Pilot study of improved lesion characterization in breast MRI using a 3D radial balanced SSFP technique with isotropic resolution and efficient fat‐water separation

Purpose

To assess a 3D radial balanced steady‐state free precession (SSFP) technique that provides submillimeter isotropic resolution and inherently registered fat and water image volumes in comparison to conventional T2‐weighted RARE imaging for lesion characterization in breast magnetic resonance imaging (MRI).

Materials and Methods

3D projection SSFP (3DPR‐SSFP) combines a dual half‐echo radial k‐space trajectory with a linear combination fat/water separation technique (linear combination SSFP). A pilot study was performed in 20 patients to assess fat suppression and depiction of lesion morphology using 3DPR‐SSFP. For all patients fat suppression was measured for the 3DPR‐SSFP image volumes and depiction of lesion morphology was compared against corresponding T2‐weighted fast spin echo (FSE) datasets for 15 lesions in 11 patients.

Results

The isotropic 0.63 mm resolution of the 3DPR‐SSFP sequence demonstrated improved depiction of lesion morphology in comparison to FSE. The 3DPR‐SSFP fat and water datasets were available in a 5‐minute scan time while average fat suppression with 3DPR‐SSFP was 71% across all 20 patients.

Conclusion

3DPR‐SSFP has the potential to improve the lesion characterization information available in breast MRI, particularly in comparison to conventional FSE. A larger study is warranted to quantify the effect of 3DPR‐SSFP on specificity. J. Magn. Reson. Imaging 2009;30:135–144. © 2009 Wiley‐Liss, Inc.     

Balanced phase-contrast steady-state free precession (PC-SSFP): a novel technique for velocity encoding by gradient inversion.

A technique for measuring velocity is presented that combines cine phase contrast (PC) MRI and balanced steady-state free precession (SSFP) imaging, and is thus termed PC-SSFP. Flow encoding was performed without the introduction of additional velocity encoding gradients in order to keep the repetition time (TR) as short as in typical SSFP imaging sequences. Sensitivity to through-plane velocities was instead established by inverting (i.e., negating) all gradients along the slice-select direction. Velocity sensitivity (VENC) could be adjusted by altering the first moments of the slice-select gradients. Disturbances of the SSFP steady state were avoided by acquiring different flow echoes in consecutively (i.e., sequentially) executed scans, each over several cardiac cycles, using separate steady-state preparation periods. A comparison of phantom measurements with those from established 2D-cine-PC MRI demonstrated excellent correlation between both modalities. In examinations of volunteers, PC-SSFP exhibited a higher intrinsic signal-to-noise ratio (SNR) and consequently low phase noise in measured velocities compared to conventional PC scans. An additional benefit of PC-SSFP is that it relies less on in-flow-dependent signal enhancement, and thus yields more uniform SNRs and better depictions of vessel geometry throughout the whole cardiac cycle in structures with slow and/or pulsatile flow.     

Dynamic visualization of arachnoid adhesions in a patient with idiopathic syringomyelia using high‐resolution cine magnetic resonance imaging at 3T

A 39‐year‐old female patient with thoracic syringomyelia underwent routine magnetic resonance imaging (MRI) and 3 T MRI to investigate the value of retrospectively cardiac‐gated cine steady‐state free precession (SSFP) MRI in the preoperative and postoperative diagnosis of arachnoid membranes in the spinal subarachnoid space. Therefore, 3T MRI included sagittal and transverse retrospectively cardiac‐gated cine balanced fast‐field echo (balanced‐FFE) sequences both preoperatively and after microsurgical lysis of arachnoid adhesions and expansive duraplasty. Arachnoid membranes were detected and this result was correlated with intraoperative findings and the results of routine cardiac‐gated phase‐contrast cerebrospinal fluid (CSF) flow MRI. Retrospectively cardiac‐gated cine SSFP MRI enabled imaging of arachnoid membranes with high spatial resolution and sufficient contrast to delineate them from hyperintense CSF preoperatively and postoperatively. The images were largely unaffected by artifacts. Surgery confirmed the presence of arachnoid adhesions in the upper thoracic spine. Not all arachnoid membranes that were seen on cine balanced‐FFE sequences caused significant spinal CSF flow blockages in cardiac‐gated phase‐contrast CSF flow studies. In conclusion, retrospectively cardiac‐gated cine SSFP MRI may become a valuable tool for the preoperative detection of arachnoid adhesions and the postoperative evaluation of microsurgical adhesiolysis in patients with idiopathic syringomyelia. J. Magn. Reson. Imaging 2010. © 2010 Wiley‐Liss, Inc.     

