On the cause of increased aliasing in the slice-select direction in 3D contrast-enhanced magnetic resonance angiography.

The combination of short repetition times and large flip angles typically used in 3D contrast-enhanced magnetic resonance angiography (3D CE MRA) can significantly alter the expected shape of the slab profile for unenhanced tissues, which can cause increased aliasing in the slice select direction. In this work, this increased slice select aliasing is demonstrated and explained from both theoretical and experimental points of view. The effect is due to the Ernst angle of unenhanced background tissue occurring on the falling edges of the flip angle profile that has been set for the significantly reduced T(1) of contrast-enhanced blood. The deleterious aliasing effects are magnified substantially when the chosen volume is placed close to surface coil reception with the slice select direction perpendicular to the coil axis. Magn Reson Med 44:336-338, 2000.     

T1rho imaging using magnetization-prepared projection encoding (MaPPE).

T1rho contrast weighting using a magnetization-prepared projection encoding (MaPPE) pulse sequence was investigated. Fast radial imaging was implemented by applying magnetization preparation pulses, each followed by multiple RF alpha pulses encoding radial trajectories of k-space. Acquiring multiple views per preparatory pulse imposes view-to-view variation; the resultant distortion of the point-spread function is examined. The issue of maximizing signal while preserving the intended contrast weighting is addressed. Under modification of repetition time and flip angle (alpha), three distinct behavior regimes of the sequence are identified. The utility of the pulse sequence as a quantitative relaxation measurement tool is also examined by comparing imaging and spectroscopy experiments. A mouse was imaged in vitro to demonstrate the viability of application to MR histology. These images exhibit the utility of spinlocking and projection encoding as an aftemative contrast source to both T2-weighted MaPPE images and conventional T2-weighted spin-echo images.     

Contrast-enhanced T1-weighted black-blood fast spin-echo MR imaging of the brain. Technique for suppression of enhancing venous signal

Purpose: Contrast-enhanced T1-weighted black-blood fast spin-echo MR imaging (BB-FSE) was performed to suppress enhancing venous signal and flow artifacts in the brain without sacrificing the T1-weighted imaging contrast.Material and Methods: Twenty-five MR imaging sections (17 transverse and 8 coronal images) in 15 patients with various brain diseases were obtained by contrast-enhanced T1-weighted SE and BB-FSE images.Results: In contrast-enhanced T1-weighted BB-FSE images, venous signal was significantly less and T1-weighted contrast of the brain was more evident. No differences in flow artifacts were found between the two imaging techniques. The interobserver agreements were good for the venous signal and flow artifacts using both techniques.Conclusion: Contrast-enhanced T1-weighted BB-FSE imaging reduced the venous signal in the brain with maintaining T1-weighted contrast. This novel MR technique can be used when the suppression of enhancing venous signal is expected to improve the depiction of enhancing lesions in the brain.     

Thermal lesion conspicuity following interstitial radiofrequency thermal tumor ablation in humans: a comparison of STIR, turbo spin-echo T2-weighted, and contrast-enhanced T1-weighted MR images at 0.2 T

The purpose of this study was to compare the contrast between radiofrequency (RF) thermal liver lesions and surrounding tissue in T2-weighted turbo spin-echo sequences (TSE T2), short TI inversion recovery techniques (STIR), and contrast-enhanced (CE) T1-weighted spin-echo images. Nineteen RF thermal ablations were performed on eight patients with metastatic liver tumors. After ablation, contrast-to-noise ratios (CNRs) were calculated between mean signal amplitudes from three regions of interest (ROI) (lesion, surrounding edema, and normal tissue) using TSE T2-weighted, STIR, and contrast-enhanced T1-weighted (CE T1) sequences for each lesion. CNRs between the thermal lesion and normal liver tissue for both TSE T2-weighted (mean 0.9) and STIR (2.0) images were significantly lower than for CE T1-weighted (8.4) images (t-test, alpha = 0.05). However, CNRs between edema rim and the core of the thermal lesion for both TSE T2-weighted (8.1) and STIR images (7.2) were not significantly different (t-test, alpha = 0.05) from CNRs between lesion and normal tissue for CE T1-weighted images (8.4), nor was the CNR between edema rim and normal tissue for both TSE T2-weighted (10.3) and STIR (9.8) images. Although the edema was not visible on CE T1-weighted images, 18 of 19 lesions (94.7%) were surrounded by a hyperintense rim on TSE T2-weighted or STIR images. Both TSE T2-weighted and STIR sequences represent valid techniques for repeatable assessment of RF thermal lesions.     

