Linear Array Ultrasound Transducer Research Articles

Ulnar Nerve Hydrodissection at the Elbow With Ultrasound Guidance

Background: Ulnar neuropathy at the elbow (UNE) is common, and treatment ranges from bracing and nonsteroidal anti-inflammatory drugs (NSAIDs) to surgical decompression. Prior to surgical intervention, some patients may opt to receive perineural injections to the ulnar nerve. The goal of this injection is to reduce pain, improve symptoms, and decrease nerve cross-sectional area through mechanical decompression. While the use of hydrodissection as a treatment for carpal tunnel syndrome has been well studied, there are few studies evaluating its utility in UNE. Indications: Ultrasound-guided perineural injections can be used to alleviate symptoms of UNE caused by compression. The use of a gel stand-off technique is helpful in maintaining adequate visualization of the needle with a steeper needle angle. Technique Description: The procedure was carried out with patient supine, shoulder abducted to 90°, and the forearm supinated. A 15-6 MHz linear array ultrasound transducer was used to localize the right ulnar nerve proximal to the retrocondylar groove at an area of focal hypoechogenicity and increased nerve cross-sectional area. A 3 mL mixture of 2 mL of 1% lidocaine and 1 mL of 10 mg/mL dexamethasone was injected using a sonographically guided in-plane anterior-to-posterior technique. Results: Our patient was seen 3 weeks after her right-sided ulnar nerve hydrodissection and had experienced temporary reduction in symptoms. Discussion/Conclusion: UNE is a common cause of focal neuropathy. Most patients will experience adequate relief of symptoms with conservative treatment modalities. If patients do not experience adequate symptom relief, ultrasound-guided ulnar nerve injection is a minimally invasive option that can provide symptom relief. However, if patients continue to experience significant symptom burden, it is reasonable to discuss surgical options for ulnar nerve decompression. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Updates on Neuronavigation: Emerging tools for tumor resection.

Multiple studies have been conducted to properly elucidate the various tools available to help enhance the resection of tumor tissue, aneurysms, and arteriovenous malformations (AVM). Diffusion tensor imaging (DTI) tractography is useful in providing a map of the tumor borders, allowing the optimal preservation of function and structure of specific regions of the brain. During neurosurgery, especially craniotomies, the possibility of the brain shifting due to swelling or gravity is high. Thus, tools for intraoperative imaging such as high-frequency linear array ultrasound transducers and doppler ultrasonography are utilized for high resolution images and detecting frequency shifts. 4D-digital subtraction angiography (DSA) is another technique used to create spatial resolutions and 3D maps for aneurysms. These similar techniques can also be utilized to assess the integrity of white matter in AVM. By implementing effective evaluation strategies, healthcare professionals can make informed decisions regarding treatment options, preventive measures, and long-term care plans tailored to individual patients.

Handheld photoacoustic imaging of indocyanine green clearance for real-time quantitative evaluation of liver reserve function.

Preoperative assessment of liver function reserve (LFR) is essential for determining the extent of liver resection and predicting the prognosis of patients with liver disease. In this paper, we present a real-time, handheld photoacoustic imaging (PAI) system-based noninvasive approach for rapid LFR assessment. A linear-array ultrasound transducer was sealed in a housing filled with water; its front end was covered with a plastic wrap. This PAI system was first implemented on phantoms to confirm that the photoacoustic (PA) intensity of indocyanine green (ICG) in blood reflects the concentration of ICG in blood. In vivo studies on normal rabbits and rabbits with liver fibrosis were carried out by recording the dynamic PA signal of ICG in their jugular veins. By analyzing the PA intensity-time curve, a clear difference was identified in the pharmacokinetic behavior of ICG between the two groups. In normal rabbits, the mean ICG clearance rate obtained by PAI at 15 min after administration (PAI-R15) was below 21.6%, whereas in rabbits with liver fibrosis, PAI-R15 exceeded 62.0% because of poor liver metabolism. The effectiveness of the proposed method was further validated by the conventional ICG clearance test and pathological examination. Our findings suggest that PAI is a rapid, noninvasive, and convenient method for LFR assessment and has immense potential for assisting clinicians in diagnosing and managing patients with liver disease.

