Vibration-controlled transient elastography for noninvasive evaluation of liver steatosis.

BACKGROUND: Nonalcoholic fatty liver disease (NAFLD) refers to a large spectrum of liver disorders and is the most common cause of metabolic liver disease. The current gold standard for diagnosing NAFLD is liver biopsy, which can lead to severe complications. PURPOSE: Among the noninvasive diagnostic options, we chose to use a FibroScan and developed an algorithm applying the Voigt rheological model to assess the viscoelastic properties of the liver and evaluate its performance for the diagnosis of steatosis. METHODS: Twenty-two healthy volunteers and 20 patients with steatosis were included. For each subject, we used a modified FibroScan, whose data had been processed by our algorithm to separate the two viscoelastic components, stiffness µ, and viscosity η. The liver elasticity µFibroscan measured by the FibroScan was also recorded. Mann-Whitney tests and receiver operating characteristics (ROCs) curve analyses were performed to compare the parameters between the two groups, and Pearson's correlation coefficients were used to assess the correlations between the parameters. RESULTS: We found a good correlation between η and µFibroscan (r = 0.75), and poor correlations between µ and both η and µFibroscan (r = 0.33 and r = 0.03, respectively). We also showed that η and µFibroscan were higher in patients with steatosis compared to healthy volunteers, with area under the ROCs (AUROC) curve at 0.814 and 0.891, respectively. Conversely, µ was not different between the two groups (AUROC = 0.557). CONCLUSIONS: Our novel method successfully separated the two viscoelastic properties of the liver, of which the parameter η is a sensitive indicator for steatosis.

Role of distal cerebral vasculature in vessel constriction after aneurysm treatment with flow diverter stents.

BACKGROUND: Treatment of intracranial aneurysms with flow diverter stent (FDS) procedures can lead to caliber changes of jailed vessels. The reason some branches remain unchanged and others are affected by narrowing remains unknown. OBJECTIVE: To investigate the influence of resistance to flow from distal vasculature on stent-induced hemodynamic modifications affecting bifurcating vessels. MATERIALS AND METHODS: Radiological images and demographic data were acquired for 142 aneurysms treated with a FDS. Vascular resistance was estimated from patient-specific anatomic data. Correlation analysis was used to identify correspondence between anatomic data and clinical outcome. Computational Fluid Dynamics was performed on a typical patient-specific model to evaluate the influence of FDS on flow. Relevant hemodynamic variables along the bifurcating vessels were quantitatively analyzed and validated with in vitro data obtained using power Doppler ultrasound. RESULTS: Statistical analysis showed a correlation between clinical outcome and FDS resistance to flow considering overall jailed vessel vascular resistance (r=0.5, P<0.001). Computational predictions of blood flow showed that hemodynamics is minimally affected by FDS treatment in the ophthalmic artery. CONCLUSIONS: Jailed vessels are affected by narrowing when resistance to flow from the FDS constitutes a larger proportion of the overall vessel resistance to flow. This knowledge may contribute to better understanding of intracranial hemodynamics after a FDS procedure and reinforce indications for flow diversion in the treatment of intracranial aneurysms.

Perfusion Quantification of Liver Metastases of Colorectal Cancer Treated with Anti-angiogenic-Based Therapy: Assessment of Intra- and Inter-observer Reproducibility of Parameters in Three Regions of Interest Outlining Lesions.

This study evaluated the reproducibility of dynamic contrast-enhanced ultrasound (DCEUS) parameters outlining liver metastases of colorectal cancer in 45 patients, before and after anti-angiogenic-based therapy. Tumor enhancement was quantified by drawing three regions of interest (ROIs): (i) outlining the tumor based on portal phase DCEUS images, (ii) in the hypo-enhanced center of the lesion and (iii) outlining the lesion using parametric imaging. Perfusion parameters were extracted from time-intensity curves. Another ROI was drawn in healthy liver parenchyma for normalization. Intra- and inter-observer reproducibility of these parameters was evaluated using intra-class correlation coefficients (ICCs). For the three ROIs, both intra- and inter-observer reproducibility were excellent (ICCs ≥0.9) for 50.8% absolute parameters and were moderate to good (0.7 ≤ ICC < 0.9) for 26.7% of them. In healthy liver parenchyma and for normalized parameters, reproducibility was moderate to excellent for 59.4% of intensity parameters and was low (ICC <0.7) for almost all temporal parameters. This study indicates that DCEUS is a reproducible tool for evaluating perfusion parameters.

