Types Of MRI Scan For The Spine

Introduction

MRI scans

Magnetic Resonance Imaging (MRI) has revolutionised the field of diagnostic medicine, offering a non-invasive and highly detailed look into the human body. MRI scans for internal body structures are produced by strong magnetic fields and radio waves. The scans are performed by an MRI scanner, which is a large tube containing powerful magnets that function as you lie inside the tube. MRI scans can be focussed on different body parts, including the brain and spinal cord, bones and joints, breasts, heart and blood vessels and other internal organs. With the use of MRI scans, medical professionals can perform condition diagnosis, treatment planning, and assessment of the effectiveness of treatments.¹ 

Why do you need MRI scans for the spine?

When it comes to spinal issues, various types of MRI scans play a crucial role in providing accurate diagnoses and informing treatment plans. They can detect inflammation, bleeding, nerve root compression and other problems, such as:

• Tumours
• Collections of pus (abscesses)
• Congenital (since birth) abnormalities of the spine or brain
• Weakening and ballooning of an artery (aneurysm)
• Abnormal and dilated veins (venous malformations)
• Bleeding into the brain or spinal cord
• Herniation or degeneration of disks of the spine

Sometimes, MRI scans are also useful for planning surgeries of the spine, including decompression of a pinched nerve or spinal fusion, and for post-surgery examination.² 

Basic types of MRI scans for the spine

MRI is a versatile diagnostic tool, especially when it comes to examining the intricate structures of the spine. Each type of MRI scan offers unique insights, allowing healthcare professionals to visualise and diagnose various spinal conditions.

MRI scans can visualise the anatomy of the spine in three planes:

• Axial: from top to down
• Sagittal: from side to side
• Coronal: from front to back³

T1-weighted imaging

T1-weighted imaging is a fundamental sequence in spinal MRI that provides excellent anatomical detail, by highlighting differences in tissue composition. In this sequence, fluids appear dark, while fat and certain structures, such as the cortical bone, appear bright, as the T1-weighted images enhance the signal of the fatty tissue (bright), while they suppress the signal of water (dark). T1-weighted images are crucial for assessing the overall anatomy of the spine, aiding in the identification of bone lesions, vertebral fractures, and disc degeneration. Additionally, T1-weighted images are often used to evaluate the spinal cord and the surrounding soft tissues.⁴

T2-weighted Imaging

 T2-weighted imaging is another advanced sequence that is based on emphasising the contrast between different soft tissues, to provide highly detailed scans of the targeted area. In T2-weighted images, fluids appear bright as they enhance the signal of water, making it an excellent choice for detecting abnormalities in the spinal cord, nerve roots, and intervertebral discs. This sequence is particularly valuable for identifying conditions such as spinal stenosis, disc herniation, and infections. T2-weighted imaging plays a crucial role in assessing the health and integrity of the spinal structures.⁴

Fluid-attenuated inversion recovery (FLAIR) imaging

FLAIR imaging is designed to suppress the cerebrospinal fluid (CSF) signal, enhancing the visibility of lesions and abnormalities that might otherwise be obscured. This sequence is beneficial in spinal imaging, when the aim is to detect subtle changes in the brain and spinal cord, such as demyelinating disorders and inflammatory conditions. FLAIR is particularly effective in highlighting periventricular lesions and lesions near the CSF spaces, contributing to a more accurate diagnosis of certain spinal pathologies.⁵

Gadolinium-enhanced Imaging

Gadolinium-enhanced imaging involves the use of a contrast agent to improve the visualisation of blood vessels, tumours, and areas of inflammation. This type of MRI scan is essential for assessing conditions like spinal tumours, vascular malformations, and inflammatory disorders. By injecting gadolinium intravenously, healthcare professionals can identify and characterise abnormal growths or areas of increased blood flow within the spinal structures. This enhances diagnostic precision, and aids in treatment planning.⁶

These basic types of MRI scans serve as the foundation for spinal imaging, providing comprehensive information about the structure and health of the spine. Depending on the clinical scenario, healthcare professionals may use a combination of these sequences to obtain a holistic understanding of the patient's spinal health and to guide appropriate interventions.

