Optimizing signal‐to‐noise ratio of high‐resolution parallel single‐shot diffusion‐weighted echo‐planar imaging at ultrahigh field strengths

The potential signal‐to‐noise ratio (SNR) gain at ultrahigh field strengths offers the promise of higher image resolution in single‐shot diffusion‐weighted echo‐planar imaging the challenge being reduced T₂ and T₂* relaxation times and increased B₀ inhomogeneity which lead to geometric distortions and image blurring. These can be addressed using parallel imaging (PI) methods for which a greater range of feasible reduction factors has been predicted at ultrahigh field strengths—the tradeoff being an associated SNR loss. Using comprehensive simulations, the SNR of high‐resolution diffusion‐weighted echo‐planar imaging in combination with spin‐echo and stimulated‐echo acquisition is explored at 7 T and compared to 3 T. To this end, PI performance is simulated for coil arrays with a variable number of circular coil elements. Beyond that, simulations of the point spread function are performed to investigate the actual image resolution. When higher PI reduction factors are applied at 7 T to address increased image distortions, high‐resolution imaging benefits SNR‐wise only at relatively low PI reduction factors. On the contrary, it features generally higher image resolutions than at 3 T due to smaller point spread functions. The SNR simulations are confirmed by phantom experiments. Finally, high‐resolution in vivo images of a healthy volunteer are presented which demonstrate the feasibility of higher PI reduction factors at 7 T in practice. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.     

SNR‐optimized phase‐sensitive dual‐acquisition turbo spin echo imaging: A fast alternative to FLAIR

Phase‐sensitive dual‐acquisition single‐slab three‐dimensional turbo spin echo imaging was recently introduced, producing high‐resolution isotropic cerebrospinal fluid attenuated brain images without long inversion recovery preparation. Despite the advantages, the weighted‐averaging‐based technique suffers from noise amplification resulting from different levels of cerebrospinal fluid signal modulations over the two acquisitions. The purpose of this work is to develop a signal‐to‐noise ratio‐optimized version of the phase‐sensitive dual‐acquisition single‐slab three‐dimensional turbo spin echo. Variable refocusing flip angles in the first acquisition are calculated using a three‐step prescribed signal evolution while those in the second acquisition are calculated using a two‐step pseudo‐steady state signal transition with a high flip‐angle pseudo‐steady state at a later portion of the echo train, balancing the levels of cerebrospinal fluid signals in both the acquisitions. Low spatial frequency signals are sampled during the high flip‐angle pseudo‐steady state to further suppress noise. Numerical simulations of the Bloch equations were performed to evaluate signal evolutions of brain tissues along the echo train and optimize imaging parameters. In vivo studies demonstrate that compared with conventional phase‐sensitive dual‐acquisition single‐slab three‐dimensional turbo spin echo, the proposed optimization yields 74% increase in apparent signal‐to‐noise ratio for gray matter and 32% decrease in imaging time. The proposed method can be a potential alternative to conventional fluid‐attenuated imaging. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

High‐resolution functional MRI at 3 T: 3D/2D echo‐planar imaging with optimized physiological noise correction

High‐resolution functional MRI (fMRI) offers unique possibilities for studying human functional neuroanatomy. Although high‐resolution fMRI has proven its potential at 7 T, most fMRI studies are still performed at rather low spatial resolution at 3 T. We optimized and compared single‐shot two‐dimensional echo‐planar imaging (EPI) and multishot three‐dimensional EPI high‐resolution fMRI protocols. We extended image‐based physiological noise correction from two‐dimensional EPI to multishot three‐dimensional EPI. The functional sensitivity of both acquisition schemes was assessed in a visual fMRI experiment. The physiological noise correction increased the sensitivity significantly, can be easily applied, and requires simple recordings of pulse and respiration only. The combination of three‐dimensional EPI with physiological noise correction provides exceptional sensitivity for 1.5 mm high‐resolution fMRI at 3 T, increasing the temporal signal‐to‐noise ratio by more than 25% compared to two‐dimensional EPI. Magn Reson Med, 2013. © 2012 The Authors. Magnetic Resonance in Medicine Published by Wiley Periodicals, Inc. on behalf of International Society of Medicine in Resonance.     