PHSPP06 Presentation Time: 3:20 PM: A New Way to Visualize Needles for Ultrasound Prostate Brachytherapy Using Color Doppler and Needle Surface Modifications

<h3>Purpose</h3> Brachytherapy applicator conspicuity during ultrasound (US) imaging can be impaired by bowel gas, tissue interfaces, or when the applicator is far or angled with respect to the ultrasound probe. Without adequate conspicuity, applicators can be inaccurately reconstructed, leading to decreased tumor control or increased normal tissue dose due to a geometrically inaccurate treatment plan. To improve the conspicuity of titanium high-dose rate (HDR) brachytherapy needles under US imaging, the surface of needles can be modified, and color-Doppler can be utilized to highlight the surface patterns. Color-Doppler imaging can produce a twinkling signature, also referred to as a ‘twinkling artifact,' when ultrasound waves reflect from a surface with a rough or patterned structure. The twinkling signature highlights the modified applicator as variegated pixels atop a grayscale B-mode US image, enhancing conspicuity. This research was a preliminary investigation into the types of surface modifications that can produce a twinkling signature, based upon a review of prior literature that has associated surface roughness with twinkling. <h3>Materials and Methods</h3> The surfaces of 17-gauge, 25 cm titanium HDR brachytherapy needles were modified using three methods of surface modification: sandblasting with an 80-grit media, laser-etching of thin grooves, and application of a polymethyl methacrylate (PMMA)-based bone cement. Laser-etches were created on the surface of the needles using a 343 nm femtosecond laser (Pharos, Light Conversion, Lithuania) on a machining system (Photomachining Inc., USA) and were created at variable widths (0.1-1 mm) and depths (10-100 μm) without penetrating the inner lumen of the applicator. Unmodified and modified needles were imaged with a bk3000 (BK Medical, USA) with an E14CL4b transrectal probe and Logiq E9 (General Electric, USA) with a 9L linear-array transducer under B-mode and color-Doppler imaging. Needle conspicuity between needle types was assessed qualitatively in the axial and sagittal planes within a prostate phantom (CIRS, Inc., USA). <h3>Results</h3> Color-Doppler imaging in combination with surface-modified needles produced a twinkling signature with select laser-etched and PMMA-cement surface modifications. The twinkling signature appeared as a color signal atop the applicator, overlaid on grayscale B-mode ultrasound images. The twinkling signature was observed with both transrectal and linear-array ultrasound transducers. Twinkling was observed at laser-etched scribe depths >20 μm and widths >0.1 mm, and it was observed that the magnitude of the twinkling signature was dependent upon the total surface area of the etched region. It was also demonstrated that needles can be laser-etched or coated with PMMA-cement to mark a reference location with respect to the needle tip (2 cm distal). The hand-roughened needles produced a faint twinkling signature with the linear-array transducer and negligible twinkling with the transrectal transducer. Sandblasted and unmodified needles produced a negligible twinkling signature. Generally, the twinkling signature was observed to be transient in nature and dependent on the pressure between the probe and the phantom. Future work is planned to study the mechanisms underlying the color-Doppler signal and to establish an optimal surface modification and signal strength. <h3>Conclusions</h3> Color-Doppler ultrasound combined with brachytherapy applicator surface modifications may be used to enhance applicator conspicuity and aid with applicator placement and digitization. HDR brachytherapy needles may be modified for color-Doppler imaging via laser-etching or coating with a PMMA-based bone cement.

Verbal Instruction for Pelvic Floor Muscle Contraction among Healthy Young Males.

