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Thứ Bảy, 29 tháng 12, 2012

Carotid Artery Stiffness Using Ultrasound Radiofrequency Data Technology


Evaluation of Carotid Artery Stiffness in Obese Children Using Ultrasound Radiofrequency Data Technology

Ye Jin,  Yaqing Chen, Qingya Tang, Mingbo Xue, Wenying Li, and Jun Jiang

 

Abstract

Objectives—The goals of this study were to investigate the difference in carotid arterial stiffness in obese children compared to healthy children and to study the correlation between carotid arterial stiffness parameters and obesity using ultrasound (US) radiofrequency (RF) data technology.

Methods—Carotid artery stiffness parameters, including the compliance coefficient, stiffness index, and pulse wave velocity, were evaluated in 71 obese patients and 47 healthy controls with US RF data technology. In addition, all participants were evaluated for fat thickness in the paraumbilical abdominal wall and fatty liver using abdominal US.

Results—Compared to the control group, the blood pressure (BP), body mass index (BMI), fat thickness in the paraumbilical abdominal wall, presence of fatty liver, and carotid stiffness parameters (stiffness index and pulse wave velocity) were significantly higher in the obese group, whereas the compliance coefficient was significantly lower in the obese group. Furthermore, the pulse wave velocity was weakly positively correlated with the BMI, systolic BP, diastolic BP, and paraumbilical abdominal wall fat thickness, whereas the compliance coefficient was weakly negatively correlated with the systolic BP, BMI, and paraumbilical abdominal wall fat thickness. The presence of a fatty liver was moderately positively correlated with the BMI and weakly positively correlated with the pulse wave velocity.

Conclusions—Ultrasound RF data technology may be a sensitive noninvasive method that can be used to accurately and quantitatively detect the difference in carotid artery stiffness in obese children compared to healthy children. The detection of carotid functional abnormalities and nonalcoholic fatty liver disease in obese children should allow early therapeutic intervention, which may prevent or delay the development of atherosclerosis in adulthood.

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Ultrasound Examinations of the Common Carotid Artery

With the participants in the supine position, the bilateral carotid arteries were scanned from the top to down in the long axis. For longitudinal 2-dimensional US images of the carotid artery, the near and far arterial walls were displayed as two echogenic lines, and the adventitia and intima were separated by the hypoechoic media. The inner most layer (intima) was isoechoic, continuous, and linear. The far arterial wall appeared as a hyperechoic structure. Carotid artery stiffness was measured at the common carotid artery bifurcation level in the long-axis view. The examination site was selected 1.0 cm below the carotid sinus edge. The width of the probe objective frame was set at 1.4 to 1.5 cm.

The position and height of the probe frame were adjusted to adapt the carotid artery to the middle of the frame. The probe beam direction was adjusted to ensure that the sound beam was vertical to the anterior and posterior arterial walls to clearly show the intima and media in the anterior and posterior walls. During the examinations, the participants were asked to hold their breath just before the start of the RF data scan. This scan detects the distension wave, intended as the change in the diameter of the vessel during a cardiac cycle. The difference between the systolic and diastolic diameter values is hereby the distension, and it is the fundamental parameter measured by the quality arterial stiffness software. The wall-tracking feature was active during the scan (Figure 1; see the orange lines across the vessel wall and the green lines associated with wall distension on pulsing). The real distension represented by the green line movements was “amplified,” giving a fast estimation for the user regarding the vessel’s elastic properties and allowing adequate detection (green lines should be as continuous as possible). The distension waveform represented by the movement of the blue lines was displayed at the bottom of the image. The waveform height provided relative information on the shape to ensure that the scan was continuous without artifacts. The premium elaboration capabilities of the MyLab Gold platform allows very fast frame rate acquisition (≈480 Hz), which allows detection without any ambiguity for wall velocities up to 30 m/s (well above the normal 10 m/s). When the instrument displayed6 continuous and stable values (an SD of the measurement ≤20 μm), the image was fixed and stored immediately. The distension value (systolic – diastolic) was determined during each cardiac cycle, and the software calculated the average value of 6 cardiac cycles.

After the 3 BP measurements had been taken, the average of both systolic and diastolic BPs were calculated and entered manually into the quality arterial stiffness vascular calculation software. The average distension value and the brachial systolic and diastolic BPs were used by the software to generate the carotid stiffness parameters, assuming that the arterial pressure at the level of the brachial artery was the same as that at the level of the carotid artery.



The carotid stiffness parameters were presented in the worksheet report (Figure 2). The mean of 3 measurements along with the maximum value were included in the final report.
 
 

Thứ Sáu, 28 tháng 12, 2012

3D US for Uterine Anomalies: The Z Technique


 

We have reported on standardization of the display of the midcoronal plane of the uterus in 3D volumes in gynecology; this technique, termed the Z technique, should help reduce operator dependency and enhance the diagnostic accuracy of 3D sonography in everyday uses. Details of the Z technique are as follows:

Step 1. Place the reference/rotational point at the midlevel of the endometrial stripe in the sagittal plane (Figure 2).

Step 2. Use Z rotation to align the long axis of the endometrial stripe along the horizontal axis in the sagittal plane of the uterus (Figure 3).
 

Step 3. Place the reference/rotational point at the midlevel of the endometrial stripe in the transverse plane (Figure 4).
 
 

Step 4. Use Z rotation to align the endometrial stripe with the horizontal axis in the transverse plane of the uterus (Figure 5).

Step 5. After step 4, the midcoronal plane of the uterus will be displayed in plane C (Figure 5); apply the Z rotation on plane C to display the midcoronal plane in the traditional orientation (Figure 6).

 

Thứ Sáu, 21 tháng 12, 2012

SIÊU ÂM CHẨN ĐOÁN GÃY SƯỜN và SỤN SƯỜN


Abstract


Introduction


Rib fractures are the most common injuries resulting from blunt chest trauma. However, costal cartilage fractures are almost invisible on chest X-rays unless they involve calcified cartilage. The sensitivity of conventional radiography and computed tomography for detecting rib fractures is limited, especially in cases where rib cartilage is involved. Therefore, this study was designed to evaluate the sensitivities of chest wall ultrasonography, clinical findings, and radiography in the detection of costal cartilage fractures.

