فهرست مطالب

  • Volume:16 Issue: 3, 2019
  • تاریخ انتشار: 1398/02/11
  • تعداد عناوین: 9
|
  • Fariba Farhadi Birgani, Mohammad Javad Tahmasebi Birgani, Roghayeh Kamran Samani, Fatemeh Maghsoodinia * Pages 189-194
    Introduction
    Nowadays, magnetic resonance imaging (MRI) in combination with computed-tomography (CT) is increasingly being used in radiation therapy planning. MR and CT images are applied to determine the target volume and calculate dose distribution, respectively. Since the use of these two imaging modalities causes registration uncertainty and increases department workload and costs, in this study, brain synthetic CT (sCT) and synthetic MR (sMR: sT1w/sT2w) images were generated using Atlas-based method; consequently, just one type of image (CT or MR) is taken from the patient.
    Material and Methods
    The dataset included MR and CT paired images from 10 brain radiotherapy (RT) patients. To generate sCT/sMR images, first each MR/CT Atlas was registered to the MR/CT target image, the resulting transformation was applied to the corresponding CT/MR Atlas, which created the set of deformed images. Then, the deformed images were fused to generate a single sCT/sMR image, and finally, the sCT/sMR images were compared to the real CT/MR images using the mean absolute error (MAE).
    Results
    The results showed that the MAE of sMR (sT1w/sT2w) was less than that of sCT images. Moreover, sCT images based on T1w were in better agreement with real CT than sCT-based T2w. In addition, sT1w images represented a lower MAE relative to sT2w.
    Conclusion
    The CT target image was more successful in transferring the geometry of the brain tissues to the synthetic image than MR target.
    Keywords: Computed Tomography Magnetic Resonance Imaging, Radiotherapy
  • Dongjun Jang, Sungchul Kim * Pages 195-199
    Introduction
    The Republic of Korea has developed a national standard based on which diagnostic X-ray equipment must be tested every 3 years. Accordingly, the performance of X-ray equipment used in all hospitals is evaluated by national certification bodies in compliance with the safety management regulations for X-ray equipment. However, if the equipment is non-compliant, its use must be stopped until it satisfies the accepted standards.
    Material and Methods
    In compliance with the safety management regulations for diagnostic X-ray equipment, hospitals in this study were divided into two groups, namely the general hospital group and the clinic group with diagnostic X-ray equipment. The samples in this study were composed of 11 and 18 machines selected randomly from general hospitals and clinics, respectively, which satisfied the acceptance standards since last year in both groups. The evaluation of diagnostic X-ray machines was based on the results obtained from X-ray tube voltage, tube current, exposure time accuracy, and the X-ray dose reproducibility.
    Results
    The X-ray machines of the general hospital group followed all national standards. However, those of the clinic group failed to satisfy the requirements of tube voltage, tube current, exposure time accuracy, and X-ray dose reproducibility.
    Conclusion
    Clinics require their own quality control to reduce unnecessary medical radiation exposure due to the poor X-ray equipment performance. Moreover, it is suggested that the test period of the safety management regulations on diagnostic X-ray equipment need to be shorter than three years.
    Keywords: Diagnostic Equipment Quality Control Reproducibility, safety management
  • Mohammed El Adnani Krabch *, Abdelouahed Chetaine, Kamal Saidi, Fatima Zohra ERRADI, Abdelati NOURREDDINE, Yassine Benkhouya, Redouane El Baydaoui Pages 200-209
    Introduction
    This study aimed to report the measurement of photon and electron beams to configure the Analytical Anisotropic Algorithm and Electron Monte Carlo used in clinical treatment.
    Material and Methods
    All measurements were performed in a large water phantom using a 3-dimensional scanning system (PTW, Germany). For photon beams, the data were measured with a 0.125cc cylindrical chamber. For electron, the data were performed with a Roos chamber.
    Results
    In photon beams, flatness and symmetry for reference field size 10×10cm2 were within the tolerance intervals. Flatness were 0.79% and 1.55% for X6MV and X18MV, respectively. Symmetry were 0.57 and 0.25 for X6MV and X18MV, respectively. The output factor vary between 0.83 and 1.11 for X6MV. Moreover, it varies between 0.74 and 1.09 for X18MV. The leaf transmission factors were 0.97% for X6MV and1.14% for X18MV. The DLG were 1.31 and 1.34 for X6MV and X18MV, respectively. For electron beams, the quality index R50 for applicator 15×15cm2 were in the tolerance. Maximum depth dose for 6, 9, 12, 16 and 20MeV were 1.2, 1.9, 2.7, 2.99 and 2.4cm, respectively. Bremsstrahlung tail were 6MeV–2.86cm, 9MeV–4.32cm, 12MeV–5.96cm, 16MeV–7.93cm, and 20MeV–10.08cm per energy levels.
