Spoiling of transverse magnetization in gradient-echo (GRE) imaging during the approach to steady state

The signal evolution behaviors and corresponding image appearances for different methods of spoiling or refocusing the transverse magnetization in short TR gradient-echo imaging during the approach to steady state were investigated experimentally and using computer simulations based on the Bloch equations. Specifically, ideally spoiled, gradient-spoiled, gradient-refocused, and RF-spoiled pulse sequence configurations were studied. This study showed that, for the gradient-spoiled configuration, the signal evolution is position and phase-encoding order-dependent and, under typical imaging conditions, can deviate substantially from the ideally spoiled signal evolution at some spatial positions, resulting in intensity banding image artifacts. For the gradient-refocused configuration, the signal evolution oscillates toward the steady state and, generally, does not closely approximate that of ideal spoiling, resulting in different image contrast or image blurring. Using RF spoiling, the signal evolution closely approximates the ideally spoiled case for flip angles less than approximately 20° and T₂ values of less than approximately 200 ms and results in relatively artifact-free images. Also, this study showed that, for RF spoiling, an RF-pulse phase-difference increment other than 117°, such as 84°, may be optimal for gradient-echo imaging during the approach to steady state.     

On the steady‐state properties of actual flip angle imaging (AFI)

AFI (actual flip angle imaging) represents an interesting approach to map the B₁ transmit fields by measuring the spatial variations of the effective flip angle. However, the accuracy of the technique relies on the adequate spoiling of transverse magnetization. In the present work configuration theory was employed to develop a proper RF and gradient spoiling scheme for the AFI technique, making the sequence robust against off‐resonance without the need of large spoiling gradients. Furthermore, numerical simulations were performed to predict the steady‐state signals and, hence, the accuracy of the AFI technique as a function of the sequence and tissue parameters. It is shown that the spoiling properties of the sequence are mainly defined by the phase shift increment ? of the RF pulses and the diffusion sensitivity resulting from the unbalanced gradients of the sequence. Adequate spoiling may be achieved for a reasonable range of tissue parameters and flip angles for moderate spoiling gradients if a favorable value for ? is chosen. Phantom and in vivo head imaging experiments show an excellent agreement with the theoretical predictions, indicating that the proper operating range of the approach may be reliably predicted by the theory. Magn Reson Med 61:84–92, 2009. © 2008 Wiley‐Liss, Inc.     

Influence of RF spoiling on the stability and accuracy of T1 mapping based on spoiled FLASH with varying flip angles

There is increasing interest in quantitative T₁ mapping techniques for a variety of applications. Several methods for T₁ quantification have been described. The acquisition of two spoiled gradient‐echo data sets with different flip angles allows for the calculation of T₁ maps with a high spatial resolution and a relatively short experimental duration. However, the method requires complete spoiling of transverse magnetization. To achieve this goal, RF spoiling has to be applied. In this work it is investigated whether common RF spoiling techniques are sufficiently effective to allow for accurate T₁ quantification. It is shown that for most phase increments the apparent T₁ can deviate considerably from the true value. Correct results may be achieved with phase increments of 118.2° or 121.8°. However, for these values the method suffers from instabilities. In contrast, stable results are obtained with a phase increment of 50°. An algorithm is presented that allows for the calculation of corrected T₁ maps from the apparent values. The method is tested both in phantom experiments and in vivo by acquiring whole‐brain T₁ maps of the human brain. Magn Reson Med 61:125–135, 2009. © 2008 Wiley‐Liss, Inc.     

On the fluid-tissue contrast behavior of high-resolution steady-state sequences

In general, MR image contrast is expected to be resolution independent, but a pronounced loss of contrast is observed between fluids and tissues with contemporary musculoskeletal protocols (typical inplane resolution << 1 mm) using nonbalanced steady‐state free precession, such as double echo steady state. For nonbalanced steady‐state free precession, diffusion sensitivity increases with increasing spoiler moments which increase with decreasing voxel size, suggesting diffusion damping as the major cause for the observed contrast variation. This is confirmed by simulations and measurements indicating that for fluids, diffusion effects become apparent already for resolutions Δx < 1 mm, whereas tissues typically require Δx < 200 μm. Gradient spoiling, however, is generically not minimized but frequently applied along the readout direction. For anisotropic steady‐state free precession scans, the loss of contrast between fluids and tissues from diffusion can thus be minimized by simply moving the spoiler gradients to the lowest resolution direction. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.     

