Ultrasound

Accurate assessment of skeletal muscle morphology is important in sports physiotherapy, exercise rehabilitation, and research. B-mode ultrasonography is a non-invasive and accessible method for assessing muscle thickness; however, ultrasound-based measurements may be influenced by image acquisition, anatomical landmark identification, and operator-dependent measurement procedures. Establishing inter-rater reliability is therefore essential to determine whether different assessors can obtain consistent measurements of muscle thickness from the same ultrasound images. The rectus abdominis is an important component of the abdominal musculature and contributes to trunk stabilization and functional performance during exercise. Blood flow restriction (BFR) training has gained increasing attention as a low-load exercise strategy for promoting muscular adaptations, although research has predominantly focused on peripheral limb muscles. Therefore, this study aims to evaluate the inter-rater reliability of ultrasound-based rectus abdominis muscle thickness measurements following a standardized BFR training protocol using ImageJ software. Establishing reliable measurement of rectus abdominis thickness will provide a methodological basis for future research investigating abdominal muscle morphology and adaptations in sports physiotherapy, exercise rehabilitation, and BFR-based training.

Uterine fibroids are the most common benign tumors in women of reproductive age, with a prevalence of 20%-50%, often causing menorrhagia, anemia, pelvic pain, and pressure symptoms that markedly impair quality of life. Current treatments include pharmacological therapy (GnRH-a, mifepristone) - effective temporarily but with high recurrence after discontinuation; surgical myomectomy or hysterectomy - definitive yet invasive, with prolonged recovery and potential fertility compromise; and minimally invasive therapies such as uterine artery embolization (UAE), high-intensity focused ultrasound (HIFU), and microwave ablation (MWA), which are increasingly favored for their minimal invasiveness and rapid recovery. MWA delivers thermal energy via a percutaneously inserted antenna under ultrasound guidance, inducing coagulative necrosis of fibroid tissue through temperatures exceeding 60°C. Advantages include minimal trauma (\~2 mm puncture), rapid recovery (discharge within 1-2 days), uterine preservation, and negligible ovarian impact. However, a key limitation is the heat sink effect: in hypervascular fibroids, flowing blood dissipates thermal energy, resulting in incomplete ablation, prolonged procedural time, and higher energy requirements - particularly challenging for fibroids \>5 cm in diameter. Chemical ablation involves intralesional injection of a sclerosing agent (e.g., lauromacrogol), which damages vascular endothelial cells, causing vascular occlusion, thrombosis, ischemic necrosis, and direct membrane disruption that accelerates apoptosis. Theoretically, pre-ablation chemical sclerotherapy may occlude feeding vessels, attenuate the heat sink effect, and enhance subsequent thermal ablation efficiency. Supporting this concept, an ex vivo bovine liver study demonstrated that pre-injection of 5 mL of 99.5% ethanol around the electrode prior to radiofrequency ablation produced a significantly larger ablation zone at equivalent energy levels compared with ablation alone. Small-sample clinical studies, including a prospective cohort from Shanghai Tenth People's Hospital, have preliminarily explored combined chemical ablation plus MWA for uterine fibroids, suggesting improved ablation rates and shorter procedural times, though findings require validation through high-quality randomized controlled trials. Therefore, the investigators conducted this multicenter, prospective, randomized controlled trial to rigorously compare the safety (incidence and severity of adverse events) and efficacy (fibroid volume reduction rate, symptom improvement, quality-of-life outcomes) of MWA alone versus MWA combined with chemical ablation. This study aims to clarify the clinical value of the combined approach and provide high-quality, evidence-based data to guide the optimal selection of minimally invasive treatment strategies for uterine fibroids.

The goal of this observational study is to assess the applicability of non-invasive ultrasound in aneurysms of the descending thoracic aorta. The main question it aims to answer is: What is the feasibility of Ultrasound to visualise the Descending Thoracic Aorta, and can this imaging modality accurately measure the maximum size of aneurysms and residual sacs with acceptable reproducibility? Participants are having their diagnosis confirmed or excluded by conventional imaging techniques (CT scans). Participants receive exactly the same standard of care regardless of their participation. The study offers an additional ultrasound scan, and the results will be compared with previous imaging.

