Evaluation of skeletal muscle elasticity using color Doppler shear wave imaging.

PURPOSE: This study aimed to (1) assess the precision and reproducibility of color Doppler shear wave imaging (CD SWI) by comparing it with shear wave elastography (SWE) via elasticity phantom measurements, and (2) investigate the potential clinical applications of CD SWI in the upper limb muscles by assessing the reproducibility of skeletal muscle elasticity evaluations. METHODS: Four elastography phantoms of different stiffness (6.0-7.5 wt%) were used to assess the precision and reproducibility of CD SWI (compared with SWE) at depths. Typical upper limb muscles of 24 men were also assessed for this comparison. RESULTS: At superficial depths (0-2 cm), the phantom measurements obtained using CD SWI and SWE were similar at all levels of stiffness. Furthermore, both methods were highly reliable, with almost perfect intra- and inter-operator reliabilities. At greater depths (2-4 cm), measurements obtained using both methods were similar at all stiffness levels. Although standard deviations (SDs) of the phantom measurements obtained using both methods at lower stiffness were similar, those at higher stiffness were different. The SD of the CD SWI measurements was < 50% of that of the SWE measurements. However, both methods were highly reliable in the phantom test, with almost perfect intra- and inter-operator reliabilities. The intra- and inter-operator reliabilities of the shear wave velocity measurements for typical muscles of the upper limbs were also substantial in clinical settings. CONCLUSION: CD SWI is a valid method for measuring elasticity, with precision and reliability as high as those of SWE.

Prevalence of systemic and local risk factors for pulmonary non-tuberculous mycobacterial disease in Japan: a single-institution study.

Objective: To identify the prevalence of risk factors for pulmonary non-tuberculous mycobacterial (NTM) disease in a Japanese population. Patients and Methods: We reviewed 337 consecutive Japanese patients (210 women) with pulmonary NTM disease, including 225 patients with Mycobacterium avium complex (MAC) disease (95.8%) at our hospital during 2006-2017. We calculated the prevalence of risk factors reported in Western countries among mycobacterial species. Results: Pulmonary MAC disease cases comprised 78.2% of pulmonary NTM patients in their 40s, increasing to 100% at age ≥80 years. Body mass index (BMI) was <18.5 in approximately 40% of patients, which was significantly higher than the prevalence of underweight in the Japanese population. The percentage of male heavy smokers (Brinkman index ≥600) was 58.2% of pulmonary NTM disease and was high for all mycobacterial species. In pulmonary MAC disease, systemic factors were observed in the order of malignant tumors (other than lung cancer), diabetes, rheumatoid arthritis, and tuberculosis. Local factors were observed in the order of bronchiectasis, chronic obstructive pulmonary disease, lung cancer, and bronchial asthma. Conclusion: The risk factors reported in Western countries were relatively highly prevalent among Japanese pulmonary NTM disease patients. This observation may help elucidate disease onset mechanisms.

The Japan Society of Ultrasonics in Medicine guidelines on non-mass abnormalities of the breast.

It is possible to appropriately diagnose non-mass abnormalities by elucidating ultrasound non-mass abnormality findings and sharing the concept. If non-mass abnormalities can be diagnosed early, the number of curable cases could increase, leading to fewer breast cancer deaths. The Japan Society of Ultrasonics in Medicine (JSUM) Terminology/Diagnostic Criteria Committee has classified non-mass abnormalities into five subtypes: hypoechoic area in the mammary gland, abnormalities of the ducts, architectural distortion, multiple small cysts, and echogenic foci without a hypoechoic area. We herein define the findings for each of these subtypes and present a summary of the JSUM guidelines on non-mass abnormalities of the breast generated based on those findings.

Acoustic radiation force impulse-induced lung hemorrhage: investigating the relationship with peak rarefactional pressure amplitude and mechanical index in rabbits.

