Lumbar myelography with three-dimensional MR imaging.

A strongly T2*-weighted, three-dimensional (3D) PSIF (time-reversed FISP [fast imaging with steady-state precession]) gradient-echo magnetic resonance (MR) sequence, with postprocessing of the 3D data set with a maximum-intensity projection (MIP) algorithm, produced x-ray myelography-equivalent images. The method was tested in 10 healthy volunteers to optimize sequence parameters and was evaluated in 30 patients with proven lumbar disk disease. MIP myelograms, unlike two-dimensional MR images, could not show the pathologic disks themselves but clearly demonstrated the effect on the thecal sac, giving a clear overall view of its geometry and dimensions, especially when displayed in a cine loop. All 28 medial and mediolateral disk herniations could be visualized, whereas only three of eight intraforminal disk herniations were seen on MR myelograms.     

CSF flow studies of intracranial cysts and cyst-like lesions achieved using reversed fast imaging with steady-state precession MR sequences

BACKGROUND AND PURPOSE: Differentiating between intracranial cysts or cyst-like structures and communicating or noncommunicating cysts is often not possible with cranial CT or nonfunctional MR imaging. We evaluated a retrospective ECG-gated fast imaging with steady-state precession (PSIF) MR sequence with optional cine mode to differentiate cystic masses from enlarged CSF spaces and to determine the accuracy of detecting communication between cysts and neighboring CSF spaces. METHODS: Fourteen patients with intracranial cystic masses underwent CSF flow studies with an ungated and a retrospective ECG-gated cine-mode PSIF sequence in addition to spin-echo imaging. Findings were evaluated retrospectively by using a five-point rating scale and without knowledge of clinical or other imaging findings. Results were compared with intraoperative findings or with results of intrathecal contrast studies. RESULTS: Eighteen arachnoid cysts and one enlarged cisterna magna were diagnosed. Improved differentiation between cysts and enlarged CSF spaces was obtained with cine-mode PSIF imaging in six lesions (six patients). Increased diagnostic certainty as to communication between cysts and CSF spaces was obtained in 18 cysts (13 patients). Diagnoses were verified by membranectomy in five lesions, by CT cisternography in five lesions, and indirectly by shunting in one cystic lesion. In one case, MR diagnosis was not confirmed by CT cisternography. CONCLUSION: Cine-mode MR imaging with a retrospective ECG-gated flow-sensitive PSIF sequence contributed to the certainty of communication between arachnoid cysts and neighboring CSF spaces with an accuracy of 90%, using surgical findings or intrathecal contrast studies as reference. Differentiation between intracranial cysts and enlargement of CSF spaces and other cystic masses was improved in 25% of cases.     

Cardiac magnetic resonance imaging using an open 0.35 T system

OBJECTIVE: To evaluate cardiac magnetic resonance imaging (MRI) using a 0.35 T magnetic resonance system with open design. METHODS: Eleven patients were examined in an open MRI system with a field strength of 0.35 T. Myocardial function was assessed with cine true fast imaging with steady-state precession sequences in 2 planes. Perfusion images were acquired with a T1-weighted gradient echo sequence. Late enhancement was performed using an inversion recovery-prepared fast gradient echo technique. Image quality was assessed using a 4-point score in consensus. Signal-noise ratio was measured. RESULTS: For functional imaging, average score was 1.65 (SD, 0.6). For perfusion imaging, the value was 2.25 (SD, 0.68). For late enhancement, quality score was 2.6 (SD, 0.82). Average value of signal-noise ratio for functional, perfusion, and late enhancement imaging was 50.6 (SD, 16.4), 91.8 (SD, 52.8), and 33.2 (SD, 20.4), respectively. CONCLUSIONS: Open MRI with lower field strength can be used for functional imaging of the heart. For perfusion and viability imaging (late enhancement), higher field strength is needed. Open low-field cardiac MRI may provide a helpful alternative for obese or claustrophobic patients or patients who are difficult to move.     

