Linear Array Transducer Research Articles

Pattern synthesis for symmetric linear transducer array by bilinear factorization of Hankel matrices

We investigate the problem of designing an unequally spaced symmetric linear array with a minimum number of elements. For unequally spaced arrays, simultaneously tuning all the elements' positions and weights leads to a non-convex problem. Inspired by the fact that the matrix pencil method (MPM) can estimate the weights and positions of array elements from a Hankel matrix formed by samples of beampattern, we attack the design problem by finding the Hankel matrix fulfilling specifications with the minimum rank. Fortunately, the low-rank optimization can be addressed by nuclear norm relaxation. In the proposed approach, we minimize the nuclear norm of the Hankel matrix utilizing the low-rank matrix factorization-based augmented Lagrangian alternating direction method. Once the low-rank Hankel matrix is obtained, we finish the array design with the help of MPM. By finding the desired Hankel matrix with a minimum nuclear norm, the proposed approach avoids the NP-hard problem of simultaneously optimizing the weights and positions of elements. Moreover, the proposed method does not need a reference beampattern and makes no assumptions on element positions, making it more flexible in facing real-world problems. We compare the proposed approach with existing methods under different scenarios and prove its effectiveness.

Differences in ultrasound elevational beam width (slice thickness) between popular handheld devices

BackgroundHandheld ultrasound devices are increasingly used by medical professionals for bedside ultrasound-guided interventions. Especially for vascular access procedures, the width of the imaging plane, known as the slice thickness or elevational beam width is a prominent source for misinterpretation. A wide slice thickness can lead to the interpretation that 2 objects (i.e. needle and vessel) are on the same plane while in fact they are not and thereby negatively influencing the performance of in-plane ultrasound-guided interventions. Therefore, the beam profiles of three popular handheld US devices are tested and compared to a conventional US device. MethodsThe GE VScan, Philips Lumify and Butterfly IQ ​+ ​are tested using a slice phantom to determine the slice thickness. For comparison, a Philips Affiniti machine was investigated. Both linear and curved array settings were analyzed. In a slice phantom, a diffuse scattering plane at an angle of exactly 45° is scanned. For each imaging depth, the vertical height of the imaged rectangle corresponds to the slice thickness at that depth. Main resultsFor the linear array transducers, the focus depth ranges from 1.5 to 3.5 cm. At the focus depth, all transducers have a reasonable slice thickness of approximately 1 mm. More superficially, the slice thickness varies between 1 and 4 mm. The curved array probes have larger focus depths, ranging from 2.7 to 7.3 cm. The slice thickness at focus depth varies between 1.4 and 3.8 mm, but at 2 cm depth is even more than 5 mm. ConclusionsThe slice thickness of handheld ultrasound transducers varies between the different devices, and can be suboptimal for superficial in-plane ultrasound-guided interventions. The larger slice thickness of the curved array settings may complicate in-plane guidance. Handheld ultrasound users should be aware of the beam characteristics of their devices to optimize guidance for interventions.

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.

Super-Resolution Ultrasound Localization Microscopy Using High-Frequency Ultrasound to Measure Ocular Perfusion Velocity in the Rat Eye.

Imaging of the ocular vasculature can provide new insights into the pathophysiology of ocular diseases. This study proposes a novel high-frequency super-resolution ultrasound localization microscopy (SRULM) technique and evaluates its ability to measure in vivo perfusion changes in the rat eye at elevated intraocular pressure (IOP). A 38.4 MHz center frequency linear array transducer on a VisualSonics Vevo F2 imaging platform was used to collect high frame rate (1 kHz) radiofrequency data of the posterior rat eye following systemic microbubble contrast injection. Following clutter and spatiotemporal non-local means filtering, individual microbubbles were localized and tracked. The microbubble tracks were accumulated over 10,000 frames to generate vascular images quantifying perfusion velocity and direction. Experiments were performed using physiologic relevant controlled flow states for algorithm validation and subsequently performed in vivo on the rat eye at 10 mm Hg IOP increments from 10 to 60 mm Hg. The posterior vasculature of the rat eye, including the ophthalmic artery, long posterior ciliary arteries and their branches, central retinal artery and retinal arterioles and venules were successfully visualized, and velocities quantified at each IOP level. Significant reductions in arterial flow were measured as IOP was elevated. High-frequency SRULM can be used to visualize and quantify the perfusion velocity of the rat eye in both the retrobulbar and intraocular vasculature simultaneously. The ability to detect ocular perfusion changes throughout the depth of the eye may help elucidate the role ischemia has in the pathophysiology of ocular diseases such as glaucoma.

