Low-Dose CT and Musculoskeletal Imaging: Which Dose Is Needed?

Aim: We evaluated the value and diagnostic possibilities of low-dose computed tomography (CT) in musculoskeletal imaging in everyday practice. An experimental study was added to determine the minimal achievable dose while keeping image quality at a high level.

Materials and Method: Low-dose CT scans of 70 patients (mostly CT of the pelvis) were evaluated, using a Likert scale to assess for image quality and diagnostic value. They were also compared with 58 normal-dose CTs of the same patients. Seven different CT protocols with and without tin-filter technology were tested, using a normal and an adipose phantom to determine the minimal achievable dose while keeping image quality high. Dose and objective (contrast-to-noise ratio) and subjective parameters were measured and compared.

Results: All 70 low-dose scans offered diagnostic image quality with a significantly reduced dose. The phantom study revealed that low-dose CTs can be performed for most clinical issues with diagnostic quality (normal-dose CT scan versus low dose using a normal phantom: 2.95–3.63 versus 0.35–1 mSv; adipose phantom: 6.79–9.11 versus 0.79–2.4 mSv). Using tin-filter technology can reduce the dose even more. Low-dose scans with tin filter at 33% dose compared with normal-dose CT achieved similar subjective results.

Conclusion: Low-dose CT scans, especially when using tin-filter technology, provide good image quality without lowering the diagnostic value for most clinical issues and reduce patient dose significantly at the same time. In our opinion these scans are a very good alternative, especially as a control scan and in young patients.