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Chủ Nhật, 28 tháng 12, 2014

C A P based on TRANSIENT ELASTOGRAPHY for HEPATIC STEATOSIS









Discussion

Hepatic steatosis, particularly because of NAFLD, is common and increasing in prevalence. In some patients, steatosis may progress to NASH, cirrhosis and end-stage liver disease.[1, 4] In light of the growing burden of NAFLD and anticipated development of specific therapies, reliable noninvasive methods for grading steatosis are needed.[9] We have demonstrated that the CAP is correlated with steatosis independent of inflammation and fibrosis, and can be used to noninvasively identify steatosis with good performance. Specifically, for significant steatosis (≥10% of affected hepatocytes), the AUROC of the CAP was 0.81; a CAP threshold of 283 dB/m was 76% sensitive and 79% specific for this outcome. Similar findings were reported in a study of 615 patients with HCV in whom the CAP had an AUROC of 0.80.[27]A threshold of 222 dB/m was 76% sensitive and 71% specific in this cohort. However, our data are somewhat less optimistic than described by Sasso et al. in a study of 115 patients with various liver disorders.[15] In this study, the AUROC for significant steatosis was 0.91; a CAP cut-off of 238 dB/m was 91% sensitive and 81% specific. These discrepancies may relate to differences in the study populations including disease aetiologies, the prevalence of obesity and extent of subcutaneous adiposity, and the severity of steatosis, which may influence CAP performance because of spectrum bias.[10]For example, the mean BMI in our cohort was 32 kg/m2 and 65% of patients had significant steatosis. In the other studies, mean BMI was 24–25 kg/m2 and 31–58% had significant steatosis.[15, 27] Future studies in larger cohorts, including ideally an individual patient data meta-analysis, will be useful for refining the operating characteristics of the CAP, including the optimal cut-offs in different disorders. Our data suggests that the performance of the CAP did not differ substantially between conditions.