Temporal SNR characteristics in segmented 3D‐EPI at 7T

Three‐dimensional segmented echo planar imaging (3D‐EPI) is a promising approach for high‐resolution functional magnetic resonance imaging, as it provides an increased signal‐to‐noise ratio (SNR) at similar temporal resolution to traditional multislice 2D‐EPI readouts. Recently, the 3D‐EPI technique has become more frequently used and it is important to better understand its implications for fMRI. In this study, the temporal SNR characteristics of 3D‐EPI with varying numbers of segments are studied. It is shown that, in humans, the temporal variance increases with the number of segments used to form the EPI acquisition and that for segmented acquisitions, the maximum available temporal SNR is reduced compared to single shot acquisitions. This reduction with increased segmentation is not found in phantom data and thus likely due to physiological processes. When operating in the thermal noise dominated regime, fMRI experiments with a motor task revealed that the 3D variant outperforms the 2D‐EPI in terms of temporal SNR and sensitivity to detect activated brain regions. Thus, the theoretical SNR advantage of a segmented 3D‐EPI sequence for fMRI only exists in a low SNR situation. However, other advantages of 3D‐EPI, such as the application of parallel imaging techniques in two dimensions and the low specific absorption rate requirements, may encourage the use of the 3D‐EPI sequence for fMRI in situations with higher SNR. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.     

High‐resolution fMRI with higher‐order generalized series imaging and parallel imaging techniques (HGS‐parallel)

Purpose

To develop a novel approach for high‐resolution functional MRI (fMRI) using the conventional gradient‐echo sequence.

Materials and Methods

Echo‐planar imaging (EPI) techniques have generally been used for fMRI studies due to their fast imaging time. However, it is difficult for studying brain function at the submillimeter level using this sequence. In addition, EPI techniques have some drawbacks, such as Nyquist ghosts and geometric distortions in the reconstructed images, and subsequently require additional postprocessing to reduce these artifacts. One way of solving these problems is to acquire fMRI data by means of a conventional gradient‐echo imaging sequence instead of EPI. To provide a fast imaging time, the proposed method combines higher‐order generalized series (HGS) imaging with a parallel imaging technique which is called the HGS‐parallel technique.

Results

The proposed HGS‐parallel technique achieves a 12.8‐fold acceleration in imaging time without the cost of spatial resolution. The proposed method was verified through the application of fMRI studies on normal subjects.

Conclusion

This study suggests that the proposed method can be used for high‐resolution fMRI studies without the geometric distortion and the Nyquist ghost artifacts compared to EPI. J. Magn. Reson. Imaging 2009;29:924–936. © 2009 Wiley‐Liss, Inc.     

Optimized T1-weighted contrast for single-slab 3D turbo spin-echo imaging with long echo trains: application to whole-brain imaging.

T(1)-weighted contrast is conventionally obtained using multislice two-dimensional (2D) spin-echo (SE) imaging. Achieving isotropic, high spatial resolution is problematic with conventional methods due to a long acquisition time, imperfect slice profiles, or high-energy deposition. Single-slab 3D SE imaging was recently developed employing long echo trains with variable low flip angles to address these problems. However, long echo trains may yield suboptimal T(1)-weighted contrast, since T(2) weighting of the signals tends to develop along the echo train. Image blurring may also occur if high spatial frequency signals are acquired with low signal intensity. The purpose of this work was to develop an optimized T(1)-weighted version of single-slab 3D SE imaging with long echo trains. Refocusing flip angles were calculated based on a tissue-specific prescribed signal evolution. Spatially nonselective excitation was used, followed by half-Fourier acquisition in the in-plane phase encoding (PE) direction. Restore radio frequency (RF) pulses were applied at the end of the echo train to optimize T(1)-weighted contrast. Imaging parameters were optimized by using Bloch equation simulation, and imaging studies of healthy subjects were performed to investigate the feasibility of whole-brain imaging with isotropic, high spatial resolution. The proposed technique permitted highly-efficient T(1)-weighted 3D SE imaging of the brain.     