The purpose of this research study is to test a new device called the PUMA-G Pediatric System. The research will measure if the device works well to safely aid doctors placing gastrostomy feeding tubes in children. The PUMA-G Pediatric System is an investigational device that uses ultrasound and magnets to guide insertion of a feeding tube.

Core stability is the ability to control the position and movement of the trunk for optimal production, transfer, and control of forces in the upper and lower extremities during functional activities. Studies have shown that TrA activation is delayed in individuals with low back pain. The relationship between core stability and the lower extremity has been frequently studied in the literature, and according to Kibler's 'Kinetic Chain' theory, loss of proximal stability is known to lead to dysfunction in distal segments; however, the relationship between the upper extremity and core stability is still unclear. The aim of our study is to investigate the upper extremity reach capacity and scapular stability of individuals with low back pain in relation to TrA involvement and to compare them with healthy individuals without low back pain.

Central venous catheterization (CVC) is a fundamental procedure in anesthesiology and reanimation practice for critical clinical processes such as hemodynamic monitoring, vasoactive drug infusion, and fluid resuscitation. The internal jugular vein (IJV) is frequently preferred due to its superficial anatomical location and ease of access. This study aims to observe and compare the ultrasound (USG) guidance and the landmark method in patients scheduled for IJV catheterization.

Twin-twin transfusion syndrome (TTTS) can arise in monochorionic, diamniotic (MoDi), those identical twins arising from division of a single fertilized ovum at 4-8 days gestational age (GA) or monochorionic, monoamniotic (MoMo or Mono-Mono) twins, arising from division on day 8-13 GA. In monochorionic twin pregnancies sharing a single placenta often unevenly, anastomoses \[connections\] artery to artery (AA), vein to vein (VV), and artery to vein (AV) can occur. AV anastomoses usually flow unilaterally, shunting blood unevenly towards one twin and away from the other. This can lead to fluid overload and polyhydramnios along with many other pathologies in one twin while the other twin suffers from inadequate blood flow and oligohydramnios, along with secondary pathologies arising from these conditions. TTTS will affect approximately 8-10% of MoDi twins while 6% of MoMo twins will suffer with this condition. Treatment for TTTS is necessary, with the donor or 'pump' twin having around an 80% chance of death without medical intervention. The aim of this single arm, unblinded, feasibility study of the Verasonics Vantage 256 device is to leverage the devices ultrafast power Doppler imaging (uPDI) to perform microvascular mapping of the placenta in healthy, non-anomalous, 18-26 week gestational age (GA), monochorionic, diamniotic (MoDi) or monochorionic, monoamniotic (MoMo/MonoMono) pregnancies without TTTS, twin reversed arterial perfusion sequence (TRAP), or maternal vascular disease. Participants will be recruited in the Maternal Fetal Medicine department of Carilion Clinic, which specializes in high risk or complicated pregnancies. Pregnant subjects carrying monochorionic twins and scheduled for appointments at the clinic, who meet study eligibility criteria, will be approached between weeks 18 and 26 for study enrollment. Those providing informed consent will undergo a single, transabdominal ultrasound examination by a licensed ultrasonographer or obstetrician with the Verasonics Vantage 256 ultrasound machine, with imaging focused on mapping the vasculature of the placenta with ultrafast power Doppler imaging (uPDI). The ultrasound exam will last about 15 minutes and occur immediately after the subject's standard-of-care appointment at the clinic so as not to inconvenience subjects more than necessary. Similar to commercially marketable ultrasounds in the US, the Verasonics ultrasound will use the principle of 'As Low As Reasonably Achievable (ALARA) to output the lowest acoustic waves possible to achieve the ultrasound imaging. After the single ultrasound scan, subjects' electronic medical records will be used to source demographic, medical, obstetric, and other historical datapoints to better characterize the 10-subject study population and their babies. No follow-up contact with subjects is expected after the single research ultrasound visit.

