B1 transmission‐field inhomogeneity and enhancement ratio errors in dynamic contrast‐enhanced MRI (DCE‐MRI) of the breast at 3T

Purpose:

To quantify B₁ transmission‐field inhomogeneity in breast imaging of normal volunteers at 3T using 3D T₁‐weighted spoiled gradient echo and to assess the resulting errors in enhancement ratio (ER) measured in dynamic contrast‐enhanced MRI (DCE‐MRI) studies of the breast.

Materials and Methods:

A total of 25 volunteers underwent breast imaging at 3T and the B₁ transmission‐fields were mapped. Gel phantoms that simulate pre‐ and postcontrast breast tissue T₁ were developed. The effects of B₁‐field inhomogeneity on ER, as measured using a 3D spoiled gradient echo sequence, were investigated by computer simulation and experiments on gel phantoms.

Results:

It was observed that by using the patient orientation and MR scanner employed in this study, the B₁ transmission‐field field is always reduced toward the volunteer's right side. The median B₁‐field in the right breast is reduced around 40% of the expected B₁‐field. For some volunteers the amplitude was reduced by more than 50%. Computer simulation and experiment showed that a reduction in B₁‐field decreases ER. This reduction increases with both B₁‐field error and contrast agent uptake.

Conclusion:

B₁ transmission‐field inhomogeneity is a critical issue in breast imaging at 3T and causes errors in quantifying ER. These errors would be sufficient to reduce the conspicuity of a malignant lesion and could result in reduced sensitivity for cancer detection. J. Magn. Reson. Imaging 2010;31:234–239. © 2009 Wiley‐Liss, Inc.     

A B1‐insensitive high resolution 2D T1 mapping pulse sequence for dGEMRIC of the HIP at 3 Tesla

Early detection of cartilage degeneration in the hip may help prevent onset and progression of osteoarthritis in young patients with femoroacetabular impingement. Delayed gadolinium‐enhanced MRI of cartilage is sensitive to cartilage glycosaminoglycan loss and could serve as a diagnostic tool for early cartilage degeneration. We propose a new high resolution 2D T₁ mapping saturation–recovery pulse sequence with fast spin echo readout for delayed gadolinium‐enhanced magnetic resonance imaging of cartilage of the hip at 3 T. The proposed sequence was validated in a phantom and in 10 hips, using radial imaging planes, against a rigorous multipoint saturation–recovery pulse sequence with fast spin echo readout. T₁ measurements by the two pulse sequences were strongly correlated (R² > 0.95) and in excellent agreement (mean difference = ?8.7 ms; upper and lower 95% limits of agreement = 64.5 and ?81.9 ms, respectively). T₁ measurements were insensitive to B₁₊ variation as large as 20%, making the proposed T₁ mapping technique suitable for 3 T. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

T1 corrected B1 mapping using multi‐TR gradient echo sequences

This work presents a new approach toward a fast, simultaneous amplitude of radiofrequency field (B₁) and T₁ mapping technique. The new method is based on the “actual flip angle imaging” (AFI) sequence. However, the single pulse repetition time (TR) pair used in the standard AFI sequence is replaced by multiple pulse repetition time sets. The resulting method was called “multiple TR B₁/T₁ mapping” (MTM). In this study, MTM was investigated and compared to standard AFI in simulations and experiments. Feasibility and reliability of MTM were proven in phantom and in vivo experiments. Error propagation theory was applied to identify optimal sequence parameters and to facilitate a systematic noise comparison to standard AFI. In terms of accuracy and signal‐to‐noise ratio, the presented method outperforms standard AFI B₁ mapping over a wide range of T₁. Finally, the capability of MTM to determine T₁ was analyzed qualitatively and quantitatively, yielding good agreement with reference measurements. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Improved B1 homogeneity of 3 Tesla breast MRI using dual-source parallel radiofrequency excitation

Purpose:

To compare breast MRI B₁ homogeneity at 3 Tesla (T) with and without dual‐source parallel radiofrequency (RF) excitation.