MR cisternography: a new method for the diagnosis of CSF fistulae

The aim of this study was to compare a new MRI method for detecting the existence of cerebrospinal fluid (CSF) fistulae, i. e. MR cisternography, with CT cisternography. In a prospective study, 30 patients with post-traumatic CSF fistulae were examined. The MR examinations were performed with a 1.0-T whole-body MR system, using two T2^*-weighted sequences, a 3D PSIF (time-inversed fast imaging with steady-state precession, FISP) and a 3D constructive interference steady-state (CISS) sequence. The results of MRI and CT cisternography were compared with the surgical findings. The sensitivity in detecting CSF fistulae with MR cisternography (PSIF: 89.9 %; CISS: 93.6 %) was higher than with CT cisternography (72.3 %). The sensitivity of CT cisternography at detecting CSF fistulae in patients with a size of dural lesion less than 2 mm or in patients with multiple dural lesions is significantly lower compared with the MR method. Although the localization of CSF fistulae always proved possible with MR cisternography, this could only be accomplished wih CT in 70 % of cases. The MR cisternography technique is a new examination method with a higher sensitivity for the detection of CSF fistulae than CT cisternography. The CISS technique is superior compared with PSIF and should be used in patients with high-flow CSF fistulas. Received 15 July 1996; Revision received 15 January 1997; Accepted 25 February 1997     

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.     

SPAMM, cine phase contrast imaging and fast spin-echo T2-weighted imaging in the study of intracranial cerebrospinal fluid (CSF) flow

AIM: To compare the qualitative assessment of cerebrospinal fluid (CSF) flow using a SPAMM (spatial modulation of magnetization) technique with cine phase contrast images (cine PC) and fast spin echo (FSE) T2-weighted images. MATERIALS AND METHODS: SPAMM, PC and T2-weighted sequences were performed on 22 occasions in 19 patients. Eleven of the studies were performed following a neuroendoscopic third ventriculostomy (NTV), and in these cases, the success of the NTV was determined by clinical follow-up. Two observers used consensus to grade the presence of CSF flow at nine different sites for each study. RESULTS: At 14 of the 178 matched sites, which could be assessed by both SPAMM and cine PC, SPAMM CSF flow grade was higher than that of cine PC. At a further 14/178 matched sites, the cine PC grade was higher than that of SPAMM. There was definite CSF flow at 113/182 (62%) of all the cine PC sites assessed, and 110/181 (61%) of all SPAMM sites assessed whilst 108/198 (54%) of FSE T2-weighted image sites demonstrated flow voids. Cine PC grades were higher than SPAMM at the cerebral aqueduct (P < 0.05, Wilcoxon sign rank test). Definite CSF flow within the anterior third ventricle was present in 4/5 (SPAMM) and 3/5 (cine PC) successful NTVs, 0/2 (SPAMM and cine PC) unsuccessful NTVs and 1/10 (SPAMM and cine PC) patients without NTV. CONCLUSION: SPAMM provides a comparable assessment of intracranial CSF flow to that of cine phase contrast imaging at all CSF sites except the cerebral aqueduct.     

Evaluation of esophageal peristalsis in patients with esophageal tumors: initial experience with cine MR imaging.

We evaluated esophageal peristalsis in patients with esophageal tumors by cine MR using steady-state free precession (SSFP) sequence and correlated the alteration of the esophageal peristalsis with clinical symptoms and tumor stages. Thirteen patients with pathologically proven esophageal tumors, including 12 esophageal cancers and one submucosal leiomyoma, underwent cine MRI using true fast imaging with steady precession (trueFISP) sequence, which is one SSFP sequence, after contrast-enhanced MR scanning for clinical purposes. A total of 120 serial images were obtained within 60 s through the plane along the long axis of the esophagus while patients chewed gum. The serial trueFISP images were evaluated for the presence, frequency, speed of progression, and passage of peristalsis through the tumor. The data from cine MRI were compared with clinical symptoms and tumor stages. Peristalsis was clearly identified in all patients. Seven patients with complete interruption of peristalsis had dysphagia; one with partially impaired peristalsis could intake solid foods with discomfort; and two with partially impaired peristalsis and three with preserved peristalsis remained asymptomatic. Patients with complete or partial interruption of peristalsis had Stage T3 or T4 esophageal cancer. In conclusion, trueFISP cine MR imaging enables direct visualization of esophageal peristalsis in relation to esophageal tumors. Complete interruption of peristalsis causes dysphagia, whereas partial interruption of and preserved peristalsis usually do not cause digestive problems. Interruption of peristalsis may indicate impaired muscle function caused by invasion of advanced esophageal cancers.     

Spontaneous ventriculostomy: report of three cases revealed by flow-sensitive phase-contrast cine MR imaging.