Regional Hypertrophy: The Effect of Exercises at Long and Short Muscle Lengths in Recreationally Trained Women.

The aim of the present study was to analyse the role of exercises' resistance profile in regional hypertrophy. Thirty-eight healthy women completed a 9-week resistance training program consisting of either 4 sets of 12 repetitions to volitional failure of inclined bicep curls (INC group) or preacher curls (PREA group), three times per week. Pre- and post-intervention muscle thickness was measured using B-mode ultrasound imaging with a linear-array transducer. Scan acquisition sites were determined by measuring 50%, 60% and 70% of the distance between the posterior crest of the acromion and the olecranon. Statistical significance was set at p < 0.05. No region of the INC group grew when comparing pre- to post-intervention. The 70% region of the PREA group grew significantly (muscle thickness increased from 2.7 ± 0.43 cm to 2.94 ± 0.44 cm). We found no growth differences between regions when analysing per group (p = 0.274), region (p = 0.571) or group*region (p = 0.367). Our results show that the distal region of the arm grows in response to the preacher curl that places the highest amount of strain in the range of motion in which the arm muscles are more elongated.

Quantitative Assessment of Tendon Backscatter Anisotropy in B-Mode Ultrasound

To test the anisotropy of human tendons in conventional B-mode ultrasound, we prospectively performed ultrasound scans of 40 normal patella tendons and 24 patella tendons with chronic tendinopathy in adults. We scanned all tendons in longitudinal orientation (parallel to tendon fibers) using a linear array transducer (8.5 MHz) with beam steering at 0°, 5°, 10°, 15° and 20°. We used ImageJ histogram analysis to process B-mode images offline for assessing backscatter as a function of angle, known as backscatter anisotropy, between normal tendons and the subcutaneous tissues and between normal tendons and tendons with tendinopathy. We compared the results using the slopes of linear regression lines drawn through the angle-dependent data, and we concluded that the tissue anisotropy was significantly different if the 95% confidence intervals of the line slopes for different tissues did not overlap. We observed significant differences between normal tendons and both the adjacent subcutaneous tissues and tendons with tendinopathy. However, the difference in the regression slopes between tendons with tendinopathy and the adjacent subcutaneous soft tissues was not significant. It appears that changes in anisotropic backscatter could be used to detect tendon abnormalities and in assessing the significance of disease and the effectiveness of therapy.

Ultrasonographic and Doppler characteristics of corpus luteum luteogenesis in Remonta Argentino jennies