Materials and Methods:

After institutional review board approval, we evaluated 14 consecutive breast MR examinations performed at 3T that included three‐dimensional B₁ maps created separately with conventional single‐source and dual‐source parallel RF excitation techniques. We measured B₁ values (expressed as % of intended B₁) on each B₁ map at nipple level in multiple bilateral locations: anterior, lateral, central, medial, and posterior. Mean whole breast and location specific B₁ values were calculated and compared between right and left breasts using paired t‐test.

Results:

Mean whole breast B₁ values differed significantly between right and left breasts with standard single‐source RF excitation (difference L‐R, Δ = 9.2%; P < 0.001) but not with dual‐source parallel RF excitation (Δ = 2.3%; P = 0.085). Location specific B₁ values differed significantly between right and left on single‐source in the lateral (P = 0.014), central (P = 0.0001), medial (P = 0.0013), and posterior (P < 0.0001) locations. Conversely, mean B₁ values differed significantly on dual‐source parallel RF excitation for only the anterior (P = 0.030) and lateral (P = 0.0003) locations.

Conclusion:

B₁ homogeneity is improved with dual‐source parallel RF excitation on 3T breast MRI when compared with standard single‐source RF excitation technique. J. Magn. Reson. Imaging 2012;35:1222‐1226. © 2012 Wiley Periodicals, Inc.     

Phase‐sensitive sodium B1 mapping

Quantitative sodium MRI requires accurate knowledge of factors affecting the sodium signal. One important determinant of sodium signal level is the transmit B₁ field strength. However, the low signal‐to‐noise ratio typical of sodium MRI makes accurate B₁ mapping in reasonable scan times challenging. A new phase‐sensitive B₁ mapping technique has recently been shown to work better than the widely used dual‐angle method in low‐signal‐to‐noise ratio situations and over a broader range of flip angles. In this work, the phase‐sensitive B₁ mapping technique is applied to sodium, and its performance compared to the dual‐angle method through both simulation and phantom studies. The phase‐sensitive method is shown to yield higher quality B₁ maps at low signal‐to‐noise ratio and greater consistency of measurement than the dual‐angle method. An in vivo sodium B₁ map of the human breast is also shown, demonstrating the phase‐sensitive method's feasibility for human studies. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

TROMBONE: T1‐relaxation‐oblivious mapping of transmit radio‐frequency field (B1) for MRI at high magnetic fields

Fast, 3D radio‐frequency transmit field (B₁) mapping is important for parallel transmission, spatially selective pulse design and quantitative MRI applications. It has been shown that actual flip angle imaging—two interleaved spoiled gradient recalled echo images acquired in steady state with two very short time delays (TR₁, TR₂)—is an attractive method of B₁ mapping. Herein, we describe the TROMBONE method that efficiently integrates actual flip angle imaging with EPI imaging, alleviates very short TR requirement of actual flip angle imaging and through their synergy yields up to 16 times higher precision in B₁ estimation in the same experimental time. High precision of TROMBONE can be traded for faster scans. The map of B₁ reconstructed from the ratio of intensities of two images is insensitive to longitudinal relaxation time (T₁) in the physiologically relevant range. A table of the optimal acquisition protocol parameters for various target experimental conditions is provided. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

On B1 inhomogeneity correction of in vivo human brain glutamate chemical exchange saturation transfer contrast at 7T

The effects of radio frequency field (B₁) inhomogeneity on measured in vivo human brain glutamate chemical exchange saturation transfer contrast maps are normally confounded with contributions from chemical exchange saturation transfer, direct saturation and magnetization transfer effects. Consequently, the chemical exchange saturation transfer effect variation with B₁ follows a complicated function and depends on the tissue types as well. In this work, we developed and tested a novel approach for B₁ inhomogeneity correction based on acquiring calibration data at a coarsely sampled B₁ values in conjunction with the measured B₁ maps. With this approach, different calibration curves are derived for gray matter and white matter instead of a simple linear scaling based on local B₁ values. Potential extensions of this approach to study chemical exchange saturation transfer contrast from other metabolites and tissue types are discussed. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

Early marker for Alzheimer's disease: Hippocampus T1rho (T1ρ) estimation

Purpose

To evaluate the T1rho (T_1ρ) MRI relaxation time in hippocampus in the brain of Alzheimer's disease (AD), mild cognitive impairment (MCI), and control, and to determine whether the T_1ρ shows any significant difference between these cohorts.

