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.