We also examined the diagnostic performance of the CAP for quantifying steatosis according to the NAS classification.[4] CAP performed well for identifying S1–S3 (≥5%) and S2–S3 (>33%) steatosis with AUROCs of 0.79 and 0.76 respectively. However, because the CAP was not significantly different between patients with S2 and S3 steatosis (Fig. 2), severe (>66%) steatosis was sub-optimally identified (AUROC 0.70). These findings were corroborated in our analysis evaluating the CAP's ability to discriminate individual steatosis grades, which overall, revealed reasonable performance (Obuchowski measure = 0.89). However, a problem with the CAP is that the optimal cut-offs identified for each outcome – based on the maximal sum of sensitivity and specificity – were similar (Table 2), which makes grading steatosis with this technology difficult. Similarly, although the CAP reliably differentiated steatosis at least 2 grades apart, the identification of single-grade differences was poor (Table 3). This limitation, which also applies to other surrogate markers of liver histology (e.g. serum fibrosis markers and FibroScan®) is in part because of the imprecision of the CAP, but also the limitations of liver biopsy. Indeed, in a study that evaluated sampling error of biopsy among 51 NAFLD patients who underwent dual pass biopsies, discordance in steatosis grading was observed in 22% of cases.[7] In 18% of patients, the difference in steatosis severity exceeded 20%. It is conceivable that the CAP actually provides a more accurate assessment of steatosis within the entire liver as it samples a volume ~100-times larger than biopsy.[15] Furthermore, the reliability and variability in the pathologic grading of steatosis, even by experts, is poor.[28–30] Steatosis evaluation can also be influenced by tissue fixation and staining methods.[31, 32] Therefore, although we included only high-quality biopsies and centralized histological grading by experts, we cannot exclude an 'imperfect gold standard bias'. Future CAP studies including more objective assessments of steatosis (e.g. computerized morphometry)[28] would be useful to investigate these issues.
Previous reports have shown higher rates of discordance in fibrosis staging using the FibroScan® in patients with highly variable LSMs.[22, 23] Therefore, we examined the impact of CAP variability – as assessed by IQR/MCAP – on the diagnostic performance of this tool. Although we did not observe significant differences in the AUROCs of the CAP for significant (≥10%) steatosis between patients with high and low IQR/M, highly variable measurements (IQR/MCAP ≥15) were less accurate for ≥5% steatosis in a post hoc analysis. These findings require confirmation. The AUROC for significant steatosis was higher among patients with no to minimal fibrosis (AUROC 0.89 vs. 0.72 with moderate to severe fibrosis), suggesting a potential role for the CAP as a screening tool in the general population. The reason for this novel finding [15, 27] remains unclear because the prevalence of significant steatosis was similar between groups (60–70%). Moreover, the CAP was not associated with fibrosis after adjustment for steatosis and inflammation. Additional studies in larger cohorts are necessary for confirmation and to examine other predictors of CAP performance.
Our study suggests that the CAP may be a worthwhile adjunct in the evaluation of patients with chronic liver disease. As LSM by FibroScan® is routine in many regions, an appealing aspect of the CAP is that it is provided automatically and immediately by the FibroScan® VCTE™ software in the same region of interest as LSM. Moreover, CAP measurement is operator-independent and requires no specific training. Another potential application of CAP is the exclusion of steatosis in donors for living-related liver transplantation, in whom steatosis increases the risk of primary graft non-function.[33] Evaluation of CAP in other clinical settings will be the focus of future investigation.
Other serum and imaging-based methods have been examined for the noninvasive assessment of steatosis. Although liver biochemistry is widely available and inexpensive, the sensitivity of these tests is sub-optimal. In our study, the AUROCs (95% CI) of ALT and GGT for significant steatosis were only 0.50 (0.40–0.60) and 0.56 (0.46–0.66) respectively (both P < 0.00005 vs. CAP). Several serum marker panels have also been proposed for quantifying steatosis. For example, the SteatoTest includes age, gender, BMI, cholesterol, triglycerides, glucose, ALT, GGT, bilirubin, haptoglobin, alpha-2-macroglobulin and apolipoprotein A1.[34] For steatosis ≥5%, its AUROC was 0.80 in a cohort of 811 patients with various liver disorders. The proprietary nature of this algorithm and delayed results are important limitations. A recently described nonproprietary panel, the FLI, includes triglycerides, GGT, BMI and waist circumference.[17] The FLI is associated with steatosis detected songraphically[17] and is an independent predictor of mortality.[18] Similarly, the HSI, which includes the ALT/AST ratio, BMI, gender and diabetes, is associated with the presence and severity of steatosis on ultrasound.[19] In our study, the CAP outperformed these indices for the primary outcome and most secondary outcomes although the small sample size may have rendered some analyses underpowered. Ultrasound is the most common imaging method for detecting steatosis, which is recognized by a diffuse increase in hepatic echogenicity.[12, 13] 

Limitations of ultrasound include its markedly reduced sensitivity for mild steatosis (under 30%),[35, 36] operator and machine-dependence, the inability to reliably quantify hepatic fat content,[12, 13, 35] and the potential for extensive fibrosis to increase liver echogenicity.[13] Although promising, other abdominal imaging techniques (e.g. CT, MRI and proton magnetic resonance spectroscopy), are not widely available, expensive, lack standardization, have controversial diagnostic performance, and in the case of CT, exposure to ionizing radiation.[12, 13]

Our study has several limitations. Most importantly, our study population was highly selected in that it included only patients with a BMI ≥28 kg/m2; moreover, a significant number of patients were excluded predominantly because of missing data. Therefore, the generalizability of our findings to other patient populations (e.g. a 'screening cohort' seen in primary care) requires confirmation. Second, our sample size was limited in part because of the difficulty of obtaining valid CAP measurements in obese patients using the FibroScan® M probe. Future studies are necessary to develop a CAP algorithm for the novel FibroScan® XL probe, which was designed for use in this population.[16] Second, because of a median delay of approximately 1 month between CAP measurement and biopsy, we cannot exclude changes in steatosis that may have influenced our findings. Third, we assessed only the diagnostic accuracy of CAP although additional properties including agreement, precision, and responsiveness deserve mention. Finally, our cohort included patients with numerous liver diseases in whom inflammation and fibrosis may be staged using different scoring systems. As these classifications are not interchangeable, this issue may have influenced our multivariate analyses.
In conclusion, the CAP is a promising tool for the noninvasive detection of hepatic steatosis. Advantages of the CAP include its simplicity, operator-independence and sensitivity to lesser degrees of steatosis than are detectable using other widely available imaging modalities. Moreover, the CAP provides an immediate assessment of steatosis simultaneously with LSM used to stage hepatic fibrosis. Future studies are necessary to validate our findings in larger cohorts to define optimal CAP thresholds and to develop a CAP algorithm for the FibroScan® XL probe that will facilitate measurement in a greater proportion of obese patients.

