Quantification of the difference in hounsfield units of an electron density phantom between a conventional and standing computed tomography machine

PMCID: PMC12174245

PMID: 40526177

DOI: 10.1007/s11259-025-10789-7

Journal: Veterinary research communications

Publication Date: 2025-6-17

Authors: Beck C, Morrice-West AV, Muir P, Hitchens PL, Whitton RC

Key Points

• HU values varied significantly between conventional and standing CT machines, with the greatest differences in high-density regions
• Mean HU values for dense bone-equivalent inserts showed up to 64.53 HU difference between machines (P < 0.001)
• Calibration using a bone-equivalent phantom is essential for accurate bone mineral density calculations across different CT systems

Summary

This veterinary imaging study investigated the variability of Hounsfield Units (HU) across two different CT machines - a conventional and a standing CT system - using an electron density phantom. The research aimed to assess potential differences in bone mineral density (BMD) estimation by comparing HU measurements across eight regions of interest with varying densities. Critically, the study revealed significant variations in HU values between machines, with the greatest disparities observed in denser phantom inserts representing bone-like structures.

The findings highlight the importance of machine-specific calibration when performing opportunistic BMD calculations in veterinary imaging. Differences in scanning parameters, including kilovoltage (kVp), field of view, and image reconstruction algorithms, contributed to HU value variations. The researchers developed machine-specific calibration curve equations to standardize BMD estimations, demonstrating that direct comparisons between CT machines without proper calibration could lead to inaccurate density measurements.