Hepatic tumor diagnosis by analysing dense transport fields in contrast-enhanced ultrasound

International audienceDynamic contrast agent enhanced ultrasound (DCEUS) is considered as a safe, noninvasive, accurate, and economic tool for analysing blood perfusion of various organs [1]. Gas-filled mi-crobubble contrast agents are used as intravascular flow tracers. In this study, a new methodology is proposed to quantify the divergence (i.e sources, sinks), curl (i.e sheering) and amplitude in the apparent microbubble transports during the bolus arrival. The efficiency of proposed methodology is evaluated in-vivo, for the classification of focal nodular hyperplasia (FNH) and inflammatory hepatic adenomas (I-HCA)

A framework for continuous target tracking during MR-guided high intensity focused ultrasound thermal ablations in the abdomen

Scatterplot showing percentage changes in stroke volume index (ΔSVI, %) and functional hemodynamic markers, Stroke Volume Variation (SVV, %) Pulse Pressure Variation (PPV, %), with the three tested tidal volumes (V T ), 6, 12 and 18 ml/kg during intra-abdominal hypertension. Solid line shows regression line between variables. (PDF 56 kb

Multiple common garden experiments suggest lack of local adaptation in an invasive ornamental plant

Aims: Adaptive evolution along geographic gradients of climatic conditions is suggested to facilitate the spread of invasive plant species, leading to clinal variation among populations in the introduced range. We investigated whether adaptation to climate is also involved in the invasive spread of an ornamental shrub, Buddleja davidii, across western and central Europe. Material and Methods: We combined a common garden experiment, replicated in three climatically different central European regions, with reciprocal transplantation to quantify genetic differentiation in growth and reproductive traits of 20 invasive B. davidii populations. Additionally, we compared compensatory regrowth among populations after clipping of stems to simulate mechanical damage. Important findings: Our results do not provide evidence for clinal variation among invasive B. davidii populations: populations responded similarly to the different environments, and trait values were not correlated to climatic conditions or geographic coordinates of their home sites. Moreover, we did not detect differences in the compensatory ability of populations. We suppose that the invasive spread of B. davidii has been facilitated by phenotypic plasticity rather than by adaptation to climate, and that continent-wide shuffling of cultivars due to horticultural trade may have limited local adaptation so far

Hepatic tumor diagnosis by analysing dense transport fields in contrast-enhanced ultrasound

International audienceDynamic contrast agent enhanced ultrasound (DCEUS) is considered as a safe, noninvasive, accurate, and economic tool for analysing blood perfusion of various organs [1]. Gas-filled mi-crobubble contrast agents are used as intravascular flow tracers. In this study, a new methodology is proposed to quantify the divergence (i.e sources, sinks), curl (i.e sheering) and amplitude in the apparent microbubble transports during the bolus arrival. The efficiency of proposed methodology is evaluated in-vivo, for the classification of focal nodular hyperplasia (FNH) and inflammatory hepatic adenomas (I-HCA)

A framework for continuous target tracking during MR-guided high intensity focused ultrasound thermal ablations in the abdomen

International audienceBackground: During lengthy magnetic resonance-guided high intensity focused ultrasound (MRg-HIFU) thermal ablations in abdominal organs, the therapeutic work-flow is frequently hampered by various types of physiological motion occurring at different time-scales. If left un-addressed this can lead to an incomplete therapy and/or to tissue damage of organs-at-risk. While previous studies focus on correction schemes for displacements occurring at a particular time-scale within the work-flow of an MRg-HIFU therapy, in the current work we propose a motion correction strategy encompassing the entire work-flow.Methods: The proposed motion compensation framework consists of several linked components, each being adapted to motion occurring at a particular time-scale. While respiration was addressed through a fast correction scheme, long term organ drifts were compensated using a strategy operating on time-scales of several minutes. The framework relies on a periodic examination of the treated area via MR scans which are then registered to a reference scan acquired at the beginning of the therapy. The resulting displacements were used for both on-the-fly re-optimization of the interventional plan and to ensure the spatial fidelity between the different steps of the therapeutic work-flow. The approach was validated in three complementary studies: an experiment conducted on a phantom undergoing a known motion pattern, a study performed on the abdomen of 10 healthy volunteers and during 3 in-vivo MRg-HIFU ablations on porcine liver.Results: Results have shown that, during lengthy MRg-HIFU thermal therapies, the human liver and kidney can manifest displacements that exceed acceptable therapeutic margins. Also, it was demonstrated that the proposed framework is capable of providing motion estimates with sub-voxel precision and accuracy. Finally, the 3 successful animal studies demonstrate the compatibility of the proposed approach with the work-flow of an MRg-HIFU intervention under clinical conditions.Conclusions: In the current study we proposed an image-based motion compensation framework dedicated to MRg-HIFU thermal ablations in the abdomen, providing the possibility to re-optimize the therapy plan on-the-fly with the patient on the interventional table. Moreover, we have demonstrated that even under clinical conditions, the proposed approach is fully capable of continuously ensuring the spatial fidelity between the different phases of the therapeutic work-flow

Influence of different isoflurane anesthesia protocols on murine cerebral hemodynamics measured with pseudo-continuous arterial spin labeling

Arterial spin labeling (ASL)-MRI can noninvasively map cerebral blood flow (CBF) and cerebrovascular reactivity (CVR), potential biomarkers of cognitive impairment and dementia. Mouse models of disease are frequently used in translational MRI studies, which are commonly performed under anesthesia. Understanding the influence of the specific anesthesia protocol used on the measured parameters is important for accurate interpretation of hemodynamic studies with mice. Isoflurane is a frequently used anesthetic with vasodilative properties. Here, the influence of three distinct isoflurane protocols was studied with pseudo-continuous ASL in two different mouse strains. The first protocol was a free-breathing set-up with medium concentrations, the second a free-breathing set-up with low induction and maintenance concentrations, and the third a set-up with medium concentrations and mechanical ventilation. A protocol with the vasoconstrictive anesthetic medetomidine was used as a comparison. As expected, medium isoflurane anesthesia resulted in significantly higher CBF and lower CVR values than medetomidine (median whole-brain CBF of 157.7 vs 84.4 mL/100 g/min and CVR of 0.54 vs 51.7% in C57BL/6 J mice). The other two isoflurane protocols lowered the CBF and increased the CVR values compared with medium isoflurane anesthesia, without obvious differences between them (median whole-brain CBF of 138.9 vs 131.7 mL/100 g/min and CVR of 10.0 vs 9.6%, in C57BL/6 J mice). Furthermore, CVR was shown to be dependent on baseline CBF, regardless of the anesthesia protocol used