A cone beam SPECT reconstruction algorithm with a displaced center of rotation

Jian-ying, LI; Jaszczak, R.J.; Wang, Huili; Gullberg, Grant T.; Greer, K.L.; Coleman, R. Edward

doi:10.1118/1.597253

Cited by 19 publications

(17 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Inaccurate knowledge of the position of the principal ray can lead to artifacts in reconstructed images. [9][10][11] Principal ray mispositioning from the ideal situation indicated above is not uncommon and has been observed in these previous studies.…”

Section: Introductionsupporting

confidence: 57%

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

et al. 1998

Self Cite

View full text Add to dashboard Cite

A filtered backprojection algorithm is developed for single photon emission computed tomography (SPECT) imaging with an astigmatic collimator having a displaced center of rotation. The astigmatic collimator has two perpendicular focal lines, one that is parallel to the axis of rotation of the gamma camera and one that is perpendicular to this axis. Using SPECT simulations of projection data from a hot rod phantom and point source arrays, it is found that a lack of incorporation of the mechanical shift in the reconstruction algorithm causes errors and artifacts in reconstructed SPECT images. The collimator and acquisition parameters in the astigmatic reconstruction formula, which include focal lengths, radius of rotation, and mechanical shifts, are often partly unknown and can be determined using the projections of a point source at various projection angles. The accurate determination of these parameters by a least squares fitting technique using projection data from numerically simulated SPECT acquisitions is studied. These studies show that the accuracy of parameter determination is improved as the distance between the point source and the axis of rotation of the gamma camera is increased. The focal length of the focal line perpendicular to the axis of rotation is determined more accurately than the focal length to the focal line parallel to this axis.

show abstract

Section: Introductionsupporting

confidence: 57%

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

et al. 1998

Self Cite

View full text Add to dashboard Cite

show abstract

“…1,7,14 It was reported that 3D images obtained using the cone-beam scanners are inevitably distorted away from the central slice as the single-orbit cone beam geometry does not provide a complete data set. 9,13 These distortions and the associated loss of spatial resolution are particularly evident in samples containing plate-shaped structures, and are minimized by reducing the cone-beam angle. 5,9,13 However, a smaller cone-beam angle has often been found to be associated with lesser number of scanning fields and lower resolution.…”

Section: Introductionmentioning

confidence: 99%

“…9,13 These distortions and the associated loss of spatial resolution are particularly evident in samples containing plate-shaped structures, and are minimized by reducing the cone-beam angle. 5,9,13 However, a smaller cone-beam angle has often been found to be associated with lesser number of scanning fields and lower resolution. This was attributed to the limitation of the distances between the object, X-ray tube, and detectors.…”

Section: Introductionmentioning

confidence: 99%

“…As compared to the conventional technique of histomorphometry, this technique allows rapid, noninvasive, and detailed assessment of the bone microstructure and enables reliable prediction of the mechanical performance of the bone. 2,4 Cone-beam mode lCT is commonly used for the imaging of small animals; 13 this technique enables rapid characterization of the 3D properties of structures and a more efficient use of X-ray fluorescence. 1,7,14 It was reported that 3D images obtained using the cone-beam scanners are inevitably distorted away from the central slice as the single-orbit cone beam geometry does not provide a complete data set.…”

Section: Introductionmentioning

confidence: 99%

“…Thus, the cone-beam angle has always been set as a constant value by manufacturers, with the reasonable range being recommended as within 10°. 5,9,13 Another important method of correcting distortions is to obtain the exact reconstruction after scanning. Several approximate reconstruction methods have been proposed previously.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The Influence of Center of Rotation on the Assessment of Trabecular Bone Densitometric and Structural Properties

