True Fast Imaging With Steady-state Precession Imaging Research Articles

Synthetic CT generation for MRI-guided adaptive radiotherapy in prostate cancer.

Current MRI-guided adaptive radiotherapy (MRgART) workflows require fraction-specific electron and/or mass density maps, which are created by deformable image registration (DIR) between the simulation CT images and daily MR images. Manual density overrides may also be needed where DIR-produced results are inaccurate. This approach slows the adaptive radiotherapy workflow and introduces additional dosimetric uncertainties, especially in the presence of the magnetic field. This study investigated a method based on a conditional generative adversarial network (cGAN) with a multi-planar method to generate synthetic CT images from low-field MR images to improve efficiency in MRgART workflows for prostate cancer. Fifty-seven male patients, who received MRI-guided radiation therapy to the pelvis using the ViewRay MRIdian Linac, were selected. Forty-five cases were randomly assigned to the training cohort with the remaining twelve cases assigned to the validation/testing cohort. All patient datasets had a semi-paired DIR-deformed CT-sim image and 0.35T MR image acquired using a true fast imaging with steady-state precession (TrueFISP) sequence. Synthetic CT images were compared with deformed CT images to evaluate image quality and dosimetric accuracy. To evaluate the dosimetric accuracy of this method, clinical plans were recalculated on synthetic CT images in the MRIdian treatment planning system. Dose volume histograms for planning target volumes (PTVs) and organs-at-risk (OARs) and dose distributions using gamma analyses were evaluated. The mean-absolute-errors (MAEs) in CT numbers were 30.1 ± 4.2 HU, 19.6 ± 2.3 HU and 158.5 ± 26.0 HU for the whole pelvis, soft tissue, and bone, respectively. The peak signal-to-noise ratio was 35.2 ± 1.7 and the structural index similarity measure was 0.9758 ± 0.0035. The dosimetric difference was on average less than 1% for all PTV and OAR metrics. Plans showed good agreement with gamma pass rates of 99% and 99.9% for 1%/1 mm and 2%/2 mm, respectively. Our study demonstrates the potential of using synthetic CT images created with a multi-planar cGAN method from 0.35T MRI TrueFISP images for the MRgART treatment of prostate radiotherapy. Future work will validate the method in a large cohort of patients and investigate the limitations of the method in the adaptive workflow.

SPIO-enhanced 0.35T MRI-guided radiotherapy for liver malignancies: usefulness in tumor visualization.

The purpose of this study was to investigate the changes of tumor-to-liver signal ratio in a 0.35T MRI-guided radiotherapy system and to evaluate the usefulness and pitfalls of superparamagnetic iron oxide (SPIO) administration for visualization of liver tumors. Forty-two patients treated with MRI-guided stereotactic ablative radiotherapy (SABR) for liver tumors were included in this study. The tumor-to-liver signal ratios before and after SPIO administration were retrospectively assessed and compared on true fast imaging with steady-state precession (FISP). Before SPIO administration, liver tumors were either invisible or barely visible in 15 cases (36%), but all tumors became visible after SPIO administration. The mean values of tumor-to-liver signal ratio before and after SPIO administration were 0.939 ± 0.201 and 1.336 ± 0.300, respectively (mean ± standard deviation, p < 0.001). In six (14%) patients, liver tumors were visible on true FISP imaging before SPIO administration, but became invisible after administration. This study showed that liver tumors that are invisible on true FISP imaging can be made visible by administration of SPIO, and that MRI-guided SABR can be performed accurately. This is the first report to examine the usefulness of liver-specific contrast agent superparamagnetic iron oxides in 0.35T MRI-guided radiation therapy. Liver tumors that are invisible on true fast imaging with steady-state precession can be made visible by administration of superparamagnetic iron oxides.

Optimization of pulse sequences in ultrafast magnetic resonance imaging for the diagnosis of acute abdominal pain caused by gastrointestinal disease.

