Background: The purpose of this study was to investigate the dosimetric characteristics of a new type of two-dimensional diode detector array used for quality assurance of stereotactic radiosurgery (SRS). Materials and Methods: The devices used in this study were the SRS MapCHECK detector and the StereoPHAN. The detector has 1013 diode detectors over an area of 77 x 77 mm2. The reproducibility, dose linearity, dose rate dependencies, output factors (OPFs) and angular dependencies were investigated as dosimetric characteristics. The OPFs were measured and compared between AP and PA direction ranging from 0. 5 x 0. 5 to 7 x 7 cm2. The angular dependencies were measured using 19 gantry angles. Results: The dose reproducibility and linearities showed sufficient performance of 6 MV and 10 MV. At 40 MU/min, there was a 1. 3% difference from the ionization chamber measurements. For the flattening filter-free beam, there was no dose rate dependency from the 400 MU/minute to 2400 MU/minute, and the variation was within 0. 5%. For small irradiation fields of 1 cm or less, the measured value of the SMC differed in AP and PA directions by up to 4. 5%. The maximum gantry angle dependency of the detector was 5. 3%. A maximum difference of-3. 1% occurred between the measurements and TPS calculations. Conclusion: Results indicate that the new 2D diode detector is stable and useful for QA and end-to-end testing of SRS due to its excellent dose characteristics, high resolution and ease of handling when combined with the StereoPHAN.

In this paper, a new algorithm for edge detection based on fuzzy concept is suggested. The proposed approach defines dynamic membership functions for different groups of pixels in a 3 by 3 neighborhood of the central pixel. Then, fuzzy distance and -cut theory are applied to detect the edge map by following a simple heuristic thresholding rule to produce a thin edge image. A large number of experiments are employed to con firm the robustness of the proposed algorithm. In the experiments different cases such as normal images, images corrupted by Gaussian noise, and uneven lightening images are involved. The results obtained are compared with some famous algorithms such as Canny and Sobel operators, a competitive fuzzy edge detector, and a statistical based edge detector. The visual and quantitative comparisons show the effectiveness of the proposed algorithm even for those images that were corrupted by strong noise.

Background: X-ray computed tomography (CT) examinations deliver a significant amount of radiation doses to patients comparing to conventional radiography examinations. The objective of the current study was to analyze and investigate the average patient received dose from axial and spiral CT exams in a medical imaging center.Material and Methods: In this study, the patient imaging technique, weight and height were recorded. The patients’ doses provided by CT unit in terms of CTDIw were also recorded. Then, other dosimetric quantities including dose-length product (DLP) and effective dose were calculated for each patient using the recorded data. The average values were obtained for all the studied dosimetric quantities. Also, their distribution in terms of examined regions and imaging mode; ie, axial and spiral CT were analyzed by SPSS software.Results: For all patients, the mean effective dose of 4.4 mGy with the standard deviation of 9.2 was found. The CTDIw for axial group was two times higher than spiral ones. Conversely, the effective dose of axial group was less than spiral group. Additionally, the effective doses of 2.3 and 5.2 mSv were found for axial and spiral, receptively. For both quantities of CTDIw and effective dose, the observed difference between axial and spiral modes were significant (P<0.001).Conclusion: Our results showed that although the patient doses in the current study was comparable with the reported values by similar studies in other countries, it was higher than the reported values of a similar study in Iran. Exposure technique’s optimaization and further review in routine CT examinations were recommended.

The effect of earthquake rotational component (torsional and rocking ones) on the structures, has attracted the attention of many researchers in recent years. The impact of the rocking and torsional components of the ground motion, particularly on high-rise and height-wise irregular structures, is significant. In this paper, the rotational components of earthquake record were computed employing the acceleration gradient method, using the data obtained from a dense accelerometer array, and the behavior of the cooling towers under the influence of these rotational components was investigated. To this end, three distinct loading combinations were applied to the tower, and the results were examined and compared. The loading combinations include 1) three translational components of earthquake record, 2) applying rotational and translational components of the earthquake simultaneously, and 3) applying translational and rocking components concurrently. The response of the tower under the two latter loading combinations was compared with that of the first one. The results indicate that in the case of simultaneous action of translational and rocking components, displacements and support reactions, on average, increase by 5% in comparison with the case of applying solely translational component. Furthermore, including the torsional component, in addition to the rocking one, leads to a rise of nearly 6% in the displacements and supports reaction in comparison with the first loading combination results.

The main purpose of this article is to evaluate and to compare the performance metrics, array factor (AF), signal to interference plus noise ratio (SINR), mean square error (MSE), bit error rate (BER), and also computational complexity of different modified blind adaptive beamforming algorithms based on constrained constant modulus (CCM).Two modified algorithms use adaptive step size mechanisms in the stochastic gradient (SG) algorithm for adjusting the step size. The third one, CCM-RLS, uses recursive least squares (RLS) optimization algorithm which is replaced by the inverse correlation matrix instead of the step size. In the case of a uniform linear array (ULA) and 5 users, one as desired signal and the others as interference signals, simulation results show that the modified algorithms, CCMRLS, CCM-SG-time averaging adaptive step size (TAASS) and CCM-SG-modified adaptive step size (MASS), offer higher performance with respect to conventional CCM-SG, respectively. Comparing the performance of CCM-RLS and adaptive step size versions of CCM-SG show that CCM-RLS converges faster and it can cancel the interferences close to the desired signal, more effectively. Moreover, the resulting SINR level is higher and BER is less than the other methods.However, CCM-SG-MASS and CCM-SG-TAASS have less computational complexity, additions and multiplications.

Cognitive radios utilize spectrum sensors to provide information about the surrounding radio environment. This enables cognitive radios to communicate at the same frequency bands with existing (primary) radio systems, and thereby improve the utilization of spectral resources. Furthermore, the spectrum sensor must be able to guarantee that the cognitive radio devices do not interfere with the primary system transmissions. This paper describes a hardware implementation of a spectrum sensor based on cyclostationary feature detector, which has an improved detection performance achieved by decimation of the cyclic spectrum. Decimation also provides a simple way to control detection time and, therefore, allows trading the detection time to better probability of detection and vice versa.Implementation complexity in terms of power consumption and silicon area for a 65 nm CMOS process is evaluated.Measured detection performance is presented and detection of a 802.11g WLAN signal through air interface is demonstrated.