MR imaging of the spine: recent advances in pulse sequences and special techniques

Role of magnetic resonance imaging in acute spinal trauma: a pictorial review

Magnetic resonance imaging (MRI) has been playing an increasingly important role in the spinal trauma patients due to high sensitivity for detection of acute soft tissue and cord injuries. More and more patients are undergoing MRI for spinal trauma in the emergency settings, thus necessitating the interpreting physicians to be familiar with MRI findings in spinal trauma. In this pictorial review, we will first describe the normal anatomy of various ligamentous structures. Indications of MRI in spinal trauma as well as the role of MRI in diagnosing spinal cord and soft tissue injuries will then be discussed. Illustrated cases are mainly of cervical spine trauma, but thoracolumbar spine injuries are also included where appropriate in our review.

Free-Breathing Radial 3D Fat-Suppressed T1-Weighted Gradient-Echo Sequence for Contrast-Enhanced Pediatric Spinal Imaging: Comparison With T1-Weighted Turbo Spin-Echo Sequence

OBJECTIVE

The purpose of this study was to compare free-breathing radially sampled 3D T1-weighted gradient-echo acquisitions (radial volumetric interpolated breath-hold examination [VIBE]) with a T1-weighted turbo spin-echo (TSE) sequence for contrast-enhanced spinal imaging of children with CNS tumors.

MATERIALS AND METHODS

Twenty-eight consecutively registered children with CNS tumors underwent evaluation of leptomeningeal seeding with 1.5-T MRI that included both radial VIBE and T1-weighted TSE sequences. For qualitative analysis, overall image quality; presence of motion, CSF flow, and radial artifacts; and lesion conspicuity were retrospectively assessed with scoring systems. The signal-intensity uniformity of each sequence was evaluated for quantitative comparison. The acquisition times for each sequence were compared.

RESULTS

Images obtained with the radial VIBE sequence had a higher overall image quality score than did T1-weighted TSE images (3.61 ± 0.73 vs 2.80 ± 0.69, p < 0.001) and lower motion artifact (0.82 ± 0.43 vs 1.29 ± 0.56, p = 0.001) and CSF flow artifact (0 vs 1.68 ± 0.67, p < 0.001) scores. Radial artifacts were found only on radial VIBE images (1.36 ± 0.31 vs 0, p < 0.001). In 13 patients with spinal seeding nodules, radial VIBE images showed greater lesion conspicuity than did T1-weighted TSE images (4.23 ± 0.52 vs 2.47 ± 0.57, p = 0.005). Radial VIBE images had diminished signal-intensity variation compared with T1-weighted TSE images in air, spine, and muscle (p < 0.01). The mean acquisition times were not significantly different between the two sequences (p = 0.117).

CONCLUSION

For pediatric spinal imaging, radial VIBE images had better image quality and lesion conspicuity and fewer CSF and respiratory motion artifacts than did T1-weighted TSE images in a similar acquisition time.

Characteristics of spondylotic myelopathy on 3D driven-equilibrium fast spin echo and 2D fast spin echo magnetic resonance imaging: a retrospective cross-sectional study

In patients with spinal stenosis, magnetic resonance imaging of the cervical spine can be improved by using 3D driven-equilibrium fast spin echo sequences to provide a high-resolution assessment of osseous and ligamentous structures. However, it is not yet clear whether 3D driven-equilibrium fast spin echo sequences adequately evaluate the spinal cord itself. As a result, they are generally supplemented by additional 2D fast spin echo sequences, adding time to the examination and potential discomfort to the patient. Here we investigate the hypothesis that in patients with spinal stenosis and spondylotic myelopathy, 3D driven-equilibrium fast spin echo sequences can characterize cord lesions equally well as 2D fast spin echo sequences. We performed a retrospective analysis of 30 adult patients with spondylotic myelopathy who had been examined with both 3D driven-equilibrium fast spin echo sequences and 2D fast spin echo sequences at the same scanning session. The two sequences were inspected separately for each patient, and visible cord lesions were manually traced. We found no significant differences between 3D driven-equilibrium fast spin echo and 2D fast spin echo sequences in the mean number, mean area, or mean transverse dimensions of spondylotic cord lesions. Nevertheless, the mean contrast-to-noise ratio of cord lesions was decreased on 3D driven-equilibrium fast spin echo sequences compared to 2D fast spin echo sequences. These findings suggest that 3D driven-equilibrium fast spin echo sequences do not need supplemental 2D fast spin echo sequences for the diagnosis of spondylotic myelopathy, but they may be less well suited for quantitative signal measurements in the spinal cord.

