Patent Application
20100292566
The present invention relates to a load detection device and a load detection method, and particularly to a load detection device and a load detection method for detecting load applied to a tip end of a linear body having flexibility in inserting the linear body in a hollow tube inserted in a bending vessel.
A catheter has conventionally been put into practical use as a linear medical appliance to be inserted in a vessel in a body such as a blood vessel, a ureter, a bronchus, an alimentary canal, or a lymph vessel. Among treatment methods using a catheter, for example, a method of preventing rupture of a cerebral aneurysm by guiding a tip end of a catheter representing a hollow tube to a mouth of the cerebral aneurysm through a blood vessel from outside a body, thereafter inserting an embolization coil and a delivery wire representing linear bodies having flexibility in the catheter, and filling the cerebral aneurysm with the embolization coil is available. If excessive load is applied to the cerebral aneurysm by the embolization coil and the delivery wire, however, the cerebral aneurysm may be damaged.
In addition, a method of providing a pressure sensor at a tip end of a catheter is available as a method of detecting load at the tip end of the catheter (see, for example, Japanese Patent Laying-Open No. 10-263089 (Patent Document 1)).
It is extremely difficult, however, to provide a pressure sensor at the tip end of a thin embolization coil and to insert in the embolization coil a signal line for extracting a signal from the pressure sensor to the outside.
Therefore, a primary object of the present invention is to provide a load detection device and a load detection method capable of readily detecting load applied to a tip end of a thin linear body.
A load detection device according to the present invention is a load detection device for detecting load applied to a tip end of a linear body having flexibility when the linear body is inserted in a hollow tube inserted in a bending vessel, and the load detection device includes first detection means for detecting a degree of bending of the vessel, the hollow tube or the linear body, second detection means for detecting load in insertion of the linear body in an inlet of the hollow tube, and calculation means for finding load applied to the tip end of the linear body based on a result of detection by the first and second detection means.
Preferably, the first detection means detects the degree of bending of the vessel, the hollow tube or the linear body based on an image of the vessel, the hollow tube or the linear body.
In addition, preferably, the calculation means finds the load applied to the tip end of the linear body further based on a coefficient of friction between the linear body and the hollow tube.
In addition, preferably, the calculation means corrects the coefficient of friction based on variation in flexural rigidity depending on a position in the linear body when the flexural rigidity of the linear body varies depending on the position in the linear body.
In addition, preferably, the coefficient of friction is measured in advance.
In addition, preferably, the vessel is a blood vessel, the hollow tube is a catheter, and the linear body is a treatment wire to be inserted in the catheter.
In addition, preferably, the treatment wire includes a delivery wire and an embolization coil provided at a tip end portion of the delivery wire, for filling a cerebral aneurysm.
In addition, preferably, the first detection means detects a degree of bending of the treatment wire when a tip end of the embolization coil enters the cerebral aneurysm, and the calculation means finds load applied to the cerebral aneurysm by the embolization coil.
In addition, preferably, the first detection means detects a degree of bending of the blood vessel based on a three-dimensional image of the blood vessel.
In addition, preferably, the first detection means detects a degree of bending of the treatment wire based on a two-dimensional image of the treatment wire taken by using X-rays during a surgical operation and a three-dimensional image of the blood vessel taken in advance, as superimposed on each other.
In addition, preferably, the load detection device includes drive means for inserting the linear body in the inlet of the hollow tube, and the second detection means detects the load in insertion of the linear body based on drive force of the drive means.
In addition, preferably, the load detection device includes a drive roller for inserting the linear body in the inlet of the hollow tube, a pressing roller rotatably supported and pressed by the drive roller with the linear body being interposed, and a motor for rotatably driving the drive roller, and the second detection means detects strain of a rotation shaft of the motor and detects the load in insertion of the linear body based on a result of that detection.
In addition, preferably, the second detection means includes a main body portion having a through hole through which the linear body passes and an internal space provided at an intermediate point of the through hole and formed such that the linear body can curve in a prescribed direction when compressive force is applied to the linear body, and a curve sensor for detecting a degree of curve of the linear body in the internal space, and detects the load in insertion of the linear body based on the degree of curve detected by the curve sensor.
In addition, preferably, the second detection means includes a main body portion having a through hole through which the linear body passes and formed in a bent manner such that the linear body applies a pressure in a prescribed direction when compressive force is applied to the linear body, and a pressure sensor provided at an intermediate point of the through hole, for detecting a pressure applied by the linear body in the prescribed direction, and detects the load in insertion of the linear body based on a result of detection by the pressure sensor.
