Our study investigated the impact of irregular respiration on correlation between surrogate respiratory signal and internal organ motion in 4DCT. Based on the proposed quantitative index of respiratory irregularity, the study cases were divided into two: the case with regular breathing and the case with irregular breathing. By groups, internal organ movements were measured from 4CT images, and correlation between external surrogate signal and internal organ motion was analyzed. The results showed that the correlation with internal organ motion was obviously deteriorated in the case with irregular breathing, rather than the case with regular breathing. As observed that the irregular respiration may lead to such errors on gating interval up to 20% either phase or amplitude level, it would be necessary to employ the respiratory guidance and feedback system that can minimize the respiratory irregularity.
As the conventional method of geometric calibration not only needs extra-scan but also have the vulnerability to the dimensional accuracy of the dedicated phantom, we proposed a new geometric calibration scheme based on data redundancy which uses projection data of any arbitrary patient already scanned, mainly focused on a geometry of Varian’s OBI system. Using the fan-beam based data redundancy which can be applied to cone-beam projection data of either full-fan or half-fan geometry, one could successfully detect the misalignments of geometric parameters and find the values of them. The simulation studies using the XCAT numerical phantom were conducted to check the feasibility of data-redundancy-based method can detect the misalignment of geometric parameters and find true values.
We present a methodology for the optimization of sampling schemes in diffuse optical tomography (DOT). The proposed method exploits singular value decomposition (SVD) of the sensitivity matrix, or weight matrix, in DOT. Two mathematical metrics are introduced to assess and determine the optimum source–detector measurement configuration in terms of data correlation and image space resolution. The key idea of the work is to weight each data measurement, or rows in the sensitivity matrix, and similarly to weight each unknown image basis, or columns in the sensitivity matrix, according to their contribution to the rank of the sensitivity matrix, respectively. The proposed metrics offer a perspective on the data sampling and provide an efficient way of optimizing the sampling schemes in DOT. We evaluated various acquisition geometries often used in DOT by use of the proposed metrics. By iteratively selecting an optimal sparse set of data measurements, we showed that one can design a DOT scanning protocol that provides essentially the same image quality at a much reduced sampling.
KEYWORDS: Deconvolution, Data acquisition, Computer simulations, X-ray imaging, Scattering, Data corrections, Head, Image quality, Convolution, Medical imaging, Fluctuations and noise
Our earlier work has demonstrated that the data consistency condition can be used as a criterion for scatter kernel optimization in deconvolution methods in a full-fan mode cone-beam CT [1]. However, this scheme cannot be directly applied to CBCT system with an offset detector (half-fan mode) because of transverse data truncation in projections. In this study, we proposed a modified scheme of the scatter kernel optimization method that can be used in a half-fan mode cone-beam CT, and have successfully shown its feasibility. Using the first-reconstructed volume image from half-fan projection data, we acquired full-fan projection data by forward projection synthesis. The synthesized full-fan projections were partly used to fill the truncated regions in the half-fan data. By doing so, we were able to utilize the existing data consistency-driven scatter kernel optimization method. The proposed method was validated by a simulation study using the XCAT numerical phantom and also by an experimental study using the ACS head phantom.
This work proposed a motion detection method for cone-beam computed tomography (CBCT) that utilizes a calibration
phantom of known geometry as the motion detector and an established geometric calibration protocol to provide the
motion information. An initial numerical study regarding the consequences of motion and its correction was conducted
with a Shepp-Logan and an XCAT phantom. Motion artifacts were induced by acquiring the projections in a simple
saddle trajectory scan. Since the scanning trajectory is set, the magnitude of motion for each projection view is already
known, the correction of motion can then be efficiently implemented. Motion correction was done prior to the
backprojection process of the filtered backprojection (FBP) image reconstruction algorithm. Results showed that motion
correction improved the image quality of the reconstructed images. For a known or unknown scanning trajectory, the
geometric calibration method can define the geometric information of a scanning system. In the current work,
projections of a calibration phantom of known geometry were acquired from a saddle trajectory scan, and geometric
parameters for selected projection views were successfully computed from the projection matrix provided by the
geometric calibration method. Further studies will involve an experimental investigation wherein a calibration phantom
is attached to a randomly moving object and scanned in a circular trajectory. Utilizing the parameters extracted from the
geometric calibration, an accurate description of the object motion can be used and adapted for motion correction.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.