The corpus luteum (CL) plays a crucial role in maintaining pregnancy and preparing the uterus for implantation of the fertilized egg. Transrectal Doppler ultrasonography of the ovary can be used as a diagnostic tool to assess the reproductive status and functionality of the CL. Our aim was to characterize size, echogenicity and degree of vascularization of the corpus luteum over five days after ovulation in Remonta Argentino jennies. Five healthy cycling jennies aged 9 to 14 years were monitored transrectally using the MyLabTMOne ultrasound (ESAOTE, InMed, Argentina) with a 5-10 MHz linear array transducer. After a preovulatory follicle was detected, jennies were monitored daily for ovulation (day 0) and ultrasonographic evaluation of the CL until day 5. Two ovulations and the respective CL formation were analyzed in each jenny (n=10 CL). Size and echogenicity were evaluated using B mode and CL vascularization using the Doppler-color function, with a pulse repetition frequency of 1.2 MHz. All ultrasound examinations were video recorded for analysis. Adobe Premiere Pro CS6® was used to collect three images from each video where the largest area of the CL and the highest Doppler signal were detected. Image J. version 1.52i software (National Institute of Health, USA) was used to analyze images and to determinethe area, number of gray pixels (echogenicity) and color area within the CL in Doppler mode. The average value from the three images was used to determine CL size (area in cm2), echogenicity (average gray pixel intensity) and the proportion of vascularized area (AV; area with blood flow/total CL area x 100). Spearman's test was used to correlate the variables and the changes recorded between days 1 and 5 of diestrus. The results obtained on each day were the following (values expressed as mean±SEM): Day 0: area 3.26±0.5; echogenicity 84.2±4.86; AV 5.54±1.75; Day 1: area 4.86±0.32; echogenicity 91.25±7.42; AV 1.84±0.26; Day 2: area 4.83±0.41; echogenicity 88.72±7.89; AV 3.51±0.81; Day 3: area 4.64±0.43; echogenicity 89.69±4.9; AV 4.54±0.67; Day 4: area 4.38±0.48; echogenicity 97.78±7.61; AV 5.8±1.06; Day 5: area 4.24±0.49; echogenicity 89.18±9.25; AV 8.66±1.15. No statistical correlation was observed either between variables or with the day of diestrus (p>0.05). Blood samples were collected daily between day 0 and day 5 of diestrus and progesterone determinations are ongoing. Our results contribute to a better understanding of CL formation in Remonta Argentino donkeys that could potentially be used to determine CL age and function.

(208) Coital Positions and Clitoral Blood Flow: A Biomechanical and Sonographic Analysis

Abstract Introduction The purported benefits of various coital positions are described in numerous magazines, books, and public forums. However, there is little scientific research that evaluates the association between different coital positions and the ability to produce female orgasm. Objective To create biomechanical models of five coital positions, and evaluate the degree of contact and forces against the clitoris. To evaluate clitoral blood flow before and after engaging in these positions. Methods Biomechanical models were rendered of a male and female pelvis in the following coital positions: face-to-face/female above, sitting/face-to-face, face-to-face/male above (with and without pillow), and kneeling/rear entry. The thrusting force and gravitational force were estimated for the pelvis(es) providing the main forces. The areas of contact between the pelvises were identified and highlighted. Sonography of the clitoris was performed before and after a healthy volunteer couple engaged in each position, using a Philips Lumify™ ultrasound (Koninklijke Philips N.V., Amsterdam, Netherlands) with a L12-4 linear array transducer (4-12 MHz). Results The biomechanical models for each position, with the exception of kneeling/rear entry, reveal a large amount of contact with the clitoris. Clitoral blood flow increased after engaging in each position except for kneeling/rear entry. Positions in which the gravitational force of the thrusting partner was in the same direction of (and thereby augmenting) the thrusting force resulted in intense clitoral blood flow (face-to-face/female above, and face-to-face/male above). Augmenting the face-to-face/male above position with a pillow generated a component of the male pelvic gravitational force in the direction of the clitoris; this resulted in more blood flow to all components of the cavernous body. Conclusions From a biomechanical perspective, different coital positions vary in their potential to stimulate the clitoris. These positions lead to variable increases in clitoral blood flow, concordant with our biomechanical models. Disclosure No

(210) Clitoral Blood Flow After Use of Gel Containing L-Arginine and L-Citrulline