High resolution diffusion‐weighted imaging using readout‐segmented echo‐planar imaging,parallel imaging and a two‐dimensional navigator‐based reacquisition

Single‐shot echo‐planar imaging (EPI) is well established as the method of choice for clinical, diffusion‐weighted imaging with MRI because of its low sensitivity to the motion‐induced phase errors that occur during diffusion sensitization of the MR signal. However, the method is prone to artifacts due to susceptibility changes at tissue interfaces and has a limited spatial resolution. The introduction of parallel imaging techniques, such as GRAPPA (GeneRalized Autocalibrating Partially Parallel Acquisitions), has reduced these problems, but there are still significant limitations, particularly at higher field strengths, such as 3 Tesla (T), which are increasingly being used for routine clinical imaging. This study describes how the combination of readout‐segmented EPI and parallel imaging can be used to address these issues by generating high‐resolution, diffusion‐weighted images at 1.5T and 3T with a significant reduction in susceptibility artifact compared with the single‐shot case. The technique uses data from a 2D navigator acquisition to perform a nonlinear phase correction and to control the real‐time reacquisition of unusable data that cannot be corrected. Measurements on healthy volunteers demonstrate that this approach provides a robust correction for motion‐induced phase artifact and allows scan times that are suitable for routine clinical application. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Single‐shot multiecho parallel echo‐planar imaging (EPI) for diffusion tensor imaging (DTI) with improved signal‐to‐noise ratio (SNR) and reduced distortion

In this work, a multiecho parallel echo‐planar imaging (EPI) acquisition strategy is introduced as a way to improve the acquisition efficiency in parallel diffusion tensor imaging (DTI). With the use of an appropriate echo combination strategy, the sequence can provide signal‐to‐noise ratio (SNR) enhancement while maintaining the advantages of parallel EPI. Simulations and in vivo experiments demonstrate that a weighted summation of multiecho images provides a significant gain in SNR over the first echo image. It is experimentally demonstrated that this SNR gain can be utilized to reduce the number of measurements often required to ensure adequate SNR for accurate DTI measures. Furthermore, the multiple echoes can be used to derive a T₂ map, providing additional information that might be useful in some applications. Magn Reson Med 60:1512–1517, 2008. © 2008 Wiley‐Liss, Inc.     

High-resolution 7T MRI of the human hippocampus in vivo

Purpose

To describe an initial experience imaging the human hippocampus in vivo using a 7T magnetic resonance (MR) scanner and a protocol developed for very high field neuroimaging.

Materials and Methods

Six normal subjects were scanned on a 7T whole body MR scanner equipped with a 16‐channel head coil. Sequences included a full field of view T1‐weighted 3D turbo field echo (T1W 3D TFE: time of acquisition (TA) = 08:58), T2*‐weighted 2D fast field echo (T2*W 2D FFE: TA = 05:20), and susceptibility‐weighted imaging (SWI: TA = 04:20). SWI data were postprocessed using a minimum intensity projection (minIP) algorithm. Total imaging time was 23 minutes.

Results

T1W 3D TFE images with 700 μm isotropic voxels provided excellent anatomic depiction of macroscopic hippocampal structures. T2*W 2D FFE images with 0.5 mm in‐plane resolution and 2.5 mm slice thickness provided clear discrimination of the Cornu Ammonis and the compilation of adjacent sublayers of the hippocampus. SWI images (0.5 mm in‐plane resolution, 1.0 mm slice thickness) delineated microvenous anatomy of the hippocampus.

Conclusion

In vivo 7T MR imaging can take advantage of higher signal‐to‐noise and novel contrast mechanisms to provide increased conspicuity of hippocampal anatomy. J. Magn. Reson. Imaging 2008;28:1266–1272. © 2008 Wiley‐Liss, Inc.     

High‐resolution diffusion tensor imaging with inner field‐of‐view EPI

Purpose

To demonstrate the applicability of inner field‐of‐view (FOV) echo‐planar imaging based on spatially two‐dimensional selective radiofrequency excitations to high‐resolution diffusion tensor imaging.

Materials and Methods

Diffusion tensor imaging of inner FOVs with in‐plane resolutions of 0.90 × 0.90 mm² and 0.50 × 0.50 mm² was performed in the human brain and cervical spinal cord on a 3 T whole‐body MR system.

Results

Using inner FOVs reduces geometric distortions in echo‐planar imaging and allows for an improved in‐plane resolution. Some of the crossings of transverse pontine fibers with the pyramidal tracts in the brainstem could be resolved, increased diffusion anisotropy and fiber orientation could be identified in cerebellar white matter, and the reduced diffusion anisotropy of spinal cord gray matter could be detected.

