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Iranian Journal of Medical Physics، جلد ۱۵، شماره Special Issue-۱۲th. Iranian Congress of Medical Physics، صفحات ۲۲۳-۲۲۳
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عنوان انگلیسی Evaluation of the gray level in CBCT systems and its relationship with HU in CT Scanners
چکیده انگلیسی مقاله Introduction: Cone-beam CT (CBCT) is an imaging system which offers three-dimensional (3D), multiplanar images and has many advantages over computed tomography (CT) including shorter acquisition times for the resolution desired in dentistry, lower radiation dose to the patient, reasonable price and higher spatial resolution but CBCT scanners are unable to display actual Hounsfield units (HU) similar to medical CT. In CT scan, to show the image that represents the density of the tissue Hounsfield Unit is proportional to the degree of x-ray attenuation and it is allocated to each pixel. In CBCT systems displayed gray levels are arbitrary and so variable, so the derived density provided less than meaningful data and the ability to assess the density or quality of bone is limited. The purpose of the present study was to present a clinical study demonstrating a method to derive Hounsfield units from gray levels in cone beam CT (CBCT). Materials and Methods: For the evaluation of CBCT gray values, a new versatile quality control tool of dental Cone- Beam CT, Pro-Dent CT mk II phantom, which consists of a main PMMA cylinder that houses modules with different test objects was used. Four CBCT devices were used for the scanning of the phantom: CS8100, CS9300(Carestream Health, New York, NY), New Tom GIANO (Quantitative Radiology, Verona, Italy), Vatech Pax-i3D (Hwaseong-si, Gyeonggi-do, Korea). The reconstructed data were exported as Digital Imaging and Communications in Medicine (DICOM) and analyzed with On Demand 3DH by Cybermed, Seoul, Korea and ImageJ as an image processing toolkit. The relationship between gray levels and linear attenuation coefficients in various kV and mA was investigated. Results: The results indicated a strong linear relationship between the gray scales in CBCT and HU in CT using the standard definition HU = (µmaterial   –  µwater)/(µwater) × 1000.  This made it possible to calculate Hounsfield units from the measured gray levels. Uncertainty in determining effective energies for each of CBCT systems resulted in unrealistic effective energies and significant variability of calculated CT numbers. Linear regression (0.802
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نویسندگان مقاله | Ahdiyeh Aghaz
Nuclear Science and Technology Research Institute, Tehran, Iran, mkardan@aeoi.org.ir.


| Mohammad Reza Kardan
Nuclear Science and Technology Research Institute, Tehran, Iran,


| Mohammad Reza Deevband
Department of Medical Physics, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran.


| Bahador Bahadorzadeh
Nuclear Engineering Department, Shiraz University, Shiraz, Iran. Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran, Iran.


| Yaser Kasesaz
Nuclear Science and Technology Research Institute, Tehran, Iran,


| Hossein Ghadiri
Department of Medical Physics and Biomedical Engineering, Tehran University of Medical Sciences, Tehran, Iran.
نشانی اینترنتی http://ijmp.mums.ac.ir/article_12847.html
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