Abstract Introduction L-arginine and its precursor, l-citrulline, are two amino acids involved in the production of nitric oxide (NO); as a result, they increase blood flow and have been used to treat male sexual dysfunction (Alatas and Yagci, 2004). Some lubricants and gels contain l-arginine and are applied directly to the genital area to increase blood flow. Although these products have been evaluated subjectively through patient reports of increased warmth, arousal, and orgasm, to our knowledge, they have not been evaluated quantitatively in women. Moreover, the effect of gels combining both l-arginine and l-citrulline have not been reported in the medical literature. Objective To evaluate whether a topical gel containing l-arginine and l-citrulline increases blood flow to the clitoris. Methods Sonography of the clitoris was performed on a healthy 32-year-old volunteer before and after applying the gel externally to the vulva. The “before” scans were obtained using a neutral ultrasound gel (without l-arginine or l-citrulline). This allowed us to verify that the observations were due to the active ingredients of the gel, and not from massage associated with its application. Control images without gel could not be obtained, since acquisition of ultrasound images requires ultrasound gel in order to reduce acoustic impedance. The scans were obtained with a Philips Lumify™ ultrasound (Koninklijke Philips N.V., Amsterdam, Netherlands) with a L12-4 linear array transducer (4-12 MHz). Clitoral blood flow was assessed qualitatively (color Doppler images), as well as quantitatively (peak systolic velocity, end diastolic velocity, and resistive index of the deep artery of the clitoris). Results Blood flow to the clitoris increased after application of the gel containing l-arginine and l-citrulline at both evaluated time points. The maximum PSV of the deep artery of the clitoris also increased from 6.2 cm/s (before), to 8.6 cm/s (5 minutes) and 13.9 cm/s (15 minutes). The maximum EDV of the deep artery of the clitoris increased from 1.4 cm/s (before), to 1.7 cm/s (5 minutes) and 9.5 cm/s (15 minutes). The RI was 0.8 before and at 5 minutes. After 15 minutes, the RI decreased to 0.3, explained by a disproportional increase in EDV compared to PSV. Conclusions The results of this pilot study suggest that clitoral blood flow increases with the use of a gel containing l-arginine and l-citrulline. These findings can help clinicians inform patients with female sexual dysfunction. Difficulty achieving clitoral stimulation is a major cause of sexual dysfunction. Clinicians can use these findings to counsel patients about using gels to increase clitoral blood flow. Disclosure No

Nanoarchitectonics of ethylene propylene diene monomer (EPDM) composites reinforced with Cu–Al–Zn-alloy for ultrasonic array transducers’ fabrication

In response to the continuous demand for industry progress and the need for low-cost alternative materials that have superior properties than the present ones, a new coupling agent was used to treat composites, which were used as new backing materials in ultrasonic array transducers. In array transducers, back-echo reverberation to the piezoelectric elements occurs, so backing materials are critical in reducing these echoes. The Cu–Al–Zn-alloy was treated with a coupling agent before being incorporated into ethylene propylene diene monomer (EPDM) composites. Cu–Al–Zn-alloy/EPDM composites were assessed using rheometric, mechanical, and morphological properties. The division of cu-alloy at the EPDM matrix was visualized using a scanning electron microscope (SEM). TGA and DSC techniques were used to study the thermal characterization of the EPDM composites. As a result, the treated Cu-alloy improved the thermal, mechanical, and morphological characteristics of EPDM composites. Ultrasonic measurements ensured the composites' effectiveness as backing materials in ultrasonic array transducers. Furthermore, the composites’ properties were similar to those of the most commonly used epoxy/tungsten backing material. Finally, linear ultrasonic-phased array transducers were fabricated using Cu–Al–Zn-alloy/EPDM composites. They had a low signal-to-noise ratio, and this ensured the effectiveness of Cu–Al–Zn-alloy/EPDM composites as backing materials.

Large-Array Deep Abdominal Imaging in Fundamental and Harmonic Mode.

Deep abdominal images suffer from poor diffraction-limited lateral resolution. Extending the aperture size can improve resolution. However, phase distortion and clutter can limit the benefits of larger arrays. Previous studies have explored these effects using numerical simulations, multiple transducers, and mechanically swept arrays. In this work, we used an 8.8-cm linear array transducer to investigate the effects of aperture size when imaging through the abdominal wall. We acquired channel data in fundamental and harmonic modes using five aperture sizes. To avoid motion and increase the parameter sampling, we decoded the full-synthetic aperture data and retrospectively synthesized nine apertures (2.9-8.8 cm). We imaged a wire target and a phantom through ex vivo porcine abdominal samples and scanned the livers of 13 healthy subjects. We applied bulk sound speed correction to the wire target data. Although point resolution improved from 2.12 to 0.74 mm at 10.5 cm depth, contrast resolution often degraded with aperture size. In subjects, larger apertures resulted in an average maximum contrast degradation of 5.5 dB at 9-11 cm depth. However, larger apertures often led to visual detection of vascular targets unseen with conventional apertures. An average 3.7-dB contrast improvement over fundamental mode in subjects showed that the known benefits of tissue-harmonic imaging extend to larger arrays.