MR signal intensity characteristics in Legg-Calvé-Perthes disease. Value of fat-suppressed (STIR) images and contrast-enhanced T1-weighted images

PURPOSE: To evaluate the MR signal intensity characteristics in Legg-Calvé-Perthes disease on fat-suppressed (STIR) images and contrast-enhanced T1-weighted spin-echo images, and to develop criteria for the administration of contrast material. MATERIAL AND METHODS: Twenty children with Legg-Calvé-Perthes disease underwent conventional radiography and MR imaging of the hip utilizing fat-suppressed (STIR) sequences and T1-weighted spin-echo sequences before and after i.v. contrast administration. The signal intensity characteristics of the femoral head and the proximal femoral metaphysis were assessed retrospectively by two pediatric radiologists. RESULTS: Evaluation of the MR images revealed six different signal patterns within the femoral head: 1) isointense signal on all images; 2) complete signal void on all images; 3) hyperintense signal on STIR images with; or 4) without contrast enhancement on T1-weighted spin-echo images; 5) isointense signal on STIR images with; or 6) without contrast enhancement on T1-weighted images. Within the metaphysis three different signal patterns were differentiated. CONCLUSION: Combination of fat-suppressed (STIR) sequences and T1-weighted pre- and post-contrast sequences allows an accurate evaluation of Legg-Calvé-Perthes disease. In patients without signal alterations or complete signal loss on fat-suppressed and T1-weighted spin-echo images, administration of i.v. contrast is not necessary. In case of bone marrow edema on fat-supressed images, contrast-enhanced T1-weighted images are required to identify viable osseous fragments.     

Time-resolved, undersampled projection reconstruction imaging for high-resolution CE-MRA of the distal runoff vessels.

Imaging of the blood vessels below the knee using contrast-enhanced (CE) MRI is challenging due to the need to coordinate image acquisition and arrival of the contrast in the targeted vessels. Time-resolved acquisitions have been successful in consistently capturing images of the arterial phase of the bolus of contrast agent in the distal extremities. Although time-resolved exams are robust in this respect, higher spatial resolution for the depiction of tight stenoses and the small vessels in the lower leg is desirable. A modification to a high-spatial-resolution T(1)-weighted pulse sequence (projection reconstruction-time resolved imaging of contrast kinetics (PR-TRICKS)) that improves the through-plane spatial resolution by a factor of 2 and maintains a high frame rate is presented. The undersampled PR-TRICKS pulse sequence has been modified to double the spatial resolution in the slice direction by acquiring high-spatial-frequency slice data only after first pass of the bolus of contrast agent. The acquisition reported in the present work (PR-hyperTRICKS) has been used to image healthy volunteers and patients with known vascular disease. The temporal resolution was found to be beneficial in capturing arterial phase images in the presence of asymmetric filling of vessels.     

Hepatic MRI with SPIO: detection and characterization of focal liver lesions

A variety of parenterally administered iron oxides have been developed for contrast-enhanced MRI of the liver. Two different classes of iron oxides are currently clinically approved or in phase 3 trials: superparamagnetic iron oxides (SPIO) with a high R2/R1 relaxivity ratio and short blood half-life (AMI-25 and SH U 555 A), and ultrasmall paramagnetic iron oxides (USPIO) with a lower R2/R1 relaxivity ratio and longer blood half-life (AMI-227). All iron oxides significantly increase tumor-to-liver contrast and allow detection of more lesions than unenhanced MRI on T2-weighted images at a field strength of 0.2–1.5 T. Malignant lesions without phagocytic cells exhibit constant signal on T2-weighted accumulation phase images with all three iron oxides. All iron oxides cause a signal decrease of benign lesions with either phagocytic cells or a significant blood pool on T2-weighted accumulation phase images. The signal decrease of benign lesions is proportional to the Kupffer cell activity or tumor vascularity and is useful for lesion characterization. Another enhancement feature for the differentiation of benign from malignant lesions is ring enhancement of malignant lesions (metastases) on T1-weighted enhanced images either during the perfusion phase with SH U 555 A or during the accumulation phase with AMI-227, which is attributed to the blood pool effects of the compounds. Differentiation of lesions and vessels is easier on enhanced images with angiographic effects than on unenhanced images. Iron oxides improve the quality of two-dimensional MR angiography techniques of the portal venous system by decreasing background signal (liver tissue with all iron oxides) and increasing intravascular signal (AMI-227). The use of iron oxides for hepatic MRI provides an alternative to the existing multistep diagnosis with CT, CT portography, MRI and biopsy. Received: 24 September 1997; Revision received: 12 November 1997; Accepted: 14 November 1997     

