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Wundrak S.,University of Ulm | Paul J.,University of Ulm | Ulrici J.,Sirona Dental Systems | Hell E.,Sirona Dental Systems | Rasche V.,University of Ulm
IEEE Transactions on Medical Imaging | Year: 2015

In golden angle radial magnetic resonance imaging a constant azimuthal radial profile spacing of 111.246·° guarantees a nearly uniform azimuthal profile distribution in k-space for an arbitrary number of radial profiles. Even though this profile order is advantageous for various real-time imaging methods, in combination with balanced steady-state free precession (SSFP) sequences the large azimuthal angle increment may lead to strong image artifacts, due to the varying eddy currents introduced by the rapidly switching gradient scheme. Based on a generalized Fibonacci sequence, a new sequence of smaller irrational angles is introduced (49.750·°, 32.039·°, 27.198·°, 23.628·°, ·). The subsequent profile orders guarantee the same sampling efficiency as the golden angle if at least a minimum number of radial profiles is used for reconstruction. The suggested angular increments are applied for dynamic imaging of the heart and the temporomandibular joint. It is shown that for balanced SSFP sequences, trajectories using the smaller golden angle surrogates strongly reduce the image artifacts, while the free retrospective choice of the reconstruction window width is maintained. © 2014 IEEE. Source

Ulrici J.,Sirona Dental Systems | Hell E.,Sirona Dental Systems
Magnetic Resonance in Medicine | Year: 2015

Purpose: To develop a self-gating method capable of assessing nonuniform motion, e.g., in cardiovascular magnetic resonance imaging of patients with severe arrhythmia, or for imaging of the temporomandibular joint. Methods: The proposed method allows cyclic motion trajectories with a nonuniform pace by replacing the one-dimensional gating signal of conventional image-based self-gating with a two-dimensional gating matrix. The resulting image quality is compared with conventional self-gating and real-time MRI. Results: Nonuniform self-gating resulted in superior image quality compared with conventional self-gating and the feasibility study showed significantly improved image sharpness (P<0.01). Further, improvements in image quality were shown compared with golden angle radial parallel sparse MRI. Conclusion: A new self-gating method was proposed that allows cardiovascular magnetic resonance of arrhythmic patients, which is a common problem in clinical practice. Further, the proposed method enables self-gated imaging of the temporomandibular joint. © 2015 Wiley Periodicals, Inc. Source

Sirona Dental Systems | Date: 2003-02-11

[ Pharmaceutical and sanitary preparations for dental use in supporting dental teeth restorations, medicated mouthwash, anti-inflammation preparations for oral mucous membrane, fillings for teeth, dental wax, dental abrasives, dental cements, dental amalgams, dental impression materials, dental polish, dental restoration compounds, dental rinses, adhesive materials for planning and execution of dental prostheses and implants, adhesive materials for gluing ceramic parts and teeth, ] dental ceramic blanks [, dental lacquer, matt lacquer for scanning teeth, dental composites, lining materials for dental use and oral prophylactics, adhesive materials for dental crowns and dental bridges, and unprocessed dental ceramic parts ]. Prerecorded computer programs for operating of dental and medical hardware components in the field of dentistry and medicine [, video cameras for medical and dental use, and electrical distribution console for dental hand pieces ]. [ Electric and pneumatic dental equipment, namely, dental drills, dental hand pieces, namely, contra-angle, straight, turbine, sandblasters, dental hand pieces for scaling, dental examination chairs, dental X-Ray diagnostic apparatus, dental prophylactic instruments, dental instruments, namely, picks, burrs, mirrors, medical and dental examination lamps, medical multi-function syringes, dental prostheses, dental inlays, dental overlays, dental crowns, dental veneers, dental bridges, ] grinding machines for machining medical and dental ceramics maintenance [, and sterilization centers, primarily comprised of sterilization chambers, instrument baskets, soaking trays ]. [ Financing services, namely, leasing of dental equipment ]. Computer services, namely, leasing access time to computer databases in the field of dentistry, dentistry services, leasing of dental equipment [, rental of medical equipment paying per use through telecommunication or prepared cards ]. Custom manufacture of dental prosthetics, and dental technician services, namely, gliding, pottery firing, and galvanizing. Training in the field of dental science, conducting seminars in the field of dental science.

Keller D.U.J.,Karlsruhe Institute of Technology | Weiss D.L.,Sirona Dental Systems | Dossel O.,Karlsruhe Institute of Technology | Seemann G.,Sirona Dental Systems
IEEE Transactions on Biomedical Engineering | Year: 2012

Despite the commonly accepted notion that action potential duration (APD) is distributed heterogeneously throughout the ventricles and that the associated dispersion of repolarization is mainly responsible for the shape of the T-wave, its concordance and exact morphology are still not completely understood. This paper evaluated the T-waves for different previously measured heterogeneous ion channel distributions. To this end, cardiac activation and repolarization was simulated on a high resolution and anisotropic biventricular model of a volunteer. From the same volunteer, multichannel ECG data were obtained. Resulting transmembrane voltage distributions for the previously measured heterogeneous ion channel expressions were used to calculate the ECG and the simulated T-wave was compared to the measured ECG for quantitative evaluation. Both exclusively transmural (TM) and exclusively apico-basal (AB) setups produced concordant T-waves, whereas interventricular (IV) heterogeneities led to notched T-wave morphologies. The best match with the measured T-wave was achieved for a purely AB setup with shorter apical APD and a mix of AB and TM heterogeneity with M-cells in midmyocardial position and shorter apical APD. Finally, we probed two configurations in which the APD was negatively correlated with the activation time. In one case, this meant that the repolarization directly followed the sequence of activation. Still, the associated T-waves were concordant albeit of low amplitude. © 2006 IEEE. Source

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