit doses with in-vivo dosimetry in head and neck cancers and comparison with treatment planning doses [Baş-boyun kanserlerinde giriş ve çi{dotless}ki{dotless}ş dozlar{dotless}ni{dotless}n in vivo dozimetri kullani{dotless}larak ölçülmesi ve tedavi planlama dozlari{dotless}yla karşi{dotless}laşti{dotless}ri{dotless}lmasi{dotless}]

OBJECTIVES We aimed to measure entrance-exit doses using in-vivo dosimetry for head and neck cancer patients and to compare with planning system doses, to facilitate determination of treatment accuracy. METHODS Three diodes were calibrated using water equivalent phantom. Correction factors had been previously assessed for in-vivo diodes and applied to the readings. Dose measurements were performed on 30 treatment setups for 3 patients treated with isocentric, asymmetric left-right two lateral and supraclavicular fields using 6MV. Measured doses were compared with expected doses. RESULTS The results indicated a small acceptable deviation from expected doses. It was found that the mean deviations for entrance and exit doses were 2.3% and 1.9%, respectively. The deviation in the delivered dose is well within the 5% International Commission on Radiation Units and Measurements (ICRU) recommendation, and thus treatment doses are determined to be in accordance with the planning system doses. CONCLUSION It has been shown that in-vivo dosimetry performed using diodes is a reliable and high-precision method for patient dose control. © 2012 Association of Oncology

Comparison of three dimensional conformal radiotherapy and intensity modulated radiotherapy techniques for the treatment of glioblastoma multiform [Glioblastoma multiform tedavisinde üç boyutlu konformal radyoterapi ile yogunluk ayarli radyoterapi tekniklerinin karsilastirilmasi]

Objective: The aim of this study was to compare Three Dimensional Conformal Radiotherapy (3D-CRT) as the standard technique in Glioblastoma Multiform (GBM) treatment with Intensity Modulated Radiotherapy (IMRT) Techniques in terms of target coverage and dose to critical organs. Material and Methods: 3D-CRT treatment plans of 14 GBM patients were replanned using the IMRT technique and same tumor and critical organ volumes. Three fields in the 3D-CRT technique and 5 fields in the IMRT technique were used. Dose limits were determined as 54Gy for the brain stem, optic chiasm, and optic nerves and 2.5Gy for the lens. The prescribed dose was 50Gy for the planned target volume [PTV](50Gy), 10Gy for the PTV(60Gy), with a total cumulative dose of 60Gy for the (PTV 60Gy) both at 2,0Gy daily fractions. Dosimetric measurements were made for quality assurance for IMRT plans. Results: In IMRT and 3D-CRT plans, maximum (Dmax) and mean (Dmean) median doses were respectively 51.7Gy and 59.0Gy, and 13.8Gy and 15.3Gy for the brain stem; 43.4Gy and 53.2Gy, and 20.5Gy and 44.4Gy for the optic chiasm; 19.3Gy and 27.2Gy, and 2.9Gy and 9.7Gy for the right optic nerve; 10.7Gy and 25.6Gy, and 3.4Gy and 4.5Gy for the left optic nerve; 1.5Gy and 1.8Gy, and 1.4Gy and 1.7Gy for the right lens; 1.4Gy and 1.7Gy, and 1.4Gy and 1.5Gy for the left lens. Furthermore, the median dose respectively was 27.4Gy and 20.0Gy for IMRT plans and 32.3Gy and 25.0Gy for 3D-CRT for Brain-Gross Target Volume (GTV) and Brain-PTV. The difference between the doses for critical organs excluding the right and left lenses and the normal brain tissue outside the tumor was significant. For PTV(50Gy) and PTV(60Gy), inhomogeneity coefficient (IC) was 0.39 and 0.09 in IMRT, 0.31 and 0.11 in 3D-CRT, respectively and the conformity index (CI) was 0.99 and 1.00 in IMRT and 1.00 in 3D-CRT, respectively for all PTVs. Conclusion: This study suggested that there was no significant difference between 3D-CRT and IMRT for PTV(60Gy) in terms of IC and IMRT had less homogenity compared to 3-D-CRT and the IMRT plans were better for both PTVs in terms of CI and spared critical organs and normal brain tissue. © 2013 by Türkiye Klinikleri

Determination of the effect of immobilization systems used in radiotherapy on dose distribution and comparison of these measurements with treatment planning algorithm calculations [Radyoterapide kullanilan immobilizasyon sistemlerinin doz dagilimina etkisinin belirlenmesi ve tedavi planlama algoritma hesaplari{dotless}ni{dotless}n ölçümlerle karşi{dotless}laşti{dotless}ri{dotless}lmasi{dotless}]

OBJECTIVES We aimed to investigate plexiglass breast board (BB) and vacuum bed (VB) effects on dose distribution and reliability of treatment planning system (TPS) calculations. Measurements were performed by placing BBs and VBs of varying thicknesses and air gaps onto water and solid phantoms. CT scans of the solid phantom mechanism were transferred to TPS for dose calculation. 2.6%, 3.9% and 5.5% dose decreases were observed for 10, 15 and 20 mm plexiglass at 5 cm depth. Maximum dose decrease was 1.5% for VB. TPS calculations were within 1% for both systems. Skin dose increased in accordance with thickness. A maximum 6.3% difference was found between calculation and measurements for increasing air gaps, but the differences were not statistically significant. BB must be positioned so as to avoid beam entry. Otherwise, it must be included into the CT scan for better calculation. If using VBs, it must be considered that skin doses increase with thickness. © 2012 Association of Oncology