UNCOMPLICATED ACUTE DIVERCULITIS: BENEFITS of ULTRASOUND DIAGNOSIS








SWE in PLACENTAL DYSFUNCTION





Abstract

Objectives—The aim of this study was to determine whether shear wave elastography of the placenta differs between normal pregnancies and pregnancies complicated by preeclampsia between 20 and 23 weeks’ gestation.
Methods—A prospective study was performed with 204 consecutive singleton pregnancies that had routine anomaly scanning between 20 and 23 weeks’ gestation. One hundred twenty-nine of these patients were examined with shear wave elastography; 101 women who had clinically normal pregnancies with normal fetal biometric measurements and normal deliveries without any perinatal complications formed group A, and 28 women who had a clinical diagnosis of early-onset preeclampsia before anomaly scanning formed group B. Women with either posterior placentations (n = 63) or other obstetric disorders (n = 12) were excluded from the study.
Results—Shear wave elastographic values for group B were significantly higher than those for group A (P < .05). No statistically significant difference was found between the elasticity values measured at the center or edge of the placenta (P > .05).



Conclusions—Shear wave elastography differentiates between the placental elasticity of normal pregnancies and pregnancies complicated by preeclampsia when performed during the second trimester. As a new method for tissue characterization, shear wave elastography is useful for evaluation of placental function and can be used as a supplement to existing methods for prediction of preeclampsia.

METASTATIC CERVICAL LYMPH NODES on V T I [ARFI]



Abstract

Objectives—The purpose of this study was to investigate the clinical usefulness of acoustic radiation force impulse elastography for the differential diagnosis of cervical lymph nodes.
Methods—Virtual touch tissue imaging (Siemens Medical Solutions, Mountain View, CA) was analyzed in 81 patients (mean age, 46.6 years; range, 5–82 years) with 81 lymph nodes (45 metastatic nodes and 36 benign nodes).

Results—Most benign lymph nodes were slightly darker or the same in brightness compared with surrounding tissue, whereas most metastatic nodes were obviously darker. The mean area ratio of benign lymph nodes ± SD (1.05 ± 0.15) was statistically lower than the mean area ratio of metastatic lymph nodes (1.39 ± 0.20; P < 0.001). The area ration cutoff level for metastatic lymph nodes was estimated to be 1.16. With the use of a receiver operating characteristic curve with this cutoff value, the area ratio predicted malignancy with sensitivity of 91.1%, specificity of 83.3%, and an area under the curve of 0.925.

 


Conclusions—Acoustic radiation force impulse imaging is feasible for cervical lymph nodes. The Virtual Touch tissue imaging technique can complement conventional sonography, thereby making it easier to diagnose cervical lymph nodes.

Clinical Application of Musculoskeletal Ultrasound in Rheumatology in Taiwan


Yu-Fen Hsiao
Department of Internal Medicine, Chu Shang Show Chwan Memorial Hospital, Nantou, Taiwan
Ko-Jen Li
Department of Internal Medicine, National Taiwan University Hospital, Taipei, Taiwan