Materials and methods


A total of 93 patients presenting with a high clinical suspicion of rib or sternal fractures were recruited for radiological workup with posterior–anterior (PA) chest radiographs, oblique rib views, sternal views, computed tomography, and chest ultrasound between April 2008 and May 2010. There were 47 men and 46 women, and the mean age of the patients was 51.8 ± 15.9 years (range 17–78 years). These patients with minor blunt chest trauma showed no evidence of rib fractures on conventional radiography and computed tomography, and no evidence of other major fractures. Chondral rib fractures were detected by using ultrasonography on a 7.5-MHz linear transducer.

Results


Of the total 93 patients, 64 (68.8%) showed chondral rib fractures, whereas 29 (31.2%) did not. The mean number of chondral rib fracture sites detected in 64 patients was 1.8 ± 0.8 (range 1–5). Subperiosteal hematoma was the most common finding associated with costal cartilage fractures (n = 14, 15.0%), followed by sternal fracture (n = 9, 9.7%). However, subperiosteal hematoma was also noticed in 1 (1.1%) of the patients without costal cartilage fractures, and sternal fractures in 7 patients (7.5%).

Discussion


The results of this study suggest that ultrasonography may be a useful imaging method for detecting costal cartilage fractures overlooked on conventional radiographs and computed tomography in patients with minor blunt chest trauma. Early ultrasonographic evaluation can give more accurate information than clinical and radiologic evaluation in detecting costal cartilage fractures and sternal fractures that are overlooked on conventional radiography and computed tomography after minor blunt chest trauma.

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Ultrasound in revelation of chondral rib fracture and  bony rib fracture at an outpatient clinic : A Vietnamese experience

Le Thanh Liem, Nguyen Thien Hung, Le van Tai, Lu Minh Tan, Le Tu Phuc, Phan Thanh Hai

MEDIC MEDICAL CENTER, HCMC, Vietnam

Abstract:

OBJECTIVE:


To disclose chondral or bony rib fracture by ultrasound which are negative on X-ray film of minor blunt chest trauma patients.

METHODS:


A total of 42 patients suffering from minor blunt chest trauma without evidence of a rib fracture on chest X-ray film, were examined with a 9L4 MHz or 7.5 MHz linear transducer of ultrasound system (Siemens, Aloka). Statistical analysis was done to outline the ultrasound findings of these rib fractures.

RESULTS:


There were 50 (100.0%) patients showed chondral and bony rib lesions, whereas these 50 patients had no evidence of rib lesions on X-ray film. Fracture of the rib with a disruption of continuity of bony cortex near junction of chrondral and bony rib was the most common finding in 45 (90,0%) patients. Chondral rib fractures were in five (10,0% )patients. Chondral rib fracture appeared as disruption of cortex, small echogenic lines in chondral rib, and bruised chondral rib was a small deformation of chondral cortex and echogenic area at trauma site which was painful site. Bony rib fractures significantly occurred in trauma patients, and the duration of pain in patients with chondral rib fractures was significantly longer than that of patients with bony rib fractures.


CONCLUSIONS:


Ultrasonography is a useful imaging method in disclosing the rib fractures (chondral and bony rib fractures) which were negative on chest X-ray film in minor blunt chest trauma. However, chondral rib fractures significantly occur less than bony rib fractures and result in a longer duration of pain.


Chondral rib fracture by ox kicking for 4 days.



2 cases of bruised chondral rib by hitting with echogenic line.


A case of calcified chondral rib for 4 years by beating.



A bruised of chondral rib with echogenic area in costal cartilage (below image), but ARFI velocity value in out of  range (above image).


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Tại MEDIC, trong 6 tháng cuối năm 2012, có 5 ca gãy dập sụn sườn trong số 50 ca chấn thương nhẹ lồng ngực với gãy xương sườn (và thân xương ức). Ca gãy sụn sườn gần với lúc khám siêu âm là 4 ngày do bị bò đá, ca xa nhất, 4 năm. X-quang không thấy tổn thương ở 2 ca này và các ca còn lại (45 ca). Gãy xương sườn là tổn thương không liên tục của vỏ xương, thường gần chỗ nối sụn và xương, và có kèm theo máu tụ khu trú thành ngực quanh ổ gãy. Gãy sụn sườn ít gặp hơn với  đường viền sụn gián đoạn, hay các đường echo dày trong sụn sườn, trong khi dập sụn sườn có các vùng echo dày trong sụn và bao sụn biến dạng lỏm ở nơi va chạm.




Siêu âm phần mềm thành ngực là phương tiện khám có hiệu quả và phát hiện sớm các trường hợp gãy sụn sườn, xương sườn (và xương ức), góp phần chẩn đoán đầy đủ các trường hợp chấn thương ngực kín nghi có tổn thương xương và sụn sườn, mà các phương tiện khác như X-quang và CT có thể bỏ sót.

Thứ Bảy, 15 tháng 12, 2012

SIÊU ÂM TĨNH MẠCH CHỦ DƯỚI trong SỐC


Sonography has traditionally been used to assess anatomic abnormalities. However, its value in evaluating physiologic characteristics has recently been recognized, particularly in the care of patients in shock. As the use of point-of-care sonography grows in critical care and emergency medicine, noninvasive assessment of intravascular volume status is increasingly being used to guide therapy of the critically ill.

Although intravenous fluid is often the initial treatment in hypotensive patients, aggressive volume resuscitation may be detrimental in some patients and in certain types of shock. Accurate diagnosis of shock state can be challenging because physical findings of hypovolemic, distributive, cardiogenic, and obstructive shock often overlap. Pulmonary artery and central venous pressure catheters, which provide physiologic data such as cardiac output and right atrial pressure, are time-consuming, invasive, and carry considerable risks. Central venous pressure has long been used to guide fluid management; however, data suggest that in critically ill patients, central venous pressure may not correlate with the effective intravascular volume. Furthermore, invasive hemodynamic monitoring has not been shown to benefit patients.

