JP2010269060A - Array type ultrasonic pulse wave measuring sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an array type ultrasonic pulse wave measuring sheet, as a flexible ultrasonic sheet, which can be easily installed on the body surface, and which can be easily used without requiring probe positioning by a specialist by arranging a number of elements in an array shape. <P>SOLUTION: As the flexible ultrasonic sheet as an array of ultrasonic elements is applied to the wrist close to the radial artery, signals of the ultrasonic elements correctly applied to the radial artery need only be read, thus eliminating need of fine positioning. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to hemodynamic evaluation and blood vessel hardness measurement.

  There are several examples in which micro ultrasonic transducers are arranged in an array, and there are several configurations and processing methods, but all are probe shapes, not flexible and thin sheet shapes that can be attached to the body surface.

Surface Micromachined Capacitive Ultrasonic Transducers I. Ladabaum, J. Xuecheng, HT Soh, A. Atalar, BT Khuri-Yakub IEEE Trans on Ultrasonics, Ferroelectrics, and Frequency Control, Vol. 45, No. 3 (1998), pp. 678- 690 Flexible Transducer Arrays with Through-wafer Electrical Interconnects Based on Trench Refilling with PDMS X. Zhuang, D.-S. Lin, O. Oralkan, and BT Khuri-Yakub Technical Digest of the 20th IEEE International Conference on Micro Electro Mechanical Systems (MEMS 2007 ), Kobe (2007, Jan.), pp. 73-76

  Provided are new measuring means such as ultrasonic inspection that can be easily used by the user, and monitoring with time by ultrasonic waves by attaching to the body surface.

  A flexible ultrasonic sheet that can be easily mounted on the body surface, and an array of many elements makes it easy for the user without the need for probe alignment by specialists, such as clinicians and clinical engineers. Can be used. As one of the specific purposes, it aims at a health care device that detects and monitors hemodynamics by attaching it to the skin on the radial artery of the wrist.

  Conventional ultrasonic inspection requires expert probe alignment, but by using a flexible array shape, the user can use it by himself / herself, which can be useful for health management and the like. Batch production is possible by using MEMS technology.

Image of array type ultrasonic pulse wave measurement sheet Examination of measurement target Device structure diagram Image of array type ultrasonic pulse wave measurement sheet Removing the board wiring PCB wiring plan Ultrasonic device fabrication process flow Wiring board manufacturing process flow Backing material production process flow Fabrication of ultrasonic element Fabrication of ultrasonic element Fabrication of electrode wiring pattern Backing material formation Apply backing material to adhesive sheet Evaluation with a single element Wiring removal Evaluation method No reflection from object Reflection from the object Move closer to the object Conversion of time change into distance

  Arteriosclerosis, a condition in which the arterial layer becomes thicker or stiffer and loses its elasticity and flexibility, is a major cause of diseases such as heart disease and cerebrovascular disorder. Early detection of arteriosclerosis is important for treatment.

  When the blood is pushed out of the heart, the waveform of the pressure in the blood vessel is called a pulse wave. By measuring this pulse wave, the vasomotor response can be examined, and the state of the blood vessel can be examined. Has been. In the field of integrated medicine represented by Kampo and Acupuncture, there is a technique called pulse diagnosis that simultaneously measures the pulse wave of the rib arteries (the artery running on the thumb side of the wrist) at three locations. Useful for understanding disease.

  Pulse waves have been measured with ultrasonic probes, but specialized in positioning the probe to the rib artery (the artery that runs on the thumb side of the wrist), the brachial artery, etc. The skills of a home, such as a clinician or clinical engineer, are required. In addition, since the slight displacement between the probe and the measurement object affects the measurement result, it is necessary to fix the probe on the wrist. However, it is difficult to stably fix the wrist for several minutes or more, and it is practically difficult to move the probe following the wrist. In addition, examples of arteries that are relatively close to the body surface that can be ultrasonically measured include the carotid artery, the superficial temporal artery of the head, and the artery near the foot surface.