3D velocity quantification in the heart: Improvements by 3D PC‐SSFP

Purpose:

To test whether a 3D imaging sequence with phase contrast (PC) velocity encoding based on steady‐state free precession (SSFP) improves 3D velocity quantification in the heart compared to the currently available gradient echo (GE) approach.

Materials and Methods:

The 3D PC‐SSFP sequence with 1D velocity encoding was compared at the mitral valve in 12 healthy subjects with 3D PC‐GE at 1.5T. Velocity measurements, velocity‐to‐noise‐ratio efficiency (VNR_eff), intra‐ and interobserver variability of area and velocity measurements, contrast‐to‐noise‐ratio (CNR), and artifact sensitivity were evaluated in both long‐ and short‐axis orientation.

Results:

Descending aorta mean and peak velocities correlated well (r² = 0.79 and 0.93) between 3D PC‐SSFP and 3D PC‐GE. At the mitral valve, mean velocity correlation was moderate (r² = 0.70 short axis, 0.56 long axis) and peak velocity showed good correlation (r² = 0.94 short axis, 0.81 long axis). In some cases VNR_eff was higher, in others lesser, depending on slab orientation and cardiac phase. Intra‐ and interobserver variability was generally better for 3D PC‐SSFP. CNR improved significantly, especially at end systole. Artifact levels did not increase.

Conclusion:

3D SSFP velocity quantification was successfully tested in the heart. Blood‐myocardium contrast improved significantly, resulting in more reproducible velocity measurements for 3D PC‐SSFP at 1.5T. J. Magn. Reson. Imaging 2009;30:947–955. © 2009 Wiley‐Liss, Inc.     

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

Purpose:

To simultaneously detect iron‐labeled cancer cells and brain tumors in vivo in one scan, the balanced steady‐state free precession (b‐SSFP) imaging sequence was optimized at 1.5 T on mice developing brain metastases subsequent to the injection of micron‐sized iron oxide particle‐labeled human breast cancer cells.

Materials and Methods:

b‐SSFP sequence parameters (repetition time, flip angle, and receiver bandwidth) were varied and the signal‐to‐noise ratio, contrast between the brain and tumors, and the number of detected iron‐labeled cells were evaluated.

Results:

Optimal b‐SSFP images were acquired with a 26 msec repetition time, 35° flip angle, and bandwidth of ±21 kHz. b‐SSFP images were compared with T₂‐weighted 2D fast spin echo (FSE) and 3D spoiled gradient recalled echo (SPGR) images. The mean tumor‐brain contrast‐to‐noise ratio and the ability to detect iron‐labeled cells were the highest in the b‐SSFP images.

Conclusion:

A single b‐SSFP scan can be used to visualize both iron‐labeled cells and brain metastases. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

Four-dimensional phase contrast MRI with accelerated dual velocity encoding

Purpose:

To validate a novel approach for accelerated four‐dimensional phase contrast MR imaging (4D PC‐MRI) with an extended range of velocity sensitivity.

Materials and Methods:

4D PC‐MRI data were acquired with a radially undersampled trajectory (PC‐VIPR). A dual V_enc (dV_enc) processing algorithm was implemented to investigate the potential for scan time savings while providing an improved velocity‐to‐noise ratio. Flow and velocity measurements were compared with a flow pump, conventional 2D PC MR, and single V_enc 4D PC‐MRI in the chest of 10 volunteers.

Results:

Phantom measurements showed excellent agreement between accelerated dV_enc 4D PC‐MRI and the pump flow rate (R² ≥ 0.97) with a three‐fold increase in measured velocity‐to‐noise ratio (VNR) and a 5% increase in scan time. In volunteers, reasonable agreement was found when combining 100% of data acquired with V_enc = 80 cm/s and 25% of the high V_enc data, providing the VNR of a 80 cm/s acquisition with a wider velocity range of 160 cm/s at the expense of a 25% longer scan.

Conclusion:

Accelerated dual V_enc 4D PC‐MRI was demonstrated in vitro and in vivo. This acquisition scheme is well suited for vascular territories with wide ranges of flow velocities such as congenital heart disease, the hepatic vasculature, and others. J. Magn. Reson. Imaging 2012;35:1462–1471. © 2012 Wiley Periodicals, Inc.     