Diagnosis of rheumatic diseases is difficult due to diverse symptoms that can involve the bone, joints, muscles, tendons, blood vessels, or nerves. In the past, physicians made diagnoses based on history-taking, physical examinations, serological tests, and X-rays. However, difficulties in diagnosing rheumatic diseases arose from limitations in the sensitivity and specificity of serological tests and X-rays.
Magnetic resonance imaging (MRI) has a high sensitivity for detecting tiny inflammatory or destructive changes, which can help physicians in early diagnosis or in the monitoring of disease progression. However, MRI has a number of disadvantages, including its expense, time required, and its limited use in evaluating renal function, which hinder the use of MRI in routine practice. In contrast to MRI, musculoskeletal ultrasound (MSUS) has the advantage of being able to provide convenient, fast and real-time images for early diagnosis and routine follow-up [1]. In evaluations of soft-tissue lesions, MSUS and MRI are more sensitive than plain radiography and computed tomography. MSUS has the advantages of being non-radioactive, inexpensive, portable, and repeatable. It can provide high-resolution, power Doppler, real-time imaging of articular, periarticular and soft-tissue structures in the evaluation of rheumatologic disease. Furthermore, ultrasound-guided procedures allow for better assessment of target lesions with minimal injury to adjacent tissues such as nerves or blood vessels [2]. There is growing evidence to show that MSUS can play a more important role in the diagnosis and treatment of rheumatic diseases.
Spondyloarthropathies are composed of five diseases with similar rheumatic presentations, including ankylosing spondylitis, psoriatic arthritis, reactive arthritis, spondylitis associated with inflammatory bowel disease (IBD) and undifferentiated spondyloarthropathy. Enthesitis is one of the most common features of spondyloarthropathies. However, the diagnosis is difficult to make due to lack of clinical awareness and there being no standard method for evaluation in the past. MSUS is considered a good tool for evaluating enthesitis, with a high sensitivity and specificity. There are many sonographic quantitative scoring systems for enthesitis evaluation, including the Glasgow Ultrasound Enthesitis Scoring System (GUESS), Mander Enthesitis Index (MEI), and the Madrid Sonographic Enthesitis Index (MASEI) [[3], [4], [5]]. In this issue of the Journal of Medical Ultrasound, Hsiao et al report a pilot study using GUESS to evaluate enthesitis in patients with and without IBD [6]. Subclinical enthesopathy with higher GUESS scores were found in patients with IBD. Thus, musculoskeletal involvement in IBD should not be overlooked by simple history-taking or clinical examinations. Further long-term MSUS follow-up is needed in IBD patients.
MSUS is more sensitive than plain radiography in the detection of synovial hyperplasia, effusion, bony erosions, and inflammation with emerging power Doppler signals, allowing earlier diagnosis of progressive rheumatoid arthritis. This is important as it is now possible to aim for low disease activity in rheumatoid arthritis in this era of biological agents. MSUS can be another tool to guide treatment other than clinical symptoms, laboratory examinations and radiography. Ultrasound is becoming a useful tool that is integrated into clinical practice and linked to decision-making [7].
According to Raftery et al, MSUS performed by a rheumatologist aided diagnosis of synovial and tendon inflammation and guided injections, while MSUS performed by a radiologist aided diagnosis of structural pathology [8]. It is essential for rheumatologists to acquire ultrasonography skills in order to improve patient care [9]. The accuracy of ultrasound examinations is operator-dependent and the technical capabilities of MSUS are a critical issue in the extensive application of MSUS in rheumatology practice. In this issue of the Journal of Medical Ultrasound, Chen et al present a study of MSUS and MRI in detecting full-thickness rotator cuff tears [10]. With arthroscopic findings as the gold standard, MSUS performed by a qualified rheumatologist has good sensitivity and accuracy in detecting full-thickness rotator cuff tears, with good agreement with MRI.
In Taiwan, MSUS was introduced to rheumatology 20 years ago. However, there remain barriers to the more widespread use of MSUS in daily practice because of equipment costs, heavy clinical load, long learning curve and certification requirements. The training programs on the use of MSUS in rheumatology were developed by the Taiwan Rheumatology Association (TRA) only in the last 7 years. In 2013, the director of the TRA, Professor Der-Yuan Chen, focused on integrating the training and certifications in the TRA and the Chinese Taipei Society of Ultrasound in Medicine (SUMROC). Due to his efforts, the MSUS certification program for rheumatologists was organized this year. We believe that more and more Taiwan rheumatologists will join the training programs and MSUS will become a useful tool in the daily practice of every rheumatologist.

© 2014 Published by Elsevier Inc.

