The 6MV photon beam production by the Elekta Line accelerateur of Tripoli of medical center (TMC) was modeled using Beamnrc and Dosexyzne Monte Carlo codes. The Beamnrc code was used to model the accelerator head and generate phase files. The phase space files were then used as input to the Dosexyzne code to simulate octogenarian deth dose and beam profiles. simulation were first stared using nominal provided by the vendor, a field size of 10x10cm2 and Source to surface distance (SSD) of 100 cm. simulation were compared with experimental data and energy tuning procedures were applied to validate the model. Energy tuning procedures indicated that the nominal energy of 6 MV and a FWHM of the Gaussian distribution of the source of 0.35 cm were the optimal energy and FWHM for the model. The depth of maximum dose at 6 MV was found to be 1.5 cm. The percentage relative differences between calculated and experimental Pdd(s) ranged from 0.5% to 3% for field size of 10cm2 and reached a value of 8% at depths greater than 20cm, The model was later used to calculate PDD(s) and beam profile and output factors for different field size ranging from 3x3cm2 to 25x25cm2. Calculated output factors were in good agreement with experimental values (the percentage relative differences ranged from 1% to 4%). (Author) arabic 42 English 152
Karima Elmasri, Tawfik Giaddui(12-2012)

Cardiovascular disease (CVD) is a major cause of mortality and the main cause of morbidity worldwide. CVD may lead to heart attacks and strokes and most of these are caused by atherosclerosis; this is a medical condition in which the arteries become narrowed and hardened due to an excessive build-up of plaque on the inner artery wall. Arterial calcification and, in particular, abdominal aortic calcification (AAC) is a manifestation of atherosclerosis and a prognostic indicator of CVD. In this paper, a two-stage automatic method to detect and quantify the severity of AAC is described; it is based on the analysis of lateral vertebral fracture assessment (VFA) images. These images were obtained on a dual energy x-ray absorptiometry (DXA) scanner used in single energy mode. First, an active appearance model was used to segment the lumbar vertebrae L1-L4 and the aorta on VFA images; the segmentation of the aorta was based on its position with respect to the vertebrae. In the second stage, feature vectors representing calcified regions in the aorta were extracted to quantify the severity of AAC. The presence and severity of AAC was also determined using an established visual scoring system (AC24). The abdominal aorta was divided into four parts immediately anterior to each vertebra, and the severity of calcification in the anterior and posterior walls was graded separately for each part on a 0-3 scale. The results were summed to give a composite severity score ranging from 0 to 24. This severity score was classified as follows: mild AAC (score 0-4), moderate AAC (score 5-12) and severe AAC (score 12-24). Two classification algorithms (k-nearest neighbour and support vector machine) were trained and tested to assign the automatically extracted feature vectors into the three classes. There was good agreement between the automatic and visual AC24 methods and the accuracy of the automated technique relative to visual classification indicated that it is capable of identifying and quantifying AAC over a range of severity. arabic 30 English 163
Karima Mohamed Ali Elmasri, William Evans, Yulia Hicks(1-2016)

There are three main aims that make this study particularly important and interesting to radiometric studies. Firstly, it will provides information on the concentration composition of natural and the associated man-made radioactivity of imported dental porcelain materials to be used by most dental laboratories in Great Jamahiriya. Since these materials do not pass radiation inspection tests before their entry or use and there is a large variety of supply source of these dental materials to be used for all dental works on Libyan patients, anomalies can be identified easily. Secondly, the analysis of selective elemental abundance (U, Th, and K ) and dose rate calculations may be used to calculate effective dose rates to dental laboratory technicians and also to the patient who will be using these specific materials. This research project will provide the first results of such measurements and the corresponding average annual effective dose rates equivalent to the patients using these materials and also to the dental technician and doctors work in the various dental laboratories that make use of these materials in their daily work. A total number of 30 dental powder samples were collected from a number of dental laboratories around Tripoli area will be analyzed. In this research project, the results from this preliminary survey regarding Th, U and K elemental concentrations in a wide variety of dental materials by means of high-resolution X-ray spectrometry will be presented. Further results from these investigations concerning activity concentrations and the associated dose rates, effective dose and the committed dose due to the use of these materials are going to be calculated and compared with other published data elsewhereandrecommendationoftheirusewillbederivedaccordingly. arabic 10 English 74
Karima Mohamed Ali Elmasri, Nouri A. Droughi(9-2010)

Dual-energy x-ray absorptiometry (DXA) is an established modality for the assessment of bone mineral density. DXA has also been used for the detection of abdominal aortic calcification (AAC) using lateral images taken for vertebral fracture assessment (VFA). In this phantom study, the capability of VFA for the detection of AAC was investigated. A Perspex phantom of variable width in the range 15-30 cm was used to simulate abdominal soft tissue. Aluminium strips of thickness 0.05-2.0 mm were sandwiched between two halves of the phantom to mimic aortic calcification. VFA images of the phantom were acquired in single-energy mode and analysed by placing regions of interest over the aluminium strip and an adjacent area of Perspex. For each phantom width, the minimum detectable aluminium thickness was assessed visually and related to contrast-to-noise ratio (CNR). Linearity of pixel value with aluminium thickness was tested by linear regression and correlation. Repeatability was measured with five repeated scans for selected phantom configurations. The minimum thickness of aluminium that could be visualised increased with phantom width and varied from 0.05 mm at 15 cm Perspex to 0.5 mm at 30 cm Perspex; the CNR threshold was about 0.03. At all phantom widths, the variation of pixel value with aluminium thickness was strongly linear (r²>0.98, p
Karima Elmasri, William David Evans, Yulia Hicks(6-2017)