Fast spin echo vs conventional spin echo in cervical spine imaging

The major attraction of fast-spin-echo (FSE) imaging is reduced acquisition time; however, careful review of the literature reveals many weaknesses: phase-encoded blurring, truncation artefact, bright fat signal, reduced magnetic susceptibility and increased motion artefact. Our aim was a prospective, blinded comparison of FSE and conventional spin echo (CSE) in the cervical spine. Both sequences were performed in 43 patients (19 males and 24 females; mean age 45 years, range 15-66 years). Twenty-eight patients were studied at 1.5 T and 15 at 0.5 T. Typical sequence parameters were: at 1.5 T, TR/TE 2000/90 CSE and 3000/120 FSE, and at 0.5 T, 2200/80 CSE and 2800/120 FSE. Time saved on the FSE was used to increase the matrix and the number of acquisitions. Two neuroradiologists evaluated the images for pathology, artefacts, disc signal intensity, thecal sac compression and image quality. Ten patients had cord lesions; 2 (20 %) were missed on CSE. In 4 of 10 patients with moderate/severe thecal sac compression, the degree of stenosis was apparently exaggerated on CSE. The mean degree of confidence for the CSE sequences was 1.8 and for the FSE 1.1, where 1 is optimal. For cervical spine imaging, FSE should be preferred to CSE.     

Intracranial black-blood MR angiography with high-resolution 3D fast spin echo

Three-dimensional fast spin-echo (3DFSE) techniques are promising for black-blood imaging of cerebral vessels. In this study, flow-related signal dephasing was demonstrated as the primary mechanism for blood signal attenuation. Parameter optimization of TR (1500 to 3000 ms), receiver bandwidth (25 to 31.25 kHz), effective TE (25.7 to 30.1 ms), and ETL (7 to 8) was accomplished by making measurements of vessel-to-tissue contrast-to-noise ratios on vessels. A comparison of high-resolution 3DFSE and 3DTOF magnetic resonance angiography demonstrated that 3DFSE can generate images with equivalent or better small vessel detail than conventional techniques. 3DFSE black-blood techniques may provide improved sensitivity of small arteries and veins with slow or in-plane flow and immunity to flow-related distortions. Future studies with optimized parameters will determine the clinical efficacy of this technique.     

Three-dimensional coronary MR angiography using zonal echo planar imaging

Using an adapted two-dimensional spatially selective RF excitation scheme, a novel yet practical three-dimensional (3D) zonal echo-planar imaging technique for MR coronary angiography has been developed. The robustness of the technique compared with the two-dimensional (2D) segmented fast low angle shot (FLASH) method was evaluated using the right coronary artery images of 16 asymptomatic volunteers with a 0.5-T mobile scanner. Each 3D acquisition required multiple breath-holds, and real-time navigator echoes were used to ensure consistent breath-holding. Advantages of the technique include an improved signal-to-noise ratio, clearer depiction of tortuous coronary vessels due to decreased partial volume effects, and reduced motion blurring by the use of a short echo-planar readout.     

Postoperative sella: evaluation with fast spin echo T2-weighted high-resolution imaging

OBJECTIVE: The purpose of this study was to investigate the magnetic resonance features of the postoperative sella with fast spin echo (FSE) T2-weighted high-resolution imaging and to evaluate the benefits of the sequence using a follow-up magnetic resonance imaging protocol after transsphenoidal surgery. METHODS: Coronal spin echo (SE) T1-weighted and FSE T2-weighted images were prospectively obtained in 24 patients after surgery for pituitary adenomas. We observed the signals and the contour of normal structures, fluid collection, implanted materials, and mass lesions, including granulation tissue and adenoma. RESULTS: The pituitary gland was delineated in 51 of 59 FSE T2-weighted images, 90.2% of which presented clear boundaries. Whereas the gland was detected in 49 of 58 SE T1-weighted images, only 20.4% showed the boundaries. A mass lesion was identified in each of 12 patients with good resolution on FSE T2-weighted images. SE T1-weighted images detected mass lesions in 7 of 12 patients without distinctive boundaries. Contrast enhancement had little advantage in clarifying the boundaries between normal and abnormal structures. For the detection of mass lesions in the sella, the kappa values for interobserver agreement were 0.8 for FSE T2-weighted images and 0.25 for SE T1-weighted images. CONCLUSION: FSE T2-weighted imaging is a reliable method with which to assess the sella with sufficient resolution after transsphenoidal surgery. The combination of unenhanced SE T1-weighted and FSE T2-weighted images may reduce the use of contrast material after pituitary surgery.     

