Why would a healthcare provider order a computed tomography (CT) scan over a magnetic resonance imaging (MRI) scan for back pain?

From the Guidelines

A healthcare provider would order a CT scan over an MRI for back pain primarily when they need to assess bone structures, such as in cases of suspected fractures, or when MRI is not feasible due to patient factors like metal implants or claustrophobia. This decision is based on the most recent and highest quality study, which suggests that CT scans are useful for preoperative planning, assessing facets and neural foramina, and predicting significant spinal stenosis and excluding cauda equina impingement 1.

Key Considerations

• CT scans are generally more accessible and less expensive than MRIs, and they take only minutes to complete, making them ideal for emergency situations where rapid imaging is necessary.
• CT scans excel at visualizing bone structures, making them suitable for detecting vertebral fractures, bony abnormalities, or calcifications.
• While MRIs provide superior soft tissue detail for conditions like herniated discs or nerve compression, CT scans remain valuable when speed, cost, or patient factors limit MRI use.
• The radiation exposure from CT scans is a consideration, but the benefit often outweighs this risk when timely diagnosis is essential for proper treatment of acute back pain with potentially serious underlying causes.

Clinical Context

In clinical practice, the choice between CT and MRI scans for back pain depends on various factors, including the patient's medical history, symptoms, and the suspected underlying cause of the pain. According to the American College of Radiology, MRI of the lumbar spine is the initial imaging modality of choice for patients with subacute or chronic low back pain who have failed conservative therapy 1. However, CT scans may be preferred in certain situations, such as when MRI is not available or when patients have contraindications to MRI, as noted in a study published in the Annals of Internal Medicine 1.

Evidence-Based Decision Making

The decision to order a CT scan over an MRI for back pain should be based on the most recent and highest quality evidence. A study published in the Journal of the American College of Radiology in 2021 provides guidance on the appropriate use of imaging modalities for low back pain, including CT scans and MRIs 1. This study suggests that CT scans are useful for assessing bone structures and predicting significant spinal stenosis, and that they may be preferred in certain situations, such as when MRI is not feasible.

From the Research

Reasons for Choosing CT Scan over MRI Scan for Back Pain

• A healthcare provider may order a computed tomography (CT) scan over a magnetic resonance imaging (MRI) scan for back pain due to several reasons, including:
  • The patient's specific condition, such as ankylosing spinal disorders or osteoporotic vertebral fractures, where CT scans are considered more effective in visualizing the fracture and its extension 2, 3
  • The need to identify noncontiguous fractures or disco-ligamentous injuries, where CT scans are more suitable 2
  • The presence of neurological deficits that require investigation of the spinal canal, where MRI scans are more appropriate 2
  • The patient's age, medical history, and other factors that may influence the choice of imaging modality 4, 5

Clinical Considerations

• The choice between CT and MRI scans for back pain also depends on clinical considerations, such as:
  • The severity and duration of back pain 4, 6
  • The presence of red flags, such as fever, weight loss, or recent trauma 4
  • The patient's overall health status and medical history 4, 5
  • The availability and cost of imaging modalities 4, 5

Imaging Modalities

• CT scans are generally considered better than MRI scans for:
  • Visualizing bony structures and fractures 2, 3
  • Identifying noncontiguous fractures or disco-ligamentous injuries 2
• MRI scans are generally considered better than CT scans for:
  • Visualizing soft tissue structures, such as discs and nerves 2, 6
  • Identifying neurological deficits or spinal canal injuries 2