Estimation of geometrical parameters for fan beam tomography

Gullberg, Grant T.; Tsui, B.M.W.; Crawford, Carl R.; Edgerton, E. R.

doi:10.1088/0031-9155/32/12/005

Cited by 75 publications

(50 citation statements)

References 14 publications

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“…where l e is the effective hole length of the collimator and m is the linear attenuation coefficient of the septal material (lead) at 140 keV (26,27,1). The effective geometric spatial resolution (R c ) is described as the FWHM of the intensity distribution obtained from a point source placed at a distance from the collimator face (2), given by: 3 where a is hole size, b is distance between the crystal and the collimator, and z is distance between the source and the collimator surface. Also, total resolution can be defined as:…”

Section: Monte Carlo Simulationsmentioning

confidence: 99%

See 1 more Smart Citation

Estimation of Fan Beam and Parallel Beam Parameters in a Wire Mesh Design

Khorshidi¹,

Ashoor²,

Hosseini³

et al. 2012

Journal of Nuclear Medicine Technology

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Special collimators used in imaging systems play an important part in obtaining qualified images to improve diagnosis in medicine. Methods: The primary aim of this study was to compare resolution between fan beam and parallel beam collimators using Monte Carlo simulation in the shape of cubic holes. Also, parameters such as geometric efficiency, geometric resolution, scatter, penetration, and full width at half maximum were studied to compare their special characteristics. Results: The simulation results demonstrated that the geometry efficiency of a fan beam collimator increased as the angle of the slant hole increased, and the geometric resolution decreased as the angle of the slant hole increased, at a distinct distance from a monoenergetic source of g-rays. In contrast, at a distinct angle, geometric resolution increased as the distance between the source and the collimator surface increased. For both collimators, scatter and penetration decreased as the distance increased. These results were in agreement with ADAC company data. Finally, fan beam collimators were found to have better resolution than parallel beam collimators with a cubic hole shape in a wire mesh design. Conclusion: Estimation of the fan beam by parallel beam parameters as cubic holes can be suitable in collimator design to improve resolution and efficiency. Col limation of low-energy photons, allowing detection of only those photons propagating in the appropriate direction, plays a key role in obtaining a suitable map in SPECT imaging. Some collimators, such as the parallel beam and fan beam types, are widely used in different applications and for organs centered within the field of view. Therefore, it is important to study collimator geometric properties to improve diagnosis in medicine. Fan beam collimators are a special type of converging collimator with the holes focusing toward a focal line parallel to the axis of rotation of the camera (1).For optimization of collimator design, photon interactions in g-camera collimators have been simulated by the Monte Carlo N-particle code (MCNP5) (2-4). In this code, source geometry, collimators, and detectors need to be defined in the input file-a cumbersome process (5,6). Recently, researchers have clinically compared parallel beam and fan beam collimators and simulated the parallel beam collimator by this code (7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22). In this study, fan beam parameters were deliberated by this code.To improve resolution and efficiency, it is helpful to model collimators of various hole shapes, edge effects, septal materials, and geometric configurations. The aim of this study was to investigate resolution between fan beam and parallel beam collimators using MCNP5 simulation in the shape of cubic holes. Also, distinctive parameters such as geometric efficiency, scatter, penetration, and full width at half maximum (FWHM) have been compared, with assessment of the fan beam and parallel beam collimator responses. MATERIALS AND METHODS Computation of Cubic Hole A...

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Section: Monte Carlo Simulationsmentioning

confidence: 99%

“…For optimization of collimator design, photon interactions in g-camera collimators have been simulated by the Monte Carlo N-particle code (MCNP5) (2)(3)(4). In this code, source geometry, collimators, and detectors need to be defined in the input file-a cumbersome process (5,6).…”

mentioning

confidence: 99%

Estimation of Fan Beam and Parallel Beam Parameters in a Wire Mesh Design

Khorshidi¹,

Ashoor²,

Hosseini³

et al. 2012

Journal of Nuclear Medicine Technology

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“…These geometric parameters are needed in the CT reconstruction [1,2] , and the precision of these parameters is so important that a little error of these parameters will result in geometric artifact and blur the reconstructed image [3,4] .…”

Section: Introductionmentioning

confidence: 99%

“…Many methods have been proposed for CT geometric calibration [1,2,[5][6][7][8][9][10][11] , most of these methods require special manufactured calibration phantom for calculating the geometric parameters [5][6][7][8][9] . Noo et al [5] proposed an analytic method based on identification of ellipse parameters, they use the ellipse parameters as intermediate parameters to calculate the CT geometric parameters.…”

Section: Introductionmentioning

confidence: 99%

A wire scanning based method for geometric calibration of high resolution CT system

Jiang

et al. 2015

SPIE Proceedings

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This paper is about geometric calibration of the high resolution CT (Computed Tomography) system. Geometric calibration refers to the estimation of a set of parameters that describe the geometry of the CT system. Such parameters are so important that a little error of them will degrade the reconstruction images seriously, so more accurate geometric parameters are needed in the higher-resolution CT systems. But conventional calibration methods are not accurate enough for the current high resolution CT system whose resolution can reach sub-micrometer or even tens of nanometers. In this paper, we propose a new calibration method which has higher accuracy and it is based on the optimization theory. The superiority of this method is that we build a new cost function which sets up a relationship between the geometrical parameters and the binary reconstruction image of a thin wire. When the geometrical parameters are accurate, the cost function reaches its maximum value. In the experiment, we scanned a thin wire as the calibration data and a thin bamboo stick as the validation data to verify the correctness of the proposed method. Comparing with the image reconstructed with the geometric parameters calculated by using the conventional calibration method, the image reconstructed with the parameters calculated by our method has less geometric artifacts, so it can verify that our method can get more accurate geometric calibration parameters. Although we calculated only one geometric parameter in this paper, the geometric artifacts are still eliminated significantly. And this method can be easily generalized to all the geometrical parameters calibration in fan-beam or cone-beam CT systems.

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“…Because tomography is a polar data acquisition technique, it requires a precise rotating system where the center of rotation (COR) must be known with high accuracy. To avoid COR error [12], geometrical calibration [13][14][15][16] and post-processing algorithms [17,18] are used to realign the projections and reconstruct the error-free images. However, when the voxel size decreases-for example in case of μCT and TDM-the accuracy of the rotation and alignments became more important.…”

Section: Introductionmentioning

confidence: 99%

Correction of error motion in a line-scanning tomographic optical microscope

Dudás

Gajdátsy²,

Sinkó

et al. 2012

Appl. Opt.

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A line-scanning tomographic optical microscope system requires precise rotation of the scanning line. Center of rotation error introduced by both the imprecision of optical and mechanical components is studied experimentally and via simulations. It was shown that a practical tolerance limit can be chosen where the influence of the investigated error on the reconstructed image quality remains insignificant. An effective and simply practical solution was presented to keep the center of rotation error below this tolerance limit and the spatial resolution of the reconstructed image close to the diffraction limit.

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Estimation of geometrical parameters for fan beam tomography

Cited by 75 publications

References 14 publications

Estimation of Fan Beam and Parallel Beam Parameters in a Wire Mesh Design

Estimation of Fan Beam and Parallel Beam Parameters in a Wire Mesh Design

A wire scanning based method for geometric calibration of high resolution CT system

Correction of error motion in a line-scanning tomographic optical microscope

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