Steatosis Using Controlled Attenuation Parameter

Quantitative Assessment of Steatosis in Liver Tissue Using Controlled Attenuation Parameter
Cheng-Kun Wu, Tsung-Hui Hu
Division of Hepato-Gastroenterology, Department of Internal Medicine, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan
Hepatic steatosis (or fatty liver) is a common histological finding in patients with metabolic syndrome, alcoholic hepatitis, or hepatitis C, or those who receive certain drugs such as steroids and amiodarone. The complication of hepatic steatosis in patients with other liver diseases such as hepatitis C leads to the progression of liver fibrosis and poor treatment response. Therefore, an accurate evaluation of hepatic steatosis is essential for clinical decision making and prognosis assessment. Abdominal ultrasonography is a highly accurate and commonly used tool for diagnosing fatty liver. The diagnostic criteria of this technique include the following: brightness contrast between the liver parenchyma and the right renal cortex; masking of the portal vein, hepatic vein, and gallbladder wall; and ultrasound attenuation in deep liver tissues. However, ultrasound has low sensitivity in diagnosing mild steatosis and is prone to the operator’s subjective opinion. Although computed tomography and magnetic resonance imaging play a certain role in diagnosing fatty liver, these techniques are limited by availability and radiation exposure. Computed tomography is suitable only for detecting steatosis with >30% fat accumulation. Although magnetic resonance imaging offers outstanding accuracy, it is less suited for regular screening for fatty liver because it is both complex and expensive. Currently, the gold standard for steatosis assessment is liver biopsy; however, it is invasive, costly, prone to sampling bias, and risks potential serious complications. Furthermore, in the clinical setting, repeated biopsies are not a feasible method for following up on the status of steatosis. To overcome these limitations, Fibroscan (® 502 Touch by Echosens (Paris, France)), a technology based on liver fibrosis, has been developed.
The measurement of ultrasound attenuation during transmission through biological tissues has multiple useful biomedical applications. Ultrasound attenuation, the energy loss when the sound wave passes through a medium, depends on: (1) the frequency of the ultrasound; and (2) the nature of the transmission medium. The standard ultrasound attenuation rates at 3.5 MHz in different human tissues are as follows: 175–630 dB/m in fat, 40–70 dB/m in liver, 315–385 dB/m in tendons, and 105–280 dB/m in soft tissues. Based on ultrasound attenuation principles and the effect of fat on attenuation, researchers developed a new method, named controlled attenuation parameter (CAP), to quantify the degree of steatosis in liver tissue [1]. This technology uses Vibration-Controlled Transient Elastography (VCTE), which emits ultrasound at a fixed center frequency of 3.5 MHz and traces the velocity of shear waves to measure liver firmness. In addition, CAP uses the frequency data collected from the same examination area to assess the total attenuation of the ultrasound signal, including the paths from and to the probe. The result is expressed in dB/m, ranging from 100 dB/m to 400 dB/m (a higher value represents a larger proportion of steatosis). The CAP technology is noninvasive, is easy to use, and provides real-time surveillance. Furthermore, because the procedure can monitor an area 100 times that of liver biopsy, it eliminates operator sampling bias. Fibroscan allows the clinician to evaluate and quantify steatosis while assessing fibrosis, thus facilitating post-treatment comparison through follow ups.
Myers et al [2] analyzed 153 patients who received liver biopsy and CAP-coupled Fibroscan simultaneously. They found that patients with a higher degree and proportion of steatosis confirmed by liver biopsy also had higher CAP scores. A recent large-scale study (comprising 5323 tests) found CAP scores associated with clinical disease presentation and blood test values. Researchers found that patients with fatty liver-triggering conditions such as metabolic syndrome, alcoholism, hypertriglyceridemia, large abdominal circumference, diabetes or hypertension, and high body mass index (>30 kg/m2) had increased CAP values accordingly. CAP areas under the receiver operating characteristic curve were 0.79 [95% confidence interval (CI), 0.74–0.84; p < 0.001], 0.84 (95% CI, 0.80–0.88, p < 0.001), and 0.84 (95% CI, 0.80–0.88, p < 0.001) in patients with >10%, >33%, and >66% steatosis, respectively [3]. Other clinical studies also showed CAP examination to be free from operator bias. In a prospective study, two independent operators performed CAP examinations on 118 patients. The results revealed good consistency between the CAP data from the two operators, with an intraclass correlation coefficient of 0.84 (95% CI, 0.77–0.88) [4]. In addition, CAP can be used to diagnose fatty liver regardless of etiology. One study recruited 146 patients with chronic hepatitis B, 180 with chronic hepatitis C, and 63 with nonalcoholic fatty liver; all 389 patients received liver biopsy and CAP examination. CAP showed areas under the receiver operating characteristic curve of 0.683, 0.793, and 0.841 in chronic hepatitis B patients with ≥6 %, >33%, and >66% steatosis, respectively. In addition, the accuracy of diagnosing fatty liver did not differ significantly between groups [5].
Fibroscan coupled with CAP shows promise as a noninvasive tool for assessing liver fibrosis and steatosis. Specifically, as this technology provides longitudinal data, it can be effectively used to evaluate treatment outcomes and prognosis in patients with chronic viral hepatitis, nonalcoholic fatty liver disease, or alcoholic hepatitis, as well as other chronic liver diseases.
© 2014 Published by Elsevier Inc.

