Real-time B-mode Ultrasound Imaging Research Articles

Palm-Sized Wireless Transient Elastography System with Real-Time B-Mode Ultrasound Imaging Guidance: Toward Point-of-Care Liver Fibrosis Assessment.

Transient elastography (TE), recommended by the WHO, is an established method for characterizing liver fibrosis via liver stiffness measurement (LSM). However, technical barriers remain towards point-of-care application, as conventional TE requires wired connections, possesses a bulky size, and lacks adequate imaging guidance for precise liver localization. In this work, we report the design, phantom validation, and clinical evaluation of a palm-sized TE system that enables simultaneous B-mode imaging and LSM. The performance of this system was validated experimentally using tissue-equivalent reference phantoms (1.45-75 kPa). Comparative studies against other liver elastography techniques, including conventional TE and two-dimensional shear wave elastography (2D-SWE), were performed to evaluate its reliability and validity in adults with various chronic liver diseases. Intra- and inter-operator reliability of LSM were established by an elastography expert and a novice. A good agreement was observed between the Young's modulus reported by the phantom manufacturer and this system (bias: 1.1-8.6%). Among 121 patients, liver stiffness measured by this system and conventional TE were highly correlated (r = 0.975) and strongly agreed with each other (mean difference: -0.77 kPa). Inter-correlation of this system with conventional TE and 2D-SWE was observed. Excellent-to-good operator reliability was demonstrated in 60 patients (ICCs: 0.824-0.913). We demonstrated the feasibility of employing a fully integrated phased array probe for reliable and valid LSM, guided by real-time B-mode imaging of liver anatomy. This system represents the first technical advancement toward point-of-care liver fibrosis assessment. Its small footprint, along with B-mode guidance capability, improves examination efficiency and scales up screening for liver fibrosis.

Real-time imaging and control of boiling histotripsy lesion formation using Doppler ultrasound

In boiling histotripsy (BH), millisecond-long HIFU bursts with shocks are used to mechanically liquefy tissue. Most BH studies have been performed under real-time B-mode ultrasound imaging of bubbles generated at the treatment site. However, such approach does not allow quantitative assessment of the degree of tissue liquefaction. In addition, aberration and clutter often limit the echogenicity introduced by bubbles. In this work, plane wave Doppler followed by B-mode imaging were implemented immediately after each BH pulse to visualize residual bubble motion during volumetric BH treatments in ex vivo bovine liver. The changes in the Doppler power and speed were used as metrics to assess the degree of tissue liquefaction. An ATL P6-3 imaging probe connected to a Verasonics Ultrasound Engine (VUE) was mounted in the central opening of a 256-element 1.5 MHz HIFU array driven by another VUE with 1.2 kW external power source enhanced by a capacitor bank. The proposed imaging sequence improved BH targeting and bubble visualization. As tissue liquefaction progressed from partial to full (single versus five BH pulses per focal spot), both Doppler power and residual bubble velocity directed away from the transducer increased (7-fold and 10 cm/s to 20 cm/s, correspondingly) and then saturated. [Work supported by NIH R01EB7643.]

Anterior Thigh Tissue Thickness Measured Using Ultrasound Imaging in Older Recreational Female Golfers and Sedentary Controls.

Physical activity is vital for the prevention of sarcopenia and frailty. The training effects of recreational golf on muscle function in older people are unknown. The present study examined quadriceps muscle and subcutaneous fat thickness in 66 older females. Thirty-one golfers (mean age 69.1 years, standard deviation ±3.4) were compared with 35 less active non-golfers (73.4 ± 4.2 years). Images of the dominant anterior thigh were obtained using real-time B-mode ultrasound imaging. Thickness of muscle (rectus femoris, vastus intermedius, and intermuscular fascia) and subcutaneous tissue (fat and perimuscular fascia) was measured, and percentage contributions calculated. Muscle thickness was significantly greater (p < 0.001) in golfers (mean 2.78 cm ± 0.73 cm) than non-golfers (2.18 cm ± 0.55 cm). Mean percentage contribution of muscle and non-contractile tissue was 64% ± 9% and 36% ± 9%, respectively, in golfers, compared to 58% ± 8% and 42% ± 8% in non-golfers (p = 0.013). Multiple linear regression analysis, controlling for age and BMI, showed that golfers still had higher total anterior thigh thickness (regression parameter for non-golfers B = −0.984, p = 0.004) and higher muscle thickness (B = −0.619, p = 0.002). This study indicates an association between recreational golf and greater relative thigh muscle thickness and lower subcutaneous fat than in less active controls. Training effects need to be examined in prospective controlled trials in males and females in different age groups.

Liver Fibrosis Assessment Using Transient Elastography Guided with Real-Time B-mode Ultrasound Imaging: A Feasibility Study