Materials and Methods

With informed consent, AD (n = 49), MCI (n = 48), and age‐matched control (n = 31) underwent T_1ρ MRI on a Siemens 1.5T Scanner. T_1ρ values were automatically calculated from the left and right hippocampus region using in‐house developed software. Bonferroni post‐hoc multiple comparisons was performed to compare the T_1ρ value among the different cohorts.

Results

Significantly higher T_1ρ values were observed both in AD (P = 0.000) and MCI (P = 0.037) cohorts compared to control; also, the T_1ρ in AD was significantly high over (P = 0.032) MCI. Hippocampus T_1ρ was 13% greater in the AD patients than control, while in MCI it was 7% greater than control. Hippocampus T_1ρ in AD patients was 6% greater than MCI.

Conclusion

Higher hippocampus T_1ρ values in the AD patients might be associated with the increased plaques burden. A follow‐up study would help to determine the efficacy of T_1ρ values as a predictor of developing AD in the control and MCI individuals. J. Magn. Reson. Imaging 2009;29:1008–1012. © 2009 Wiley‐Liss, Inc.     

Combined use of T2‐weighted MRI and T1‐weighted dynamic contrast–enhanced MRI in the automated analysis of breast lesions

A multiparametric computer‐aided diagnosis scheme that combines information from T₁‐weighted dynamic contrast–enhanced (DCE)‐MRI and T₂‐weighted MRI was investigated using a database of 110 malignant and 86 benign breast lesions. Automatic lesion segmentation was performed, and three categories of lesion features (geometric, T₁‐weighted DCE, and T₂‐weighted) were automatically extracted. Stepwise feature selection was performed considering only geometric features, only T₁‐weighted DCE features, only T₂‐weighted features, and all features. Features were merged with Bayesian artificial neural networks, and diagnostic performance was evaluated by ROC analysis. With leave‐one‐lesion‐out cross‐validation, an area under the ROC curve value of 0.77 ± 0.03 was achieved with T₂‐weighted‐only features, indicating high diagnostic value of information in T₂‐weighted images. Area under the ROC curve values of 0.79 ± 0.03 and 0.80 ± 0.03 were obtained for geometric‐only features and T₁‐weighted DCE‐only features, respectively. When all features were considered, an area under the ROC curve value of 0.85 ± 0.03 was achieved. We observed P values of 0.006, 0.023, and 0.0014 between the geometric‐only, T₁‐weighted DCE‐only, and T₂‐weighted‐only features and all features conditions, respectively. When ranked, the P values satisfied the Holm–Bonferroni multiple‐comparison test; thus, the improvement of multiparametric computer‐aided diagnosis was statistically significant. A computer‐aided diagnosis scheme that combines information from T₁‐weighted DCE and T₂‐weighted MRI may be advantageous over conventional T₁‐weighted DCE‐MRI computer‐aided diagnosis. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Transmit B1‐field correction at 7T using actively tuned coupled inner elements

When volume coils are used for ¹H imaging of the human head at 7T, wavelength effects in tissue cause a variation in intensity, that is typically brighter at the center of the head and darker in the periphery. Much of this image nonuniformity can be attributed to variation in the effective transmit B₁ field, which falls by ～ 50% to the left and right of center at mid‐elevation in the brain. Because most of this B₁ loss occurs in the periphery of the brain, we have explored use of actively controlled, off‐resonant loop elements to locally enhance the transmit B₁ field in these regions. When tuned to frequencies above the NMR frequency, these elements provide strong local enhancement of the B₁ field of the transmit coil. Because they are tuned off‐resonance, some volume coil detuning results, but resistive loading of the coil mode remains dominated by the sample. By digitally controlling their frequency offsets, the field enhancement of each inner element can be placed under active control. Using an array of eight digitally controlled elements placed around a custom‐built head phantom, we demonstrate the feasibility of improving the B₁ homogeneity of a transmit/receive volume coil without the need for multiple radio frequency transmit channels. Magn Reson Med, 2011. © 2011 Wiley‐Liss, Inc.     