Assessment of Transarterial Chemoembolization Using Super-resolution Ultrasound Imaging and a Rat Model of Hepatocellular Carcinoma.

Hepatocellular carcinoma (HCC) is a highly prevalent form of liver cancer diagnosed annually in 600,000 people worldwide. A common treatment is transarterial chemoembolization (TACE), which interrupts the blood supply of oxygen and nutrients to the tumor mass. The need for repeat TACE treatments may be assessed in the weeks after therapy with contrast-enhanced ultrasound (CEUS) imaging. Although the spatial resolution of traditional CEUS has been restricted by the diffraction limit of ultrasound (US), this physical barrier has been overcome by a recent innovation known as super-resolution US (SRUS) imaging. In short, SRUS enhances the visible details of smaller microvascular structures on the 10 to 100 µm scale, which unlocks a host of new clinical opportunities for US. In this study, a rat model of orthotopic HCC is introduced and TACE treatment response (to a doxorubicin-lipiodol emulsion) is assessed using longitudinal SRUS and magnetic resonance imaging (MRI) performed at 0, 7 and 14 d. Animals were euthanized at 14 d for histological analysis of excised tumor tissue and determination of TACE response, that is, control, partial response or complete response. CEUS imaging was performed using a pre-clinical US system (Vevo 3100, FUJIFILM VisualSonics Inc.) equipped with an MX201 linear array transducer. After administration of a microbubble contrast agent (Definity, Lantheus Medical Imaging), a series of CEUS images were collected at each tissue cross-section as the transducer was mechanically stepped at 100 μm increments. SRUS images were formed at each spatial position, and a microvascular density metric was calculated. Microscale computed tomography (microCT, OI/CT, MILabs) was used to confirm TACE procedure success, and tumor size was monitored using a small animal MRI system (BioSpec 3T, Bruker Corp.). Although there were no differences at baseline (p > 0.15), both microvascular density levels and tumor size measures from the complete responder cases at 14 d were considerably lower and smaller, respectively, than those in the partial responder or control group animals. Histological analysis revealed tumor-to-necrosis levels of 8.4%, 51.1% and 100%, for the control, partial responder and complete responder groups, respectively (p < 0.005). SRUS imaging is a promising modality for assessing early changes in microvascular networks in response to tissue perfusion-altering interventions such as TACE treatment of HCC.

Precise Estimation of Intravascular Pressure Gradients.

This study presents a method for noninvasive pressure gradient estimation, which allows the detection of small pressure differences with higher precision compared to invasive catheters. It combines a new method for estimating the temporal acceleration of the flowing blood with the Navier-Stokes equation. The acceleration estimation is based on a double cross-correlation approach, which is hypothesized to minimize the influence of noise. Data are acquired using a 256-element, 6.5-MHz GE L3-12-D linear array transducer connected to a Verasonics research scanner. A synthetic aperture (SA) interleaved sequence with 2 ×12 virtual sources evenly distributed over the aperture and permuted in emission order is used in combination with recursive imaging. This enables a temporal resolution between correlation frames equal to the pulse repetition time at a frame rate of half the pulse repetition frequency. The accuracy of the method is evaluated against a computational fluid dynamic simulation. Here, the estimated total pressure difference complies with the CFD reference pressure difference, which yields an R -square of 0.985 and an RMSE of 3.03 Pa. The precision of the method is tested on experimental data, measured on a carotid phantom of the common carotid artery. The volume profile used during measurement was set to mimic flow in the carotid artery with a peak flow rate of 12.9 mL/s. The experimental setup showed that the measured pressure difference changes from -59.4 to 31 Pa throughout a single pulse cycle. This was estimated with a precision of 5.44% (3.22 Pa) across ten pulse cycles. The method was also compared to invasive catheter measurements in a phantom with a 60% cross-sectional area reduction. The ultrasound method detected a maximum pressure difference of 72.3 Pa with a precision of 3.3% (2.22 Pa). The catheters measured a maximum pressure difference of 105 Pa with a precision of 11.2% (11.4 Pa). This was measured over the same constriction and with a peak flow rate of 12.9 mL/s. The double cross-correlation approach revealed no improvement compared to a normal differential operator. The method's strength, thus, lies primarily in the ultrasound sequence, which allows precise and accurate velocity estimations, at which acceleration and pressure differences can be acquired.