Teaching Pelvic Floor Muscle (PFM) contraction is a challenging task for clinicians and patients, as these muscles cannot be directly visualized. Thus, this study’s objective is to compare the effectiveness of six verbal instructions for contracting the PFM among young men, as observed with transabdominal ultrasound imaging. Thirty-five male physiotherapy students, mean age 25.9 ± 1.9 years, participated in the study. A 6 MHz 35-mm curved linear array ultrasound transducer (Mindray M5) was placed in the transverse plane, supra-pubically, and angled 15–30° from the vertical plane. During crook lying, participants received six verbal instructions for contracting the PFM, with bladder base displacement and endurance evaluated. Following the instructions, “squeeze your anus”, “shorten the penis”, and “elevate the scrotum”, over 91% of the participants performed a cranial (upward) bladder base displacement. During instruction six, “draw in”, which involves breathing, the PFM, and the transversus abdominis, only 25% performed cranial bladder base displacement (p < 0.001), and the endurance was the lowest (p < 0.001). Our findings suggest that several simple verbal instructions can be used for teaching PFM contraction to young males. Moreover, two instructions should be avoided: “draw in” and the general instruction “squeeze your PFM”, as they did not produce effective elevation of the bladder base.

Ocular ultrasonography for detection of posterior segment pathology in adult patients presenting with blurred vision

Background and objective: Ocular posterior segment lesions can affect individuals of both sexes at all ages. Such lesions can lead to serious manifestations such as retinal detachment and retinal hemorrhage, leading to permanent loss of eyesight. This study aimed to determine the association between age and gender and changes in ocular posterior segment based on ultrasonography findings. Methods: This prospective cross-sectional study included 50 patients with blurry vision who had been referred from ophthalmology outpatient clinics to the radiology department of Rizgary Teaching Hospital in Erbil, Kurdistan region in Iraq. Required data were collected using a researcher-designed questionnaire, and the patients were examined using a high resolution 7.5-10 MHz linear array ultrasound transducer. Results: The most frequent complications associated with ocular posterior segment pathologies were old vitreous hemorrhage (72%), posterior vitreous detachment (36%), and retinal detachment (34%). Diabetes and hypertension were the most frequent diseases associated with ocular posterior segment pathology. A significant association was seen between the patients' age with old vitreous hemorrhage (P = 0.003). A significant association was seen between the patients’ medical conditions with old vitreous hemorrhage and retinal detachment. There was no significant correlation between the patients’ gender and the studied ocular posterior segment pathologies. Conclusion: Age has a strong correlation with old vitreous hemorrhage, chronic medical conditions such as diabetes, and hypertension correlated with old vitreous hemorrhage and retinal detachment. Keywords: Ocular ultrasonography; Posterior segment pathology; Blurred vision; Age; Gender.

Talar-Cartilage Deformation and Spatiotemporal Gait Patterns in Individuals With and Those Without Chronic Ankle Instability.

Individuals with chronic ankle instability (CAI) present with alterations in the compositional structure of their talar articular cartilage. These alterations likely influence how the talar cartilage responds to the loading associated with activities of daily living, such as walking. Ultrasonography has emerged as an alternative imaging modality for assessing the amount of cartilage deformation in response to loading because it is clinically accessible and cost effective for routine measurements. To (1) compare talar-cartilage deformation in response to a standardized exercise protocol between those with and those without CAI and (2) examine the association between spatiotemporal walking gait parameters and cartilage deformation. Case-control study. Research laboratory. A volunteer sample of 24 participants with self-reported CAI (age = 23.2 ± 3.9 years, body mass index [BMI] = 25.1 ± 3.7 kg/m2) and 24 uninjured controls (age = 24.3 ± 2.9 years, BMI = 22.9 ± 2.8 kg/m2). Spatiotemporal walking gait was first assessed from 5 self-selected trials using an electronic walkway with data sampled at 120 Hz. An 8- to 13-MHz linear-array ultrasound transducer placed transversely in line with the medial and lateral malleoli captured 3 images before and after a standardized loading protocol consisting of 30 single- and double-limb squats, 2-minute single-limb balance, and 10 single-legged drops from a 40-cm-height box. After controlling for BMI, we found that the participants with CAI had greater deformation than the uninjured control participants (P = .034). No other between-groups differences were observed (P values > .05). No significant partial correlations were noted between talar-cartilage deformation and spatiotemporal gait parameters when controlling for BMI (P > .05). Individuals with CAI had greater talar-cartilage deformation in response to a standardized exercise protocol than control individuals. The amount of talar-cartilage deformation was not associated with the spatiotemporal walking gait.