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.     

Effect of multislice interference on image contrast in T2- and T1-weighted MR images

Multislice imaging markedly degrades the contrast of T2-weighted MR images as the separation between slices is reduced. Image contrast was measured clinically at 1.5 T and experimentally at 0.15 T as a function of interslice gap width and shown to be in agreement with calculations based on known relaxation times and excitation profiles. Thus, the cause of T2 contrast degradation in multislice sequences is demonstrated. Contrast in T1-weighted sequences is shown to be minimally affected or even slightly enhanced. Selective excitation pulses with better spatial definition will diminish these contrast changes. Since perfect slice profiles can never be achieved, the clinical implications of these findings are discussed for MR imaging. The choice of slice gaps is an important operator-selected parameter in reducing contrast degradation in T2-weighted sequences.     

Ultrasmall superparamagnetic iron-oxide-enhanced MR imaging of normal bone marrow in rodents: original research original research

RATIONALE AND OBJECTIVES: The objective is to compare three different ultrasmall superparamagnetic iron oxides (USPIOs) for magnetic resonance (MR) imaging of normal bone marrow in rodents. MATERIALS AND METHODS: Femoral bone marrow in 18 Sprague-Dawley rats was examined by using MR imaging before and up to 2 and 24 hours postinjection (PI) of 200 mumol of Fe/kg of SHU555C (n = 6), ferumoxtran-10 (n = 6), or ferumoxytol (n = 6), using T1-weighted (50 ms/1.7 ms/60 degrees = repetition time [TR]/echo time [TE]/flip angle) and T2*-weighted (100 ms/15 ms/38 degrees = TR/TE/flip angle) three-dimensional spoiled gradient recalled echo sequences. USPIO-induced bone marrow was evaluated qualitatively and quantified as signal-to-noise ratio (SNR) and change in signal intensity (DeltaSI) values. A mixed-effect model was fitted to the SNR and DeltaSI values, and differences among USPIOs were tested for significance by using F tests. RESULTS: At 2 hours PI, all three USPIOs showed marked positive signal enhancement on T1-weighted images and a corresponding marked signal loss on T2*-weighted images. At 24 hours PI, the T1 effect of all three USPIOs disappeared, whereas T2*-weighted images showed persistent signal loss on SHU555C and ferumoxytol-enhanced MR images, but not ferumoxtran-10-enhanced MR images. Corresponding SNR and DeltaSI values on T2*-weighted MR images at 24 hours PI were significantly different from baseline for SHU555C and ferumoxytol, but not ferumoxtran-10. CONCLUSION: All three USPIO contrast agents, ferumoxtran-10, ferumoxytol, and SHU555C, can be applied for MR imaging of bone marrow. Ferumoxtran-10 apparently reveals a different kinetic behavior in bone marrow than ferumoxytol and SHU555C.     