Improved Magneto-Acousto-Electrical Computed Tomography (MAE-CT) With Multi-Angle Plane Wave Excitation.

As a tissue conductivity imaging method, magneto-acousto-electric tomography (MAET) has the advantage of high axial spatial resolution compared with traditional electrical impedance imaging methods. However, it has the problems of difficulty in imaging targets with irregular conductivity distribution and poor lateral spatial resolution. Although the rotation-based MAET method can partly solve the irregular target problem, there is still a poor imaging signal-to-noise ratio (SNR) problem. Our previous study established a framework of an innovative MAET method, which has a very similar imaging theory and reconstruction algorithm to those of computed tomography (CT). Therefore, we name the method magneto-acoustic-electric computed tomography (MAE-CT). This paper proposes an improved implementation of MAE-CT based on multi-angle plane wave excitation. This method combines the electronic steering of the linear array transducer with the mechanical rotation to increase the number of projection angles while keeping the imaging complexity. In this study, we first established a finite element simulation model to verify the method's feasibility. Then phantom experiments were conducted to systematically investigate the performance of the proposed method. Finally, in vitro liver tissue experiment was conducted to further explore the feasibility of the method. The experimental results show that our method improves both the SNR and spatial resolution of the reconstructed image. For the phantom results, this method can detect conductivity of 0.67 S/m in an area with a size of 2 mm. To the best of our knowledge, this is the best result of spatial resolution available for MAET.

Point-of-Care Ultrasound: A Review of Ultrasound Parameters for Predicting Difficult Airways.

Airway management remains a crucial part of perioperative care. The conventional approach to assessing potentially difficult airways emphasizes the LEMON method, which looks for and evaluates the Mallampati classification, signs of obstruction, and neck mobility. Clinical findings help predict a higher likelihood of difficult tracheal intubation, but no clinical result reliably excludes difficult intubation. Ultrasound as an adjunct to clinical examination can provide the clinician with a dynamic anatomical airway assessment, which is impossible with clinical examination alone. In the hands of anesthesiologists, ultrasound is becoming more popular in the perioperative period. This method is particularly applicable for identifying proper endotracheal tube positioning in specific patient populations, such as those who are morbidly obese and patients with head and neck cancer or trauma. The focus is on identifying the normal anatomy, correctly positioning the endotracheal tube, and refining the parameters that predict difficult intubation. Several ultrasound measurements are clinical indicators of difficult direct laryngoscopy in the literature. A meta-analysis revealed that the distance from the skin to the epiglottis (DSE) is most associated with a difficult laryngoscopy. An ultrasound of the airway could be applied in routine practice as an adjunct to the clinical examination. A full stomach, rapid sequence intubation, gross visual anatomical abnormalities, and restricted neck flexibility prevent using ultrasound to assess the airway. The airway evaluation is performed with a linear array transducer of 12-4 MHz, with the patient in the supine position, with no pillow, and with the head and neck in a neutral position. The central axis of the neck is where the ultrasound parameters are measured. These image acquisitions guide the standard ultrasound examination of the airway.

High-Resolution Ultrasound Characterization of Local Scattering in Cancer Tissue.

