Siemens Aktiengesellschaft

Siemens Healthcare Gmbh

Michael Koehler

Thorsten Speckner

George William Ferguson

Thorsten Feiweier

Dieter Ritter

Wilhelm Horger

Michael Wullenweber

Daniel Niederloehner

Constantin Von Deuster

Markus Vester

Dominik Paul

Alto Stemmer

Flavio Carinci

Rainer Schneider

Juergen Nistler

Rene Gumbrecht

Franz Hebrank

Uvo Hoelscher

Wilfried Landschuetz

The present disclosure relates to operating an MR system in which MR signals of an object under examination are acquired in an examining region using a multi echo imaging sequence, in which an RF excitation pulse and a plurality of RF refocusing pulses are applied. The techniques include determining a first accumulated phase of a magnetization in the object under examination. Then, a second accumulated phase of the magnetization in the object under examination is determined due to concomitant magnetic fields occurring between a second pair of consecutive RF pulses. Finally, it is determined whether a deviation from the predefined relationship is larger than a threshold and, if this is the case, a measure is applied in view of the fact that the deviation is larger than the threshold.

Minimization of effects of concomitant fields in multi echo imaging

Techniques are disclosed for acquiring MR signals of an object under examination in an MR system using a multi echo imaging sequence. The method comprises the steps of applying an RF excitation pulse to the object to generate a transverse magnetization, applying at least two RF refocusing pulses for refocusing the transverse magnetization to generate at least two MR spin echoes for the RF excitation pulse, applying a first magnetic field gradient in a read out direction between the RF excitation pulse and the first of the at least two RF refocusing pulses, applying a second magnetic field gradient in the read out direction after each of the at least two RF refocusing pulses such that the zeroth and first gradient moment is substantially zero for the second magnetic field gradient, and acquiring the at least two MR spin echoes during the at least two second magnetic field gradients.

Minimization of signal losses in multi-echo imaging

In a method and magnetic resonance (MR) apparatus for acquiring MR data from a volume of an object in which first and second excitable spin types are present that differ in their Larmor frequencies by a chemical shift, an MR sequence with at least one radio-frequency pulse sequence selectively excites the first spin type or selectively suppresses MR signals of the second spin type. A B0 map describing the basic field distribution in a region of interest of the volume is established. First and second items of distribution information, which respectively describe the spectral distribution of Larmor frequencies of the first and second spin types, are derived from the B0 map. A pulse sequence parameter that describes the excitation spectrum of the radio-frequency pulse sequence is optimized based on the items of distribution information, with regard to a quality criterion that optimizes selective excitation and/or suppression.

Method and apparatus for acquiring magnetic resonance data

In a method for operating a magnetic resonance (MR) facility during recording of MR data by using a MR sequence including a saturation module for a spin type to be saturated, in which a high-frequency saturation pulse is emitted between first and second spoiler gradient pulses, and multiple further gradient pulses apart from the spoiler gradient pulses, eddy current data is determined. The eddy current data describes eddy currents existing during emission of the saturation pulse and resulting from the further gradient pulses. Further, a pulse parameter of the first spoiler gradient pulse is selected based on the eddy current data such that the eddy currents generated by the first spoiler gradient pulse compensate for at least part of the eddy currents described by the eddy current data during emission of the saturation pulse. The facility is controlled to emit the first spoiler gradient pulse with the selected pulse parameter.

Method and system for operating a magnetic resonance facility

In a magnetic resonance tomography (MRT) apparatus and operating method, a field of view for imaging a target object is acquired. A relative position of this field of view in relation to a receiving space of the MRT scanner, in which the target object is received, is then automatically determined. A radio-frequency (RF) pulse to be used by the MRT scanner for imaging the target object is then automatically adjusted depending on this relative position. An excitation angle produced in the field of view by the RF pulse is changed compared to the use of the corresponding unadjusted RF pulse.

Magnetic resonance apparatus and operating method with adjustment of the excitation angle dependent on data acquisition field of view

In a method for operating a medical imaging apparatus having multiple sub-systems controlled by a controller in a coordinated manner in order to perform a measurement sequence, a number of first setting parameters are chosen to be constant for a complete measurement sequence, and after a static adjustment, a dynamic adjustment of second setting parameters, which are defined by control signals for the measurement sequence and that can vary while a measurement sequence is being performed, takes place. Base data defining underlying conditions specific to the patient to be imaged are measured for the total imaging volume in a measurement sequence. Reference values for the setting parameters that affect the underlying conditions are saved in association with the base data during the measurement sequence. If the present values of the setting parameters adjusted during the static adjustment differ from the reference values, updated base data are calculated based on the difference between the present values and the reference values, and the current base data are used for local optimization in the dynamic adjustment.

Medical imaging examination apparatus having multiple sub-systems and method for the operation thereof

In a method and magnetic resonance apparatus for determining a B1 field map in a scanner of the apparatus, the B1 field map describing a local field distribution of a B1 field resulting from excitation pulses radiated in a measurement sequence, first and second measured values are acquired from a region in which nuclear spins are excited by an excitation pulse having an assigned flip angle, and a provisional flip angle is determined from the first and second measured values. A correction factor, dependent on the pulse shape of a selected excitation pulse, is then determined, and the provisional flip angle is multiplied thereby to obtain a corrected value for entry into said B1 field map.