Sheng

Dai

et al. 2008

Ann Biomed Eng

View full text Add to dashboard Cite

The center of rotation is a physical location in the microCT scanner, defined by the axis of rotation of the sample stage. This physical location is always well defined during calibration of the instrument and fitted by an appropriate algorithm. However, in real images of limited contrast and with X-ray photon noise, this algorithm exhibits poorer precision and the optimum center of rotation cannot be always acquired. Thus, adjustment by operator is necessary to determine whether the center of rotation was correct, in order that the structural information of the sample can be correctly interpreted. In this paper, the effect of center of rotation on the assessment of densitometric and structural properties of trabecular bone was firstly evaluated. Twenty female Sprague-Dawley rats of 7-month-old were randomly assigned to ovariectomized (OVX) and SHAM-operated (SHAM) groups. The left tibiae were harvested at 3 weeks postoperatively. High resolution microCT was used to identify the densitometric and microstructural properties of trabeculae in the proximal ends of tibia. After CT scanning, the best artificial center of rotation for each scan was obtained. Bone parameters analyses were performed on the centers at different places away from the best artificial center of +/-0.2, +/-0.5, +/-1.0, +/-1.5, and +/-2.0 pixels, respectively. The general linear model (GLM) repeated measures procedure was used to investigate the difference in the parameters between the two groups (OVX vs. SHAM) and the possible effects of center displacements. A significant difference between OVX and SHAM groups was found in all parameters (p < 0.05) except Tb.Th, DA, and BS/BV. TBMD, DA, BS/BV, and Conn.D were decreased while BV/TV and Tb.Th were increased with the center deflection. Variations of these parameters were acceptable when the displacements were limited within +/-1.5 pixels for tBMD, BV/TV, DA, and Conn.D, and +/-1.0 pixels for Tb.Th and BS/BV. These changes were similar in both OVX and SHAM groups. The changing curves of bone parameters vs. centers could be well fitted by quadric regression models, by which the real center could be acquired, and thus the precision of microCT analysis would be improved. There were some inevitable differences between the best artificial and real centers.

show abstract

Line‐based iterative geometric calibration method for a tomosynthesis system

Choi,

Vent,

Acciavatti

et al. 2024

Medical Physics

View full text Add to dashboard Cite

BackgroundA next generation tomosynthesis (NGT) system, capable of two‐dimensional source motion, detector motion in the perpendicular direction, and magnification tomosynthesis, was constructed to investigate different acquisition geometries. Existing position‐based geometric calibration methods proved ineffective when applied to the NGT geometries.PurposeA line‐based iterative calibration method is developed to perform accurate geometric calibration for the NGT system.MethodsThe proposed method calculates the system geometry through virtual line segments created by pairs of fiducials within a calibration phantom, by minimizing the error between the line equations computed from the true and estimated fiducial projection pairs. It further attempts to correct the 3D fiducial locations based on the initial geometric calibration. The method's performance was assessed via simulation and experimental setups with four distinct NGT geometries: X, T, XZ, and TZ. The X geometry resembles a conventional DBT acquisition along the chest wall. The T geometry forms a “T”‐shaped source path in mediolateral (ML) and posteroanterior (PA) directions. A descending detector motion is added to both X and T geometries to form the XZ and TZ geometries, respectively. Simulation studies were conducted to assess the robustness of the method to geometric perturbations and inaccuracies in fiducial locations. Experimental studies were performed to assess the impact of phantom magnification and the performance of the proposed method for various geometries, compared to the traditional position‐based method. Star patterns were evaluated for both qualitative and quantitative analyses; the Fourier spectral distortions (FSDs) graphs and the contrast transfer function (CTF) were extracted. The limit of spatial resolution (LSR) was measured at 5% modulation of the CTF.ResultsThe proposed method presented is highly robust to geometric perturbation and fiducial inaccuracies. After the line‐based iterative method, the mean distance between the true and estimated fiducial projections was [X, T, XZ, TZ]: [0.01, 0.01, 0.02, 0.01] mm. The impact of phantom magnification was observed; a contact‐mode acquisition of a calibration phantom successfully provided an accurate geometry for 1.85× magnification images of a star pattern, with the X geometry. The FSD graphs for the contact‐mode T geometry acquisition presented evidence of super‐resolution, with the LSR of [0°‐quadrant: 8.57, 90°‐quadrant: 8.47] lp/mm. Finally, a contact‐mode XZ geometry acquisition and a 1.50× magnification TZ geometry acquisition were reconstructed with three calibration methods—position‐based, line‐based, and iterative line‐based. As more advanced methods are applied, the CTF becomes more isotropic, the FSD graphs demonstrate less spectral leakage as super‐resolution is achieved, and the degree of blurring artifacts reduces significantly.ConclusionsThis study introduces a robust calibration method tailored to the unique requirements of advanced tomosynthesis systems. By employing virtual line segments and iterative techniques, we ensure accurate geometric calibration while mitigating the limitations posed by the complex acquisition geometries of the NGT system. Our method's ability to handle various NGT configurations and its tolerance to fiducial misalignment make it a superior choice compared to traditional calibration techniques.

show abstract

A cone beam SPECT reconstruction algorithm with a displaced center of rotation

Cited by 19 publications

References 0 publications

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

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

The Influence of Center of Rotation on the Assessment of Trabecular Bone Densitometric and Structural Properties

Line‐based iterative geometric calibration method for a tomosynthesis system

Contact Info

Product

Resources

About