Showing papers on "Steady-state free precession imaging published in 2011"

Cardiovascular magnetic resonance myocardial feature tracking detects quantitative wall motion during dobutamine stress

Abstract: Dobutamine stress cardiovascular magnetic resonance (DS-CMR) is an established tool to assess hibernating myocardium and ischemia. Analysis is typically based on visual assessment with considerable operator dependency. CMR myocardial feature tracking (CMR-FT) is a recently introduced technique for tissue voxel motion tracking on standard steady-state free precession (SSFP) images to derive circumferential and radial myocardial mechanics. We sought to determine the feasibility and reproducibility of CMR-FT for quantitative wall motion assessment during intermediate dose DS-CMR. 10 healthy subjects were studied at 1.5 Tesla. Myocardial strain parameters were derived from SSFP cine images using dedicated CMR-FT software (Diogenes MRI prototype; Tomtec; Germany). Right ventricular (RV) and left ventricular (LV) longitudinal strain (EllRV and EllLV) and LV long-axis radial strain (ErrLAX) were derived from a 4-chamber view at rest. LV short-axis circumferential strain (EccSAX) and ErrSAX; LV ejection fraction (EF) and volumes were analyzed at rest and during dobutamine stress (10 and 20 μg · kg-1· min-1). In all volunteers strain parameters could be derived from the SSFP images at rest and stress. EccSAX values showed significantly increased contraction with DSMR (rest: -24.1 ± 6.7; 10 μg: -32.7 ± 11.4; 20 μg: -39.2 ± 15.2; p < 0.05). ErrSAX increased significantly with dobutamine (rest: 19.6 ± 14.6; 10 μg: 31.8 ± 20.9; 20 μg: 42.4 ± 25.5; p < 0.05). In parallel with these changes; EF increased significantly with dobutamine (rest: 56.9 ± 4.4%; 10 μg: 70.7 ± 8.1; 20 μg: 76.8 ± 4.6; p < 0.05). Observer variability was best for LV circumferential strain (EccSAX ) and worst for RV longitudinal strain (EllRV) as determined by 95% confidence intervals of the difference. CMR-FT reliably detects quantitative wall motion and strain derived from SSFP cine imaging that corresponds to inotropic stimulation. The current implementation may need improvement to reduce observer-induced variance. Within a given CMR lab; this novel technique holds promise of easy and fast quantification of wall mechanics and strain.

Cardiac magnetic resonance imaging findings in 20-year survivors of mediastinal radiotherapy for hodgkin's disease

Abstract: Purpose The recognition of the true prevalence of cardiac toxicity after mediastinal radiotherapy requires very long follow-up and a precise diagnostic procedure. Cardiac magnetic resonance imaging (MRI) permits excellent quantification of cardiac function and identification of localized myocardial defects and has now been applied to a group of 20-year Hodgkin's disease survivors. Methods and materials Of 143 patients treated with anterior mediastinal radiotherapy (cobalt-60, median prescribed dose 40 Gy) for Hodgkin's disease between 1978 and 1985, all 53 survivors were invited for cardiac MRI. Of those, 36 patients (68%) presented for MRI, and in 31 patients (58%) MRI could be performed 20-28 years (median, 24) after radiotherapy. The following sequences were acquired on a 1.5-T MRI: transversal T1-weighted TSE and T2-weighted half-fourier acquisition single-shot turbo-spin-echo sequences, a steady-state free precession (SSFP) cine sequence in the short heart axis and in the four-chamber view, SSFP perfusion sequences under rest and adenosine stress, and a SSFP inversion recovery sequence for late enhancement. The MRI findings were correlated with previously reconstructed doses to cardiac structures. Results Clinical characteristics and reconstructed doses were not significantly different between survivors undergoing and not undergoing MRI. Pathologic findings were reduced left ventricular function (ejection fraction Conclusions In 20-year survivors of Hodgkin's disease, cardiac MRI detects pathologic findings in approximately 70% of patients. Cardiac MRI has a potential role in cardiac imaging of Hodgkin's disease patients after mediastinal radiotherapy.

