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Thứ Hai, 28 tháng 3, 2016

WHAT MEANS POINT-SHEAR WAVE ELASTOGRAPHY [p-SWE]?


Ultrasound based-elastographic techniques are classified in: strain techniques and shear
wave elastography  techniques. Three  types of elastographic  techniques are  included
in  the  last category: Transient Elastography, point Shear Wave Elastography  (pSWE)
and shear wave elastography (SWE) imaging (including 2D-SWE and 3D-SWE). 

In the pSWE category two techniques are included: Acoustic Radiation Force Impulse (ARFI) elastography and ElastPQ.



Elastographic Techniques Based on Shear Waves Generated by the Acoustic Beam

These techniques have the advantage of being integrated into ultrasound systems; thus, conventional sonography, which is advised every 6 to 12 months in patients with chronic liver disease, could also be performed. As of today, for the assessment of liver stiffness, these techniques are commercially available in high-end ultrasound systems made by Philips Healthcare (Bothell, WA; ElastPQ), Siemens Medical Solutions (Mountain View, CA; Virtual Touch Tissue Quantification [VTTQ]), and SuperSonic Imagine, SA (Aix-en-Provence, France; ShearWave Elastography [SWE]). These techniques generate shear waves inside the liver by using radiation force from a focused ultrasound beam. The shear waves are generated near the region of interest in the liver parenchyma and not on the surface of the body, as happens with external vibration devices. The ultrasound system monitors shear wave propagation using a Doppler-like ultrasound technique and measures its velocity. The shear wave velocity is displayed in meters per second or kilopascals through the Young modulus. Unlike transient elastography, the measurements are not limited by the presence of ascites because the ultrasound beam, which generates the shear waves, propagates through fluids. With the VTTQ and ElastPQ techniques, the readings of the shear wave speed are made by using a small sample box (usually 0.5 × 1 cm); thus, a quantitative estimate of liver stiffness at a single location is obtained (Figures 2 and 3). They have been categorized as point–shear wave elastography.The SWE technique is based on an ultrafast ultrasound imaging approach that allows detailed monitoring of the shear waves in a large area of liver parenchyma with real-time color-coded elasticity imaging inside a sample box, and the measurement is obtained by placing a region of interest inside the sample box (Figure 4). This technique is 2-dimensional elastography.27 In all of the studies that have assessed the accuracy of the different devices in staging liver fibrosis, right intercostal access has been used. The patient is examined in the dorsal decubitus position with the right arm elevated above the head for optimal intercostal access in a resting respiratory position. Measurements are performed at least 1.5 to 2.0 cm beneath the Glisson capsule to avoid reverberation artifacts. In case of physical conditions affecting the signal to-noise ratio, the Philips and Siemens devices do not give any measurement. With the SuperSonic Imagine device, a measurement fails when no/little signals are obtained in the sample box for all of the acquisitions.




Siemens Technique (VTTQ)
The first one available was the Siemens technique, which is commonly referred to as acoustic radiation force impulse in the literature, which is technically the same force that generates shear waves for all 3 available techniques. Moreover, the term acoustic radiation force impulse is rather generic and does not identify shear wave–based methods. In fact, acoustic radiation force impulse push pulses are also used in strain imaging of other organs, such as the breast and thyroid. In recent years, the diagnostic accuracy of the VTTQ technology for quantification of liver stiffness, mainly in patients with chronic hepatitis C, has been investigated in several studies and a meta-analysis. The technology has shown high interobserver agreement, with an intraclass correlation coefficient of 0.86. Operator training does not seem to be required.The cutoff values obtained in a large meta-analysis were 1.34, 1.55, and 1.80 m/s for significant fibrosis (METAVIR fibrosis score of F2 or greater), severe fibrosis (METAVIR fibrosis score of F3 or greater), and cirrhosis (METAVIR fibrosis score of F4), respectively. In this meta-analysis, which included patients with several etiologies of chronic liver disease, the diagnostic accuracy was comparable with that of transient elastography for the assessment of severe fibrosis, whereas higher performance of transient elastography was seen for significant fibrosis and liver cirrhosis. In a study by Rizzo et al, the technique was significantly more accurate than transient elastography for diagnosing significant and severe fibrosis, whereas this difference was only marginal for cirrhosis.