Evaluation of the correlation of the new Ballard scoring with the ultrasonographic optical nerve sheath diameter and brain volume of preterm infants

BackgroundOptic nerve sheath diameter (ONSD) measurements with magnetic resonance imaging and ultrasonography in preterm infants are similar. AimWe measured ultrasonographic ONSD and calculated the brain volumes of preterm infants using two-dimensional cranial ultrasonography and explored the relationships thereof with gestational age, birth weight, head circumference, and new Ballard score. MethodThis prospective study included preterm infants admitted to the neonatal intensive care unit without intracranial pathology. Two images per eye were obtained from a linear array ultrasound transducer placed on the patient's superior eyelid. The ONSD was measured 3 mm behind the globe. The brain was considered an ellipsoid, and estimated absolute brain volumes were calculated by subtracting the volumes of the two lateral ventricles from the total brain volumes. ResultsA total of 143 preterm infants (male 74, female 69) included in the study. The mean gestational age of the study population was 29.7 weeks (23–36), and the mean birth weight was 1390 g (500–2850). There was a significant difference in ONSD between the male and female gender. A significant, strong, and positive correlation was found between ONSD measurements and gestational age (r 0.901, p < 0.001), new Ballard score (r 0.946, p < 0.001), birth weight, head circumference, and brain volumes. ConclusionOur results suggested that ONSD measurements are highly correlated with anthropometry, and it could be a promising bedside, non-invasive objective tool for the determination of exact gestational age postnatally along with the new Ballard score.

Forward-viewing estimation of 3D blood flow velocity fields by intravascular ultrasound: Influence of the catheter on velocity estimation in stenoses

Coronary artery disease is the most common type of cardiovascular disease, affecting > 18 million adults, and is responsible for > 365 k deaths per year in the U.S. alone. Wall shear stress (WSS) is an emerging indicator of likelihood of plaque rupture in coronary artery disease, however, non-invasive estimation of 3-D blood flow velocity and WSS is challenging due to the requirement for high spatial resolution at deep penetration depths in the presence of significant cardiac motion. Thus we propose minimally-invasive imaging with a catheter-based, 3-D intravascular forward-viewing ultrasound (FV US) transducer and present experiments to quantify the effect of the catheter on flow disturbance in stenotic vessel phantoms with realistic velocities and luminal diameters for both peripheral (6.33 mm) and coronary (4.74 mm) arteries. An external linear array ultrasound transducer was used to quantify 2-D velocity fields in vessel phantoms under various conditions of catheter geometry, luminal diameter, and position of the catheter relative to the stenosis at a frame rate of 5000 frames per second via a particle imaging velocimetry (PIV) approach. While a solid catheter introduced an underestimation of velocity measurement by > 20% relative to the case without a catheter, the hollow catheter introduced < 10% velocity overestimation, indicating that a hollow catheter design allowing internal blood flow reduces hemodynamic disturbance. In addition, for both peripheral and coronary arteries, the hollow catheter introduced < 3% deviation in flow velocity at the minimum luminal area compared to the control case. Finally, an initial comparison was made between velocity measurements acquired using a low frequency, catheter-based, 3-D intravascular FV US transducer and external linear array measurements, with relative error < 12% throughout the region of interest for a flow rate of 150 mL/min. While further system development is required, results suggest intravascular ultrasound characterization of blood flow velocity fields in stenotic vessels could be feasible with appropriate catheter design.

