الفهرس 
IntroductionOnly 14 pages are availabe for public view
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Abstract
The practice of medicine involves the science, dealing with the prevention,diagnosis, alleviation, and treatment of disease. The variety and complexity of human conditions make it impossible to reach the most appropriate diagnosis all the time or to predict certain particular response to treatment.Computed tomography (CT) has been widely applied as a vital non-invasive diagnostic tool in the medical field. CT has also been proven to be accurate in demonstrating anatomy and pathology due to its precise spatial resolution. CT is utilized extensively in imaging of the head. CT is sufficient and diagnostic in many clinical circumstances such as acute trauma, non-traumatic intracranial hemorrhage; also CT is useful screening tool for indications such as mental status changes, acute neurologic deficit, and acute headache. CT is very useful screening modality for the presence of neoplasm and mass effect to which the addition of intravenous contrast may provide added sensitivity in selected circumstances. The challenges in optimization of dose and image quality are compounded by the lack of a commercially available vendor automated mechanisms which collecting and modifying wide system protocols. The manual labor involved in identifying, recording, and compiling for review and subsequent implementation all relevant parameters of active protocols is not inconsequential. The clinical community needs effective protocol management tools and efficient methods to replicate protocols across different scanners in order to ensure consistency. The ability to quickly view and understand the myriad of CT protocol parameters contained within a single exam type is critical to the success of protocol review process.CT scanning, image quality has many components and is depend on many Parameters such as CT number, noise, slice thickness (Z-axis resolution), low contrast resolution, uniformity and high contrast resolution. Our work aimed to measure and to evaluate the quality parameters of computed tomography image at precise slice thickness. This study examined the image quality tests by using two different quality assurance phantoms to ensure the image quality status besides examining the capability of phantoms to perform these tests. In this study the advanced quality assurance checks were tested and measured by using the manufacture manual protocol of checking the 64 x 0.625 was used. This precise measurement of small slice width provide us to evaluate the consistency of image. According to manufacture recommendation another phantom should be used for achieving more precise measurements; So Multi detector Computed tomography (CT) scanner Brilliance64, Philips was evaluated by two phantoms (Philips manufacture phantom, American College of Radiology (ACR) phantom. The scanner was tested in the same day. The same protocol parameters of Philips phantom were used on both phantoms. The obtained Computed tomography (CT) images for each test were analyzed and the image quality variations were measured. The results were determined by comparing it with the tolerance values of each phantom. Digital Imaging and Communications in Medicine (DICOM) viewer program software was used for analyzing our data because it has well-developed image quality checks and tolerances for standard CT systems .DICOM also is relatively simple to set up. CT accreditation phantom (ACR) of model (Gammex-464) was chosen due to its high radiation safety levels. The International Atomic Energy Agency (IAEA) recommends an acceptance tests and periodically quality assurance tests of CT-scanners with respect to radiation dose and image quality. When Results have been obtained and compared with tolerance values it showed that: positioning, alignment, slice thickness, high contrast resolution, and uniformity tests were accepted values and within tolerance levels in both phantoms. While noise, test was out of the tolerance values in both phantoms. There was a good capability of recognizing artifacts in both phantoms and there were two types of errors recorded: A ring artifact and a strike artifact. Ring artifacts are very common artifacts generated by detectors. CT number test results were accepted in ACR phantom but in Philips phantom there was two materials out of tolerance values. During our study; we noticed that ACR phantom is much easier than manufacture water phantom in positioning test so it took less effort and less time. Finally it was concluded that; 1. The use of two different types of phantoms has confirmed the status of the image quality. 2. The presence of a qualified medical physicist (QMP) is essential for all the Egyptian radiology departments to improve the image quality especially in cases of advanced tests with precise images thickness and to monitor the radiation dose. 3. The American College of Radiology (ACR) phantom is a suitable choice to evaluate advanced quality assurance tests specially those advanced tests of precise slice thickness. 4. The quality assurance phantoms importance for medical imaging field was improved.