In addition, preferably, the load detection device further includes display means for visually displaying at least one load of the load in insertion of the linear body detected by the second detection means and the load applied to the tip end of the linear body found by the calculation means.
In addition, preferably, the load detection device further includes sound generation means for generating sound indicating at least one load of the load in insertion of the linear body detected by the second detection means and the load applied to the tip end of the linear body found by the calculation means.
In addition, preferably, the load detection device further includes recording means for recording in a video image recording medium together with an fluoroscopic image of a tip end portion of the linear body, at least one load of the load in insertion of the linear body detected by the second detection means and the load applied to the tip end of the linear body found by the calculation means.
In addition, preferably, the load detection device is incorporated in a medical training apparatus.
In addition, a load detection method according to the present invention is a load detection device for detecting load applied to a tip end of a linear body having flexibility when the linear body is inserted in a hollow tube inserted in a bending vessel, and a degree of bending of the vessel, the hollow tube or the linear body and load in insertion of the linear body in an inlet of the hollow tube are detected, and load applied to the tip end of the linear body is found based on a result of that detection.
According to the load detection device and the load detection method of the present invention, a degree of bending of a vessel, a hollow tube or a linear body and load in insertion of the linear body in an inlet of the hollow tube are detected, and load applied to the tip end of the linear body is found based on a result of that detection. Therefore, even when the linear body is thin, load applied to the tip end of the linear body can readily be detected.
1 hollow tube; 2 linear body; 3 catheter; 4 embolization coil; 5 delivery wire; 6 cerebral artery; 7 cerebral aneurysm; 8 Y-connector; 10 X-ray equipment; 1 image synthesis device; 12 degree-of-bending detection device; 13, 56 insertion load detection device; 14 storage device; 15 arithmetic processing unit; 16 display device; 20 aorta; 21 carotid artery; 22 vertebral artery; 23 blood vessel; 24 fluoroscopic two-dimensional image; 25 three-dimensional blood vessel image; 26 path; 27 three-dimensional image; 30 pressing roller; 31 drive roller; 32 motor; 33 torque control circuit; 34 torque sensor; 40, 50 main body portion; 41, 51 through hole; 42, 52 input and output port; 43 restraint portion; 44 space; 45 line sensor; 46 light source device; 47 storage portion; 48 signal generation portion; 53 elastic member; 54 strain sensor; 55 human body; 57, 64 cable; 58 operation device; 59 display; 60 speaker; 61 switch; 62 simulator; and 63 monitor.
Specifically, as shown in
−Ff=Fo·cos α−Fi·cos α (1)
Fh=Fo·sin α+Fi·sin α (2)
Here, denoting a coefficient of friction as μ, Ff=μ·Fh. In addition, as angle α corresponds to Δθ shown in
|R|/Δs=1/tan α (3)
Summarizing the equations (1) to (3), relation among Fo, Fi, R, Δs, and μ is expressed in the following equation (4).
(−μ/|R|)·Δs·(Fo+Fi)=Fo−Fi (4)
Here, assuming that a distance from an insertion end of linear body 2 to point P is denoted as s, load applied to linear body 2 at point P is denoted as F(s), and a small distance from point P is denoted as Δs, Fi and Fo are expressed in the following equations (5) and (6), respectively.
Fi=F(s) (5)
Fo=F(s+Δs) (6)
Here, by substituting the equations (5) and (6) into the equation (4) and assuming that a radius of curvature at position P at distance s is denoted as R(s), the following equation (7) is obtained.
(−μ/|R(s)|)·Δs{F(s+Δs)+F(s)}=F(s+Δs)−F(s) (7)
Further, by approximating Δs to 0, a differential equation as shown in the following equation (8) is obtained. By solving the differential equation, the following equation (9) showing relation between Fo and Fi at a small distance ds of point P is obtained.
dF(s)/ds=−(2μ/|R(s)|)·F(s) (8)
Fo=Fi·exp(−2μ∫(1/|R(s)|)ds) (9)
By using the equation (9), even though portions where friction occurs are continuous, Fo can be found by designating a range of integration. In a case where linear body 2 is inserted in a catheter representing hollow tube 1, since a difference between an inner diameter of hollow tube 1 and an outer diameter of linear body 2 is small, it can conveniently be supposed that linear body 2 is continuously in contact with the inner wall of hollow tube 1.
In addition, when ds is close to 0, tan(dθ) can be approximated to dθ. Therefore, relation between R(s), ds and dθ is as shown in the following equation (10). Here, it is assumed that dθ is described as θ(s, s+ds) and dθ indicates an angle from s to s+ds. By inserting the equation (10) into the equation (9), the following equation (11) is obtained.
