Re: Characterization of Urinary Stone Composition by Use of Third-Generation Dual-Source Dual-Energy CT with Increased Spectral Separation

Objective: To assess accuracy of dual-energy computed tomography (DECT) to differentiate uric acid from calcium urinary stones in dual-energy split filter vs sequential-spiral vs dual-source acquisition. Methods: Thirty-four urinary stones (volume 89.0 ± 77.4 mm³; 17 calcium stones, 17 uric acid stones) were scanned in a water-filled phantom using a split-filter equipped CT scanner (SOMATOM Definition Edge, Siemens Healthineers, Forchheim, Germany) in split-filter mode at 120kVp and sequential-spiral mode at 80 and 140kVp. Additional DE scans were acquired at 80 and 140kVp (tin filter) with a dual-source CT scanner (SOMATOM Definition FLASH, Siemens Healthineers). Scans were performed with a CTDIvol of 7.3mGy in all protocols. Urinary stone categorization was based on dual energy ratio (DER) using an automated 3D segmentation. As reference standard, infrared spectroscopy was used to determine urinary stone composition. Results: All three DECT techniques significantly differentiated between uric acid and calcium stones by attenuation values and DERs (p < 0.001 for all). Split-filter DECT provided higher DERs for uric acid stones, when compared with dual-source and sequential-spiral DECT, and lower DERs for calcified stones when compared with dual-source DECT (p < 0.001 for both), leading to a decreased accuracy for material differentiation. Conclusion: Split-filter DECT, sequential-spiral DECT and dual-source DECT all allow for the acquisition of DER to classify urinary stones. Advances in knowledge: Split-filter DECT enables the differentiation between uric acid and calcium stones despite decreased spectral separation when compared with dual-source and dual-spiral DECT.

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Prospective prediction of the major component of urinary stone composition with dual-source dual-energy CT in vivo

Clinical Radiology ◽

10.1016/j.crad.2016.07.012 ◽

2016 ◽

Vol 71 (11) ◽

pp. 1178-1183 ◽

Cited By ~ 15

Author(s):

G.-M.-Y. Zhang ◽

H. Sun ◽

H.-D. Xue ◽

H. Xiao ◽

X.-B. Zhang ◽

...

Keyword(s):

Urinary Stone ◽

Dual Energy ◽

Dual Energy Ct ◽

Stone Composition ◽

Dual Source

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Threshold-dependent iodine imaging and spectral separation in a whole-body photon-counting CT system

European Radiology ◽

10.1007/s00330-021-07786-0 ◽

2021 ◽

Author(s):

S. Sawall ◽

L. Klein ◽

E. Wehrse ◽

L. T. Rotkopf ◽

C. Amato ◽

...

Keyword(s):

Image Quality ◽

Photon Counting ◽

Dual Energy ◽

Whole Body ◽

Dual Energy Ct ◽

Post Mortem ◽

Tube Voltage ◽

Spectral Separation ◽

Dual Source ◽

Noise Ratio

Abstract Objective To evaluate the dual-energy (DE) performance and spectral separation with respect to iodine imaging in a photon-counting CT (PCCT) and compare it to dual-source CT (DSCT) DE imaging. Methods A semi-anthropomorphic phantom extendable with fat rings equipped with iodine vials is measured in an experimental PCCT. The system comprises a PC detector with two energy bins (20 keV, T) and (T, eU) with threshold T and tube voltage U. Measurements using the PCCT are performed at all available tube voltages (80 to 140 kV) and threshold settings (50–90 keV). Further measurements are performed using a conventional energy-integrating DSCT. Spectral separation is quantified as the relative contrast media ratio R between the energy bins and low/high images. Image noise and dose-normalized contrast-to-noise ratio (CNRD) are evaluated in resulting iodine images. All results are validated in a post-mortem angiography study. Results R of the PC detector varies between 1.2 and 2.6 and increases with higher thresholds and higher tube voltage. Reference R of the EI DSCT is found as 2.20 on average overall phantoms. Maximum CNRD in iodine images is found for T = 60/65/70/70 keV for 80/100/120/140 kV. The highest CNRD of the PCCT is obtained using 140 kV and is decreasing with decreasing tube voltage. All results could be confirmed in the post-mortem angiography study. Conclusion Intrinsically acquired DE data are able to provide iodine images similar to conventional DSCT. However, PCCT thresholds should be chosen with respect to tube voltage to maximize image quality in retrospectively derived image sets. Key Points • Photon-counting CT allows for the computation of iodine images with similar quality compared to conventional dual-source dual-energy CT. • Thresholds should be chosen as a function of the tube voltage to maximize iodine contrast-to-noise ratio in derived image sets. • Image quality of retrospectively computed image sets can be maximized using optimized threshold settings.

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