The goal of this proof-of-concept, case-control, clinical trial is to evaluate the efficacy of using two newer ultrasound technologies, quantitative ultrasound (QUS) and ultrafast power Doppler imaging (uPDI), to evaluate the health of the placenta, visualize blood flow through the placental vasculature by color Doppler imaging in singleton pregnancies with and without fetal growth restriction (FGR). * Our primary objective is to investigate the ability of using these ultrasound technologies to distinguish healthy pregnancies from those affected by FGR, a condition characterized by a fetal weight below the 10th percentile for the gestational age or abdominal circumference of the pregnancy. * Secondary aims include longitudinal evaluation of differences in QUS and uPDI imaging over gestation and changes in these measures with evolution of utero-placental insufficiency including with the development of abnormal umbilical-artery Doppler testing, diagnosis of severe FGR, identification of stillbirth, and detection of preeclampsia or preterm birth. Investigators will compare QUS/uPDI imaging and values in pregnancies determined to be healthy by approved, standard-of-care growth ultrasounds to those diagnosed with FGR. Participants will receive research ultrasounds with the experimental Verasonics Vantage 256 system (Verasonics, Inc, Kirkland, WA) utilizing uPDI/QUS every three weeks following their routine growth ultrasound evaluation until delivery. Demographic, obstetric, and delivery-related information, as well as portions of subjects' past medical history will be utilized by researchers to further contextualize imaging and variables gathered during the research ultrasounds.

The use of lung ultrasound is instrumental in the evaluation of many chest pathologies and its ability to detect pleuro-pulmonary pathology is widely accepted. However, the use of ultrasound to explore the state of the peripheral lung parenchyma, when the organ is still aerated, is a relatively new application. Horizontal and vertical artifacts are separate and distinct artifacts that can be seen during ultrasound examination of the lungs. While the practical role of lung ultrasound artifacts is accepted to detect and monitor many conditions, further research is needed for the physical interpretation of ultrasound artifacts. These artifacts are diagnostic signs, but we don't fully understand their origin. The artifactual information deriving from the surface acoustic interaction, beyond the pleural line, in the ultrasound images of the normally aerated and non-deflated lung, represents the final result of complex interactions of acoustic waves with a specific three-dimensional structure of the biological tissue. Thus, the umbrella term "vertical artifacts" oversimplifies many physical phenomena associated with a pathological pleural plane. There is growing evidence that vertical artifacts are caused by physiological and pathological changes in the superficial lung parenchyma. Therefore, the need emerges to explore the physical phenomena underlying the artifactual ultrasound information deriving from the surface acoustic interaction of ultrasound with the pleuro-pulmonary structures.

Current guidelines support the use of predictive clinical tests in the evaluation of difficult airway, meaning either difficult bag and mask ventilation, conventional laryngoscopy and/or endotracheal intubation. However, despite the clinical use of these predictive tests, unpredictive difficult laryngoscopy complicates 1.5-13% of cases. Life threatening scenarios may be encountered in patients with difficult or impossible bag and mask ventilation. Anaesthesiologists are familiar with the use of ultrasound, with peripheral nerve blockade and central vascular access representing the most popular applications during the last decades. The ultrasound provides real time and accurate images. According to the current literature, there are only a handful of studies relevant to the application of point of care ultrasound (POCUS), as a new tool in the upper airway evaluation. It is a new field of research with high interest. This is a prospective observational study to investigate if specific ultrasound measurements of the anterior neck can serve as predictors of difficult airway. The ultrasound parameters will be measured preoperatively, during the preanaesthetic evaluation, along with standard clinical prognostic tools, like the mallampati score. The ultrasound parameters to be investigated are: 1. the distance from thyroid isthmus to skin surface, 2. the distance from the hyoid bone to the skin surface, 3. the distance from the anterior commissure of vocal cords to the skin surface, 4. the distance from skin to the trachea at the level of jugular notch, 5. the distance from skin to epiglottis corresponding to half of the distance between thyroid cartilage and hyoid bone, 6. and the angle between glottis and epiglottis. After the induction in anaesthesia, the Cormack Lehane score (grading of the laryngoscopy view) and the Han scale (grading of the degree of difficulty of bag and mask ventilation) will also be recorded. The goal of this study is the investigation of the role of POCUS in the evaluation of difficult bag and mask ventilation and difficult intubation. The primary endpoint is the incidence of difficult bag and mask ventilation and the incidence of difficult laryngoscopy and intubation. Secondary endpoints are the correlations between clinical prognostic tools of difficult airway and the POCUS parameters under investigation.