MR imaging of acute cervical spinal ligamentous and soft tissue trauma

The increasing availability of magnetic resonance imaging (MRI) and the high sensitivity of MRI for soft tissue injury are resulting in the increased use of MRI for the evaluation of acute trauma. As cervical spine injury can have a devastating consequence, MRI is being more commonly used to evaluate cervical spine injury in the acute setting, necessitating emergent interpretation by the on-call radiologist. Unless one is formally trained in a trauma center, the MRI findings of soft tissue and ligamentous cervical spine injury may not be fully appreciated. The goal of this pictorial review is to familiarize the reader with some of the more common soft tissue, vascular, and ligamentous injuries seen on MRI of the cervical spine in the emergent setting.

Three-dimensional isotropic T2-weighted cervical MRI at 3T: comparison with two-dimensional T2-weighted sequences

AIM

To compare three-dimensional (3D) isotropic T2-weighted magnetic resonance imaging (MRI) sequences and reformation with two-dimensional (2D) T2-weighted sequences regarding image quality of the cervical spine at 3T.

MATERIALS AND METHODS

A phantom study was performed using a water-filled cylinder. The signal-to-noise and image homogeneity were evaluated. Fourteen (n=14) volunteers were examined at 3T using 3D isotropic T2-weighted sagittal and conventional 2D T2-weighted sagittal, axial, and oblique sagittal MRI. Multiplanar reformation (MPR) of the 3D T2-weighted sagittal dataset was performed simultaneously with image evaluation. In addition to artefact assessment, the visibility of anatomical structures in the 3D and 2D sequences was qualitatively assessed by two radiologists independently. Cohen's kappa and Wilcoxon signed rank test were used for the statistical analysis.

RESULT

The 3D isotropic T2-weighted sequence resulted in the highest signal-to-noise ratio (SNR) and lowest non-uniformity (NU) among the sequences in the phantom study. Quantitative evaluation revealed lower NU values of the cerebrospinal fluid (CSF) and muscles in 2D T2-weighted sagittal sequences compared to the 3D volume isotropic turbo spin-echo acquisition (VISTA) sequence. The other NU values revealed no statistically significant difference between the 2D turbo spin-echo (TSE) and 3D VISTA sequences (0.059<p<0.959). 3D VISTA images showed significantly fewer CSF flow artefacts (p<0.001) and better delineated intradural nerve rootlets (p=0.001) and neural foramina (p=0.016) compared to 2D sequences.

CONCLUSION

A 3D T2 weighted sequence is superior to conventional 2D sequences for the delineation of intradural nerve rootlets and neural foramina and is less affected by CSF flow artefacts.

Diagnostic abilities of magnetic resonance imaging in traumatic injury to the posterior ligamentous complex: the effect of years in training

BACKGROUND CONTEXT

The integrity of the posterior ligamentous complex (PLC) has been proposed to be an integral aspect in the treatment algorithm for spinal trauma. Magnetic resonance imaging (MRI) has been reported as the ideal tool to determine the integrity of the PLC. The ability to assess disruption of the PLC by reviewers of differing levels of training has not been described. In addition, the MRI sequence most suggestive of injury for each component of the PLC has not been clearly determined.

PURPOSE

This study was designed to determine the ability of reviewers with differing levels of training (fellowship-trained spine surgeon, fellowship-trained musculoskeletal radiologist, senior orthopedic surgery resident, and junior orthopedic surgery resident) to accurately interpret the results of MRI. The secondary purpose was to evaluate the MRI sequence that was most indicative of injury to the components of the PLC.

STUDY DESIGN

This is a prospective radiological study comparing reviewers of MRI to determine integrity of the PLC components using intraoperative notation as the gold standard for integrity.

PATIENT SAMPLE

Forty-five consecutive spinal trauma patients who underwent operative fixation after obtaining MRI.

OUTCOME MEASURES

No patient outcome measures were used.

METHODS

The sensitivity, specificity, and accuracy for each MRI reviewer in regard to MRI integrity were compared with the gold standard of intraoperative observation. In addition, the MRI sequence most suggestive of integrity of the PLC was noted by each reviewer for each component of the PLC.

RESULTS

Forty-five patients (29 men and 16 women) with traumatic spine injuries were enrolled in the study. The sensitivity and accuracy of the surgeon were 0.83 (0.66, 0.92) and 0.81 (0.70, 0.88), respectively. The sensitivity and accuracy of the attending spine surgeon were not statistically significantly different from the other reviewers (p value=.2317 and .2582). However, the specificity of the surgeon was statistically significantly higher than that of the other reviewers (p=.0043). In the cervical, thoracic, and lumbar spine, the reviewers reached a 93% agreement that the sagittal short-tau inversion recovery (STIR) sequences were most helpful in visualizing injury to the supraspinous ligament (SSL), interspinous ligament (ISL), ligamentum flavum (LF), and the cervical facet capsules. The reviewers attained a 95% agreement that visualization of injury to the lumbar facet capsules is most optimal in the T2 axial sequences.