Experimental protocol for activation‐induced manganese‐enhanced MRI (AIM‐MRI) based on quantitative determination of Mn content in rat brain by fast T1 mapping

In activation‐induced manganese‐enhanced MRI (AIM‐MRI) experiments, differential accumulation of Mn in activated and silent brain areas is generally assessed using T₁‐weighted images and quantified by the enhancement of signal intensity (SI), calculated with reference to SI before Mn administration or to SI of brain regions unaffected by the specific stimulus. However, SI enhancement can be unreliable when animals are removed from and reinserted into the magnet. We have developed an experimental protocol based on repeated intraperitoneal (i.p.) injections of Mn, quantitative determination of T₁, and coregistration of images to a rat brain atlas that allows absolute quantification of Mn concentration in selected brain areas. Results showed that interanimal variability of postcontrast T₁ values was very low (compared to the experimental error in T₁ determinations) allowing detection of differential regional Mn uptake in stimulated and unstimulated animals. In addition we have determined in vivo relaxivity of Mn in brain tissue and its frequency dependence. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Single‐shot T1 mapping using simultaneous acquisitions of spin‐ and stimulated‐echo‐planar imaging (2D ss‐SESTEPI)

The conventional stimulated‐echo NMR sequence only measures the longitudinal component while discarding the transverse component, after tipping up the prepared magnetization. This transverse magnetization can be used to measure a spin echo, in addition to the stimulated echo. Two‐dimensional single‐shot spin‐ and stimulated‐echo‐planar imaging (ss‐SESTEPI) is an echo‐planar‐imaging‐based single‐shot imaging technique that simultaneously acquires a spin‐echo‐planar image and a stimulated‐echo‐planar image after a single radiofrequency excitation. The magnitudes of the spin‐echo‐planar image and stimulated‐echo‐planar image differ by T₁ decay and diffusion weighting for perfect 90° radiofrequency and thus can be used to rapidly measure T₁. However, the spatial variation of amplitude of radiofrequency field induces uneven splitting of the transverse magnetization for the spin‐echo‐planar image and stimulated‐echo‐planar image within the imaging field of view. Correction for amplitude of radiofrequency field inhomogeneity is therefore critical for two‐dimensional ss‐SESTEPI to be used for T₁ measurement. We developed a method for amplitude of radiofrequency field inhomogeneity correction by acquiring an additional stimulated‐echo‐planar image with minimal mixing time, calculating the difference between the spin echo and the stimulated echo and multiplying the stimulated‐echo‐planar image by the inverse functional map. Diffusion‐induced decay is corrected by measuring the average diffusivity during the prescanning. Rapid single‐shot T₁ mapping may be useful for various applications, such as dynamic T₁ mapping for real‐time estimation of the concentration of contrast agent in dynamic contrast enhancement MRI. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

Rapid T1 mapping of mouse myocardium with saturation recovery look‐locker method

Dynamic contrast‐enhanced MRI using gadolinium or manganese provides unique characterization of myocardium and its pathology. In this study, an electrocardiography (ECG) triggered saturation recovery Look‐Locker method was developed and validated for fast cardiac T₁ mapping in small animal models. By sampling the initial portion of the longitudinal magnetization recovery curve, high temporal resolution (～3 min) can be achieved at a high spatial resolution (195 × 390 μm2) in mouse heart without the aid of parallel imaging or echo‐planar imaging. Validation studies were performed both in vitro on a phantom and in vivo on C57BL/6 mice (n = 6). Our results showed a strong agreement between T₁ measured by saturation recovery Look‐Locker and by the standard saturation recovery method in vitro or inversion recovery Look‐Locker in vivo. The utility of saturation recovery Look‐Locker in dynamic contrast‐enhanced MRI studies was demonstrated in manganese‐enhanced MRI experiments in mice. Our results suggest that saturation recovery Look‐Locker can provide rapid and accurate cardiac T₁ mapping for studies using small animal models. Magn Reson Med, 2010. © 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.     

