Iranian Journal of Medical Physics
Volume:12 Issue: 1, Winter 2015

Bacterial meningitis is a known infectious disease which occurs at early ages and should be promptly diagnosed and treated. Bacterial and aseptic meningitis are hard to be distinguished. Therefore, physicians should be highly informed and experienced in this area. The main aim of this study was to suggest a system for distinguishing between bacterial and aseptic meningitis, using fuzzy logic. In the first step, proper attributes were selected using Weka 3.6.7 software. Six attributes were selected using Attribute Evaluator, InfoGainAttributeEval, and Ranker search method items. Then, a fuzzy inference engine was designed using MATLAB software, based on Mamdani’s fuzzy logic method with max-min composition, prod-probor, and centroid defuzzification. The rule base consisted of eight rules, based on the experience of three specialists and information extracted from textbooks. Data were extracted from 106 records of patients with meningitis (42 cases with bacterial meningitis) in order to evaluate the proposed system. The system accuracy, specificity, and sensitivity were 89%, 92 %, and 97%, respectively. The area under the ROC curve was 0.93, and Kappa test revealed a good level of agreement (k=0.84, P<0.0005). According to the results, the suggested fuzzy system showed a good agreement and high efficiency in terms of distinguishing between bacterial and aseptic meningitis. To avoid unnecessary antibiotic treatments, patient hospitalization, and misdiagnosis of bacterial meningitis, such systems are useful and highly recommended. However, no system has been yet introduced with 100% correct output and further research is required to improve the results.

Range and diffusion of positron-emitting radiopharmaceuticals are important parameters for image resolution in positron emission tomography (PET). In this study, GEANT4 toolkit was applied to study positron diffusion in soft tissues with and without a magnetic field for six commonly used isotopes in PET imaging including 11C, 13N, 15O, 18F, 68Ga, and 82Rb. GEANT4 toolkit was used to simulate the transport and interactions of positrons. Calculations were performed for the soft tissue phantom (8 mm ×8 mm × 8 mm). Positrons were emitted isotropically from the center of the phantom. By the application of a magnetic field perpendicular to the path of positrons, lateral scattering of positrons could be prevented due to Lorentz force. When the positron energy was below the cut-off threshold (0.001 MeV), the simulation was terminated. The findings showed that the presence of a magnetic field increased the rate of positron annihilation. At magnetic field strengths of 3, 7, and 10 Tesla, 18F with the lowest decay energy showed improvements in the ratio of full width at half maximum (FWHM) resolution to the peak of curve by 3.64%, 3.89%, and 5.96%, respectively. In addition, at magnetic field strengths of 3, 7 and 10 Tesla, 82Rb with the highest decay energy showed improvements in resolution by 33%, 85%, and 99%, respectively. Application of a magnetic field perpendicular to the positron diffusion plane prevented the scattering of positrons, and consequently, improved the intrinsic spatial resolution of PET imaging, caused by positron range effects.

DNA damage is among the main consequences of radiation. Of many different classes of DNA damage, double-strand breaks are the most deleterious. Development of a sensitive biodosimetry method, which utilizes a detection material with a similar construction to the body, seems essential for monitoring radiation workers. In this study, histone H2AX protein was examined as a potential biodosimeter in radiation workers. Moreover, the presence of this protein after in vitro irradiation of blood samples was assessed simultaneously. Blood samples from 46 radiation workers were analyzed in Golestan province, Iran. Meanwhile, two groups of blood samples (five blood samples in each group) were irradiated in vitro by doses of 1 to 0.2 Gy and 0.09 to 0.01 Gy from a 60Co source, respectively. gH2AX level in lymphocytes was measured, using Western blot technique. ANOVA and Tukey’s tests were performed, using SPSS version 16. The significance level was considered to be 0.05. The results of Western blotting for the identification of gH2AX protein in radiation workers were negative. However, gH2AX level in lymphocytes of two in vitro irradiated groups showed a significant correlation with the radiation dose (P<0.0001). The results showed that gH2AX was a good indicator for acute or local exposure to ionizing radiation, while in chronically exposed individuals, including radiation workers, this protein was useless at least in autoradiography detection method. Regarding the presence of gH2AX protein in blood samples, which were irradiated in vitro at low doses, it can be concluded that this protein has powerful repair mechanisms.

Introduction Breast cancer is one of the most life-threatening conditions among women. Early detection of this disease is the only way to reduce the associated mortality rate. Mammography is a standard method for the early detection of breast cancer. Today, considering the importance of breast cancer detection, computer-aided detection techniques have been employed to increase the quality of mammographic images and help physicians reduce false positive rate (FPR). Materials and Methods In this study, a method was proposed for improving the quality of mammographic images to help radiologists establish a prompt and accurate diagnosis. The proposed approach included three major parts including pre-processing, feature extraction, and classification. In the pre-processing stage, the region of interest was determined and the image quality was improved by non-subsampled contourlet transform and super-resolution algorithm. In the feature extraction stage, some features of image components were extracted and skewness of each feature was calculated. Finally, a support vector machine was utilized to classify the features and determine the probability of benignity or malignancy of the disease. Results Based on the obtained results using Mammographic Image Analysis Society (MIAS) database, the mean accuracy was estimated at 87.26% and maximum accuracy was 96.29%. Also, the mean and minimum FPRs were estimated at 9.55% and 2.87%, respectively. Conclusion The results obtained using MIAS database indicated the superiority of the proposed method to other techniques. The reduced FPR in the proposed method was a significant finding in the present article.