CAIPIRINHA accelerated SSFP imaging

Abstract: Exciting multiple slices at the same time, “controlled aliasing in parallel imaging results in higher acceleration” (CAIPIRINHA) and “phase-offset multiplanar” have shown to be very effective techniques in 2D multislice imaging. Being provided with individual rf phase cycles, the simultaneously excited slices are shifted with respect to each other in the FOV and, thus, can be easily separated. For SSFP sequences, however, similar rf phase cycles are required to maintain the steady state, impeding a straightforward application of phase-offset multiplanar or controlled aliasing in parallel imaging results in higher acceleration. In this work, a new flexible concept for applying the two multislice imaging techniques to SSFP sequences is presented. Linear rf phase cycles are introduced providing both in one, the required shift between the slices and steady state in each slice throughout the whole measurement. Consequently, the concept is also appropriate for real-time and magnetization prepared imaging. Steady state properties and shifted banding behavior of the new phase cycles were investigated using simulations and phantom experiments. Moreover, the concept was applied to perform whole heart myocardial perfusion SSFP imaging as well as real-time and cine SSFP imaging with increased coverage. Showing no significant penalties in SNR or image quality, the results successfully demonstrate the general applicability of the concept. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.

Automated estimation of aortic strain from steady-state free-precession and phase contrast MR images.

Abstract: The strain values extracted from steady-state free-precession (SSFP) and phase contrast (PC) images acquired with a 1.5T scanner on a compliant flow phantom and within the thoracic aorta of 52 healthy subjects were compared. Aortic data were acquired perpendicular to the aorta at the level of the pulmonary artery bifurcation. Cross sectional areas were obtained by using an automatic and robust segmentation method. While a good correlation (r = 0.99) was found between the aortic areas extracted from SSFP and PC sequences, a lower correlation (r = 0.71) was found between the corresponding aortic strain values. Strain values estimated using SSFP and PC sequences were equally correlated with age. Interobserver reproducibility was better for SSFP than for PC. Strain values in the ascending and descending aorta were better correlated for SSFP (r = 0.8) than for PC (r = 0.65) and fitted with the expectation of a larger strain in the ascending aorta when using SSFP. The spatial and temporal resolutions of the acquisitions had a minor influence upon the estimated strain values. Thus, if PC acquisitions can be used to estimate both pulse wave velocity and aortic strain, an additional SSFP sequence may be useful to improve the accuracy in estimating the aortic strain.

Congenital heart disease: cardiovascular MR imaging by using an intravascular blood pool contrast agent.

Abstract: In this study, an inversion-recovery steady-state free precession (SSFP) MR imaging sequence with gadofosveset trisodium showed improved image quality and diagnostic performance in the assessment of cardiovascular morphology in patients with complex congenital heart disease compared with a T2-prepared SSFP sequence with gadopentetate dimeglumine and gadofosveset trisodium and respective contrast-enhanced MR angiographic examinations.

Quantitative mapping of T2 using partial spoiling

Abstract: 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.

Layer-specific functional and anatomical MRI of the retina with passband balanced SSFP.

Abstract: The retina consists of multiple cellular and synaptic layers and is nourished by two distinct (retinal and choroidal) circulations bounding the retina, separated by an avascular layer. High spatiotemporal resolution, layer-specific MRI of the retina remains challenging due to magnetic inhomogeneity-induced artifacts. This study reports passband balanced steady-state free-precession (bSSFP) MRI at 45×45×500 μm and 1.6 s temporal resolution to image the mouse retina, overcoming geometric distortion and signal dropout while maintaining rapid acquisition and high signal-to-noise ratio. bSSFP images revealed multiple alternating dark-bright-dark-bright retinal layers. Hypoxic (10% O(2) ) inhalation decreased bSSFP signals in the two layers bounding the retina, corresponding to the retinal and choroidal vasculatures. The layer in between showed no substantial response and was assigned the avascular photoreceptor layers. Choroidal responses (-25.9 ± 6.4%, mean ± SD, n=6) were significantly (P<0.05) larger than retinal vascular responses (-11.6±2.4%). bSSFP offers very high spatiotemporal resolution and could have important applications in imaging layer-specific changes in retinal diseases.