Introduction The current diagnostic approach for patients with suspected oropharyngeal cancer involves a combination of clinical examination, tissue sampling, and relevant cross-sectional imaging. Previous studies have shown that transoral and cervical ultrasound (US) of the palatine and lingual tonsils has a better diagnostic accuracy than clinical investigation and magnetic resonance imaging (MRI) in patients with suspected oropharyngeal cancer, but it has not been established whether adding this scan to the diagnostic workup has a clinical impact. Methods A randomized controlled study, including 170 patients at four different Head and Neck Hospital departments in Denmark. One group receives standard diagnostics (control group), and the other group receives standard diagnostics supplemented by transoral and cervical ultrasound of the lingual and palatine tonsils. The diagnostic accuracy, number of correct biopsies, number of imaging modalities ordered, and time to final diagnosis are noted. Conclusion This randomized controlled study examines whether the implementation of transoral and cervical ultrasound of the palatine and lingual tonsils in patients with suspected oropharyngeal cancer will improve the diagnostic accuracy and have a clinical impact. This concerns more accurate initial diagnoses, more correct biopsies, fewer unnecessary scans, and fewer visits to the outpatient clinic.

Carpal tunnel syndrome (CTS) is a common musculoskeletal disorder, which is caused by compression of the median nerve as it travels through the wrist. There are several treatments for CTS, including conservative and surgical options. Though local corticosteroid injection has been considered more effective than physical therapy for treatment of CTS and has significant short-term benefits, long term benefits are not evidenced. Several studies in recent years reported significantly superior longer-term benefit of D5W and PRP compared with corticosteroid injections and other conservative managements. In addition, percutaneous release of the transverse carpal ligament (TCL) was developed to treat CTS in recent years. Because the effectiveness of the recently developed techniques in treating CTS has not been well established, the investigators aim to investigate whether combining US-guided partial release of the transverse carpal ligament with a needle plus D5W hydrodissection is more beneficial for CTS comparing to either treatment alone.

Atherosclerotic plaques, the build-up of fatty materials within our arteries, can develop over a long period of time without causing any symptoms. These plaques may continue to grow and rupture causing narrowing and blockages of the blood vessels. This can lead to serious cardiovascular disease such as a heart attack or stroke causing over 160,000 deaths each year. Lots of research has been done on why particular groups of people may develop atherosclerosis and controlling risk factors such as diabetes and high blood pressure go a long way to reduce people's risks. However, despite the treatments we have available and controlling these risk factors, some people unfortunately still go on to develop a potentially serious disease. Further research has shown us that certain plaques in the blood vessels may be more vulnerable to rupturing compared to others. So far we know that plaques with thin caps, soft centres or those that are able to grow their own tiny blood vessels are more likely to rupture. We have now started to develop new imaging methods to try and help us detect these vulnerabilities. The hope is by being able to detect more vulnerable plaques we may be able to treat these earlier and therefore more effectively. There are different scans available to try and visualise the tiny vessels within these plaques in the neck arteries. These include, MRI (a Magnetic Resonance Imaging scan, taking pictures using a small tunnel), CT (Computed Tomography, uses a ring-shaped machine to take pictures), and ultrasound. Ultrasound has the benefit of being free of ionising radiation and iodinated contrast, therefore posing less risk to patients. However, current ultrasound uses 2D ultrasound. Although this has shown promising results, our blood vessels and any plaques are 3D structures so we don't get to see the whole plaque using 2D imaging and therefore may miss important information. The available 3D probes in use at the moment are not able to visualise the tiny vessels accurately enough. This study uses a different 3D ultrasound probe and ultrasound machine that is able to produce many more images than our usual probes. By taking images with this probe and using offline computer programmes to track the contrast through structures we hope that this system will be able to give us a visualisation of the whole plaque enabling us to detect any new blood vessels more accurately.

Circumcision is a widely performed surgical procedure. For this reason, optimal analgesic management is essential. Loco-regional anesthesia, particularly penile blocks, combined with general anesthesia is the technique of choice for managing analgesia during circumcisions. Ultrasound is increasingly used in locoregional anesthesia techniques. There is already human research on penile blocks and the use of ultrasound. Studies carried out to date describe an optimization of pain relief in children after circumcision compared with the alternative technique without ultrasound, as well as a reduction in local complications due to injection. However, other studies tend to contradict these findings. In order to provide additional knowledge and to verify whether ultrasound could provide with more optimal relief after your circumcision, the investigators are carrying out this study. The investigators are proposing to every patient aged 0 to under 18 who is going to undergo circumcision to take part in this project. A letter is sent to all potential participants no later than 3 days before the operation. Consent can be signed no later than the day of the operation. The cooling-off period is the same regardless of age. Taking part in the study does not affect the operation in any way. The block will take place in the operating room, prior to surgery. In this study, participants are randomized into groups. This method is important for obtaining reliable results. * Group 1 (intervention group): The penile block will be performed using ultrasound. * Group 2 (control group): The penile block will be performed using anatomical landmarks. This is a "single-blind" study, which means that only the anaesthetists, investigators and operating room team will be aware of the allocation to one of the two groups. Data on opiate consumption will be registered as well as the different durations preoperatively, intraoperatively, postoperatively, back in the recovery room and before returning home or any complications as well as pain assessment.