PURPOSE: The safety of acoustic radiation force impulse (ARFI) elastography, which applies higher acoustic power with a longer pulse duration (PD) than conventional diagnostic ultrasound, is yet to be verified. We assessed the ARFI-induced lung injury risk and its relationship with peak rarefactional pressure amplitude (PRPA) and mechanical index (MI). METHODS: Eighteen and two rabbits were included in the ARFI (0.3-ms push pulses) and sham groups, respectively. A 5.2-MHz linear probe was applied to the subcostal area and aimed at both lungs through the liver for 30 ARFI emissions. The derated PRPA varied among the six ARFI groups-0.80 MPa, 1.13 MPa, 1.33 MPa, 1.70 MPa, 1.91 MPa, and 2.00 MPa, respectively. RESULTS: The occurrence of lung hemorrhage and the mean lesion area among all samples in the seven groups were 0/6, 0/6, 1/6 (1.7 mm2), 4/6 (8.0 mm2), 4/6 (11.2 mm2), 5/6 (23.8 mm2), and 0/4 (sham), respectively. Logistic regression analysis showed that derated PRPA was significantly associated with lung injury occurrence (odds ratio: 207, p < 0.01), with the threshold estimated to be 1.1 MPa (MI, 0.5). Spearman's rank correlation showed a positive correlation between derated PRPA and lesion area (r = 0.671, p < 0.01). CONCLUSION: This study demonstrated that the occurrence and severity of ARFI-induced lung hemorrhage increased with a rise in PRPA under clinical conditions in rabbits. This indicates a potential risk of lung injury due to ARFI elastography, especially when ARFI is unintentionally directed to the lungs during liver, heart, or breast examinations.

Spontaneous regression of lymphovascular invasion and metastasis of malignant melanoma: ultrasound findings.

This report presents a case of malignant melanoma in a 40-year-old male who underwent resection of the tumor in his right ankle. Eleven months after the resection, a subcutaneous mass was observed on his right femur. Ultrasound examination revealed a hypoechoic tubular structure in the right thigh, with a small amount of blood flow in the lesion. Using ultrasound and fine-needle aspiration, the patient was diagnosed with metastasis and lymphovascular invasion of malignant melanoma. Treatment with an immune checkpoint inhibitor was originally scheduled, but the lesion disappeared spontaneously after the fine-needle aspiration.

The effect of attenuation inside the acoustic traps on the configuration of vertical artifacts in lung ultrasound: an experimental study with simple models.

PURPOSE: Using simple experimental models for lung ultrasound, we evaluated the relationship of the attenuation inside the sources of vertical artifacts to the echo intensity and attenuation of artifacts. METHODS: As sources of artifacts, we made 10 different hemispherical gel objects with two different mediums (pure agar or agar containing graphite with an attenuation coefficient of 0.5 dB/cm · MHz) and five different diameters (3.6, 5.6, 7.5, 9.5, or 11.4 mm). Ten of each hemispherical gel object were prepared for the statistical analyses. Each object was placed onto a chest wall phantom as the plane of the hemisphere was placed in an upward position. The echo intensity and attenuation of the artifact generated from each object was measured and compared. RESULTS: For all sizes, the intensity and attenuation of the artifacts in the objects made of agar containing graphite were significantly lower and larger, respectively, than those in the objects made of pure agar. In the objects containing graphite, the intensity decreased when the frequency was changed from 5 to 9 MHz. CONCLUSION: Based on this experiment, assessing the intensity and attenuation of vertical artifacts may help estimate the physical composition of sources of vertical artifacts in lung ultrasound.

Assessment of the risk of disease transmission during fine-needle aspiration cytology under ultrasound guidance by visualization of droplet and aerosol formation.