Spin‐locked balanced steady‐state free‐precession (slSSFP)

A spin‐locked balanced steady‐state free‐precession (slSSFP) pulse sequence is described that combines a balanced gradient‐echo acquisition with an off‐resonance spin‐lock pulse for fast MRI. The transient and steady‐state magnetization trajectory was solved numerically using the Bloch equations and was shown to be similar to balanced steady‐state free‐precession (bSSFP) for a range of T₂/T₁ and flip angles, although the slSSFP steady‐state could be maintained with considerably lower radio frequency (RF) power. In both simulations and brain scans performed at 7T, slSSFP was shown to exhibit similar contrast and signal‐to‐noise ratio (SNR) efficiency to bSSFP, but with significantly lower power. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Reduction of flow artifacts by using partial saturation in RF‐spoiled gradient‐echo imaging

Radiofrequency (RF)‐spoiled gradient‐echo imaging provides a signal intensity close to pure T₁ contrast by using spoiler gradients and RF phase cycling to eliminate net transverse magnetization. Generally, spins require many RF excitations to reach a steady‐state magnetization level; therefore, when unsaturated flowing spins enter the imaging slab, they can cause undesirable signal enhancement and generate image artifacts. These artifacts can be reduced by partially saturating an outer slab upstream to drive the longitudinal magnetization close to the steady state, while the partially saturated spins generate no signal until they enter the imaging slab. In this work, magnetization evolution of flowing spins in RF‐spoiled gradient‐echo sequences with and without partial saturation was simulated using the Bloch equations. Next, the simulations were validated by phantom and in vivo experiments. For phantom experiments, a pulsatile flow phantom was used to test partial saturation for a range of flip angles and relaxation times. For in vivo experiments, the technique was used to image the carotid arteries, abdominal aorta, and femoral arteries of normal volunteers. All experiments demonstrated that partial saturation can provide consistent T₁ contrast across the slab while reducing inflow artifacts. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

DANTE-prepared pulse trains: A novel approach to motion-sensitized and motion-suppressed quantitative magnetic resonance imaging

Delay alternating with nutation for tailored excitation (DANTE) pulse trains are well appreciated as frequency‐selective excitation methods in Fourier transform NMR and for spatial tagging in MRI. In this study, nonselective DANTE pulse trains are used in combination with gradient pulses and short repetition times as motion‐sensitive preparation modules. We show that while the longitudinal magnetization of static tissue is mostly preserved, flowing spins are largely (or fully) attenuated as they fail to establish transverse steady state due to a spoiling effect caused by flow along the applied gradient. The attenuation of flowing spins is effectively insensitive to spin velocity (above a low threshold) and can be approximately quantified with a simple T₁ longitudinal magnetization decay model. The relevant analytical equations for moving spins and static spins during DANTE module application are derived for both transient and steady state epochs. The equations are validated by comparing analytical solutions and numerical Bloch equation simulations against experimental observations in phantoms and in vivo. Based on this contrast mechanism, the application of the DANTE preparation to black blood vessel imaging is proposed. A simple demonstration of DANTE black blood imaging modules shows that it provides excellent blood signal suppression and static tissue signal preservation. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.     

Simplified quantification of labile proton concentration‐weighted chemical exchange rate (kws) with RF saturation time dependent ratiometric analysis (QUESTRA): Normalization of relaxation and RF irradiation spillover effects for improved quantitative chemical exchange saturation transfer (CEST) MRI

Chemical exchange saturation transfer MRI is an emerging imaging technique capable of detecting dilute proteins/peptides and microenvironmental properties, with promising in vivo applications. However, chemical exchange saturation transfer MRI contrast is complex, varying not only with the labile proton concentration and exchange rate, but also with experimental conditions such as field strength and radiofrequency (RF) irradiation scheme. Furthermore, the optimal RF irradiation power depends on the exchange rate, which must be estimated in order to optimize the chemical exchange saturation transfer MRI experiments. Although methods including numerical fitting with modified Bloch‐McConnell equations, quantification of exchange rate with RF saturation time and power (QUEST and QUESP), have been proposed to address this relationship, they require multiple‐parameter non‐linear fitting and accurate relaxation measurement. Our work extended the QUEST algorithm with ratiometric analysis (QUESTRA) that normalizes the magnetization transfer ratio at labile and reference frequencies, which effectively eliminates the confounding relaxation and RF spillover effects. Specifically, the QUESTRA contrast approaches its steady state mono‐exponentially at a rate determined by the reverse exchange rate (k_ws), with little dependence on bulk water T₁, T₂, RF power and chemical shift. The proposed algorithm was confirmed numerically, and validated experimentally using a tissue‐like phantom of serially titrated pH compartments. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Quantitative mapping of T2 using partial spoiling