Ultrasound (US) has afforded an approach to tissue characterization for more than a decade. The challenge is to reveal hidden patterns in the US data that describe tissue function and pathology that cannot be seen in conventional US images. Our group has developed a high-resolution analysis technique for tissue characterization termed H-scan US, an imaging method used to interpret the relative size of acoustic scatterers. In the present study, the objective was to compare local H-scan US image intensity with registered histologic measurements made directly at the cellular level. Human breast cancer cells (MDA-MB 231, American Type Culture Collection, Manassas, VA, USA) were orthotopically implanted into female mice (N=5). Tumors were allowed to grow for approximately 4 wk before the study started. In vivo imaging of tumor tissue was performed using a US system (Vantage 256, Verasonics Inc., Kirkland, WA, USA) equipped with a broadband capacitive micromachined ultrasonic linear array transducer (Kolo Medical, San Jose, CA, USA). A 15-MHz center frequency was used for plane wave imaging with five angles for spatial compounding. H-scan US image reconstruction involved use of parallel convolution filters to measure the relative strength of backscattered US signals. Color codes were applied to filter outputs to form the final H-scan US image display. For histologic processing, US imaging cross-sections were carefully marked on the tumor surface, and tumors were excised and sliced along the same plane. By use of optical microscopy, whole tumor tissue sections were scanned and digitized after nuclear staining. US images were interpolated to have the same number of pixels as the histology images and then spatially aligned. Each nucleus from the histologic sections was automatically segmented using custom MATLAB software (The MathWorks Inc., Natick, MA, USA). Nuclear size and spacing from the histology images were then compared with local H-scan US image features. Overall, local H-scan US image intensity exhibited a significant correlation with both cancer cell nuclear size (R2 > 0.27, p < 0.001) and the inverse relationship with nuclear spacing (R2 > 0.17, p < 0.001).

Accuracy of Shoulder Ultrasound for Diagnosis of Rotator Cuff Pathologies

To assess accuracy of shoulder ultrasound (USG) for diagnosis of rotator cuff pathologies. Seventy- four adult patients in age range of 30-80 years with rotator cuff pathologies of either gender were subjected to USG taken with Philips IU22 and a 5-12 MHz linear array transducer. All tendons were examined and grayscale 2D USG images were stored. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) was measured. USG findings showed intact supraspinatus tendons in 36 and 32, full tear in 8 and 10, partial tear in 2 and 7 and tendinosis in 28 and 25 cases respectively. Statistical analysis showed non- significant difference (P&gt;0.05). USG findings showed intact infraraspinatus tendons in 45 and 41, full tear in 0 and 7, partial tear in 3 and 10 and tendinosis in 26 and 16 cases respectively. Statistical analysis showed significant difference (P&lt;0.05). USG findings showed intact biceps tendons in 50 and 48, full tear in 2 and 3, partial tear in 4 and 4 and tendinosis in 18 and 19 cases respectively. Statistical analysis showed non- significant difference (P&gt;0.05). A high accuracy, sensitivity, specificity, PPV and NPV was observed with USG in diagnosis of supraspinatus tendon, infraspinatus tendon, biceps tendons, subcapularis tendons. USG found to be effective in assessment of rotator cuff pathologies having high sensitivity, specificity, positive predictive and negative predictive values.

Variability of Common Carotid Intima-media Thickness Measured using B-mode and M-mode Ultrasound Imaging

Background: Common carotid artery intima-media thickness (cIMT) has been associated with cardiovascular diseases, including stroke and coronary heart disease. There is a limited number of studies that specifically address the variability of ultrasound imaging modes in measuring cIMT. Therefore, this study aimed to assess the agreement-level and inter-observer reproducibility of cIMT measurements using B-mode and M-mode.&#x0D; Materials and Methods: B-mode and M-mode ultrasound imaging were used in measuring cIMT of healthy subjects using linear-array transducer. Inter-imaging mode agreement and inter-observer reproducibility of B-mode and M-mode were assessed using Intraclass correlation coefficient (ICC). Differences in cIMT measurements between imaging modes and observers were determined using paired t-test&#x0D; Results: There was significant difference between B-mode and M-mode in measuring cIMT (mean difference (MD), 0.03 mm, 95% CI 0.02 - 0.05, p&lt;0.001). Intra-imaging mode agreement was poor with ICC of 0.39. Inter-observer reproducibility of cIMT measured using B-mode and M-mode were good and moderate, respectively, (B-mode ICC of 0.76, 95% CI 0.64 - 0.84, p&lt;0.01; M-mode ICC of 0.68, 95% CI 0.52 - 0.78, p&lt;0.01). No significant difference between the two observers in measuring cIMT measured using B-mode or M-mode (B-mode p=0.3; M-mode p=0.4). &#x0D; Conclusion: There was a significant difference and poor intra-imaging mode agreement between B-mode and M-mode in measuring cIMT. B-mode showed higher inter-observer reproducibility of cIMT measurement than M-mode. Further studies investigating the variability and agreement between ultrasound imaging modes of patients with thickened cIMT are required.