Phase contrast using multiecho steady-state free precession.

Conventional phase-contrast (PC) MRI is limited in the temporal resolution (typically 50 ms) that can be achieved, due to the need to implement bipolar velocity encoding gradients. PC using steady-state free precession (SSFP) has recently been developed to acquire PC data at higher rates without sacrificing contrast-to-noise ratio (CNR). This work presents two multiecho SSFP PC implementations that can be used to increase the time efficiency of PCSSFP. Both approaches (extrinsic and intrinsic) enable reference image lines to be acquired within the same TR as the flow-encoded lines, thus minimizing the scan time and permitting TR-equivalent temporal resolutions. Both approaches have been implemented and tested successfully on human volunteers at 1.5T and 3T. While the intrinsic approach is useful for encoding higher velocity flows in-plane, the extrinsic implementation can be used for studying a wider range of encoding velocities for flow in the imaging plane and through the imaging plane.     

Improved MR phase‐contrast velocimetry using a novel nine‐point balanced motion‐encoding scheme with increased robustness to eddy current effects

Phase‐contrast MRI (PC‐MRI) velocimetry is a noninvasive, high‐resolution motion assessment tool. However, high motion sensitivity requires strong motion‐encoding magnetic gradients, making phase‐contrast‐MRI prone to baseline shift artifacts due to the generation of eddy currents. In this study, we propose a novel nine‐point balanced velocity‐encoding strategy, designed to be more accurate in the presence of strong and rapidly changing gradients. The proposed method was validated using a rotating phantom, and its robustness and precision were explored and compared with established approaches through computer simulations and in vivo experiments. Computer simulations yielded a 39–57% improvement in velocity–noise ratio (corresponding to a 27–33% reduction in measurement error), depending on which method was used for comparison. Moreover, in vivo experiments confirmed this by demonstrating a 26–53% reduction in accumulated velocity error over the R–R interval. The nine‐point balanced phase‐contrast‐MRI‐encoding strategy is likely useful for settings where high spatial and temporal resolution and/or high motion sensitivity is required, such as in high‐resolution rodent myocardial tissue phase mapping. Magn Reson Med, 2013. © 2012 Wiley Periodicals, Inc.     

Comparison of wideband steady‐state free precession and T2‐weighted fast spin echo in spine disorder assessment at 1.5 and 3 T

Wideband steady‐state free precession (WB‐SSFP) is a modification of balanced steady‐state free precession utilizing alternating repetition times to reduce susceptibility‐induced balanced steady‐state free precession limitations, allowing its use for high‐resolution myelographic‐contrast spinal imaging. Intertissue contrast and spatial resolution of complete‐spine‐coverage 3D WB‐SSFP were compared with those of 2D T₂‐weighted fast spin echo, currently the standard for spine T₂‐imaging. Six normal subjects were imaged at 1.5 and 3 T. The signal‐to‐noise ratio efficiency (SNR per unit‐time and unit‐volume) of several tissues was measured, along with four intertissue contrast‐to‐noise ratios; nerve‐ganglia:fat, intradural‐nerves:cerebrospinal fluid, nerve‐ganglia:muscle, and muscle:fat. Patients with degenerative and traumatic spine disorders were imaged at both MRI fields to demonstrate WB‐SSFP clinical advantages and disadvantages. At 3 T, WB‐SSFP provided spinal contrast‐to‐noise ratios 3.7–5.2 times that of fast spin echo. At 1.5 T, WB‐SSFP contrast‐to‐noise ratio was 3–3.5 times that of fast spin echo, excluding a 1.7 ratio for intradural‐nerves:cerebrospinal fluid. WB‐SSFP signal‐to‐noise ratio efficiency was also higher. Three‐dimensional WB‐SSFP disadvantages relative to 2D fast spin echo are reduced edema hyperintensity, reduced muscle signal, and higher motion sensitivity. WB‐SSFP's high resolution and contrast‐to‐noise ratio improved visualization of intradural nerve bundles, foraminal nerve roots, and extradural nerve bundles, improving detection of nerve compression in radiculopathy and spinal‐stenosis. WB‐SSFP's high resolution permitted reformatting into orthogonal planes, providing distinct advantages in gauging fine spine pathology. Magn Reson Med, 2012. © 2012 Wiley Periodicals, Inc.     

