This paper presents a method for horizontally extending the field-of-view in cone-beam tomography to overcome the limitations of traditional detector sizes. The acquisition algorithms are implemented on an Exciscope Polaris phase-contrast micro-CT instrument, which ensures sufficient motion accuracy for horizontal extension solely reliant on stage positions, even at submicron voxel sizes. This innovation enables the construction of an automated data pipeline that bypasses the need for user input or image registration to recombine frames. Utilizing cloud computing for reconstruction, we efficiently handle large data sizes and computational demands. We demonstrate the method both with a reconstruction diameter of 12,500 voxels and with submicron voxel sizes, showcasing significant improvements in imaging capabilities.
The application of 3D X-ray imaging for biological samples (e.g. biopsies) to gain a deeper understanding of microscopic structures on a (sub)cellular level is restricted by the weak attenuation contrast of soft tissue. The development of novel staining tools for X-ray soft-tissue imaging will overcome these challenges. Here, we present the application of a recently developed method combining a laboratory-based nanoscopic X-ray CT setup enabling resolutions down to 100 nm with a target-specific X-ray staining protocol. The results clearly show that the X-ray attenuation contrast in the samples is remarkably improved by our staining method and detailed tissue (sub)structures are apparent, which cannot be visualized without the staining. The nanoscopic CT data reproduce the tissue morphology with a similar level of detail as the corresponding histological light microscopy images in 2D and enable pathological characterization of the crucial structures. Beyond that, the applied method allows for visualization of the 3D tissue architecture, offering deeper insights into the 3D microscopic structure of soft-tissue. Moreover, we demonstrate the compatibility of the X-ray stain with standard histological staining methods. Beside medical research, the methodology has the potential to contribute to advances in zoology and developmental biology.
In clinical X-ray imaging, the quantitative information in a CT scan has recently been extended by the possibility of using dual-energy information. Dual-energy CT has found its way into clinical imaging during the last few years and has been proven to add additional diagnostic information in different pathologies. It is based on a dual measurement at different photon energies, such that the energy dependence of the linear attenuation coefficient can be used for improved material discrimination. Here, we demonstrate how the dual information accessed with grating-based phase-contrast CT can be used to provide the same quantitative information. Different from dual energy, the phase-contrast measurement directly yields the electron-density and the total attenuation coefficient in a single measurement. With algebraic basis transformation this can be used for quantitative material decomposition, allowing the visualization of quantitative material maps. Further, a simple interaction parametrization has been used for the generation of effective atomic number maps and virtual monochromatic images. The approach has been demonstrated with an experimental angiography simulation with a chicken heart. The results have been compared with iodine staining, which is a current approach for ex-vivo soft-tissue contrast enhancement. The measurements have been performed at a compact laser-undulator synchrotron X-ray source with a tunable quasi-monochromatic X-ray energy. The simultaneous image acquisition guarantees an inherent registration of the two original data-sets. In total, the method provides a range of novel quantitative image representations which can be helpful for specific material discrimination tasks in medical imaging in the future.
Due to the recent development of transmission X-ray tubes with very small focal spot sizes, laboratory-based CT imaging with sub-micron resolutions is nowadays possible. We recently developed a novel X-ray nanoCT setup featuring a prototype nanofocus X-ray source and a single-photon counting detector. The system is based on mere geometrical magnification and can reach resolutions of 200 nm. To demonstrate the potential of the nanoCT system for biomedical applications we show high resolution nanoCT data of a small piece of human tooth comprising coronal dentin. The reconstructed CT data clearly visualize the dentin tubules within the tooth piece.
Compared to conventional computed tomography (CT), dual energy CT allows for improved material decomposition by conducting measurements at two distinct energy spectra. Since radiation exposure is a major concern in clinical CT, there is a need for tools to reduce the noise level in images while preserving diagnostic information. One way to achieve this goal is the application of image-based denoising algorithms after an analytical reconstruction has been performed. We have developed a modified dictionary denoising algorithm for dual energy CT aimed at exploiting the high spatial correlation between between images obtained from different energy spectra. Both the low-and high energy image are partitioned into small patches which are subsequently normalized. Combined patches with improved signal-to-noise ratio are formed by a weighted addition of corresponding normalized patches from both images. Assuming that corresponding low-and high energy image patches are related by a linear transformation, the signal in both patches is added coherently while noise is neglected. Conventional dictionary denoising is then performed on the combined patches. Compared to conventional dictionary denoising and bilateral filtering, our algorithm achieved superior performance in terms of qualitative and quantitative image quality measures. We demonstrate, in simulation studies, that this approach can produce 2d-histograms of the high- and low-energy reconstruction which are characterized by significantly improved material features and separation. Moreover, in comparison to other approaches that attempt denoising without simultaneously using both energy signals, superior similarity to the ground truth can be found with our proposed algorithm.
Scanning times have always been an important issue in x-ray micro-tomography. To reach high-quality reconstructions the exposure times for each projection can be very long due to small detector pixel sizes and limited flux of x-ray sources. In addition, the required number of projections is a factor which limits a reduction of exposure beyond a certain level. This applies particularly to grating-based phase-contrast computed tomography (PCCT), as several images per projection have to be acquired in order to obtain absorption, phase and dark-field information. In this work we qualitatively compare statistical iterative reconstruction (SIR) and filtered back-projection (FBP) reconstruction from undersampled projection data based on a formalin-fixated mouse sample measured in a grating-based phase-contrast small-animal scanner. The results from our assessment illustrate that SIR offers not only significantly higher image quality, but also enables high-resolution imaging from severely undersampled data in comparison to the FBP algorithm. Therefore, the application of advanced iterative reconstruction methods in micro-tomography entails major advantages over state-of-the-art FBP reconstruction while offering the opportunity to shorten scan durations via a reduction of exposure time per projection and number of angular views.
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.