Fast quantitative MRI has become an important tool for biochemical characterization of tissue beyond conventional T₁, T₂, and T₂*‐weighted imaging. As a result, steady‐state free precession (SSFP) techniques have attracted increased interest, and several methods have been developed for rapid quantification of relaxation times using steady‐state free precession. In this work, a new and fast approach for T₂ mapping is introduced based on partial RF spoiling of nonbalanced steady‐state free precession. The new T₂ mapping technique is evaluated and optimized from simulations, and in vivo results are presented for human brain at 1.5 T and for human articular cartilage at 3.0 T. The range of T₂ for gray and white matter was from 60 msec (for the corpus callosum) to 100 msec (for cortical gray matter). For cartilage, spatial variation in T₂ was observed between deep (34 msec) and superficial (48 msec) layers, as well as between tibial (33 msec), femoral, (54 msec) and patellar (43 msec) cartilage. Excellent correspondence between T₂ values derived from partially spoiled SSFP scans and the ones found with a reference multicontrast spin‐echo technique is observed, corroborating the accuracy of the new method for proper T₂ mapping. Finally, the feasibility of a fast high‐resolution quantitative partially spoiled SSFP T₂ scan is demonstrated at 7.0 T for human patellar cartilage. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Small‐tip fast recovery imaging using non‐slice‐selective tailored tip‐up pulses and radiofrequency‐spoiling

Small‐tip fast recovery (STFR) imaging is a new steady‐state imaging sequence that is a potential alternative to balanced steady‐state free precession. Under ideal imaging conditions, STFR may provide comparable signal‐to‐noise ratio and image contrast as balanced steady‐state free precession, but without signal variations due to resonance offset. STFR relies on a tailored “tip‐up,” or “fast recovery,” radiofrequency pulse to align the spins with the longitudinal axis after each data readout segment. The design of the tip‐up pulse is based on the acquisition of a separate off‐resonance (B0) map. Unfortunately, the design of fast (a few ms) slice‐ or slab‐selective radiofrequency pulses that accurately tailor the excitation pattern to the local B0 inhomogeneity over the entire imaging volume remains a challenging and unsolved problem. We introduce a novel implementation of STFR imaging based on “non‐slice‐selective” tip‐up pulses, which simplifies the radiofrequency pulse design problem significantly. Out‐of‐slice magnetization pathways are suppressed using radiofrequency‐spoiling. Brain images obtained with this technique show excellent gray/white matter contrast, and point to the possibility of rapid steady‐state T₂/T₁‐weighted imaging with intrinsic suppression of cerebrospinal fluid, through‐plane vessel signal, and off‐resonance artifacts. In the future, we expect STFR imaging to benefit significantly from parallel excitation hardware and high‐order gradient shim systems. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

An analytical description of balanced steady‐state free precession with finite radio‐frequency excitation

Conceptually, the only flaw in the standard steady‐state free precession theory is the assumption of quasi‐instantaneous radio‐frequency pulses, and 10–20% signal deviations from theory are observed for common balanced steady‐state free precession protocols. This discrepancy in the steady‐state signal can be resolved by a simple T₂ substitution taking into account reduced transverse relaxation effects during finite radio‐frequency excitation. However, finite radio‐frequency effects may also affect the transient phase of balanced steady‐state free precession, its contrast or its spin‐echo nature and thereby have an adverse effect on common steady‐state free precession magnetization preparation methods. As a result, an in‐depth understanding of finite radio‐frequency effects is not only of fundamental theoretical interest but also has direct practical implications. In this article, an analytical solution for balanced steady‐state free precession with finite radio‐frequency pulses is derived for the transient phase (under ideal conditions) and in the steady state demonstrating that balanced steady‐state free precession key features are preserved but revealing an unexpected dependency of finite radio‐frequency effects on relaxation times for the transient decay. Finally, the mathematical framework reveals that finite radio‐frequency theory can be understood as a generalization of alternating repetition time and fluctuating equilibrium steady‐state free precession sequence schemes. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.     