CONCLUSIONS

The interpretation of traumatic MRI is very sensitive and accurate regardless of years of training of the observer. The attending-level spine surgeon was statistically more specific in the evaluation of injury MRIs. The fluid-weighted STIR sagittal sequences are most useful in determining injury to the SSL, ISL, LF, and cervical facets capsules. Lumbar facet capsules are best evaluated with axial T2 MRI. The evaluation of the PLC on MRI can be accurately and efficiently interpreted by physicians at multiple levels of training, thus providing a key imaging modality in determining stability and need for stabilization.

Using magnetic resonance imaging to accurately assess injury to the posterior ligamentous complex of the spine: a prospective comparison of the surgeon and radiologist

Object

Magnetic resonance imaging has been proposed as a powerful technique for assessing the integrity of the posterior ligamentous complex (PLC) in spinal trauma. Because MR imaging is often used to determine appropriate treatment, it is important to determine the accuracy and reliability of MR imaging in diagnosing PLC disruption. The purpose of this study is to compare the ability of the radiologist and surgeon to assess disruption of the PLC in the setting of acute cervical and thoracolumbar trauma using MR imaging.

Methods

The components of the PLC in 89 consecutive patients with cervical or thoracolumbar fractures following acute spinal trauma were evaluated using MR imaging by both a musculoskeletal radiologist and an independent spine surgeon and assessed intraoperatively under direct visualization by the treating surgeon. The MR imaging interpretations of the musculoskeletal radiologist and surgeon were compared with the intraoperative report for accuracy, sensitivity, specificity, and positive and negative predictive values. A comparison between the radiologist's and spine surgeon's accuracy of MR imaging interpretation was performed.

Results

The agreement between both the spine surgeon's and radiologist's MR imaging interpretation and the actual intraoperative findings was moderate for most components of the PLC. Overall, the MR imaging interpretation of the surgeon was more accurate than that of the radiologist. The interpretation of MR imaging by the surgeon had negative predictive value and sensitivity of up to 100%. However, the specificity of MR imaging for both the surgeon and radiologist was lower, ranging from 51.5 to 80.5%.

Conclusions

Comparison of the MR imaging interpretations between surgeon and radiologist indicates that the surgeon was more accurate for some PLC components. The relatively low positive predictive value and specificity for MR imaging in assessing PLC integrity suggests that both the surgeon and radiologist tend to overdiagnose PLC injury using MR imaging. This can lead to unnecessary surgeries if only MR imaging is used for treatment decision making.

Magnetic resonance imaging of the cervical spine: comparison of 2D T2-weighted turbo spin echo, 2D T2*weighted gradient-recalled echo and 3D T2-weighted variable flip-angle turbo spin echo sequences

To compare an isotropic three-dimensional (3D) high-resolution T2-weighted (w) MR sequence and its reformations with conventional sequences for imaging of the cervical spine. Fifteen volunteers were examined at 1.5 T using sagittal and axial 3D T2-w, sagittal and axial 2D T2w, and axial 2D T2*w MR sequences. Axial reformations of the sagittal 3D dataset were generated (3D MPR T2w). Signal-to-noise and image homogeneity were evaluated in a phantom and in vivo. Visibility of ten anatomical structures of the cervical spine was evaluated. Artifacts were assessed. For statistical analysis, Cohen's kappa, Wilcoxon matched pairs, and t-testing were utilized. There were no significant differences in homogeneity between the sequences. Sagittal 3D T2w enabled better delineation of nerve roots, neural foramina, and intraforaminal structures compared to sagittal 2D T2w. Axial 3D T2w and axial 3D MPR T2w resulted in superior visibility of most anatomical structures compared to axial 2D T2w and comparable results to 2D T2*w concerning the spinal cord, nerve roots, intraforaminal structures, and fat. Artifacts were most pronounced in axial 2D T2w and axial 3D T2w. Acquisition of a 3D T2w data set is feasible in the cervical spine with superior delineation of anatomical structures compared to 2D sequences.

[Fundamental study of turbo spin echo sequence with driven equilibrium pulse]

When MR images are obtained with the turbo spin echo (TSE) sequence, DRIVE can be used as a sequence in which the driven equilibrium pulse (DE pulse), a reset pulse, is applied at the TSE echo train to accelerate relaxation time and return to the equilibrium of Mz magnetization. In this study, we examined the extent to which TR could be shortened in DRIVE and how the other parameters of the turbo spin echo sequence influence it.