Conclusion

Inner FOV echo‐planar imaging may help to improve the spatial resolution and thus the accuracy of diffusion anisotropy and white matter fiber orientation measurements in the human central nervous system. J. Magn. Reson. Imaging 2009;29:987–993. © 2009 Wiley‐Liss, Inc.     

Application of parallel imaging to fMRI at 7 Tesla utilizing a high 1D reduction factor.

Gradient-echo EPI, blood oxygenation level-dependent (BOLD) functional MRI (fMRI) using parallel imaging (PI) is demonstrated at 7 Tesla with 16 channels, a fourfold 1D reduction factor (R), and fourfold maximal aliasing. The resultant activation detection in finger-tapping fMRI studies was robust, in full agreement with expected activation patterns based on prior knowledge, and with functional maps generated from full field of view (FOV) coverage of k-space using segmented acquisition. In all aspects the functional maps acquired with PI outperformed segmented coverage of full k-space. With a 1D R of 4, fMRI activation based on PI had higher statistical significance, up to 1.6-fold in an individual case and 1.25+/-.25 (SD) fold when averaged over six studies, compared to four-segment/full-FOV data in which the square root R reduction in the image signal-to-noise ratio (SNR) due to k-space undersampling was compensated for by acquiring additional repetitions of the undersampled k-space. When this compensation for loss in SNR was not performed, the effect of PI was determined by the ratio of physiologically induced vs. intrinsic (thermal) noise in the fMRI time series and the extent to which physiological "noise" was amplified by the use of segmentation in the full-FOV data. The results demonstrate that PI is particularly beneficial at this ultrahigh field strength, where both the intrinsic image SNR and temporal signal fluctuations due to physiological processes are large.     

Three‐dimensional biexponential weighted 23Na imaging of the human brain with higher SNR and shorter acquisition time

A new method is presented for acquiring 3D biexponential weighted sodium images of the in vivo human brain with up to three times higher signal‐to‐noise ratio compared with conventional six‐step phase‐cycling triple‐quantum‐filtered imaging. To excite and detect multiple‐quantum coherences, a three‐pulse preparation is used. During the pulse train, two images are obtained. The first image is acquired with ultrashort echo time (0.3 ms) during preparation between the first two pulses to yield a spin‐density‐weighted image. After the last pulse, a single‐quantum‐filtered image is acquired with an echo time of 11 ms that maximizes the resulting signal. The biexponential weighted image is calculated by subtracting the single‐quantum‐filtered image from the spin‐density‐weighted image. The resulting image mainly shows signal from sodium ions with biexponential quadrupolar relaxation behavior. In isotropic environments, the resulting image mainly contains triple‐quantum‐filtered signal. The four‐step phase cycling yields similar signal‐to‐noise ratio in shorter acquisition time compared with six‐step phase‐cycling biexponential weighted imaging. Magn Reson Med 70:754–765, 2013. © 2012 Wiley Periodicals, Inc.     

Improving the performance of diffusion-weighted inner field-of-view echo-planar imaging based on 2D-selective radiofrequency excitations by tilting the excitation plane

Purpose:

To improve the performance and flexibility of diffusion‐weighted inner field‐of‐view (FOV) echo‐planar imaging (EPI) based on 2D‐selective radiofrequency (RF) excitations by 1) using higher gradient amplitudes for outer excitation lines, and 2) tilting the excitation plane such that the unwanted side excitations do not overlap with the current image slice or other slices to be acquired.

Materials and Methods:

Acquisitions with a conventional (untilted) and the improved setup were compared and inner FOV diffusion tensor measurements were performed in the human brain and spinal cord with voxel sizes of 1.0 × 1.0 × 5.0 mm³ and 0.6 × 0.6 × 5.0 mm³ on a 3 T whole‐body magnetic resonance imaging (MRI) system.

Results:

With the modified setup, the 2D‐selective RF excitations can be considerably shortened (e.g., from 26 msec to 6 msec) which 1) avoids profile distortions in the presence of magnetic field inhomogeneities, and 2) reduces the required echo time and increases the signal‐to‐noise ratio accordingly, e.g., by about 20% in the spinal cord.

Conclusion:

Tilting the excitation plane and applying variable gradient amplitudes improves the applicability of inner FOV EPI based on 2D‐selective RF excitations. J. Magn. Reson. Imaging 2012;35:984–992. © 2011 Wiley Periodicals, Inc.     

