Lower limit of iron quantification using dual-energy CT - a phantom study.

Area of Science:

• Medical Imaging
• Radiology
• Quantitative Imaging

Background:

• Dual-energy computed tomography (DECT) shows promise for quantifying hepatic iron concentration (IC).
• Establishing the lower limit of quantification (LLOQ) is crucial for clinical adoption.
• Previous studies have not definitively established the LLOQ for DECT-based IC quantification.

Purpose of the Study:

• To establish the LLOQ for hepatic iron concentration (IC) using dual-energy computed tomography (DECT).
• To investigate the impact of patient size, radiation dose, energy settings, and reconstruction techniques on DECT's IC quantification accuracy.

Main Methods:

• Phantoms of varying sizes and ferric nitrate solutions were used to simulate different IC levels.
• DECT scans were acquired using different kVp combinations (80/140 kVp and 100/140Sn kVp) and CT dose indices (CTDI).
• An image-domain three-material-decomposition algorithm calculated IC, with LLOQ determined by the coefficient of variation.

Main Results:

• Strong correlation between measured and true IC in small/medium phantoms (R² > 0.99), moderate in large phantoms (0.8 < R² < 0.9).
• LLOQ improved with increased CTDI; at 30 mGy, LLOQ was 0.50/1.73/6.25 mg/ml for small/medium/large phantoms.
• 80/140Sn kVp and iterative reconstruction yielded superior LLOQ compared to other settings.

Conclusions:

• DECT successfully quantified clinically relevant hepatic iron concentrations in small and medium phantoms.
• Quantification in large phantoms remained challenging, highlighting limitations.
• Optimal spectral separation and precise calibration are critical for accurate DECT-based iron quantification.