Corneal Lamb wave imaging for quantitative assessment of collagen cross-linking treatment based on comb-push ultrasound shear elastography

Keratoconus, a serious corneal disorder, often causes highly irregular astigmatism and different degrees of visual impairment. Riboflavin/UVA corneal collagen cross-linking(CXL) is currently approved for effective treatment of keratoconus by enhancing the mechanical strength of collagen fibers in the cornea. However, few methods are capable of quantitatively and non-destructively assessing the mechanical properties of the cornea before and after CXL treatments. This study developed a corneal viscoelasticity imaging method based on comb-push ultrasound shear elastography (CUSE) and implemented this method on a Verasonics™ Vantage 256 ultrasound open system with a high-frequency linear array ultrasound transducer. Push beams were generated by three teeth each consisting of 10 elements (working frequency = 10.41 MHz) for inducing Lamb wave propagation in the cornea, and then the system immediately switched to the plane wave imaging mode using 60 elements in the middle (working frequency = 18 MHz). This method can provide a high-resolution 2D Lamb wave velocity image overlapping with a B-mode image as well as quantitative viscoelasticity estimation according to experimentally obtained phase velocity dispersion of Lamb waves. The validation experiments were performed on ex vivo porcine corneas, and the accuracy of elasticity estimation was verified by a tensile test. The results showed that the shear elasticity increased and the viscosity decreased after CXL treatment. The shear elasticity results (reported as mean ± standard deviation) of one control group with no CXL treatment and three CXL-treated groups named as 10 min, 30 min, and 60 min groups according to UV irradiation time were 14.62 ± 3.38 kPa, 49.47 ± 3.63 kPa, 116.54 ± 23.99 kPa, and 197.89 ± 39.64 kPa, respectively, which was in agreement with the results of tensile tests. The ultrasound safety measurement indicated that this method could have acceptable safety, but further to ocular tissue and vision function. The study demonstrated the possibility of using a commercial ultrasound system to obtain high-resolution images of corneal mechanical properties as well as the ability to quantify changes induced by CXL treatment. Therefore, the proposed method could serve as a helpful tool in the studies related in corneal biomechanics.

Scaled reassigned spectrograms applied to linear transducer signals.

This study evaluates the applicability of scaled reassigned spectrograms (ReSTS) on ultrasound radio frequency data obtained with a clinical linear array ultrasound transducer. The ReSTS's ability to resolve axially closely spaced objects in a phantom is compared to the classical cross-correlation method with respect to the ability to resolve closely spaced objects as individual reflectors using ultrasound pulses with different lengths. The results show that the axial resolution achieved with the ReSTS was superior to the cross-correlation method when the reflected pulses from two objects overlap. A novel B-mode imaging method, facilitating higher image resolution for distinct reflectors, is proposed.

In Vivo Tumor Vascular Imaging with Light Emitting Diode-Based Photoacoustic Imaging System.

Photoacoustic (PA) imaging has shown tremendous promise for imaging tumor vasculature and its function at deeper penetration depths without the use of exogenous contrast agents. Traditional PA imaging systems employ expensive and bulky class IV lasers with low pulse repetition rate, due to which its availability for preclinical cancer research is hampered. In this study, we evaluated the capability of a Light-Emitting Diode (LED)-based PA and ultrasound (US) imaging system for monitoring heterogeneous microvasculature in tumors (up to 10 mm in depth) and quantitatively compared the PA images with gold standard histology images. We used a combination of a 7 MHz linear array US transducer and 850 nm excitation wavelength LED arrays to image blood vessels in a subcutaneous tumor model. After imaging, the tumors were sectioned and stained for endothelial cells to correlate with PA images across similar cross-sections. Analysis of 30 regions of interest in tumors from different mice showed a statistically significant R-value of 0.84 where the areas with high blood vessel density had high PA response while low blood vessel density regions had low PA response. Our results confirm that LED-based PA and US imaging can provide 2D and 3D images of tumor vasculature and the potential it has as a valuable tool for preclinical cancer research.