PURPOSE: Fine-needle aspiration cytology (FNAC) under ultrasound guidance is clinically useful, but there is a risk of spreading infection by generating droplets of contaminated fluids during the procedure. Risk assessment to better control infection remains to be established. The aim of this study was to estimate infection risks during FNAC by visualization of droplet production and deposition using a simulation model. METHODS: The simulation comprised a puncture needle, a device for holding the needle, and a fluid specimen containing fluorescent particles as a model. Simulating each step of FNAC (removal of the inner and outer cylinder and transferring the specimen onto a glass slide), the generation and deposition of droplets were visualized using a laser. RESULTS: After removal of the inner cylinder, an aerosol of droplets in the air surrounding the needle was observed. After removal of the outer cylinder, several large droplets precipitating onto the circumjacent surface were observed. From the beginning of transferring the specimen, a large amount of sizeable droplets first moving away and then precipitating was observed, followed by the production of a cluster of fine droplets drifting and spreading through the air. CONCLUSIONS: Here, the generation of droplets at each step of FNAC, precipitation of large droplets onto the circumjacent surface, and drifting and spreading through the air of fine droplets was visualized. These results emphasize the need for precautions to prevent the transmission of infectious agents during FNAC.

Self-learning followed by telepresence instruction of focused cardiac ultrasound with a handheld device for medical students: a preliminary study.

PURPOSE: This study aimed to assess the feasibility and efficiency of self-learning with or without self-training (subjects performed scans on themselves) and telepresence instruction in focused cardiac ultrasound (FOCUS) education for medical students. METHODS: This study included 24 medical students. The participants initially completed a written pre-test and were randomized into a video lecture (participants watched a video lecture) or self-training (participants watched a video lecture and self-performed FOCUS) group. After finishing self-learning, they completed a written post-test. Then they undertook a skill pre-test and a first perception survey. Telepresence instruction was then provided. Finally, they undertook a skill post-test and a second perception survey. RESULTS: The written post-test total scores were significantly higher than the pre-test total scores (P < 0.001). In the skill pre-test, the scores for the video lecture and self-training groups were not significantly different (P = 0.542). The skill post-test total scores were significantly higher than the skill pre-test total scores (P = 0.008). Forty-two percent of the video lecture group participants agreed that the video lecture was effective preparation for the skill pre-test, while all participants in the same group agreed that the combination of the video lecture and telepresence instruction was effective preparation for the skill post-test. CONCLUSION: This study demonstrated the feasibility and efficiency of self-learning followed by telepresence instruction on FOCUS for medical students.

In Vivo Temperature Rise Measurements of Rabbit Liver and Femur Bone Surface Exposed to an Acoustic Radiation Force Impulse.

Acoustic radiation force impulse (ARFI) imaging and shear wave elastography use a "push pulse." The push pulse, which is referenced as an ARFI in this study, has a longer duration than that of conventional diagnostic pulses (several microseconds). Therefore, there are concerns regarding thermal safety in vivo. However, few in vivo studies have been conducted using living animals. In this study, to suggest a concept for deciding an ARFI output and cooling time while considering thermal safety, the liver (with and without an ultrasound contrast agent) and femur bone surface of living rabbits were exposed to an ARFI, and the maximum temperature rise, temperature rise for 5-min duration, and cooling time were measured via a thermocouple. While testing within the regulation limits of diagnostic ultrasound outputs, a maximum temperature rise on the femur bone surface exceeded the allowable temperature rise (1.5°C) in the British Medical Ultrasound Society (BMUS) statement. However, using the linear relationships between the pulse intensity integral (PII) of a single pulse and the above three temperature parameters, PII may be determined so that the maximum temperature rise is within the allowable temperature rise in the BMUS statement. The cooling time can be estimated from the PII.

The Mechanisms Underlying Vertical Artifacts in Lung Ultrasound and Their Proper Utilization for the Evaluation of Cardiogenic Pulmonary Edema.

The recent advances in lung ultrasound for the diagnosis of cardiogenic pulmonary edema are outstanding; however, the mechanism of vertical artifacts known as B-lines used for the diagnosis has not yet been fully elucidated. The theory of "acoustic trap" is useful when considering the generation of vertical artifacts. Basic research in several studies supports the theory. Published studies with pilot experiments indicate that clarification of the relationship between the length and intensity of vertical artifacts and physical or acoustic composition of sources may be useful for differentiating cardiogenic pulmonary edema from lung diseases. There is no international consensus with regard to the optimal settings of ultrasound machines even though their contribution to the configuration of vertical artifacts is evident. In the clinical setting, the configuration is detrimentally affected by the use of spatial compound imaging, the placement of the focal point at a deep level, and the use of multiple focus. Simple educational materials using a glass microscope slide also show the non-negligible impact of the ultrasound machine settings on the morphology of vertical artifacts.