One-step surgical removal of cutaneous melanoma with surgical margins based on preoperative ultrasound measurement of the thickness of the melanoma.

BACKGROUND: Surgical margins of melanoma vary from 5 mm to 1 or 2 cm depending on histology thickness (Breslow). This approach usually requires two surgical steps: excisional biopsy and further re-excision according to histology thickness. A previous systematic review showed that measuring melanoma thickness with high-resolution ultrasound imaging equipment correlates well with histological measurement of melanoma thickness. Therefore, we routinely determined tumour sonographic thickness in order to perform surgery as a single step. OBJECTIVES: To determine the proportion of patients who receive one-step surgery with adequate margins based on sonographic measurement of melanoma thickness and identify the reasons for differences between these two measurements. MATERIALS AND METHODS: A retrospective series of patients with melanoma, in which thickness was measured by ultrasound (20 MHz) from April 2007 to December 2015 prior to surgery. RESULTS: Ninety-nine melanomas were treated, of which 78 were removed in a single step with surgical margins based on sonometric thickness measurements; 71 of these (91%, 95% CI: 82-96) did not require re-excision, five had excessive margins, and two had insufficient margins. The correlation between the histometric and sonometric measurements was good; r=0.88. Significant absolute difference between sonometric and histometric measurements was associated with thickness, ulceration, and size of tumours, based on bivariate analysis. Thickness remained the only significant factor based on multivariate analysis. CONCLUSION: Measuring the thickness of melanoma with high-resolution ultrasound imaging equipment makes it possible to remove the melanoma in a single step with adequate margins in at least 82% of the cases in routine care.

High-frequency ultrasound imaging for cutaneous neurofibroma in patients with neurofibromatosis type I.

Neurofibromas (NFs) are benign tumours arising from a nerve sheath, which are present in nearly all patients with neurofibromatosis type 1 (NF1). High-frequency ultrasound (HFU) systems, using frequencies over 20 MHz, were developed to improve visualization of skin tumours by means of increased resolution. To describe NFs by using HFU in patients with NF1. Anonymized HFU (25-MHz) images of NFs were randomized. Initially, two dermatologist investigators, with experience in HFU imaging of the skin, together described the ultrasound images and established eight criteria for NFs. The same task was then repeated by two other dermatologists, also with experience in HFU imaging of the skin, independently, to establish inter-observer agreement. A total of 108 NFs in 29 patients were included. Superficial and subcutaneous NFs were hypoechoic with a round to spindle shape. Plexiform NFs were ill-defined, consisting of multiple hypoechoic linear zones. Good to excellent inter-observer agreement was found for six of the eight criteria (k>0.6). This is the first series describing HFU skin imaging of NFs in patients with NF1. Lateral extension that may correspond to involvement of an adjacent nerve seems to be specific to NFs.

Penetration depth with the XPS GreenLight laser assessed by contrast enhanced ultrasonography.

PURPOSE: The GreenLight laser is one of the main alternative treatments for benign prostatic hyperplasia (BPH). Ultrasonography with contrast (ECUS) is one of the main innovations in radiology that has led to the examination of tissue vascularity. The objective of the study was to measure the impact of photovaporization of the prostate (PVP) on the prostate gland with ECUS. PATIENTS AND METHODS: We conducted a pilot study to assess the impact of PVP on the prostate by using ECUS intraoperatively (ethical committee approval No. 2012-001451-39). Twelve patients undergoing PVP for symptomatic BPH were enrolled in this study after providing their informed consent. ECUS was performed just before and after PVP in the operating room and at 1 month postoperatively. RESULTS: Comparative analysis showed that after PVP, a nonvascularized area with an average thickness of 11.1 mm was observed beyond the operative cavity. The nonvascularized area was thinner at 1 month postoperatively and disappeared at 6 months for the six patients evaluated. This is the first study using contrast-enhanced ultrasonography to measure the impact of PVP on the prostate. Our study has the limitations of a pilot study with a small population and a short follow-up. Based on these results, we would advise beginners to take into account the necrosis thickness and to limit the depth of vaporization. CONCLUSIONS: Through the use of ECUS, our study demonstrated that a large area of necrosis is induced around the surgical cavity from the action of the GreenLight laser. Being aware of this phenomenon will certainly reduce the risk of complications induced by surgery.