Self-gating MR imaging of the fetal heart: comparison with real cardiac triggering

Abstract: To investigate the self-gating technique for MR imaging of the fetal heart in a sheep model. MR images of 6 fetal sheep heart were obtained at 1.5T. For self-gating MRI of the fetal heart a cine SSFP in short axis, two and four chamber view was used. Self-gated images were compared with real cardiac triggered MR images (pulse-wave triggering). MRI of the fetal heart was performed using both techniques simultaneously. Image quality was assessed and the left ventricular volume and function were measured and compared. Compared with pulse-wave triggering, the self-gating technique produced slightly inferior images with artifacts. Especially the atrial septum could not be so clearly depicted. The contraction of the fetal heart was shown in cine sequences in both techniques. The average blood volumes could be measured with both techniques with no significant difference: at end-systole 3.1 ml (SD± 0.2), at end-diastole 4.9 ml (±0.2), with ejection fractions at 38.6%, respectively 39%. Both self-gating and pulse-wave triggered cardiac MRI of the fetal heart allowed the evaluation of anatomical structures and functional information. Images obtained by self-gating technique were slightly inferior than the pulse-wave triggered MRI.

Temporal diffeomorphic free form deformation (TDFFD) applied to motion and deformation quantification of tagged MRI sequences

Abstract: This paper presents strain quantification results obtained from the Tagged Magnetic Resonance Imaging (TMRI) sequences acquired for the 1st cardiac Motion Analysis Challenge (cMAC). We applied the Temporal Diffeomorphic Free Form Deformation (TDFFD) algorithm to the phantom and the 15 healthy volunteers of the cMAC database. The TDFFD was modified in two ways. First, we modified the similarity metric to incorporate frame to frame intensity differences. Second, on volunteer sequences, we performed the tracking backward in time since the first frames did not show the contrast between blood and myocardium, making these frames poor choices of reference. On the phantom, we propagated a grid adjusted to tag lines to all frames for visually assessing the influence of the different algorithmic parameters. The weight between the two metric terms appeared to be a critical parameter for making a compromise between good tag tracking while preventing drifts and avoiding tag jumps. For each volunteer, a volumetric mesh was defined in the Steady-State Free Precession (SSFP) image, at the closest cardiac time from the last frame of the tagging sequence. Uniform strain patterns were observed over all myocardial segments, as physiologically expected.

Magnetization-Prepared IDEAL bSSFP: A Flow-Independent Technique for Noncontrast-Enhanced Peripheral Angiography

Abstract: Purpose: To propose a new noncontrast-enhanced flow-independent angiography sequence based on balanced steady-state free precession (bSSFP) that produces reliable vessel contrast despite the reduced blood flow in the extremities. Materials and Methods: The proposed technique addresses a variety of factors that can compromise the exam success including insufficient background suppression, field inhomogeneity, and large volumetric coverage requirements. A bSSFP sequence yields reduced signal from venous blood when long repetition times are used. Complex-sum bSSFP acquisitions decrease the sensitivity to field inhomogeneity but retain phase information, so that data can be processed with the Iterative Decomposition of Water and Fat with Echo Asymmetry and Least-Squares Estimation (IDEAL) method for robust fat suppression. Meanwhile, frequent magnetization preparation coupled with parallel imaging reduces the muscle and long-T1 fluid signals without compromising scan efficiency. Results: In vivo flow-independent peripheral angiograms with reliable background suppression and high spatial resolution are produced. Comparisons with phase-sensitive bSSFP angiograms (that yield out-of-phase fat and water signals, and exploit this phase difference to suppress fat) demonstrate enhanced vessel depiction with the proposed technique due to reduced partial-volume effects and improved venous suppression. Conclusion: Magnetization-prepared complex-sum bSSFP with IDEAL fat/water separation can create reliable flow-independent angiographic contrast in the lower extremities. J. Magn. Reson. Imaging 2011;33:931–939. © 2011 Wiley-Liss, Inc.

Cardiac MRI: Part 1, cardiovascular shunts

Abstract: OBJECTIVE. MRI plays an important role in the morphologic and functional evaluation of cardiovascular shunts. Good spatiotemporal resolution, inherent contrast resolution, wide FOV, and multiplanar imaging capabilities make MRI an ideal tool in the investigation of cardiovascular shunts. The velocity-encoded phase-contrast sequence is used in the quantification of a shunt and the steady-state free precession (SSFP) sequence is used in the assessment of the functional impact of a shunt. In this article, the role of MRI in the evaluation of cardiovascular shunts and their respective MRI appearances are described and illustrated. CONCLUSION. MRI can identify and characterize septal defects, quantify shunts and their impact on cardiac function, and help in the selection of appropriate candidates for percutaneous device placement.