RESULTS

1) DRIVE is effective when the T2 value is long. 2) It is necessary to set TR at 1000 ms or more to obtain image contrast with free water and fat in T2-weighted images for which a conventional turbo spin echo sequence using DRIVE is employed in clinical examination. 3) It is not necessary to consider the influence of the TSE factor when using DRIVE.

AreT1weighted images helpful in MRI of cervical radiculopathy?

MRI in patients with cervical myelopathy or radiculopathy usually includes T(1) weighted (T(1)W) and T(2) weighted (T(2)W) images. We prospectively examined a hypothesis that T(2)W alone is sufficient to diagnose the cause of cervical myelopathy and radiculopathy and that the T(1)W sagittal images do not provide additional useful information. 30 patients presenting with a history of cervical radiculopathy with or without myelopathy were prospectively assessed by MRI. Those with a history suggestive of intrinsic primary cord disease or who had previously had surgery were excluded. Two neuroradiologists, blinded to the clinical information, separately viewed the sagittal and axial T(2)W images alone, and at a later time, the full set of T(1)W and T(2)W images. Image quality, location and severity of disease and confidence of diagnosis at each level were scored on 4- or 5-point scales. The T(1) sequences did not demonstrate any significant lesions not already seen on the T(2)W images alone. The T(1)W sequence may safely be omitted in patients with radiculopathy.

Myelographic MR imaging of the cervical spine with a 3D true fast imaging with steady-state precession technique: initial experience

The majority of spinal magnetic resonance (MR) imaging has been performed with spin-echo sequences and spoiled gradient-echo sequences. Advances in gradient MR imaging performance now permit imaging with coherent steady-state sequences. In this study, the authors compare a three-dimensional true fast imaging with steady-state precession sequence with a three-dimensional spoiled gradient-recalled-echo sequence for MR evaluation of the cervical spine in the transverse plane. Initial experience indicates that the steady-state sequence is superior to spoiled gradient-recalled-echo sequences for MR evaluation of cervical spine anatomy and abnormalities.

Magnetic resonance imaging of sports injuries of the spine

Spinal injuries are relatively frequent events in professional athletes. Greater popularity of recreational athletic activities has increased the occurrence of sports-related spinal injuries in the general population. The demand of high-intensity sports places a constant load on the vertebral column. Several studies have demonstrated higher prevalence of spinal abnormalities in athletes than nonathletes. Direct correlation of the number and extent of injuries with the length in years of sports activity has been established. Diagnostic imaging, particularly magnetic resonance imaging (MRI), plays a crucial role in evaluating and detecting sports-related spinal injuries. Subtle bone marrow, soft-tissue, and spinal cord abnormalities, which may not be apparent on other imaging modalities, can be readily detected on MRI. Early detection often leads to prompt accurate diagnosis and expeditious management, in many cases avoiding unnecessary procedures. This article reviews the technical aspects of MRI for evaluation of the spine and the role of MRI in the assessment of sports-related spinal injuries.

Feasibility of ultrasound examination in posterior ligament complex injury of thoracolumbar spine fracture

STUDY DESIGN

A prospective study of 12 patients with thoracolumbar spinal fractures was conducted.

OBJECTIVE

To assess the feasibility of ultrasound examination for posterior ligament complex injury in thoracolumbar spinal fractures.

SUMMARY OF BACKGROUND DATA

In posterior ligament complex injury of thoracolumbar spine fracture, the reliability of magnetic resonance imaging (MRI) for diagnosis has been reported. Nevertheless the usefulness of ultrasound for diagnosis has not been studied, whereas diagnostic ultrasound has been applied in the musculoskeletal system.

METHODS

Two healthy volunteers without a history of spinal trauma were recruited for pilot examination of the ultrasound procedure to access normal findings of the posterior ligament complex. This study investigated 12 thoracolumbar spine fractures. Four were flexion distraction injury; six were stable or unstable burst fractures; and two were simple compression fractures. Osteoporotic spine fractures were excluded from this study. Ultrasound was performed over the injured area by an experienced musculoskeletal radiologist in addition to radiography and MRI. Five patients underwent operative procedures to stabilize the fractured spine. Imaging data and operative findings were correlated with ultrasound examination.

RESULTS

In the patients who did not undergo surgery, agreement in diagnosis between MRI and ultrasound was moderate (5 of 7). Difficulty evaluating ligament status was encountered when the region of interest was the lower thoracic level (T10, T11, T12) because of long overlapping spinous processes. In the patients who underwent surgery, correlation between MRI, ultrasound, and operative findings was excellent, especially in diagnosing the status of the supraspinous and interspinous ligaments. Nevertheless, it is impossible to visualize deep-seated structures (i.e., ligamentum flavum, deep muscles of the spine, and facet joint) with ultrasound.

