Imaging of the spine and spinal cord: An overview of magnetic resonance imaging (MRI) techniques

Toward Functional PET Imaging of the Spinal Cord

At present, spinal cord imaging primarily uses magnetic resonance imaging (MRI) or computed tomography (CT), but the greater sensitivity of positron emission tomography (PET) techniques and the development of new radiotracers are paving the way for a new approach. The substantial rise in publications on PET radiotracers for spinal cord exploration indicates a growing interest in the functional and molecular imaging of this organ. The present review aimed to provide an overview of the various radiotracers used in this indication, in preclinical and clinical settings. Firstly, we outline spinal cord anatomy and associated target pathologies. Secondly, we present the state-of-the-art of spinal cord imaging techniques used in clinical practice, with their respective strengths and limitations. Thirdly, we summarize the literature on radiotracers employed in functional PET imaging of the spinal cord. In conclusion, we propose criteria for an ideal radiotracer for molecular spinal cord imaging, emphasizing the relevance of multimodal hybrid cameras, and particularly the benefits of PET-MRI integration.

Diffusion Tensor Imaging Identifies Cervical Spondylosis, Myelitis, and Spinal Cord Tumors

BACKGROUND

Diffusion tensor imaging (DTI) has been increasingly recognized for its capability to study microstructural changes in the neuropathology of brain diseases. However, the optimal DTI metric and its diagnostic utility for a variety of spinal cord diseases are still under investigation.

PURPOSE

To evaluate the diagnostic efficacy of DTI metrics for differentiating between cervical spondylosis, myelitis, and spinal tumors.

METHODS

This retrospective study analyzed DTI scans from 68 patients (22 with cervical spondylosis, 23 with myelitis, and 23 with spinal tumors). DTI indicators, including fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD) and axial diffusivity (AD), were calculated. The Kruskal-Wallis test was used to compare these indicators, followed by Receiver Operating Characteristic (ROC) curve analysis, to evaluate the diagnostic efficacy of each indicator across disease pairs. Additionally, we explored the correlations of DTI indicators with specific clinical measurements.

RESULTS

FA values were significantly lower in tumor patients compared to those with cervical spondylosis (p < 0.0001) and myelitis (p < 0.05). Additionally, tumor patients exhibited significantly elevated MD and RD values relative to the spondylosis and myelitis groups. ROC curve analysis underscored FA's superior discriminative performance, with an area under the curve (AUC) of 0.902 for differentiating tumors from cervical spondylosis, and an AUC of 0.748 for distinguishing cervical myelitis from spondylosis. Furthermore, a significant negative correlation was observed between FA values and Expanded Disability Status Scores (EDSSs) in myelitis patients (r = -0.62, p = 0.002), as well as between FA values and Ki-67 scores in tumor patients (r = -0.71, p = 0.0002).

CONCLUSION

DTI indicators, especially FA, have the potential in distinguishing spondylosis, myelitis, and spinal cord tumors. The significant correlation between FA values and clinical indicators highlights the value of FA in the clinical assessment and prognosis of spinal diseases and may be applied in diagnostic protocols in the future.

Axial T1-weighted imaging of the lumbar spine: a redundancy or an asset?

OBJECTIVE

To determine the diagnostic value of axial T1-weighted imaging for patients suffering from lower back pain.

MATERIALS AND METHODS

In this retrospective study, 100 consecutive lumbar spine MRIs obtained in patients with chronic low back pain were reviewed in two sessions: First, readers viewed core sequences (sagittal T1-weighted, STIR and T2-weighted, and axial T2-weighted) with axial T1-weighted sequences, and second, readers viewed cores sequences alone. Readers recorded the presence of disc degeneration, nerve root compromise, facet joint arthritis, and stenosis at each lumbar spine level as well as the presence of lipoma of filum terminale (LFT), spondylolisthesis, transitional vertebrae, and fractures. The McNemar, Wilcoxon signed-rank, and student T tests were utilized.

