Purpose: Though improvement in the efficiency of ultrasound treatment is expected in combination with microbubbles, because microbubbles disperse in the bloodstream, we have attempted to actively control microbubbles in blood flow by means of acoustic radiation force in order to increase the local concentration of the microbubbles. Bubble liposomes (BLs), which have a high potential to contain various kinds of drugs, are ready for in vivo applications, and investigation of the possibility of active control is needed. However, the controllability of microbubbles in blood flow has not been confirmed. Because the average diameter of BLs is 0.5 μm, their concentration cannot be measured with conventional optical observation. Subjects and Methods: Therefore, we established a method for identifying the concentration of BLs from the brightness variations in ultrasound images (echograms) with two kinds of suspension, i.e., normal saline and porcine blood. First, we derived an acceptable mechanical index at which the effect of BL destruction can be ignored when measuring the concentration. We then examined the active path selection of BLs using a Y-form bifurcation of artificial blood vessels with focused ultrasound with a central frequency of 5 MHz and a maximum sound pressure of 300 kPa-pp, in a flow velocity of 30 mm/s. Results and Discussion: The experiments confirmed less destruction of BLs with the medium of porcine blood as compared with normal saline. Furthermore, higher induction performance was confirmed when the focal point of ultrasound emission was several mm away from the bifurcation point versus the focal point corresponding to the bifurcation point. Conclusion: From these results there is a possibility to enhance the controllability of in vivo BLs.

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Purpose: Subtle myocardial deformations such as early systolic lengthening (ESL) and post-systolic shortening (PSS) seem to be useful for detecting myocardial ischemia by 2-dimensional (2D) speckle tracking echocardiography. However, it is still unclear whether the same holds true for the 3-dimensional (3D) method. We therefore evaluated the accuracy of 2D and 3D speckle tracking echocardiography for the diagnosis of myocardial ischemia using an experimental model. Subjects and Methods: In 20 open-chest dogs, 2D or 3D echocardiographic images were acquired before flow reduction of the left circumflex artery, during 20-40% of flow reduction (stenosis 1) and 40-60% of flow reduction (stenosis 2). Peak systolic strain, early systolic lengthening, and post-systolic shortening were analyzed in the ischemic region, and the area under the curve (AUC) of the receiver operating characteristic curve for diagnosing each stenosis was calculated. Results: With the 2D method, the AUC of all parameters was significantly larger than the line of no information (AUC=0.5) in the case of stenosis 2; however, only the AUC of PSS was significant in the case of stenosis 1 (AUC: peak systolic strain=0.70, ESL=0.72, PSS=0.87). With the 3D method, the AUC of all parameters tended to be smaller than that yielded by the 2D method. Neither ESL nor PSS was significant in the case of stenosis 1 (AUC: peak systolic strain=0.64, ESL=0.51, PSS=0.61). Conclusion: 2D speckle tracking echocardiography provided better diagnostic accuracy for detecting myocardial ischemia than the 3D method. The assessment of PSS was superior to that of peak systolic strain with the 2D method but not with the 3D method.

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Purpose: To elucidate the mechanism behind the so-called “bamboo blind” sign frequently observed on B-mode images as multiple low-echoic lines in nonalcoholic steatohepatitis and highly fatty liver cases. Subjects and Methods: Six types of acoustic shadowing artifacts that might be the cause of the bamboo blind sign were defined. B-mode images were acquired for 21 fatty liver cases (inc. 9 highly fatty liver cases). The cases were then pathologically diagnosed. A phantom experiment was also performed to investigate whether the refraction occurs due to the gap of sound velocity between two different media. Results and Discussion: The mechanism of the bamboo blind sign corresponded well to the acoustic shadowing from small vessels in the liver. The phantom experiment validated the same phenomenon at a larger gap in sound velocity, which can be regarded as the same level as that in highly fatty liver cases. Conclusion: The refraction between blood vessels and highly fatty liver parenchyma with decreased sound velocity is the dominant reason for the bamboo blind sign.

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Purpose: Achilles tendonitis and plantar fasciitis are features of spondyloarthritis (SpA) that are used to evaluate the activity of SpA. There were few reports about the association between osteophytes at the entheses and the thickness of entheseal insertions. We aimed to clarify the association between osteophytes at the enthesis of calcaneus and the thickness of Achilles and plantar entheseal insertions. Subjects and Methods: We screened for SpA in 165 patients between June 2014 and November 2015. We excluded the patients who were diagnosed with SpA, rheumatoid arthritis, and other collagen diseases, and who had heel pain. Ninety-one feet were included. We evaluated osteophytes at the enthesis of calcaneus (lateral image) and the thickness of Achilles and plantar entheseal insertions by ultrasound examination. Results and Discussion: In the case of Achilles entheseal insertions, the thickness of positive osteophytes at the enthesis was thicker than that of non-osteophytes at the enthesis (4.45±0.78 and 3.96±0.65, p⟨0.01). In the case of plantar entheseal insertions, there was no association between the thickness and osteophytes at the enthesis (2.85±0.48 and 2.77±0.64, p=0.52). Osteophytes at the enthesis of the Achilles tendon develop within the insertions, but osteophytes at the enthesis of the plantar fascia do not develop within the plantar fascia. This difference may reflect the mechanism of the osteophyte during enthesis formation. Conclusion: Osteophytes at the enthesis may cause thicker Achilles entheseal insertions. Therefore, we should carefully interpret the thickness of calcaneus insertions in cases with an osteophyte at the enthesis.

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