In vivo single scan detection of both iron-labeled cells and breast cancer metastases in the mouse brain using balanced steady-state free precession imaging at 1.5 T.

Abstract: THE INCIDENCE OF BREAST CANCER patients with brain metastases is increasing (1,2). This is due in part to the pharmaceutical focus on development of therapeutic agents that successfully treat systemic, but not brain metastases. Still, the median survival time with aggressive treatment is extended by only 4–12 months. To study the mechanisms of breast cancer metastasis to the brain, mouse models have been developed using human breast cancer cell lines (3,4). Histology, immunohistochemistry, and microscopy are typically used to estimate the numbers and the cross-sectional area of metastases, and for analysis of cellular markers (5–7). The limitations of these methods are the need to sacrifice the animal, allowing only an endpoint analysis, and the small subset of tissue volume assessed. Microimaging technologies, including high-resolution magnetic resonance imaging (MRI), micro-computed tomography, and positron emission tomography have shown great utility for characterizing small-animal models of disease. MRI is particularly well suited for studies of brain metastasis because it is noninvasive, three-dimensional, has excellent soft-tissue contrast, and no limitation in depth of penetration at clinical magnetic field strengths. Cellular MRI combines the use of high-resolution MRI with cell labels to track cells of interest. The most commonly used labels are iron-based nanoparticles including superparamagnetic, ultrasmall, and micron-sized iron oxide particles (MPIO). Stem cells (8), macrophages (9), dendritic cells (10), cancer cells (11), and lymphocytes (12) have been tracked in vivo with MRI using this approach. The presence of the label causes a distortion in the magnetic field and leads to abnormal signal hypointensities in iron-sensitive images. Most studies have employed T2-weighted (T2w) spin echo, and T2*-weighted gradient echo sequences to detect iron-labeled cells. The balanced steady-state free precession (b-SSFP) imaging sequence has been used to detect single iron-labeled macrophages and cancer cells in vivo as signal voids in the mouse brain (11,13). The major advantage of the b-SSFP sequence is its high signal-to-noise ratio (SNR) efficiency, allowing for imaging at high spatial resolution in reasonable scan times (14). Another important feature of b-SSFP is its high sensitivity to magnetic field inhomogeneities (15,16). Miraux et al (17) also investigated the b-SSFP sequence on mouse brains at 4.7 and 9.4 T. They compared b-SSFP images of implanted gliomas with T2w SE images, the most commonly employed contrast for the visualization of brain tumors in mice. At 4.7 T the SNR and brain-to-tumor contrast-to-noise ratio (CNR) were comparable in b-SSFP and T2w images, but the scan time was ≈4 times shorter with b-SSFP. At 9.4 T, the CNR was attenuated and tumors were barely visible. Bernas et al (18) developed a b-SSFP protocol at 3 T to optimally visualize iron-loaded glioma in the mouse brain. This protocol consists of a set of two b-SSFP image acquisitions with complementary contrasts, allowing delineation of tumors, which appear as regions of signal hyperintensity due to longer T2 of tumor tissue compared to brain parenchyma, and providing high sensitivity to iron-labeled cells, which are detected as regions of signal void. The purpose of this study was to optimize b-SSFP at 1.5 T with the goal of generating image contrast for the simultaneous detection of single iron-labeled cancer cells and brain tumors in vivo in one scan. A single scan would reduce the acquisition time and allow for monitoring of both nonproliferative cancer cells and developing metastases. For this purpose, MPIO-labeled cancer cells were injected into the left ventricle of the heart in nude mice. After intracardiac injection, cells become trapped in the brain microvasculature. With time, some cancer cells proliferate into metastases that appear as regions of signal hyperintensity in b-SSFP images, primarily due to increased T2 relaxation, while other cells remain dormant (nonproliferative) and are detected as persistent signal voids (11).

Noncontrast MR Angiography for Comprehensive Assessment of Abdominopelvic Arteries using Quadruple Inversion-Recovery Preconditioning and 3D balanced Steady-State Free Precession Imaging

Abstract: Purpose To develop a non-contrast MR angiography (MRA) method for comprehensive evaluation of abdominopelvic arteries in a single 3D acquisition.