Classification of young healthy individuals with different exercise levels based on multiple musculoskeletal ultrasound images

Whether in sports or exercise rehabilitation, muscles are usually strengthened through exercise. In this process, the biological structure of the muscle is also changed subtly. However, it has not reported whether these changes can be reflected in ultrasonic images. Furthermore, it is a challenging and novel task to capture this nuance, and existing methods that use only one image are difficult to resolve it. Therefore, this study proposes a multiple images feature selection (MIFS) framework that combines information from multiple images, aiming to find an optimal feature set that can effectively distinguish between different exercise levels. In this study, the optimal feature set was obtained from seven differently operated musculoskeletal ultrasound images (MUI) of 107 healthy subjects (55 males, 52 females, age 21.0 ± 1.9 years) included 54 regular exercisers and 53 irregular exercisers by the MIFS framework. All ultrasound images are acquired in B-mode with an 8.5 MHz linear array ultrasound transducer. Finally, we obtain an optimal feature set consisting of 20 features, and the optimal classification accuracy exceeds the existing single-image-based method, up to 78.9 %. This preliminary study suggests nuance in muscle structure caused by different exercise levels can be captured by ultrasound images. What's more, MIFS can more accurately deal with complicated task of classifying between regular and irregular exercisers as well.

Three-dimensional clinical handheld photoacoustic/ultrasound scanner

Clinical 2D photoacoustic (PA) imaging can be easily implemented in a traditional ultrasound (US) system. However, 3D PA imaging is still preferable because 2D B-mode PA/US imaging suffers from low reproducibility and high-operator dependency. Here, we demonstrate a compact clinical handheld 3D PA/US scanner using an 1D linear array US transducer combined with a mechanical scanning stage working via a Scotch yoke mechanism. The entire scanner measures just 100 × 80 × 100 mm3 and weighs only 950 g, so it can easily be operated by hand. Blood vessels and hemoglobin oxygen saturation images of different parts of the human body (e.g., neck, wrist, thigh, and instep) have been successfully acquired. The system can potentially be used for clinical applications in fields such as oncology, dermatology, nephrology, and internal medicine.

Ultrasound Shear Wave Elastography to Assess Osteopathic Manipulative Treatment on the Iliocostalis Lumborum Muscle: A Feasibility Study.

To investigate the feasibility of ultrasound shear wave elastography (SWE) in assessing iliocostalis lumborum muscle changes after osteopathic manipulative treatment (OMT). Using a linear array ultrasound transducer (4-9 MHz), we prospectively measured the shear wave velocity (SWV) of bilateral iliocostalis lumborum muscles in 20 patients with low back somatic dysfunction and in 9 age-matched healthy volunteers. The SWV was measured in muscle relaxation and contraction in all participants and immediately before and after OMT in patients. We developed a muscle SWV rate [SWVcontraction - SWVrelaxation )/SWVrelaxation ] and an SWV improvement index [(SWVpre-OMT - SWVpost-OMT )/SWVpre-OMT ] for quantifying muscle contractibility and changes in muscle stiffness after OMT. Statistical analyses included an unpaired t test to analyze the difference in the muscle SWV between muscle relaxation and contraction and between somatic dysfunction and nonsomatic dysfunction in patients and healthy volunteers, a paired t test to examine the difference in the SWV and SWV rate before and after OMT, the intraclass correlation coefficient to test intraobserver and interobserver reliability, and Spearman rank correlation to analyze the correlation of changes in the SWV with manual osteopathic assessments. The mean ages of the patients with low back somatic dysfunction and the healthy volunteers were 28 and 26 years, respectively. The muscle SWV significantly differed between somatic dysfunction and nonsomatic dysfunction in patients and healthy volunteers, between muscle relaxation and contraction, and before and after OMT (P < .001). The SWV improvement index moderately correlated with manual osteopathic assessments (r = 0.68). The interobserver and intraobserver reliability for performing SWE was good (intraclass correlation coefficient, >0.8). Our results suggest that SWE is feasible for quantifying the change in muscle stiffness and contractibility after OMT.

