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Skip to main content. Log In Sign Up. Development and validation of two phantoms for quality control 1 in cone-beam CT. Barrera Angeles, Analitia et al. Thiyagarajan, S et al.
Alonso, TC et al. A comparison among methodologies. Cervantes-Sanchez, F et al. Melo Bernal, W et al. An analytical approach to cell survival. Ortiz Murillo, JA et al. Use of Monte Carlo simulation software for calculating Effective dose in Gsometria beam computed tomography. Barbalho – Salvador, Bahia, Brasil wilsonottobatista gmail. There are currently projects to standardize the use of CBCT.
This study aimed at the development and validation of the models of phantom: The two phantom used to evaluate seven parameters of quality control are: The spatial resolution is a critical parameter that differs significantly from the other types of scan, and in these two phantom can be evaluated by two different methods: Validation was performed in three models CBCT: All imaging protocols were characterized dosimetrically with solid state sensors to correlate with the perfect operation.
These models were geimetria by different manufacturers have different characteristics as FOV, maximum voltage, slice thickness and patient positioning mode. The two of phantom models were viable and also showed compliance with the specifications and data available in the literature. We conclude the feasibility of the two phantom models, and model option will be linked to the practicality positioning equipment.
Phantoms for quality control; Cone Beam CT.
However, this imaging modality was introduced in dental radiology, unaccompanied tools destined to check service to image quality standards Bamba et al.
The Cone Beam Computed Tomography CBCT is a device that generates tomographic images as consists in using a two-dimensional array of detectors, whereas the fan shaped beam tomography uses a one-dimensional array detectors. Another fundamental characteristic is the isotropy of the volume elements, Voxel. Thus, the images generated in cone beam CT scanners allow geometrically accurate measurements on any plane.
The practice and periodic verification of radiology image quality are essential for the safety of diagnosis.
In this sense, all other modalities in radiology have protocols and tools for the image quality control realization Commission, ; Engen et al. At present scientific publications and technical initiatives have suggested to some phantom models for quality control in cone beam CT Commission, ; Pauwels et al. However, the variety of models and technological concepts between the different manufacturers require the development of a phantom that meets all possibilities including field of view of size, FOV; angle of rotation and FOVs combinations.
An initiative was presented in with a model consisting of objects inserted in a square block, parallelepiped, of PMMA immersed in water Batista et al. This format, parallelepiped does not allow its use in combined FOVs. Similarly tomography beam fan-shaped, MSCT, the minimum parameters necessary for image quality assurance are: Here, it is important to point out that the Hounsfield scale, important scale set to MSCT, is not valid for cone beam tomography.
In addition to CBCT is essential to check the geometric distortion; linear measurements in three dimensions; angular measurements. And replacing the Hounsfield scale, is evaluated, the intensity of the pixel value or as commonly referred to, the average value of the pixel MPV Suomalainen et al.
In this context the main objective of this study is to present two models of phantoms for the quality control assessments in cone beam tomography. These phantoms enable the evaluation of all the parameters mentioned above in any FOV size available.
In the first objects, modules are fixed, stacked and positioned immersed in water. The second model modules are positioned on PMMA and these disks are stacked to form the simulator.
Both modular phantoms to assess the following parameters associated with the evaluation of image quality: The uniformity of the image is calculated according to the following expression, Equation 1.
Low contrast resolution PMMA cylindrical module, Figure 2 c with a face containing grooves with a depth of 2 mm and equal to 5 mm in diameter; 4 mm; 3 mm; 2 mm; 1. These grooves are filled with material with linear attenuation coefficient close to the linear attenuation coefficient of PMMA for the energy range used in cone beam tomography.
Spatial resolution in high contrast: And x is the position in centimeters. MTF is calculated by Fourier transform of g x. Geometric distortion and angular measurements Two modules are available for evaluating geometric distortion in the image, Figure 2 a. These holes are regularly spaced by 10 mm, thereby forming a pattern of holes with separating disk 10 mm across; 2 The same pattern of holes is arranged in one of the resolution module faces in low-contrast view of the CT scanners of small field of view FOVFigure 2 c.
Evaluation of linear measurements in the z axis In the drive for low-contrast resolution evaluation there are two holes of 3. The selected equipment satisfies the features of the phantoms: Table 1 shows the main technical characteristics of the equipment used in the validation process Table 1 – Technical characteristics of the equipment used in the validation process of phantoms.
In Table benjamij is shown the data concerning the evaluation of the intensity value of the pixel or MPV the five different materials. These results reflect average values for the different voxel sizes. Table 2 — Pixel value of intensity or MPV for five different materials. This check has the main purpose to verify compliance on the manufacturer’s specification when exist and establish a baseline.
Figure 4 shows an example of the regions of interest, ROI, used in the measurements. Figure 4 — Selection of ROIs for pixel intensity measurement on different materials.
Spatial resolution in high-contrast and low-contrast resolution The evaluation of spatial resolution with high contrast presented below refers to visual assessment of the bar pattern.
Other analytical options and based on obtaining the MTF are not presented here. And there is no limit specification for detection capability, resolution in low contrast.
Geometría Analítica – Benjamín Garza Olvera – Google Books
Figure 5 shows an image with purpose to illustrate the analiticaa interpretation of bar patterns. Geometric distortion and linear dimensions along the direction z.
All this equipment meets the specifications of the manufacturers and the accuracy of measurements of distances along the z axis and the geometric distortion in the xy plane of olvers image.
The tolerance established by manufacturers and rules of the Uunited Kingdom Public Health England, is 0. Figure 6 a shows in detail the holes with a depth of 4. Table 4 shows the values of evaluation of the image uniformity, the uniformity and non-integral uniformity.
And, in Figure 7 a is an example of the ROIs and Figure 7 b a profile for the evaluation of uniformity and non-integral uniformity. Table 4 — Evaluation of uniform, non-uniform integral and integral uniformity. Figure 7 – Example of evaluation of image uniformity. Development and implementation of a low-cost phantom for quality control in cone beam computed tomography.
palmas estudios mediante: Topics by
Radiation protection dosimetry— The European protocol for the quality control of the physical and technical aspects of mammography screening.
Development and applicability of a quality control phantom for dental cone-beam CT. Dosimetry and image quality of four dental cone beam computed tomography scanners compared with multislice computed tomography scanners. Dentomaxillofacial Radiology 38, — A phantom for simplified image quality control of dental cone beam computed tomography units.
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Las conclusiones a las que llegaron fueron las siguientes: Y por ende no obtener resultados confiables. Study of the Effect of U0.