A Modified EPI sequence for high‐resolution imaging at ultra‐short echo time

A robust modification of echo‐planar imaging dubbed double‐shot echo‐planar imaging with center‐out trajectories and intrinsic navigation (DEPICTING) is proposed, which permits imaging at ultra‐short echo time. The k‐space data is sampled by two center‐out trajectories with a minimal delay achieving a temporal efficiency similar to conventional single‐shot echo‐planar imaging. Intersegment phase and intensity imperfections are corrected by exploiting the intrinsic navigator information from both central lines, which are subsequently averaged for image reconstruction. Phase errors induced by inhomogeneities of the main magnetic field are corrected in k‐space, recovering the superior point‐spread function achieved with center‐out trajectories. The minimal echo time (<2 msec) is nearly independent of the acquisition matrix permitting applications, which simultaneously require high spatial and temporal resolution. Examples of demonstrated applications include anatomical imaging, BOLD‐based functional brain mapping, and quantitative perfusion imaging. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

3D fast spin echo with out‐of‐slab cancellation: A technique for high‐resolution structural imaging of trabecular bone at 7 tesla

Spin‐echo‐based pulse sequences are desirable for the application of high‐resolution imaging of trabecular bone but tend to involve high‐power deposition. Increased availability of ultrahigh field scanners has opened new possibilities for imaging with increased signal‐to‐noise ratio (SNR) efficiency, but many pulse sequences that are standard at 1.5 and 3 T exceed specific absorption rate limits at 7 T. A modified, reduced specific absorption rate, three‐dimensional, fast spin‐echo pulse sequence optimized specifically for in vivo trabecular bone imaging at 7 T is introduced. The sequence involves a slab‐selective excitation pulse, low‐power nonselective refocusing pulses, and phase cycling to cancel undesired out‐of‐slab signal. In vivo images of the distal tibia were acquired using the technique at 1.5, 3, and 7 T field strengths, and SNR was found to increase at least linearly using receive coils of identical geometry. Signal dependence on the choice of refocusing flip angles in the echo train was analyzed experimentally and theoretically by combining the signal from hundreds of coherence pathways, and it is shown that a significant specific absorption rate reduction can be achieved with negligible SNR loss. Magn Reson Med 63:719–727, 2010. © 2010 Wiley‐Liss, Inc.     

Two-dimensional spatially-selective RF excitation pulses in echo-planar imaging.

Two-dimensional spatially-selective RF (2DRF) excitation pulses were developed for single-shot echo-planar imaging (EPI) with reduced field of view (FOV) in the phase-encoding direction. The decreased number of k-space lines significantly shortens the length of the EPI echo train. Thus, both gradient-echo and spin-echo 2DRF-EPI images of the human brain at 2.0 T exhibit markedly reduced susceptibility artifacts in regions close to major air cavities. Based on a blipped-planar trajectory, implementation of a typical 2DRF pulse resulted in a 26-ms pulse duration, a 5-mm section thickness, a 40-mm FOV along the phase-encoding direction, and a 200-mm distance of the unavoidable side excitations from the center of the FOV. For the above conditions and at 2 x 2 mm(2) resolution, 2DRF-EPI yielded an echo train length of only 21 ms, as opposed to 102 ms for conventional EPI. This gain in time may be used to achieve higher spatial resolution. For example, spin-echo 2DRF-EPI of a 40-mm FOV at 1 x 1 mm(2) resolution led to an echo train of 66 ms. Although the current implementation still lacks user-friendliness, 2DRF pulses are likely to become a useful addition to the arsenal of advanced MRI tools. .     

Parallel imaging with asymmetric acceleration to reduce Gibbs artifacts and to increase signal‐to‐noise ratio of the gradient echo echo‐planar imaging sequence for functional MRI

