Long spin coherence lifetimes are realized for ensembles of electronic spin impurities in solid state spin systems, for example NV color centers in diamond, by using spin-control RF pulse sequences to provide dynamic decoupling of the ensembles of spin impurities from environmental sources of decoherence such as dipolar and hyperfine interactions with proximal spin and other paramagnetic impurities in diamond. In this way, the measurement sensitivity of the coherent evolution of ensembles of solid state spin impurities are increased. Using the Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence, the spin coherence lifetimes of NV ensembles can be extended to more than 2 ms in room temperature diamond, and sensitivity of magnetometry that uses NV ensembles can be increased.

A method and apparatus are provided to perform controlled aliasing in parallel imaging (CAIPI) using time shifts between the radio frequency (RF) excitation pulses and the waveform of the slice-select gradient field to shift respective sampling points within the two-dimensions of k-space corresponding to phase encoding. Thus, a CAIPI sampling pattern is generated using time shifts, rather than by modulating the RF excitation pulses or gradient fields.

In a method and apparatus to quickly determine regions of modified temperature in a sample volume by magnetic resonance tomography using a multi-echo sequence, one or more one-dimensional or two-dimensional images of regions of modified temperature are respectively determined.

In a method to associate k-space lines with echo trains of raw magnetic resonance data, parallel k-space lines orthogonally intersect a plane at respective intersection points. Each echo train has a trajectory length, and the k-space lines are associated with the echo trains such that a sum of trajectory lengths of all echo trains is minimal. The trajectory length TL of an echo train is defined by $\mathrm{TL}=\underset{i=1}{\overset{L-1}{.Math.}}\stackrel{\_}{P_i{P}_{i+1}}$
wherein L is a sequence of k-space lines, P.sub.i is an intersection point of the i-th k-space line of the echo train with the plane; and P.sub.iP.sub.i+1 is the length of the path from the i-th intersection point to the (i+1)-th intersection point.

A method and a system for measuring and calibrating an imaging magnetic field in a magnetic resonance apparatus are provided. The method includes: providing the imaging magnetic field, where the imaging magnetic field is adapted for scanning an object; sampling a signal corresponding to the imaging magnetic field; processing the signal to obtain an actual magnetic field intensity; and calibrating based on a difference between the actual magnetic field intensity and a target magnetic field intensity. The system includes: a magnetic component, adapted for scanning an object to be imaged; a sampling unit, adapted for sampling a signal corresponding to the imaging magnetic field; a processing unit, adapted for processing the signal to obtain an actual magnetic field intensity; a calibration unit, adapted for calibrating based on a difference between the actual magnetic field intensity and a target magnetic field intensity; and a control unit, adapted for controlling the system.

In a method and magnetic resonance (MR) apparatus to acquire MR data of a target region that includes a metal object, an MR sequence that includes at least one radio-frequency excitation to be emitted via a radio-frequency coil arrangement is used. A radio-frequency coil arrangement having multiple coil elements that can be controlled independently with different amplitude and/or phase is used. The amplitudes and/or phases of the coil elements that describe the polarization of the radio-frequency field are selected to at least partially reduce artifacts arising in the metal object due to the radio-frequency excitation, in comparison to a homogeneous, circular polarization of the radio-frequency field of the radio-frequency field in the target region.

Apparatus, systems, and methods are disclosed for tracking movement over the ground or other surfaces of tools or instruments or equipment, such as buried object locators or other devices, and generating motion, position, location, mapping and/or related information for tracked locations, as well as measuring and storing associated signals and other information detected or generated during tracking.

Methods, systems, and devices for characterizing an anomalous fluid body in an earth formation using measurements in a borehole intersecting the formation. Methods include galvanically exciting a transient electric field in the earth formation which interacts with an anomalous fluid body in the earth formation remote from the borehole; galvanically receiving a corresponding transient electromagnetic (TEM) signal; and using at least one processor to estimate a value of a parameter of the anomalous fluid body using the corresponding transient signal.

A steering tool is movable by a drill string to form an underground bore along an intended path. A sensing arrangement of the steering tool detects its pitch and yaw orientations at a series of spaced apart positions along the bore, each position is characterized by a measured extension of the drill string. The steering tool further includes a receiver. At least one marker is positioned proximate to the intended path, for transmitting a rotating dipole field to expose a portion of the intended path to the field for reception by the receiver. The detected pitch orientation, the detected yaw orientation and the measured extension of the drill string are used in conjunction with magnetic information from the receiver to locate the steering tool. The steering tool may automatically use the magnetic information when it is available. A customized overall position determination accuracy can be provided along the intended path.

A device for measuring a variation (ΔC.sub.X) of a capacitance (C.sub.X), includes: elements for charging the capacitance (C.sub.X) on the basis of a supply voltage (V.sub.CC). elements for discharging the capacitance (C.sub.X) into a reference capacitance (C.sub.S) in a fixed number of discharges (x), elements for measuring a voltage (V.sub.S) and for detecting a threshold of voltage (V.sub.TH) across the terminals of the reference capacitance (C.sub.S). elements for charging with current (I.sub.C) the reference capacitance (C.sub.S) on the basis of the supply voltage (V.sub.CC) for a duration (t), after the transfer of charge from the capacitance (C.sub.X) into the reference capacitance (C.sub.S), and elements for measuring the variation between the duration (t) with respect to a previously measured duration so as to estimate the variation (ΔC.sub.X) of the capacitance (C.sub.X).