Given the importance of determining intravascular volume in shock, a rapid bedside sonographic examination can be instrumental in guiding medical management of critically ill patients. Multiple sonographic protocols now exist for the evaluation of shock, dyspnea, and cardiac arrest.  This article will describe the use of sonography of the inferior vena cava (IVC) in the evaluation of patients in shock.


 



 
Physiology: IVC Parameters
The IVC is a compliant vessel that distends and collapses with pressure and volume changes. Although the absolute IVC size varies widely among healthy individuals and may not by itself be diagnostic, the maximal IVC diameter has been shown to be lower in patients with hypovolemia.5
A better indicator of intravascular volume is collapsibility of the IVC. As intrathoracic pressure decreases with inspiration, venous blood is pulled from the lower half of the body into the right atrium. This action causes a transient, but normal, decrease in the IVC diameter. With expiration, the IVC diameter increases and returns to its baseline. These changes are known as respirophasic variability. The IVC collapsibility index, also known as the caval index, is defined as the difference between the maximal (expiratory) and minimal (inspiratory) IVC diameters divided by the maximal diameter. The caval index is used in spontaneously breathing patients to estimate right atrial pressure.6,7 In patients with minimal respirophasic collapse, having the patient inspire forcefully, or sniff, will differentiate between patients with poor inspiratory effort and those with elevated right atrial pressure. The sniff method may provide more accurate estimation of volume status; however, measurements taken during normal respiration are reasonably accurate as well.8
Recent guidelines from the American Society of Echocardiography support the general use of IVC size and collapsibility in assessment of volume status.9 Studies have suggested the use of specific parameters for maximal IVC diameter and caval index to predict volume status.6,8 In one of these studies, using 2 cm as the cutoff for the maximal IVC diameter resulted in good sensitivity and specificity for predicting elevated right atrial pressure.8 A caval index greater than 50% suggests a low volume state,6 especially in combination with a small IVC diameter. Conversely, a low caval index with a large IVC diameter suggests a high volume state.
Inferior vena cava size does not predict right atrial pressure in patients receiving mechanical ventilation.10 Mechanical ventilation reverses the hemodynamics of venous return during the respiratory cycle. During positive pressure inspiration, intrathoracic pressure is increased, impeding blood flow from the IVC to the right atrium. During expiration, intrathoracic pressure is lower, and venous return increases. In a patient with normal right atrial pressure, this cyclic venous return produces minimal variation of the IVC size during the respiratory cycle. When a patient is volume depleted, however, the right atrium and IVC become more compliant, and the IVC size increases with positive pressure inspiration. Assessment of the IVC has been used in mechanically ventilated patients to predict whether fluid expansion is expected to increase the stroke volume and cardiac output. The variation of the IVC in positive pressure ventilation, known as the IVC distensibility index, is the difference between the maximum and minimum IVC diameters divided by the minimum diameter. In contrast to IVC collapsibility, which indicates volume status, the distensibility index has been used to assess preload dependence and predict fluid responsiveness such that the absence of respiratory variation suggests that volume expansion is unlikely to be effective.11,12 Fluid responsiveness is an emerging and important concept in critical care that seeks to avoid unnecessary fluid administration, which may expose the patient to risks of volume overload, when a fluid challenge is not expected to improve hemodynamics and organ perfusion.
Anatomy and Scanning Technique
A low-frequency phased array transducer (3.5–5 MHz) is used to evaluate the IVC, which lies in the retroperitoneum to the right of the aorta. It is differentiated by its thinner walls and respiratory flow variation. The IVC passes posterior to the liver and is joined by the hepatic veins before it enters the thoracic cavity and drains into the right atrium. There exists considerable variability in the literature regarding the location at which the IVC diameter should be measured. Most studies agree that the measurement should be distal to the junction with the right atrium and within 3 cm of that point.6,8,1214 Other studies measure the IVC at or near the junction with the hepatic veins.11,1520 A study comparing commonly measured locations found that respiratory variation of the IVC at the junction with the right atrium did not correlate with variation at sites distal to the hepatic veins.21 Guidelines from the American Society of Echocardiography recommend an assessment of the IVC just proximal to the hepatic veins, which lie approximately 0.5 to 3 cm from the right atrium.9
To image the IVC, the probe is placed in the subxiphoid 4-chamber position with the probe marker oriented laterally to identify the right ventricle and right atrium. As the probe is progressively aimed toward the spine, the convergence of the IVC with the right atrium will be seen. The IVC should be followed inferiorly, specifically looking for the confluence of the hepatic veins with the IVC (Figure 1). The IVC can also be evaluated in the long-axis plane. For this view, the probe is turned from a 4-chamber subxiphoid to a 2-chamber subxiphoid orientation, with the probe now in a longitudinal orientation (Figure 2). Although this view allows visualization of the IVC throughout the length of the hepatic segment, the true size of the IVC may be underestimated in the long axis due to a common error known as the cylinder tangent effect. This effect occurs when the ultrasound beam travels through the vessel longitudinally in an off-centered plane. One way to avoid underestimating the size of the IVC is to angle the probe laterally and medially until the greatest dimension is identified.
The diameter of the IVC should be measured perpendicular to the long axis of the IVC at end-expiration and end-inspiration. The finding of a small-diameter IVC with large inspiratory collapse (high caval index) correlates with low volume states. This phenomenon may be observed in hypovolemic and distributive shock states (Figures 3 and 4 and Videos 1 and 2). Conversely, a large IVC with minimal collapse (low caval index) suggests a high volume state such as cardiogenic or obstructive shock (Figures 5 and 6 and Videos 3 and 4). Movement of the diaphragm, especially during forceful inspiration or sniffing, may displace the IVC relative to the probe, making it difficult to obtain comparative measurements at the same location. In the short axis, the probe may need to be angled inferiorly during inspiration to locate the site measured at expiration. In the long axis, displacement of the IVC may require angling inferiorly and/or laterally (to avoid tangential measurement). In either orientation, it is recommended to observe the changes of the IVC through several respiratory cycles.
 