1/|R(s)|·ds=|θ(s,s+ds)| (10)
Fo=Fi·exp(−2μ∫(|θ(s,s+ds)|/ds)ds) (11)
In this equation (11), ∫(|θ(s, s+ds)|/ds)ds means division of small angle θ(s, s+ds) obtained by sectioning linear body 2 or hollow tube 1, from the inlet to the tip end of hollow tube 1, into small lengths ds by that small length ds and integration of that result with small length ds, and hence a result thereof turns out to be a total sum θ of degrees of bending of linear body 2 or hollow tube 1. Based on this equation (11), load Fo at the tip end of linear body 2 can be found based on total sum θ of degrees of bending of linear body 2 or hollow tube 1 from the inlet to the tip end of hollow tube 1 and load Fi in insertion of linear body 2. Since coefficient of friction μ may be different depending on combination of hollow tube 1 and linear body 2, it should only be measured in advance for each combination and selected for use depending on hollow tube 1 and linear body 2 to be used.
Fo=(Fi−β(θ))·(exp(−2μθ)−C) (12)
The equation (12) is a corrected version of the equation (11). Here, β(θ) is a function for correcting input load Fi with θ and C is a constant value for correcting influence by friction in an example where linear body 2 is straight (θ=0).
As can be seen in
Meanwhile, for example, the delivery wire is smaller in diameter at a position close to the tip end of the coil. Namely, flexural rigidity of linear body 2 is not uniform across positions in linear body 2 but is different from position to position. At such a position where flexural rigidity varies, a portion lower in flexural rigidity tends to bend more, which results in greater normal reaction Fh applied to hollow tube 1. In that case, depending on flexural rigidity EI at a position in linear body 2 and variation in flexural rigidity EI, the equation (12) is corrected to the following equation (13). In this case, equivalent μ should only be corrected. Therefore, coefficient of friction μ is expressed as a function of flexural rigidity EI(s), variation in flexural rigidity dEI(s)/ds and R(s), and this function is found in advance in experiments.
Fo=Fi·exp(−2∫μ(EI(s),dEI(s)/ds,R(s))·|R(s)|ds) (13)
In present Embodiment 1, degree of bending θ of hollow tube 1 or linear body 2 and load Fi in insertion of linear body 2 in the inlet of hollow tube 1 are detected, and load Fo applied to the tip end of linear body 2 is found based on the result of detection. Therefore, load Fo applied to the tip end of thin linear body 2 can readily be detected. Thus, an operator who is a doctor can accurately operate linear body 2 based on a detection value of load Fo at the tip end of linear body 2 and such medical malpractice as damaging a cerebral aneurysm or the like with the tip end of linear body 2 is prevented. In addition, as it is not necessary to attach a pressure sensor at the tip end, conventional linear bodies 2 can be used as they are and detection at low cost can be made.
Such treatment for embolizing cerebral aneurysm 7 is given while a human body is subjected to fluoroscopy using X-ray equipment. As catheter 3 is made of resin, it is not displayed in a fluoroscopic image. On the other hand, embolization coil 4 and delivery wire 5 are made of metal, they are displayed in a fluoroscopic image. A fluoroscopic image is normally a two-dimensional image, however, in treatment for embolizing cerebral aneurysm 7, in order to observe a state of embolization coil 4 in cerebral aneurysm 7, the X-ray equipment is of a revolving type, so that a three-dimensional image can be created from a plurality of two-dimensional perspective images taken while the X-ray equipment revolves.
In treatment for embolizing cerebral aneurysm 7, cerebral aneurysm 7 of which blood vessel wall is thin and fragile should be filled with embolization coil 4 so as not to cause rupture of cerebral aneurysm 7 and hence force Fo applied to cerebral aneurysm 7 by embolization coil 4 is desirably measured. In present Embodiment 2, degrees of bending θ of embolization coil 4 and delivery wire 5 within catheter 3 are summed based on fluoroscopic images, load Fi in inserting delivery wire 5 is measured, and force Fo applied to cerebral aneurysm 7 by embolization coil 4 is estimated.
X-ray equipment 10 takes a plurality of two-dimensional perspective images while revolving around a patient. Image synthesis device 1 creates a three-dimensional image from two-dimensional images taken by X-ray equipment 10. Degree-of-bending detection device 12 detects degree of bending θ of embolization coil 4 and delivery wire 5 based on the three-dimensional image created by image synthesis device 1. Insertion load detection device 13 detects load Fi in insertion of delivery wire 5. Storage device 14 stores coefficient of friction μ between embolization coil 4, delivery wire 5 and catheter 3 measured in advance.