Method and apparatus for determining a B1 field map in a magnetic resonance scanner

In a method and magnetic resonance apparatus for performing at least one adjusting measurement for the magnetic resonance apparatus, a localizing measurement is performed using the magnetic resonance apparatus and a localization dataset is created, and at least one examination region on the localization dataset. At least one examination region of the localization dataset is selected, and at least one adjusting measurement is performed according to the at least one selected examination region. The at least one adjusting measurement can be the calculation of a radio-frequency pulse amplitude, the calculation of a system frequency and the calculation of at least one current of at least one shim coil.

Method and magnetic resonance apparatus for performing an adjusting measurement

In a method and apparatus for correcting image data acquired by an image data acquisition scanner of a magnetic resonance system, a reception profile of a reception antenna of the magnetic resonance scanner is determined. A correction function is determined by which an asymmetry of the reception profile with respect to a symmetry plane is corrected. Furthermore, image data are received and corrected by multiplying the intensity values of the image data with the determined correction function.

Image correction during magnetic resonance dependent on the reception profile of the reception antenna

In a method and apparatus for acquiring a magnetic resonance image data set of a scan area of an examination subject, the image data are acquired with a magnetic resonance apparatus having a transmitter coil that emits a radio-frequency signal having at least two transmission channels so that different polarizations of the radio-frequency signal are produced, and a magnetic resonance sequence is used to acquire raw data for the magnetic resonance image data set, wherein raw data are acquired during at least two scanning operations with the magnetic resonance sequence, with different polarizations of the radio-frequency signals being used for at least two of the at least two scanning operations, following which the magnetic resonance image data set is determined by averaging the raw data.

Method and apparatus for acquiring a magnetic resonance image data set and magnetic resonance device

In a magnetic resonance method and apparatus to determine a subject-specific Bdistribution of an examination subject in a measurement volume in the magnetic resonance apparatus, a first measurement data set of the examination subject is acquired using a first pulse sequence, a second measurement data set of the examination subject is acquired using a second pulse sequence, and a third measurement data set of the examination subject is acquired using a third pulse sequence. A first phase is determined from the first measurement data set, a second phase from the second measurement data set and a third phase from the third measurement data set. A relevant phase shift is calculated from the first phase, the second phase and the third phase, and the Bdistribution are determined from the calculated relevant phase shift.

Method and apparatus to determine a subject-specific B1 distribution of an examination subject in a measurement volume of a magnetic resonance apparatus

In a method for correction of a B0 field map measured with a magnetic resonance device, that describes deviations from a nominal field strength in the homogeneity area of the magnetic resonance device by deviations from a nominal frequency for protons bonded to water, the deviations being represented as Larmor frequency values for different picture elements shifted by chemical shifts, the B0 field map is recorded with spins of the fat and water protons not in phase. The B0 field map is segmented by evaluating the differences of the Larmor frequency values of adjacent picture elements of the B0 field map in at least two contiguous clusters. For each cluster, a decision is made on the basis of a smoothness criterion and a compactness criterion as to whether a cluster containing a majority of protons bonded into fat is involved. Clusters identified as containing a majority of protons bonded into fat are corrected by lowering the Larmor frequency values by the difference between the nominal frequency for protons bonded into water and the corresponding nominal frequency for protons bonded to fat.

Method and magnetic resonance apparatus for correction of a B0 map for chemical shifts

In a method and magnetic resonance (MR) system to acquire MR data within a volume segment, the MR data are repeatedly acquired with a sequence that which includes the following steps. A first resonant RF pulse is radiated and a second resonant RF pulse is radiated. A dephasing first gradient is applied after the first resonant RF pulse and before the second resonant RF pulse. A third resonant RF pulse is radiated after the second resonant RF pulse. A second gradient is applied after the third RF pulse in order to refocus a stimulated echo of a magnetization component prepared by the first gradient. MR data are read out, and a fourth resonant RF pulse is radiated after the readout of the MR data, to reduce the longitudinal magnetization.

Magnetic resonance system and method to acquire MR data and to determine a B1 magnetic field

In a method to acquire magnetic resonance (MR) data within a volume segment with a magnetic resonance system, the MR data are repeatedly acquired with a sequence that includes radiating a first resonant RF pulse, radiating a second resonant RF pulse, applying a dephasing first gradient after the first resonant RF pulse and before the second resonant RF pulse, radiating a third resonant RF pulse after the second resonant RF pulse, applying a second gradient after the third RF pulse in order to refocus a stimulated echo of a magnetization component prepared by the first gradient, and read out MR data. At least one of the first gradient and/or the second gradient is/are different in a respective repetition of the sequence and an additional repetition of the sequence that directly follows the respective repetition.

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Nuremberg, Germany

Michael Koehler