BackgroundMagnetic resonance imaging (MRI) is widely used to diagnose acute abdominal pain; however, it remains unclear which pulse sequence has priority in acute abdominal pain.PurposeTo investigate the diagnostic accuracy of MRI and to assess the conspicuity of each pulse sequence for the diagnosis of acute abdominal pain due to gastrointestinal diseasesMaterial and MethodsWe retrospectively enrolled 60 patients with acute abdominal pain who underwent MRI for axial and coronal T2-weighted (T2W) imaging, fat-suppressed (FS)-T2W imaging, and true-fast imaging with steady-state precession (True-FISP) and axial T1-weighted (T1W) imaging and investigated the diagnosis with endoscopy, surgery, histopathology, computed tomography, and clinical follow-up as standard references. Two radiologists determined the diagnosis with MRI and rated scores of the respective sequences in assessing intraluminal, intramural, and extramural abnormality using a 5-point scale after one month. Diagnostic accuracy was calculated and scores were compared by Wilcoxon-signed rank test with Bonferroni correction.ResultsDiagnostic accuracy was 90.0% and 93.3% for readers 1 and 2, respectively. Regarding intraluminal abnormality, T2W, FS-T2W, and True-FISP imaging were superior to T1W imaging in both readers. FS-T2W imaging was superior to True-FISP in reader 2 (P < 0.0083). For intramural findings, there was no significant difference in reader 1, whereas T2W, FS-T2W, and True-FISP imaging were superior to T1W imaging in reader 2 (P < 0.0083). For extramural findings, FS-T2W imaging was superior to T2W, T1W, and True-FISP imaging in both readers (P < 0.0083).ConclusionT2W and FS-T2W imaging are pivotal pulse sequences and should be obtained before T1W and True-FISP imaging.

True FISP Cardiac Gated CSF Flow Dynamic Imaging of Chiari Malformation

Abstract INTRODUCTION Brain pulsation and related CSF dynamics is a well-known intraoperative characteristic, but methods for its visualization on magnetic resonance imaging (MRI) have until now been very limited. Best characterized techniques including phase-contrast MRI and cine echo-planar imaging, although of significant value, lack a detailed spatial and temporal resolution needed to investigate CSF and structural dynamics in an adequate manner to address preoperative decision making. Electrocardiographic (ECG)-gated true fast imaging with steady-state precession (FISP) sequences has been widely used to investigate cardiac motion and is capable of demonstrating brain pulsations and movements of intracranial structures surrounded by CSF with high temporal and spatial precision. We feature here the application of true FISP cardiac-gated imaging to the management of 2 patients with Chiari Malformation Type 1 and associated syringohydromyelia. METHODS Two children with Chiari Malformation Type 1 and concurrent syringohydromyelia underwent true FISP cardiac-gated imaging at our institution. RESULTS While conventional imaging studies such as T1 and phase-contrast cine MRI appeared to demonstrate obstruction of CSF flow secondary to tonsillar herniation, true FISP showed patent peritonsillar CSF flow and the presence of a pulsatile arachnoid veil. Subsequently, open surgery confirmed the presence of an arachnoid veil, and postoperative true FISP imaging revealed restoration of CSF flow following arachnoid veil fenestration. CONCLUSION We demonstrated 2 patients who presented with Chiari 1 malformation, where true FISP cardiac imaging was very instructive in visualizing dynamic images of an arachnoid veil and its possible role in the development of syringomyelia without a significant obstruction of outflow by cerebellar tonsils at the foramen of Magendie. We advocate use of this technology will aid in pre and post-surgical decision making, providing a more representative image of posterior fossa pathology in patients with Chiari 1 malformation.

Automated 3D quantitative assessment and measurement of alpha angles from the femoral head-neck junction using MR imaging

To develop an automated approach for 3D quantitative assessment and measurement of alpha angles from the femoral head-neck (FHN) junction using bone models derived from magnetic resonance (MR) images of the hip joint.Bilateral MR images of the hip joints were acquired from 30 male volunteers (healthy active individuals and high-performance athletes, aged 18–49 years) using a water-excited 3D dual echo steady state (DESS) sequence. In a subset of these subjects (18 water-polo players), additional True Fast Imaging with Steady-state Precession (TrueFISP) images were acquired from the right hip joint. For both MR image sets, an active shape model based algorithm was used to generate automated 3D bone reconstructions of the proximal femur. Subsequently, a local coordinate system of the femur was constructed to compute a 2D shape map to project femoral head sphericity for calculation of alpha angles around the FHN junction. To evaluate automated alpha angle measures, manual analyses were performed on anterosuperior and anterior radial MR slices from the FHN junction that were automatically reformatted using the constructed coordinate system.High intra- and inter-rater reliability (intra-class correlation coefficients > 0.95) was found for manual alpha angle measurements from the auto-extracted anterosuperior and anterior radial slices. Strong correlations were observed between manual and automatic measures of alpha angles for anterosuperior (r = 0.84) and anterior (r = 0.92) FHN positions. For matched DESS and TrueFISP images, there were no significant differences between automated alpha angle measures obtained from the upper anterior quadrant of the FHN junction (two-way repeated measures ANOVA, F < 0.01, p = 0.98).Our automatic 3D method analysed MR images of the hip joints to generate alpha angle measures around the FHN junction circumference with very good reliability and reproducibility. This work has the potential to improve analyses of cam-type lesions of the FHN junction for large-scale morphometric and clinical MR investigations of the human hip region.