M-mode Doppler sonography of the IVC can be used to graphically document the absolute size and dynamic changes in the caliber of the vessel during the patient's respiratory cycle in both short and long axes (Figures 710). It should be noted, however, that M-mode sonography may introduce inaccurate measurements due to the displacement of the IVC relative to the probe during inspiration. Movement of the IVC out of the plane of the M-mode cursor may appear as vessel collapse on the M-mode tracing. It is therefore recommended that M-mode sonography be used after adequately visualizing IVC variability in the B-mode to avoid inaccurate estimation of vessel size and collapse.
Further studies are needed to define normal IVC parameters such as size, collapsibility, and distensibility (in mechanically ventilated patients). Until then, assessment of IVC collapsibility is useful in the critically ill patient whose caval index approaches the extremes. Additionally, caval sonography can be repeated during resuscitation to evaluate improvement of these parameters.
Evidence
Incorporation of a goal-directed sonographic protocol including assessment of the IVC has been shown to improve the accuracy of physician diagnosis in patients with undifferentiated hypotension.22 In a recent prospective study, point-of-care sonography evaluating cardiac contractility and IVC collapsibility in patients with suspected sepsis was shown to increase physician certainty and alter more than 50% of treatment plans.23 Inadequate dilatation of the IVC after a fluid challenge was more sensitive than blood pressure for identification of hypovolemia in trauma patients.24 Another study in trauma patients showed the value of bedside caval sonography in evaluation of fluid status and resuscitation of critically ill patients.25 A study in acutely dyspneic patients presenting to the emergency department showed that IVC sonography rapidly identifies patients with congestive heart failure and volume overload.26
Rather than relying on a single measurement of the IVC, it may be more useful to follow changes in vessel size and collapsibility over time in response to an intervention. Studies have shown a decrease in the IVC diameter and increased collapsibility after blood loss15 and fluid removal during hemodialysis.27 In hypotensive emergency patients, volume resuscitation was associated with increases in the IVC diameter and less inspiratory collapsibility.14 Just as a single blood pressure measurement is an incomplete representation of the hemodynamic status of a patient, sonography of the IVC should be repeated after interventions or changes in clinical parameters. Monitoring of the IVC diameter during resuscitation is an emerging area of research, and further studies are necessary to determine the exact parameters to interpret IVC size and collapsibility.
Pitfalls
The IVC should be followed to the junction with the right atrium to avoid misidentification with the aorta. Because a single long-axis view may be inaccurate, it is recommended to assess the IVC in both short and long axes. Inferior vena cava determinations should be made at or near the confluence with the hepatic veins. Measurements elsewhere may not reflect intravascular volume.
A dynamic evaluation of the degree of IVC collapse with inspiration may correlate better with the intravascular volume than a single static measurement of the vessel size. Inferior vena cava size does not predict right atrial pressure in patients receiving mechanical ventilation. Care should be taken to maintain adequate visualization of the IVC throughout the respiratory cycle because the probe and IVC may be displaced by diaphragmatic and abdominal wall movements. Overestimation of intravascular volume may occur in conditions that impede flow to the right heart, including valvular abnormalities, pulmonary hypertension, and heart failure.
Interpretation of caval physiology is hindered by conditions that restrict the physiologic variability of the IVC, such as liver cirrhosis and fibrosis,28 masses causing external compression, and elevated intra-abdominal pressure. Interpretation of the physiologic characteristics of the IVC should be done in context with the patient's clinical scenario and adjunctive data.
Conclusions
Determination of shock state in critically ill patients is challenging, but caval sonography may be a substitute for invasive hemodynamic monitoring. Assessment of the physiologic characteristics of the IVC provides a rapid distinction between low and high volume states and offers the clinician a rapid, noninvasive way to guide resuscitation in critically ill patients. In addition to caval sonography, focused echocardiography and lung sonography have been suggested by an increasing number of resuscitation sonography protocols to further evaluate patients in shock.

 

Thứ Ba, 11 tháng 12, 2012

ARFI for Nonalcoholic Fatty Liver


Abstract

PURPOSE:

To investigate the clinical usefulness of ultrasonography-based acoustic radiation force impulse (ARFI) elastography (ie, ARFI sonoelastography) in patients with a diagnosis of nonalcoholic fatty liver disease (NAFLD) and compare ARFI sonoelastography results with transient sonoelastography and serum fibrosis marker test results.

MATERIALS AND METHODS:

Written informed consent was obtained from all subjects, and the local ethics committee approved the study. Fifty-four patients with a liver biopsy-confirmed diagnosis of NAFLD (mean age, 50.6 years +/- 13.7) were examined. All patients with NAFLD and healthy volunteers underwent ARFI sonoelastography, transient sonoelastography, and serum liver fibrosis marker testing (hyaluronic acids, type IV collagen 7 S domain). Ten healthy volunteers underwent ARFI sonoelastography. ARFI sonoelastography results were compared with liver biopsy findings, the reference standard. ARFI sonoelastography findings were compared with liver biopsy, transient sonoelastography, and serum fibrosis marker test results. Student t testing was used for univariate comparisons; Kruskal-Wallis testing, for assessments involving more than two independent groups; and areas under the receiver operating characteristic curve (A(z)), to assess the sensitivity and specificity of ARFI sonoelastography for detection of stage 3 and stage 4 fibrosis.

RESULTS:

Median velocities in the patients with NAFLD were 1.040 m/sec for those with stage 0 fibrosis, 1.120 m/sec for those with stage 1, 1.130 m/sec for those with stage 2, 1.780 m/sec for those with stage 3, and 2.180 m/sec for those with stage 4. The A(z) for the diagnosis of hepatic fibrosis stages 3 or higher was 0.973 (optimal cutoff value, 1.77 m/sec; sensitivity, 100%; specificity, 91%), while that for the diagnosis of stage 4 fibrosis was 0.976 (optimal cutoff value, 1.90 m/sec; sensitivity, 100%; specificity, 96%). Significant correlations between median velocity measured by using ARFI sonoelastography and the following parameters were observed: liver stiffness measured with transient sonoelastography (r = 0.75, P < .0001), serum level of hyaluronic acid(r = 0.459, P = .0009), and serum level of type IV collagen 7 S domain (r = 0.445, P = .0015).