Spontaneous ventriculostomy is a rare condition that occurs with the spontaneous rupture of a ventricle, resulting in a communication between the ventricular system and the subarachnoid space. Three cases of spontaneous ventriculostomy through the floor of the third ventricle that occurred in cases of chronic obstructive hydrocephalus are presented. The communication was identified via flow-sensitive phase-contrast cine MR imaging. Spontaneous ventriculostomy is probably a result of a rupture of the normally thin membrane that forms the floor of the third ventricle and, with long-standing obstructive hydrocephalus, creates an internal drainage pathway that spontaneously compensates for the hydrocephalus.     

Steady-state diffusion imaging for MR in-vivo evaluation of reparative cartilage after matrix-associated autologous chondrocyte transplantation at 3 tesla--preliminary results

OBJECTIVES: To demonstrate the feasibility of time-reversed fast imaging with steady-state precession (FISP) called PSIF for diffusion-weighted imaging of cartilage and cartilage transplants in a clinical study. MATERIAL AND METHODS: In a cross-sectional study 15 patients underwent MRI using a 3D partially balanced steady-state gradient echo pulse sequence with and without diffusion weighting at two different time points after matrix-associated autologous cartilage transplantation (MACT). Mean diffusion quotients (signal intensity without diffusion-weighting divided by signal intensity with diffusion weighting) within the cartilage transplants were compared to diffusion quotients found in normal cartilage. RESULTS: The global diffusion quotient found in repair cartilage was significantly higher than diffusion values in normal cartilage (p<0.05). There was a decrease between the earlier and the later time point after surgery. CONCLUSIONS: In-vivo diffusion-weighted imaging based on the PSIF technique is possible. Our preliminary results show follow-up of cartilage transplant maturation in patients may provide additional information to morphological assessment.     

Magnetic resonance imaging versus ultrasonography in fetal pathology

PURPOSE: This paper describes our experience with magnetic resonance imaging (MRI) in the assessment of fetal anatomical structures and major fetal pathologies. MATERIALS AND METHODS: The retrospective study included 128 pregnant women between the 22nd and 38th week of gestation. We used the following imaging protocol: T2-weighted single-shot fast spin-echo sequences for all foetuses and, in selected cases, gradient echo with steady-state free precession (SSFP), T1-weighted spoiled gradient echo [fast low-angle shot (FLASH)] with and without fat saturation, and T2 thick-slab sequences with multiplanar technique. In 32 cases, we performed diffusion-weighted sequences with apparent diffusion coefficient (ACD) maps on the brain, the kidneys and the lungs. RESULTS: We achieved diagnostic-quality images in 125 of 128 patients; MR image quality was unsatisfactory in three cases only. In 16 cases with previous negative ultrasound (US) findings, MRI confirmed the US diagnosis. MRI confirmed the positive US diagnosis in 67 of 109 cases (61.5%); in 11 cases it changed the US diagnosis, and in 31/109 the examination was negative. In addition, MRI identified other anomalies not recognised during US examination. CONCLUSIONS: With its ultrafast sequences, fetal MRI provides good detail of normal fetal anatomy and allows characterisation of suspected anomalies.     

Velocity and flow quantitation in the superior sagittal sinus with ungated and cine (gated) phase-contrast MR imaging

Normal blood flow and velocity in the superior sagittal sinus were measured in 30 patients. A fast two-dimensional ungated phase-contrast (PC) pulse sequence was compared with a peripherally gated cine PC technique for velocity and flow quantitation. The same imaging parameters were used for both methods. Measured values for mean velocity and flow obtained with the two methods were compared by using regression analysis and t testing. For blood flow, the correlation coefficient was 0.976. For velocity measurements, r was 0.950. Mean flow was 285 mL/min ± 19 with the ungated PC method and 281 mL/min ± 19 with the cine PC method. The mean velocities measured with the two methods were 12.94 cm/sec ± 1.1 and 13.59 cm/sec ± 1.1, respectively. There was no significant difference (paired t test) between the methods for mean flow or velocity data. This was true even though flow in the superior sagittal sinus is moderately pulsatile, as shown with the cine PC technique. The ungated PC method provided these data in 13 seconds versus 3.5 minutes for the cine PC method.     

Externally placed vs intravaginally positioned radio frequency coils for quantitative spin-spin relaxometry of ovarian follicular fluid.