90°-Flip-angle three-dimensional double-echo steady-state (3D-DESS) magnetic resonance imaging of the knee: Isovoxel cartilage imaging at 3 T

PurposeThe purpose of this study was to investigate whether 3D-double echo steady state (3D-DESS) with improved contrast by setting the FA (Flip angle) at 90° is useful in 3D isotropic cartilage imaging of the knee at 3T. Materials and methodsImaging was performed in 10 healthy volunteers using 3 methods: with 3D-DESS using FA of 25° and 90°, and with true fast imaging with steady-state precession (True-FISP). The signal-to-noise ratio (SNR) of the synovial fluid and cartilage, and contrast-to-noise ratio (CNR) were measured, and mean values were compared. Visual assessment of artifacts was performed with the cartilage divided into 6 regions. ResultsThere were no significant differences in synovial fluid SNR in the comparison between FA-90° 3D-DESS and True-FISP (P=0.364). A significantly higher cartilage SNR was observed with FA-90° 3D-DESS than with True-FISP (P=0.031). There were no significant differences in synovial fluid-cartilage CNR between FA-90° 3D-DESS and True-FISP (P=0.892). In the evaluation of artifacts, FA-90° 3D-DESS imaging showed a significantly higher score than True-FISP imaging in the patella and trochlea cartilage (P<0.001, P<0.002). ConclusionsFA-90° 3D-DESS is useful in 3D isotropic cartilage imaging of the knee at 3T.

Assessment with Unenhanced MRI Techniques of Renal Morphology and Hemodynamic Changes during Acute Kidney Injury and Chronic Kidney Disease in Mice

Background/Aims: Changes in renal oxygenation and perfusion have been identified as common pathways to the development and progression of renal disease. Recently, the sensitivity of hemodynamic response imaging (HRI) was demonstrated; this is a functional magnetic resonance imaging (MRI) method combined with transient hypercapnia and hyperoxia for the evaluation of renal perfusion and vascular reactivity. The aim of this study was to utilize HRI for the noninvasive evaluation of changes in renal hemodynamics and morphology during acute, chronic and acute-on-chronic renal failures. Methods: Renal-HRI maps and true fast imaging with steady-state precession (True-FISP) images were used to evaluate renal perfusion, morphology and corticomedullary differentiation (CMD). MR images were acquired on two mouse models of kidney injury: adenine-induced chronic kidney disease (CKD) and rhabdomyolysis-induced acute kidney injury (AKI). Serum urea was measured from these mice in order to determine renal function. Results: Renal-HRI maps revealed a blunted response to hypercapnia and hyperoxia with evolving kidney dysfunction in both models, reflecting hampered renal vascular reactivity and perfusion. True-FISP images showed a high sensitivity to renal morphological changes, with different patterns characterizing each model. Calculated data obtained from HRI and True-FISP during the evolution of renal failure and upon recovery, with and without protective intervention, closely correlated with the degree of renal impairment. Conclusions: This study suggests the potential combined usage of two noninvasive MRI methods, HRI and True-FISP, for the assessment of renal dysfunction without the potential risk associated with contrast-agents administration. HRI may also serve as a research tool in experimental settings, revealing the hemodynamic changes associated with kidney dysfunction.

Intraobserver and Interobserver Variability of Renal Volume Measurements in Polycystic Kidney Disease Using a Semiautomated MR Segmentation Algorithm

Total renal volume and changes in kidney volume are markers of disease progression in autosomal-dominant polycystic kidney disease (ADPKD) but are not used in clinical practice in part because of the complexity of manual measurements. This study aims to assess the intra- and interobserver reproducibility of a semiautomated renal volumetric algorithm using fluid-sensitive MRI pulse sequences. Renal volumes of 17 patients with ADPKD were segmented from high-resolution coronal HASTE and true fast imaging with steady-state precession (FISP) MR acquisitions. Measurements performed independently by four readers were repeated, typically after 7 days. Intraobserver agreement indexes were calculated for total kidney volume for each patient. Interobserver agreement indexes were obtained for the six paired combinations of readers as well as for two readers after rigorous formalized training. Pearson and concordance correlation coefficients, coefficients of variation (CVs), and 95% limits of agreement were determined. The HASTE and true FISP sequences performed similarly with a median intraobserver agreement of greater than 98.1% and a CV of less than 2.4% across all readers. The median interobserver agreement was greater than 95.2% and the CV was less than 7.1%, across all reader pairs. Reader training further lowered interobserver CV. The mean total kidney volume was 1420 mL (range, 331-3782 mL) for HASTE imaging and 1445 mL (range, 301-3714 mL) for true FISP imaging, with mean image processing times per patient of 43 and 28 minutes, respectively. This semiautomated MR volumetric algorithm provided excellent intraobserver and very good interobserver reproducibility using fluid-sensitive pulse sequences that emphasize cyst conspicuity.