CONCLUSION:

There is a significant positive correlation between median velocity measured by using ARFI sonoelastography and severity of liver fibrosis in patients with NAFLD. The results of ARFI sonoelastography were similar to those of transient sonoelastography

 

Discussion

Our study results demonstrate a significant positive correlation between median ARFI sonoelastographic velocity and liver fibrosis severity in patients with NAFLD. NAFLD is now a common cause of chronic liver disease. Its incidence in adults and children is rapidly increasing because of ongoing epidemics of obesity and type 2 diabetes (21,22). Patients with NAFLD can be divided into two categories: those with simple steatosis and those with NASH at liver biopsy. However, liver biopsy is an invasive and expensive procedure and is associated with a relatively high risk of complications (7). The biopsy procedure results in pain in 25% of all patients (23), and the risk of severe complications has been reported to be 3.1 cases per 1000 procedures (24). Moreover, the accuracy of biopsy for assessing the severity of liver fibrosis remains questionable, and intra- and interobserver variations have been observed (8,9,2527). Furthermore, sampling errors are often reported, even in patients with NASH (28). Thus, a rapid and noninvasive method of detecting fibrosis in patients with NAFLD is of major clinical interest.

From an imaging viewpoint, we previously reported that transient sonoelastography can be used to measure fibrosis in patients with NAFLD (10,11). Recently, ARFI sonoelastography has been used to generate internal mechanical excitation noninvasively, and this method has attracted a great deal of attention for its use in the measurement of liver stiffness. Friedrich-Rust et al (29) compared ARFI imaging with both transient sonoelastography and serum fibrosis marker testing for the noninvasive assessment of liver fibrosis in patients with viral hepatitis. They reported that the results of US-based ARFI imaging for noninvasive measurement of liver fibrosis were comparable to those of transient sonoelastography and serum fibrosis marker testing.

To our knowledge, no investigators had previously evaluated the utility of ARFI sonoelastography for the assessment of liver fibrosis specifically in patients with NAFLD. Our results demonstrate that the median velocity measured by using ARFI sonoelastography increases as the fibrotic stage increases in these patients. The results also demonstrate a significant relationship between median ARFI sonoelastographic velocity and transient sonoelastographic liver stiffness measurement. Although we found a positive correlation between median ARFI sonoelastographic velocity and serum levels of liver fibrosis markers, the r values were relatively weak; thus, it is unlikely that this correlation can be used clinically.

The major advantages of transient sonoelastography and ARFI sonoelastography, as compared with liver biopsy, are that these techniques are painless, rapid, and have no associated complications and are, therefore, very easily accepted by patients. Moreover, ARFI sonoelastography can be integrated into a conventional US system by using conventional US probes and therefore can be performed during standard US examinations of the liver, which are routinely performed in patients with chronic liver disease.

We found that the optimal median ARFI velocity for the diagnosis of NASH with severe fibrosis (stages 3 and 4) was 1.77 m/sec. Thus, in the future, patients with median velocities of more than 1.77 m/sec should be closely followed up, because it is likely that they have NASH with severe fibrosis. On the other hand, there is a possibility that the patients with a low median velocity might have simple steatosis. Therefore, in the future, patients with a low median velocity measured by using ARFI might be spared from undergoing liver biopsy.

We also found that the median velocity in patients with simple steatosis was lower than that in healthy volunteers. Possible reasons for this observation include the hypothesis that steatosis makes the liver softer because of fat deposition in the liver parenchyma. Unlike viral hepatitis, NASH has two aspects: steatosis and fibrosis. Therefore, in patients with NAFLD, it may be difficult to distinguish between simple steatosis and NASH with mild fibrosis with use of ARFI sonoelastography, although it can be performed more conveniently than transient sonoelastography.

One limitation of our study was that we calculated our accuracy measurements on the basis of the population being studied; therefore, our results are optimized for this specific population and likely include overestimations of performance. Another limitation was the relatively small number of patients, particularly those with higher grades of liver fibrosis. Because of this, we may not have adequately assessed the biologic variability in the patients with higher grades of fibrosis. Selection bias was another limitation because in this study, we did not examine patients who had any clinical evidence of hepatic decompensation. Furthermore, the liver biopsies were performed up to 12 months before ARFI sonoelastography and transient sonoelastography. There is the possibility that the degrees of steatosis and fibrosis had changed for the period. In this study, the same person performed the ARFI sonoelastographic and transient sonoelastographic examinations; this was an advantage because the two examinations could be performed with the patient in the same position. However, it cannot be denied that knowledge of other examinations could have biased results. At present, we have no choice but to depend on liver biopsy for the diagnosis of NASH.

In conclusion, to our knowledge, this is the first study conducted to investigate the potential clinical usefulness of a US-based ARFI elastography technique as a noninvasive method of assessing liver fibrosis in patients with NAFLD. Further investigation is required to ensure that ARFI sonoelastographic measurements are useful diagnostic markers of NASH.

Advances in Knowledge

*          There is a stepwise increase in the median velocity measured by using acoustic radiation force impulse (ARFI) sonoelastography with increasing histologic severity of hepatic fibrosis in fatty liver disease.

*          The median velocity in patients with simple steatosis is lower than that in healthy volunteers.

*          There is a relationship between median velocity measured by using ARFI sonoelastography and liver stiffness measured by using transient sonoelastography.

Implications for Patient Care

*          ARFI sonoelastography can be performed during standard US examinations of the liver, which are routinely performed in patients with chronic liver disease.

*          ARFI sonoelastography is a rapid and noninvasive method of detecting fibrosis in patients with nonalcoholic fatty liver disease.