OBJECTIVE: To evaluate different imaging protocols, especially with respect to radio frequency (RF) receiver coil location, for their suitability in providing least squares derived quantitative T2 values of ovarian follicular fluid for investigations of basic ovarian physiology. METHODS: The ovaries of 10 women were imaged via magnetic resonance imaging (MRI) using externally positioned and intravaginally placed RF receiver coils. Half-Fourier acquisition with single-shot turbo spin-echo (HASTE), multiple-echo T2, Dixon, turbo spin-echo, and 3-dimensional (3D) fast imaging with steady-state precession (FISP) and time-reversed FISP (PSIF) sequences were used. Quantitative T2 nuclear spin relaxation rate information from the ovarian follicles between data acquired with the external and intravaginal coils were compared. Additionally, the amount of ovarian follicle and corpora lutea structural detail visible was qualitatively assessed. RESULTS: The T2 computations indicated that there was no difference in the follicular fluid T2 values or in the heterogeneity (spatial variance) of the T2 values between data acquired with the external RF coil and data acquired with the intravaginal RF coil. The best sequences for the visualization of ovarian internal structure were the 3D PSIF sequences and the multiple-echo T2-weighted images, confirming our earlier imaging work on excised cow ovaries. CONCLUSION: It is best to use an externally placed RF coil for quantitative MRI study of ovarian physiology given the lack of difference in quantitative T2 information and the difficulty associated with imaging the ovaries using an intravaginal RF probe.     

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.     

Cine MR angiography of the heart with segmented true fast imaging with steady-state precession

In five healthy subjects and 18 patients, cine magnetic resonance (MR) imaging of the heart was performed with a true fast imaging with steady-state precession (FISP) sequence. Results were compared both quantitatively and qualitatively with those at cine fast low-angle shot (FLASH) MR imaging. The blood-myocardial contrast-to-noise ratio (CNR) was 2.0 times higher and the normalized (for measurement time and pixel size) blood-myocardial CNR was 4.0 times higher for true FISP compared with FLASH MR imaging. Qualitative scores for image quality were significantly higher with true FISP MR imaging. Segmented cine true FISP MR imaging generated high-contrast MR images of the heart in healthy subjects and in patients with heart disease and produced image quality superior to that with cine FLASH MR imaging.     

Fast MR imaging of liver metastasis using FLASH and FISP--optimal sequences for T1- and T2*-weighted images

This paper deals with a study to obtain the optimal sequence of gradient echo (GE) for T1- and T2*-weighted images similar to T1- and T2-weighted images of spin echo (SE). Two GE sequences, fast low angle shot (FLASH) and fast imaging with steady-state precession (FISP), were performed in 15 cases of liver metastasis in various combination of flip angle (FA), repetition time (TR), and echo time (TE). The optimal combinations were summarized as follows: 1) T1-weighted FLASH image with FA of 40 degrees, TR of 22 msec and TE of 10 msec, 2) T1-weighted FISP image with FA of 70 degrees, TR of 100 msec, TE of 10 msec, 3) both T2*-weighted FLASH and FISP images with FA of 10 degrees, TR of 100 msec and TE of 30 msec. Not only to provide the adequate T1- and T2*-weighted images but also to enable breath-holding MR imaging, GE sequences can optionally take place SE in cases of deteriorated images caused by moving artifacts. Other applications support the re-examination and further detailing when required, conveniently rather in short time.     

T1-weighted magnetic resonance imaging shows fatty deposition after myocardial infarction.

Pathologic studies have shown an increased lipid content in areas of myocardial infarction (MI). We sought to show the ability of precontrast T1-weighted MRI to noninvasively detect fat deposition in MI and show its association with infarct age. Thirty-two patients with MI were studied. Precontrast inversion-recovery (IR) cine steady-state free precession (SSFP) imaging was used to generate both fat- and muscle-nulled images to locate areas of fat deposition in the left ventricular (LV) myocardium. Postcontrast delayed hyperenhanced (DHE) imaging was also performed. Image contrast in regions of MI on precontrast images and postcontrast DHE images was measured. The association of image contrast with infarct age was determined by means of correlations and Student's t-test. We found a significant association between infarct age and image contrast in both fat- and muscle-nulled images. Precontrast T1-weighted MRI is a promising method for detecting myocardial fat deposition in chronic MI, and can be used to assess myocardial infarct age.     

Segmented k-space and real-time cardiac cine MR imaging with radial trajectories.

The authors developed and evaluated two cine magnetic resonance (MR) imaging sequences with a radial rather than a rectilinear k-space coordinate frame: segmented k space and real-time true fast imaging with steady-state precession, or FISP. The two radial k-space segmentation (or view sharing) techniques, which were interleaved or continuous, were compared, and the feasibility of their application in cardiac cine MR imaging was explored in phantom and volunteer studies. Images obtained with the radial sequences were compared with those obtained with two-dimensional Fourier transform, or 2DFT, sequences currently used in cine MR imaging. Temporal resolution of 55 msec was achieved with the real-time radial sequences, which allowed acquisition of almost 19 high-quality images per second.     