MRI and cardiac pacing devices — beware the rules are changing

We have been following the development of MRI-compatible cardiac permanent pacemakers (PPM) with great interest. Recently, we have been asked to perform clinical MRI studies in patients with a MRI-compatible PPM. We would like to share our experience in performing one such study and highlight important safety measures that radiologists should undertake prior to imaging. Conventional PPM has always been regarded as an absolute contraindication for MRI. This has prevented a large number of patients from undergoing clinically important MRI studies. MRI-compatible PPM is now available for clinical use following a prospective randomised controlled unblinded multicenter study, involving 464 patients [1,2]. Our first patient had an Advisa DR MRI SureScan (Medtronic, Minneapolis, MN) system, which is one of the most widely used MRI-compatible systems. These devices have been designed to minimise thermal damage and limit induced voltages preventing unintended stimulation of the heart. Performing an MRI study in these patients requires robust preparation and liaison between physicist, radiographer, electrophysiology technicians, consultant radiologist and referring clinician. Informed consent should be obtained from the patient after discussing the benefits of the MRI study and potential complications. The following radiology specific pre-requisites should be fulfilled and adhered to and these may change depending on the manufacturer of the device: Cylindrical bore, clinical MR systems with a static magnetic field of 1.5 T. Gradient systems with maximum gradient slew rate performance per axis of ≤200 T m−1per second. Whole body averaged specific absorption rate (SAR) must be ≤2 W kg−1 and for head <3.2 W kg−1. Implant must consist of an MRI-compatible device as well as the lead. Any other leads or broken leads remain a contraindication. The pacing system should be implanted in either the right or left pectoral region and should have been in place for more than 6 weeks. The patient should not be positioned on his or her side within the scanner. Local transmit/receive coils should not be placed over the pacing system. Prior to taking the patient into the scanner the PPM is programmed to MRI safe mode by electrophysiologists outside the MR safety zone. Once in the scanner, continuous monitoring using electrocardiography (ECG), pulse oximetry and blood pressure is essential. External defibrillator must be readily available and the procedure should be abandoned if patient's haemodynamic function is compromised. After completing the scan, the PPM is turned back on to normal mode and the correct pacing capture threshold is ensured prior to discharging the patient. Our patient was a young man who underwent a cardiac MRI study for cardiomyopathy. He was involved in discussions regarding the safety of the procedure and consented prior to the study. He was extremely anxious when he went into the scanner, but relaxed as the procedure went on. He did not experience any untoward sensations or arrhythmia during the 40 min study. Standard TrueFISP (true fast imaging with steady state precession) images were degraded owing to artefacts from the leads; this was rectified by switching over to FLASH (fast low angle shot) cine images (Figure 1). Overall the image quality was good. Figure 1 Cardiac MRI in standard planes in (a) TrueFISP (true fast imaging with steady state precession) and (b–d) FLASH (fast low angle shot) sequences. Note the clear delineation of the pacing leads (arrow) on the latter sequence with no significant ... We foresee that more patients will undergo MRI scanning with compatible cardiac pacing systems. Currently there is limited evidence regarding its safety and long-term effects. We, therefore, profess extreme prudence and a multidisciplinary approach prior to scanning a patient with an MRI-compatible pacemaker.

