MR imaging of the lumbar spine: anatomic correlations and the effects of technical variations

Evaluation of the Level of Dural Sac Tip in Saudi Population: A Magnetic Resonance Imaging Study

Background For the success of procedures such as caudal block, craniospinal irradiation (CSI), and management of lower back pain and to minimize the risk of dural puncture the exact level of dural sac (DS) termination should be known. Objective The evaluation of DS tip location in the Saudi population and exploring possible significant factors that could be used as predictors in clinical prognosis. Methods A total of 200 patients' lumbar sagittal Weighted T2 Magnetic Resonance Imaging (MRI) study were randomly selected from a single-center hospital in-between 2020 and 2021. The DS tip location was determined by generating a perpendicular line from the longitudinal axis of its termination to the corresponding level. Then naming it after an intervertebral disk or a corresponding vertebrate that is divided into three thirds (upper, middle, and lower). Results In most cases, the level of DS termination is at the middle part of S2 (26.5%), followed by the upper part of S2 (25.1%), and the lower part of S2 (20%). In Saudi nationals, the DS tip was in the middle S2 level at 21.5%, upper S2 level at 19.1%, and lower S2 level at 17%. Factors such as age, sex, cause of referral, and nationality had no statistical significance in relation to DS tip location. Conclusion The DS termination level in the Saudi population ranges from disk between L5-S1 to the lower third of S3. Moreover, nationality, age, and cause of referral were not significant in determining the DS termination level. Therefore, it is still important to individualize patients' treatment by using MRI for each case that requires it.

Coil Selection for Magnetic Resonance Imaging of the Cervical and Thoracic Spine Using a Vertical Magnetic Field

In order to optimize the coil selection for cervical and thoracic spine imaging the signal characteristics of two different solenoidal surface coils (15 cm and 30 cm diameter, respectively) as well as the head coil and body coil were determined using a 0.3 T MR scanner with a vertical magnetic field. Signal-to-noise ratio curves were obtained for each coil using tube phantoms and a human-like phantom. The findings were compared with images obtained in two healthy volunteers. The head coil was found to be superior for imaging of the cranio-cervical junction while the 15 cm surface coil gave better results in the remaining part of the cervical spine and the upper thoracic spine. The body coil was superior for imaging of the thoracic region at the level of the shoulders (T4-T6) but the 30 cm surface coil was better for the more caudal part of the thoracic spine. Combined phantom and in vivo studies are also recommended for evaluation of future, improved coils.

Emergency Magnetic Resonance Examination of Patients with Spinal Cord Symptoms

Eighteen consecutive patients with spinal cord symptoms of sudden or relatively sudden onset were examined with magnetic resonance imaging (MRI). The examinations were performed on a 0.3 tesla permanent/resistive imaging system using solenoidal surface coils. MRI revealed epidural tumour in five patients, intramedullary tumour in one, epidural abscess in one, myelitis in two, spontaneous intraspinal epidural haematoma in two, disc herniation in two, traumatic lesions in four and no abnormality in one patient. MRI was found to be capable of non-invasively and painlessly detecting and exactly defining the extent of intraspinal and paraspinal lesions. In some cases the nature of the lesion could be inferred from specific signal characteristics, which is a unique property of MRI. The results strongly suggest that MRI is superior to myelography and other imaging methods and should be regarded as the examination of choice in the emergency examination of patients with spinal cord symptoms.

Discovertebral Junction of the Spine — A Cadaveric Study by Spin-Echo MR Imaging

To evaluate the MR appearance of the discovertebral junction (DVJ) of the spine, we examined 161 DVJs in 27 cadaveric spines using superconductive MR imaging. T1-, proton density-, and T2-weighted spin-echo imaging were used. With a small surface coil, higher resolution and more sharply defined contours of the DVJ were obtained than when using a head coil. Cortical bone had very low signal intensity in all sequences. Cartilaginous end-plate (CP) was of low to intermediate signal intensity on T1-weighted images, and of low signal intensity on proton density- and T2-weighted images. MR images were able to reveal the gross CP appearances, Schmorl's nodules, and adjacent bone marrow pathology. We conclude that MR imaging is valuable for assessing abnormalities of the DVJ.

