What is the radiation dose for a lumbosacral (lower back and sacrum) Computed Tomography (CT) scan?

From the Guidelines

The typical radiation dose for a lumbosacral CT scan is approximately 3.2-4.8 millisieverts (mSv) when using low-dose protocols. This dose range is based on the most recent guidelines and studies, such as those outlined in the European Journal of Nuclear Medicine and Molecular Imaging 1, which highlight the use of whole body-low dose-CT (WB-LDCT) protocols to minimize radiation exposure without compromising diagnostic accuracy.

Key Considerations

• The radiation dose for a lumbosacral CT scan can vary depending on the specific protocol, equipment, and patient factors.
• Low-dose CT protocols are designed to reduce radiation exposure while maintaining diagnostic quality, with doses ranging from 3.2-4.8 mSv 1.
• CT scans are valuable for evaluating bony structures, particularly in cases of trauma, fracture assessment, or when MRI is contraindicated.
• Alternative modalities like MRI may be considered for patients requiring multiple imaging studies, as they do not use ionizing radiation.

Minimizing Radiation Exposure

• Techniques like dose modulation, where the scanner adjusts radiation output based on tissue density, can help minimize radiation exposure.
• Limiting the scan field to only the necessary anatomy is also crucial in reducing radiation dose.
• Patients should be aware of the radiation exposure associated with CT scans, but also understand that the diagnostic benefits typically outweigh the risks when the scan is medically indicated.

Comparison with Other Imaging Modalities

• The radiation dose from a lumbosacral CT scan is higher than a standard X-ray but lower than more extensive CT scans of multiple body regions.
• MRI, which does not use ionizing radiation, may be an alternative for certain patients, especially those requiring repeated imaging studies. However, CT remains the preferred choice for specific indications due to its ability to evaluate bony structures accurately.

From the Research

Radiation Dose for Lumbosacral CT Scan

• The radiation dose for a lumbosacral (lower back and sacrum) Computed Tomography (CT) scan can be reduced to around 1 mSv, which is comparable to the dose from lumbar spine radiography 2, 3.
• A study found that low-dose lumbar spine CT at about 1 mSv has superior image quality to lumbar spine radiography, with more anatomical and diagnostic information 2.
• The optimal settings for low-dose lumbar spine CT can be achieved with a tube potential of 120 kV, reference mAs 30, and medium or medium smooth convolution filter, resulting in a sub-millisievert dose level 3.
• Technical developments in CT acquisition and reconstruction, such as artificial intelligence and photon counting CT, may also help reduce the radiation dose without compromising image quality 4.
• Simulating lower-dose scans from an existing standard-dose scan can also help determine the lowest possible radiation dose that still produces sufficient clinical information 5.

Image Quality Considerations

• Image quality is closely associated with radiation dose, and higher doses result in less apparent image noise and easier perception of low-contrast structures 6.
• Spatial resolution is ultimately limited by sampling, but both image noise and resolution are strongly affected by the reconstruction filter 6.
• Diagnostically acceptable image quality at acceptable doses of radiation requires appropriately designed clinical protocols, including appropriate kilovolt peaks, amperages, slice thicknesses, and reconstruction filters 6.