Characteristics and pitfalls of contrast-enhanced, T1-weighted magnetization transfer images of the brain

RATIONALE AND OBJECTIVES: This study was undertaken to clarify the difference in signal pattern on contrast material-enhanced T1-weighted magnetic resonance (MR) magnetization transfer (MT) images between enhancing and nonenhancing lesions in various intracranial diseases and to determine the necessity of nonenhanced MT images for evaluating lesional contrast enhancement. MATERIALS AND METHODS: MR images of 116 patients who underwent nonenhanced T1-weighted imaging, nonenhanced MT imaging, and contrast-enhanced MT imaging were reviewed. The increase in signal intensity of lesions relative to normal brain was compared between nonenhanced T1-weighted images and contrast-enhanced MT images. Signal intensity of lesions was compared with that of the striate nucleus and white matter on contrast-enhanced MT images. True enhancement was determined by comparison with nonenhanced MT images. RESULTS: In all, 143 lesions, including 86 enhancing and 57 nonenhancing lesions, were identified among 63 patients. Almost all (99%) of the enhancing lesions were hyperintense to striate nucleus on contrast-enhanced MT images, and most (>87%) showed moderate to marked signal intensity increase from nonenhanced T1-weighted images to contrast-enhanced MT images. Most (>95%) of the nonenhancing lesions showed mild or no increase in relative signal intensity, and most (75%) were iso- or hypointense to striate nucleus on contrast-enhanced MT images. A few nonenhancing lesions (4%-6%), however, showed increase in signal intensity that was indistinguishable from true enhancement without comparison to non-enhanced MT images. CONCLUSION: Nonenhanced MT images should be obtained to assess pathologic enhancement accurately.     

Evaluation of crosstalk effect on spin-echo images at 1.5 and 3 T

The purpose of this study is to evaluate the crosstalk effect on spin-echo (SE) images at 1.5 and 3 T MRI. We examined the influence of crosstalk by comparing the full width at half-maximum (FWHM) and slice profile of images of a wedge-shaped phantom for various slice gaps. We also assessed crosstalk effect in the brain by comparing image contrast among healthy volunteers (n=8). Among the subjects, the shapes of the slice profiles at 1.5 T were similar to those at 3 T for long repetition times (TRs); however, at shorter TRs, differences in slice profiles were observed among the subjects and were more apparent at 3 than at 1.5 T. The relative contrast between white matter and gray matter on T(1)-weighted images was lower at 3 than at 1.5 T. The crosstalk effect was strongest when the TR of the excitation pulse was short. The influence of the adjacent excitation pulse is important in the process of T(1) relaxation because T(1) values are greater at 3 T. In conclusion, the influence of crosstalk on SE T(1)-weighted images is greater at 3 than at 1.5 T.     

Lymph nodes of the neck. Diagnosis using magnetic resonance with gradient-echo technique

As for the pathologic conditions of neck lymph nodes, the clinician needs to know if the involved node is reactive, phlogistic, or neoplastic in nature. If accurate tumor staging is required, imaging techniques play a fundamental role. Our study was aimed at assessing the actual role of MR imaging in the evaluation of neck lymph node involvement. The study was performed using an MR Max Plus by General Electrics operating with an 0.5 T superconductive magnet. We employed gradient-echo (GE) pulse sequences with TR 500, TE 15 ms and 90 degrees flip angle for T1-weighted images, and with TR 500, TE 30 ms and 25-30 degrees flip angles for T2-weighted images; for Pd-T2-weighted images, TR was 520, TE 30 ms, and flip angles were 40-45 degrees. The results were correlated with histopathologic findings obtained at biopsy. The advantages of GE sequences were: 1) whole neck imaging--thus saving time, and reducing radiation dose and contrast media; 2) optimal anatomical and topographic evaluation of the lesion; 3) imaging of the longitudinal diameter of the node; 4) higher sensitivity for lymph node tissue modifications; 5) imaging of necrosis, hemorrhage, and/or fibrosis. GE sequences were especially useful for accurate tumor staging, in the follow-up, and to verify response to therapy. However, even though MR imaging has proven to have high sensitivity, its specificity was similar to that of contrast-enhanced CT. Further studies with the use of paramagnetic contrast media are needed to solve these problems.     