Finite RF pulse correction on DESPOT2

Magnetization transfer and finite radiofrequency (RF) pulses affect the steady state of balanced steady state free precession. As quantification of transverse relaxation (T₂) with driven equilibrium single pulse observation of T₂ is based on two balanced steady state free precession acquisitions, both effects can influence the outcome of this method: a short RF pulse per repetition time (T_RF/TR ? 1) leads to considerable magnetization transfer effects, whereas prolonged RF pulses (T_RF/TR > 0.2) minimize magnetization transfer effects, but lead to increased finite pulse effects. A correction for finite pulse effects is thus implemented in the driven equilibrium single pulse observation of T₂ theory to compensate for reduced transverse relaxation effects during excitation. It is shown that the correction successfully removes the driven equilibrium single pulse observation of T₂ dependency on the RF pulse duration. A reduction of the variation in obtained T₂ from over 50% to less than 10% is achieved. We hereby provide a means of acquiring magnetization transfer‐free balanced steady state free precession images to yield accurate T₂ values using elongated RF pulses. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.     

Optimal radiofrequency and gradient spoiling for improved accuracy of T1 and B1 measurements using fast steady‐state techniques

Variable flip angle T₁ mapping and actual flip‐angle imaging B₁ mapping are widely used quantitative MRI methods employing radiofrequency spoiled gradient‐echo pulse sequences. Incomplete elimination of the transverse magnetization in these sequences has been found to be a critical source of T₁ and B₁ measurement errors. In this study, comprehensive theoretical analysis of spoiling‐related errors in variable flip angle and actual flip‐angle imaging methods was performed using the combined isochromat summation and diffusion propagator model and validated by phantom experiments. The key theoretical conclusion is that correct interpretation of spoiling phenomena in fast gradient‐echo sequences requires accurate consideration of the diffusion effect. A general strategy for improvement of T₁ and B₁ measurement accuracy was proposed based on the strong spoiling regimen, where diffusion‐modulated spatial averaging of isochromats becomes a dominant factor determining magnetization evolution. Practical implementation of strongly spoiled variable flip angle and actual flip‐angle imaging techniques requires sufficiently large spoiling gradient areas (A_G) in combination with optimal radiofrequency phase increments (?₀). Optimal regimens providing <2% relative T₁ and B₁ measurement errors in a variety of tissues were theoretically derived for prospective in vivo variable flip angle (pulse repetition time = 15–20 ms, A_G = 280–450 mT·ms/m, ?₀ = 169°) and actual flip‐angle imaging (pulse repetition time₁/pulse repetition time₂ = 20/100 ms, A_G1/A_G2 = 450/2250 mT·ms/m, ?₀ = 39°) applications based on 25 mT/m maximal available gradient strength. Magn Reson Med 63:1610–1626, 2010. © 2010 Wiley‐Liss, Inc.     

Effect of inflow of fresh blood on vascular‐space‐occupancy (VASO) contrast

In vascular‐space‐occupancy (VASO)‐MRI, cerebral blood volume (CBV)‐weighted contrast is generated by applying a nonselective inversion pulse followed by imaging when blood water magnetization is zero. An uncertainty in VASO relates to the completeness of blood water nulling. Specifically, radio frequency (RF) coils produce a finite inversion volume, rendering the possibility of fresh, non‐nulled blood. Here, VASO‐functional MRI (fMRI) was performed for varying inversion volume and TR using body coil RF transmission. For thin inversion volume thickness (δ_tot < 10 mm), VASO signal changes were positive (ΔS/S = 2.1–2.6%). Signal changes were negative and varied in magnitude for intermediate inversion volumes (δ_tot = 100–300 mm), yet did not differ significantly (P > 0.05) for δ_tot > 300 mm. These data suggest that blood water is in steady state for δ_tot > 300 mm. In this appropriate range, long‐TR VASO data converged to a less negative value (ΔS/S = –1.4% ± 0.2%) than short‐TR data (ΔS/S = –2.2% ± 0.2%), implying that cerebral blood flow or transit‐state effects may influence VASO contrast at short TR. Magn Reson Med 61:473–480, 2009. © 2009 Wiley‐Liss, Inc.     

