Estimation of k‐space trajectories in spiral MRI

For non‐Cartesian data acquisition in MRI, k‐space trajectory infidelity due to eddy current effects and other hardware imperfections will blur and distort the reconstructed images. Even with the shielded gradients and eddy current compensation techniques of current scanners, the deviation between the actual k‐space trajectory and the requested trajectory remains a major reason for image artifacts in non‐Cartesian MRI. It is often not practical to measure the k‐space trajectory for each imaging slice. It has been reported that better image quality is achieved in radial scanning by correcting anisotropic delays on different physical gradient axes. In this article the delay model is applied in spiral k‐space trajectory estimation to reduce image artifacts. Then a novel estimation method combining the anisotropic delay model and a simple convolution eddy current model further reduces the artifact level in spiral image reconstruction. The root mean square error and peak error in both phantom and in vivo images reconstructed using the estimated trajectories are reduced substantially compared to the results achieved by only tuning delays. After a one‐time calibration, it is thus possible to get an accurate estimate of the spiral trajectory and a high‐quality image reconstruction for an arbitrary scan plane. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Rapid PROPELLER‐MRI: A combination of iterative reconstruction and under‐sampling

Purpose:

To develop a technique that is able to reduce acquisition time and remove uneven blurring in reconstructed image for PROPELLER MRI. By using under‐sampling and iterative reconstruction, this proposed technique will be less sensitive to subject motion.

Materials and Methods:

Numerical simulations, as well as experiments on a phantom and healthy human subjects were performed to demonstrate advantages of a combination of under‐sampled acquisition and iterative reconstruction. Method of motion correction was modified to increase accuracy of motion correction for the under‐sampled PROPELLER acquisition.

Results:

It was demonstrated that the proposed approach achieved substantial acceleration of PROPELLER acquisition while maintaining its motion correction advantage.

Conclusion:

An effective method for reducing imaging time in PROPELLER was introduced in this study, which minimizes typical under‐sampling artifacts without uneven spatial resolution and maintains the ability of motion correction. J. Magn. Reson. Imaging 2012;36:1241–1247. © 2012 Wiley Periodicals, Inc.     

A parallel imaging technique using mutual calibration for split‐blade diffusion‐weighted PROPELLER

Split‐blade diffusion‐weighted periodically rotated overlapping parallel lines with enhanced reconstruction (DW‐PROPELLER) was proposed to address the issues associated with diffusion‐weighted echo planar imaging such as geometric distortion and difficulty in high‐resolution imaging. The major drawbacks with DW‐PROPELLER are its high SAR (especially at 3T) and violation of the Carr‐Purcell‐Meiboom‐Gill condition, which leads to a long scan time and narrow blade. Parallel imaging can reduce scan time and increase blade width; however, it is very challenging to apply standard k‐space‐based techniques such as GeneRalized Autocalibrating Partially Parallel Acquisitions (GRAPPA) to split‐blade DW‐PROPELLER due to its narrow blade. In this work, a new calibration scheme is proposed for k‐space‐based parallel imaging method without the need of additional calibration data, which results in a wider, more stable blade. The in vivo results show that this technique is very promising. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.     

Intraprocedural diffusion‐weighted PROPELLER MRI to guide percutaneous biopsy needle placement within rabbit VX2 liver tumors

Purpose

To test the hypothesis that diffusion‐weighted (DW)‐PROPELLER (periodically rotated overlapping parallel lines with enhanced reconstruction) magnetic resonance imaging (MRI) can be used to guide biopsy needle placement during percutaneous interventional procedures to selectively target viable and necrotic tissues within VX2 rabbit liver tumors.

Materials and Methods

Our institutional Animal Care and Use Committee approved all experiments. In six rabbits implanted with 15 VX2 liver tumors, baseline DW‐PROPELLER images acquired prior to the interventional procedure were used for apparent diffusion coefficient (ADC) measurements. Next, intraprocedural DW‐PROPELLER scans were performed with needle position iteratively adjusted to target viable, necrotic, or intermediate border tissue regions. DW‐PROPELLER ADC measurements at the selected needle tip locations were compared with the percentage of tumor necrosis qualitatively assessed at histopathology.