CONCLUSIONS

This study demonstrated the excellent diagnostic ability of ultrasound to detect the status of the supraspinous and interspinous ligaments, especially in patients who undergo surgery. Although ultrasound examination appears to be less sensitive than MRI in predicting ligament status, the cost effectiveness of ultrasound and its use as an alternative to MRI in special situations (i.e., patients with pacemaker, ferromagnetic implant, or severe claustrophobia) should be emphasized. More clinical data concerning the sensitivity, specificity, and accuracy of ultrasound examination should be addressed in future studies.

In vivo 1H magnetic resonance imaging and spectroscopy of the rat spinal cord using an inductively-coupled chronically implanted RF coil

An inductively coupled, chronically implanted short-solenoid coil was used to obtain in vivo localized 1H NMR spectra and diffusion-weighted images from a rat spinal cord. A 5 x 8 mm two-turn elliptically shaped solenoid coil was implanted in rats at the site of a T-12 vertebral-level laminectomy. Excitation was achieved solely by a 3 x 3 cm external surface coil, and signal detection was achieved by inductively coupling the external coil to the implanted coil. The image signal-to-noise ratio (SNR) obtained with the inductively-coupled implanted coil was compared with that obtained using a linear or a quadrature external surface coil. The implanted coil provided a gain by over a factor of 3 in SNR. The implanted coil was used to measure localized 1H spectra in vivo at the T13/L1 spinal-cord level within a 1.85 x 1.85 x 4.82 mm (16.5 microL) volume. With 256 averages, a approximately 3-s repetition delay and respiratory gating, a high-quality spectrum was acquired in 13 min. In addition, water translational diffusion was measured in three orthogonal directions using a stimulated-echo imaging sequence, with a short echo time (TE), to produce a quantitative map of diffusion in a rat spinal cord in vivo.

Spinal fractures and pseudoarthrosis complicating ankylosing spondylitis: MRI manifestation and clinical significance

PURPOSE

To analyze magnetic resonance (MR) patterns of fractures and pseudoarthrosis of the ankylosing spondylitic spine, and related changes in the dura and adjacent soft tissue.

MATERIALS AND METHODS

Sixteen patients with radiographically evident fractures or pseudoarthrosis of the spine were included. Each underwent MR studies. Ten patients among them underwent surgical operations.

RESULTS

Both transdiscal (n = 12) and transvertebral (n = 4) fractures were identified. The levels were located from T9 to L3. Five of 16 patients had pseudoarthrosis. The fractures or pseudoarthrosis had two patterns: low signal on T1-and high signal on T2-weighted images, and low signal on both T1-and T2-weighted images. Disruption of anterior longitudinal ligament (ALL) was identified in 14 patients. Seven patients had vertebral translation, all had disruption of the ALL. Dural adhesions were noted in five patients and manifested as linear epidural enhancements with triangular blunt edges.

CONCLUSION

MR patterns of ankylosing spondylitis are important in evaluating complications of fractures or pseudoarthrosis, as well as changes in dura, soft tissue, and ligaments.

Clinical applications of FLAIR, HASTE, and magnetization transfer in neuroimaging

We review the clinical utility of three commonly used and relatively new magnetic resonance techniques as it pertains to neuroimaging. These techniques include fluid-attenuated inversion-recovery (FLAIR) images, half-Fourier acquisition single-shot turbo spin echo (HASTE) images, and magnetization transfer (MT). These techniques may be used to improve image quality and, in some cases, increase the sensitivity and the specificity of magnetic resonance imaging of the brain and spine.

Neoplasms of the spinal cord and filum terminale: radiologic-pathologic correlation

Intramedullary spinal cord neoplasms are rare, accounting for about 4%10% of all central nervous system tumors. Despite their rarity, these lesions are important to the radiologist because magnetic resonance (MR) imaging is the preoperative study of choice to narrow the differential diagnosis and guide surgical resection. On contrast materialenhanced MR images, intramedullary spinal tumors almost always manifest as expansion of the spinal cord and show enhancement. Syringohydromyelia and cystic lesions are frequently associated with intramedullary tumors. Nontumoral cysts tend to be located at the poles of the tumors and do not enhance on contrast-enhanced MR images, whereas cysts within the substance of the tumor are considered tumoral cysts and typically demonstrate peripheral enhancement. Spinal cord ependymomas are the most common type in adults, and cord astrocytomas are most common in children. Both entities constitute up to 70% of all intramedullary neoplasms. A central location within the spinal cord, presence of a cleavage plane, and intense homogeneous enhancement are imaging features that favor an ependymoma. Intramedullary astrocytomas are usually eccentrically located within the cord, are ill defined, and have patchy enhancement after intravenous contrast material administration. Even with these characteristics, it may not be possible to differentiate these two entities on the basis of imaging features alone. Cord hemangioblastomas are the third most common type of intramedullary spinal tumor. Gangliogliomas commonly extend over more than eight vertebral segments. Paragangliomas and primitive neuroectodermal tumors have an affinity for the filum terminale and cauda equina. Other spinal cord tumors include metastatic disease, which is characterized by prominent cord edema for the size of the enhancing portion, and primary lymphoma.