Thứ Sáu, 7 tháng 12, 2012

Shear Wave Elastography in the Diagnosis of Thyroid Nodules: Feasibility in the Case of Coexistent Chronic Autoimmune Hashimoto's Thyroiditis.


SUMMARY

 Objective ShearWave™ Elastography (SWE) is real-time, quantitative and user-independent technique, recently introduced in the diagnostic work-up of thyroid nodules. Hashimoto’s thyroiditis (HT), characterized by variable degrees of lymphocytic infiltration and fibrosis, might affect shear wave propagation. The aim of this study was to assess the feasibility of SWE in cytologically benign thyroid nodules within both Hashimoto’s and nonautoimmune thyroid glands. The effect of autoimmunity on the gland stiffness was also evaluated.

 Design longitudinal study in a single centre.

 Patients SWE was performed in 75 patients with a benign thyroid nodule at cytology: 33 with Hashimoto’s thyroiditis (HT group) and 42 with uni- or multi-nodular goitre, negative for thyroid autoimmunity (non-HT group).

 Results The elasticity index (EI) of the extra-nodular tissue was greater, though not statistically significant, in the HT than in the non-HT group (24·0 ± 10·5 kPa vs 20·8 ± 10·4 kPa; P = 0·206). However, the EI of extra-nodular tissue was related to the TPOAb titre in the HT group (P = 0·02) and was significantly higher in patients with HT receiving L-thyroxine than in the euthyroid subjects (P = 0·02). The EI of thyroid nodules was similar in HT and non-HT groups. In both groups, the stiffness of nodules was significantly higher than that of the embedding tissue.

 Conclusions Our data indicate that SWE correctly defines the elasticity of thyroid nodules independently from the coexistence of autoimmune thyroiditis, always being able to differentiate nodular tissue from the surrounding parenchyma. In HT, the stiffness of extra-nodular tissue increases in relation to both the thyroid antibody titre and the degree of impairment of thyroid function.




BÀN LUẬN
Dữ liệu của chúng tôi  cho thấy kỹ thuật sử dụng siêu âm đàn hồi sóng biến dạng [shear wave elastograpphy, SWE] này có thể  xác định một cách chính xác độ đàn hồi của các hạt giáp, độc lập với nền  tuyến giáp cứng như trong viêm giáp Hashimoto (HT). Một gradient độ cứng đã được quan sát thấy trong tất cả các bệnh nhân, với các hạt giáp là cứng hơn đáng kể  so với các mô xung quanh, cả trong HT và trong các nhóm không-HT.

Viêm giáp tự miễn mạn tính HT tự nó [per se]  và độ nặng của nó, theo đánh giá của hiệu giá TPOAb và cần có  liệu pháp thay thế với L-T4 cho suy giáp, làm tăng thêm chỉ số đàn hồi [elastic index, EI] nhu mô quanh hạt. Tuy nhiên, ngay cả trong viêm giáp Hashimoto, một gradient độ đàn hồi đáng kể được duy trì giữa các hạt lành tính và mô-ngoài-hạt, chỉ số EI của hạt luôn lớn hơn so với nhu mô tuyến giáp mà hạt nhúng vào. Trong chấp nhận và thống nhất với phát hiện này, thấy có  quan hệ trực tiếp giữa các chỉ số đàn hồi EI của mô quanh hạt  và chỉ số EI các hạt lành tính ở viêm giáp Hashimoto.
Siêu âm đàn hồi sóng biến dạng SWE là một công cụ mạnh mẽ cho việc chẩn đoán các hạt giáp ác tính, chỉ số EI của hạt ác tính cao hơn đáng kể so với hạt lành tính.Theo chúng tôi biết, đây là nghiên cứu  khảo sát đầu tiên ảnh hưởng của viêm giáp HT  trên tính năng đàn hồi hạt giáp. Cũng được biết rõ rằng viêm giáp tự miễn mạn tính HT, được đặc trưng bằng thâm nhiễm tế bào lympho  và xơ hóa, làm thay đổi siêu cấu trúc [ultrastructure] tuyến giáp  gây cứng mô tuyến. Trong bệnh to cực [acromegaly], một nguyên do đặc trưng khác gây  xơ hóa  tuyến giáp, siêu âm đàn hồi đã cho thấy là không ích lợi  trong việc dự đoán tính chất ác tính của các hạt giáp. Điều này do bệnh nhân bệnh to cực dường như có một tỷ lệ  hạt cứng lớn hơn, nhưng không phải ác tính trên mô bệnh học. Ở những bệnh nhân này, xơ hóa và kết quả là độ cứng có thể do tăng tổng hợp collagen và lắng đọng gây ra bởi GH và IGF1.  Mặc dù hạn chế bởi loạt bệnh nhân của chúng tôi không nhiêu, những phát hiện của nghiên cứu này cho thấy viêm giáp tự miễn mạn tính HT không làm giảm khả năng siêu âm đàn hồi  sóng biến dạng trong  đánh giá các hạt giáp ở viêm giáp tự miễn mạn tính HT.

Điều này có liên quan đặc biệt bởi vì: (i) HT ảnh hưởng đến ít nhất 5% dân số nói chung,  (ii) bệnh nhân với HT có nhiều khả năng để phát triển các hạt giáp, do, ít nhất là một phần, từ kích thích TSH mãn tính;  (iii) một số nghiên cứu cho thấy mối liên quan giữa HT và ung thư tuyến giáp loại nhú [papillary carcinoma];  và (iv) một tỷ lệ cao  các kết quả  FNAC đáng ngờ hoặc không xác định được báo cáo khi kiểm tra hạt trong viêm giáp tự miễn Hashimoto.  Theo quan điểm này, việc xác định độ đàn hồi chính xác trở nên quan trọng trong quy trình  chẩn đoán các  hạt trong viêm giáp tự miễn  Hashimoto.
Để  kết luận, dữ liệu của chúng tôi cho thấy siêu âm đàn hồi sóng biến dạng SWE xác định  chính xác độ đàn hồi của các hạt giáp độc lập với viêm tuyến giáp tự miễn mạn tính cùng tồn tại, luôn  có khả năng phân biệt mô hạt từ nhu mô xung quanh. Trong viêm giáp  HT, độ cứng  mô ngoài hạt tăng thêm  trong tương quan cả hiệu giá kháng thể tuyến giáp  [thyroid antibody] lẫn mức độ suy giảm chức năng tuyến giáp, cao hơn ở những bệnh nhân đòi hỏi phải điều trị  L-thyroxine.

