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Image Quality and Radiation Dose in CBCT for Musculoskeletal Applications

A Ferrero*, D Magnuson , B Schueler , Mayo Clinic, Rochester, MN


(Tuesday, 7/31/2018) 10:00 AM - 10:30 AM

Room: Exhibit Hall | Forum 1

Purpose: Thanks to its high spatial resolution, compact gantry and potential for radiation dose reduction, cone-beam CT (CBCT) is an appealing alternative to diagnostic CT for musculoskeletal applications. In this work we compared image quality (IQ) and radiation dose for two extremity CBCT systems and a state-of-the-art diagnostic CT scanner.

Methods: A custom IQ phantom (16 cm diameter) was scanned using our routine protocols on a CurveBeam InReach extremity scanner (CBCT-A), a Siemens Multitom RAX scanner (CBCT-B) and a Siemens Force CT scanner (dCT). The reconstructed images were reformatted to 1mm slice thickness for all systems. In-plane spatial resolution and CT number accuracy for soft tissue and bone equivalent material were assessed for the wrist protocol. Radiation dose was measured using a 0.6cc ionization chamber at the center of a 10 cm phantom for all 3 systems, and replicated for wrist, knee and foot protocols.

Results: 16 lp/cm could be visualized with CBCT-A, compared to 13 lp/cm with CBCT-B and 16 lp/cm with dCT. CNR for the soft tissue and bone compartments were 1.6 and 9 for CBCT-A, 1.6 and 17 for CBCT-B and 2.4 and 20 for dCT, using the wrist protocol. For the same exam, the measured dose was 6.2 mGy for CBCT-A, 5.3 mGy for CBCT-B and 44.6 mGy for dCT.

Conclusion: State-of-the-art CBCT is clinically suitable for MSK applications, especially for evaluation of bony anatomy and pathology. However, bone and soft tissue contrast were found to be significantly inferior to diagnostic CT exams.


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