Ultra Low Field Magnetic Resonance Imaging and Computed Tomography in the Diagnosis of Lumbar Disc Disease

Magnetic resonance (MR) examination of the lumbar spine was performed in 51 patients using a resistive magnet with a field strength of 0.02 T. The results at 105 intervertebral levels were compared with those of computed tomography (CT). Due to the extremely low field strength, an unfavourable signal-to-noise ratio degraded the image quality. Some improvement was achieved with the development of a dedicated surface coil. The diagnostic information was not comparable with that obtained with CT, nor was the image quality comparable to that obtained at higher field strengths. Compared with CT there was no false information. Therefore, it is suggested that extremely low field units may permit exclusion of pathology on the basis of a normal examination and in this way help in the selection of those patients who need further investigation and treatment.

Lumbar subcutaneous edema and degenerative spinal disease in patients with low back pain: a retrospective MRI study

PURPOSE

This study was designed to determine the association between LSE, spondylolisthesis, facet arthropathy, lumbar canal stenosis, BMI, radiculopathy and bone marrow edema at conventional lumbar spine MR imaging.

METHODS

This is a retrospective radiological study; 441 consecutive patients with low back pain (224 men and 217 women; mean age 57.3 years; mean BMI 26) underwent conventional lumbar MRI using a 1.5-T magnet (Avanto, Siemens). Lumbar MR images were reviewed by consensus for the presence of LSE, spondylolisthesis, facet arthropathy, lumbar canal stenosis, radiculopathy and bone marrow edema. Descriptive statistics and association studies were conducted using STATA software 11.0. Association studies have been performed using linear univariate regression analysis and multivariate regression analysis, considering LSE as response variable.

RESULTS

The overall prevalence of LSE was 40%; spondylolisthesis (p = 0.01), facet arthropathy (p < 0.001), BMI (p = 0.008) and lumbar canal stenosis (p < 0.001) were included in the multivariate regression model, whereas bone marrow edema, radiculopathy and age were not.

CONCLUSIONS

LSE is highly associated with spondylolisthesis, facet arthropathy and BMI, suggesting underestimation of its clinical impact as an integral component in chronic lumbar back pain. Longitudinal simultaneous X-ray/MRI studies should be conducted to test the relationship of LSE with lumbar spinal instability and low back pain.

Investigation of suspected Guillain-Barre syndrome in childhood: what is the role for gadolinium enhanced magnetic resonance imaging of the spine?

AIM

To review the role of gadolinium-enhanced magnetic resonance imaging of the spine in the diagnosis of paediatric Guillain-Barre syndrome and compare it with nerve conduction studies and cerebrospinal fluid analysis.

METHODS

A retrospective review of investigations undertaken in children admitted to our institution with acute Guillain-Barre syndrome over a 10-year period was performed.

RESULTS

Seven of eight children (88%) displayed post-gadolinium nerve root enhancement consistent with Guillain-Barre syndrome. This compared with supportive nerve conduction studies in 21/24 children (88%) and cerebrospinal fluid protein analysis consistent with the diagnosis in 16/20 children (80%).

CONCLUSION

Nerve conduction studies are the recognised 'gold standard' technique for confirming a clinical diagnosis of Guillain-Barre syndrome. In this study, a high positive rate was demonstrated. While more experience is necessary, this study and the literature support gadolinium enhanced magnetic resonance imaging of the spine as a valuable, although not necessarily superior, investigation in the diagnosis of Guillain-Barre syndrome. It may be of particular benefit when specialist neurophysiology expertise is unavailable.

Evaluation of intervertebral disk degeneration in chondrodystrophic and nonchondrodystrophic dogs by use of Pfirrmann grading of images obtained with low-field magnetic resonance imaging

OBJECTIVE

To assess whether the Pfirrmann system for grading lumbar intervertebral disk (IVD) degeneration in humans can also be used in dogs.