Arithmetic processing unit 15 calculates load Fo at the tip end applied to cerebral aneurysm 7 by embolization coil 4, based on degree of bending θ of embolization coil 4 and delivery wire 5 detected by degree-of-bending detection device 12, load Fi in insertion of delivery wire 5 detected by insertion load detection device 13, and coefficient of friction μ stored in storage device 14. This calculation method is as described in Embodiment 1. Display device 16 displays load Fo at the tip end. A doctor gives embolizing treatment while viewing load Fo at the tip end displayed on display device 16.
Though a degree of bending of delivery wire 5 or the like during coil embolization is found in Embodiment 2, a degree of bending of delivery wire 5 or the like before treatment is found in present Embodiment 3. In treatment for embolizing cerebral aneurysm 7 with a coil, in order to check a size and presence of cerebral aneurysm 7 before treatment, an X-ray CT (computerized tomography system) or an MRI (nuclear magnetic resonance imaging system) is used to take a three-dimensional blood vessel image as shown in
In treatment, catheter 3 is inserted from an artery at the base of a femoral region and sent from an aorta 20 through a carotid artery 21 (or a vertebral artery 22) and cerebral artery 6 to cerebral aneurysm 7. As catheter 3 is bent along the blood vessel, bending of embolization coil 4 and delivery wire 5 that pass therethrough is also substantially the same as bending of the blood vessel. Therefore, by using a degree of bending of a blood vessel path to cerebral aneurysm 7, force applied to cerebral aneurysm 7 by embolization coil 4 can be guessed as in Embodiment 2.
Specifically, after the three-dimensional blood vessel image as shown in
Though centerline 23a of blood vessel 23 is found after a path of blood vessel 23 is extracted in present Embodiment 3, a centerline of the entire blood vessel may be found in image processing in advance and then a path of a blood vessel through which catheter 3 passes may be found based on the path of the centerline.
By combining fluoroscopic two-dimensional image 24 and a three-dimensional blood vessel image 25 taken prior to a surgical operation with each other, however, a degree of three-dimensional bending of linear body 2 can be estimated. Since linear body 2 has been inserted in blood vessel 23 and in addition a path 26 from an insertion port to a destination (cerebral aneurysm 7) has been known, a position of linear body 2 in three-dimensional blood vessel image 25 can be known by matching fluoroscopic two-dimensional image 24 and three-dimensional blood vessel image 25 with each other. Thus, by using a degree of three-dimensional bending of blood vessel 23, degree of three-dimensional bending θ of linear body 2 can be known. Therefore, even during insertion of linear body 2 in a human body, load Fo at the tip end of linear body 2 can be estimated.
Linear body 2 such as delivery wire 5 is inserted in hollow tube 1 as it passes between rollers 30 and 31. Drive roller 31 is rotatably driven by motor 32. Torque control circuit 33 supplies a drive current to motor 32 in accordance with a torque command value and outputs a signal indicating a drive current value to arithmetic processing unit 15 in
As the drive current is supplied from torque control circuit 33 to motor 32, motor 32 rotatably drives rollers 30 and 31 at a low speed so that linear body 2 is inserted in hollow tube 1. Arithmetic processing unit 15 in
According to present Embodiment 5, load Fi in insertion of linear body 2 can readily be detected.
When the drive current is supplied to motor 32, motor 32 rotatably drives rollers 30 and 31 at a low speed so that linear body 2 is inserted in hollow tube 1. Arithmetic processing unit 15 in
According to present Embodiment 6 as well, load Fi in insertion of linear body 2 can readily be detected.
A tapered input and output port 42 is formed at each of opening portions at respective opposing ends of through hole 41, for facilitating insertion and extraction of linear body 2. In a restraint portion 43 in the rear of input and output port 42, a diameter of through hole 41 is slightly greater than a diameter of linear body 2, and it is set, for example, to 105% to 120% of the diameter of linear body 2. Therefore, in restraint portion 43, linear body 2 cannot move in a direction other than a direction of longitudinal axis.
When insertion load Fi in the direction of longitudinal axis is applied to linear body 2, main body portion 40 defines a direction of curve of linear body 2 within through hole 41. Namely, through hole 41 is bent between two restraint portions 43 and linear body 2 passes through through hole 41 while bending along one wall. In addition, through hole 41 forms a space 44 between two restraint portions 43, that extends toward a wall along which linear body 2 does not extend. Therefore, in space 44, an operation of linear body 2 in a direction in parallel to the sheet surface is not restricted by through hole 41.