Results

DW‐PROPELLER images demonstrated intratumoral tissue heterogeneity and clearly depicted the needle tip position within viable and necrotic tumor tissues. Mean ADC measurements within the region‐of‐interest encompassing the needle tip were highly correlated with histopathologic tumor necrotic tissue assessments.

Conclusion

DW‐PROPELLER is an effective method to selectively position the biopsy needle tip within viable and necrotic tumor tissues. The DW‐PROPELLER method may offer an important complementary tool for functional guidance during MR‐guided percutaneous procedures. J. Magn. Reson. Imaging 2009;30:366–373. © 2009 Wiley‐Liss, Inc.     

Reduced field‐of‐view single‐shot fast spin echo imaging using two‐dimensional spatially selective radiofrequency pulses

Purpose:

To demonstrate reduced field‐of‐view (RFOV) single‐shot fast spin echo (SS‐FSE) imaging based on the use of two‐dimensional spatially selective radiofrequency (2DRF) pulses.

Materials and Methods:

The 2DRF pulses were incorporated into an SS‐FSE sequence for RFOV imaging in both phantoms and the human brain on a 1.5 Tesla (T) whole‐body MR system with the aim of demonstrating improvements in terms of shorter scan time, reduced blurring, and higher spatial resolution compared with full FOV imaging.

Results:

For phantom studies, scan time gains of up to 4.2‐fold were achieved as compared to the full FOV imaging. For human studies, the spatial resolution was increased by a factor of 2.5 (from 1.7 mm/pixel to 0.69 mm/pixel) for RFOV imaging within a scan time (0.7 s) similar to full FOV imaging. A 2.2‐fold shorter scan time along with a significant reduction of blurring was demonstrated in RFOV images compared with full FOV images for a target spatial resolution of 0.69 mm/pixel.

Conclusion:

RFOV SS‐FSE imaging using a 2DRF pulse shows advantages in scan time, blurring, and specific absorption rate reduction along with true spatial resolution increase compared with full FOV imaging. This approach is promising to benefit fast imaging applications such as image guided therapy. J. Magn. Reson. Imaging 2010;32:242–248. © 2010 Wiley‐Liss, Inc.     

Modified PROPELLER approach for T2‐mapping of the abdomen

Quantitative abdominal T₂ measurements may be useful for lesion differentiation and functional tissue characterization. However, T₂ mapping of the abdomen with conventional spin‐echo (SE) and turbo‐spin‐echo (TSE) approaches can be challenging due to physiologic motion artifacts. Multishot TSE‐based PROPELLER (Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction) can provide superior image quality due to reduced sensitivity to motion artifacts. With echo‐reordering to accurately estimate effective echo times and an extended slice thickness ratio to reduce stimulated echo effects, a modified PROPELLER approach may permit accurate, robust abdominal T₂ measurements. We validated the accuracy of our modified PROPELLER T₂‐mapping approach by comparison to conventional SE measurements in a phantom model and demonstrated the feasibility of acquiring accurate, high‐quality abdominal T₂ maps in normal volunteers. Magn Reson Med 61:1269–1278, 2009. © 2009 Wiley‐Liss, Inc.     

Improving non‐contrast‐enhanced steady‐state free precession angiography with compressed sensing

Flow‐independent angiography offers the ability to produce vessel images without contrast agents. Angiograms are acquired with magnetization‐prepared three‐dimensional balanced steady‐state free precession sequences, where the phase encodes are interleaved and the preparation is repeated before each interleaf. The frequent repetition of the preparation significantly decreases the scan efficiency. The number of excitations can instead be reduced with compressed sensing by exploiting the compressibility of the angiograms. Hence, the phase encodes can be undersampled to save scan time without significantly degrading image quality. These savings can be allotted for preparing the magnetization more often, or alternatively, improving resolution. The enhanced resolution and contrast achieved with the proposed method are demonstrated with lower leg angiograms. Depiction of the vasculature is significantly improved with the increased resolution in the phase‐encode plane and higher blood‐to‐background contrast. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

PROPELLER EPI: an MRI technique suitable for diffusion tensor imaging at high field strength with reduced geometric distortions.