Detecting Rotator Cuff Tears in Rheumatoid Arthritis: US in Comparison to MRI

Diagnostic Utility of US for Detecting Rotator Cuff Tears in Rheumatoid Arthritis Patients: Comparison with Magnetic Resonance Imaging
Der-Yuan Chen, Howard Haw-Chang Lan, Kuo-Lung Lai, Hsin-Hua Chen , Chan-Pein Chen

ABSTRACT

Background
Ultrasonography (US) is being increasingly used in clinical practice to detect rotator cuff tears (RCTs) in patients with rheumatoid arthritis (RA) who have shoulder pain. The major aim of this study was to determine the diagnostic utility of US and magnetic resonance imaging (MRI) for detecting RCTs in patients with RA who have persistent shoulder pain.

Patients and methods 
With standardized procedures, US and MRI examinations of the shoulder were performed in 36 patients with RA who had persistent shoulder pain prior to arthroscopic intervention. Within 1 month after US and MRI examination, arthroscopic repair was performed. Arthroscopic findings were used as the gold standard for the diagnosis of RCTs.

Results 
Full-thickness RCTs in 28 patients with RA (77.8%) and partial-thickness RCTs in eight patients (22.2%) were identified using arthroscopic inspection. With arthroscopic findings as the gold standard, the sensitivity and accuracy of US in detecting full-thickness RCTs were 92.9% and 89%, respectively, whereas those for MRI were 96.4% and 90%, respectively. In detecting partial-thickness RCTs, the sensitivity and accuracy were 62.5% and 75.0%, respectively, for US, in contrast with 87.5% and 88%, respectively, for MRI. The overall agreement between US and MRI was 89.3% in detecting full-thickness RCTs and 75.0% in detecting partial-thickness RCTs. US demonstrated levels of sensitivity similar to that of MRI in detecting posterior recess synovitis, tenosynovitis, and subacromial-subdeltoid bursitis.

Conclusions

With a good agreement with MRI, US was shown to be a highly sensitive and accurate imaging modality in detecting full-thickness RCTs for patients with RA who have shoulder pain, but appeared to have lower sensitivity in detecting partial-thickness RCTs compared with MRI.

