Tadashi Hachiga

Blood flow velocity imaging of malignant melanoma by micro multipoint laser Doppler velocimetry

We have developed a laser Doppler velocimeter to measure blood flow, the micromultipoint laser Doppler velocimeter (μ-MLDV). This equipment can measure absolute velocity and, based on this, can display the course of blood vessels. In this study, we attempted to perform blood flow velocity imaging of malignant melanoma transplanted to the mouse ear. We found that blood flow velocity of the formed blood vessels originating in the melanoma was much greater than that of the capillary vessels in normal skin. Furthermore, the form of the tumor was clearly visible from the blood flow velocity image. These experimental results suggest that μ-MLDV has potential as a diagnostic method for distinguishing benign nevi from malignant melanomas.

Measurement of blood flow velocity in a model of stenosis in vitro and in mesenteric vessels in vivo using non-invasive micro multipoint laser Doppler velocimetry

Our research goal is to carry out two-dimensional (2D) and three-dimensional (3D) measurements of the velocity distribution within a single vessel. We modified a non-invasive beam laser Doppler velocimeter using near-infrared light, and linearized the laser to carry out simultaneous multipoint measurements. We also scanned the measurement line in the direction of depth to allow 3D imaging of vascular blood flow in opaque areas in vivo. We used micro multipoint laser Doppler velocimetry (LDV) and a device with improved spatial resolution from 250 to 125 µm. We compared actual and calculated values using a rotating disk with an attached microwire. To demonstrate the effectiveness of the proposed system, blood flowing at a constant rate through a glass capillary and the velocity distribution of flow in the capillary were measured and mapped. The average flow velocity was calculated from the cross-sectional area and flow rate in the glass capillary, and we compared the calculated and measured values. To obtain an image of blood flow velocity in vivo, we measured both 2D and 3D flow velocity distributions in mouse mesenteric vessels.

In-vivo visualization of melanoma tumor microvessels and blood flow velocity changes accompanying tumor growth

We demonstrate that using micro multipoint laser Doppler velocimetry (μ-MLDV) for noninvasive in-vivo imaging of blood vessels is useful for diagnosing malignant melanomas by comparison with visual diagnosis by dermoscopy. The blood flow velocity in microvessels varied during growth of melanomas transplanted in mouse ears. Mouse ears were observed by μ-MLDV up to 16 days after transplantation. The blood flow velocity in the tumor increased with increasing time and reached maximum of 4.5 mm/s at 9 days, which is more than twice that prior to transplantation. After 12 days, when the lesion had grown to an area of 6.6 mm2, we observed the formation of new blood vessels in the tumor. Finally, when the lesion had an area of 18 mm2 after 16 days, the flow velocity in the tumor decreased to approximately 3.2 mm/s.

Pressure and Temperature Dependence of Dielectric Properties of Pb(Co1/2W1/2)O3

The pressure (0 to 5 kbar) and temperature (-150 to +60°C) dependence of dielectric properties (permittivity, dielectric loss tangent and phase transition temperatures) of ceramic Pb(Co1/2W1/2)O3 were measured, and the pressure-temperature phase diagram was obtained. The dielectric properties associated with the paraelectric-antiferroelectric phase transition was fairly explained in terms of a phenomenological theory.

Noninvasive In-vivo Measurements of Microvessels by Reflection-Type Micro Multipoint Laser Doppler Velocimeter

We have developed a micro multipoint laser Doppler velocimeter (µ-MLDV) that enables selective collection of Doppler interference photons. In previous report [H. Ishida et al.: Rev. Sci. Instrum. 82 (2011) 076104], developed the reflection-type µ-MLDV, and showed the results of demonstrations performed on transparent artificial flow channels. In this study, we attempted to perform in-vivo experiments using animals. It can measure absolute velocity and generate tomographs of blood vessels courses. The present system can perform noninvasive in-vivo measurements with a detection limit of about 0.5 mm/s and a spatial resolution in the x–y plane of 125 µm. It is thus able to image venulae. It was used to image venulae in a mouse ear and a subcutaneous blood vessel in a mouse abdomen at a depth of about 1.0 mm below the skin.