Perfusion imaging with a freely diffusible hyperpolarized contrast agent

Contrast agents that can diffuse freely into or within tissue have numerous attractive features for perfusion imaging. Here we present preliminary data illustrating the suitability of hyperpolarized ¹³C labeled 2‐methylpropan‐2‐ol (also known as dimethylethanol, tertiary butyl alcohol and tert‐butanol) as a freely diffusible contrast agent for magnetic resonance perfusion imaging. Dynamic ¹³C images acquired in rat brain with a balanced steady‐state free precession sequence following administration of hyperpolarized 2‐methylpropan‐2‐ol show that this agent can be imaged with 2–4s temporal resolution, 2 mm slice thickness, and 700 μm in‐plane resolution while retaining adequate signal‐to‐noise ratio. ¹³C relaxation measurements on 2‐methylpropan‐2‐ol in blood at 9.4T yield T₁ = 46 ± 4s and T₂ = 0.55 ± 0.03s. In the rat brain at 4.7T, analysis of the temporal dynamics of the balanced steady‐state free precession image intensity in tissue and venous blood indicate that 2‐methylpropan‐2‐ol has a T₂ of roughly 2–4s and a T₁ of 43 ± 24s. In addition, the images indicate that 2‐methylpropan‐2‐ol is freely diffusible in brain and hence has a long residence time in tissue; this in turn makes it possible to image the agent continuously for tens of seconds. These characteristics show that 2‐methylpropan‐2‐ol is a promising agent for robust and quantitative perfusion imaging in the brain and body. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Contrast‐enhanced specific absorption rate‐efficient 3D cardiac cine with respiratory‐triggered radiofrequency gating

Purpose:

To investigate the use of radiofrequency (RF) gating in conjunction with a paramagnetic contrast agent to reduce the specific absorption rate (SAR) and increase the blood‐myocardium contrast in balanced steady‐state free precession (bSSFP) 3D cardiac cine.

Materials and Methods:

RF gating was implemented by synchronizing the RF‐excitation with an external respiratory sensor (bellows), which could additionally be used for respiratory gating. For reference, respiratory‐gated 3D cine images were acquired without RF gating. Free‐breathing 3D cine images were acquired in eight healthy subjects before and after contrast injection (Gd‐BOPTA) and compared to breath‐hold 2D cine.

Results:

RF‐gated 3D cine reduced the SAR by nearly 40% without introducing significant artifacts while providing left ventricle (LV) measurements similar to those obtained with 2D cine. The contrast‐to‐noise ratio (CNR) was significantly higher for 3D cine compared to 2D cine, both before and after contrast injection; however, no statistically significant CNR increase was observed for the postcontrast 3D cine compared to the precontrast acquisitions.

Conclusion:

Respiratory‐triggered RF gating significantly reduces SAR in 3D cine acquisitions, which may enable a more widespread clinical use of 3D cine. Furthermore, CNR of 3D bSSFP cine is higher than of 2D and administration of Gd‐BOPTA does not improve the CNR of 3D cine. J. Magn. Reson. Imaging 2013;37:986–992. © 2012 Wiley Periodicals, Inc.     

Gradient echo imaging

Magnetic resonance imaging (MRI) based on gradient echoes is used in a wide variety of imaging techniques and clinical applications. Gradient echo sequences form the basis for an essential group of imaging methods that find widespread use in clinical practice, particularly when fast imaging is important, as for example in cardiac MRI or contrast‐enhanced MR angiography. However, the term “gradient echo sequence” is somewhat unspecific, as even images acquired with the most common sequences employing the gradient echo for data acquisition can significantly differ in signal, contrast, artifact behavior, and sensitivity to, eg, flow. This is due to the different use of sequence timing and basic sequence building blocks such as spoiler gradients or specific radiofrequency (RF) pulse phase patterns. In this article the basic principles of gradient echo formation compared to spin echo imaging are reviewed and the properties of gradient echo imaging in its simplest form (TR ? T₂) are described. Further, the most common three variants of fast gradient echo sequences (TR < T₂), namely, unbalanced gradient echo, RF spoiled gradient echo, and balanced steady state free precession; are discussed. For each gradient echo sequence type, examples of applications exploiting the specific properties of the individual technique are presented. J. Magn. Reson. Imaging 2012;35:1274–1289. © 2012 Wiley Periodicals, Inc.     