A technique suitable for diffusion tensor imaging (DTI) at high field strengths is presented in this work. The method is based on a periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) k-space trajectory using EPI as the signal readout module, and hence is dubbed PROPELLER EPI. The implementation of PROPELLER EPI included a series of correction schemes to reduce possible errors associated with the intrinsically higher sensitivity of EPI to off-resonance effects. Experimental results on a 3.0 Tesla MR system showed that the PROPELLER EPI images exhibit substantially reduced geometric distortions compared with single-shot EPI, at a much lower RF specific absorption rate (SAR) than the original version of the PROPELLER fast spin-echo (FSE) technique. For DTI, the self-navigated phase-correction capability of the PROPELLER EPI sequence was shown to be effective for in vivo imaging. A higher signal-to-noise ratio (SNR) compared to single-shot EPI at an identical total scan time was achieved, which is advantageous for routine DTI applications in clinical practice.     

3D magnetization‐prepared imaging using a stack‐of‐rings trajectory

Efficient acquisition strategies for magnetization‐prepared imaging based on the three‐dimensional (3D) stack‐of‐rings k‐space trajectory are presented in this work. The 3D stack‐of‐rings can be acquired with centric ordering in all three dimensions for greater efficiency in capturing the desired contrast. In addition, the 3D stack‐of‐rings naturally supports spherical coverage in k‐space for shorter scan times while achieving isotropic spatial resolution. While non‐Cartesian trajectories generally suffer from greater sensitivity to system imperfections, the 3D stack‐of‐rings can enhance magnetization‐prepared imaging with a high degree of robustness to timing delays and off‐resonance effects. As demonstrated with phantom scans, timing errors and gradient delays only cause a bulk rotation of the 3D stack‐of‐rings reconstruction. Furthermore, each ring can be acquired with a time‐efficient retracing design to resolve field inhomogeneities and enable fat/water separation. To demonstrate its effectiveness, the 3D stack‐of‐rings are considered for the case of inversion‐recovery‐prepared structural brain imaging. Experimental results show that the 3D stack‐of‐rings can achieve higher signal‐to‐noise ratio and higher contrast‐to‐noise ratio within a shorter scan time when compared to the standard inversion‐recovery‐prepared sequence based on 3D Cartesian encoding. The design principles used for this specific case of inversion‐recovery‐prepared brain imaging can be applied to other magnetization‐prepared imaging applications. Magn Reson Med 63:1210–1218, 2010. © 2010 Wiley‐Liss, Inc.     

High‐resolution magnetic resonance angiography in the mouse using a nanoparticle blood‐pool contrast agent

High‐resolution magnetic resonance angiography is already a useful tool for studying mouse models of human disease. Magnetic resonance angiography in the mouse is typically performed using time‐of‐flight contrast. In this work, a new long‐circulating blood‐pool contrast agent—a liposomal nanoparticle with surface‐conjugated gadolinium (SC‐Gd liposomes)—was evaluated for use in mouse neurovascular magnetic resonance angiography. A total of 12 mice were imaged. Scan parameters were optimized for both time‐of‐flight and SC‐Gd contrast. Compared to time‐of‐flight contrast, SC‐Gd liposomes (0.08 mmol/kg) enabled improved small‐vessel contrast‐to‐noise ratio, larger field of view, shorter scan time, and imaging of venous structures. For a limited field of view, time‐of‐flight and SC‐Gd were not significantly different; however, SC‐Gd provided better contrast‐to‐noise ratio when the field of view encompassed the whole brain (P < 0.001) or the whole neurovascular axis (P < 0.001). SC‐Gd allowed acquisition of high‐resolution magnetic resonance angiography (52 × 52 × 100 micrometer³ or 0.27 nL), with 123% higher (P < 0.001) contrast‐to‐noise ratio in comparable scan time (～45 min). Alternatively, SC‐Gd liposomes could be used to acquire high‐resolution magnetic resonance angiography (0.27 nL) with 32% higher contrast‐to‐noise ratio (P < 0.001) in 75% shorter scan time (12 min). Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Spatially 2D‐selective RF excitations using the PROPELLER trajectory: Basic principles and application to MR spectroscopy of irregularly shaped single voxel