The aim of this study is to early detect kidney disease in the natural population cohort of children by urine and ultrasound screening, to assist in the precise prevention and treatment of children's kidney disease, and to establish a risk prediction system for children's kidney disease. About 10,000 children called KunQi Cohort are born in Jiangsu Province(8,000 in Kunshan and 2,000 in Qidong) and about 3,000 born in Shanghai. Through the project, child who is found with abnormal urine or ultrasound result will be referred to Children's Hospital of Fudan University to get further examination and treatment.

The aim of our study is to determine the relationship between disease severity and sleep quality in CTS patients and to compare the findings with healthy controls.

This observational study aims to evaluate the relationship between small bowel ultrasound findings and tissue transglutaminase (tTG) antibody blood levels in assessing celiac disease activity. The traditional gold standard for diagnosing and monitoring celiac disease involves an invasive duodenal biopsy. Researchers want to determine if combining a painless, non-invasive small bowel ultrasound with tTG antibody blood tests can accurately predict disease severity and monitor a patient's response to a gluten-free diet. The study will enroll 140 participants aged 2 years and older, including newly diagnosed patients, patients currently on a gluten-free diet, and a control group. All participants will undergo a clinical assessment, blood tests for tTG antibodies, and a high-resolution small bowel ultrasound. Newly diagnosed patients will also undergo an upper gastrointestinal endoscopy and biopsy to confirm their diagnosis. Researchers will score the ultrasound severity based on factors like bowel wall thickness and compare it to the antibody levels. A cohort of patients will be monitored over time with serial assessments at baseline, 6 months, and 12 months.

Neuraxial blockade is commonly performed using a manual palpation technique, but the procedure can be challenging, particularly in patients with high body mass index, pregnancy, or spinal deformities. Preprocedural ultrasound may improve identification of the optimal injection site, yet its use in clinical practice remains limited, partly due to a lack of structured training. This multicentre randomised controlled trial investigates whether anaesthesiologists performing ultrasound-assisted spinal anaesthesia achieve better clinical outcomes and higher patient satisfaction compared with the traditional manual palpation technique. Both novice anaesthesia residents and more experienced anaesthesiologists are included. Participants receive structured simulation-based training using either ultrasound-assisted or manual palpation techniques, following a mastery learning approach with predefined performance standards. After certification, participants perform spinal anaesthesia during elective lower limb surgery, with clinical performance assessed by senior anaesthesiologists. The primary outcome is first-attempt success of spinal block. Secondary outcomes include number of attempts, needle redirections, time spent, need for assistance, and overall block success. Patient satisfaction and complications are assessed as tertiary outcomes. This study aims to provide evidence on the clinical effects of structured training in ultrasound-assisted neuraxial access and to explore the role of prior clinical experience.

Study Aim: This trial evaluates if a novel non-invasive, AI-assisted simulation training improves ultrasound-guided needle visualization skills in anesthesia residents. Design: Trainees were randomized into two groups: Intervention: AI-based, non-invasive simulated needle puncture training. Control: Conventional ultrasound teaching. Key Outcomes: The primary outcome is objective needle tip visibility. Secondary outcomes include anatomical identification, correct view acquisition, operator confidence, and overall scanning performance. Assessment: Outcomes are measured via blinded expert evaluation and theoretical tests. The goal of this randomized controlled clinical trial is to determine whether an ultrasound-guided non-invasive simulated needle puncture training technique can improve ultrasound-guided needle visualization skills in anesthesiology residents undergoing standardized residency training. The study is conducted in anesthesiology residents enrolled in a standardized residency training program. The main questions it aims to answer are: 1. Does non-invasive simulated needle puncture training improve objective needle tip visibility during ultrasound-guided peripheral nerve block procedures? 2. Does this training method improve anatomical structure identification, acquisition of correct block views, operator confidence, and overall scanning performance compared with conventional ultrasound teaching? Researchers will compare a non-invasive simulated needle puncture training group with a conventional ultrasound teaching group to see if the simulated training technique leads to superior needle visualization and procedural performance. Participants will: Receive standardized theoretical instruction on ultrasound- guided peripheral nerve blocks; Be randomly assigned to either non-invasive simulated needle puncture training using an artificial intelligence-assisted system or conventional ultrasound scanning training; Perform ultrasound scanning and simulated or conventional practice on healthy volunteers; Undergo theoretical examinations and blinded expert assessments of ultrasound scanning performance and needle visualization outcomes.

