TESS offers rapid T1 and T2 quantification within one single scan, and in particular B1 -insensitive T2 estimation. As a result, the new proposed method is of high interest for fast and reliable high-resolution T2 mapping, especially of the musculoskeletal system at high to ultra-high fields.

Heule, R., Bruder, C., Burgarth, D., Stojanovi?, V. M. (2010). Local quantum control of Heisenberg spin chains, Physical Review A, 82, Article No: 052333Motivated by some recent results of quantum control theory, we discuss the feasibility of local operator control in arrays of interacting qubits modeled as isotropic Heisenberg spin chains. Acting on one of the end spins, we aim at finding piecewise-constant control pulses that lead to optimal fidelities for a chosen set of quantum gates. We analyze the robustness of the obtained results for the gate fidelities to random errors in the control fields, finding that with faster switching between piecewise-constant controls the system is less susceptible to these errors. The observed behavior falls into a generic class of physical phenomena that are related to a competition between resonance- and relaxation-type behavior, exemplified by motional narrowing in NMR experiments. Finally, we discuss how the obtained optimal gate fidelities are altered when the corresponding rapidly varying piecewise-constant control fields are smoothened through spectral filtering.Peer reviewe

Purpose Relaxation and dephasing of water protons embedded in a vascular network is driven by local magnetic field inhomogeneities around deoxygenated blood vessels. These effects strongly depend on the relation between mean diffusion length and diameter of blood vessels, as well as on the chosen imaging sequence. In this work, the BOLD sensitivity of steady‐state sequences as a function of vessel size, field strength, and sequence parameters are analyzed. Methods Steady‐state magnetization within a network of artificial cylinders is simulated with Monte Carlo methods for different coherence pathways. In addition, measurements on microspheres were performed to confirm theoretical results. Results Simulations and phantom results demonstrate a vessel size‐dependent signal attenuation effect of all coherence pathways. Both the FID and ECHO pathways show a signal profile similar to spin echo sequences where in the static dephasing regime the effect of larger vessels is suppressed. Conclusion The BOLD effect measured in steady‐state sequences is most sensitive to microvessels and might therefore be closer to the underlying neuronal event compared to gradient echo sequences.

Based on a global T2 estimate, the accuracy of VFA T1 relaxometry in the human brain can substantially be improved compared with conventional approaches which rely on the generally wrong assumption of ideal spoiling.