From the Guidelines
A lumbosacral CT scan typically delivers a radiation dose of approximately 10 to 25 mSv for a single study. This dose range is based on the effective dose estimates for computed tomographic (CT) scans, as reported in the American College of Radiology white paper on radiation dose in medicine 1. The radiation exposure from a lumbosacral CT scan occurs because CT scanners use X-rays to create detailed cross-sectional images of the spine, surrounding tissues, and neural structures.
Factors Affecting Radiation Dose
- Patient-specific factors, such as body size, can affect the dose, with larger patients typically requiring more radiation to penetrate tissues adequately.
- The specific protocol and equipment used can also impact the radiation dose.
- Modern CT scanners often incorporate dose reduction technologies, such as iterative reconstruction algorithms and automatic exposure control, to minimize radiation while maintaining diagnostic image quality.
Clinical Considerations
- While the radiation dose from a lumbosacral CT scan presents a small theoretical risk of cancer induction, the immediate diagnostic benefit usually outweighs this risk for patients with appropriate clinical indications, such as suspected fractures, disc herniations, spinal stenosis, or tumors.
- For pregnant patients or young individuals who may be more sensitive to radiation effects, alternative imaging methods like MRI might be considered when clinically appropriate, as the risk of radiation-induced cancer is a concern, especially at high doses, with a statistically significant increase in cancer at dose estimates in excess of 50 mSv, as shown in the study of atomic bomb survivors in Japan 1.
From the Research
Radiation Dose of Lumbosacral CT Scan
- The radiation dose of a Lumbosacral (lower back and sacrum) Computed Tomography (CT) scan can be reduced using various techniques, such as tailoring the scan to the patient, minimizing scan length, and using tube current modulation 2.
- A study on low-dose CT of the lumbar spine found that the effective dose was around 1.0-1.1 mSv, which is comparable to or even lower than the dose from radiography 3.
- Another study found that the use of body mass index (BMI) and automatic exposure control (AEC) can reduce the radiation dose of CT volume scans of the lumbar spine without compromising image quality 4.
- The radiation dose for specific CT scan protocols can vary, with reported doses ranging from 1.8 mGy for thoracic bone visualization to 10.6 mGy for lumbar soft-tissue visualization 5.
Factors Affecting Radiation Dose
- Patient size and body mass index (BMI) can affect the radiation dose, with larger patients requiring higher doses to achieve adequate image quality 4.
- The use of automatic exposure control (AEC) can help reduce the radiation dose by adjusting the tube current and voltage based on the patient's size and anatomy 4.
- The type of CT scanner and scan protocol used can also impact the radiation dose, with newer scanners and protocols often providing lower doses while maintaining image quality 6.
Image Quality and Diagnostic Information
- Low-dose CT scans of the lumbar spine can provide superior image quality and diagnostic information compared to radiography, with better visualization of anatomical structures and pathological changes 3.
- The use of low-dose CT scans can also reduce the time required to review images and make diagnoses, with reported review times of around 204 seconds for low-dose CT compared to 152 seconds for radiography 3.