CT-based internal density calibration for opportunistic skeletal assessment using abdominal CT scans

Area of Science:

• Radiology and Medical Imaging
• Biomedical Engineering
• Orthopedics

Background:

• Computed Tomography (CT) scans can be used for opportunistic skeletal assessment, aiding in osteoporosis diagnosis.
• Traditional phantom-based calibration methods have limitations for quantitative CT analysis.
• Internal calibration techniques using in-scan tissue references offer a potential solution to overcome these limitations.

Purpose of the Study:

• To establish and validate an internal calibration technique for quantitative CT-based skeletal assessment using abdominal CT scans.
• To determine the reproducibility and precision of internal calibration compared to phantom-based calibration.
• To assess the utility of internal calibration for measuring bone mineral density (BMD) and finite element (FE) failure load.

Main Methods:

• Ten full-body cadavers were CT scanned at the spine and pelvis with a calibration phantom.
• Internal calibration was performed using in-scan tissue references to derive voxel-specific calibration.
• Three independent users assessed intra-exam precision by manual tissue selection; ten subjects were imaged using an abdominal protocol for verification.

Main Results:

• Internal calibration demonstrated performance comparable to gold-standard phantom-based calibration in cadaver spine and hip assessments.
• Spine BMD precision with internal calibration was 7 mg/cc (4.9%) and FE precision was 163 N (7.2%).
• Hip BMD precision with internal calibration was 11 mg/cc (5.3%) and FE precision was 84 N (6.0%), with overall outcome precision within 7.2%.

Conclusions:

• Internal calibration is a valid and reproducible technique for quantitative CT-based skeletal assessment, equivalent to phantom-based methods.
• This method overcomes limitations of phantom-based calibration and can be effectively implemented using abdominal CT scans.
• Internal calibration provides precise BMD and FE failure load measurements, supporting opportunistic skeletal health assessment and osteoporosis diagnosis.