Postextubation distress is detrimental to the prognosis of critically ill patients with successful spontaneous breathing trial. Failure to wean is known to be connected with heart, lung, and diaphragm problems. The aim of this study was to investigate how a composite model comprising diaphragm, lung, and heart ultrasonography indications could predict the weaning outcome. Methods: Ultrasonic features of the diaphragm, heart, and lungs are going to be collected along with clinical data about the patients. Either the successful weaning group or the failed weaning group is going to comprised the patients. Multivariate logistic regression analysis is going to be used to identify the variables that may be associated with the likelihood of weaning failure. A multiindicator combination model is going to be developed to increase the predictive accuracy after the possible indicators' accuracy in foretelling the weaning outcome was assessed.

This study aims to compare the analgesic efficacy, duration of analgesia, and overall opioid consumption between the external oblique intercostal plane (EOIP) block and subcostal transversus abdominis plane (TAP) block in patients undergoing laparoscopic sleeve gastrectomy.

Timely detection of signs of raised intracranial pressure or persistent inflammation within the meninges can expedite therapeutic decisions improving the prognosis of patients with brain damage. Optic nerve ultrasonography provides a user-friendly, safe, low-cost, and non-invasive imaging method that can be easily deployed for ICU patient assessment. This study aims to evaluate the sensitivity and specificity of optic nerve ultrasound in estimating cerebral inflammation extension and cerebral edema in patients in the ICU. The working hypothesis is that optic nerve ultrasound is a useful tool in the rapid diagnosis of cerebral edema and the presence or persistence of cerebral inflammation, which can enable adapted and rapid therapeutic interventions.

The goal of this clinical trial is to learn if robotic ultrasound screening works as well as or better than traditional sonographer-led screening for detecting breast cancer. It will also explore how well participants follow recommended post-screening care. The main questions it aims to answer are: Does robotic ultrasound screening detect more cases of breast cancer compared to traditional sonographer-led screening? How well do participants follow up on recommended care after robotic ultrasound screening? Researchers will compare robotic ultrasound screening to traditional sonographer-led screening to see if robotic ultrasound works effectively for breast cancer screening. Participants will: Receive a breast ultrasound performed either by a robotic system or a human sonographer. Undergo follow-up management based on their BI-RADS classification.

This study aims to evaluate the efficacy of ultrasound-guided external oblique and rectus abdominis plane block on the neuroendocrine stress response and postoperative analgesia in adults undergoing umbilical hernia repair.

DETECT-HCC-ESLD is a prospective multicenter study designed to examine early detection and risk stratification of hepatocellular carcinoma (HCC) in individuals with advanced liver disease. Adults with cirrhosis of different etiologies are enrolled and followed longitudinally with structured clinical assessments and imaging at predefined intervals. A key objective is to evaluate ultrasound and abbreviated MRI (AMRI) as surveillance modalities for HCC. The study examines detection performance, feasibility, and factors influencing image quality and interpretability. The protocol also includes the study of body composition, focusing on how variations in adiposity and muscle mass may relate to imaging characteristics, disease progression, and HCC risk. Longitudinal clinical and imaging data are used to explore prediction models aimed at identifying patients with differing levels of HCC risk. The study records outcomes such as incident HCC, liver-related complications, and mortality to support analyses of disease trajectories. The DETECT-HCC-ESLD study provides a structured framework for collecting clinical, imaging, and body composition data over time, enabling detailed evaluation of surveillance strategies and risk patterns in advanced liver disease.