Field Echo Magnetic Resonance Imaging Research Articles

Preoperative assessment of the individual anatomy of the superior petrosal vein complex using balanced fast field echo magnetic resonance imaging.

Here, we sought to examine the validity and reproducibility of balanced fast field echo (bFFE) for assessing superior petrosal vein (SPV) complex (SPVC) anatomy. Preoperative bFFE or equivalent scans and operative videos were studied and directly compared with regard to the individual anatomical features of SPVCs and their relation to the operative field. The anatomical details of the bFFE findings of the non-operated side (group 2) of all 50 patients were then reviewed, including the presence of petrosal-galenic anastomosis, and finally compared to the operated SPVCs (group 1). A complete correlation between bFFE and intraoperative findings was observed in 62% of cases and had a significant correlation with 3 Tesla magnet strength and higher pixel bandwidth (rbis = -0.47; p = 0.005). The sensitivity and specificity of bFFE magnetic resonance imaging were 93.7 and 95.2%, respectively, for detecting an SPV disturbing the operative field, and 97.3% and 95% for a disturbing tributary, respectively. Each group had 50 SPVCs, with a total of 70 and 64 SPVs, 10 and 11 general SPVC configurations, as well as 29 and 28 different individual anatomical variations in groups 1 and 2, respectively. Both groups had 1-3 SPVs with a similar distribution of frequencies [Chi-square (4) = 27.56; p = 0.0145 (Fisher's exact test)]. The similarity of the general configurations was not statistically significant. The same four predominant configurations constituted 80% of the SPVCs in each group. The vein of the cerebellopontine fissure was most frequently found in 86% and 88% of cases, and a petrosal-galenic anastomosis was seen in 38% and 40% of groups 1 and 2, respectively. Individual SPVC variations are extensive. Good quality bFFE or equivalents are feasible for preoperative SPVC assessments. However, methods improving vascular visualization are recommended.

Diagnostic Accuracy of Three-dimensional Turbo Field Echo Magnetic Resonance Imaging Sequence in Pediatric Tracheobronchial Anomalies with Congenital Heart Disease

Tracheobronchial anomalies are common in congenital heart disease (CHD), including tracheobronchial stenosis, tracheal bronchus, cardiac bronchus, and bronchial isomerism, which can cause varying degrees of respiratory illness. It is necessary to assess tracheobronchial anomalies and make a preoperative airway evaluation. Multi-slice computed tomography (MSCT) and cardiac magnetic resonance imaging (MRI) are the most effective noninvasive modalities for the diagnosis of CHD and the associated tracheobronchial anomalies. However, MSCT remains an ionizing procedure despite using low dose protocols. The aim of this study was to evaluate diagnostic accuracy of tracheobronchial anomalies in patients with CHD using three-dimensional turbo field echo(3D-TFE) magnetic resonance imaging sequence for preoperative airway evaluation. The results indicated that 3D-TFE provided better image quality as compared to that of 3D-balanced turbo field echo (3D-bTFE), and it can clearly demonstrated the tracheobronchial tree and tracheobronchial anomalies in CHD. This study confirms the clinical value of 3D-TFE in diagnosing tracheobronchial anomalies and supply helpful tracheobronchial information for preoperative strategies and postoperative follow-up.

Usefulness of multiecho fast field echo MRI in the evaluation of ossification of the posterior longitudinal ligament and dural ossification of the cervical spine.

ObjectivesThe diagnosis of ossification of the posterior longitudinal ligament (OPLL) on magnetic resonance imaging (MRI) is challenging. The purpose of this study is to evaluate the usefulness of the multiecho fast field echo (mFFE) MRI in the detection of ossification of the posterior longitudinal ligament and dural ossification (DO) of the cervical spine.MethodsSixty-three patients who underwent MRI with mFFE and CT for cervical spine were retrospectively evaluated. The presence of OPLL and DO on MR images was assessed by two independent readers. The sensitivity, specificity, and accuracy of MRI for detecting OPLL and DO were determined using CT as a reference standard. Image contrast ratios were obtained between the OPLL and perilesional structures on each sequence.ResultsThere were 31 patients with OPLL and 13 DO lesions. The mean sensitivity, specificity, and accuracy of both readers were 94%, 81%, 88% for OPLL and 92%, 81%, 86% for DO, respectively. The contrast ratios for OPLL and intervertebral disc, spinal cord and cerebrospinal fluid were significantly superior on mFFE images, whereas those for OPLL and bone marrow were significantly inferior on mFFE images than those of T1-and T2-weighted images (p ≤ 0.016).ConclusionsMRI with mFFE may be sufficient for the assessment of OPLL and DO, with good contrasts between OPLL and intervertebral disc, spinal cord, and cerebrospinal fluid.

