Functional magnetic resonance imaging (fMRI) is widely used to pinpoint active brain areas. Changes in neuronal activity modulate the local blood oxygenation level, and the associated modulation of the magnetic field homogeneity can be detected with magnetic resonance imaging. Thus, the blood oxygenation level-dependent (BOLD) fMRI indirectly measures neuronal activity. Similar modulation of ma...

While most diffusion-weighted imaging (DWI) is acquired using single-shot diffusion-weighted spin-echo echo-planar imaging, steady-state DWI is an alternative method with the potential to achieve higher-resolution images with less distortion. Steady-state DWI is, however, best suited to a segmented three-dimensional acquisition and thus requires three-dimensional navigation to fully correct for...

Diffusion-weighted magnetic resonance (MR) imaging (DWI) is increasingly applied to evaluate tumors in the abdomen and pelvis. However, DWI is susceptible to a variety of artifacts that arise from motion, use of strong gradient pulses, and echo-planar imaging technique. We discuss practical issues to help radiologists optimize the use of DWI to evaluate tumors in the body, including breath-hold...

Anatomical MRI studies at 7T have demonstrated the ability to provide high-quality images of human tissue in vivo. However, diffusion-weighted imaging at 7T is limited by the increased level of artifact associated with standard, single-shot, echo-planar imaging, even when parallel imaging techniques such as generalized autocalibrating partially parallel acquisitions (GRAPPA) are used to reduce ...

Diffusion-weighted imaging (DWI) obtained with interleaved echo-planar imaging (EPI) pulse sequence has great potential of characterizing brain tissue properties at high spatial-resolution. However, interleaved EPI based DWI data may be corrupted by various types of aliasing artifacts. First, inconsistencies in k-space data obtained with opposite readout gradient polarities result in Nyquist ar...

Goal This lecture aims to give an overview of ultrafast image techniques such as echo-planar imaging (EPI) and spiral imaging. While these techniques offer significant speed improvement, they are often accompanied by practical issues that degrade the quality of the images, thereby compromising their benefits. Therefore, it is important to take proper control of the tradeoff between imaging spee...

Single-shot line scan imaging (LSI) was adapted to diffusion-weighted (DW) MRI by replacing the initial 90 degrees radiofrequency pulse of the underlying high-speed stimulated echo sequence by a DW spin-echo preparation period. Implementation on a 2. 0 T whole-body MRI system yielded DW images of the human brain with b factors of 750 s mm(-2) and total imaging times of about 500 ms either for a...

Magnetic field inhomogeneity causes artifacts in MRI. For example, in single-shot echo-planar imaging (EPI), they often appear as severe geometric distortions along the phase-encoding direction. Sensitivity encoding (SENSE) is useful in reducing the distortion in EPI since it only acquires partial k-space data using multiple receiver channels. In SENSE, a reference scan usually needs to be perf...

Three infants were studied by echo planar imaging after repair of congenital diaphragmatic hernias. Total lung volume and individual lung volumes were estimated using echo planar imaging. In the two patients with left sided hernias, the right lung was more than twice as large as the left. The patient with a right sided hernia had developed emphysema on the right side, and the right lung was twi...

diffusion weighted imaging uses the signal loss associated with the random thermal motion of water molecules in the presence of magnetic field gradients to derive a number of parameters that reflect the translational mobility of the water molecules in tissues. with a suitable experimental set-up, it is possible to calculate all the elements of the local diffusion tensor (dt) and derived paramet...