Articular cartilage and labral lesions of the glenohumeral joint: diagnostic performance of 3D water-excitation true FISP MR arthrography

To evaluate the diagnostic performance of MR arthrography in the detection of articular cartilage and labral lesions of the glenohumeral joint using a transverse 3D water-excitation true fast imaging with steady-state precession (FISP) sequence. Seventy-five shoulders were included retrospectively. Shoulder arthroscopy was performed within 6 months of MR arthrography. MR images were evaluated separately by two radiologists. They were blinded to clinical and arthroscopic information. Arthroscopy served as the reference standard. For the detection of humeral cartilage lesions, sensitivities and specificities were 86% (12/14)/89% (50/56) for observer 1 and 93%/86% for observer 2) for the transverse true FISP sequence and 64%/86% (50%/82% for observer 2) for the coronal intermediate-weighted spin-echo images. The corresponding values for the glenoidal cartilage were 60% (6/10)/88% (51/58) (80%/76% for observer 2) and 70%/86% (60%/74% for observer 2) respectively. For the detection of abnormalities of the anterior labrum (only assessed on true FISP images) the values were 94% (15/16)/84% (36/43) (88%/79% for observer 2). The corresponding values for the posterior labrum were 67% (8/12)/77% (36/47) (observer 2: 25%/74%). The kappa values for the grading of the humeral and glenoidal cartilage lesions were 0.81 and 0.55 for true FISP images compared with 0.49 and 0.43 for intermediate-weighted fast spin-echo images. Kappa values for true FISP evaluation of the anterior and posterior part of the labrum were 0.81 and 0.70. Transverse 3D true FISP MR arthrography images are useful for the difficult diagnosis of glenohumeral cartilage lesions and suitable for detecting labral abnormalities.

MRI of Pelvic Floor Dysfunction: Dynamic True Fast Imaging with Steady-State Precession Versus HASTE

The objective of our study was to retrospectively compare the degree of pelvic organ prolapse shown on dynamic true fast imaging with steady-state precession (FISP) versus HASTE sequences in symptomatic patients. Fifty-nine women (mean age, 57 years) with suspected pelvic floor dysfunction underwent MRI using both a sagittal true FISP sequence, acquired continuously during rest alternating with the Valsalva maneuver, and a sagittal HASTE sequence, acquired sequentially at rest and at maximal strain. Data sets were evaluated in random order by two radiologists in consensus using the pubococcygeal line (PCL) as a reference. Measurement of prolapse was based on a numeric grading system indicating severity as follows: no prolapse, 0; mild, 1; moderate, 2; or severe, 3. A comparison between sequences on a per-patient basis was performed using a Wilcoxon's analysis with p < 0.05 considered significant. Overall, 66.1% (39/59) of patients had more severe prolapse (>or= 1 degrees ) based on dynamic true FISP images, with 28.8% (17/59) of the cases of prolapse seen exclusively on true FISP images. Only 20.3% (12/59) of patients had greater degrees of prolapse on HASTE images than on true FISP images, with 10.2% (6/59) of the cases seen exclusively on HASTE images. A statistically significant increase in the severity of cystoceles (p < 0.01) and urethral hypermobility (p < 0.01)-with a trend toward more severe urethroceles (p < 0.07), vaginal prolapse (p < 0.09), and rectal descent (p < 0.06)-was shown on true FISP images. Overall, greater degrees of organ prolapse in all three compartments were found with a dynamic true FISP sequence compared with a sequential HASTE sequence. Near real-time continuous imaging with a dynamic true FISP sequence should be included in MR protocols to evaluate pelvic floor dysfunction in addition to dynamic multiplanar HASTE sequences.

Internal Knee Derangement Assessed with 3-minute Three-dimensional Isovoxel True FISP MR Sequence: Preliminary Study

To prospectively evaluate the accuracy of magnetic resonance (MR) imaging of the knee performed by using a three-dimensional (3D) isovoxel sequence involving an acquisition time of approximately 3 minutes, with surgery as the reference standard. The study was institutional review board approved. Written informed consent was obtained from all patients. Thirty knees of 29 patients (14 women, 15 men; mean age, 41 years) were prospectively examined by using a 3D isovoxel true fast imaging with steady-state precession (FISP) sequence with water excitation and secondary multiplanar reformations. All patients underwent arthroscopy within 12 days after true FISP MR imaging. Two blinded readers evaluated the MR images. Accuracy for detection of cartilage defects and anterior cruciate ligament (ACL) and meniscal tears, interobserver agreement, and intermethod agreement were calculated. Overall sensitivity, specificity, and accuracy of isovoxel true FISP imaging for the diagnosis of cartilage defects were 45%, 83%, and 76%, respectively, for reader 1 and 63%, 82%, and 83%, respectively, for reader 2. Averaged (for readers 1 and 2) sensitivity, specificity, and accuracy of isovoxel true FISP imaging were, respectively, 80%, 95%, and 90% for diagnosis of ACL tear; 100%, 82%, and 90% for diagnosis of medial meniscal tear; and 83%, 83%, and 83% for diagnosis of lateral meniscal tear. The standard MR sequences used at the authors' institution had overall sensitivities, specificities, and accuracies of 39%, 83%, and 71%, respectively, for reader 1 and 37%, 85%, and 76%, respectively, for reader 2. Averaged sensitivity, specificity, and accuracy of the standard MR sequences were, respectively, 70%, 100%, and 90% for diagnosis of ACL tear; 96%, 77%, and 85% for diagnosis of medial meniscal tear; and 83%, 77%, and 78% for diagnosis of lateral meniscal tear. The diagnostic performance of knee MR imaging performed by using a 3D water excitation isovoxel true FISP sequence and an imaging time of approximately 3 minutes is comparable to the diagnostic performance of the MR sequences used as standards at the authors' institution.