Introduction In this study, effective dose equivalent for the public due to internal exposure to 222radon (222Rn) was evaluated in three regions of Ramsar, a northern coastal city in Iran. Materials and Methods Measurements were carried out using a radon monitoring device. Outdoor and indoor radon concentrations were measured within 24 hours with an integration interval of 3 hours. Regions were selected with respect to our previous study on areas of Ramsar with high levels of environmental background radiation. Results This study showed that indoor 222Rn concentration reached to 465 Bq/m3 in one of the selected regions (Talesh Mahalleh) in early morning (5-8 a.m.). Our study also showed that the average effective dose equivalents (due to both indoor and outdoor exposures) in the selected regions (Talesh Mahalleh, Sadat Mahalleh, and Chaparsar) were 9.5±2.8, 5.1±2.1, and 3.2±1.2 mSv/y, respectively. Conclusion It is clear that the annual effective dose from internal exposure to 222Rn in areas of Ramsar with high levels of natural radiation was significantly higher than the maximum annual effective dose permissible for public.

Introduction The purpose of this study was to evaluate personal shields in radiation departments of hospitals affiliated to Mashhad University of Medical Sciences. Materials and Methods First, the information related to 109 personal shields was recorded and evaluated by imaging equipment. Afterwards, the equivalent lead thickness (ELT) of 62 personal shields was assessed, using dosimeter and standard lead layers at 100 kVp. Results In this study, 109 personal shields were assessed in terms of tears, holes and cracks. The results showed that 18 shields were damaged. Moreover, ELT was evaluated in 62 shields. As the results indicated, ELT was unacceptable in 8 personal shields and lower than expected in 9 shields. Conclusion According to the results, 16.5% of personal shields had defects (tears, holes and cracks) and 13% of them were unacceptable in terms of ELT and needed to be replaced. Therefore, regular quality control of personal shields and evaluation of new shields are necessary at any radiation department.

Introduction Application of near-infrared absorbing nanostructures can induce hyperthermia, in addition to providing more efficient photothermal effects. Gold-gold sulfide (GGS) is considered as one of these nanostructures. This study was performed on a tissue-equivalent optical-thermal phantom to determine the temperature profile in the presence and absence of GGS and millisecond pulses of a near-infrared laser. Moreover, the feasibility of hyperthermia induction was investigated in a simulated tumor. Materials and Methods A tumor with its surrounding tissues was simulated in a phantom made of Agarose and Intralipid. The tumor was irradiated by 30 laser pulses with durations of 30, 100, and 400 ms and fluences of 40 and 60 J/cm2. Temperature variations in the phantom with and without GGS were recorded, using fast-response sensors of a digital thermometer, placed at different distances from the central axis at three depths. The temperature rise was recorded by varying duration and fluence of the laser pulses. Results The rise in temperature was recorded by increasing laser fluence and number of pulses for three durations. The temperature profile was obtained at each depth. The presence of GGS resulted in a significant increase in temperature in all cases (P<0.035). Also, the laser temperature had a slower reduction in the presence of GGS, compared to its absence after turning the laser off (P<0.001). Conclusion The millisecond laser pulses could induce hyperthermia in a relatively large target tissue volume. GGS as a simple and cost-effective synthesized nanostructure could induce localized hyperthermia in the desired region during near-infrared laser irradiation.

Introduction Intensity-Modulated Radiotherapy (IMRT) is becoming an increasingly routine treatment method. IMRT can be delivered by use of conventional Multileaf Collimators (MLCs) and/or physical compensators. One of the most important factors in selecting an appropriate IMRT technique is integral dose. Integral dose is equal to the mean energy deposited in the total irradiated volume of the patient. The aim of the present study was to calculate and compare the integral dose in normal and target organs in two different procedures of IMRT: Step-and-Shoot (SAS) and compensator-based IMRT. Materials and Methods In this comparative study, five patients with prostate cancer were selected. Module Integrated Radiotherapy System was applied, using three energy ranges. In both treatment planning methods, the integral dose dramatically decreased by increasing energy. Results Comparison of two treatment methods showed that on average, the integral dose of body in SAS radiation therapy was about 1.62% lower than that reported in compensator-based IMRT. In planning target volume, rectum, bladder, and left and right femoral heads, the integral doses for SAS method were 1.01%, 1.02%, 1.11%, 1.47%, and 1.40% lower than compensator-based IMRT, respectively. Conclusion Considering the treatment conditions, the definition of dose volume constraints for healthy tissues, and the equal volume of organs in both treatment methods, SAS radiation therapy by providing a lower integral dose seems to be more advantageous and efficient for prostate cancer treatment, compared to compensator-based IMRT.