Quantitative analysis of the diffusion-weighted steady-state free precession signal in vertebral bone marrow lesions.

Abstract: water , , S S accord- ing to (5), which depend on the relaxation times, T1 and T2, and the ADCs of both signal components as well as on the sequence parameters (repetition time TR, diffusion gradient shape, and the flip angle). Methods: MRI was performed on a 1.5-T whole-body scanner in 40 patients with benign (n=20) or malignant (n=20) VLs to determine the fat fraction and tissue parameters (ADC, T1, T2, T2 * ) for both the water and fat signal component (using single-shot turbo-spin-echo (ssTSE) sequences for ADC, T1, and T2 quanti- fication, and gradient-echo sequences for fat-fraction and T2 * quantification). With these values, the DW-SSFP signal was simulated and compared with the measured signals (PSIF diffusion sequence: TE = 7.17 ms, TR = 25 ms, flip angle 40°; diffusion gradient 23 mT⁄m, duration δ = 0.5,1.5,3.0,5.0,7.4 ms) for different diffusion gradients. Simulations and measurement results were compared by determining the signal ratios RVL between the SSFP signals of the lesions and of normal-appearing VBM for both malignant and benign vertebral lesions. Results: The simulated DW-SSFP contrast agreed well with the measured con- trast (cf. Fig. 1) and provided a very good differentiation between benign osteopo- rotic and malignant VLs with a sensitivity of up to 95% and a specificity of 100%. ADCs were significantly different in both lesion types; however, the great- est contributions to the observed total image contrast resulted from the differences (between both patient groups) of ffat in the lesions as well as in normal-appearing VBM, of T * 2,fat in normal-appearing VBM, and of T * 2,water in the lesions (cf. Fig. 2). Smaller effects are caused by the differences of T1,fat and T2,fat in normal- appearing VBM and (with opposite sign) of T2,water in the lesions. The other para- meter differences do not contribute substantially to the observed contrast. Conclusions: In this study, we could confirm previous results that the DW- SSFP sequence provides an excellent differentiation between benign osteoporotic and malignant VLs. We could also show that the main reasons for the different lesion contrasts (hypo-/isointense vs. hyperintense signal) are an opposed-phase readout in combination with the differing fat fractions and T2 * -values in the le- sions as well as in normal-appearing VBM of both entities. The observed signal contrast is therefore rather fat- and T2 * -weighted than diffusion-weighted. The intermediate diffusion weighting of the applied SSFP sequence, however, helps to shift the different contrasts into a signal range that is easily visually accessible.

MRI for detection of anomalous pulmonary venous drainage in patients with sinus venosus atrial septal defects

Abstract: Purpose of this survey was to estimate the value of MRI for the assessment of the anatomical and functional features of sinus venosus atrial septal defect (SVD). This prospective study included 13 surgically proven cases of SVD out of 81 subjects submitted to MRI due to inconclusive transthoracic echocardiography (TTE) or suspicion of high intracardiac and/or extracardiac shunt volumes based on echocardiographic findings. MRI examination included cine SSFP sequences, contrast-enhanced 3D gradient-echo (GE) sequences for MR angiography (MRA) and phase-contrast flow-measurements. MRI revealed nine patients with a superior and four with an inferior SVD. Anomalous pulmonary venous drainage (APVD) was observed only in subjects with a superior SVD, and it was right-sided in all cases. All MRI and MRA results for the SVD patients were confirmed intraoperatively. The Correlation coefficient between MR flow measurements and cardiac catheterisation was 0.94 (P < 0.0001). According to MRI the rest of the subjects (n = 68) presented a secundum ASD, whereas in 18% an APVD coexisted. The latter MR outcomes concurred with the cardiac catheterisation (n = 56) and operative (n = 12) results. MRI provides a reliable, non-invasive method for evaluation of SVDs, APVDs and shunt quantification.