    Conclusion
    The obtained results and international recommendations were in a good agrement
    Keywords: Linear accelerator Algorithm, Monte Carlo Method Radiotherapy
  • Monire Mohebian, Reza Pourimani * Pages 210-216
    ntroduction: The purpose of this study was to measure the radioactivity in the agricultural soil of south-east of Shazand Refinery Complex to determine both reliable baseline data on the radiation level and the radiation dose exposure to the farmers and inhabitants of the studied area.
    Material and Methods
    This study was conducted on 21 soil samples collected from two different lands. Sampling spots in each land were selected for the assessment of specific activities of radionuclides of 226Ra, 232Th, 40K, and137Cs by using high purity germanium detector setup. Standards of International Atomic Energy Agency references material gamma ray uranium, reference gamma-ray thorium, and reference gamma-ray potassium were used for quality control and determining efficiency calibration. All samples were examined for radium equivalent, absorbed gamma dose rate, internal hazard index, external radiation hazard, annual gonadal dose equivalent, indoor and outdoor annual effective dose equivalent, and excess lifetime cancer risk. 
    Results
    The specific activities of radionuclides 226Ra, 232Th, 40K, and 137Cs varied from13.12 to 33.03, 11.3 to 35.86, 257.82 to 605.5, and 1.28 to 13.36 Bq/kg, respectively. Moreover, the results of this study were compared with those reported from other countries and worldwide average.
    Conclusion
    Although all samples were polluted by the 137Cs fission product, the measured values were within the global reported safety limits. Therefore, there is no risk for farmers and inhabitants in this region.
    Keywords: Natural radioactivity, Radionuclides Dosage Radiation Health Risk
  • Abdelati NOURREDDINE *, El Amin MARNOUCHE, Mohammed El Adnani KRABCH, Rajaa CHERKAOUI EL MOURSLI, Noureddine BENJAAFAR Pages 217-223
    Introduction
    The commonly used technique of radiation therapy for vulvar cancer consists of anteroposterior (AP) and posteroanterior (PA) fields. This is the first study that reports the dosimetric comparison between the AP-PA techniques and the new 3D advanced conformal technique (3D-ACT) based on the multiplicity of treatment fields in patients with squamous cell cancer of the vulva in the postoperative setting.
    Material and Methods
    This comparative planning study was conducted on15 patients with vulvar carcinoma treated with adjuvant radiation therapy at the National Institute of Oncology in Rabat, Morocco. Three treatment plans were performed, corresponding to three techniques, namely photons with source-skin distance inguinal supplement, modified segmental boost technique and 3D advanced conformal technique. For each plan, the dose-volume histogram was used to generate planning target volumes (total and inguinal PTV) and organs at risk (bladder, rectum, bowel and femoral heads) parameters.
    Results
    The 95% isodose volume was significantly reduced with the advanced conformal technique (P<0.0001) without compromising the total PTV coverage (P= 0.94). This technique resulted in the best conformity and homogeneity index. The 3D-ACT decreased significantly the PTVs Dmax and Dmean (P<0.0001), and offered better homogeneity for inguinal PTV (i.e., 1.07±0.01, P<0.0001).The 3D-ACT decreased the rectum absorbed dose, V40 (volume receiving ≥40Gy), V45, and Dmaxto50.21±27.21, 22.81±10.22, and 46.56±1.11, respectively. With regard to femoral heads, the 3D-ACT decreased the Dmax and V45 in comparison to the other two techniques.
    Conclusion
    The 3D-ACT seems to be an alternative to the AP-PA irradiation techniques in postoperative setting when IMRT is unavailable.
    Keywords: Vulvar cancer, Dosimetric comparison, 3-D Conformal Radiotherapy, Planning Techniques
  • Payam Samadi Miandoab *, Ahmad Esmaili Torshabi, Sohelia Parandeh Pages 224-231
    Introduction
    A new method based on image registration technique and an intelligent correlation model to calculate. The present study aimed to propose inter- and intra-fraction motion errors in order to address the limitations of conventional Patient positioning methods.
    Material and Methods
    The configuration of the markerless method was accomplished by using four-dimensional computed tomography (4DCT) datasets. Firstly, the MeVisLab software package was used to extract a three-dimensional (3D) surface model of the patient and determine the tumor location. Then, the patient-specific 3D surface model which also included the breathing phases was imported into the MATLAB software package in order to define several control points on the thorax region as virtual external markers. Finally, based on the correlation of breathing signals/patient position with breathing signals/tumor coordinate, an adaptive neuro fuzzy inference system was proposed to both verify and align the inter- and intra-fraction motion errors in radiotherapy, if needed. In order to validate the proposed method, the 4DCT data acquired from four real patients was considered.
    Results
    Final results revealed that our hybrid configuration method was capable of aligning patient setup with lower uncertainties, compared to other available methods. In addition, the 3D root-mean-square error has been reduced from 5.26 to 1.5 mm for all patients.
    Conclusion
    In this study, a markerless method based on the image registration technique in combination with a correlation model was proposed to address the limitations of the available methods, including dependence on operator’s attention, use of passive markers, and rigid-only constraint for patient setup.