Anterior and posterior lobes of the pituitary gland: assessment by 1.5 T MR imaging

Pituitary glands of 60 normal volunteers (30 men 20-36 years old, and 30 women 18-42 years old) were studied by 1.5 T magnetic resonance (MR) imaging. The T1-weighted images (T1WI) [repetition time (TR) = 400 ms; echo time (TE) = 25 ms] were obtained in the coronal, sagittal, and axial planes. Proton density (PD)/T2-weighted images (PDWI/T2WI) (TR = 2,000 ms; TE = 25/100 ms) were obtained in the sagittal plane using 3 mm slice thickness. On T1WIs of all subjects the posterior part (PP) of the pituitary fossa showed the highest signal, which was indistinguishable from fatty tissue. This study reveals that this region of high signal intensity (PP) corresponds to the posterior lobe and not intrasellar fat because its shape, size, and position are compatible with the posterior lobe; its signal intensity differs from that of fatty tissue on PDWI and T2WI; the absence of an intrinsic chemical shift artifact (CSA) characteristic of fat; and due to CSA, a dorsum with fatty marrow is shifted relative to the PP (or may be made to merge with it). Regarding the differentiation of the two lobes of the pituitary gland on MR, the morphology of the anterior and posterior lobes was evaluated and great variation found. Appreciation of normal is particularly important in evaluating coronal images for small pituitary lesions.     

Dynamic MR venography: an intrinsic benefit of time-resolved MR angiography

PURPOSE: To investigate the possibility of obtaining dynamic contrast-enhanced magnetic resonance venography (DCE-MRV) images of the lower extremities. MATERIALS AND METHODS: Peripheral contrast-enhanced magnetic resonance angiography (CE-MRA) was performed on 20 patients using a time-resolved sequence that combined undersampled projection reconstruction (PR) in-plane and Cartesian slice encoding through-plane. The contrast dynamics of distal vessels were depicted. An automated segmentation algorithm based on a contrast arrival time (CAT) threshold was used to generate contrast dynamics in the venous system. The signal difference between the vein and artery was measured to evaluate the effectiveness of this technique in isolating the venous contrast dynamics. RESULTS: The automatically generated image series depicted the contrast dynamics of both the arterial and venous systems, including asymmetric venous enhancement and background tissue enhancement. Quantitative measurement showed a mean venous/arterial signal ratio increase from 1.58 to 4.82 for the peak venous frame after arterial signal suppression. CONCLUSION: DCE-MRV is a minimally invasive technique for evaluating the venous side of the systemic vascular anatomy. Time-resolved MRA has the potential clinical benefit of enabling both arterial and venous disease to be detected in patients undergoing CE-MRA.     

Comparison of four magnetization preparation schemes to improve blood-wall contrast in cine short-axis cardiac imaging

Improvements in short-axis blood-myocardium contrast in the heart with the use of four magnetization preparation schemes applied before the imaging sequence are demonstrated. Gradient-echo cine cardiac images are acquired and compared at 0.95 T incorporating T₂, T_1p, magnetization transfer, and double inversion (black blood) preparations in a series of volunteer studies over the first 550 ms of the cardiac cycle. T₂ and T_1p preparations exhibit improvements of 100% and above in image contrast. Magnetization transfer preparation exhibits improvements of 50% in image contrast, whereas an initial improvement (50%) followed by a large loss in contrast is observed using the black blood preparation. Improvements in contrast are dependent on tissue relaxation parameters and therefore are suitable for studies involving patients exhibiting poor in-flow enhancement of blood caused by poor heart function.     

Improved detection of enhancing and nonenhancing lesions of multiple sclerosis with magnetization transfer.

PURPOSETo determine whether magnetization transfer imaging can improve visibility of contrast enhancement of multiple sclerosis plaques.METHODSFifty-nine enhancing and 63 nonenhancing lesions in 10 patients with multiple sclerosis were evaluated to calculate contrast-to-noise ratios on conventional T1-weighted and T1-weighted magnetization transfer images. The signal intensity of the lesion and the background (white matter) were measured on precontrast T1-weighted and T1-weighted magnetization transfer images (800/20/1 [repetition time/echo time/excitations]) and on postcontrast T1-weighted and T1-weighted magnetization transfer images. Mean contrast-to-noise ratios was calculated for all lesions.RESULTSThe contrast-to-noise ratio was significantly higher for enhancing and nonenhancing lesions on T1-weighted magnetization transfer images than on conventional T1-weighted images. For enhancing lesions, the contrast-to-noise ratio was significantly higher on postcontrast T1-weighted magnetization transfer images, 32 +/- 2 compared with 21 +/- 2 on conventional T1-weighted images. Fifty of the 59 enhancing lesions were seen on both the T1-weighted and the T1-weighted magnetization transfer images. Nine enhancing lesions were seen only on the postcontrast T1-weighted magnetization transfer images. In addition, of 63 nonenhancing lesions seen on proton-density, T2-weighted, and T1-weighted magnetization transfer images, 16 were not seen on the conventional T1-weighted images. Seven of the 63 nonenhancing lesions and 7 of the 59 enhancing lesions had high signal intensity on the precontrast T1-weighted magnetization transfer images suggestive of lipid signal, a finding not seen on the conventional precontrast T1-weighted images.CONCLUSIONMagnetization transfer improves the visibility of enhancing multiple sclerosis lesions, because they have a higher contrast-to-noise ratio than conventional postcontrast T1-weighted images. High signal intensity on both nonenhancing and enhancing lesions noted only on precontrast T1-weighted magnetization transfer suggests a lipid signal was unmasked. If magnetization transfer is used in multiple sclerosis patients, a precontrast magnetization transfer image is necessary.     