Ultrasonography in undergraduate medical education: a comprehensive review and the education program implemented at Jichi Medical University.

The concept of point-of-care ultrasound has been widely accepted owing to the development of portable ultrasound systems and growing body of evidence concerning its extensive utility. Thus, it is reasonable to suggest that training to use this modality be included in undergraduate medical education. Training in ultrasonography helps medical students learn basic subjects such as anatomy and physiology, improve their physical examination skills, and acquire diagnostic and procedural skills. Technological advances such as simulators, affordable handheld devices, and tele-ultrasound systems can facilitate undergraduate ultrasound education. Several reports have indicated that some medical schools have integrated ultrasound training into their undergraduate medical curricula. Jichi Medical University in Japan has been providing medical students with ultrasound education to fulfill part of its mission to provide medical care to rural areas. Vertical integration of ultrasound education into a curriculum seems reasonable to ensure skill retention and improvement. However, several issues have hampered the integration of ultrasound into medical education, including a lack of trained faculty, the need to recruit human models, requisition of ultrasound machines for training, and limited curricular space; proposed solutions include peer teaching, students as trained simulated patients, the development of more affordable handheld devices, and a flipped classroom approach with access to an e-learning platform, respectively. A curriculum should be developed through multidisciplinary and bottom-up student-initiated approaches. Formulating national and international consensuses concerning the milestones and curricula can promote the incorporation of ultrasound training into undergraduate medical education at the national level.

Evaluation of the Elasticity of the Pancreas Using Acoustic Radiation Force Impulse Elastography in Patients with Acute Pancreatitis: A Systematic Review and Meta-Analysis.

Acoustic radiation force impulse (ARFI) elastography has been used to diagnose acute pancreatitis (AP). The present study aimed to assess the effectiveness of ARFI elastography in the diagnosis of AP. Studies examining the efficacy of ARFI elastography in AP were selected by searching MEDLINE, EMBASE, CENTRAL, ICTRP, and ClinicalTrial.gov. until September 2021. Meta-analyses were performed using random effects models. The Grading of Recommendations, Assessment, Development, and Evaluation approach was used to assess the certainty of the evidence. Eight case-control studies (994 patients) were included in the meta-analysis. The ARFI-Virtual Touch Quantification value (or ARFI shear wave propagation velocity) of the AP patient group was 0.83 m/s higher (95% confidence interval [CI]: 0.36-1.3) than that in the control group (95% CI: 1.0-1.28). The sensitivity and specificity of ARFI elastography for diagnosing AP were 98.3% (95% CI: 92.6-96.6%) and 95.5% (95% CI: 87.5-98.5%), respectively. The results showed that physicians could use ARFI elastography to accurately diagnose patients with AP. Additional well-designed studies are necessary to validate the efficacy of ARFI elastography in patients with AP.

Simple Experimental Models for Elucidating the Mechanism Underlying Vertical Artifacts in Lung Ultrasound: Tools for Revisiting B-Lines.

Using simple experimental models, we evaluated the generation, configuration and echo intensity of vertical artifacts by varying the point or plane of contact and height of objects that correspond to sources of vertical artifacts in the subpleural space. We used an ultrasound gel spot to imitate the source and a block of bacon as a chest wall phantom. As the size of the point of contact between the gel spot on the polypropylene sheet and the phantom decreased by peeling the sheet, a vertical artifact measuring ≤1 cm was generated and/or extended deeper, finally reaching 10 cm in depth. Next, objects of different shapes made using gel balls were used to observe the generation of artifacts and measure and compare the echo intensity. For a given shape, the intensity was markedly higher in one model with the point of contact than in the other model with the plane of contact. With the same point or plane of contact, the echo intensity was higher in the taller model. The size of the point or plane of contact and height of the source were observed to be key factors in the generation, length and echo intensity of the artifacts.

Inhibitory effects of ultrasound irradiation on Staphylococcus epidermidis biofilm.