Spatially two‐dimensional selective radio frequency (2DRF) excitations are able to excite arbitrarily‐shaped profiles in their excitation plane and, hence, can be used to minimize partial volume effects in single‐voxel magnetic resonance spectroscopy. In this study, 2DRF excitations based on the PROPELLER trajectory which consists of blades of parallel lines that are rotated against each other, are presented. Because the k‐space center is covered with each segment, the trajectory yields a high signal efficiency which, e.g., is considerably improved compared to a segmented blipped‐planar approach. It is shown that a sampling density correction based on the PROPELLER trajectory's Voronoi diagram suppresses unwanted side excitations. Off‐resonance effects like chemical‐shift displacement artifacts, can be minimized by applying nonselective refocusing radio frequency pulses between the lines of a blade. With half‐Fourier segments, the 2DRF's echo time contribution can be shortened considerably. Thus, robust 2DRF excitations capable of exciting high‐resolution profiles at short echo times with high signal efficiency are obtained. Their applicability to MR spectroscopy of an arbitrarily‐shaped single voxel is demonstrated in a two‐bottle phantom and in the human brain in vivo on a 3 T whole‐body MR system. Magn Reson Med, 2011. © 2011 Wiley Periodicals, Inc.     

X‐PROP: A fast and robust diffusion‐weighted propeller technique

Diffusion‐weighted imaging (DWI) has shown great benefits in clinical MR exams. However, current DWI techniques have shortcomings of sensitivity to distortion or long scan times or combinations of the two. Diffusion‐weighted echo‐planar imaging (EPI) is fast but suffers from severe geometric distortion. Periodically rotated overlapping parallel lines with enhanced reconstruction diffusion‐weighted imaging (PROPELLER DWI) is free of geometric distortion, but the scan time is usually long and imposes high Specific Absorption Rate (SAR) especially at high fields. TurboPROP was proposed to accelerate the scan by combining signal from gradient echoes, but the off‐resonance artifacts from gradient echoes can still degrade the image quality. In this study, a new method called X‐PROP is presented. Similar to TurboPROP, it uses gradient echoes to reduce the scan time. By separating the gradient and spin echoes into individual blades and removing the off‐resonance phase, the off‐resonance artifacts in X‐PROP are minimized. Special reconstruction processes are applied on these blades to correct for the motion artifacts. In vivo results show its advantages over EPI, PROPELLER DWI, and TurboPROP techniques. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

High‐resolution diffusion tensor imaging of the human pons with a reduced field‐of‐view,multishot, variable‐density,spiral acquisition at 3 T

Diffusion tensor imaging of localized anatomic regions, such as brainstem, cervical spinal cord, and optic nerve, is challenging because of the existence of significant susceptibility differences, severe physiologic motion in the surrounding tissues, and the need for high spatial resolution to resolve the underlying complex neuroarchitecture. The aim of the methodology presented here is to achieve high‐resolution diffusion tensor imaging in localized regions of the central nervous system that is motion insensitive and immune to susceptibility while acquiring a set of two‐dimensional images with more than six diffusion encoding directions within a reasonable total scan time. We accomplish this aim by implementing self‐navigated, multishot, variable‐density, spiral encoding with outer volume suppression. We establish scan protocols for achieving equal signal‐to‐noise ratio at 1.2 mm and 0.8 mm in‐plane resolution for reduced field‐of‐view diffusion tensor imaging of the brainstem. In vivo application of the technique on the human pons of three subjects shows a clear delineation of the multiple local neural tracts. By comparing scans acquired with varying in‐plane resolution but with constant signal‐to‐noise ratio, we demonstrate that increasing the resolution and reducing the partial volume effect result in higher fractional anisotropy values for the corticospinal tracts. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Turboprop+: Enhanced turboprop diffusion‐weighted imaging with a new phase correction

Faster periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) diffusion‐weighted imaging acquisitions, such as Turboprop and X‐prop, remain subject to phase errors inherent to a gradient echo readout, which ultimately limits the applied turbo factor (number of gradient echoes between each pair of radiofrequency refocusing pulses) and, thus, scan time reductions. This study introduces a new phase correction to Turboprop, called Turboprop+. This technique employs calibration blades, which generate 2‐D phase error maps and are rotated in accordance with the data blades, to correct phase errors arising from off‐resonance and system imperfections. The results demonstrate that with a small increase in scan time for collecting calibration blades, Turboprop+ had a superior immunity to the off‐resonance‐related artifacts when compared to standard Turboprop and recently proposed X‐prop with the high turbo factor (turbo factor = 7). Thus, low specific absorption rate and short scan time can be achieved in Turboprop+ using a high turbo factor, whereas off‐resonance related artifacts are minimized. Magn Reson Med 70:497–503, 2013. © 2012 Wiley Periodicals, Inc.     