Is True FISP Imaging Reliable in the Evaluation of Venous Thrombosis?

The objective of our study was to evaluate the accuracy of true fast imaging with steady-state precession (FISP) in the diagnosis of venous thrombosis using gadolinium-enhanced 3D T1-weighted gradient-echo images and correlative imaging as the gold standard. Twenty-five MR examinations were retrospectively reviewed independently by two radiologists to rule out thrombosis in the central veins of the body. The presence of venous thrombus was assessed separately in 80 veins using true FISP and gadolinium-enhanced T1-weighted images. Diagnosis was confirmed by another imaging technique (sonography, CT, and/or conventional venography) in all positive cases. Negative examinations were confirmed using imaging, clinical follow-up, or both. Venous thrombosis was present in 25 veins in 18 patients. True FISP images had a lower sensitivity (66%) and specificity (70.9%) for the diagnosis of venous thrombosis than gadolinium-enhanced MR images (p < 0.01). True FISP images have lower sensitivity and specificity in the diagnosis of venous thrombosis than gadolinium-enhanced T1-weighted gradient-echo images. True FISP images should not be used exclusively for the diagnosis of venous thrombosis.

Phase-Sensitive Inversion-Recovery MR Imaging in the Detection of Myocardial Infarction

To prospectively determine if phase-sensitive inversion-recovery (IR) magnetic resonance (MR) imaging eliminates the need to find the precise inversion time (TI) to null the signal of normal myocardium to achieve high contrast between infarcted and normal myocardium. Informed consent was obtained from each patient for this prospective MR imaging research study, which was approved by the institutional review board. Twenty patients (16 men; four women; mean age, 56 years +/- 12.3) who experienced Q-wave myocardial infarction 2 weeks earlier were examined with a 1.5-T MR system 10 minutes after administration of 0.1 mmol per kilogram of body weight gadobenate dimeglumine. To determine the optimal TI, a TI scout sequence was used. A segmented two-dimensional IR turbo fast low-angle shot (FLASH) sequence and a segmented two-dimensional IR true fast imaging with steady-state precession (FISP) sequence that produces both phase-sensitive and magnitude-reconstructed images were used at TI values of 200-600 msec (TI values were varied in 100-msec steps) and at optimal TI (mean value, 330 msec). Contrast-to-noise ratios (CNRs) of normal and infarcted myocardium and the area of infarcted myocardium were determined. Magnitude-reconstructed IR turbo FLASH images were compared with magnitude-reconstructed and phase-sensitive IR true FISP images. Two-tailed unpaired sample Student t test was used to compare CNRs, and two-tailed paired-sample Student t test was used to compare area of infarction. Mean CNR of images acquired with IR turbo FLASH and IR true FISP (phase-sensitive and magnitude-reconstructed images) at optimal TI (mean value, 330 msec) were 6.6, 6.2, and 6.1, respectively. For a TI of 200 msec, CNR values were -4.3, -4.0, and 7.2, respectively; for TI of 600 msec, CNR values were 3.1, 3.3, and 4.3, respectively. Area of infarcted myocardium was underestimated on magnitude-reconstruction images (P = .002-.03) for short TI values (ie, 200 msec) for both sequences and for a TI of 300 msec for IR true FISP but not on phase-sensitive reconstructed IR true FISP images when compared with IR turbo FLASH images obtained at optimal TI. Phase-sensitive image reconstruction results in reduced need for precise choice of TI and more consistent image quality.