SuperSonic Imagine Technique (SWE)
The reproducibility of the SWE method is very high, with intraobserver intraclass correlation coefficients of 0.95 and 0.93 for an expert and a novice operator, respectively, and interobserver agreement of 0.88. As for conventional sonography, it is user dependent; thus, it is recommended that at least 50 supervised scans and measurements should be performed by a novice operator to obtain consistent measurements. Values obtained in a small series of healthy participants ranged from 4.92 kPa (1.28 m/s) to 5.39 kPa (1.34 m/s). In a pilot study conducted on 121 patients with chronic hepatitis C undergoing liver biopsy, the optimal cutoff values were 7.1 kPa (1.54 m/s) for significant fibrosis (METAVIR fibrosis score of F2 or greater), 8.7 kPa (1.70 m/s) for advanced fibrosis (METAVIR fibrosis score of F3 or greater), and 10.4 kPa (1.86 m/s) for cirrhosis (METAVIR fibrosis score of F4), and the technique was more accurate than transient elastography in assessing significant fibrosis. In another study, with respect to transient elastography, the technique showed higher accuracy in assessing mild and intermediate stages of fibrosis.

Philips Technique (ElastPQ)
The ElastPQ technique was the most recent to enter the market; thus, only a few studies have been published so far. With this technique, liver stiffness values in healthy volunteers have been reported to be less than 4.0 kPa (1.15 m/s). Ling et al found that men had higher values than women (3.8 ± 0.7 versus 3.5 ± 0.4 kPa, or 1.13 ± 0.48 versus 1.08 ± 0.37 m/s) and liver stiffness was comparable with different probe positions, examiners, and age groups. In a series that comprised 88 patients with chronic viral hepatitis and 33 healthy volunteers, the technique compared favorably with transient elastography in staging liver fibrosis, and healthy volunteers showed significantly lower values than patients with nonsignificant fibrosis.
 REFERENCES:


Bamber J, Cosgrove D, Dietrich CF, et al. : EFSUMB guidelines and recommendations on the clinical use of ultrasound elastography, part 1: basic principles and technology. Ultraschall Med 2013; 34:169–184.

Ferraioli et al: Shear Wave Elastography for Evaluation of Liver FibrosisJ Ultrasound Med 2014; 33:197–203 199

Thứ Bảy, 5 tháng 3, 2016

S W ELASTO into PLAQUE IMAGING from E C R 2016

ELASTOGRAPHY OFFERS NEW INSIGHTS INTO PLAQUE IMAGING




ELASTOGRAPHY OFFERS NEW INSIGHTS INTO PLAQUE IMAGING

Elastography has been used for many years to differentiate malignant from benign lesions, especially in the breast or liver. Experience in carotid artery disease is limited, but recent studies have shown that elastography may help to stratify plaque and reduce the risk of unnecessary surgery, as a Greek expert will show during a New Horizons session today at the ECR.
Stroke is one of the leading causes of death in developed countries; one third of cases are fatal and survival can come with considerable disabilities. In Europe alone, experts estimate that there are one million new ischaemic strokes per year and they expect this number to rise by 12% by 2020, as the population ages1. A wide spectrum of carotid artery diseases can lead to stroke, but atherosclerosis accounts for a significant percentage – about 20 to 30% of cases. Stenosis is typically a cause for atherosclerosis and is now being measured using ultrasound in symptomatic patients, who are usually treated with atherectomy. But it is not so clear how asymptomatic patients should be managed, according to Dr. Nikos Liasis, medical director of Affidea Greece, a pan-European medical service provider specialising in diagnostics investigations, clinical laboratories and cancer treatment services. “Despite many randomised clinical trials, there is a surprising lack of consensus regarding the treatment of asymptomatic patients,” he said ahead of his presentation during the session today. There is widespread agreement among physicians that many procedures are probably being performed with risks that are higher than the risk of the actual indications. “Ninety-two per cent of all atherectomies in the U.S. are undertaken in asymptomatic patients. On average, we operate on 16 patients to prevent one stroke in just five years, so we perform surgery on 15 people who may not need it, which is quite a high risk,” he said. The degree of stenosis is not the only predictive parameter for myocardial infarction or stroke. Therefore it has become crucial to be able to understand and stratify plaque morphology. The majority of myocardial infarctions and strokes are actually caused by plaque rupture. Thanks to histological findings, physicians know that unstable, vulnerable plaques, which are prone to rupture and distal embolisation, are those with a large lipid core and intraplaque haemorrhage. Inflammation is also a high risk factor for plaque rupture. Researchers have tried to establish whether it would be suitable to use ultrasound in everyday clinical practice to stratify plaque morphology, but the results combined with histopathological findings were poor. Liasis and his team at Affidea Greece, together with the University of Athens Medical School and the National Technical University of Athens, decided to conduct a prospective study in order to determine the contribution of ultrasound elastography to the description of plaque morphology. “Ultrasound elastography is based on the principle that so tissue deforms more than hard tissue. So plaques that are hard and stable deform less than so, vulnerable plaques,” he said. So far the few available papers on the topic focused on either shear wave or strain elastography. In his study, Liasis has compared both techniques against histopathological findings and he will present his results today. He estimates that the potential of both techniques for stratifying plaque is significant, and that they may be complementary in many ways as they offer information that is not accessible through B mode or Doppler flow and other US techniques. “Elastography enables the detection of the fibrous cap, the thickness or thinness of which is an indication of plaque instability, but it remains challenging to spot with traditional ultrasound. It also provides information about plaque smoothness and more accurate information on what is outside of the plaque. We have all the features that are characteristics of plaque morphology and which make plaque unstable,” he said. Elastography offers other benefits to consider for daily practice; it is radiation free, accessible and widely available. Furthermore, it does not require any patient preparation and the costs are low. Examination times are short compared with MRI and, unlike CT, there are no allergy risks linked to contrast agents use. However a number of technical limitations remain to be overcome and reproducibility is still challenging. “When plaque is calcified, we are not able to describe it because of the acoustic shadow. Our biggest disadvantage is subjectivity. Reproducibility is still an issue, but using appropriate examination protocols may help,” Liasis said. It will also be necessary to adapt the technique, which has been developed for lesions in superficial organs, to small pulsating vessels. “We need more prospective studies to evaluate its potential. US elastography in carotid plaque imaging is only a few years old. But our research is very promising to describe plaque,” he concluded.