Half‐fourier‐acquisition single‐shot turbo spin‐echo (HASTE) MRI of the lung at 3 Tesla using parallel imaging with 32‐receiver channel technology

Purpose

To assess the feasibility of half‐Fourier‐acquisition single‐shot turbo spin‐echo (HASTE) of the lung at 3 Tesla (T) using parallel imaging with a prototype of a 32‐channel torso array coil, and to determine the optimum acceleration factor for the delineation of intrapulmonary anatomy.

Materials and Methods

Nine volunteers were examined on a 32‐channel 3T MRI system using a prototype 32‐channel‐torso‐array‐coil. HASTE‐MRI of the lung was acquired at both, end‐inspiratory and end‐expiratory breathhold with parallel imaging (Generalized autocalibrating partially parallel acquisitions = GRAPPA) using acceleration factors ranging between R = 1 (TE = 42 ms) and R = 6 (TE = 16 ms). The image quality of intrapulmonary anatomy and subjectively perceived noise level was analyzed by two radiologists in consensus. In addition quantitative measurements of the signal‐to‐noise ratio (SNR) of HASTE with different acceleration factors were assessed in phantom measurements.

Results

Using an acceleration factor of R = 4 image blurring was substantially reduced compared with lower acceleration factors resulting in sharp delineation of intrapulmonary structures in expiratory scans. For inspiratory scans an acceleration factor of 2 provided the best image quality. Expiratory scans had a higher subjectively perceived SNR than inspiratory scans.

Conclusion

Using optimized multi‐element coil geometry HASTE‐MRI of the lung is feasible at 3T with acceleration factors up to 4. Compared with nonaccelerated acquisitions, shorter echo times and reduced image blurring are achieved. Expiratory scanning may be favorable to compensate for susceptibility associated signal loss at 3T. J. Magn. Reson. Imaging 2009;30:541–546. © 2009 Wiley‐Liss, Inc.     

Contrast‐enhanced intracranial magnetic resonance angiography with a spherical shells trajectory and online gridding reconstruction

Purpose:

To evaluate the feasibility of applying the shells trajectory to single‐phase contrast‐enhanced magnetic resonance angiography.

Materials and Methods:

Several methods were developed to overcome the challenges of the clinical implementation of shells including off‐resonance blurring (eg, from lipid signal), aliasing artifacts, and long reconstruction times. These methods included: 1) variable TR with variable readout length to reduce fat signal and off‐resonance blurring; 2) variable sampling density to suppress aliasing artifacts while minimizing acquisition time penalty; and 3) an online 3D gridding algorithm that reconstructed an 8‐channel, 240³ image volume set. Both phantom and human studies were performed to establish the initial feasibility of the methods.

Results:

Phantom and human study results demonstrated the effectiveness of the proposed methods. Shells with variable TR and readout length further suppressed the fat signal compared to the fixed‐TR shells acquisition. Reduced image aliasing was achieved with minimal scan time penalty when a variable sampling density technique was used. The fast online reconstruction algorithm completed in 2 minutes at the scanner console, providing a timely image display in a clinical setting.

Conclusion:

It was demonstrated that the use of the shells trajectory is feasible in a clinical setting to acquire intracranial angiograms with high spatial resolution. Preliminary results demonstrate effective venous suppression in the cavernous sinuses and jugular vein region. J. Magn. Reson. Imaging 2009;30:1101–1109. © 2009 Wiley‐Liss, Inc.     

