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Ultra-low-dose CT versus radiographs for minor spine and pelvis trauma: a Bayesian analysis of accuracy

  • Musculoskeletal
  • Published:
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To compare diagnosis performance and effective dose of ultra-low-dose CT (ULD CT) versus radiographs in suspected spinal or pelvic ring or hip fracture for minor trauma.


ULD CT, in addition to radiography, was prospectively performed in consecutive patients admitted to the emergency department for minor traumas, during working hours over 2 months. Presence of a recent fracture was assessed by two blind radiologists independently. Sensitivities and specificities were estimated using the best valuable comparator (BVC) as a reference and using a latent class model in Bayesian inference (BLCM). Dosimetric indicators were recorded and effective doses (E) were calculated using conversion coefficient.


Eighty areas were analyzed in 69 patients, including 22 dorsal spine, 28 lumbar spine, and 30 pelvic ring/hip. Thirty-six fractures (45%) were observed. Applying the BVC method, depending on location, ULD CT sensitivity was 80 to 100% for reader 1 and 85 to 100% for reader 2, whereas radiographic sensitivity was 60 to 85% for reader 1 and 50 to 92% for reader 2. With BLCM approach for reader 2, ULD CT sensitivity for all locations/dorsal spine/lumbar spine and pelvic ring-hip was 87.1/75.9/84.2/76.9% respectively. Corresponding radiograph sensitivity was 73.8, 54.8, 80.4, and 68.7%. Effective doses of ULD CT were similar to radiographs for dorsal and hip locations whereas for lumbar spine, ULD CT effective dose was 1.83 ± 0.59 mSv compared with 0.96 ± 0.59 mSv (p < 0.001).


Sensitivity for fracture detection was higher for ULD CT compared with radiographs with an effective dose comparable to radiographs.

Key Points

• Ultra-low-dose spine and pelvis CT demonstrates better fracture detection when compared with radiographs.

• The effective dose of ultra-low-dose spine and pelvis CT scan and radiographs is comparable.

• Replacement of radiographs by ULD CT in daily practice for trauma patients is an option to consider and should be evaluated by a randomized trial.

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Best valuable comparator

CTDIvol :

Volume CT dose index


Dose area product


Dose length product


Effective dose

eDAP :

Region-specific conversion coefficient to calculate ERX

eDLP :

Region-specific conversion coefficient to calculate EULD


Effective dose for each radiograph examination


Effective dose calculated for each ULD CT examination


Iterative reconstruction


Magnetic resonance imaging


Picture archiving and communication system


Ultra-low-dose computed tomography


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Correspondence to Aymeric Hamard.

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The scientific guarantor of this publication is Jean Paul Beregi, MD, PhD.

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The authors of this manuscript declare no relationships with any companies whose products or services may be related to the subject matter of the article.

Statistics and biometry

One of the authors has significant statistical expertise: Sophie Bastide, MD

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Written informed consent was obtained from all subjects (patients) in this study.

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Institutional Review Board approval was obtained.


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Hamard, A., Greffier, J., Bastide, S. et al. Ultra-low-dose CT versus radiographs for minor spine and pelvis trauma: a Bayesian analysis of accuracy. Eur Radiol 31, 2621–2633 (2021).

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