Comparison of True FISP with Turbo SE in Ovarian Imaging

To compare the signal pattern of True FISP (true fast imaging with steady state precession) with that of T2-weighted TSE (turbo spin echo) sequencing in several ovarian pathologies and to clarify the pathologies that may be misdiagnosed when True FISP is used as a fast T2-weighted MR (magnetic resonance) imaging technique. A total of 56 patients with 58 ovarian lesions were prospectively studied. The histopathological diagnoses were surgically confirmed in all patients. All MR images were acquired with a 1.5T MR scanner. After routine MR examination (T2-weighted sagittal imaging with a turbo spin echo sequence and T1 and T2 transverse imaging with a spin echo and turbo spin echo sequence, respectively), True FISP was performed in the sagittal plane with a fat-saturation technique. The acquisition times for the True FISP and TSE techniques were 27 s and 4 min, 42 s, respectively. Three radiologists interpreted all images according to three grading scores and with particular reference to the difference in signal pattern between the two sequences (1=similar signal patterns in the ovarian lesions in both True FISP and TSE images; 2=partially different signal patterns in both True FISP and TSE images; and 3=conflicting signal patterns in both True FISP and TSE images). Those assigned a score of "1" included 30 patients with 30 ovarian lesions (12 malignant lesions and 18 benign lesions); those assigned a score of "2" included 10 patients with 10 lesions (two malignant and eight benign); and those assigned a score of "3" included 16 patients with 18 ovarian lesions (two malignant and 16 benign). With the influence of the fat-suppression technique excluded, eight ovarian lesions showed conflicting signal patterns between the two sequences and high signal intensity of hemorrhaging in the corresponding lesion in T1-weighted images. Lesions of both high and low signal intensity in TSE images appeared as lesions of high signal intensity in True FISP images. About 14% (8/56 lesions) of the True FISP and TSE signal patterns in ovarian pathology were conflicting in this study. The results indicate that the True FISP technique cannot replace the T2-weighted TSE technique in the evaluation of ovarian pathology. T1-weighted images with or without fat suppression are required for the evaluation of ovarian lesions with FISP images.

Preoperative Evaluation of the Entire Hepatic Vasculature in Living Liver Donors with Use of Contrast-enhanced MR Angiography and True Fast Imaging with Steady-state Precession

To preoperatively assess the entire hepatic vasculature in living related liver donors with use of a combination of contrast material-enhanced magnetic resonance (MR) angiography and true fast imaging with steady-state precession (FISP). Twenty-five living potential liver donors were examined preoperatively on a 1.5T Siemens Sonata system. Twenty-four underwent surgery and two had catheter angiography performed to delineate complex anatomy. Contiguous 5-mm-thick, sub-second true FISP images of the liver were initially obtained during breath-holding in axial and coronal planes (repetition time [TR]/echo time [TE], 3.2/1.6; flip angle, 70 degrees ). MR angiography was performed with use of a three-dimensional (3D) gradient-echo fast low-angle shot (FLASH) pulse sequence (TR/TE, 3.0/1.2; flip angle, 25 degrees ), with 40 mL of Gadolinium DTPA injected at a rate of 2 mL/sec. One precontrast and two postcontrast coronal 3D volumes were acquired, each in a 20-second breath-hold, and two subtracted 3D sets were calculated. Arterial anatomy was assessed with use of maximum-intensity projection, volume rendering, and multiplanar reformatting algorithms. Hepatic and portal venous anatomy was evaluated with use of the true FISP images and the venous phase of the MR angiogram. Visualization of hepatic arterial branches was noted. Visualization of portal vein branches was scored on a scale of 0-5. The presence of anatomic variants was noted. Vascular anatomy was confirmed at the time of surgery and at catheter angiography. Segmental branch vessels were visualized on MR angiography in the majority of cases. The segment four branch was identified in 96% patients. Variant arterial anatomy was seen in 50% of patients. MR angiography detected 10 of 11 arterial variants found at surgery and angiography. Visualization of portal vein branches was generally higher with true FISP compared to MR angiography. Twenty-four percent of patients had variant portal venous anatomy. Caudal hepatic veins were identified in 60% of patients, of which eight were significant (>5 mm). Hepatic and portal venous anatomy was accurately predicted by true FISP and MR angiography in all patients who went on to undergo surgery. Preoperative imaging with use of a combination of contrast-enhanced MR angiography and true FISP provides a comprehensive assessment of the entire hepatic vasculature in living liver donors.

Juxtapapillary diverticulum: findings on MRI.

