Biomedical subjects

Michael Grasruck

Publications and source records attributed to Michael Grasruck.

4 recordsLinked to original sources

PubMed2006

Material differentiation by dual energy CT: initial experience.

The aim of this study was to assess the feasibility of a differentiation of iodine from other materials and of different body tissues using dual energy CT. Ten patients were scanned on a SOMATOM Definition Dual Source CT (DSCT; Siemens, Forchheim, Germany) system in dual energy mode at tube voltages of 140 and 80 kVp and a ratio of 1:3 between tube currents. Weighted CT Dose Index ranged between 7 and 8 mGy, remaining markedly below reference dose values for the respective body regions. Image post-processing with three-material decomposition was applied to differentiate iodine or collagen from other tissue. The results showed that a differentiation and depiction of contrast material distribution is possible in the brain, the lung, the liver and the kidneys with or without the underlying tissue of the organ. In angiographies, bone structures can be removed from the dataset to ease the evaluation of the vessels. The differentiation of collagen makes it possible to depict tendons and ligaments. Dual energy CT offers a more specific tissue characterization in CT and can improve the assessment of vascular disease. Further studies are required to draw conclusions on the diagnostic value of the individual applications.

Algorithms↗

PubMed2006

Ultra-high resolution flat-panel volume CT: fundamental principles, design architecture, and system characterization.

Digital flat-panel-based volume CT (VCT) represents a unique design capable of ultra-high spatial resolution, direct volumetric imaging, and dynamic CT scanning. This innovation, when fully developed, has the promise of opening a unique window on human anatomy and physiology. For example, the volumetric coverage offered by this technology enables us to observe the perfusion of an entire organ, such as the brain, liver, or kidney, tomographically (e.g., after a transplant or ischemic event). By virtue of its higher resolution, one can directly visualize the trabecular structure of bone. This paper describes the basic design architecture of VCT. Three key technical challenges, viz., scatter correction, dynamic range extension, and temporal resolution improvement, must be addressed for successful implementation of a VCT scanner. How these issues are solved in a VCT prototype and the modifications necessary to enable ultra-high resolution volumetric scanning are described. The fundamental principles of scatter correction and dose reduction are illustrated with the help of an actual prototype. The image quality metrics of this prototype are characterized and compared with a multi-detector CT (MDCT).

Algorithms↗

PubMed2005

First performance evaluation of a dual-source CT (DSCT) system.

We present a performance evaluation of a recently introduced dual-source computed tomography (DSCT) system equipped with two X-ray tubes and two corresponding detectors, mounted onto the rotating gantry with an angular offset of 90 degrees . We introduce the system concept and derive its consequences and potential benefits for electrocardiograph [corrected] (ECG)-controlled cardiac CT and for general radiology applications. We evaluate both temporal and spatial resolution by means of phantom scans. We present first patient scans to illustrate the performance of DSCT for ECG-gated cardiac imaging, and we demonstrate first results using a dual-energy acquisition mode. Using ECG-gated single-segment reconstruction, the DSCT system provides 83 ms temporal resolution independent of the patient's heart rate for coronary CT angiography (CTA) and evaluation of basic functional parameters. With dual-segment reconstruction, the mean temporal resolution is 60 ms (minimum temporal resolution 42 ms) for advanced functional evaluation. The z-flying focal spot technique implemented in the evaluated DSCT system allows 0.4 mm cylinders to be resolved at all heart rates. First clinical experience shows a considerably increased robustness for the imaging of patients with high heart rates. As a potential application of the dual-energy acquisition mode, the automatic separation of bones and iodine-filled vessels is demonstrated.

Coronary Angiography↗

PubMedDate not supplied

Inherently 3-dimensional method for measurement of computed tomographic resolution anisotropy.

OBJECTIVE: Current techniques to measure computed tomography (CT) spatial resolution use separate methods for in-plane and out-of-plane directions. The growing use of near-isotropic voxel size necessitates a new single method that inherently measures resolution in any direction. METHOD: We introduce a method using a set of numerous glass microspheres suspended in a small volume from which a mean sphere image is constructed. Projecting asymptotes after imaging different microsphere sets with decreasing diameters provides an inherently 3-dimensional measure of spatial resolution and anisotropy. We apply the method to both a flat-panel and multidetector CT scanner. RESULTS: The full-width at half-maximum from line profiles through mean sphere in transverse directions corresponds to known microsphere diameters. Increased longitudinal full-width at half-maximum corresponds to known anisotropy, which is larger for a multidetector CT scanner than for a flat-panel CT scanner. CONCLUSIONS: A new single method to measure CT resolution is inherently isotropic.

Anisotropy↗