Assessment of myocardial perfusion hemodynamics using echo planar MR imaging

It was possible to obtain images for individual heart beats using single-shot Echo Planar Imaging(EPI), and changes of myocardial signal intensity could be assessed visually after GD-DTPA administration. Measurement of the same site in the myocardium on myocardial perfusion images for individual heart beats was facilitated by imaging during breath-holding, and accurate evaluation was possible. In patients with coronary artery disease, the site of myocardial infarction tended to show less increase in signal intensity than the normal myocardium, and could easily be distinguished from normal myocardium according to the change in signal intensity. In patients with atrial fibrillation, the signal intensity of the myocardium varied with each heart beat, and it was difficult to assess perfusion hemodynamics. Myocardial perfusion studies using EPI still present problems with respect to spatial resolution, but the myocardial perfusion hemodynamics for individual heart beats can be determined by preparing time/intensity curves. It is also possible to obtain information on cardiac morphology, wall motion, and myocardial metabolism in addition to perfusion data by combining myocardial perfusion studies with methods such as high speed cine MRI, tagging, or myocardial MRS. It is possible that this method will also be useful in studying myocardial viability.     

Lumbar spine magnetic resonance imaging: comparison between fast spin echo proton density and spin echo T1 axial scans

Spin echo (SE) T1 axial scans are routinely obtained in magnetic resonance imaging of the lumbar spine in many centres. This study directly compared matched SE T1 and fast SE (FSE) proton density (PD) axial scans. Both SE T1 and FSE PD axial scans of the lumbar spine were obtained in 116 consecutive patients. The imaging parameters (field-of-view, slice thickness, interslice gap, number of excitations and matrix size) and scan levels were identical for each pair of sequences. At two selected levels, L4/5 and L5/S1, various structures were independently graded by two observers. In 232 lumbar levels analysed, the bone marrow, epidural fat, disc, extradural nerve root and facet joint were equally well seen on both sequences by both observers (combined mean grades of 2.93-2.99). The thecal sac was marginally better depicted on FSE PD than on SE T1 images, with mean grades of 2.96 and 2.88, respectively. The psoas muscle was adequately visualized for diagnostic purposes on both sequences (mean grades of 2.30-2.32). The cauda equina were better seen on FSE PD (mean grade 1.92) than on SE T1 (mean grade 1.00) images. In conclusion, FSE PD scans are comparable to and may potentially replace SE T1 axial MR scans of the lumbar spine.     

Fast gradient echo MR imaging of the liver enhanced with superparamagnetic iron oxide

Urinary proteins of patients with diabetes mellitus (DM) were analyzed using cellulose acetate membrane electrophoresis, to determine the clinical usefulness of fraction patterns of the proteins in detecting the group at high risk for diabetic nephropathy. We divided the protein patterns into 5 groups. Four groups (I, II, III, IV) were found in the healthy group and a newly classified group was termed group 0 and was characterized by a prominent albumin peak with a negligible or small globulin peak. The incidence of groups 0, I, II, III, and IV, was 36.6%, 13.3%, 18.7%, 10.7% and 22.7%, respectively. This distribution was clearly different from that of healthy subjects and the most characteristic feature of diabetics was that group 0 accounted for 36.6% of the total cases. Characteristic features of each group were examined from the aspect of laboratory and clinical findings. Urinary protein patterns were concluded to be useful not only to predict the high risk group for diabetic nephropathy in the preclinical stage but also to discriminate nephropathic types of glomerular or tubular origin. It is useful for clinicians to know the risk stage and prognosis for diabetic nephropathy.     

