Dynamic Volume Data Research Articles

On-the-Fly Fast X-Ray Tomography Using a CdTe Pixelated Detector—Application in Mechanical Testing

Fast tomography measurements are still done almost exclusively within the domain of synchrotrons. However, recent progress in radio diagnostic instrumentation has enabled researchers to perform time-lapse computed tomography (4-D CT) even under laboratory conditions with standard X-ray sources. Thus, fast time-dependent processes within materials with relatively high X-ray attenuation can be monitored. This paper describes the in situ tomographic monitoring of crack formation and propagation in a quasi-brittle silicate matrix composite subjected to three-point bending. A 3-D CT volume containing the region of interest in the specimen is imaged over a period of time, while the continuously increasing load causes crack initiation and propagation, creating a dynamic volume data set. An acquisition time of 50 s for one full-angle tomography with 400 projections makes this tomographic system one of the fastest systems in the world. The resulting visualizations provide qualitative information concerning progressive crack propagation within areas of lower material density. Differential images then allow displaying the spatial orientation of the crack over time. The results were further processed for a quantitative analysis of image quality using various methods of beam hardening correction.

Preliminary study of time maximum intensity projection computed tomography imaging for the detection of early ischemic change in patient with acute ischemic stroke.

Noncontrast computed tomography (NCCT) has been used for the detection of early ischemic change (EIC); however, correct interpretation of NCCT findings requires much clinical experience. This study aimed to assess the accuracy of time maximum intensity projection computed tomography technique (tMIP), which reflects the maximum value for the time phase direction from the dynamic volume data for each projected plane, for detection of EIC, against that of NCCT.Retrospective review of NCCT, cerebral blood volume in CT perfusion (CTP-CBV), and tMIP of 186 lesions from 280 regions evaluated by Alberta Stroke Program Early CT Score (ASPECTS) in 14 patients with acute middle cerebral artery stroke who had undergone whole-brain CTP using 320-row area detector CT was performed. Four radiologists reviewed EIC on NCCT, CTP-CBV, and tMIP in each ASPECTS region at onset using the continuous certainty factor method. Receiver operating characteristic analysis was performed to compare the relative performance for detection of EIC. The correlations were evaluated.tMIP-color showed the best discriminative value for detection of EIC. There were significant differences in the area under the curve for NCCT and tMIP-color, CTP-CBV (P < .05). Scatter plots of ASPECTS showed a positive significant correlation between NCCT, tMIP-gray, tMIP-color, and the follow-up study (NCCT, r = 0.32, P = .0166; tMIP-gray, r = 0.44, P = .0007; tMIP-color, r = 0.34, P = .0104).Because tMIP provides a high contrast parenchymal image with anatomical and vascular information in 1 sequential scan, it showed greater accuracy for detection of EIC and predicted the final infarct extent more accurately than NCCT based on ASPECTS.

Temporal Scalability of Dynamic Volume Data Using Mesh Compensated Wavelet Lifting.

Due to their high resolution, dynamic medical 2D+t and 3D+t volumes from computed tomography (CT) and magnetic resonance tomography (MR) reach a size which makes them very unhandy for teleradiologic applications. A lossless scalable representation offers the advantage of a down-scaled version which can be used for orientation or previewing, while the remaining information for reconstructing the full resolution is transmitted on demand. The wavelet transform offers the desired scalability. A very high quality of the lowpass sub-band is crucial in order to use it as a down-scaled representation. We propose an approach based on compensated wavelet lifting for obtaining a scalable representation of dynamic CT and MR volumes with very high quality. The mesh compensation is feasible to model the displacement in dynamic volumes which is mainly given by expansion and contraction of tissue over time. To achieve this, we propose an optimized estimation of the mesh compensation parameters to optimally fit for dynamic volumes. Within the lifting structure, the inversion of the motion compensation is crucial in the update step. We propose to take this inversion directly into account during the estimation step and can improve the quality of the lowpass sub-band by 0.63 and 0.43 dB on average for our tested dynamic CT and MR volumes at the cost of an increase of the rate by 2.4% and 1.2% on average.

Four-dimensional computed tomography (4DCT): A review of the current status and applications.

The applications of conventional computed tomography (CT) have been widely researched and implemented in clinical practice. A recent technological innovation in the field of CT is the emergence of four-dimensional computed tomography (4DCT), where a three-dimensional computed tomography volume containing a moving structure is imaged over a period of time, creating a dynamic volume data set. 4DCT has previously been mainly utilised in the setting of radiation therapy planning, but with the development of wide field of view CT, 4DCT has opened major avenues in the diagnostic arena. The aim of this study is to provide a comprehensive narrative review of the literature regarding the current clinical applications of 4DCT. The applications reviewed include both routine diagnostic usage as well as an appraisal of the current research literature. A systematic review of the studies related to 4DCT was conducted. The Medline database was searched using the MeSH subject heading 'Four-Dimensional Computed Tomography'. After excluding non-human and non-English papers, 2598 articles were found. Further exclusion criteria were applied, including date range (since wide field of view CT was introduced in 2007), and exclusion of technical/engineering/physics papers. Further filtration of papers included identification of Review papers. This process yielded 67 papers. Of these, exclusion of papers not specifically discussing 4DCT (cone beam, 4D models) yielded 38 papers. As part of the review, the technique for 4DCT is described, with perspectives as to how it has evolved and its benefits in different clinical indications.

A DIGITAL MODEL FRAMEWORK OF METABOLIC SYSTEM BASED ON VISIBLE HUMAN DATA SET

Digital model of human metabolic system incorporated with real anatomical structure can be seen as an important tool in order to understand and study the processes of metabolism. This paper presented a whole body digital model framework of [18F]2-fluoro-2-deoxy-D-glucose (FDG) metabolism based on the segmented Visible Human Project (VHP) data set as the anatomical structure framework. First, the blood time-activity curve (BTAC) and the tissues time-activity curves (TTAC) were obtained from kinetic analysis. According to the obtained BTAC and TTACs, a set of corresponding values were assigned to the segmented VHP image frames. Thus a set of dynamic volume data were derived to show the 18F distribution in human body for the predetermined sampling schedule. Finally, the simulated FDG distribution was visualized by coronal, axial, and sagittal slices and volume rendering method. The model established here was especially for the metabolism of FDG; however, the modeling method is general for all tracers. The proposed model represented functional information of dynamical process of human metabolism with high visualization resolution. The results of modeling and visualization provide a useful tool for education and research on nuclear imaging, and may provide a novel technical platform for the study of pharmacokinetics.

135時系列ボリュームデータマイニングのための位相解析アプローチ

This paper takes advantage of a 3D field topology analysis for automating transfer function design aiming at volume data mining. The conventional Reeb graph-based approach to describe the topological features of 3D surfaces is extended to capture the topological skeleton of a volumetric field. Based on the analysis results, which are represented in the form of hyper Reeb graph, we propose two principles to design appropriate color/opacity transfer functions for direct volume rendering. Feasibility study of the present methodology is performed with a large scale 4D simulated dataset from atomic collision research. In analyzing the dynamic volume data, it turned out to be effective to use transfer functions designed appropriately at each time step. The basic idea of another approach with a higher order hyper Reeb graph to dynamic volume data mining is also discussed.