Influence of MT effects on T2 quantification with 3D balanced steady-state free precession imaging

Abstract: Signal from balanced steady-state free precession is affected by magnetization transfer. To investigate the possible effects on derived T2 values using variable nutation steady-state free precession, magnetization transfer-effects were modulated by varying the radiofrequency pulse duration only or in combination with variable pulse repetition time. Simulations reveal a clear magnetization transfer dependency of T2 when decreasing radiofrequency pulse duration, reaching maximal deviation of 34.6% underestimation with rectangular pulses of 300 μs duration. The observed T2 deviation evaluated in the frontal white matter and caudate nucleus shows a larger underestimation than expected by numerical simulations. However, this observed difference between simulation and measurement is also observed in an aqueous probe and can therefore not be attributed to magnetization transfer: it is an unexpected sensitivity of derived T2 to radiofrequency pulse modulation. As expected, the limit of sufficiently long radiofrequency pulse duration to suppress magnetization transfer-related signal modulations allows for proper T2 estimation with variable nutation steady-state free precession. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc.

Noncontrast magnetic resonance angiography of the hand: improved arterial conspicuity by multidirectional flow-sensitive dephasing magnetization preparation in 3D balanced steady-state free precession imaging.

Abstract: Purpose To develop a flow-sensitive dephasing (FSD) preparative scheme to facilitate multi-directional flow signal suppression in three-dimensional balanced steady-state free precession (SSFP) imaging and to validate the feasibility of the refined sequence for noncontrast MR angiography (NC-MRA) of the hand

A multimodal database for the 1st cardiac motion analysis challenge

Abstract: This paper describes the acquisition of the multimodal database used in the 1st Cardiac Motion Analysis Challenge The database includes magnetic resonance (MR) and 3D ultrasound (3DUS) datasets from a dynamic phantom and 15 datasets from healthy volunteers The MR acquisition included cine steady state free precession (SSFP), whole-heart turbo field echo (TFE), and 4D tagged MR (tMR) sequences From the SSFP images, the end diastolic anatomy was extracted using a deformable model of the left ventricle (LV) The LV model was mapped to the tMR coordinates using DICOM information From the LV model, 12 landmarks were generated (4 walls at 3 ventricular levels) These landmarks were manually tracked in the tMR data over the whole cardiac cycle by two observes using an in-house application with 4D visualization capabilities Finally, the LV model was registered to the 3DUS coordinates using a point based similarity transform Four institutions responded to the challenge by providing motion estimates for the data Preliminary results are presented for one of the volunteer data sets

Steady-state MRI: methods for neuroimaging

Abstract: MRI pulse sequences that use regularly spaced trains of rapidly applied excitation pulses (every few milliseconds) are known as ‘steady-state’ sequences Under these conditions, the magnetization evolves into a steady state that depends on tissue parameters such as T1, T2 and diffusion, as well as sequence parameters such as repetition time and flip angle These sequences have attractive properties including high efficiency (in terms of signal-to-noise ratio) and flexible image contrast; they also create unique challenges due to the need to maintain the magnetization in the steady state and their complicated signal dependence This article describes the primary types of steady-state sequences and their application to brain imaging

Comparison of intravascular and extracellular contrast media for absolute quantification of myocardial rest-perfusion using high-resolution MRI.

Abstract: Purpose: To use the contrast agent gadofosveset for absolute quantification of myocardial perfusion and compare it with gadobenate dimeglumine (Gd-BOPTA) using a high-resolution generalized autocalibrating partially parallel acquisition (GRAPPA) sequence. Materials and Methods: Ten healthy volunteers were examined twice at two different dates with a first-pass perfusion examination at rest using prebolus technique. We used a 1.5 T scanner and a 32 channel heart-array coil with a steady-state free precession (SSFP) true fast imaging with steady state precession (trueFISP) GRAPPA sequence (acceleration-factor 3). Manual delineation of the myocardial contours was performed and absolute quantification was performed after baseline and contamination correction. At the first appointment, 1cc/4cc of the extracellular contrast agent Gd-BOPTA were administered, on the second date, 1cc/4cc of the blood pool contrast agent (CA) gadofosveset. At each date the examination was repeated after a 15-minute time interval. Results: Using gadofosveset perfusion the value (in cc/g/min) at rest was 0.66 ± 0.25 (mean ± standard deviation) for the first, and 0.55 ± 0.24 for the second CA application; for Gd-BOPTA it was 0.62 ± 0.25 and 0.45 ± 0.23. No significant difference was found between the acquired perfusion values. The apparent mean residence time in the myocardium was 23 seconds for gadofosveset and 19.5 seconds for Gd-BOPTA. Neither signal-to-noise ratio (SNR) nor subjectively rated image contrast showed a significant difference. Conclusion: The application of gadofosveset for an absolute quantification of myocardial perfusion is possible. Yet the acquired perfusion values show no significant differences to those determined with Gd-BOPTA, maintained the same SNR and comparable perfusion values, and did not picture the expected concentration time-course for an intravasal CA in the first pass. J. Magn. Reson. Imaging 2011;33:1047–1051. © 2011 Wiley-Liss, Inc.