Non‐contrast‐enhanced flow‐independent peripheral MR angiography with balanced SSFP

Flow‐independent angiography is a non‐contrast‐enhanced technique that can generate vessel contrast even with reduced blood flow in the lower extremities. A method is presented for producing these angiograms with magnetization‐prepared balanced steady‐state free precession (bSSFP). Because bSSFP yields bright fat signal, robust fat suppression is essential for detailed depiction of the vasculature. Therefore, several strategies have been investigated to improve the reliability of fat suppression within short scan times. Phase‐sensitive SSFP can efficiently suppress fat; however, partial volume effects due to fat and water occupying the same voxel can lead to the loss of blood signal. In contrast, alternating repetition time (ATR) SSFP minimizes this loss; however, the level of suppression is compromised by field inhomogeneity. Finally, a new double‐acquisition ATR‐SSFP technique reduces this sensitivity to off‐resonance. In vivo results indicate that the two ATR‐based techniques provide more reliable contrast when partial volume effects are significant. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Hepatic vascular flow measurements by phase contrast MRI and doppler echography: A comparative and reproducibility study

Purpose:

To directly compare and study the variability of parameters related to hepatic blood flow measurements using 3 T phase‐contrast magnetic resonance imaging (PC‐MRI) and Doppler ultrasound (US).

Materials and Methods:

Nine healthy subjects were studied. Blood velocities and flow rate measurements were performed in the portal vein and the proper hepatic artery. MR studies were performed using a 3 T imager. Gradient‐echo fast phase contrast sequences were used with both cardiac and respiratory gating. MR and Doppler flow parameters were extracted and compared. Two methods of calculation were used for Doppler flow rate analysis.

Results:

Compared to Doppler US, PC‐MRI largely underestimated hepatic flow data with lower variability and higher reproducibility. This reproducibility was more pronounced in the portal vein than in the proper hepatic artery associated with poorer velocity correlations. Total hepatic flow values were 1239 ± 223 mL/min and 1595 ± 521 mL/min for PC‐MRI and Doppler US, respectively.

Conclusion:

Free‐breathing PC‐MRI can provide reliable noninvasive measurement of hepatic flow parameters compared to Doppler US. The MR technique could help to improve Doppler flow calculations, thereby allowing standardization of protocols, particularly for applications in disease. J. Magn. Reson. Imaging 2010;31:579–588. © 2010 Wiley‐Liss, Inc.     

Spiral balanced steady-state free precession cardiac imaging.

Balanced steady-state free precession (SSFP) sequences are useful in cardiac imaging because they achieve high signal efficiency and excellent blood-myocardium contrast. Spiral imaging enables the efficient acquisition of cardiac images with reduced flow and motion artifacts. Balanced SSFP has been combined with spiral imaging for real-time interactive cardiac MRI. New features of this method to enable scanning in a clinical setting include short, first-moment nulled spiral trajectories and interactive control over the spatial location of banding artifacts (SSFP-specific signal variations). The feasibility of spiral balanced SSFP cardiac imaging at 1.5 T is demonstrated. In observations from over 40 volunteer and patient studies, spiral balanced SSFP imaging shows significantly improved contrast compared to spiral gradient-spoiled imaging, producing better visualization of cardiac function, improved localization, and reduced flow artifacts from blood.     

Fundamental study of the fat-suppressed three-dimensional coherent oscillatory state acquisition for the manipulation of image contrast (3D-COSMIC) sequence in the knee joint cartilage

Fat-suppressed three-dimensional coherent oscillatory state acquisition for the manipulation of image contrast (3D-COSMIC) is a sequence that is based on fast imaging employing steady state acquisition (FIESTA) of balanced steady-state free precession (balanced SSFP). Since the data acquisition of steady-state transition is filled up with the center of k-space, improvement in the contrast of the cartilage, which is a low T?/T? value domain, is expected. This time we report on the usability in applying the above sequence to cartilage imaging of the knee joint and comparing and examining this sequence with the sequence in the past from the viewpoints of the contrast and scan time. As a result, compared with fat-suppressed three-dimensional spoiled gradient echo (3D-SPGR), the contrast of marrow and synovial fluid was equivalent to that of the cartilage, and imaging time was shorter than half of that with the cartilage. Compared with a fat-suppressed two-dimensional proton density weighted image (2D-PDWI), the contrast of the cartilage and synovial fluid was significantly improved, and spatial resolution was also excellent. As a short imaging time and a high resolution image pick-up are possible for fat-suppressed 3D-COSMIC, and it can describe minute damage of the cartilage since it depicts synovial fluid as high-level signals, I think this technique is useful.     