Detecting Early Ocular Choroidal Melanoma Using Ultrasound Localization Microscopy.

Ocular choroidal melanoma (OCM) is the most common ocular primary malignant tumor in adults, and there is an increasing emphasis on its early detection and treatment worldwide. The main obstacle in early detection of OCM is its overlapping clinical features with benign choroidal nevus. Thus, we propose ultrasound localization microscopy (ULM) based on the image deconvolution algorithm to assist the diagnosis of small OCM in early stages. Furthermore, we develop ultrasound (US) plane wave imaging based on three-frame difference algorithm to guide the placement of the probe on the field of view. A high-frequency Verasonics Vantage system and an L22-14v linear array transducer were used to perform experiments on both custom-made modules in vitro and a SD rat with ocular choroidal melanoma in vivo. The results demonstrate that our proposed deconvolution method implement more robust microbubble (MB) localization, reconstruction of microvasculature network in a finer grid and more precise flow velocity estimation. The excellent performance of US plane wave imaging was successfully validated on the flow phantom and in an in vivo OCM model. In the future, the super-resolution ULM, a critical complementary imaging modality, can provide doctors with conclusive suggestions for early diagnosis of OCM, which is significant for the treatment and prognosis of patients.

Spontaneous Bilateral Rectus Abdominis Rhabdomyolysis in a 24-Year Old Male Following Intense Physical Activity in a Sub-Urban Nigerian Town: A Case Report

Introduction: Exercise induced Rhabdomyolysis is a syndrome characterised by disintegration of the skeletal muscles and release of toxic intracellular contents into the plasma. It can be precipitated by strenuous exercise and its diagnosis can easily be missed by physicians. Soft tissue ultrasonography is an invaluable tool for evaluating patients with rhabdomyolysis especially in sub Saharan Africa where sophisticated imaging modalities like magnetic resonance imaging (MRI) and computed tomographic scanners are not readily available. Ultrasonography in this case is the commonly available modality. It is cheap and easier to use. It can aid in the diagnosis of suspected cases, help to determine extent of the disease, identify associated complications and also for monitoring disease progression. Spontaneous rhabdomyolysis following exercise has not been previously reported in our environment. Objectives: To report a case of exercise induced rhabdomyolysis in a 24 year old male patient. To highlight the importance of ultrasound in evaluating patients with rhabdomyolysis, describe the notable ultrasound findings and review relevant existing literature on this condition. Case Report: A 24 year old male with spontaneous rhabdomyolysis of the infra-umbilical segment of both recti abdominis muscles, who presented to a private ultrasound facility in Agbor, Delta state, Nigeria. His symptoms were; lower abdominal pain made worse with movements, and passage of dark red urine which developed spontaneously following a week history of intense physical exercise at a gymnasium. An ultrasound scanner of the Toshiba Medical systems Corp Model 2016 (Xario 100) with a 7 to 12 MHz linear array transducer was used to scan both recti abdominis muscles in different planes. Abnormal findings were noted involving the infra umbilical segment of both abdominal recti muscle belly. Notable findings were thickening of the muscle fascia, blurring of the fat planes, fat stranding, disorganization of the normal architectural pattern of the fibres as well as presence of hypoechoic lesions within the affected muscle segment. The images were frozen and the sonograms were acquired and saved. Conclusion: Ultrasonography is an indispensable tool for evaluating patients with exercise induced spontaneous rhabdomyolysis. This case study is of immense significance in developing affordable methods of image based diagnosis and investigation of rhabdomyolysis that also aids in standard clinical, laboratory and histopathological studies of the condition.