The quantification of bone mineral density using photon counting computed tomography and its implications for...

Area of Science:

• Medical Imaging
• Radiology
• Bone Densitometry

Background:

• High-resolution peripheral quantitative CT (HR-pQCT) is standard for in vivo volumetric bone mineral density (vBMD) quantification.
• HR-pQCT's limitations include peripheral-only access, small fields of view, and long scan times, restricting clinical applicability.
• Photon counting CT (PCCT) presents a potential alternative for quantitative bone imaging.

Purpose of the Study:

• To evaluate the potential of PCCT for quantitative bone imaging.
• To assess PCCT's accuracy and repeatability in measuring vBMD and bone turnover.
• To determine the clinical feasibility of PCCT for bone analysis.

Main Methods:

• PCCT was calibrated using the European Forearm Phantom for hydroxyapatite (HA) density.
• Cadaveric forearms (n=8) were scanned with PCCT and HR-pQCT; volunteer forearms (n=2) were scanned twice with PCCT.
• Accuracy was assessed by paired total vBMD (Tt.vBMD) measurements; voxel-level repeatability was evaluated via image registration and subtraction of ex vivo PCCT scans.

Main Results:

• Paired Tt.vBMD measurements between PCCT and HR-pQCT showed a high Pearson correlation (0.986) with a bias of 7.46 mgHA/cm³.
• Voxel-level analysis of repeated PCCT scans revealed a bias of 17.66 mgHA/cm³ and a standard error of 96.23 mgHA/cm³.
• Least detectable remodeling was 250 mgHA/cm³, with <0.5% of voxels misclassified in cadavers (0.37%) and 0.97% in vivo.

Conclusions:

• PCCT demonstrates accuracy comparable to HR-pQCT for quantifying vBMD and bone turnover.
• The study provides proof of principle for PCCT's accuracy in vivo.
• PCCT holds significant potential for broader clinical applications in quantitative bone imaging.