Magnetization exchange in capillaries by microcirculation affects diffusion-controlled spin-relaxation: A model which describes the effect of perfusion on relaxation enhancement by intravascular contrast agents

The effect of perfusion on relaxation time in tissue has only been considered for first-pass kinetics of NMR-signal after application of contrast agents. The importance of perfusion on relaxation has not yet been studied for steady state conditions, i.e., when the intravascular relaxation rate is constant in time. The aim of this study is to develop a model in which T, relaxation is derived as a function of perfusion and intracap-illary volume fraction (regional blood volume). Tissue is considered to be two-compartment system, which consists of intracapillary and extravascular space. Intracapillary relaxation differs from relaxation in the arterial system due to diffusion-exchange of magnetization from extravascular to intracapillary space. Perfusion tends to attenuate this difference and thus counteracts the effect on intracapillary relaxation. Relaxation in the extravascular space becomes a function of perfusion because extravascular and intracapillary magnetization are linked by diffusion. This dependence is presented in analytical form and a generic equation is derived. A T₁ experiment is considered in which all spins of tissue and blood are inverted at the beginning. Calculations are performed for the fast exchange model of tissue. Perfusion increases relaxation enhancement of intravascular contrast agents. This effect is considerable in highly perfused tissue like myocardium. The dependence of relaxation on perfusion implies an overestimation of the regional blood volume when the calculation of the latter is based on tissue models that neglect perfusion. The model presented here is applied to predict the effect of perfusion on T₁ imaging with FLASH-pulse sequences because this technique has been proven to be a powerful method to obtain T₁ maps within a short time interval. For the fast exchange model, two algorithms are suggested that determine perfusion and regional blood volume from T₁ imaging in the presence and absence of intravascular contrast agents.     

Intrascanner and interscanner variability of magnetization transfer‐sensitized balanced steady‐state free precession imaging

Recently, a new and fast three‐dimensional imaging technique for magnetization transfer ratio (MTR) imaging has been proposed based on a balanced steady‐state free precession protocol with modified radiofrequency pulses. In this study, optimal balanced steady‐state free precession MTR protocol parameters were derived for maximum stability and reproducibility. Variability between scans was assessed within white and gray matter for nine healthy volunteers using two different 1.5 T clinical systems at six different sites. Intrascanner and interscanner MTR measurements were well reproducible (coefficient of variation: c_v < 0.012 and c_v < 0.015, respectively) and results indicate a high stability across sites (c_v < 0.017) for optimal flip angle settings. This study demonstrates that balanced steady‐state free precession MTR not only benefits from short acquisition time and high signal‐to‐noise ratio but also offers excellent reproducibility and low variability, and it is thus proposed for clinical MTR scans at individual sites as well as for multicenter studies. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Effects of inflow and radiofrequency spoiling on the arterial input function in dynamic contrast‐enhanced MRI: A combined phantom and simulation study

The arterial input function is crucial in pharmacokinetic analysis of dynamic contrast‐enhanced MRI data. Among other artifacts in arterial input function quantification, the blood inflow effect and nonideal radiofrequency spoiling can induce large measurement errors with subsequent reduction of accuracy in the pharmacokinetic parameters. These errors were investigated for a 3D spoiled gradient‐echo sequence using a pulsatile flow phantom and a total of 144 typical imaging settings. In the presence of large inflow effects, results showed poor average accuracy and large spread between imaging settings, when the standard spoiled gradient‐echo signal equation was used in the analysis. For example, one of the investigated inflow conditions resulted in a mean error of about 40% and a spread, given by the coefficient of variation, of 20% for K^trans. Minimizing inflow effects by appropriate slice placement, combined with compensation for nonideal radiofrequency spoiling, significantly improved the results, but they remained poorer than without flow (e.g., 3–4 times larger coefficient of variation for K^trans). It was concluded that the 3D spoiled gradient‐echo sequence is not optimal for accurate arterial input function quantification and that correction for nonideal radiofrequency spoiling in combination with inflow minimizing slice placement should be used to reduce the errors. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.