Reliability of magnetic resonance imaging in detecting posterior ligament complex injury in thoracolumbar spinal fractures

STUDY DESIGN

Prospective study of 34 patients with thoracolumbar spinal fractures.

OBJECTIVES

To assess the reliability of magnetic resonance imaging (MRI) for posterior ligament complex injury in thoracolumbar spinal fractures.

SUMMARY OF BACKGROUND DATA

Some researchers have studied posterior ligament complex injury in spinal fracture using MRI. However, most did not evaluate the findings of MRI compared with the operative findings.

METHODS

Thirty-four patients with thoracolumbar spinal fracture were evaluated by palpation of the interspinous gap, plain radiography, and MRI before operation. In addition to conventional MRI sequences, a fat-suppressed T2-weighted sagittal sequence was performed. Surgery was performed by a posterior approach. During the operation, posterior ligament complex injury was carefully examined.

RESULTS

A wide interspinous gap was palpated in 14 patients and was found in 21 patients on plain radiography. Magnetic resonance imaging raised suspicion of injury to the posterior ligament complex in 30 patients. According to interpretation of MRI, injury to the supraspinous ligament was suspected in 27 patients, the interspinous ligament in 30 patients, and the ligamentum flavum in 9 patients. There were 28 supraspinous ligament injuries, 29 interspinous ligament injuries, and 7 ligamentum flavum injuries in operative findings. There was a significant relation between MRI interpretation and operative findings.

CONCLUSION

A fat-suppressed T2-weighted sagittal sequence of MRI was a highly sensitive, specific, and accurate method of evaluating posterior ligament complex injury. Based on the results of this study, a fat-suppressed T2-weighted sagittal sequence of MRIs is recommended for the accurate evaluation of posterior ligament complex injury and would be helpful in the selection of treatment options.

Comparison of fast spin-echo and conventional spin-echo magnetic resonance spinal imaging techniques in four normal dogs

Various magnetic resonance (MR) imaging techniques have been used to assess lumbar spinal abnormalities in people. Four, young adult, clinically normal dogs were used to compare images of the spinal cord acquired using conventional spin-echo and rapid acquisition relaxation-enhanced (RARE), commonly called fast spin-echo (FSE), magnetic resonance imaging techniques. Lateral myelograms were made as an anatomic control. The T2-weighted FSE technique was characterized by better image quality than the T2-weighted conventional spin-echo technique. The short acquisition time with the FSE technique allowed increases in the matrix size and number of excitations, thus improving resolution and signal-to-noise ratio. In canine lumbar spinal MR imaging, use of a FSE technique is recommended to reduce the overall time for imaging and to improve image quality.

Use of magnetic resonance imaging in spinal trauma: indications, techniques, and utility

Magnetic resonance (MR) imaging of acute spinal injury provides excellent visualization of neurologic and soft-tissue structures in a noninvasive format. Advances in imaging-sequence techniques have made possible more rapid acquisition of images with greater spatial resolution. Appropriate selection of imaging sequences allows improved imaging and contrast of the pathologic processes involved in acute spinal trauma, including spinal cord, soft-tissue, and ligamentous injury. Three patterns of spinal cord injury have been identified. Type I is representative of acute cord hemorrhage. Type II represents spinal cord edema. Type III is a mixed hemorrhagic-edematous presentation. Correlation of MR findings with experimental and clinical spinal cord injury has given a relative predictive value to spinal cord injury patterns on MR images indicative of long-term neurologic outcome. Magnetic resonance imaging is useful in delineating soft-tissue injuries associated with spinal column trauma. Despite the improved spatial resolution of MR imaging, plain radiography and computed tomography remain the standard modalities for visualizing spinal fractures.

Ossification of posterior longitudinal ligaments: evaluation with MRI

Ossification of the posterior longitudinal ligament is a special subcategory of degenerative disease responsible for compression of the spinal cord. On MR images, T2-weighted sequences are the most effective to evaluate both spinal cord compression due to the ossification and abnormal signal intensity of the cord. Although ossification of the ligaments is well demonstrated on CT and plain radiographs, MRI noninvasively provides useful information about the degree and extent of spinal cord compression, as well as the character of the ossification.

