Astigmatic single photon emission computed tomography imaging with a displaced center of rotation

Wang, Huili; Smith, Mark F.; Stone, C.D.; Jaszczak, R.J.

doi:10.1118/1.598325

Cited by 27 publications

(30 citation statements)

References 14 publications

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“…If and follow Gaussian distributions about and , respectively, with standard deviations given by and , respectively, then (13) may be interpreted as a likelihood. This function is similar to the cost functions in [5], [9], [10] since the probability distribution is modeled as Gaussian. Estimates of the uncertainties of the fitted parameters are determined from the fit under the assumption that (13) is a valid likelihood function.…”

Section: A Fitting Of Shiftsmentioning

confidence: 97%

Simultaneous multi-head calibration for pinhole SPECT

Metzler

Jaszczak

2006

IEEE Trans. Nucl. Sci.

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Pinhole collimation is used as a magnifying geometry to overcome the resolution constraints of the gamma cameras used in SPECT. It is very sensitive to the mechanical position of the aperture relative to the axis of rotation. It is also sensitive to the axial position of the aperture. When one camera head is used, there is no intrinsic reference point for determining the axial mechanical shift. However, when multiple heads are used, the axial origin can be defined as the center of the first aperture. The other apertures can be measured relative to the first. A procedure has been developed for simultaneously calibrating multiple heads by using a single point source in the field of view of all heads. The gantry is rotated through 360 degrees. The centroids are fit using a maximum-likelihood method to an equation that describes the axial and transaxial geometry. The three coordinates of the point source are determined along with the mechanical and electronic shifts in the axial and transaxial directions; the axial mechanical shift of the first aperture is set to zero by definition. Another advantage of multi-head calibration is that a further constraint on the position of the point source is made. We apply the calibration information to a sub-micro disk phantom with 1.6 mm disks.

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Section: A Fitting Of Shiftsmentioning

confidence: 97%

Simultaneous multi-head calibration for pinhole SPECT

Metzler

Jaszczak

2006

IEEE Trans. Nucl. Sci.

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“…Therefore, in this paper we propose a new high-precision calibration method which is based on optimization theory and uses a thin wire as calibration phantom. In this paper we calculated only S err (see Fig.1), but this parameter has the most influence on reconstruction images [4] , so we can still get much better reconstruction images by calculating this parameter only. In the implementation, we use the method proposed by Noo et al [5] to calculate the rest of the parameters for reconstruction, and assume that they are accurate.…”

Section: Introductionmentioning

confidence: 98%

“…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%

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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“…To achieve optimal performance in resolution and sensitivity on a SPECT system, it is critical that the system's geometrical parameters [2]- [5] used for image generation are accurate. Erroneous values would introduce artifacts and resolution loss [6], [7]. Slit-slat collimator [8]- [10] has the useful features of both pinhole and parallel hole collimators.…”

Section: Introductionmentioning

confidence: 99%

Optimization and Calibration of Slat Position for a SPECT With Slit-Slat Collimator and Pixelated Detector Crystals

Deng

Yao

2011

IEEE Trans. Nucl. Sci.

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To expand the availability of SPECT for biomedical research, we developed a SPECT imaging system on an existing animal PET detector by adding a slit-slat collimator. As the detector crystals are pixelated, the relative slat-to-crystal position (SCP) in the axial direction affects the photon flux distribution onto the crystals. The accurate knowledge of SCP is important to the axial resolution and sensitivity of the system. This work presents a method for optimizing SCP in system design and for determining SCP in system geometrical calibration. The optimization was achieved by finding the SCP that provides higher spatial resolution in terms of average-root-mean-square width of the axial point spread function (PSF) without loss of sensitivity. The calibration was based on the least-square-error method that minimizes the difference between the measured and modeled axial point spread projections. The uniqueness and accuracy of the calibration results were validated through a singular value decomposition (SVD) based approach. Both the optimization and calibration techniques were evaluated with Monte Carlo (MC) simulated data. We showed that the was improved about 15% with the optimal SCP as compared to the least-optimal SCP, and system sensitivity was not affected by SCP. The SCP error achieved by the proposed calibration method was less than 0.04 mm. The calibrated SCP value was used in MC simulation to generate the system matrix which was used for image reconstruction. The images of simulated phantoms showed the expected resolution performance and were artifact free. We conclude that the proposed optimization and calibration method is effective for the slit-slat collimator based SPECT systems.

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Astigmatic single photon emission computed tomography imaging with a displaced center of rotation

Cited by 27 publications

References 14 publications

Simultaneous multi-head calibration for pinhole SPECT

Simultaneous multi-head calibration for pinhole SPECT

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

Optimization and Calibration of Slat Position for a SPECT With Slit-Slat Collimator and Pixelated Detector Crystals

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