Multicontrast late gadolinium enhancement imaging enables viability and wall motion assessment in a single acquisition with reduced scan times

Purpose

To determine the accuracy of multicontrast late enhancement imaging (MCLE) in the assessment of myocardial viability and wall motion compared to the conventional wall motion and viability cardiac magnetic resonance imaging (MRI) pulse sequences.

Materials and Methods

Forty‐one patients with suspected myocardial infarction were studied. Patients underwent assessment of cardiac function with cine steady‐state free‐precession (SSFP), followed by late gadolinium enhancement (LGE) imaging using inversion recovery gradient echo scanning (IR‐GRE) sequence and MCLE. MCLE was compared to cine SSFP in the assessment of wall motion, ejection fraction (EF), left ventricular (LV) mass, LV end‐diastolic volume (EDV), and to IR‐GRE for measuring infarct size.

Results

MCLE, IR‐GRE, and SSFP imaging demonstrated excellent agreement in the assessment of EF, LV infarct size, and LV mass (r > 0.95, P < 0.001 for all measures), as well as in the assessment of wall motion (κ statistic 0.75).

Conclusion

MCLE provided coregistered images for the assessment of viability and wall motion without loss of accuracy in the assessment of quantitative cardiac parameters. MCLE provides accurate quantitative cardiac assessment with reduced scan times compared to the conventional sequences and thus may be used as an alternative to conventional cine SSFP and IR‐GRE imaging. J. Magn. Reson. Imaging 2009;30:771–777. © 2009 Wiley‐Liss, Inc.     

ToF‐SWI: Simultaneous time of flight and fully flow compensated susceptibility weighted imaging

Purpose

To perform systematic investigations on parameter selection of a dual‐echo sequence (ToF‐SWI) for combined 3D time‐of‐flight (ToF) angiography and susceptibility weighted imaging (SWI).

Materials and Methods

ToF‐SWI was implemented on 1.5 T and 3 T MR scanners with complete 3D first‐order flow compensation of the second echo. The efficiency of flow compensating the SWI echo was studied based on phantom and in vivo examinations. Arterial and venous contrasts were examined in volunteers as a function of flip angle and compared with additionally acquired single‐echo ToF and single‐echo SWI data.

Results

Complete flow compensation is required to reduce arterial contamination in the SWI part caused by signal voids. A ramped flip angle of 20° depicted arteries best while venous contrast was preserved. Comparing ToF‐SWI with single‐echo ToF demonstrated arteries with similar quality and delineated all major arteries equally well. Venous delineation was degraded due to lower SNR associated with the thinner slabs used with ToF‐SWI compared to single‐echo SWI acquisition.

Conclusion

A dual‐echo sequence (ToF‐SWI) with full flow compensation of the second echo in a single scan is feasible. This sequence allows simultaneous visualization of intrinsically coregistered arteries and veins without spatial mis‐registration of vessels caused by oblique flow and with minimal signal loss in arteries. J. Magn. Reson. Imaging 2009;29:1478–1484. © 2009 Wiley‐Liss, Inc.     

Modulated repetition time look‐locker (MORTLL): A method for rapid high resolution three‐dimensional T1 mapping

Purpose

To demonstrate a modification of the Look‐Locker (LL) technique that enables rapid high resolution T1 mapping over the physiologic range of intracranial T1 values, ranging from white matter to cerebrospinal fluid (CSF). This is achieved by use of a three‐dimensional (3D) balanced steady‐state free precession (b‐SSFP) acquisition (for high signal‐to‐noise and resolution) along with variable repetition time to allow effective full recovery of longitudinal magnetization.

Materials and Methods

Two modifications to the Look‐Locker technique were made to realize high resolution imaging in a clinically reasonable scan time. The 3D b‐SSFP acquisition after an initial inversion pulse was followed by a variable repetition time. This technique makes it possible to image a volume of thin contiguous slices with high resolution and accuracy using a simple fitting procedure and is particularly useful for imaging long T1 species such as CSF. The total scan time is directly proportional to the number of slices to be acquired. The scan time was reduced by almost half when the repetition time was modified using a predesigned smooth function. Phantoms and volunteers were imaged at different resolutions on a 3 Tesla scanner. Results were compared with other accepted techniques.