Comparison of MR imaging sequences for liver and head and neck interventions: is there a single optimal sequence for all purposes?

RATIONALE AND OBJECTIVES: To compare the appropriate pulse sequences for interventional device guidance during magnetic resonance (MR) imaging at 0.2 T and to evaluate the dependence of sequence selection on the anatomic region of the procedure. MATERIALS AND METHODS: Using a C-arm 0.2 T system, four interventional MR sequences were applied in 23 liver cases and during MR-guided neck interventions in 13 patients. The imaging protocol consisted of: multislice turbo spin echo (TSE) T2w, sequential-slice fast imaging with steady precession (FISP), a time-reversed version of FISP (PSIF), and FISP with balanced gradients in all spatial directions (True-FISP) sequences. Vessel conspicuity was rated and contrast-to-noise ratio (CNR) was calculated for each sequence and a differential receiver operating characteristic was performed. RESULTS: Liver findings were detected in 96% using the TSE sequence. PSIF, FISP, and True-FISP imaging showed lesions in 91%, 61%, and 65%, respectively. The TSE sequence offered the best CNR, followed by PSIF imaging. Differential receiver operating characteristic analysis also rated TSE and PSIF to be the superior sequences. Lesions in the head and neck were detected in all cases by TSE and FISP, in 92% using True-FISP, and in 84% using PSIF. True-FISP offered the best CNR, followed by TSE imaging. Vessels appeared bright on FISP and True-FISP imaging and dark on the other sequences. CONCLUSION: In interventional MR imaging, no single sequence fits all purposes. Image guidance for interventional MR during liver procedures is best achieved by PSIF or TSE, whereas biopsies in the head and neck are best performed using FISP or True-FISP sequences.     

Diffusion-prepared fast imaging with steady-state free precession (DP-FISP): a rapid diffusion MRI technique at 7 T

Diffusion MRI is a useful imaging technique with many clinical applications. Many diffusion MRI studies have utilized echo-planar imaging (EPI) acquisition techniques. In this study, we have developed a rapid diffusion-prepared fast imaging with steady-state free precession MRI acquisition for a preclinical 7T scanner providing diffusion-weighted images in less than 500 ms and diffusion tensor imaging assessments in ～1 min with minimal image artifacts in comparison with EPI. Phantom apparent diffusion coefficient (ADC) and fractional anisotropy (FA) assessments obtained from the diffusion-prepared fast imaging with steady-state free precession (DP-FISP) acquisition resulted in good agreement with EPI and spin echo diffusion methods. The mean apparent diffusion coefficient was 2.0 × 10(-3) mm(2) /s, 1.90 × 10(-3) mm(2) /s, and 1.97 × 10(-3) mm(2) /s for DP-FISP, diffusion-weighted spin echo, and diffusion-weighted EPI, respectively. The mean fractional anisotropy was 0.073, 0.072, and 0.070 for diffusion-prepared fast imaging with steady-state free precession, diffusion-weighted spin echo, and diffusion-weighted EPI, respectively. Initial in vivo studies show reasonable ADC values in a normal mouse brain and polycystic rat kidneys.     

Real-time interactive MR imaging system: sequence optimization, and basic and clinical evaluations

A real-time interactive MR imaging system (real-time MRI) is an MR scanner which has a fast image updating cycle and the ability to freely change slice orientation, just like an ultrasound imaging system. Recently, such a system has been developed and installed on a clinical 1.5-Tesla system. The purpose of this study was to optimize the pulse sequences for clinical use and to evaluate the clinical usefulness and basic functionality of real-time MRI. For T1-weighted imaging, FLASH (fast low angle shot) can be selected, and up to 5 frames per second can be acquired depending on the matrix size. For T2-weighted imaging, true FISP (fast imaging with steady-state precession) can be selected, and up to 4 frames per second can be acquired. Maximum C/N between liver and spleen was obtained at a flip angle of 20 degrees on FLASH. Maximum C/N between cardiac cavity and wall was obtained at a flip angle of 60 degrees on true FISP. Localization of the right and left coronary arteries could be performed within 30 seconds in three volunteers. Although the present real-time MRI system has drawbacks such as low spatial resolution and relatively low contrast resolution, we expect real-time MRI to be one of the most important tools for future clinical MRI.