    Keywords: Image Processing, Image Guided Radiation Therapy (IGRT), patient positioning
  • Sareh Tajiki, Hassan Nedaie *, Mahbod Esfehani, Ghazale Geraily, Mohsen Hassani, Ali Rastjoo Ardakani, Ehsan Mohammadi, Mansur Naderi Pages 232-240
    Introduction
    Penumbra is an important property of the radiation beam to obtain a suitable margin surrounding the target volume. Therefore, the precise penumbra width determination in stereotactic radiotherapy is necessary for treatment planning. This study aimed to compare the obtained results of penumbra width by in-house and standard circular cones by different dosimeters, as well as evaluating the function of EBT3 for dosimetric properties of the small field radiation.
    Material and Methods
    Different circular cones were mounted on the head of the accelerator to produce 12, 20, and 40 mm field sizes at isocenter. Dosimetric measurements were performed with the EBT3 film, PinPoint ion chamber. Afterwards, MCNPX Monte Carlo simulation was used to evaluate the dosimetric parameters.
    Results
    According to the obtained results, the penumbra width was increased by larger diameters of circular cones. The obtained measured data by PinPoint ion chamber showed a larger penumbra width compared to those calculated by Monte Carlo at all field sizes. The gamma index analysis revealed  distance-to-agreement and dose-difference of 2 mm /2%/ at all points. The results of this study showed that source to diaphragm distance had a major role in penumbra size determination of small field dosimetry with PinPoint ion chamber, EBT3 film, and Monte Carlo simulation.
    Conclusion
    As findings of this study reported, EBT3 films are reliable detectors for relative dosimetry due to high spatial resolution for small field sizes. Furthermore, they can be used for measuring beam profile and percentage depth dose curves.
    Keywords: Monte Carlo Method, small field, penumbra, Gafchromic Film Stereotactic Radiotherapy
  • Jue Zhang, Li Chen * Pages 241-249
    Introduction
    Breast cancer is the second cause of mortality among women. Early detection is the only rescue to reduce the risk of breast cancer mortality. Traditional methods cannot effectively diagnose tumor since they are based on the assumption of well-balanced dataset.. However, a hybrid method can help to alleviate the two-class imbalance problem existing in the diagnosis of breast cancer and establish a more accurate diagnosis.
    Material and Methods
    The proposed hybrid approach was based on improved Laplacian score (LS) andK-nearest neighbor (KNN) algorithms called LS-KNN. An improved LS algorithm was used for obtaining the optimal feature subset. The KNN with automatic K was utilized for classifying the data which guaranteed the effectiveness of the proposed method by reducing the computational effort and making the classification more faster. The effectiveness of LS-KNN was also examined on two biased-representative breast cancer datasets using classification accuracy, sensitivity, specificity, G-mean, and Matthews correlation coefficient.
    Results
    Applying the proposed algorithm on two breast cancer datasets indicated that the efficiency of the new method was higher than the previously introduced methods. The obtained values of accuracy, sensitivity, specificity, G-mean, and Matthews correlation coefficient were 99.27%, 99.12%, 99.51%, 99.42%, respectively.
    Conclusion
    Experimental results showed that the proposed approach worked well with breast cancer datasets and could be a good alternative to the well-known machine learning methods
    Keywords: Breast Cancer, classification, imbalance, Computer aided diagnosis
  • Mohammad Mehdi Movahedi, Ali Tavakoli Golpayegani *, Arash Safari, Samad Amani Pages 250-254
    Introduction
    There have been many studies conducted on the effects of mobile phones radiations on people’s health due to increasing number of mobile phones users. The present study aimed to investigate the effects of electromagnetic waves generated from 3G and 4G mobile phone radiations on student’s reaction time and short-term memory.
    Material and Methods
    This was a cross-sectional and descriptive-analytic study. A sample of 85 medical students from Shiraz University of Medical Sciences in the age range of 18-22 years was selected. After 10-min exposure to 3G and 4G mobile waves without any prognoses if mobile phone was on or off, response time and short-term memory tests were taken at once. The groups then left laboratory for about 2 h to take a rest, and they came back to laboratory to carry out the second mode of testing after two h (mobile phones on or off related to previous test). Both tests were performed in the afternoon to make students almost identical in terms of daily fatigue conditions. The data were analyzed in SPSS software (version 19) using t-test technique. The difference was statistically considered significant (P<0.05).
    Results
    The results revealed that the reaction time and average short-term memory following the exposure to electromagnetic waves emitted from mobile 3G and 4G mobile phones increased and decreased, respectively. However, this difference was only significant in the reaction time. The electromagnetic waves generated by the 3G and 4G mobile phones led to slower response time among students under emission, compared to the control group.
    Conclusion
    According to our findings, it can be concluded that the frequency of electromagnetic waves increased the response to stimulus time.
    Keywords: Electromagnetic Fields, Mobile Phone Data, Radiofrequency, Short-Term Memory Reaction Tim