On the other hand, in input and output port 42 and space 44, a height of through hole 41 in a direction perpendicular to the sheet surface is slightly greater than a diameter of linear body 2, and it is set, for example, to 105% to 120% of the diameter of linear body 2. Therefore, an operation of linear body 2 in the direction perpendicular to the sheet surface is restricted by through hole 41. Namely, in input and output port 42 and space 44, a cross-sectional shape of through hole 3 in a cross-section perpendicular to the direction of longitudinal axis of linear body 2 is rectangular as shown in
As shown in
As shown in
The illumination light emitted from light source device 46 is incident on line sensor 45 where linear body 2 is absent, however, it is cut off by linear body 2 where linear body 2 is present and is not incident on line sensor 45. In other words, a shadow of linear body 2 is cast on line sensor 45. A large photocurrent is generated in light-receiving element 45a that receives the illumination light, but a photocurrent is hardly generated in light-receiving element 45a located in the shadow of linear body 2. Therefore, by detecting a photocurrent of each light-receiving element 45a, a position of linear body 2 within space 44, that is, height h of curve of linear body 2, can be found.
The insertion load detection device further includes a storage portion 47 and a signal generation portion 48. Storage portion 47 stores a table showing correlation between height h of curve of linear body 2 and insertion load Fi. Signal generation portion 48 finds height h of curve of linear body 2 by detecting a photocurrent of each light-receiving element 45a, finds insertion load Fi corresponding to that height h by referring to the table in storage portion 47, and outputs a signal ΦFi indicating that insertion load Fi to arithmetic processing unit 15 in
According to present Embodiment 7 as well, load Fi in insertion of linear body 2 can readily be detected.
A tapered input and output port 52 is formed at each of opening portions at respective opposing ends of through hole 51, for facilitating insertion and extraction of linear body 2. A diameter of through hole 51 is slightly greater than a diameter of linear body 2, and it is set, for example, to 105% to 120% of the diameter of linear body 2. Through hole 51 is bent in an arc shape in a central portion in a direction of length, and linear body 2 passes through through hole 51 while it is bent. An elastic member 53 is embedded on an outer side (an upper side in
Linear body 2 is inserted in through hole 51 as it is bent. Therefore, when insertion load Fi is applied to linear body 2, a central portion curved in an arc-shape tends to further bend and a pressure is applied to strain sensor 54 through elastic member 53. Therefore, load Fi in insertion of linear body 2 can be detected based on an output signal from strain sensor 54. Arithmetic processing unit 15 in
According to present Embodiment 8 as well, load Fi in insertion of linear body 2 can readily be detected.
For example, the device shown in Embodiments 7 and 8 is used as insertion load detection device 56. Insertion load detection device 56 and Y-connector 8 may integrally be formed. Linear body 2 is inserted in catheter 3 through insertion load detection device 56 and Y-connector 8. A degree of bending of linear body 2 is found, for example, with the method shown in Embodiments 3 and 4.
An output signal from insertion load detection device 56 is provided to an operation device 58 through a cable 57. A display 59, a speaker 60 and a switch 61 are connected to operation device 58. Operation device 58 finds load Fo at the tip end of linear body 2 based on the output signal from insertion load detection device 56, a degree of bending of linear body 2, and the like.
Display 59 provides visual display of load Fo at the tip end or insertion load Fi by using numerics. Speaker 60 gives aural notification of load Fo at the tip end or insertion load Fi by using tone, volume or the like. Switch 61 switches between display 59 and speaker 60, for providing display or giving notification of any of load Fo at the tip end and insertion load Fi. A doctor can know load Fo at the tip end or insertion load Fi by viewing display on display 59 or listening to sound from speaker 60, and operates linear body 2 based thereon.
An operator in training operates linear body 2 while viewing a simulated perspective image displayed on monitor 63 and insertion load Fi or load Fo at the tip end displayed on display 59 and further listening to sound from speaker 60 indicating insertion load Fi or load Fo at the tip end. The simulated perspective image, insertion load Fi and load Fo at the tip end during operation are recorded in a video image recording medium within a video image recording apparatus (not shown). The record is utilized for training or evaluation of an operator. In addition, the video image recording medium records a simulated perspective image, insertion load Fi, load Fo at the tip end, and a commentary by a person of skill at the time when he/she operates linear body 2 in simulator 62. A less experienced operator can reproduce the operation records of the person of skill and learn his/her manipulation.
According to present Embodiment 10, manipulation of a skilled operator can be quantified and transferred to a less experienced operator, so that manipulation of the less experienced operator can quickly be improved.
It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-323670 | Dec 2007 | JP | national |
| 2008-266365 | Oct 2008 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2008/072030 | 12/4/2008 | WO | 00 | 6/14/2010 |