Parallel imaging with accelerated acquisition was noted to pronounce Gibbs artifacts which appear as ripples propagated in the phase‐encoding (PE) direction near the susceptibility‐affected region in echo‐planar imaging (EPI). Using the extended EPI sequence, which collected extended readouts outside the regular data sampling time, the pronounced Gibbs artifact was analyzed and found to be caused by an increased echo shift in the pre‐echo time (T_E) of accelerated parallel imaging. This was also confirmed by theoretical derivation of the echo shift caused by the inplane susceptibility gradient in the PE direction (ISG_PE). A new EPI sequence was developed to reduce the Gibbs artifact and to restore the signal level toward that of nonaccelerated parallel imaging by asymmetrically accelerating only the post‐T_E sampling time and by using the extended EPI in the pre‐T_E. The nonaccelerated portion in the pre‐T_E used the delay for the optimum blood oxygen level dependent (BOLD) sensitivity at 3 T, maintaining the same slice coverage as the symmetrical acceleration in both pre‐T_E and post‐T_E. The increased data sampling points resulted in an increase of the signal‐to‐noise ratio (SNR). The restored signal and enhanced SNR of the proposed method were confirmed to deliver a better BOLD functional MRI (fMRI) result in the breath holding experiment. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc.     

Sinusoidal echo-planar imaging with parallel acquisition technique for reduced acoustic noise in auditory fMRI

Purpose:

To extend the parameter restrictions of a silent echo‐planar imaging (sEPI) sequence using sinusoidal readout (RO) gradients, in particular with increased spatial resolution. The sound pressure level (SPL) of the most feasible configurations is compared to conventional EPI having trapezoidal RO gradients.

Materials and Methods:

We enhanced the sEPI sequence by integrating a parallel acquisition technique (PAT) on a 3 T magnetic resonance imaging (MRI) system. The SPL was measured for matrix sizes of 64 × 64 and 128 × 128 pixels, without and with PAT (R = 2). The signal‐to‐noise ratio (SNR) was examined for both sinusoidal and trapezoidal RO gradients.

Results:

Compared to EPI PAT, the SPL could be reduced by up to 11.1 dB and 5.1 dB for matrix sizes of 64 × 64 and 128 × 128 pixels, respectively. The SNR of sinusoidal RO gradients is lower by a factor of 0.96 on average compared to trapezoidal RO gradients.

Conclusion:

The sEPI PAT sequence allows for 1) increased resolution, 2) expanded RO frequency range toward lower frequencies, which is in general beneficial for SPL, or 3) shortened TE, TR, and RO train length. At the same time, it generates lower SPL compared to conventional EPI for a wide range of RO frequencies while having the same imaging parameters. J. Magn. Reson. Imaging 2012;36:581–588. © 2012 Wiley Periodicals, Inc.     

Accelerating time‐resolved MRA with multiecho acquisition

A new four‐dimensional magnetic resonance angiograpy (MRA) technique called contrast‐enhanced angiography with multiecho and radial k‐space is introduced, which accelerates the acquisition using multiecho while maintaining a high spatial resolution and increasing the signal‐to‐noise ratio (SNR). An acceleration factor of approximately 2 is achieved without parallel imaging or undersampling by multiecho (i.e., echo‐planar imaging) acquisition. SNR is gained from (1) longer pulse repetition times, which allow more time for T₁ regrowth; (2) decreased specific absorption rate, which allows use of flip angles that maximize contrast at high field; and (3) minimized effects of a transient contrast bolus signal with a shorter temporal footprint. Simulations, phantom studies, and in vivo scans were performed. Contrast‐enhanced angiography with multiecho and radial k‐space can be combined with parallel imaging techniques such as Generalized Autocalibrating Partially Parallel Acquisitions (GRAPPA) to provide additional 2‐fold acceleration in addition to higher SNR to trade off for parallel imaging. This technique can be useful in diagnosing vascular lesions where accurate dynamic information is necessary. Magn Reson Med 63:1520–1528, 2010. © 2010 Wiley‐Liss, Inc.     

Fast diffusion tensor imaging and tractography of the whole cervical spinal cord using point spread function corrected echo planar imaging

Diffusion tensor imaging has been used in a number of spinal cord studies, but severe distortions caused by susceptibility induced field inhomogeneities limit its applicability to investigate small volumes within acceptable acquisition times. A way to evaluate image distortions is to map the point spread function of the voxel intensity in a reference scan. In this study, the point spread function was mapped for an echo‐planar imaging sequence in the human cervical spinal cord with isotropic resolution and large field of view. Correction with the point spread function map improved anatomical consistency, and full cervical tractography was thereby possible from a C1 seed region in healthy controls and one individual with spinal cord injury. It is suggested that point spread function mapping of the spinal cord can be used in combination with sequence‐based methods for reduction of susceptibility artifacts or in high‐field imaging settings where off‐resonance effects are pronounced. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.