Breath hold MR cholangio-pancreatography (MRCP) using long echo train length fast spin echo sequence in combination with surface coil

To test the feasibility of MR cholangio-pancreatography (MRCP) using long echo train length (32) fast spin echo sequence in combination with shoulder surface coil, 20 patients who had had ERCP were examined. Good correlations were acquired between the findings obtained by two modalities in terms of ductal strictures, dilatations and intraductal lesions. MRCP was considered to be an examination of choice in various kinds of pathologies affecting biliary duct as well as pancreatic duct for its non-invasiveness and reasonable image quality.     

Cervical spine: three-dimensional MR imaging with magnetization transfer prepulsed turbo field echo techniques

In 11 volunteers, magnetic resonance (MR) imaging of the cervical spine was performed with a magnetization transfer preparatory pulse (prepulsed), three-dimensional Fourier transform, turbo field echo sequence. The effects of flip angle, number of shots, phase-encoding profile order, and magnetization transfer prepulse offset frequency on cerebrospinal fluid-to-cord contrast were evaluated. The contrast was improved by lowering the flip angle, increasing the number of shots, and implementing a magnetization transfer prepulse and linear phase-encoding profile order. Maximum myelographic effect was achieved with the magnetization prepulse (500-Hz frequency offset), 3 degrees flip angle, six shots, and linear phase-encoding profile order.     

FASE (fast advanced spin echo)

RF-refocused single or multi-shot EPI provides high-contrast 2D or 3D T2-weighted images in a very short scan time. Applications include MR cholangiopancreatography, MR myelography, imaging detailed structures of the internal auditory canal and in situations in which very fast T2 imaging is required. FASE offers both 2D and 3D techniques. 2D FASE technique permits high-resolution images of 384 matrix or more to be obtained at 2 to 3 seconds per image. It is easy to perform and suitable for screening. 3D FASE permits acquisition of isotropic voxels, allowing high-resolution viewing from any desired direction by post-processing (MIP and/or MPR). This technique is best suited to detailed examinations in which multiple projection angles will be reconstructed or high-resolution diagnosis of source images.     

Single shot fast spin echo (SSFSE)

Single Shot Scan methods, which acquire all the necessary data for reconstruction with one excitation, are very useful methods to minimize motion artifacts. Single Shot Scan can be categorized in 2 groups, one is EPI method using gradient by Echo data acquisition, and another is SSFSE method using RF. SSFSE method is Single Shot FSE method using 0.5 NEX. SSFSE produces images with less motion artifacts and heavy PD and T2 images with high contrast. New RF reduces Echo Space and minimizes image quality degradation caused by Single Shot. SSFSE is useful for long T2 like MRCP. Long TE mode can be used with very long ETE even with 0.5 NEX. New applications development for Single Shot using RF is awaited in the future.     

MR imaging

MRI is a tool of unprecedented capabilities for evaluating arthritis and its progression. Not only can it non-invasively delineate the anatomy of all components of a joint with unparalleled clarity, MRI is also capable of probing important functional and compositional parameters of disease in these tissues. Particularly intriguing is MRI's potential for identifying very early changes of joint disease when clinical symptoms may be minimal or absent. Early detection of patients who are at risk for developing progressive disease may allow appropriate treatment to be initiated earlier, when there may be a greater chance of favourable outcome. MRI can, furthermore, provide objective and quantitative measures of disease progression and treatment response. Certain parameters, such as articular cartilage volume, have been validated cross-sectionally; however, their longitudinal performance has yet to be established. Further work is, therefore, necessary to thoroughly validate and optimize some of these measures so that they can begin to be used in more powerful ways to explore the pathophysiology and potential therapies of arthritic disorders.     