RESULTS

For 100 studies, 5 spine levels were evaluated (L1-L2 through L5-S1). There were cases of disc disease (444/500 bulges, 56/500 herniations), nerve root compromise (1/500 nerve enlargement, 36/500 contact only, 20/500 displacement or compression), facet arthritis (438/500), stenosis (58/500 central canal, 64/500 lateral recess, 137/500 neuroforaminal), 6/100 LFTs, and other abnormalities (58/500 spondylolisthesis, 10/100 transitional vertebrae, 10/500 fracture/spondylolysis). There was no difference in diagnostic performance between the interpretation sessions (with and without axial T1-weighted imaging) at any level (p > 0.05), although four small additional LFTs were identified with axial T1-weighted imaging availability.

CONCLUSION

There was no clinically significant difference in the interpretation of lumbar spine MRI viewed with and without axial T1-weighted imaging, suggesting that the axial T1-weighted sequence does not add diagnostic value to routine lumbar spine MRI.

Neurologic pathologies of the vertebral spine

At some institutions, musculoskeletal and general radiologists rather than neuroradiologists are responsible for reading magnetic resonance imaging (MRI) of the spine. However, neurological findings, especially intrathecal ones, can be challenging. Intrathecal neurological findings in the spine can be classified by location (epidural, intradural extramedullary, and intramedullary) or etiology (tumor, infection, inflammatory, congenital). In this paper, we provide a succinct review of the intrathecal neurological findings that can be seen on MRI of the spine, primarily by location and secondarily by etiology, in order that this may serve as a helpful guide for musculoskeletal and general radiologists when encountering intrathecal neurological pathologies.

Vascular Myelopathies

There are many vascular disorders that can affect the spinal cord, and their prevalence and etiology are highly influenced by age, sex, and risk factors. This article reviews the embryology and anatomy of the spinal cord, as well as several vascular conditions, describing their clinical and imaging presentation, emphasizing the different imaging modalities' contributions to increasing specificity and better defining the most appropriate therapy strategy for improving the patient's prognosis.

Developmental Abnormalities of the Pediatric Spine: A Review of the Correlation Between Ultrasound and MRI Findings

A broad spectrum of spinal pathologies can affect the pediatric population. Ultrasound (US) is the primary modality for pediatric spine assessment due to its widespread availability, non-requirement of sedation, and absence of ionizing radiation. Supplementing this, MRI offers an in-depth exploration of these conditions, aiding in preoperative strategizing. In this review, we examine the clinical indications, methodologies, and protocols for US and MRI scans of the pediatric spine. Additionally, we illustrate normal pediatric spinal anatomy, highlighting several examples of normal variants that are often misinterpreted. Through a series of case-based illustrations, we offer a comprehensive overview of various pathological conditions such as tethered cord, spinal dysraphism, spinal lipoma, diastematomyelia, and dermal sinus tract, among others. Furthermore, we explore the correlation between US and MRI findings for these lesions, employing real-world cases to enhance our understanding of this topic.

Quantitative MRI evaluation of bone marrow in sickle cell disease: relationship with haemolysis and clinical severity

AIM

To evaluate bone marrow fat fraction using the Dixon technique (FFDix) of magnetic resonance imaging (MRI) as a potential biomarker of haemolysis and clinical severity in the overall assessment and follow-up of sickle cell disease (SCD) patients.

MATERIAL AND METHODS

The present study was a cross-sectional study in which healthy individuals and SCD patients (matched for age, sex, and weight) were subjected to MRI of the lumbar spine and pelvis to quantify FFDix in the bone marrow using the Dixon technique. SCD severity was analysed by clinical and laboratory data, and an online calculator. A high degree of haemolysis was defined using the cut-off values haemoglobin (Hb) ≤10 g/dl, lactate dehydrogenase (LDH) ≥325 U/l, reticulocytes ≥3% and total bilirubin (TB) ≥1.2 mg/dl. Pearson's correlation, receiver operating characteristic (ROC) curve and binary logistic regression analysis were performed.