In vivo visualization method by absolute blood flow velocity based on speckle and fringe pattern using two-beam multipoint laser Doppler velocimetry

Two-beam multipoint laser Doppler velocimetry (two-beam MLDV) is a non-invasive imaging technique able to provide an image of two-dimensional blood flow and has potential for observing cancer as previously demonstrated in a mouse model. In two-beam MLDV, the blood flow velocity can be estimated from red blood cells passing through a fringe pattern generated in the skin. The fringe pattern is created at the intersection of two beams in conventional LDV and two-beam MLDV. Being able to choose the depth position is an advantage of two-beam MLDV, and the position of a blood vessel can be identified in a three-dimensional space using this technique. Initially, we observed the fringe pattern in the skin, and the undeveloped or developed speckle pattern generated in a deeper position of the skin. The validity of the absolute velocity value detected by two-beam MLDV was verified while changing the number of layers of skin around a transparent flow channel. The absolute velocity value independent of direction was ...

Note: Reflection-type micro multipoint laser Doppler velocimeter for measuring velocity distributions in blood vessels

We have developed a laser Doppler velocimeter (LDV) for measuring velocity distributions in blood vessels. We converted a transmission-based LDV into a reflection-based LDV to make it suitable for clinical applications. The velocity distribution image of a serpentine flow channel obtained could be qualitatively explained by the numerical results. Finally, we evaluated the system by using it to measure injection of blood into a glass tube by a syringe pump. The results obtained demonstrate that erythrocytes can be used as seeding particles for the reflection-type micro multipoint LDV. The results obtained are useful as basic data for clinical applications.

Multi-channel laser Doppler velocimetry using a two-dimensional optical fiber array for obtaining instantaneous velocity distribution characteristics

A laser Doppler velocimeter (LDV) has been developed that is capable of performing two-dimensional (2D) cross-sectional measurements. It employs two horizontal laser light sheets that intersect at an angle of 13.3°. Since the intersection region is thin, it can be used to approximately determine the 2D flow field. An 8 × 8 array of optical fibers is used to simultaneously measure Doppler frequencies at 64 points. Experiments were conducted to assess the performance of the LDV, and it was found to be capable of obtaining spatial and temporal velocity information at multiple points in a flow field. The technique is fast, noninvasive, and accurate over long sampling periods. Furthermore, its applicability to an actual flow field was confirmed by measuring the temporal velocity distribution of a pulsatile flow in a rectangular flow channel with an obstruction. The proposed device is thus a useful, compact optical instrument for conducting simultaneous 2D cross-sectional multipoint measurements.

Observation of tumor microvessels that are controlled by blood flow in breast cancer

We attempted to perform non-invasive breast cancer imaging using a reflection-type multipoint laser Doppler velocimeter to monitor blood flow. On day six, after transplantation of cancer cells into mouse breast, we found that blood flow velocity in a blood vessel that extended into the tumor was increased compared to that in normal skin. The effect of carcinogenesis on blood flow over such a short period was shown using blood flow velocity imaging. Although such imaging has not yet been adapted for use in humans, this study is an important step in reaching the ultimate goal, which is early detection of breast cancer.

Low-Resistivity Bi2Sr2CaCu2O8+δ/Au Contacts for Fabrication of Stacked Intrinsic Josephson Junctions

We investigated the specific contact resistivity (ρc) of a Bi2Sr2CaCu2O8+δ (Bi-2212)/Au interface for the fabrication of high-quality intrinsic Josephson junctions (IJJs). The Bi-2212 single crystal was grown using a self-flux method. The Au film was deposited on the freshly cleaved crystal surface by RF magnetron sputtering using different vacuum chambers with different background pressures (PBP= 6.7×10-3, 8.0×10-4, and 1.1×10-4 Pa). For PBP= 6.7×10-3 Pa, the substrate temperature (Ts) dependence of the ρc was studied. The measurement of ρc was carried out at room temperature. ρc decreased with an increase in Ts, and reached 2×10-3 Ω cm2 at Ts =150 °C. This result may explain the Au particle diffusion in the Bi-2212 crystal induced by self-heating during deposition. We also measured the PBP dependence of ρc. ρc decreased with a decrease in PBP, and reached 8×10-5 Ω cm2 for PBP=1.1×10-4 Pa. We suggest that the adsorption of residual moisture on the cleaved Bi-2212 surface is the dominant cause of the degradation of ρc. In our research, 8×10-5 Ω cm2 was the minimum value. Finally, we fabricated a stacked Bi-2212 Josephson junction (Bi-2212 stack) using a self-planarizing process. The ρc of these stacks was 8×10-5 Ω cm2 in the temperature range from 4.2 to 77 K. This value was smaller than the target value, i.e., ρc=1×10-3 Ω cm2.