Evaluating Bone Mass with Opportunistic Chest CT: T8 as the Optimal Vertebral Level

Area of Science:

• Radiology
• Osteoporosis Research
• Medical Imaging

Background:

• Opportunistic chest CT (OC-CT) shows promise for early osteoporosis screening.
• Current limitations include specific patient populations and an undetermined optimal vertebral level for detection.

Purpose of the Study:

• Determine the optimal vertebral level for osteoporosis detection using OC-CT.
• Assess the feasibility and diagnostic performance of OC-CT compared to dual-energy X-ray absorptiometry (DXA).

Main Methods:

• Retrospective analysis of 1236 participants (≥50 years) with both DXA and routine chest CT scans.
• Receiver Operating Characteristic (ROC) analysis to evaluate diagnostic performance for low bone mass and osteoporosis.
• Analysis of 15,007 vertebrae (T1-T12, L1) for CT-averaged (CT_AV) values.

Main Results:

• CT_AV at T1-T12 and L1 vertebrae showed good discrimination (AUC > 0.80) for low bone loss and osteoporosis.
• The T8 vertebra achieved sensitivity > 0.80 for both conditions.
• Cut-off values for T8: 163.5 Hu (81% sensitivity, 84% specificity for low bone mass) and 132.3 Hu (82% sensitivity, 75% specificity for osteoporosis).

Conclusions:

• OC-CT demonstrates comparable diagnostic performance to DXA for bone mass evaluation in adults aged 50+.
• The T8 vertebra is recommended as the optimal site for opportunistic bone mass assessment.
• T7 and T10 are suitable alternatives, with a self-check table proposed for clinical utility.