Use of Non-Invasive Phase Contrast Magnetic Resonance Imaging for Estimation of Atrial Septal Defect Size and Morphology: A Comparison with Transesophageal Echo

Transesophageal echocardiography (TEE) is a trusted method of sizing atrial septal defect (ASD) prior to percutaneous closure but is invasive, uncomfortable, and may carry a small risk of morbidity and mortality. Magnetic resonance imaging (MRI) may be useful non-invasive alternative in such patients who refuse or are unable to tolerate TEE and may provide additional information on the shape of the A0SD. To validate the accuracy of ASD sizing by MRI compared with TEE. Twelve patients (mean age 30 years; range 11-60 years) scheduled for ASD closure underwent TEE, cine balanced fast field echo MRI (bFFE-MRI) in four-chamber and sagittal views and phase-contrast MRI (PC-MRI) with reconstruction using the two orthogonal planes of T2-weighted images as planning. The average of the three longest measurements for all imaging modalities was calculated for each patient. Mean maximum ASD length on TEE was 18.8 +/- 4.6 mm, mean length by bFFE-MRI was 20.0 +/- 5.0 mm, and mean length by PC-MRI was 18.3 +/- 3.6 mm. The TEE measurement was significantly correlated with the bFFE-MRI and PC-MRI measurements (Pearson r = 0.69, p = 0.02 and r = 0.59, p = 0.04, respectively). The mean difference between TEE and bFFE-MRI measurements was -1.2mm (95% CI: -3.7, 1.3) and between TEE and PC-MRI was 0.5 mm (95% CI: -1.9, 2.9). Bland-Altman analysis also determined general agreement between both MRI methods and TEE. The ASDs were egg-shaped in two cases, circular in 1 patient and oval in the remaining patients. ASD sizing by MRI using bFFE and phase-contrast protocols correlated well with TEE estimations. PC-MRI provided additional information on ASD shapes and proximity to adjacent structures.

Catheter Visualization with Resonant Markers at MR Imaging–guided Deployment of Endovascular Stents in Swine

To evaluate resonant circuits as markers for magnetic resonance (MR) imaging-guided placement of nitinol stents. The study was approved by the institutional animal research committee and complied with National Institutes of Health guidelines for care and use of laboratory animals. Resonant circuits similar to catheter markers used at conventional angiography were placed proximally and distally to a nitinol stent in a stent delivery system. Resonant circuits were tested in vitro and in vivo for signal intensity levels that would enable visualization during MR imaging-guided stent deployment. Experiments were conducted by using real-time imaging with a 1.5-T unit. Stents (n = 9) were deployed in the vena cava (n = 2), abdominal aorta (n = 2), isthmus of the aorta (n = 2), and carotid (n = 2) and iliac (n = 1) arteries in five pigs. After intervention, the site of the stent was investigated with balanced fast field-echo MR imaging and contrast material-enhanced MR angiography. Blood flow velocities were measured in the stent lumen and next to the stent with velocity-encoded cine MR imaging. Level of agreement was determined with Bland-Altman analysis. During all interventions, resonant circuits provided highly visible MR signal that allowed fast and reliable visualization of the stent delivery system. Borders of loaded stents were clearly marked, which allowed precise stent placement in all experiments. Balanced fast field-echo MR imaging and contrast-enhanced MR angiography provided information about immediate postintervention position. Positions depicted on MR images were found accurate at postmortem examination. Results of Bland-Altman analysis showed good agreement between blood flow velocities measured in and next to the stent lumen, with a mean difference of -9 cm/sec +/- 5 (standard deviation). Resonant circuits are well suited for use at deployment of endovascular stents.

Cervical spondylosis: contrast-enhanced magnetization transfer prepulsed 3D turbo field echo MR imaging.

Magnetic resonance (MR) imaging of the cervical spine with axial, low flip angle three-dimensional (3D) gradient-echo sequences is limited by long acquisition times and also by increased sensitivity to extrinsic and intrinsic magnetic field inhomogeneity, magnetic susceptibility differences, chemical shifts, and cerebrospinal fluid pulsatility. We attempted to assess the performance of gadolinium-enhanced, magnetization transfer (MT) prepulsed 3D fast gradient-echo sequences in demonstrating spondylotic changes of the cervical spine. Twenty patients with known cervical spine spondylosis were prospectively imaged in the axial plane using two gradient-echo-based MR techniques: 3D fast field echo (FFE) and gadolinium-enhanced, MT prepulsed, segmented turbo field echo (TFE). An average of 58 neural foramina on the 3D FFE images and 47 neural foramina on the contrast-enhanced TFE images were judged to be narrowed. The degree of neural foraminal narrowing was significantly less on the contrast-enhanced TFE images compared with the FFE images (P <0.001). Contrast-enhanced, MT prepulsed, segmented 3D TFE MR imaging has potential for ameliorating some of the limitations encountered in the more widely used gradient-echo techniques.

Focal hepatic lesions: Detection by dynamic and delayed computed tomography versus short TE/TR spin echo and fast field echo magnetic resonance imaging

Eighteen patients with focal hepatic lesions were evaluated with two computed tomographic (CT) techniques including dynamic sequential bolus contrast CT and delayed contrast CT, and 3 magnetic resonance (MR) techniques including a spin echo pulse sequence with TE/TR of 21/310 msec and 2 fast field echo sequences using a TE/TR of 15/300 msec and 80 degrees flip angle (T1-weighted) and TE/TR of 15/500 msec and 10-20 degrees flip angle (T2-weighted). We concluded that CT, using delayed contrast and dynamic sequential bolus contrast techniques, was consistently superior to the 3 MR pulse sequences used on our imagers in terms of number of lesions detected, lesion-to-liver contrast, and quality of scan.

The effects of finite sampling in spin-echo or field-echo magnetic resonance imaging.

The artifacts associated with finite sampling in magnetic resonance imaging are shown to be significant when the ratio of half the sampling time, Ts/2, to transverse relaxation time, T2, is on the order of unity or greater. For both symmetric and asymmetric sampling, these artifacts include enhanced high spatial frequency image intensity (bright edges), induced systematic noise, loss of resolution, and changes in phase. Simple filtering of the raw data does not remove the problem in tissues with position-dependent T2 values. An exact deconvolution method is described to remove these problems associated with finite position-dependent T2 values.