3D MDEFT imaging of the human brain at 4.7 T with reduced sensitivity to radiofrequency inhomogeneity.

A modification to the 3D modified driven equilibrium Fourier transform (MDEFT) imaging technique is proposed that reduces its sensitivity to RF inhomogeneity. This is especially important at high field strengths where RF focusing effects exacerbate B(1) inhomogeneity, causing significant signal nonuniformity in the images. The adiabatic inversion pulse used during the preparation period of the MDEFT sequence is replaced by a hard (nonadiabatic) pulse with a nominal flip angle of 130 degrees. The spatial inhomogeneity of the hard pulse preparation compensates for the inhomogeneity of the excitation pulses. Uniform signal intensity is obtained for a wide range of B(1) amplitudes and the high CNR characteristic of MDEFT is retained. The new approach was validated by numerical simulations and successfully applied to human brain imaging at 4.7 T, resulting in high-quality T(1)-weighted images of the whole human brain at high field strength with uniform signal intensity and contrast, despite the presence of significant RF inhomogeneity.     

Advanced three-dimensional tailored RF pulse for signal recovery in T2*-weighted functional magnetic resonance imaging.

T(2) (*)-weighted functional MR images are plagued by signal loss artifacts caused by susceptibility-induced through-plane dephasing. We present major advances to the original three-dimensional tailored RF (3DTRF) pulse method that pre-compensates the dephasing using three-dimensional selective excitation. The proposed 3DTRF pulses are designed iteratively with off-resonance incorporation and with a novel echo-volumar trajectory that frequency-encodes in z and phase-encodes in x,y. We also propose a computational scheme to accelerate the pulse design process. We demonstrate effective signal recovery in a 5-mm slice in both phantom and inferior brain, using 3DTRF pulses that are only 15.4 ms long. Compared to the original method, the new approach leads to significantly reduced pulse length and enhancement in slice selectivity. 3D images of the slice volume confirm fidelity of the excited phase pattern and slice profile.     

T2 measurement of the human myocardium using a T2-prepared transient-state TrueFISP sequence.

A fast and motion-insensitive technique suitable for myocardial BOLD contrast imaging is presented. The method, termed T2-TrueFISP, combines T2 magnetization preparation with steady-state free precession (SSFP) imaging for T2 relaxation mapping of the myocardium in healthy volunteers. The T2 contrast-to-noise ratio (CNR) was optimized with the use of transient-state TrueFISP readout and half-Fourier readout with linear phase encoding. Single-slice myocardial T2-weighted image was obtained within one heartbeat, and a single slice T2 map of the myocardium was obtained in under 5-7 s. A respiratory navigator-gating method was incorporated for serial measurements and signal averaging, with the subjects breathing freely. The mean myocardial T2 relaxation time measured in 12 healthy volunteers was 54 +/- 5.7 ms. Regional variations of T2 values across the myocardium were 7%. Temporal variations across serial T2 measurements in a transmural region covering approximately 0.5 cc of the left ventricular (LV) wall were 3.6% without signal averaging (number of excitations (NEX) = 1) and 1.7% with signal averaging (NEX = 10). According to our preliminary results, the T2-TrueFISP method is expected to provide a robust and sensitive tool for clinical application of myocardial BOLD contrast imaging.