Monitoring of release of cargo from nanocarriers by MRI/MR spectroscopy (MRS): Significance of T2/T effect of iron particles

To monitor the release of cargo molecules from nanocarriers, a novel MRI/MRS technique was developed and tested. This novel approach uses a simultaneous encapsulation of superparamagnetic iron oxide (SPIO) nanoparticles and either a gadolinium (Gd)‐based paramagnetic contrast agent, Gd‐diethylenetriamine pentaacetic acid bismethylamide(GdDTPA‐BMA), for MRI, or an anticancer agent, 5‐fluorouracil (5‐FU), for MRS. These agents have significantly different diffusion properties due to their different molecular sizes. Strong negative signal enhancement due to the T₂ effects of SPIO dominates the positive T₁ contrast generated by GdDTPA‐BMA when SPIO and GdDTPA‐BMA are in close proximity (intact form). Positive T₁ contrast becomes evident upon release of GdDTPA‐BMA from the carrier once the distance between GdDTPA‐BMA and SPIO molecules is beyond the T₂ enhancement range. Similarly, intact nanocarriers loaded with 5‐FU and SPIO have a broad ¹⁹F resonance line because line‐width is inversely proportional to T^*₂, while free 5‐FU appears as a narrow resonance line once it is released from the liposomes. This technique allowed monitoring of the release of cargo molecules from liposomes encapsulating both SPIO and either GdDTPA‐BMA or 5‐FU by MRI/MRS in vitro using 2% agarose gel phantoms. Experimental results demonstrate successful demarcation of the released cargo molecules vs. encapsulated molecules. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Spectrally selective B1‐insensitive T2 magnetization preparation sequence

A T₂ magnetization‐preparation (T₂ Prep) sequence is proposed that is insensitive to B₁ field variations and simultaneously provides fat suppression without any further increase in specific absorption rate (SAR). Increased B₁ inhomogeneity at higher magnetic field strength (B₀ ≥ 3T) necessitates a preparation sequence that is less sensitive to B₁ variations. For the proposed technique, T₂ weighting in the image is achieved using a segmented B₁‐insensitive rotation (BIR‐4) adiabatic pulse by inserting two equally long delays, one after the initial reverse adiabatic half passage (AHP), and the other before the final AHP segment of a BIR‐4 pulse. This sequence yields T₂ weighting with both B₁ and B₀ insensitivity. To simultaneously suppress fat signal (at the cost of B₀ insensitivity), the second delay is prolonged so that fat accumulates additional phase due to its chemical shift. Numerical simulations as well as phantom and in vivo image acquisitions were performed to show the efficacy of the proposed technique. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Correction of main and transmit magnetic field (B0 and B1) inhomogeneity effects in multicomponent‐driven equilibrium single‐pulse observation of T1 and T2

Multicomponent‐driven equilibrium single‐component observation of T₁ and T₂ offers a new approach to multiple component relaxation time and myelin water analysis. The method derives two‐component relaxation information from spoiled and fully balanced steady‐state (SPGR and bSSFP) imaging data acquired over multiple flip angles. Although these steady‐state imaging techniques afford rapid acquisition times and high signal‐to‐noise ratio efficiency, they are also sensitive to main (B₀) and transmit (B₁) magnetic field inhomogeneities. These effects alter the measured signal from their theoretical values and lead to substantive errors in the derived myelin volume fraction estimates. Here, we incorporate correction techniques to mitigate these effects. DESPOT1‐HIFI is used to first calibrate the transmitted flip angles; and B₀ affects are removed through the inclusion of an additional parameter in the multicomponent‐driven equilibrium single‐component observation of T₁ and T₂ fitting, coupled with the acquisition of multiple phase‐cycled bSSFP data. The performance of these correction techniques was evaluated using numerical simulations, demonstrating effective removal of B₀ and B₁‐induced errors in the derived myelin fraction relaxation parameters. The approach was also successfully demonstrated in vivo, with near artifact‐free whole‐brain, high spatial resolution (1.7 mm × 1.7 mm × 1.7 mm isotropic voxels) myelin water fraction maps acquired in a clinically feasible 16 min. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.     

