| (1)Research background | |
| [The cause of one's death] | |
| About 60 percent of the Japanese have passed away with the neoplasm (cancer) which are the three major lifestyle-related illnesses, the cardiac disease (cardiopathy), and the brain blood vessel disease (apoplexy). (Refer to figure)Among these, the main causes of a cardiac disease and a brain blood vessel disease are arteriosclerosis. Although arteriosclerosis advances with aging, the advance degree is influenced by the custom and home environment of everyday life, and social environment. Therefore, the time whose symptoms arteriosclerosis,illness from which arteriosclerosis happens owing to,shows changes with people. It is very important that inspect the advance degree of arteriosclerosis at an early stage, and it is in charge of prevention and medical treatment. Although it changes in the diagnostic method of arteriosclerosis with blood vessels to diagnose, there are various methods, such as diagnosis by blood vessel photography, X ray CT inspection, an ultrasonic dislocation method, and the ultrasonic Doppler method. There is a diagnostic method of WI measurement which diagnoses the advance degree of arteriosclerosis by computing the index which shows the contraction power of the heart which measures the blood pressure and the blood flow velocity of carotid artery using ultrasonic diagnosis equipment, and is called Wave Intensity (WI) by one in it. We are doing research and development in the new measurement robot system which supports the solution and WI measurement of a problem in the present WI measurement paying attention to this diagnostic method. |
 2007, Ministry of Health, Labor and Welfare |
| [Wave Intensity] | |
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Wave Intensity is the index which Paker and Jones proposed as an index with which the influence the advance wave which goes to erasion from the heart, the blood pressure of the artery which is a synthetic waveform by the reflective wave which goes to the heart from erasion, and whose waveform of a flow velocity are which distinguishes a superior mosquito. Although WI which came to be called such from it being the same unit as the intensity of a sound wave attracted attention only from the physical meaning ,superiority or inferiority of the influence of an advance wave and a reflective wave, which the mark of the positive/negative has It becomes clear that the size of WI has an important physiological meaning by research of Professor Sugawara of the Himeji Dokkyo University, and it attracts attention as a new indicator of blood-flow dynamics. WI is calculated by the product of blood pressure P and the time differentiation value of a flow velocity U. |
 
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The feature of WI is very sharp to state change of a circulatory organ system. This feature is the factor which attracts attention as a new indicator of blood-flow dynamics. It is used as a means to know the contraction power of the heart especially now. The advance degree of arteriosclerosis affects the size of Compression Wave (W1) of the left figure, and Expansion Wave (W2). W1 and W2 which the size of W1 decreases and the size of W2 increases are expressed like the following formula as arteriosclerosis advances and a blood vessel becomes hard. |
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Here, the grade of the hardness of a blood vessel is expressed with the constant to which rho is called blood density and beta is called stiffness parameter. Arteriosclerosis is inspected by computing the value of beta from the value of W1 and W2 which were obtained by measurement. |
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| [The problem of WI measurement] | |
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Until now, the method to support the supersonic wave probe by the hand or by the adjustment catch has been adopted as methods of measuring WI. The advantage when supporting it by the hand is that alignment is easy. But, Maintaining it at the same position is difficult and the load of the doctor is large. On the other hand, the position-keeping load is small when the adjustment catch is used. But, because of hard fine adjustment and low user-friendliness, realignment requires time and patient's fatigue is increased. The purpose of this study is to reduce the measurement time and the doctor's and the patient's fatigue by development of a robot system. |
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| (2)Hardware | |
| [Configuration of robot system] | |
 Robot system is configured with a probe supporting device, a controller and a ultrasonic diagnostic system. |
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| [Probe supporting device] | |
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Approximate adjustment (One-touch switching of fixation and release，Passive) ・Positioning arm ・Probe fixing ball joint Fine adjustment (Controller operation，Active) ・Probe manipulator |
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[Probe holding manipulator] The probe holding manipulator has 6-DOF, parallel link mechanism. A different point is to divide into the link part and the actuator part though the structure of the link part looks like the Stewart platform type. It is becoming by composing like this it is possible to thin as for the link. As a result, it is in came to being able to take a movable range widely because it becomes difficult to interfere with the link mutually. The size is 100[mm] in diameter and 340~400[mm] in length, and weight is approximately 2.0[kg]. We applied the genetic algorithm for optimization of link position. |
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[Link part] The link part is composed of total 6-DOF, and linear actuator (1-DOF), and 2 universal joint (2-DOFx2), and bearing (1-DOF). The thickness of the link is 3[mm], and a movable corner of universal collaboration is 45 [deg]. |
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[Actuator part] The actuator part is composed of the DC motor and the ball screw. |
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[Positioning arm] The positioning arm is passive and it has 6-DOF. It is possible to fix with the permanent magnet brake in each joint.The positioning arm equips a mechanical gravity canceller configured with a consant force spring. Since the passive mechanism is released when a foot switch is pressed, the risk of forgettig to turn off the switch is low. Furthermore because the permanent magnet brakes are used, it is fixed without electric power. Therefore the risk that the arm is not fixed is low when an accident like power failure. Additionaly, the fixing force of the arm is not strong so that a patient or a doctor can quickly change the arm's configuration when a patient or a doctor feels danger. In this way, the arm assure the safety of the doctor and the patient. |
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The mechanical gravity canceller is composed of constant force spring attached to slide guide so that moment arm of both side can ballance. Furthermore, slide guide has a adjustable small angle in order to cancel non-linearity of constant force spring output. The mechanism achieved almost complete gravity cancellation. |
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[Probe fixing ball joint] A permanent magnet is used for fixation. And, an electromagnet is used for release. |
| [Probe controller] | |
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Laser mouse sensor, acceleration sensor, gyro sensor and photo-reflector is used for probe controller. X and Y-axis is detected with Laser mouse sensor. Yaw-axis is detected with two laser mouse sensors combination. Roll and pitch-axis is detected with accelaration sensor and gyro sensor. Z-axis is detected with photo-reflector. Controller is divided into grip part and ground part so that laser mouse sensor should not leave from ground while inputting angle. |
| (3)Clinical tests | |
| WI measurement test has been done by doctor and ultrasound diagnosis technician. The first figure shows the time spent by three ways of measurement (traditional manual fixing, using adjustment catch and robot system). The robot system results shorter measurement time. We expanded the movable range of the manipulator in 2008 and evaluated the usability of manipulator. The second figure shows the frequency which expanded rage has been used during position fixing by the robot system. It is presented that expanded movalbe range has been used at frequency of over 60%. The doctor evaluated the robot system intuitive and easy to operate. | |
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| (4)Link | |
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SolidWorks Japan K.K. |
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