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INTRODUCTION

Elastography is an evolving technique aimed at differentiating benign from malignant thyroid nodules. This technique allows in vivo estimation of the tissue mechanical properties using a conventional ultrasound (US) system with modified software. Similarly to palpation, the rationale of elastography is that a cancerous nodule is stiffer, with less elastic deformation compared with the surrounding thyroid tissue or a benign thyroid nodule. This issue is of particular interest because thyroid nodules are commonly encountered in clinical practice, being detected by US in 19–67% of randomly selected individuals.1,2 As only a minority of these are malignant (5–15%3,4), selecting the malignant ones for thyroid surgery represents a major clinical issue.

Elastosonography, and in particular real-time US-elastography (US-E), was recently investigated as a tool for stratifying the presurgical risk of malignancy in nodules with indeterminate or nondiagnostic cytology.5 Rago et al.6 evaluated tissue stiffness by US-E in a large group of patients with thyroid nodules who underwent surgery for compressive symptoms or suspicion of malignancy at fine-needle aspiration cytology (FNAC). US-E displayed a sensitivity of 97%, a specificity of 100%, a positive predictive value of 100% and a negative predictive value of 98%, independently from nodule size. Recently, the same approach was applied to patients bearing nodules with indeterminate or nondiagnostic cytology, confirming the association of nodular stiffness with malignancy.6 Although promising, static US-E is biased by several factors, such as poor reproducibility, inter-observer variability and lack of quantitative information.7–9 Furthermore, US-E was mainly evaluated in highly selected patients, excluding those with cystic nodules and nodules with eggshell calcification.10,11 As the estimation of elasticity is altered by the presence of a nearby hard area, this technique is not reliable in the study of multi-nodular goitres, which represent about 40% of all nodular thyroid glands.12

Shear Wave™ Elastography (SWE) is a new real-time imaging modality, which uses a linear US transducer operated with no added pressure. Transient pulses are used to generate propagating shear waves in the body, and elasticity is directly calculated by measuring the wave propagation speed. Currently, SWE is the only technique producing real-time quantitative information on selected areas of thyroid tissue.13 It is also claimed to be relatively operator-independent and reproducible. Sebag et al.14 investigated the efficiency of this technique in predicting malignancy in solitary or multiple thyroid nodules. Using a cut-off level of 65 kPa of elasticity index (EI), they could predict malignancy with a sensitivity of 85·2%, a specificity of 93·9% and a positive predictive value of 92·3%. However, the accuracy of SWE might be impaired in patients with acromegaly, in whom GH/IGF I-induced fibrosis has been reported to increase nodule hardness, as assessed by US-E, independently from the malignant nature of the lesion.15 A more common, potentially confounding condition, yet to be evaluated, is chronic autoimmune Hashimoto’s thyroiditis (HT) coexistent with thyroid nodules. At histology, HT is characterized by lymphocytic infiltration of the thyroid parenchyma associated with variable degrees of fibrosis. The characteristic US pattern of Hashimoto’s glands consists of an array of tiny hypoechoic nodules that may become confluent, interspersed with echogenic fibrous bands. These pathological changes might affect shear wave propagation, thus hampering the diagnostic potential of SWE in thyroid nodules. This issue is of particular interest for two reasons. First, an increased prevalence of thyroid cancer has been reported in patients with HT.16,17 Second, the diagnostic accuracy of FNAC may be diminished in nodules within a Hashimoto’s gland, resulting in a higher rate of indeterminate or suspicious cytological reports.18

To answer the question of whether SWE might be feasible in nodules associated with HT, we investigated a series of benign thyroid nodules at cytology, which were harboured either within a Hashimoto’s gland or within a nonautoimmune thyroid.

PATIENTS and METHODS

Patients

The study enrolled 33 patients with HT harbouring one or more thyroid nodules (HT group) and 42 patients with uni-nodular or multi-nodular goitre, who had tested negative for thyroid antibodies and had a normal echo pattern at US (non-HT group).19 Inclusion criteria were a previous FNAC indicating that the nodule was benign and the absence of a dominant cystic component within the nodule.

The diagnosis of HT was made in the presence of a positive test for thyroglobulin antibody (TgAb) and/or thyroid peroxidase (TPOAb) antibody, and a hypoechoic pattern of the thyroid at US. Fifty-four patients were euthyroid without therapy, and 14, all of them belonging to the HT group, were euthyroid on L-thyroxine (L-T4) therapy. In patients with HT, the indication of LT4 treatment was a diagnosis of subclinical or overt hypothyroidism. Another seven patients, all with nodular goitre, were on L-T4 TSH-suppressive treatment. In patients in L-T4 replacement therapy and L-T4 TSH-suppressive therapy, the duration of L-T4 treatment ranged from 12 to 156 months (median 36·0 months).

All patients gave their informed consent to participate in the study.

Cytopathological diagnosis

Selection of nodules for FNAC was made according to the current guidelines.20,21 FNAC was performed, under US guidance, by a skilled endocrinologist using a 23-gauge needle attached to a 5-ml syringe.


Shear Wave Elastography

After a preliminary US evaluation and a cytological diagnosis of a benign lesion, thyroid nodules were evaluated by SWE. Briefly, SWE generates a remote radiation force by focused ultrasonic beams, a patented technology called ‘Sonic Touch’. Several of these so-called pushing beams at increasing depths are transmitted to generate a quasi-plane shear wave frame that propagates throughout the whole imaging area. Then, an ultrafast echographic imaging sequence (Ultrafast Imaging System) is performed to acquire successive raw radiofrequency dots at a very high frame rate (up to 20,000 frames per second). From shear wave propagation speed, tissue elasticity can be derived based on Young’s modulus formula (E = σ/ε, where σ is stress and ε is strain). This results in a colour-coded image, blue representing softer tissue and red stiffer tissue. Quantitative information is delivered as EI expressed in kilo-Pascal (kPa).