ANIMALS

202 dogs.

PROCEDURES

Magnetic resonance imaging was used to obtain images of vertebral segments from dogs, which were reviewed separately by 3 observers who graded the extent of degeneration in each visible IVD by use of the Pfirrmann classification system used for grading lumbar IVD degeneration in humans. Grading was validated against 2 factors associated with the extent of disk degeneration: type of dog (chondrodystrophic or nonchondrodystrophic breeds) and age.

RESULTS

Interobserver and intraobserver agreement for Pfirrmann grading of IVD degeneration were good (κ scores, 0.81 to 0.93). An increase in the extent of disk degeneration was positively correlated with increases in age and with chondrodystrophic breed.

CONCLUSIONS AND CLINICAL RELEVANCE

The Pfirrmann system was reliably used to grade IVD degeneration in dogs of various breeds and ages. An increase in the extent of IVD degeneration was positively correlated with increases in age and with chondrodystrophic-type dogs.

Level of termination of the spinal cord and the dural sac: a magnetic resonance study

Previous studies concerning the level of termination of the human spinal cord have been carried out in unselected cadavers. We have used magnetic resonance imaging to determine this level of termination, and that of the dural sac, in normal living subjects. We found a wider range of the level of termination of both the spinal cord and dural sac and a higher median level of termination of each than is commonly described. These anatomical findings are of clinical relevance to clinicians practicing regional anesthesia.

Spinal cord diameters in cadaveric specimens and magnetic resonance scans, to assess embalming artefacts

It would be valuable to use cadaveric models of cervical vertebrae and spinal cord to assess how varying degrees of traumatic subluxation would relate to neurological damage. However, before such a study may be undertaken, it would be important to assess the degree of shrinkage of expansion of the spinal cord that occurs during the embalming process. This is achieved in this study by comparing diameters of cadaveric spinal cord to that of sagittal magnetic resonance scans of living subjects. The geometric measurements of radiographs in living subjects has been assessed but no direct model for spinal cord injury has been described [1]. If embalmed spinal cord diameters were a good estimator of living spinal cord diameters then cadaveric cervical spines could be used as a model. By reproducing various degrees of fracture and dislocation the extent of corresponding cord compression could be assessed. Our study shows that spinal cord dimensions increase after embalming using the Cambridge procedure [4].

Rotation cryotomy: medical and scientific value of a new serial sectioning procedure

Preparation of thin serial sections for comparative macromorphologic investigations has always represented a grave technical problem, especially in the case of regions in which bone as well as soft tissue are to be documented within their natural relations to each other in any desired sectional plane. Non-decalcified specimens up to the size of a whole cadaver are embedded in physiologic medium, precisely positioned, and deep-frozen to a specimen-ice block. A newly developed device, working on the basis of blades rotating at high speed, allows quick, successive removal of sections from the surface of the specimen block, with a thickness of each section infinitely variable between 0.1 and 5 mm. Following each cut, the new surface of the block can be documented photographically or on videotape for macromorphologic evaluation. So far more than 1,000 human, animal, and botanical specimens have been sectioned and evaluated with this method. In none of the cases were specimens damaged. Furthermore, any desired sectional plane could be adjusted: consequently a definite correlation between these sections and previous sonography, magnetic resonance (MR), or computed tomography (CT) images could be established. As serial cryosectioning becomes available to a far wider circle of medical and natural scientists, high-quality results should be obtained at lower costs.

Effect of phase-encoding direction upon magnetic resonance image quality of the heart

In order to optimize overall cardiac image quality on MR images experienced observers were asked to rank and rate MR images of the heart. The effect of phase-encoding direction and use of cardiac triggering with and without respiratory gating was examined in three orthogonal imaging planes. Results indicate that use of both respiratory and cardiac gating yields the best images. Adequate images of the heart can be obtained without respiratory gating. The quality of images of the heart can be optimized by proper selection of the direction of the phase-encoding gradient. These are improved by using horizontal phase encoding in the sagittal plane and vertical phase encoding in transverse and coronal planes.