The purpose of our study was to describe the imaging findings of juxtapapillary diverticulum on magnetic resonance imaging (MRI). The MRI and magnetic resonance cholangiopancreatography (MRCP) examinations of 14 patients with juxtapapillary diverticula that were diagnosed on endoscopic retrograde cholangiopancreatography (ERCP) (N = 8) or endoscopy (N = 6) were retrospectively evaluated. T1-weighted spoiled gradient-echo, T2-weighted half Fourier single shot fast spin-echo (HASTE), and T2-weighted True FISP (fast imaging with steady state precession) images and thin-slice MRCP images were obtained on all patients. In five patients, diluted gadolinium DPTA (1/100) was used as an oral contrast. T2-weighted True FISP and HASTE images demonstrated air-fluid levels within all diverticula. Hyperintense oral contrast on T1-weighted spoiled gradient-echo images aided detection of the smaller diverticula. MRCP images obtained in the coronal plane best demonstrated the relationship of the diverticula to the papilla. MRI with the use of HASTE, True FISP, and oral contrast-enhanced T1-weighted sequences was able to depict juxtapapillary diverticula in our series.

TrueFISP—technical considerations and cardiovascular applications

Magnetic resonance imaging (MRI) using steady-state free precession (SSFP) sequences was described in the early years of MR imaging. However, due to hardware imperfections, these techniques were not robust enough at the time to play any significant role in clinical MRI. More recently, significant hardware improvements became widely available, and the SSFP sequences such as TrueFISP (true fast imaging with steady-state precession) became very popular for a variety of clinical applications due to the distinct improvements in signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). The purpose of this article is to give an overview on the basics of TrueFISP imaging and to demonstrate its potential for current clinical applications with a focus on cardiovascular MRI.

MRI of the liver: can True FISP replace HASTE?

To determine the diagnostic accuracy of two fast breath-hold magnetic resonance (MR) imaging sequences, half-Fourier acquired single turbo spin-echo (HASTE) and true fast imaging with steady state precession (TrueFISP), for the detection and characterization of focal liver lesions A total of 186 patients with suspected focal liver lesions were enrolled in this study. All patients underwent the same standardized study protocol including HASTE and TrueFISP. A consensus reading based on all available image data served as a standard of reference for classifying lesions into cysts, hemangiomas, focal nodular hyperplasia, or malignant/other lesions. All malignant lesions, as well as hepatic adenomas and abscesses, were histologically verified. Each separated by an eight-week interval, HASTE and TrueFISP images were retrospectively reviewed in random order for the detection and characterization of focal hepatic lesions. Finally, a receiver operating characteristic (ROC) analysis was calculated. HASTE images had an overall sensitivity of 0.86 and a specificity of 0.91, whereas TrueFISP showed an overall sensitivity and specificity of 0.79 and 0.83, respectively (p>0.1). Neither HASTE nor TrueFISP alone are sufficient for the detection and characterization of hepatic lesions.

TrueFISP: assessment of accuracy for measurement of left ventricular mass in an animal model.

To test the accuracy of a high performance true fast imaging with steady-state precession (TrueFISP) pulse sequence for the assessment of left ventricular (LV) mass in a large animal model on 1.5-T scanners. We imaged dogs (N = 10) on a clinical 1.5-T clinical scanner using electrocardiogram (ECG)-gated TrueFISP. In all animals, contiguous segmented k-space cine images were acquired from base to apex (in-plane resolution 1 x 1 mm(2), slice thickness 5 mm, TR = 4.8 msec, TE = 1.6 msec) during repeated breath-holds. In nine of the 10 animals, single-shot images gated to end-diastole were also acquired from base to apex in a single breath-hold (in-plane resolution 1 x 1 mm(2), slice thickness 5 mm, TR = 3.2 msec, TE = 1.6 msec). After imaging, animals were killed, the left ventricle was isolated, and the true mass of the left ventricle (free wall and septum) was determined. Independently, two observers blinded to the post-mortem results computed LV masses based on analysis of the magnetic resonance (MR) images. Comparison of the computed LV mass using TrueFISP to the actual mass showed excellent agreement. Cine-systole was the most accurate technique (mass = 98.6% +/- 4.5% actual, bias = 1.2 +/- 3.4 g) followed by cine-diastole (mass = 97.9% +/- 5.3% actual, bias = 1.8 +/- 4.1 g) and single shot (mass = 94.7% +/- 7.9% actual, bias = 4.2 +/- 6.3 g). Inter- and intra-observer variabilities were low (5.8% +/- 7.1% and 0.4% +/- 4.8%, respectively). We conclude that TrueFISP imaging is an accurate, rapid method to determine ventricular mass. In single-shot mode, TrueFISP requires only one breath-hold to estimate the mass of the heart within 6% of the actual value, whereas the segmented k-space implementation measured LV mass to within 3% of the true value.