PURPOSE: We aimed to investigate whether low-intensity continuous and pulsed wave ultrasound (US) irradiation can inhibit the formation of Staphylococcus epidermidis biofilms, for potential application in the treatment of catheter-related bloodstream infections (CRBSI). METHODS: S. epidermidis biofilms that formed on the bottom surfaces of 6-well plates were irradiated on the bottom surface using the sound cell incubator system for different intervals of time. RESULTS: US irradiation with continuous waves for 24 h notably inhibited biofilm formation (p < 0.01), but the same US irradiation for 12 h had no remarkable effect. Further, double US irradiation with pulsed waves for 20 min inhibited biofilm formation by 33.6%, nearly two-fold more than single US irradiation, which reduced it by 17.9%. CONCLUSION: US irradiation of a lower intensity (ISATA = 6-29 mW/cm2) than used in a previous study and lower than recommended by the Food and Drug Administration shows potential for preventing CRBSI caused by bacterial biofilms.

Acoustic radiation force impulse under clinical conditions with single infusion of ultrasound contrast agent evoking arrhythmias in rabbit heart.

PURPOSE: We previously reported that acoustic radiation force impulse (ARFI) with concomitant administration of perfluorobutane as an ultrasound contrast agent (UCA)-induced arrhythmias at a mechanical index (MI) of 1.8 or 4.0 in a rabbit model. The present study identified the location of arrhythmias with a MI < 1.8 using a new system that can transmit ARFI with B-mode imaging. METHODS: Under general anesthesia, six male Japanese white rabbits were placed in a supine position. Using this system, we targeted ARFI to the exact site of the heart. ARFI exposure with MI 0.9-1.2 was performed to the right or left ventricle of the heart 2 min after UCA injection. RESULTS: ARFI with a MI lower than previously reported to rabbit heart evoked extrasystolic waves with single UCA infusion. Arrhythmias were not observed using ARFI without UCA. Extrasystolic waves were observed significantly more frequently in the right ventricle group than in the left ventricle group, with arrhythmias showing reversed shapes. No fatal arrhythmias were observed. CONCLUSION: ARFI applied to simulate clinical conditions in rabbit heart evoked extrasystolic waves with single UCA infusion. The right ventricle group was significantly more sensitive to ARFI exposure, resulting in arrhythmias, than the left ventricle group. The shapes of PVCs that occurred in the right ventricle group and the left ventricle group were reversed. Ultrasound practitioners who use ARFI should be aware of this adverse reaction, even if the MI is below the previously determined value of 1.9.

Pulmonary mycobacterium avium complex disease complicated by cancer: an 11-year survey at a single-center.

Objective: Pulmonary mycobacterium avium complex (MAC) disease is increasing significantly worldwide. Several studies have investigated the clinical features of pulmonary MAC disease in the setting of cancer. Here, we aimed to clarify the clinical characteristics of patients with cancer with recent onset of pulmonary MAC disease and the effect of cancer on the onset of this disease. Patients and Methods: Of the 323 consecutive Japanese patients newly diagnosed with pulmonary MAC disease at Jichi Medical University Hospital between and 2006-2017, we retrospectively reviewed 79 consecutive patients with cancer. Results: Seventeen patients had lung cancer (21.0%), while 62 had non-lung cancer. Of the 17 patients with lung cancer, 16 had adenocarcinoma of which 10 had stage I to III disease; 8 of the 10 patients had not received chemotherapy. Sixteen patients with lung cancer had a MAC infection in the ipsilateral lung. Notably, 9 of the 11 lung cancer patients who did not undergo surgery had a MAC infection in the affected lobe. Of the 39 patients with the most common types of non-lung cancer (14 had gastric cancer, 13 had colorectal cancer, and 12 had breast cancer), 22 had stage I to III disease, and 18 of these 22 had not received chemotherapy. Conclusion: Lung cancer may act as a local factor contributing to the onset of pulmonary MAC disease in the ipsilateral lung. However, the underlying mechanism by which a history of cancer might affect the onset of pulmonary MAC disease remains unclear. Further investigation into this mechanism is needed.