How to evaluate a spinal cord stimulator (SCS) via computed tomography (CT) scan?

From the Guidelines

CT scans are not the primary modality for evaluating spinal cord stimulators, but if used, should be performed with thin slices, high kV settings, and metal artifact reduction techniques to minimize interference. When evaluating a spinal cord stimulator via computed tomography (CT) scan, it is essential to consider the limitations and potential artifacts associated with this imaging modality. According to the guidelines for imaging in trauma patients 1, CT scans are highly sensitive for detecting bony injuries, but may not be the best option for evaluating spinal cord stimulators directly.

To evaluate a spinal cord stimulator using CT, the following protocols should be followed:

• Use thin slices (1-2 mm) to reduce artifact interference
• Employ high kV settings (typically 120-140 kV) and appropriate mA to minimize metal artifacts
• Utilize metal artifact reduction software (MARS) or iterative reconstruction techniques if available
• Position the patient carefully to align the spinal cord stimulator leads parallel to the scan plane when possible
• Turn off the stimulator prior to the scan according to manufacturer guidelines

It is crucial to note that while CT can help evaluate the general position of the hardware and detect gross complications like lead migration or fracture, it cannot assess the functional status of the device 1. For functional evaluation, clinical testing with the device programmer is necessary. Additionally, MRI may be a better option for some patients with MRI-conditional stimulator systems when soft tissue evaluation is needed, though this requires strict adherence to manufacturer safety protocols.

From the Research

Evaluating a Spinal Cord Stimulator via Computed Tomography (CT) Scan

To evaluate a spinal cord stimulator (SCS) via computed tomography (CT) scan, several factors should be considered:

• The positioning of the SCS electrodes within the spinal canal, typically in the epidural space in the posterior one third of the spinal canal 2
• The type of electrodes used, which can vary and may include percutaneous or surgical paddle electrodes 2, 3
• Potential complications, such as misplaced, retained, or broken leads, puncture of the thecal sac, infection, or hematoma, which can be identified on CT scans 2

CT Scan Evaluation

When evaluating an SCS via CT scan:

• Radiologists should be familiar with the different types of electrodes and their typical spinal locations 2, 3
• The CT scan can help identify the position of the electrodes within the spinal canal and detect any potential complications 2
• The imaging quality should be sufficient to answer the clinical question posed, despite potential technical challenges 4

Considerations for MRI vs. CT Scans

While MRI scans are frequently used to evaluate SCS devices, CT scans can also be used, especially when MRI is not feasible:

• MRI scans have specific absorption rate (SAR) limitations and technical challenges, but can provide diagnostically useful images 4, 5
• CT scans can be used to evaluate the positioning of SCS electrodes and detect potential complications, but may not provide the same level of detail as MRI scans 2, 3