1 Data gathered by Brainomix, Oxford University h‑ps://ec.europa.eu/easme/en/ sme/4065/brainomix-limited BY MÉLISANDE ROUGER 

Thứ Năm, 3 tháng 3, 2016

ARFI CÁC TUYẾN BỌT VÀ TUYẾN GIÁP ở MEDIC CENTER

ARFI CÁC TUYẾN BỌT và TUYẾN GIÁP ở MEDIC CENTER
  

Gần đây siêu âm đàn hồi bắt đầu được áp dụng vào lâm sàng để khảo sát u, bệnh tự miễn và bệnh nhiễm trùng của tuyến giáp và các tuyến bọt.


Những khảo sát riêng lẽ về siêu âm đàn hồi của  tuyến giáp và các tuyến bọt ghi nhận không có khác biệt theo tuổi và phái tính ở người trưởng thành. Tuy nhiên khảo sát siêu âm đàn hồi tuyến giáp và các tuyến bọt trong điều kiện bình thường và khảo sát  cùng lúc và trên cùng người được khám thì chưa có thông tin.

 Chúng tôi có ý định:


1/ tìm tương quan độ sinh echo của tuyến giáp và các tuyến bọt.
2/ tìm khác biệt giữa sinh echo tuyến giáp và tuyến mang tai trên cùng cá thể.

3/ định lượng độ đàn hồi tuyến giáp và các tuyến bọt .

Qua khảo sát 68 [34 nam, 34 nữ] cá nhân cùng lúc tuyến giáp và các tuyến bọt trong tình trạng khỏe mạnh, chúng tôi có kết quả như sau :


Giá trị trung bình vận tốc của sóng biến dạng ở mô tuyến giáp là = 1,58 ± 0,17m/s [ở nghiên cứu của NPB Quân và cs là:1,47 ± 0,41 m/s. Không có sự khác biệt vận tốc này với nhóm tuổi, nhưng có khác biệt với giới (p nhỏ hơn 0,05)].

Giá trị trung bình vận tốc của sóng biến dạng ở mô tuyến dưới hàm bình thường là 1,47± 0,015m/s [ ở nghiên cứu của AF Badea là =1,82 ± 0,41m/s cho cả 2 tuyến P và T].

Giá trị trung bình vận tốc của sóng biến dạng ở mô tuyến mang tai bình thường là 1,42 ± 0,015m/s  so với 1,54 ± 0,6 m/s ở nghiên cứu của I.Badea].

Khác biệt về độ đàn hồi tuyến giáp bình thường và các tuyến mang tai và dưới hàm không có ý nghĩa thống kê ( p nhỏ hơn 0,0001).




Tài liệu tham khảo chính:

Nguyễn Phước Bảo Quân, Nguyễn Hữu Thịnh: Bước đầu nghiên cứu siêu âm đàn hồi mô tuyến giáp ở người bình thường bằng phương pháp tạo hình và đo vận tốc sóng biến dạng qua kỹ thuật ARFI

Alexandru Florin Badea, Attila Tamas Szora, Elisabeta Ciuleanu, Ioana Chioreanu, Grigore Băciuţ, Monica Lupşor Platon, Radu Badea: ARFI quantitative elastography of the submandibular glands. Normal
measurements and the diagnosis value of the method in radiation submaxillitis.


Iulia Badea, Attila Tamas-Szora, Ioana Chiorean, Maria Crisan, Elisabeta Ciuleanu, Grigore Baciut, Mindra Badea: Acoustic Radiation Force Impulse quantitative elastography: a new  noninvasive technique for the evaluation of parotid glands.  A preliminary study in controls and in patients with irradiated nasopharyngeal carcinoma.