Results

T1 values in the brain corresponded well with full repetition time imaging as well as inversion recovery spin echo imaging. T1 values for white matter, gray matter, and CSF were measured to be 755 ± 10 ms, 1202 ± 9 ms, and 4482 ± 71 ms, respectively. Scan times were reduced by approximately half over full repetition time measurements.

Conclusion

High resolution T1 maps can be obtained rapidly and with a relatively simple postprocessing method. The technique is particularly well suited for long T1 species. For example, changes in the composition of proteins in CSF are linked to various pathologies. The T1 values showed excellent agreement with values obtained from inversion recovery spin‐echo imaging. J. Magn. Reson. Imaging 2009. © 2009 Wiley‐Liss, Inc.     

Whole heart magnetization‐prepared steady‐state free precession coronary vein MRI

Purpose

To compare two coronary vein imaging techniques using whole‐heart balanced steady‐state free precession (SSFP) and a targeted double‐oblique spoiled gradient‐echo (GRE) sequences in combination with magnetization transfer (MT) preparation sequence for tissue contrast improvement.

Materials and Methods

Nine healthy subjects were imaged with the proposed technique. The results are compared with optimized targeted MT prepared GRE acquisitions. Both quantitative and qualitative analyses were performed to evaluate each imaging method.

Results

Whole‐heart images were successfully acquired with no visible image artifact in the vicinity of the coronary veins. The anatomical features and visual grading of both techniques were comparable. However, the targeted small slab acquisition of the left ventricular lateral wall was superior to whole‐heart acquisition for visualization of relevant information for cardiac resynchronization therapy (CRT) lead implantation.

Conclusion

We demonstrated the feasibility of whole‐heart coronary vein MRI using a 3D MT‐SSFP imaging sequence. A targeted acquisition along the lateral left ventricular wall is preferred for visualization of branches commonly used in CRT lead implantation. J. Magn. Reson. Imaging 2009;29:1293–1299. © 2009 Wiley‐Liss, Inc.     

Nonsubtractive spiral phase contrast velocity imaging.

Phase contrast velocity imaging is a standard method for accurate in vivo flow measurement. One drawback, however, is that it lengthens the scan time (or reduces the achievable temporal resolution) because one has to acquire two or more images with different flow sensitivities and subtract their phases to produce the final velocity image. Without this step, non-flow-related phase variations will give rise to an erroneous, spatially varying background velocity. In this paper, we introduce a novel phase contrast velocity imaging technique that requires the acquisition of only a single image. The idea is to estimate the background phase variation from the flow-encoded image itself and then have it removed, leaving only the flow-related phase to generate a corrected flow image. This technique is sensitive to flow in one direction and requires 50% less scan time than conventional phase contrast velocity imaging. Phantom and in vivo results were obtained and compared with those of the conventional method, demonstrating the new method's effectiveness in measuring flow in various vessels of the body. Magn Reson Med 42:704-713, 1999.     

Fast T(2)-weighted imaging by PSIF at 0.2 T for interventional MRI.

Rapid T(2) weighted (T(2)W) images would facilitate physicians being able to distinguish normal tissues, vessels, tumors, and thermal lesions from therapeutic devices throughout interventional MRI procedures commonly performed in open low-field scanners (e.g., 0.2 T). Conventional diagnostic MRI techniques have not been successful at low-field strength for fast T(2)W imaging during the guidance phase of interventional MRI (I-MRI) procedures. FISP and true-FISP methods yield T(1)/T(2)-weighted images and do not always provide sufficient contrast for device guidance or lesion assessment. As such, a variant of PSIF (a gradient reversed form of FISP) which collects the T(2)-weighted spin echo of the SSFP signal was developed and implemented at 0.2 T for use in I-MRI procedures. The sequence has a balanced readout gradient to reduce motion sensitivity. Asymmetric sampling toward the end of the TR cycle reduces T(2)* decay of the spin echo component in the SSFP signal. The sequence gives one image in 5-7 s in vivo with adequate SNR and T(2) contrast for interventional applications. Patient studies showed that the PSIF sequence variant demarcates many tumors not detectable by either FISP or true-FISP. Results from animal experiments suggested that it has potential to monitor thermal lesions during interstitial thermal ablation procedures. Magn Reson Med 42:335-344, 1999.