Thứ Sáu, 19 tháng 12, 2014

US Elastography and Achille Tendon

The Achilles is the largest and most frequently injured tendon, and the incidence of injury increases with age. A large-scale study in the literature found that runners older than 40 were more than twice as likely to injure the Achilles tendon and calf muscle, most often as Achilles tendinopathy and gastrocnemius muscle strains, said presenter Laura Chernak Slane, PhD.
Several studies have examined the biological changes in the tendon that occur from aging. Researchers found a variety of factors that occurred at different scales in the tendon, including an increase in elastin content, a decrease in collagen fibril diameter, and a decrease in fascicle sliding.
"But it's challenging to understand how these microscopic changes affect whole-scale tendon mechanics," she said.
In recent years, there's been a lot of emphasis in the biomechanics community on using ultrasound-based methods to track anatomical landmarks while a subject undergoes different types of loading patterns, Slane said.
Conflicting literature results
These in vivo observations in the literature have yielded conflicting results, however. Some studies found that tendon strain increases with age, while others found that tendon strain decreases with age. Another study found that tendon stiffness was the same between age groups.
"So it's unclear what is really happening as we age," she said. "We hypothesize that this might be due to the fact that oftentimes these anatomical landmark-tracking approaches look at large portions of the Achilles tendon, all the way from the calcaneus to the gastrocnemius muscle tendon junction -- really large regions."
The group was interested in learning whether there were spatial variations among different tendon regions that might explain the conflicting results, Slane said. The researchers used a commercially available imaging technique (supersonic shear imaging, SuperSonic Imagine) to evaluate tendon mechanical properties at high resolution.
With the quantitative technique, a focused ultrasound beam induces shear waves in the underlying tissue; the shear waves are then tracked as they propagate throughout the tissue via collection of ultrahigh-frame-rate data. Average shear-wave speeds are calculated and displayed for manually selected regions of interest on the ultrasound image.
"Shear-wave speed is an important mechanical characteristic because it relates to the elastic modulus of a tissue," she said. "As shear-wave speed increases, we expect an increase in tissue stiffness."
The study included 10 healthy young adults (seven females and three males) with an average age of 25 ± 4 years, along with 10 healthy middle-aged adults (five females and five males) with an average age of 49 ± 4 years.
Shear-wave speed (SWS) was measured at three Achilles tendon areas (the free tendon, the soleus aponeurosis, and the medial gastrocnemius aponeurosis) at rest and at dorsiflexed and plantarflexed angles.
Significant variations
Shear-wave speed varied significantly according to imaging location; the free tendon had the highest speeds. In addition, ankle posture significantly affected SWS; speed progressively increased with ankle dorsiflexion along the whole length of the tendon, the researchers found.
There was only one significant age-related difference: a significant reduction in shear-wave speed for middle-aged adults in the gastrocnemius aponeurosis, which "corresponds with the region where calf muscle strains are thought to occur," Slane said. "A lot of MR images show them originating near the muscle-tendon junction."
A significant inverse relationship was seen between resting gastrocnemius aponeurosis SWS and age (R2= 0.34, p < 0.01), and a similar relationship was seen in the gastrocnemius aponeurosis in the dorsiflexed posture (R2 = 0.55, p < 0.01).
Because it's difficult to distinguish the relative contributions of different factors behind these tendon changes, the researchers are now collaborating with a team from the University of Virginia to build a musculoskeletal model to help them interpret the study results, Slane told AuntMinnie.com.
She noted, however, that the significant variation in shear-wave speeds found in different regions of the Achilles "emphasizes that when we're looking at different studies or when we're using it clinically, it's really important that we think about what region we're using and how we're comparing that."
Postural angle also significantly affected SWS, so it's important to report and consider angle and posture with these studies, she added.
The results also suggest that different portions of the Achilles tendon may be changing in different ways.

Thứ Sáu, 12 tháng 12, 2014

ULTRASOUND ANATOMY of LUNG and UPPER RESPIRATORY TRACT

For Medical Tan tao University students.





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Chủ Nhật, 7 tháng 12, 2014

O-mode ULTRASOUND in DEVELOPMENT



CHICAGO — The new O-mode form of ultrasound, which improves visualization behind structures and eliminates the need for beam formation, also weighs and costs less than conventional ultrasound, according to researchers presenting here at the Radiological Society of North America 100th Annual Meeting.
"We were quite impressed that, for the little bit of work that we did, we got such images," said Richard Barr, MD, from the Northeast Ohio Medical University in Youngstown. "The technology is actually not extremely complex," he explained, and said he expects that the small hand-held O-mode device will be available next year.
Dr. Barr presented a proof-of-concept study that confirmed that O-mode imaging is possible in a clinical setting.
The beam focuser required for traditional B-mode ultrasound imaging is considered to be important, but can lead to many of the limitations and artifacts seen in conventional scans. In contrast, the O-mode technique does not require a beam focuser.
The novel technique mimics a "single transducer lateral motion" along a known trajectory. This allows the Doppler effect to be evoked artificially from the "moving" transducer.
The result is an echo in different radiofrequency shifts that comes from the different scatterers located at the same depth but at different lateral positions, Dr. Barr explained. The technique makes it possible to visualize a Doppler shift between the Z particles.
O-mode provides constant lateral resolution that is independent of depth of penetration. It therefore significantly decreases the shadowing from small pockets of gas, allowing for the use of new imaging windows.
It also allows for exact lateral localization by exchanging the traditional ultrasound focusing procedure along the line of sight with signal processing of frequency-modulated signals that come from each depth.
Proof of Concept
To test the effectiveness of the O-mode method, Dr. Barr and his team used the technique to scan various organs of 10 patients.
When the images, which received very little post-processing, were reviewed by a board-certified radiologist, all were deemed to visualize deep structures at least as well as conventional B-mode ultrasound.
In addition, O-mode imaging can be performed in real time at 30 to 40 frames per minute, a rate typical of that seen with other systems, Dr. Barr pointed out.
"That's interesting," said session moderator Jason Stafford, PhD, from the University of Texas MD Anderson Cancer Center in Houston. He told Medscape Medical News that he is eager to read more about the technique.
The next step will be to "implement a small device that will be for the market," said Mati Shirizly, PhD, chief executive officer of Orcasonix, the company that will be manufacturing the O-mode ultrasound. The small device will likely retail for approximately $5000.
"Eventually, we will want to put this technology into a high-end system," Dr. Shirizly told Medscape Medical News. He said he thinks the technique will be particularly useful for imaging the hearts of obese patients.
However, during his presentation, Dr. Barr acknowledged that the O-mode technique still requires improved contrast resolution and improved image processing. Because the O-mode does not yet include image processing, it is difficult to truly compare it to conventional ultrasounds. "At this point, it really is hard to do a comparison of apples to apples. It really is apples to oranges," he said.
This study received funding by Orcasonix, the company that will manufacture the O-mode ultrasound. Dr. Barr is a consultant at Siemens AG. Dr. Stafford has disclosed no relevant financial relationships. Dr. Shirizly is a shareholder at Orcasonix.
Radiological Society of North America (RSNA) 100th Annual Meeting: Abstract SSA21-09. Presented November 30, 2014.