Functional MRI (fMRI) for the spine

Functional magnetic resonance imaging (fMRI) provides insights into the dynamic aspects of spinal cord function. While not as common as structural imaging, fMRI can offer valuable information for understanding neural activity and can assist in planning surgeries involving the spine.

fMRI is a specialised application of MRI technology that focuses on capturing dynamic changes in blood flow, enabling the visualisation of neural activity within the spinal cord. While traditionally associated with brain studies, fMRI has been increasingly finding relevance in spinal research, offering valuable insights into the functional aspects of the spinal cord.

Functional imaging overview

Functional MRI operates on the principle of blood oxygen level-dependent (BOLD) contrast, where changes in blood flow and oxygenation are detected and used as indicators of neural activity. In spinal fMRI, this technology allows researchers and clinicians to observe real-time changes in blood flow within the spinal cord, in response to various stimuli or tasks taken by the patient.⁷

Applications in spinal cord studies

• Pain Perception and Processing: fMRI is utilised to investigate how the spinal cord processes pain signals. By exposing individuals to specific stimuli, researchers can map the regions of the spinal cord associated with pain perception. This information is valuable for understanding chronic pain conditions and developing targeted interventions.⁸
• Motor Function and Rehabilitation: Studying the spinal cord's response during motor tasks provides insights into motor function and recovery after spinal cord injuries. fMRI helps to identify areas of the spinal cord that are involved in voluntary movements, facilitating the design of rehabilitation strategies that can enhance motor recovery.⁹
• Neuroplasticity: fMRI contributes to our understanding of neuroplasticity within the spinal cord, which is the ability of the nervous system to reorganise and adapt, through the formation of new neural connections, or the strengthening of existing ones. This is particularly relevant in cases of spinal cord injury, where fMRI can reveal changes in neural activity associated with adaptive processes.¹⁰
• Mapping Sensory Pathways: By stimulating sensory nerves and observing the corresponding spinal cord activation, fMRI aids in mapping sensory pathways. This is crucial for understanding how the spinal cord processes and transmits sensory information, with implications for conditions like neuropathic pain.¹¹
• Evaluation of Therapeutic Interventions: Researchers use fMRI to assess the effectiveness of therapeutic interventions for spinal cord disorders like biopsy, and the treatment of primary spinal tumours and metastatic diseases. This includes evaluating the impact of medications, neurostimulation techniques, and rehabilitative approaches on spinal cord function.¹²

Emerging technologies

Recent advancements in MRI technology, including high-resolution imaging and higher field strengths like 7.0 Tesla MRI, contribute to improved spatial resolution and diagnostic accuracy. Additionally, artificial intelligence applications, such as deep learning-driven ultra-fast musculoskeletal MRI, enhance the efficiency and accuracy of image interpretation, potentially revolutionising spinal diagnostics.¹³

Considerations and precautions

Ensuring patient safety and comfort is paramount in spinal MRI. Adequate patient preparation, including screening for contraindications such as metal implants, pregnancy, and claustrophobia, among others, is essential. As MRI functions with a strong magnet, it cannot be used under some circumstances:

• Having an implanted pacemaker or cardiac defibrillator
• Having older intracranial aneurysm clips
• Having cochlear implants
• Having certain prosthetic devices
• Having implanted medicine infusion pumps or medicine ports
• Use of neurostimulators before/during the examination
• Use of bone-growth stimulators before/during the examination
• Using certain intrauterine contraceptive devices
• Having any other type of iron-based metal implants
• Tattoos (can rarely cause inflammation but can undergo scan) or body piercings (must be removed)
• Having metal items within the body, like bullets, fragments, surgical clips, pins, plates, screws, metal sutures, or wire mesh²

Understanding and mitigating the potential risks can contribute to a successful imaging procedure. If you are getting an MRI scan, you must inform the radiographer whether you are allergic to any medicine, contrast dye, or iodine. It is also important to tell them whether you have had kidney disease, kidney failure, kidney transplant, liver disease, or are on dialysis or not, as people with these conditions may experience serious complications from the use of the contrast dye, even though this is very rare. In general, there is no need to fast beforehand or limit any activities before having an MRI scanning procedure. 

Summary

In conclusion, the various types of MRI scans for the spine provide a comprehensive toolkit for clinicians to assess and diagnose spinal conditions. From the foundational T1 and T2-weighted imaging, to advanced techniques like diffusion-weighted imaging and magnetic resonance neurography, each sequence serves a specific purpose in unravelling the mysteries of spinal pathology. As technology continues to advance, the future of spinal MRI holds promise, with emerging technologies and artificial intelligence further enhancing our ability to understand and treat spinal issues.