BACKGROUND: A correlation between acquired renal cysts in the dialysed kidney and renal cancer has long been debated, but no changes in the physical properties of kidneys at the microscopic level have been reported. The purpose of the present study was to classify the physical properties of the kidneys of patients undergoing haemodialysis at several stages of pathology by use of the scanning acoustic microscope. METHODS: Sixteen surgically excised kidneys of dialysis patients were investigated. Tissues were fixed in 10% formalin, frozen in acetone, and cut 10 microns thick on a cryostat. We used a scanning acoustic microscope operated in the frequency range of 100-200 MHz. Attenuation constant and sound speed were measured on a two-dimensional distribution. RESULTS: The attenuation constant for inflammatory granulation tissue was significantly higher than that for hyaline degeneration tissue (P < 0.001). Sound speed was high for granulation tissue, but tended to diminish gradually for hyaline degeneration. Sound speed increased again with progression to cystic degeneration (P < 0.001), but the attenuation constant remained low. When a cystic kidney contained a malignant lesion, the previously low attenuation constant rose at that site (P < 0.001), and the previously high sound speed was diminished (P < 0.001). CONCLUSION: Our data suggest that the physical properties of dialysed kidneys at different stages of pathology can be classified by their acoustic properties. Simultaneous evaluation of attenuation constant and sound speed is considered applicable to determining whether tissues contain malignant elements.

Background: Pulse diagnosis of the peripheral artery is an important technique in Traditional Chinese Medicine, where, in acupuncture therapy, the treatment is adjusted according to the observed changes of the pulse. We investigated the change of blood flow in the peripheral artery and the cardiac index during acupuncture treatment. Objectives: The aim of this study is to explore the effect of acupuncture on radial and brachial artery blood flow volume and the cardiac index in healthy subjects. Methods: Eighteen (18) healthy volunteers were enrolled. Acupuncture was performed bilaterally on LR-3 with manual rotation of the needles. The blood pressure and heart rate were measured at rest and 180 seconds after acupuncture. Radial and brachial artery blood flow volume was monitored continuously by an ultrasound with an echo-tracking system. Cardiac index was measured by impedance cardiography. The hemodynamic parameters were measured before, during, and 30, 60, 180 seconds after acupuncture. Results: The peripheral artery blood flow volume decreased significantly during acupuncture (radial; p < 0.01, brachial; p < 0.05) but increased at 180 seconds after acupuncture (radial; p < 0.05, brachial; p < 0.05) compared with before acupuncture. The cardiac index did not change significantly after acupuncture, but systemic vascular resistance index significantly decreased (p < 0.05). Conclusions: The present study showed that radial and brachial artery blood flow volume decreased immediately during acupuncture on LR-3 acupoint, but increased at 180 seconds after acupuncture. This reaction is attributed to the change in peripheral vascular resistance.

High-intensity focused ultrasound is a noninvasive treatment applied by externally irradiating ultrasound to the body to coagulate the target tissue thermally. Recently, it has been proposed as a noninvasive treatment for vascular occlusion to replace conventional invasive treatments. Cavitation bubbles generated by the focused ultrasound can accelerate the effect of thermal coagulation. However, the tissues surrounding the target may be damaged by cavitation bubbles generated outside the treatment area. Conventional methods based on Doppler analysis only in the time domain are not suitable for monitoring blood flow in the presence of cavitation. In this study, we proposed a novel filtering method based on the differences in spatiotemporal characteristics, to separate tissue, blood flow, and cavitation by employing singular value decomposition. Signals from cavitation and blood flow were extracted automatically using spatial and temporal covariance matrices.

To achieve fine visualization of the peripheral microvascular networks, we have developed a photoacoustic (PA) microscope equipped with a four-channel annular array transducer. The quality of PA images processed with delay-and-sum (DAS) method is degraded by off-axis signals. Thus, to achieve higher image quality for the PA microscope, this study evaluated the efficacy of the five coherence factor weighting methods: coherence factor, sign coherence factor, phase coherence factor, circular coherence factor, and vector coherence factor. Using PA signals acquired from a 100 μ m microtube and the skin microvessels, we generated PA images with DAS and one of the weighting methods, and quantitatively evaluated the image quality by calculating the sharpness, contrast ratio, and contrast-to-noise ratio. The results showed the phase coherence factor and the vector coherence factor methods were more effective to clearly visualize the microvascular structure, in terms of vessel sharpening and noise suppression performances, than the other methods.

We present a theoretical model of laser heating carbon nanotubes to determine the temperature profile during laser irradiation. Laser heating carbon nanotubes is an essential physics phenomenon in many aspects such as materials science, pharmacy, and medicine. In the present article, we explain the applications of carbon nanotubes for photoacoustic imaging contrast agents and photothermal therapy heating agents by evaluating the heat propagation in the carbon nanotube and its surrounding. Our model is constructed by applying the classical heat conduction equation. To simplify the problem, we assume the carbon nanotube is a solid cylinder with the length of the tube much larger than its diameter. The laser spot is also much larger than the dimension of carbon nanotubes. Consequently, we can neglect the length of tube dependence. Theoretically, we show that the temperature during laser heating is proportional to the diameter of carbon nanotube. Based on the solution of our model, we suggest using the larger diameter of carbon nanotubes to maximize the laser heating process. These results extend our understanding of the laser heating carbon nanotubes and provide the foundation for future technologically applying laser heating carbon nanotubes.

High-intensity focused ultrasound (HIFU) is a minimally invasive treatment modality to induce thermal coagulation. In clinical cases, noninvasive blood flow occlusion was successfully achieved by HIFU exposure. However, it is difficult to monitor the blood flow during HIFU exposure due to the interference of HIFU noise with RF echo signals. In this study, we proposed a novel filtering method for monitoring blood flow during HIFU exposure by combining an singular value decomposition (SVD) filter with the HIFU noise reduction method. The HIFU noise was reducted by subtracting the RF signals of passive imaging from the RF signals of active imaging while keeping the tissue and blood flow signals intact. After that, the blood flow signals were identified by employing the SVD filter, on the basis of the spatiotemporal characteristics and amplitudes of these signals. The results imply that the proposed filtering method is useful for monitoring of blood flow during HIFU exposure.