RESULTS

Forty-eight SCD patients (26 homozygous: HbSS and 22 compound heterozygous: HbSC) and 48 healthy individuals participated in the study. FFDix was lower in SCD patients than in the control group, showing even lower values in the HbSS subtype and patients with a higher degree of haemolysis. HbSC patients with a higher degree of haemolysis using hydroxyurea (medium dosage 9.8 mg/kg/day) had lower FFDix. ROC curves and odds ratios for detecting patients with a higher degree of haemolysis at the different FFDix measurement sites demonstrated excellent performance: iliac bones (cut-off ≤16.75%, AUC = 0.824, p<0.001), femoral heads (cut-off ≤46.7%, AUC = 0.775, p=0.001), lumbar vertebrae (cut-off ≤7.8%, AUC = 0.755, p=0.002).

CONCLUSION

Decreased FFDix is indicative of higher degree of haemolysis and SCD severity with great potential as a non-invasive biomarker contributing to the overall assessment and follow-up of SCD patients.

Multiacquisition with variable resonance image combination T2 (MAVRIC SL T2) for postoperative cervical spine with artificial disc replacement

Anterior cervical discectomy with artificial disc replacement (ADR) is an effective treatment of cervical degenerative disc disease. However, postoperative MRI due to recurrent neck/radicular pain is limited due to severe metallic artifacts of artificial disc instrument. Multiacquisition with variable resonance image combination selective T2 (MAVRIC SL T2) has been developed as an MRI technique for metal artifact reduction but has not been evaluated for the postoperative cervical spine with ADR. In our study, we compared MAVRIC SL T2 with the fast spin echo (FSE) T2-weighted sequence (T2WI), which was an essential MR sequence for evaluation of the cervical neural structure, for metallic artifact reduction in the post-operative cervical spine with ADR. Our study revealed MAVRIC SL T2 showed smaller signal void areas, less distortion and signal pile-up, and was more clinically useful than T2WI (p < 0.05). The spinal cord, vertebral bodies, both neural foramina, and anterior paravertebral soft tissue were significantly more visible with MAVRIC SL T2 than with T2WI (p < 0.05). MAVRIC SL T2 might be a useful technique for the evaluation of postoperative cervical spine with ADR and complements T2WI in the evaluation of the spinal cord and nerve roots which were important structures for post-operative recurrent neck/radicular pain.

Imaging of Common Spinal Cord Diseases

Spinal cord evaluation is an integral part of spine assessment, and its reliable imaging work-up is mandatory because even localized lesions may produce serious effects with potentially irreversible sequelae. Spinal cord alterations are found both incidentally during spine evaluation in otherwise neurologically asymptomatic patients or during neurologic/neuroradiologic assessment in myelopathic patients. Myelopathy (an umbrella term for any neurologic deficit that refers to spinal cord impairment) can be caused by intrinsic lesions or extrinsic mechanical compression, and its etiology may be both traumatic and/or nontraumatic. The symptoms largely depend on the size/extension of lesions, ranging from incontinence to ataxia, from spasticity to hyperreflexia, from numbness to weakness. Magnetic resonance imaging is the reference imaging modality in spinal cord evaluation, ensuring the best signal and spatial resolution. We provide an overview of the most common spinal cord disorders encountered by radiologists and describe the technical measures that offer optimal spinal cord visualization.

Spinal vascular lesions: anatomy, imaging techniques and treatment

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Vascular myelopathies include different aetiology and mechanism of damage.

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The level of the lesion and the localization within the SC correlates with the clinical symptoms.

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CT, MRI and angiography are essential for diagnosis and treatment playing a complementary role.

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MRI is the gold standard for the evaluation of spinal cord lesions.

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Spinal angiography is the gold standard for evaluation of spinal cord vasculature and vascular malformations.

Background

Vascular lesions of the spinal cord are rare but potentially devastating conditions whose accurate recognition critically determines the clinical outcome. Several conditions lead to myelopathy due to either arterial ischemia, venous congestion or bleeding within the cord. The clinical presentation varies, according with the different aetiology and mechanism of damage.

Purpose

The aim is to provide a comprehensive review on the radiological features of the most common vascular myelopathies, passing through the knowledge of the vascular spinal anatomy and the clinical aspects of the different aetiologies, which is crucial to promptly address the diagnosis and the radiological assessment.