  Therefore, by creating a flexible and wearable sheet-shaped measuring device with a plurality of ultrasonic elements mounted in an array, there is no need for the probe to be positioned by an expert, making it easy to measure pulse waves and blood vessels at home. Hardness evaluation, exercise monitoring, etc. are possible (see Fig. 1). Multi-point simultaneous measurement is also possible.

  Ultrasonic elements are mounted in a one-dimensional or two-dimensional array on a sheet that can be attached to the skin (ribs) on the artery located near the body surface, and a flexible sheet is mounted with the ultrasonic elements in an array. Since only the signal of the ultrasonic element correctly applied to the radial artery (the element in the red frame in FIG. 1) need only be read by being attached to the nearby wrist, fine alignment is not required. In addition, since the ultrasonic elements are mounted on the sheet in a one-dimensional or two-dimensional array, precise alignment with the measurement object is unnecessary.

  A flexible and wearable sheet can be monitored during exercise. A flexible, thin and lightweight sheet that moves following the object to be measured and reduces displacement.

  Measurement items include “diameter change” of radial artery, blood flow velocity using Doppler effect, and evaluation of blood vessel hardness by elastic measurement. Simple imaging is possible by reducing the element size and increasing the number. Become. When looking at the displacement of the blood vessel wall, it is impossible to measure the displacement of only the blood vessel wall when both the blood vessel wall and the element are displaced. Even when displaced, the change in the diameter of the blood vessel wall can be measured (see FIG. 2).

  Piezoelectric single crystal PMN-PT is used for the ultrasonic element (ultrasonic transducer), Au / Cr is used for the electrode, and polyimide film is used for the flexible substrate. A backing material is attached to suppress the vibration on the upper electrode side and to efficiently propagate the ultrasonic wave into the body (see FIG. 3).

  Note that the ultrasonic transducer does not necessarily need to be a piezoelectric single crystal, and may be piezoelectric ceramics such as PZT or CMUTs (Capacitive Micromachined Ultrasonic Transducers) manufactured by MEMS technology (Non-Patent Documents 1 and 2). PZT can be a bulk material, a film formed by sputtering, or a sheet obtained by thinning and sintering a slurry of slurry. Both can be made into a two-dimensional array type sheet by microfabrication technology such as MEMS. What will be described later is one of the embodiments. The flexible substrate is not necessarily made of polyimide, and may be another flexible material or a structure in which the hard and unbent arrays are connected by a soft material or a bending structure.

  Considering the movement of the wrist, it is necessary to be flexible mainly in the long axis direction, so it is desirable to extend the electrode wiring in the short axis direction (see FIG. 4).

The specifications are as follows.
-Number of elements: 30 (10 horizontal x 1 row x 3)
・ Element size: 500μm × 500μm
-Flexible board size: 20mm x 20mm
・ Wiring: Thin coaxial cable

  FIG. 7 shows a process flow for manufacturing the ultrasonic element. A film of Au / Cr is formed on the entire surface of the piezoelectric material PMN-PT (thickness 0.3 mm) by sputtering (about 600 nm), and a notch for separating the upper and lower electrodes (several μm) by a dicer and a notch for element isolation (Approx. 100 μm). The processed PMN-PT is bonded to a flexible board with Au / Cr wiring pattern (Au / Au bonding). A backing material is pasted with an adhesive sheet, and each element is separated by a dicer. A coaxial cable is attached with a conductive adhesive, and polarization is performed (see FIGS. 5 and 6).

  Next, FIG. 8 shows a process flow for manufacturing a wiring board. Au / Cr is deposited on a polyimide film (50 μm) by sputtering (about 700 nm), and a positive resist is applied by spin coating. The resist is patterned by photolithography using a mask on which a wiring board pattern is drawn. Unnecessary Au / Cr is etched using the resist remaining in the wiring pattern as a mask. The resist is removed with acetone to obtain an Au / Cr wiring pattern. PMN-PT processed on this wiring board film is bonded by Au / Au bonding.

