, Volume 22, Issue 1, pp 251-258
Date: 17 Aug 2011

Targeted dual-energy single-source CT for characterisation of urinary calculi: experimental and clinical experience

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Abstract

Objective

To assess the accuracy of targeted dual-energy single-source multi-detector CT (MDCT) for characterisation of urinary calculi.

Methods

For proof of principle, 71 ex-vivo calculi underwent single-source 256-slice MDCT. Low-dose CT was performed in 154 patients with suspected urinary calculi. In 104 patients with urinary calculi targeted dual-energy imaging within one breath-hold was added. 46 patients with sufficient material for infrared-spectroscopy were analysed. Potential anatomical misregistrations between 80- and 140-kVp-images and HU-values were measured. DEIs (dual-energy-indices) were compared with the standard of reference. Effective doses were calculated.

Results

In 26 of 46 patients no misregistration was present. Mean deviations were 2.7 mm in the z-axis (16 patients) and 4.3 mm in the axial plane (10 patients). The DEIs were 0.018 ± 0.016 for uric acid (UA), 0.035 ± 0.015 for mixed UA and 0.102 ± 0.015 for calcified stones in-vitro and 0.017 ± 0.002 for UA, 0.050 ± 0.019 for mixed UA and 0.122 ± 0.024 for calcified calculi in-vivo. Significant differences were noted among calcium, mixed UA and UA stones (p < 0.05). For the low-dose examination mean effective dose was 3.11 mSv. Targed dual-energy resulted in an extra dose of 1.84 mSv (additional 59.1%).

Conclusion

Targeted dual-energy imaging within one breath-hold is feasible for characterisation of urinary calculi using single-source MDCT allowing minimal anatomical discordance.

Key Points

• Targeted dual-energy single-source CT is feasible for characterizing urinary calculi

Dual Energy Index discriminates between uric-acid and non-uric-acid containing stones

It provides ancillary for decisions about stone removal or metaphylaxis