Ultrasound shear wave elastography in assessment of skeletal muscle stiffness in senior volunteers

Purpose: The aim of the study was to evaluate the reliability of ultrasound shear wave elastography (SWE) to assess biceps brachii muscle (BBM) and quadriceps muscle (QM) stiffness in senior volunteers.Methods: Using a linear array ultrasound transducer (7 MHz), we prospectively measured shear wave velocity (SWV) of BBM and QM in passive joints (elbow and knee) flexion (90°) and extension (180°) in 19 senior volunteers by two operators. We developed SWV rate (SWVelbow-extension – SWVelbow-flexion)/SWVelbow-flexion to assess BBM contractibility. Statistical analysis included unpaired t-test to examine the difference in SWV of muscle between left vs right limbs, men vs women, and athletes vs nonathletes; Intraclass correlation coefficient (ICC) and violin plots for analyzing intra- and inter-observer reliability in performing SWE in muscles.Results: There was no significant difference in SWV between left vs right (flexion or extension), male vs female (flexion or extension), for BBM and QM, and athlete vs nonathlete extension for QM (all p > 0.05). The difference in SWV of BBM in elbow extension and in SWV rate between athlete and nonathlete was significant (p < 0.05). The difference in muscle SWV between joint flexion and extension was also significant (p < 0.05). Reliability in performing SWE of BBM and QM was good (ICC > 0.75).Conclusions: Our results suggest that ultrasound SWE is feasible in estimating BBM and QM stiffness in seniors with good reproducibility. SWV rate and SWV of the extended BBM representing muscle contractibility in athlete were higher than in nonathlete.

Triceps surae muscle–subtendon interaction differs between young and older adults

ABSTRACTBackground: Mechanical power generated via triceps surae muscle-tendon interaction during walking is important for walking performance. This interaction is made complex by distinct “subtendons” arising from the lateral and medial gastrocnemius (GAS) and soleus (SOL) muscles. Comparative data and our own in vivo evidence allude to a reduced capacity for sliding between adjacent subtendons compromising the Achilles tendon in old age. However, its unclear if and how these changes affect muscle contractile behavior.Objective: We investigated aging effects on triceps surae muscle-subtendon interaction using dual-probe ultrasound imaging during isolated muscle contractions. We hypothesized that, compared to young adults, older adults would have more uniform subtendon tissue displacements that are accompanied by anatomically consistent differences in GAS versus SOL muscle length change behavior.Materials and Methods: 9 younger subjects (age: 25.1 ± 5.6 years) and 10 older adult subjects (age: 74.3 ± 3.4 years) completed a series of ramped maximum isometric voluntary contractions at ankle angles spanning 0° (neutral) to 30° plantarflexion. Two linear array ultrasound transducers simultaneously recorded GAS and SOL fascicle kinematics and tissue displacements in their associated tendinous structures.Results: We revealed that older adults have more uniform subtendon tissue displacements that extend to anatomically consistent and potentially unfavorable changes in muscle contractile behavior – evidenced by smaller differences between gastrocnemius and soleus peak shortening during isometric force generation.Conclusions: These findings provide an important biomechanical basis for previously reported correlations between more uniform Achilles subtendon behavior and reduced ankle moment generation during waking in older adults.

