Development and validation of an intrinsic landmark-based gating protocol applicable for functional and molecular ultrasound imaging
To implement a retrospective intrinsic landmark-based (ILB) gating protocol for contrast-enhanced ultrasound (CEUS) and to compare its efficiency to non-gated, manually gated and extrinsically gated CEUS.
CEUS of the liver was performed in healthy mice (n = 5) and in NEMO knockout mice with dysplastic livers (n = 5). In healthy animals, first-pass kinetics of non-specific microbubbles was recorded. Knockout mice were analysed regarding retention of VEGFR2-specific microbubbles. For retrospective gating, a landmark which showed respiratory movement was encircled as a region of interest (ROI). During inspiration, the signal intensity within the ROI altered, which served as gating signal. To evaluate the accuracy, non-gated, extrinsically gated and ILB-gated time-intensity curves were created. For each curve, descriptive parameters were calculated and compared to the gold standard (manual frame-by-frame gating).
No significant differences in the variation of ILB- and extrinsically gated time-intensity curves from the gold standard were observed. Non-gated data showed significantly higher variations. Also the variation of molecular ultrasound data was significantly lower for ILB-gated compared to non-gated data.
ILB gating is a robust and easy method to improve data accuracy in functional and molecular ultrasound liver imaging. This technique can presumably be translated to contrast-enhanced ultrasound examinations in humans.
• Quantitative analysis of the uptake of contrast agents during ultrasound is complex.
• Intrinsic landmark-based gating (ILB) offers a simple implementable method for motion correction.
• Results using ILB-gating are comparable to extrinsic gating using external biomonitoring devices.
• Functional and molecular imaging of mobile organs will benefit from ILB gating.
KeywordsGating Ultrasound Contrast enhanced Functional imaging Molecular imaging
Region of interest
Intrinsic landmark-based gating
Area under the curve
Vascular endothelial growth factor receptor type 2
This work was supported by the German Ministry for Education and Research (BMBF), project “Virtual Liver Consortium”, number 0315743 and by the German Research Foundation (DFG) SFB TRR57.