Shear wave elastographic measurement was performed with the Aixplorer, developed by SuperSonic Imagine (Les Jardins de la Duranne, Aix en Provence, France).



RESULTS

Patients in the HT and non-HT groups were matched for age (Table 1). The calcitonin concentration was in the normal range in all patients, confirming the benign nature of the nodule.

Conventional US

Table 1 summarizes the main US features of evaluated nodules. In the HT group, the volumes of the thyroid and of the nodules were significantly lower than in the non-HT group. The main US features, which may suggest malignancy, such as hypoechogenicity, microcalcifications, absence of halo and increased vascularization were equally distributed in the HT and non-HT glands.

Shear Wave Elastography

 Effect of chronic autoimmune thyroiditis on the elasticity of extra-nodular thyroid parenchyma. The mean (±SD) EI of the extra-nodular tissue was higher in the HT than in the non-HT group, but the difference did not reach statistical significance (24·0 ± 10·5 kPa vs 20·8 ± 10·4 kPa; P = 0·2; Fig. 1). However, the severity of chronic autoimmune thyroiditis significantly affected the elasticity of extra-nodular thyroid parenchyma, as assessed by a significant direct relationship between the EI of extra-nodular tissue and the serum titre of TPOAb (P = 0·02). Moreover, the mean EI of the extra-nodular tissue was significantly higher in the 14 patients with HT who were on L-T4 substitution for hypothyroidism as compared with the 54 untreated euthyroid patients (27·3 ± 9·0 kPa vs 20·9 ± 10·4 kPa, respectively, P = 0·02).


Figure 1. Mean (±SD) elasticity index of extra-nodular thyroid parenchyma and of benign nodules in Hashimoto’s thyroiditis (HT) and non-HT groups of patients. 

 Effect of chronic autoimmune thyroiditis on the gradient of elasticity between thyroid nodules and extra-nodular tissue. The median EI was calculated for the whole cohort of patients, both for thyroid parenchyma (20·4 KPa) and for nodules (29·5 KPa). The percentage of patients having an EI of the thyroid parenchyma higher than the calculated median one did not differ in HT (51·3%) as compared with the non-HT group (48·7%). Similarly, HT and non-HT patients were equally distributed above and below the median value of elasticity measured in nodular tissue (46% and 54%, respectively).

The mean (±SD) EI of thyroid nodules did not significantly differ in the HT as compared with the non-HT group (Fig. 1). In the HT group, the EI of the extra-nodular tissue was significantly related to the EI of the thyroid nodules (r2 = 0·196, P = 0·01). This association was absent in the non-HT group. The stiffness of thyroid nodules was always higher than that of the embedding tissue in both the HT and non-HT groups, and the difference between the two regions of interest was statistically significant (Fig. 2).


Figure 2. Mean (SD) elasticity index of benign nodules and extra-nodular thyroid parenchyma in Hashimoto’s thyroiditis (HT) and non HT groups of patients. 

DISCUSSION

Our data using shear wave elastography confirm the ability of this technique to correctly define the elasticity of thyroid nodules, independent from the presence of a stiffer gland as observed in HT. A gradient of stiffness was observed in all patients, with thyroid nodules being significantly harder than the surrounding tissue, both in HT and in the non-HT groups.

Chronic autoimmune HT per se and its severity, as assessed by TPOAb titres and by the need of replacement therapy with L-T4 for hypothyroidism, increases the EI of extra-nodular parenchyma. However, even in Hashimoto’s glands, a significant elasticity gradient is maintained between benign nodules and the extra-nodular tissue, the EI of nodules always being greater than that of the embedding thyroid parenchyma. In agreement with this finding, a significant direct relation was observed between the EI of the extra-nodular tissue and that of the benign nodules in Hashimoto’s glands.

Shear wave elastography has been reported to be a powerful tool for the diagnosis of malignant thyroid nodules, the EI being significantly greater in malignant as compared with benign nodules.14 To the best of our knowledge, this is the first study investigating the influence of HT on the elastographic features of thyroid nodules. It is well established that chronic autoimmune HT, being characterized by lymphocytic infiltration and fibrosis, modifies thyroid ultrastructure resulting in a stiffer gland. In acromegaly, another condition characterized by fibrosis of the thyroid, elastosonography was found to be useless in predicting the malignant nature of thyroid nodules. This is because patients with acromegaly seem to have a greater prevalence of hard nodules, which are not malignant at cytopathological examination.15 In these patients, fibrosis and consequent stiffness are probably due to increased collagen synthesis and deposition induced by GH and IGF1.24 Although limited by the fact that our series of patients was not large, the findings of the present study indicate that chronic autoimmune HT does not impair the ability of shear wave elastography to evaluate thyroid nodules even in chronic autoimmune HT. This is of particular relevance because: (i) HT affects at least 5% of the general population;25 (ii) patients with HT are more likely to develop thyroid nodules, due, at least in part, to a chronic TSH stimulation;26 (iii) several studies indicate an association between HT and thyroid cancer of the papillary type;16,27–32 and (iv) a higher prevalence of suspicious or indeterminate FNAC reports was reported when examining nodules harboured within a Hashimoto’s gland.33 In view of these considerations, correctly defining elasticity becomes critically important in the diagnostic work-up of nodules within Hashimoto’s glands.

In conclusion, our data indicate that shear wave elastography correctly defines the elasticity of thyroid nodules independently from the coexistence of chronic autoimmune thyroiditis, always being able to differentiate nodular tissue from surrounding parenchyma. In HT glands, the stiffness of extra-nodular tissue increases in relation to both the thyroid antibody titre and the degree of thyroid function impairment, being higher in patients requiring L-thyroxine therapy.