The value of lumbar spine magnetic resonance imaging in the demonstration of anular tears

STUDY DESIGN

Retrospective review of magnetic resonance imaging and discography in patients investigated for low back pain before spinal fusion.

OBJECTIVE

To determine the sensitivity of magnetic resonance imaging in the detection of painful anular tears manifested by the high-intensity zone.

SUMMARY OF BACKGROUND DATA

Two studies have produced results showing that magnetic resonance imaging has a high specificity for the detection of painful anular tears manifested by a high-intensity zone. However, in a recent study, results showed no significant correlation between the high-intensity zone and pain reproduction. The sensitivity of magnetic resonance imaging in identifying anular tears in a symptomatic population has not been determined.

METHODS

Anular tears were identified in magnetic resonance images by the presence of a high-intensity zone in the posterior anulus. The results were compared with the demonstration of painful anular tears on discogram, which has been considered the gold standard.

RESULTS

The study group comprised 58 patients (31 men, 27 women; mean age 42, range 21-63 years). One hundred and fifty-two discs were injected and examined by discography, and 108 were considered degenerate. Of these, 86 had anular tears (54 posterior, 6 anterior, 26 both). Seventy anular tears were associated with concordant pain provocation. Twenty-seven high-intensity zones were identified in magnetic resonance imaging, of which 24 were associated with pain reproduction by discography. The sensitivity, specificity, positive predictive value, and negative predictive value of magnetic resonance imaging in the diagnosis of concordantly painful posterior anular tears are therefore 26.7%, 95.2%, 88.9%, and 47%, respectively.

CONCLUSION

These results confirm that the high-intensity zone is a marker of a painful posterior anular tear. However, the usefulness of this sign is limited by low sensitivity.

Magnetic resonance imaging of the musculoskeletal system. Part 8. The spine, section 1

Magnetic resonance has assumed a preeminent role in the imaging evaluation of the spine. Owing to its multiplanar capability and superior soft tissue contrast, magnetic resonance imaging is the procedure of choice for a host of spinal disorders including degenerative disc disease, tumor evaluation, trauma, and spinal deformities. It represents the most accurate means of distinguishing between recurrent disc herniation and epidural fibrosis, and it excels at the assessment of many postoperative abnormalities such as infection, adjacent segment disc degeneration, and arachnoiditis. Magnetic resonance imaging is also helpful in the evaluation of numerous diagnostic challenges that are less well resolved by other means. This includes the distinction between disc herniation and epidural hematoma, synovial cyst from nonspecific fibrous thickening of a facet capsule, and the evaluation of numerous other soft tissue abnormalities. Computed tomography, computed tomography myelography, and scintigraphy continue to be useful for numerous specific disorders and in those patients with metal hardware or contraindications to magnetic resonance scanning. Overall, however, magnetic resonance is the imaging procedure preferred for many spinal disorders. This article is the first installment of a 3-part series discussing the role of magnetic resonance imaging of spinal disorders. Section 1 will describe the varying imaging modalities available and their relative advantages and disadvantages. A consideration of magnetic resonance imaging techniques will follow, followed by a discussion of the imaging manifestations of early degenerative disc disease. Section 2 will be devoted to an in depth discussion of specific pathologic processes encountered in patients with degenerative disc disease. Section 3 will end the series with a consideration of postoperative imaging followed by a discussion of spinal deformities, trauma, and neoplasms.

Epidural spinal infection. Variability of clinical and magnetic resonance imaging findings

STUDY DESIGN

This study evaluates the magnetic resonance characteristics of spinal epidural abscesses and their associated disc space infections.

OBJECTIVES

The results were correlated with history, clinical, and laboratory findings to provide guidelines for early and appropriate diagnosis of epidural spinal infections.

SUMMARY OF BACKGROUND DATA

Imaging signs of spinal infections have been reported before, but not with special attention to early clinical and imaging findings.

METHODS

Thirteen patients (10 men, 3 women; age range, 32-64 years) with progressive sensorimotor deficit were studied. All patients had a neurologic examination after admission and a magnetic resonance imaging scan done within the first 48 hours. In all cases, T1-weighted images before and after administration of gadolinium were obtained. T2-weighted images were acquired in eight cases as well. Ten patients subsequently underwent open surgery; in three cases, a percutaneous biopsy and drainage was performed.

RESULTS

Cervical discitis was found in five patients, and thoracic discitis was seen in another five cases. Three patients had an epidural infection without a concomitant discitis. Neurologic and clinical findings varied considerably. Despite clinical signs of spinal cord involvement, a spinal cord lesion was demonstrated only once. Signal change in T2-weighted images may be the first sign of disc space infection. Because a neurologic deficit may occur before any change is visible, follow-up examinations may be required if epidural infection is suspected on clinical grounds.