  A process flow for producing the backing material is shown in FIG. Backing material mixed with epoxy and tungsten at 58:42 is buried in the frame of the glass plate. A Teflon (registered trademark) film is used for the base so that the backing material can be easily peeled off after curing. After curing at 80 ° C / 3h, remove the backing material from the Teflon (registered trademark) film and apply it to one side of the double-sided PSA sheet (10μm). Cut out to the size of the ultrasonic element to be attached by a dicer, and attach it to the ultrasonic element. Each element is separated by a dicer.

  In order to fabricate 10 ultrasonic elements in one horizontal row in an array at a time, PMN-PT (thickness 0.3 mm) is cut into 0.5 mm x 10 mm size, and Au / Cr is sputtered on the entire surface while rotating. The upper and lower electrodes were separated by making a 25 μm wide cut (see FIG. 10).

  In order not to cut the substrate when the element is separated, a cut having a width of 100 μm and a depth of 100 μm is made on the lower electrode side of the PMN-PT (see FIG. 11).

  An electrode wiring pattern of Au / Cr was prepared on a polyimide film (see FIG. 12). A glass plate frame made on a Teflon (registered trademark) film is filled with a mixture of epoxy and tungsten (5.84 g: 4.16 g), filled in to a uniform thickness, cured at 80 ° C / 3h, and approximately 300μm thick The backing material was formed (see FIG. 13).

  The backing material was taken out from the glass frame on the Teflon (registered trademark) film, pasted on one side of a double-sided adhesive sheet (10 μm), cut out together with the adhesive sheet to a size of 0.5 mm x 10 mm, and pasted on PMN-PT (see Fig. 14) .

Evaluation with a single element was performed (shown in FIG. 15. A single element (0.5 mm × 0.5 mm) was cut out and bonded with a wiring board film by Au / Au bonding using a flip chip bonder.
-Joining conditions: Temperature: 350 ° C / 60min, load: 1 N, pressure: 4 MPa

  As shown in FIG. 16, a coaxial cable (φ300 μm) was attached with a conductive adhesive, and polarization (450 V / 30 min) was performed.

Evaluation method (see Fig. 17)
-Cover with ultrasonic gel with the upper electrode side facing down and the lower electrode side (substrate film side) facing up-Place a sponge as a backing material to absorb reflection on the upper electrode side-Object (use a metal ruler ) On the substrate film, change the distance to the element, observe the change in waveform at that time with a digital oscilloscope, convert the change in reflection time from the object into distance

  Since the backing material is not attached to the element this time, we decided to use a sponge as the backing material to suppress the reflection of ultrasonic waves on the upper electrode side. A metal ruler was used for the object to obtain a large reflection (see FIGS. 18 to 20).

  When the object is brought closer, the time (horizontal axis) when the reflected wave returns changes. The change in distance from the object can be obtained from the change in time and the speed of sound (1.5 × 103 m / s).

  In the measurement by the impedance analyzer, the resonance frequency of this single element was 1.35 MHz (see FIG. 21).

  In the actual specification, it is necessary to measure the vascular system by disassembling a plurality of reflection sound sources distributed at different depths, so it is necessary to improve the distance resolution by using a single pulse and increasing the frequency.

Claims (4)

  An array type ultrasonic pulse wave measurement sheet, wherein ultrasonic elements are mounted in a one-dimensional or two-dimensional array on a sheet that can be attached to the skin on an artery located near the body surface.   2. The array-type ultrasonic pulse wave measurement sheet according to claim 1, wherein the ultrasonic elements are mounted on the sheet in a one-dimensional or two-dimensional array so that precise alignment with a measurement object is unnecessary.   3. The array-type ultrasonic pulse wave measurement sheet according to claim 1, wherein the sheet is flexible, thin and lightweight, and moves in accordance with a measurement target to reduce positional deviation.   4. The array type ultrasonic pulse wave measurement sheet according to claim 1, wherein the measurement item is a change in radial artery diameter, blood flow velocity, blood vessel elasticity, or blood vessel image.