Pharyngeal swallowing sound profile assessed after partial and total laryngectomy.

Recently, we described three components of a normal pharyngeal swallowing sound. The aim of the present study was to identify variations of these components using synchronized acoustic-radiological data in partially laryngectomized (PL) and totally laryngectomized (TL) patients before and after surgery. In this prospective study, from January 2003 to December 2006 we enrolled 14 patients in a PL group and 9 patients in a TL group. A fluoroscopy camera and a microphone were connected to a computer to obtain acoustic-radiological data (25 images/s). The subjects were asked to perform six deglutitions of 10 ml of barium suspension. The average durations of the sound variables were measured before and after surgery. The duration of the preoperative pharyngeal sound was 602 ms in the PL group and 562 ms in the TL group. It was significantly decreased after the TL (296 ms) and was increased after the PL (740 ms). A typical profile of the swallowing sound for each group was obtained. This study allowed us to describe the main variations of the pharyngeal swallowing sound induced by PL and TL. This noninvasive tool could be useful to assess postoperative swallowing function.

Temporal analysis of tissue displacement induced by a transient ultrasound radiation force.

One of the stress sources that can be used in dynamic elastography imaging methods is the acoustic radiation force. However, displacements of the medium induced by this stress field are generally not fully understood in terms of spatial distribution and temporal evolution. A model has been developed based on the elastodynamic Green's function describing the different acoustic waves generated by focused ultrasound. The function is composed of three terms: two far-field terms, which correspond to a purely longitudinal compression wave and a purely transverse shear wave, and a coupling near-field term which has a longitudinal component and a transverse component. For propagation distances in the shear wavelength range, the predominant term is the near field term. The displacement duration corresponds to the propagation duration of the shear wave between the farthest source point and the observation point. This time therefore depends on the source size and the local shear modulus of the tissue. Evolution of the displacement/time curve profile, which is directly linked to spatial and temporal source profiles, is computed at different radial distances, for different durations of force applications and different shear elastic coefficients. Experimental results performed with an optical interferometric method in a homogeneous tissue-mimicking phantom agreed with the theoretical profiles.

Spatial variation of acoustic parameters in human skin: an in vitro study between 22 and 45 MHz.

This study of spatial variance of acoustic parameters was performed on eight nonfrozen samples of female abdominal skin (women 46.5 +/- 12.2 years old), obtained during plastic surgery. Intra- and interindividual variations are discussed on the basis of estimations of three acoustic parameters (slope of attenuation- beta; integrated attenuation coefficient- IAC; integrated backscattering coefficient- IBC) and one texture parameter (based on two estimators of effective density of scatterers: alpha(2) and alpha(1/2)) as a function of surface area and depth of acquisition in the frequency range 22 to 45 MHz. Values of intraindividual variations varied from 7.1% for IAC to 23.2% for IBC, and significantly decreased at a ratio between 1.2 to 2.3 when the acquisition surface area was increased from 4 mm(2) to 1 cm(2). Interindividual variations were higher than intraindividual variations, and varied from 14.2% for alpha(1/2) to 51% for IBC. The mean values (+/- SD) for all specimens combined, estimated with a large number of independent radiofrequency (RF) lines (400) and for a surface area of exploration of 4 cm(2), were 1.06 +/- 0.17 dB cm(-1) MHz(-1) for beta, 135 +/- 37 dB cm(-1) for IAC, (3.7 +/- 1.9) x 10(-2) cm(-1) sr(-1) for IBC, 1.40 +/- 0.17 scatterers/resolution cell for alpha(2) and 1.32 +/- 0.27 scatterers/resolution cell for alpha(1/2). Finally, attenuation micro(f) and backscattering coefficient sigma(b)(f) were compared to published results for the same parameters measured in human skin.