Motion corrected intracranial MRA using PROPELLER with RF quadratic encoding

A new motion corrected Time‐of‐Flight MRA technique named Variable Pitch PROPELLER is presented. This technique employs the PROPELLER acquisition and reconstruction scheme for in‐plane bulk motion correction. A non‐ Fourier through‐plane encoding mechanism called quadratic encoding boosts SNR, relative to conventional 2D MRA, in lieu of traditional 3D encoding. Partial Fourier encoding is applied in the slice direction for a further reduction in scan time. This work details the construction and optimization of this technique. VPPROP MRAs are compared with a clinical MOTSA protocol. Initial results show promising robustness to bulk motion effects. The comparisons with MOTSA provide insight as to the additions required to create a comparable scan. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

A three‐dimensional variable‐density spiral spatial‐spectral RF pulse with rotated gradients

Three‐dimensional spatial‐spectral radiofrequency pulses using a stack‐of‐spirals trajectory can achieve two‐dimensional spatial localization and one‐dimensional spectral selection simultaneously. These pulses are useful, for example, in reduced field‐of‐view applications that also require frequency specificity such as lipid imaging. A limitation of the pulse design is that the length of the spiral trajectory is fixed by the frequency separation of lipid and water. This restricts the highest possible excitation resolution of the spatial profile over a given field of excitation. In this work, we examine the use of periodically rotated variable‐density spirals to increase the spatial excitation resolution without changing the frequency selectivity. Variable‐density spirals are used to undersample the high spatial frequencies such that higher excitation resolutions can be obtained with a small expense in increased aliasing of the slice profile. The periodic rotation of the spiral trajectories reduces the impact of the undersampling by distributing the aliasing in the frequency domain. The technique is demonstrated with simulations, phantom studies, and imaging human leg muscle at 3 T. It was found in the human study that the spatial excitation resolution could be improved from 6 × 6 to 8 × 8 (matrix size over a fixed field of view) while decreasing aliasing by approximately 40‐60%. Magn Reson Med 63:828–834, 2010. © 2010 Wiley‐Liss, Inc.     

Whole‐heart contrast‐enhanced coronary magnetic resonance angiography using gradient echo interleaved EPI

Whole‐heart coronary MR angiography (MRA) is a promising method for detecting coronary artery disease. However, the imaging time is relatively long (on the order of 10–15 min). Such a long imaging time may result in patient discomfort and compromise the robustness of whole‐heart coronary MRA due to increased respiratory and cardiac motion artifacts. The goal of this study was to optimize a gradient echo interleaved echo planar imaging (GRE‐EPI) acquisition scheme for reducing the imaging time of contrast‐enhanced whole‐heart coronary MRA. Numerical simulations and phantom studies were used to optimize the GRE‐EPI sequence parameters. Healthy volunteers were scanned with both the proposed GRE‐EPI sequence and a 3D TrueFISP sequence for comparison purposes. Slow infusion (0.5 cc/sec) of Gd‐DTPA was used to enhance the signal‐to‐noise ratio (SNR) of the GRE‐EPI acquisition. Whole‐heart images with the GRE‐EPI technique were acquired with a true resolution of 1.0 × 1.1 × 2.0 mm³ in an average scan time of 4.7 ± 0.7 min with an average navigator efficiency of 44 ± 6%. The GRE‐EPI acquisition showed excellent delineation of all the major coronary arteries with scan time reduced by a factor of 2 compared with the TrueFISP acquisition. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Motion correction in periodically‐rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) and turboprop MRI

Periodically‐rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) and Turboprop MRI are characterized by greatly reduced sensitivity to motion, compared to their predecessors, fast spin‐echo (FSE) and gradient and spin‐echo (GRASE), respectively. This is due to the inherent self‐navigation and motion correction of PROPELLER‐based techniques. However, it is unknown how various acquisition parameters that determine k‐space sampling affect the accuracy of motion correction in PROPELLER and Turboprop MRI. The goal of this work was to evaluate the accuracy of motion correction in both techniques, to identify an optimal rotation correction approach, and determine acquisition strategies for optimal motion correction. It was demonstrated that blades with multiple lines allow more accurate estimation of motion than blades with fewer lines. Also, it was shown that Turboprop MRI is less sensitive to motion than PROPELLER. Furthermore, it was demonstrated that the number of blades does not significantly affect motion correction. Finally, clinically appropriate acquisition strategies that optimize motion correction are discussed for PROPELLER and Turboprop MRI. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.