MR imaging in patients with strabismus

The patients with strabismus, including 8 with superior oblique paresis, 1 with inferior rectus paresis, and 1 with congenital constant exotropia, were examined with MR imaging at 1.5 tesla (T) or 0.5T with a surface coil. Abnormal findings of extraocular muscles were identified in 8 of the 10 patients and most of them were consistent with the clinical findings. Deviation of the optic nerves was noted in 5 patients. Coronal short repetition time (RT) and echo time (ET) images were used to measure the concerned extraocular muscles and the optic nerves. The differences in diameters between the concerned extraocular muscles of both the diseased and normal eyes were calculated. MR imaging is considered to be advantageous and can be favorably used to observe and measure the extraocular muscles and other intraorbital structures in patients with strabismus.     

Diagnosis of bronchial rupture with MR imaging

Tracheobronchial rupture is a serious injury occurring in approximately 1.5% of cases of major chest trauma. This injury is associated with significant mortality and morbidity and may be difficult to recognize both clinically and radiologically. Radiologic signs are mostly nonspecific, with pneumothorax and pneumomediastinum being the most common. A high level of suspicion is required to make the diagnosis. Computed tomography (CT) can be helpful; however, it provides only indirect evidence for the diagnosis. This report describes a case of complete transection of the right main bronchus, suspected at plain radiography and CT and clearly shown on magnetic resonance (MR) images. MR imaging, with its multiplanar capabilities, can be helpful in defining the location and extent of injury and in diagnosing injury not suspected or clearly demonstrated with other imaging modalities.     

MR angiography with ultrashort echo time in cerebral aneurysms treated with Guglielmi detachable coils

We evaluated a time-of-flight three-dimensional MR angiographic sequence with an ultrashort echo time for its ability to characterize the perfusional state of cerebral aneurysms that had been treated with Guglielmi detachable coils and to depict adjacent cerebral arteries. The results were compared with findings at conventional MR angiography and digital subtraction angiography. Adjacent vessels were seen better in 36% of patients imaged with the new technique. Both MR angiographic methods detected residual cerebral aneurysmal perfusion with a tendency to overestimate the patent portion of the aneurysm.     

Brain functional MRI of the visual cortex with echo planar imaging

Brain functional MR imaging (fMRI) is a non invasive imaging method for detecting neural activity. We performed functional MRI of the visual cortex with gradient-echo echo planar imaging (GE-EPI) and spin-echo EPI (SE-EPI) using 1.5T MRI system. Visual stimuli was performed with a checkerboard patterns. Magnitude and temporal phase of correlation between each pixel's time-course and sine functions at the frequency of the stimulus was calculated. In all subjects, the activation area in visual cortex obtained from SE-EPI was smaller than that from GE-EPI. Temporal phase delay images from both GE-EPI and SE-EPI showed signal spread from the primary visual cortex to peripheral supplementary areas. Temporal phase analysis is important to discriminate the source of the hemodynamic response to neural activation in fMRI.     

MR imaging of symptomatic osteochondromas with pathological correlation

Presentation of antigenic peptides by major histocompatibility complex (MHC) class I molecules depends on translocation of cytosolic peptides into the endoplasmic reticulum (ER) by transporters associated with antigen processing (TAP). Peptide transport by TAP is thought to include at least two steps: initial binding of peptide to TAP, and its subsequent translocation requiring ATP hydrolysis. These events can be monitored in peptide binding and transport assays. Previous studies have shown that the efficiency of peptide transport by human, mouse and rat transporters varies according to the C-terminals of peptide substrates in an allele and species-specific manner. However, it has not been clear during which step of peptide interaction with TAP selection occurs. We used an assay monitoring the peptide binding step to study the binding affinity of a library of 199 peptides for human TAP and the two major allelic rat TAP complexes. We observed a dominant influence of the C-terminus on peptide binding affinity for all transporters, and highly restrictive selection of peptides with aliphatic and aromatic C-terminals by rat TAP1/TAP2u complexes. The selectivity of peptide binding to rat TAP complexes is in full accordance with published data on selective peptide transport and on control of antigen presentation by rat TAP. These results strongly suggest that (i) peptide selection by TAP occurs exclusively in the initial binding step; (ii) all factors involved in peptide selection by TAP are present in insect cells.