Orcasonix Unveils Innovative Ultrasound Technology Built on Cephasonics cQuest Family of Ultrasound Systems

Visit Cephasonics at RSNA 2013 in Hall B, Booth 8522
Monday, December 2, 2013 - 06:00
Chicago, December 2, 2013—Cephasonics, a technology-innovation leader with a game-changing embedded-ultrasound platform, and Orcasonix, an innovative ultrasound company specializing in imaging systems with depth-independent resolution, today disclosed details of the Cephasonics design-in. Orcasonix used the Cephasonics cQuest Cicada™ platform to develop its first prototype imaging system, the Orca™-1, and plans to commercialize the system in 2014 and go to volume production with the just announced cQuest Dragonfly™ system. Orcasonix will be showcasing its new technology in Cephasonics’ booth at RSNA 2013 held here in Chicago from December 1-6.  Visitors can also see Cephasonics’ latest technology, including Dragonfly.
According to Mati Shirizly, CEO of Orcasonix, “Cephasonics’ unique business model and flexible cQuest Ultrasound™ hardware/software architecture provided us with a fast way to prove our technology, develop a prototype, and conduct initial clinical trials.” He said that his company’s innovative imaging techniques will dramatically improve the scanning of challenging patients, including general abdominal imaging of obese, overweight patients.
“The Orcasonix team achieved a major breakthrough in ultrasound imaging and we are pleased to partner with them both in demonstrating the unique capabilities of their depth-independent resolution imaging system and supporting their production ramp with our solutions,” said Richard Tobias, CEO of Cephasonics.
Orcasonix developed a new ultrasound imaging system with depth-independent resolution that uses a novel patented approach of generating CT-like images from sound echoes. The technology enables an extremely low cost hardware implementation with a virtually unlimited number of channels at a fraction of the cost of current systems. Signal and image processing is extremely efficient, thus significantly reducing the cost of the ultrasound system’s computer sub-system. The Orca-1 will be the first in a planned family of high-quality, cost-efficient imaging systems.
About Cephasonics
A technology-innovation leader with a game-changing embedded-ultrasound platform, Cephasonics provides a complete range of cQuest™-based technology, systems and components that increase the performance, lower the power and accelerate time-to- market of ultrasound devices. The company’s cQuest Ultrasound API™ software is the catalyst for customer innovations that are spurring a revolution in ultrasound from image-guided procedures to ultrasound as an appliance. Launched with a management buyout in March 2012 and headquartered in Santa Clara, Calif., Cephasonics’ technology, including its AutoFocus™ beamforming technology, has won multiple industry awards for innovation. Additional information about Cephasonics can be found at www.cephasonics.com.
About Orcasonix
An innovative ultrasound imaging company that has developed a new ultrasound-imaging platform with depth-independent resolution, Orcasonix was established in 2011 and is based in Netanya, Israel. Its first product has started clinical trials and others are in early stages of development. Additional information about Orcasonix can be found at www.orcasonix.com
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cQuest, cQuest Ultrasound, cQuest Ultrasound API, cQuest Cicada, cQuest Dragonfly, and AutoFocus are trademarks of Cephasonics.
Orca-1 is a trademark of Orcasonix.