摘要:
A method and apparatus is disclosed for MR perfusion acquisition using a notched RF saturation pulse. In acquiring such MR data, a volume of slice locations is selected in which MR data is to be acquired. Each given slice is prepared with a notched RF saturation pulse which has a stop-band between a pair of pass-bands. The stop-band is designed to not affect the spins in the next slice in which MR data is to be acquired thereby effectively increasing the TI and increasing SNR and contrast simultaneously. Since the notched saturation pulse saturates all the spins outside of the notched stop-band, the blood in the ventricular chamber is effectively saturated so that the resulting perfusion images have blood pool suppression. Additionally, the use of a 90° presaturation RF pulse provides a high level of immunity to the effects of arrhythmias or other variations in the patient's heart rate. In order to keep the stop-band, or the notch, as wide as possible to overlap the boundaries of each slice location, it is preferable to interleave the acquisition of slice locations.
摘要:
The present invention includes a method and apparatus to perform rapid multi-slice MR imaging without ECG gating or requiring breath-holding that is capable of renal profusion analysis and angiographic screening. An ungated interleaved pulse sequence is applied in rapid succession, followed by a delay interval. The ungated interleaved pulse sequence is repeatedly played out with the predefined delay interval between each application of the pulse sequence. The resulting images provide not only a series of temporal phases of contrast-enhanced blood uptake for renal profusion analysis, but also provide enough dynamic range to include angiographic screening of the renal arteries.
摘要:
A system and method for arterial and venous discrimination in MR venography is disclosed. By setting a noise level in the phase image (that is proportional to the velocity encoding value) at a threshold level between that of the arterial signals and the venous signals during the diastole portion of the cardiac cycle and acquiring a phase contrast MR image during the diastole portion, the arterial signals are effectively suppressed and a venous only image can be reconstructed. Post-processing steps are disclosed which can alternatively provide an arterial only image. By separately reconstructing a magnitude image and a phase image map to produce a magnitude image and a phase image, a masking module can create an output displaying venous only or arterial only images based on a user selection. The present invention allows for a complete noninvasive angiography exam to be completed within approximately 30 minutes.
摘要:
An apparatus, system and method to determine a coordinate system of a heart includes an imager and a computer. The computer is programmed to acquire a first set of initialization imaging data from an anatomical region of a free-breathing subject. A portion of the first set of initialization imaging data includes organ data, which includes cardiac data. The computer is further programmed to determine a location of a central region of a left ventricle of a heart, where the location is based on the organ data and a priori information. The computer is also programmed to determine a short axis of the left ventricle based on the determined location, acquire a first set of post-initialization imaging data from the free-breathing subject from an imaging plane orientation based on the determination of the short axis, and reconstruct at least one image from the first set of post-initialization imaging data.
摘要:
A method and apparatus is disclosed to initially screen a patient's peripheral arterial vasculature for lesions, or stenotic vessels, using MR technology, and then grading the severity of any located stenosis. The invention includes tracking the passage of a contrast agent bolus through a patient, while acquiring a series of first MR images having low resolution. This initial examination uses flow sensitive bi-polar gradient waveforms with a gradient echo imaging pulse sequence to increase the sensitivity to lesion detectability. The bi-polar gradients generate a broad distribution of velocities in a large voxel. Relevant stenoses present in a voxel will result in intra-voxel flow dephasing in voxels immediate to and distal to the stenosis. After identifying a stenosis, a second MR image, having a higher resolution than the first, is used to grade the stenosis.
摘要:
A system and method for creating MR images using mask data that is copied forward for on-the-fly image subtraction for use within such techniques as MR angiography is disclosed. The invention includes acquiring an MR mask image comprised of a plurality of k-space lines, and then copying the k-space line data of the MR mask image into a number of different memory locations. The number of different memory locations corresponds to a preselected number of MR image acquisitions as set by an MR operator. The invention next includes acquiring the preselected number of MR images, each comprised of k-space line data. As the k-space line data is acquired, it is then immediately accumulated in one of the memory locations having the MR mask image k-space line data. By setting a polarity of the data stored, each acquired k-space line of an acquired MR image is subtracted from a corresponding k-space line of the MR mask image in real time. The image is then reconstructed using the subtracted k-space line data. After each additional MR image acquisition, the data is accumulated with the masked data, which result is used for reconstructing an MR image without the need to transfer the data to another workstation for separate processing or post-processing. In this manner, the acquired data is automatically subtracted on-the-fly, thereby yielding fluoroscopic images, for example, without the prior art penalties of excessive image reconstruction time and image post-processing time.
摘要:
A system and method is disclosed to combine both a fractional echo (k.sub.x) and a fractional NEX (k.sub.y) to reduce acquisition times and echo times in MR imaging. The method uses both zero-filling and homodyne reconstruction to construct concurrent fractional NEX and fractional echo data in a single image while minimizing any blurring effects. The system includes acquiring partial MRI data in the k.sub.x direction and acquiring partial MRI data in the k.sub.y direction. Once a partial echo and a partial NEX are acquired, the missing data is first zero-filled in the k.sub.x direction and Fourier transformed to acquire a full x direction data set. Next, the data is synthesized in the k.sub.y direction using a homodyne reconstruction technique to acquire a full data set in the k.sub.y direction. The full x,y data set can then be used to reconstruct an MR image with reduced acquisition and echo times. In order to minimize the effects of blurring in the resulting MR image, it is preferable to acquire at least an 80% fractional echo and a 60% fractional NEX. The system can be extended to any number of desirable dimensions.
摘要:
A uniform surface current density is approximated in an RF transmitting/receiving NMR coil by employing a plurality of discrete conductors having a resonantly distributed current. Inductive and capacitive lines provide a sinusoidal current distribution with various resonant modes providing different magnetic field orientations. The distributed current reduces losses. In a second order resonant mode, decoupling of the surface coil from a transmit coil is achieved without a blocking network.
摘要:
An apparatus includes a first magnetic resonance (MR) coil element configured to output a first set of MR data at a first output frequency and a first mixer coupled to the first MR coil element. The first mixer is configured to receive the first set of MR data from the first MR coil element and frequency translate the first set of MR data to a first offset frequency different from the first output frequency by a first offset value. The apparatus also includes a digitizer coupled to the first mixer and configured to convert the frequency-translated first set of MR data into a set of digital data and a transmission line coupled to the first mixer and to the digitizer, the transmission line configured to transmit the frequency-translated first set of MR data from the MR coil element to the digitizer without a balun coupled to the transmission line.
摘要:
The invention includes a technique for efficient multi-slice fast spin echo image acquisition with black blood contrast in cardiac imaging. The technique includes applying a non-selective inversion pulse, followed by a re-inversion pulse that is slice-selective over a region encompassing a plurality of slice selections. Execution of a series of RF excitation pulses with fast spin echo readout is timed such that signal from blood is near a null point before acquiring data for each spatial slice. For greater contrast consistency, the flip angles for the excitation pulses occurring before the null point can be reduced, and those occurring after the null point can be increased.