Liver fibrosis is a kind of chronic damage of the liver and can lead to cirrhosis, one of the top 10 causes of death in the Western world. However, there is still a lack of noninvasive methods for diagnosing liver fibrosis. Fibroscan (Echosens, Paris, France), a device based on A-mode transient elastography, has shown promising results. In this study, a transient elastography system with real-time B-mode imaging for non-invasive liver fibrosis assessment, named Liverscan, was developed; its performance was tested and compared with that of the Fibroscan. A specific measurement probe was designed and fabricated with a B-mode ultrasound transducer fixed along the axis of a mechanical vibrator. It was integrated with the Liverscan to measure liver stiffness based on the shear wave propagation in liver tissues. The system was validated by mechanical indentation test using custom-made agar-gelatin phantoms with different stiffness. To further test its feasibility, in vivo measurements were conducted in 67 volunteers (age, 34 ± 3 years; body mass index, 21.3 ± 2.8 kg/m2; Mean ± SD., 34 male and 33 female), including 20 patients with various liver diseases, and 28 (19 male and 9 female) being tested by both Liverscan and Fibroscan. A significant linear correlation between the stiffness measured by the mechanical indentation test and that by the Liverscan (r = 0.973; p < 0.001) was obtained. The in vivo liver stiffness measured by Liverscan was also correlated with that by Fibroscan significantly (r = 0.886; p < 0.001). There was a significant difference in liver stiffness between the 20 patients and the other healthy subjects (14.1 ± 3.4 kPa vs. 10.5 ± 2.1 kPa; p = 0.001). The intra- and inter-observer tests indicated that the measurements were repeatable with intra-class correlation coefficients being 0.987 (p < 0.001) and 0.988 (p < 0.001), respectively. This study demonstrated that Liverscan with a specifically designed probe was able to measure and differentiate liver of different stiffness using the established measurement protocol under the guidance of real-time B-mode ultrasound imaging.

Diagnosis of deep vein thrombosis using real-time B-mode ultrasound imaging

The authors discuss real-time B-mode imaging in reference to the diagnosis of deep vein thrombosis. This technique is noninvasive, reproducible, painless, and accurate in diagnosing deep vein thrombosis. A case report demonstrating the effectiveness of this modality is presented. The authors believe this diagnostic tool will soon become the procedure of choice in the diagnosis of deep vein thrombosis.

Ultrasound confirmation of endotracheal tube placement.

Real-time B-mode ultrasound imaging was performed in 24 intubated patients in order to confirm the correct placement of endotracheal tubes. The large acoustic impedance mismatch between the air within the endotracheal tube cuff and the tracheal wall could be bypassed by (1) use of a foam-cuffed Bivona endotracheal tube, or by (2) cuff inflation with saline instead of air. Optimal repositioning of the endotracheal tube could be done under direct visualization. Imaging of the foam-filled and saline-filled cuffs was easier in the longitudinal (sagittal) than in the transverse view, was enhanced by a slight longitudinal to-and-fro motion of the tube, and was often improved with the use of a stand-off pad. Cases of esophageal intubation were not considered. Use of a noninvasive imaging modality such as ultrasound will spare selected patients from the radiation exposure associated with a chest x-ray. This is of value in pregnant patients and in those requiring frequent chest radiographs for the sole purpose of confirming correct endotracheal tube placement. Limitations of the techniques are discussed.

Follow up of acute deep venous thrombosis by real time B-mode ultrasound imaging and continuous wave doppler (Echography Doppler)

Follow up of acute deep venous thrombosis by real time B-mode ultrasound imaging and continuous wave doppler (Echography Doppler)

Ultrasound characteristics of recurrent carotid disease: Hypothesis explaining the low incidence of symptomatic recurrence

The true incidence of recurrent disease after carotid endarterectomy (CENDX) is unknown, but noninvasive hemodynamic testing shows a paradox between the incidence of hemodynamically significant recurrent stenosis (RS) and the presence of symptomatic disease. We have shown that real-time B-mode ultrasound imaging can demonstrate the gross pathology of the arterial wall and plaque and their surface characteristics. Therefore we reviewed the clinical data and B-mode studies performed 6 months to 15 years after 276 carotid endarterectomies. Preoperative and perioperative risk factors and associated symptoms on follow-up were stored on computer. The patients were divided into three groups by the anatomy of their B-mode study. The majority of the studies were normal (203 [73.5%]), 42 (15.2%) showed mild disease, and 34 (12.3%) demonstrated significant RS. The RS group had a statistically significant increase in incidence of known lipid abnormalities (p < 0.05), associated peripheral vascular disease, previous myocardial infarctions, and ulcerated plaque on the original carotid endarterectomy (p < 0.01). The site of RS appeared related to the time of detection by B-mode ultrasound imaging. Internal carotid RS developed late (>4 years), as did RS of the bifurcation. By contrast, stenosis at the common carotid level developed earlier. These findings suggest different pathogenic mechanisms—for the former, redevelopment of atherosclerosis; for the latter, accentuation of preexisting atherosclerosis perhaps by hemodynamic factors. Finally, in the 26 vessels with RS without occlusion, there was an 8% incidence of plaque ulcer or hemorrhage vs. a 62% incidence in 79 primary atherosclerotic plaque previously studied by both B-mode and pathologic examination. The low incidence of plaque characteristics associated with symptomatic disease may account for the low incidence of symptomatic disease associated with RS.

The Peroperative Use of Real-Time B-Mode Ultrasound Imaging in Biliary and Pancreatic Surgery

The current state of the use of ultrasound imaging during biliary and pancreatic surgery is discussed. Special attention is drawn to the peroperative application of ultrasound for the peroperative screening of the common bile duct. The advantages and drawbacks of this method are discussed.

Department of Surgery, Bristol Royal Infirmary, U.K.

Recent developments in ultrasound techniques have made it possible to investigate patients with arterial disease non-invasively by using Doppler blood velocity signal analysis. Since January 1979, 189 patients were pre-stroke syndromes have been investigated by using pulsed Doppler and real-time B-mode ultrasound imaging and waveform analysis. The results were that both imaging systems were highly (more than 92%) sensitive and specific when compared with conventional carotid arteriography. The ultrasound systems detected turbulence and could also be used to measure the distensibility of the arterial wall. The results show that varying grades of carotid stenosis can be demonstrated by two ultrasonic imaging systems, and that lateral scans are particularly helpful.