Geometric calibration method for multiple-head cone-beam SPECT system

Rizo, P.; Grangeat, Pierre; Guillemaud, R.

doi:10.1109/23.340643

Cited by 68 publications

(33 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A CCURATE calibration has been shown to be important for good reconstructions of cone-beam [1]- [3] and pinhole [4], [5] projection data. Recent work has shown that angular-dependent correction for the radius of rotation (ROR) can make an impact on reconstruction results [6].…”

Section: Introductionmentioning

confidence: 99%

Angular-Dependent Axial-Shift Correction for Pinhole SPECT

Metzler

Jaszczak²,

Greer³

et al. 2007

IEEE Trans. Nucl. Sci.

View full text Add to dashboard Cite

Compensation for pinhole-SPECT calibration parameters has been previously shown to be important for achieving good resolution. It has also been shown that angular-dependent (AD) compensations for the variation of radius of rotation can reduce reconstruction artifacts. In this study, we evaluate the effect of AD compensation of axial mechanical shifts (AMS) on the axial resolution of reconstructions. Measuring the AD AMS was accomplished using point-source scans. The centroids of the scans were fitted to their expected values in the transverse and axial directions. The differences in the axial direction between the data and fit were used to calculate the AD AMS under the assumption that the differences were due only to this shift. The effect on reconstruction was evaluated using a cold-disk phantom with 1.6 mm thick disks. Triple-head acquisitions using circular and helical paths were performed. The data were reconstructed with and without the calculated correction. The results show that the amplitude of the axial shift is approximately 0.5-1.0 mm for our system. The angular dependence of the heads is similar and suggests that the paths of the heads are distorted by gravitational effects. The circular and helical reconstructions show substantial improvement with compensation. In conclusion, AD compensation for AMS has a large impact on reconstruction quality. It is likely that the further development of other AD compensations may also have a large impact on resolution.Index Terms-Instrumentation, pinhole, single photon emission computed tomography, small animal imaging, SPECT.

show abstract

Section: Introductionmentioning

confidence: 99%

Angular-Dependent Axial-Shift Correction for Pinhole SPECT

Metzler

Jaszczak²,

Greer³

et al. 2007

IEEE Trans. Nucl. Sci.

View full text Add to dashboard Cite

show abstract

“…Later, a method 9 suggested that seven parameters are sufficient to calibrate the cone-beam geometry for a circular motion in which the azimuthal angles are known. Those seven parameters were divided to intrinsic and extrinsic parameters.…”

Section: Introductionmentioning

confidence: 99%

“…Alignment calibration methods for cone-beam geometry were developed in Refs. [8][9][10][11]. One method 8 used an alignment point source to estimate three alignment parameters (distance from focus to center of rotation, focal length, and location of projection of center of rotation) plus the three-dimensional coordinate of the alignment point source.…”

Section: Introductionmentioning

confidence: 99%

A line‐source method for aligning on‐board and other pinhole SPECT systems

2013

View full text Add to dashboard Cite

Purpose: In order to achieve functional and molecular imaging as patients are in position for radiation therapy, a robotic multipinhole SPECT system is being developed. Alignment of the SPECT system-to the linear accelerator (LINAC) coordinate frame and to the coordinate frames of other on-board imaging systems such as cone-beam CT (CBCT)-is essential for target localization and image reconstruction. An alignment method that utilizes line sources and one pinhole projection is proposed and investigated to achieve this goal. Potentially, this method could also be applied to the calibration of the other pinhole SPECT systems. Methods: An alignment model consisting of multiple alignment parameters was developed which maps line sources in three-dimensional (3D) space to their two-dimensional (2D) projections on the SPECT detector. In a computer-simulation study, 3D coordinates of line-sources were defined in a reference room coordinate frame, such as the LINAC coordinate frame. Corresponding 2D line-source projections were generated by computer simulation that included SPECT blurring and noise effects. The Radon transform was utilized to detect angles (α) and offsets (ρ) of the line-source projections. Alignment parameters were then estimated by a nonlinear least squares method, based on the α and ρ values and the alignment model. Alignment performance was evaluated as a function of number of line sources, Radon transform accuracy, finite line-source width, intrinsic camera resolution, Poisson noise, and acquisition geometry. Experimental evaluations were performed using a physical linesource phantom and a pinhole-collimated gamma camera attached to a robot. Results: In computer-simulation studies, when there was no error in determining angles (α) and offsets (ρ) of the measured projections, six alignment parameters (three translational and three rotational) were estimated perfectly using three line sources. When angles (α) and offsets (ρ) were provided by the Radon transform, estimation accuracy was reduced. The estimation error was associated with rounding errors of Radon transform, finite line-source width, Poisson noise, number of line sources, intrinsic camera resolution, and detector acquisition geometry. Statistically, the estimation accuracy was significantly improved by using four line sources rather than three and by thinner linesource projections (obtained by better intrinsic detector resolution). With five line sources, median errors were 0.2 mm for the detector translations, 0.7 mm for the detector radius of rotation, and less than 0.5• for detector rotation, tilt, and twist. In experimental evaluations, average errors relative to a different, independent registration technique were about 1.8 mm for detector translations, 1.1 mm for the detector radius of rotation (ROR), 0.5• and 0.4• for detector rotation and tilt, respectively, and 1.2• for detector twist. Conclusions: Alignment parameters can be estimated using one pinhole projection of line sources. Alignment errors are largely associated with limite...

show abstract

“…The calibration process consists of associating multiple known points with their measured image locations to extract the 9 calibration parameters from the matrices in equation (4). (Note that there is a small subtlety in equation (4): the scalar will also vary with each measurement.)…”

Section: A Problem Definitionmentioning

confidence: 99%

“…[1][2][3][4][5][6][7][8][9]). Broadly speaking, the usual approach is to scan an appropriate known calibration object, and use the projection data to deduce the various parameters describing the orientations and locations of the relevant physical components (i.e.…”

Section: Introductionmentioning

confidence: 99%

Analytic Calibration of Cone-Beam Scanners

Strubel

Clackdoyle²,

Mennessier³

et al.

IEEE Nuclear Science Symposium Conference Record, 2005

View full text Add to dashboard Cite

We are investigating a direct analytic method of determining all geometric calibration parameters for a cone-beam scanner. Each projection is independently calibrated using a common calibration object that remains fixed in the laboratory frame. We make no assumptions or restrictions on the path of the cone vertex (e.g. the x-ray source) or the movement of the detector but we do assume a known field-of-view common to all views. The method uses a calibration object consisting of 30 small balls lying on 3 orthogonal concentric circles and one additional ball at the center of the calibration object. From parametrizations of the 3 image ellipses it is possible to analytically obtain expressions for all the calibration parameters. Using simulations we present our first results with this method, and by adding uncertainty to the locations of the projected balls, we determine the stability of the method. Our ultimate goal is to develop a completely automated calibration procedure requiring no user intervention whatsoever, and providing a seamless link to the reconstruction procedure.

show abstract

Geometric calibration method for multiple-head cone-beam SPECT system

Cited by 68 publications

References 9 publications

Angular-Dependent Axial-Shift Correction for Pinhole SPECT

Angular-Dependent Axial-Shift Correction for Pinhole SPECT

A line‐source method for aligning on‐board and other pinhole SPECT systems

Analytic Calibration of Cone-Beam Scanners

Contact Info

Product

Resources

About