Effects of respiratory cycle and body position on quantitative pulmonary perfusion by MRI

Abstract: Purpose: To evaluate the performance of lung perfusion imaging using two-dimensional (2D) first pass perfusion MRI and a quantitation program based on model-independent deconvolution algorithm. Materials and Methods: In eight healthy volunteers 2D first pass lung perfusion was imaged in coronal planes using a partial Fourier saturation recovery stead state free precession (SSFP) technique with a temporal resolution of 160 ms per slice acquisition. The dynamic signal in the lung was measured over time and absolute perfusion calculated based on a model-independent deconvolution program. Results: In the supine position mean pulmonary perfusion was 287 ± 106 mL/min/100 mL during held expiration. It was significantly reduced to 129 ± 68 mL/min/100 mL during held inspiration. Similar differences due to respiration were observed in prone position with lung perfusion much greater during expiration than during inspiration (271 ± 101 versus 99 ± 38 mL/min/100 mL (P < 0.01)). There was a linear increase in pulmonary perfusion from anterior to posterior lung fields in supine position. The perfusion gradient reversed in the prone position with the highest perfusion in anterior lung and the lowest in posterior lung fields. Conclusion: Lung perfusion imaging using a 2D saturation recovery SSFP perfusion MRI coupled with a model-independent deconvolution algorithm demonstrated physiologically consistent dynamic heterogeneity of lung perfusion distribution. J. Magn. Reson. Imaging 2011;. © 2011 Wiley-Liss, Inc.

Suitability of miniature inductively coupled RF coils as MR-visible markers for clinical purposes

Abstract: Purpose: MR-visible markers have already been used for various purposes such as image registration, motion detection, and device tracking. Inductively coupled RF (ICRF) coils, in particular, provide a high contrast and do not require connecting wires to the scanner, which makes their application highly flexible and safe. This work aims to thoroughly characterize the MR signals of such ICRF markers under various conditions with a special emphasis on fully automatic detection. Methods: The small markers consisted of a solenoid coil that was wound around a glass tube containing the MR signal source and tuned to the resonance frequency of a 1.5 T MRI. Marker imaging was performed with a spoiled gradient echo sequence (FLASH) and a balanced steady-state free precession (SSFP) sequence (TrueFISP) in three standard projections. The signal intensities of the markers were recorded for both pulse sequences, three source materials (tap water, distilled water, and contrast agent solution), different flip angles and coil alignments with respect to theB 0 direction as well as for different marker positions in the entire imaging volume (field of view, FOV). Heating of the ICRF coils was measured during 10-min RF expositions to three conventional pulse sequences. Clinical utility of the markers was assessed from their performance in computer-aided detection and in defining double oblique scan planes. Results: For almost the entire FOV (±215 mm) and an estimated 82% of all possible RF coil alignments with respect toB 0, the ICRF markers generated clearly visible MR signals and could be reliably localized over a large range of flip angles, in particular with the TrueFISP sequence (0.3°–4.0°). Generally, TrueFISP provided a higher marker contrast than FLASH. RF exposition caused a moderate heating (≤5 °C) of the ICRF coils only. Conclusions : Small ICRF coils,imaged at low flip angles with a balanced SSFP sequence showed an excellent performance under a variety of experimental conditions and therefore make for a reliable, compact, flexible, and relatively safe marker for clinical use.

Acute Myocarditis: Diagnostic Value of Contrast-Enhanced Cine Steady-State Free Precession MRI Sequences

Abstract: OBJECTIVE. MRI has become the primary tool for assessment of myocardial inflammation in patients with suspected acute myocarditis. Optimal diagnostic performance is achieved with late gadolinium-enhanced sequences, but cine balanced steady-state free precession (SSFP) MRI sequences are routinely used to evaluate cardiac function. Our aim was to prospectively assess the diagnostic value of unenhanced and contrast-enhanced cine SSFP MRI sequences in comparison with late gadolinium-enhanced sequences for imaging of patients with strong evidence of acute myocarditis. SUBJECTS AND METHODS. Eighteen patients with strong evidence of acute myocarditis underwent 1.5-T cardiac MRI. Unenhanced and contrast-enhanced cine SSFP images and late gadolinium-enhanced images were obtained. The images were analyzed both qualitatively and quantitatively. Data were analyzed with analysis of variance and the Bonferroni test or paired Student t test. RESULTS. Areas of high signal intensity were detected in 28% (5/18), 94% (17/18...