CONCLUSIONS

Magnetic resonance imaging is the appropriate method for diagnostic work-up of progressive neurologic deficit resulting from epidural infection.

Evaluation of the temporal evolution of acute spinal cord injury

RATIONALE AND OBJECTIVES

After receiving a controlled injury to the thoracic cord, five rats were examined on a 1.5-T magnetic resonance (MR) imaging system at regular intervals over 1 month to assess evolution of the injury.

METHODS

After the rats received pentobarbital anesthesia, a T10 laminectomy was performed on them, which exposed the dura over the dorsal surface of the spinal cord. With the animal placed in a New York University weight-drop device, a 10-g rod with a flat brass tip was dropped (free-fall) from a height of 50 mm to impact the cord. After injury, the incision was closed with suture material. Each animal was imaged on the day of injury, and at 7, 14, and 28 days after injury. Before contrast injection was administered, sagittal sections were obtained with T2 fast-spin echo and T1-spin echo technique. Each rat then received 0.3-mmol/kg gadoteridol (Gd HP-DO3A or ProHance) intravenously, with the T1 scan repeated. At 28 days, the animals were killed, and the cord was fixed and embedded in paraffin for histologic evaluation.

RESULTS

The intensity of cord enhancement in the region of injury, after intravenous (i.v.) contrast injection, was at a maximum on the day of injury, and it decreased in a steady fashion thereafter. The intensity was 11.7 +/- 0.6 on the day of injury, 9.7 +/- 2.6 on day 7, 6.3 +/- 5.3 on day 14, and 0.0 +/- 2.3 on day 28. The results on day 0 and 7 were statistically significant in terms of a difference from that on day 28, with a P value < 0.001. The length of cord injury, assessed postcontrast, also decreased in a steady fashion from the day of injury. The length of injury (in cm) was 1.1 +/- 0.1 on the day of injury, 0.5 +/- 0.2 on day 7, 0.3 +/- 0.1 on day 14, and 0.1 +/- 0.1 on day 28. The results on day 0 and 14 were statistically significant in terms of a difference from those at the next time point, with P values from < 0.01 to < 0.001. Visually, on T2 images, substantial edema was noted on day 0, with progression to focal cord atrophy and gliosis by day 28.

CONCLUSIONS

Acute spinal cord injury in a rat model is well visualized on pre- and postcontrast MR scans at 1.5 T. Observation of T2 changes and disruption of the blood-spinal cord barrier provide markers for temporal assessment of spinal cord injury in the rat model.

Comparison between magnetization transfer contrast and fast spin-echo MR imaging of degenerative disease of the cervical spine at 0.3 T

We compared magnetization transfer contrast (MTC) with gradient recalled echo (GRE) magnetic resonance imaging (MRI) and fast spin-echo (FSE) MRI of the degenerative cervical spine at 0.3 T. Fifty patients with suspected degenerative disease of the cervical spine were prospectively evaluated. Multislice sagittal and axial images of the cervical spine were obtained using MTC GRE sequence [repetition time (TR)/echo time (TE)/flip angle = 750/23/25 degrees] and FSE sequence with peripheral gating (TR/effective TE = 2000-4000/120). Quantitatively, FSE showed higher signal-to-noise ratio and superior disk contrast between normal and degenerative disks, while MTC images showed superior contrast-to-noise ratio for the cerebrospinal fluid (CSF) versus cord and superior CSF homogeneity. In qualitative analysis, similar results were obtained. In conclusion, FSE and MTC GRE sequences are MRI techniques of imaging the cervical spine that have different characteristics and supplement each other in the diagnostic imaging of degenerative disease of the cervical spine.

Radiotherapeutic management of spinal metastases

Radiotherapy remains the primary treatment of malignant epidural spinal cord compression. Therapeutic success depends on diagnosis before the development of neurological compromise and the prompt initiation of radiotherapy. Radiotherapy alone is effective in over 85% of cases of spinal cord compression that occur in highly radioresponsive tumors (multiple myeloma, germ cell or lymphoproliferative tumors). In the more common tumors, like breast, prostate, and lung cancer, response to radiotherapy is based on presenting neurologic deficits, extent of disease, duration of symptoms, and overall clinical status, including other sites of metastatic involvement. Surgery is recommended in addition to radiotherapy in selected cases, and further study is needed to better define the prognostic and neurological parameters for the surgical management of spinal cord compression. Improvements in outcome in the treatment of spinal cord compression will require approaches like combined modality therapy because of the limitations primarily imposed by the radiation tolerance of the spinal cord.