T1ρ MRI quantification of arthroscopically confirmed cartilage degeneration

Nine asymptomatic subjects and six patients underwent T₁ρ MRI to determine whether Outerbridge grade 1 or 2 cartilage degeneration observed during arthroscopy could be detected noninvasively. MRI was performed 2‐3 months postarthroscopy, using sagittal T₁‐weighted and axial and coronal T₁ρ MRI, from which spatial T₁ρ relaxation maps were calculated from segmented T₁‐weighted images. Median T₁ρ relaxation times of patients with arthroscopically documented cartilage degeneration and asymptomatic subjects were significantly different (P < 0.001), and median T₁ρ exceeded asymptomatic articular cartilage median T₁ρ by 2.5 to 9.2 ms. In eight observations of mild cartilage degeneration at arthroscopy (Outerbridge grades 1 and 2), mean compartment T₁ρ was elevated in five, but in all observations, large foci of increased T₁ρ were observed. It was determined that T₁ρ could detect some, but not all, Outerbridge grade 1 and 2 cartilage degeneration but that a larger patient population is needed to determine the sensitivity to these changes. Magn Reson Med 63:1376–1382, 2010. © 2010 Wiley‐Liss, Inc.     

Parallel‐transmission‐enabled three‐dimensional T2‐weighted imaging of the human brain at 7 Tesla

Purpose: A promise of ultra high field MRI is to produce images of the human brain with higher spatial resolution due to an increased signal to noise ratio. Yet, the shorter radiofrequency wavelength induces an inhomogeneous distribution of the transmit magnetic field and thus challenges the applicability of MRI sequences which rely on the spin excitation homogeneity. In this work, the ability of parallel‐transmission to obtain high‐quality T₂‐weighted images of the human brain at 7 Tesla, using an original pulse design method is evaluated. Methods: Excitation and refocusing square pulses of a SPACE sequence were replaced with short nonselective transmit‐SENSE pulses individually tailored with the gradient ascent pulse engineering algorithm, adopting a k_T‐point trajectory to simultaneously mitigate B₁⁺ and ΔB₀ nonuniformities. Results: In vivo experiments showed that exploiting parallel‐transmission at 7T with the proposed methodology produces high quality T₂‐weighted whole brain images with uniform signal and contrast. Subsequent white and gray matter segmentation confirmed the expected improvements in image quality. Conclusion: This work demonstrates that the adopted formalism based on optimal control, combined with the k_T‐point method, successfully enables three‐dimensional T₂‐weighted brain imaging at 7T devoid of artifacts resulting from B₁⁺ inhomogeneity. Magn Reson Med 73:2195–2203, 2015. © 2014 Wiley Periodicals, Inc.     

Contrast‐enhanced whole‐heart coronary MRI with bolus infusion of gadobenate dimeglumine at 1.5 T

We sought to investigate the T₁ kinetics of blood and myocardium after three infusion schemes of gadobenate dimeglumine (Gd‐BOPTA) and subsequently compared contrast‐enhanced whole‐heart coronary MRI after a bolus Gd‐BOPTA infusion with nonenhanced coronary MRI at 1.5 T. Blood and myocardium T₁ was measured in seven healthy adults, after each underwent three Gd‐BOPTA infusion schemes (bolus: 0.2 mmol/kg at 2 mL/sec, hybrid: 0.1 mmol/kg at 2 mL/sec followed by 0.1 mmol/kg at 0.1 mL/sec, and slow: 0.2 mmol/kg at 0.3 mL/sec). Fourteen additional subjects underwent contrast‐enhanced coronary MRI with an inversion‐recovery steady‐state free precession sequence after bolus Gd‐BOPTA infusion. Images were compared with nonenhanced T₂‐prepared steady‐state free precision whole‐heart coronary MRI in signal‐to‐noise ratio, contrast‐to‐noise ratio, depicted vessel length, vessel sharpness, and subjective image quality. Bolus and slow infusion schemes resulted in similar T₁ during coronary MRI, whereas the hybrid infusion method yielded higher T₁ values. A bolus infusion of Gd‐BOPTA significantly improved signal‐to‐noise ratio, contrast‐to‐noise ratio, depicted coronary artery length, and subjective image quality, when all segments were collectively compared but not when compared segment by segment. In conclusion, whole‐heart steady‐state free precision coronary MRI at 1.5 T can benefit from a bolus infusion of 0.2 mmol/kg Gd‐BOPTA. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.