New respiratory gating technique for whole heart cine imaging: integration of a navigator slice in steady state free precession sequences.

Abstract: Purpose: To evaluate the performance of a slice navigator sequence integrated into a b-SSFP sequence for obtaining real time respiratory self-gated whole heart cine imaging. Materials and Methods: In this work, we present a novel and robust approach for respiratory motion detection by integrating a slice navigator sequence into a balanced steady state free precession (b-SSFP) sequence, while maintaining the steady state. The slice navigator sequence is integrated into consecutive repetition times (TRs) of a b-SSFP sequence to excite and read out a navigator slice. We performed several phantom experiments to test the performance of the slice navigator sequence. Additionally, the method was evaluated in five volunteers and compared with breathing signals obtained from conventional pencil beam navigator sequence. Finally, the navigator slice was used to obtain whole heart MR cine images. Results: The breathing signals detected by the proposed method showed an excellent agreement with those obtained from pencil beam navigators. Moreover, the technique was capable of removing respiratory motion artifacts with minimal distortion of the steady state. Image quality comparison showed a statistical significant improvement from a quality score of 2.1 obtained by the nonrespiratory gated images, compared to a quality score of 3.4 obtained by the respiratory gated images. Conclusion: This novel method represents a robust approach to estimate breathing motion during SSFP imaging. The technique was successfully applied to acquire whole heart artifact-free cine images. J. Magn. Reson. Imaging 2011;. © 2011 Wiley-Liss, Inc.

Nonenhanced ECG-gated time-resolved 4D Steady-state free precession (SSFP) MR angiography (MRA) for assessment of cerebral collateral flow: comparison with digital subtraction angiography (DSA)

Abstract: Objectives To evaluate a nonenhanced time-resolved 4D SSFP MRA for dynamic visualization of intracranial collateral blood flow.

Isolated Noncompaction of Ventricular Myocardium: a Magnetic Resonance Imaging Study of 11 Patients

Abstract: Objective To retrospectively summarize the cardiac magnetic resonance imaging (CMRI) findings of isolated noncompaction of ventricular myocardium (INVM). Materials and methods Eleven patients (M:F = 9:2; mean age, 35 years) were evaluated. Steady-state free precession (SSFP), fast spin echo (SE) sequence, SSFP cine imaging, and delayed enhanced inversion recovery spoiled gradient echo (IR-SPGR) sequence were used for showing abnormal myocardium, measuring ratio of noncompacted/compacted myocardium layers (NC/C ratio), and detecting myocardial viability. The left ventricle was divided into nine segments and a NC/C ratio > 2.3 in diastole was used as cutoff value in diagnosing left INVM. The right ventricle was assessed qualitatively. Results Cardiac MRI indicated left INVM in seven patients, right INVM in one patient and biventricle INVM in three patients. Characteristic CMRI changes included prominent trabeculations, deep intertrabecular recesses and an increase in the NC/C ratio. The most frequently involved segments was left ventricular apex. Three patients had abnormal high signals within the trabecular structures on SE T2 weighted image. One ventricular aneurysm and one apical thrombus were also observed. Delayed enhancement was seen in six of nine patients with subendocardial and transmural patterns. Conclusion There are CMRI features that might be characteristic for INVM.

Positive contrast visualization of SPIO-labeled pancreatic islets using echo-dephased steady-state free precession.

Abstract: Objective MRI has recently been introduced as a promising method of monitoring the transplanted pancreatic islets labelled with superparamagnetic iron oxide (SPIO). However, the traditional \( {\hbox{T}}_2^* \)-weighted approach frequently yields ambiguous results because of the negative contrast of the SPIO particles on the background of other body components. This obstacle could be overcome with the use of a novel method known as echo-dephased steady state free precession (SSFP), generating positive contrast in the presence of paramagnetic material.