Optic Nerve Sheath Diameter for Preterm Infants: A Pilot Study

Objective: In preterm infants, early diagnosis and management of a raised intracranial pressure (ICP) may be important to improve neurodevelopmental outcomes. While invasive ICP monitoring is not recommended, ultrasonography of the optic nerve sheath diameter (ONSD) could provide a noninvasive alternative to evaluate ICP. The objective of this pilot study was to document ranges of ONSD in preterm infants. Methods: This prospective cohort pilot evaluated preterm infants who were admitted to the neonatal intensive care unit without suspected raised ICP. Three images per eye were obtained from a 20–5 MHz linear array ultrasound transducer placed on the patient’s superior eyelid. The OSND was measured 3 mm behind the globe. A second ultrasonographer duplicated half of the scans. Multiple linear regression analysis was conducted for both right and left ONSD with corrected gestational age, weight, and head circumference as predictors. Lin’s concordance assessed interrater reliability. Results: In 12 preterm infants 114 scans were performed on both eyes. The median age was 33 weeks (corrected gestational age) with a range of 29–36 weeks. Corrected gestational age was the strongest predictor for ONSD, and preliminary measurements at each gestational age were established. Interrater reliability demonstrated substantial agreement (Q_c = 0.97). Conclusion: In preterm infants, ONSD strongly correlates with corrected gestational age. These data should be validated with other imaging modalities before abnormal ranges can be considered.

Sparsity-based photoacoustic image reconstruction with a linear array transducer and direct measurement of the forward model.

Photoacoustic (PA) imaging is an emerging imaging technique for many clinical applications. One of the challenges posed by clinical translation is that imaging systems often rely on a finite-aperture transducer rather than a full tomography system. This results in imaging artifacts arising from an underdetermined reconstruction of the initial pressure distribution (IPD). Furthermore, clinical applications often require deep imaging, resulting in a low-signal-to-noise ratio for the acquired signal because of strong light attenuation in tissue. Conventional approaches to reconstruct the IPD, such as back projection and time-reversal, do not adequately suppress the artifacts and noise. We propose a sparsity-based optimization approach that improves the reconstruction of IPD in PA imaging with a linear array ultrasound transducer. In simulation studies, the forward model matrix was measured from k-Wave simulations, and the approach was applied to reconstruct simulated point objects and the Shepp-Logan phantom. The results were compared with the conventional back projection, time-reversal approach, frequency-domain reconstruction, and the iterative least-squares approaches. In experimental studies, the forward model of our imaging system is directly measured by scanning a graphite point source through the imaging field of view. Experimental images of graphite inclusions in tissue-mimicking phantoms are reconstructed and compared with the back projection and iterative least-squares approaches. Overall these results show that our proposed optimization approach can leverage the sparsity of the PA images to improve the reconstruction of the IPD and outperform the existing popular reconstruction approaches.

What is the most effective verbal instruction for correctly contracting the pelvic floor muscles?

The purpose of the present study was to compare the effectiveness of four different verbal instructions in correctly contracting pelvic floor muscles (PFMs), examined as a displacement of the pelvic floor by transabdominal ultrasound. Fifty-six female undergraduate physiotherapy students, mean age 24.2 ± 2.5 years, participated in the study. A 6 MHz 35-mm curved linear array ultrasound transducer (Mindray M5) was placed in the transverse plane, suprapubically over the lower abdomen and angled at 15-30° from the vertical depending. The participants were randomly divided into two groups: posterior and anterior. Each group received four different verbal instructions as to how to correctly contract the PFMs. Only one verbal instruction differed between the groups: "squeeze the anus" (posterior group) compared with "stop the flow of urine" (anterior group). In the posterior group, 27 participants (90%) performed a correct contraction compared with 17 participants (65%) in the anterior group, thus demonstrating a statistically significant difference in favor of the "anus" instruction (P = 0.025). Forty-seven participants (84%) exhibited a downward movement during the verbal instruction combining transversus abdominis contractions with breathing, that is, "take a moderate breath in, let the breath out then draw in and lift your pelvic floor." Our findings suggest that the most effective verbal instruction for correctly contracting the PFMs among 56 physiotherapy students was the posterior instruction of "squeezing the anus." The majority (90%) of participants succeeded in correctly contracting the PFMs.