Low dose CT of the lumbar spine compared with radiography: a study on image quality with implications for clinical practice

Abstract

Background Lumbar spine radiography is often performed instead of CT for radiation dose concerns. Purpose To compare image quality and diagnostic information from low dose lumbar spine CT at an effective dose of about 1 mSv with lumbar spine radiography. Material and Methods Fifty-one patients were examined by both methods. Five reviewers scored all examinations on eight image quality criteria using a five-graded scale and also assessed three common pathologic changes. Results Low dose CT scored better than radiography on the following: sharp reproduction of disc profile and vertebral end-plates (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.3–2.5), intervertebral foramina and pedicles (OR, 4.3; 95% CI, 3.1–5.9), intervertebral joints (OR, 139; 95% CI, 59–326), spinous and transverse processes (OR, 7.0; 95% CI, 4.3–11.2), sacro-iliac joints (OR, 4.2; 95% CI, 3.2–5.7), reproduction of the adjacent soft tissues (OR, 2.9; 95% CI, 2.1–4.0), and absence of any obscuring superimposed gastrointestinal gas and contents (OR, 188; 95% CI, 66–539). Radiography scored better on sharp reproduction of cortical and trabecular bone (OR, 0.3; 95% CI, 0.2–0.4). The reviewers visualized disk degeneration, spondylosis/diffuse idiopathic skeletal hyperostosis (DISH) and intervertebral joint osteoarthritis more clearly and were more certain with low dose CT. Mean time to review low dose CT was 204 s (95% CI, 194–214 s.), radiography 152 s (95% CI, 146–158 s.). The effective dose for low dose CT was 1.0–1.1 mSv, for radiography 0.7 mSv. Conclusion Low dose lumbar spine CT at about 1 mSv has superior image quality to lumbar spine radiography with more anatomical and diagnostic information.