|Title of Invention||
TACTILE INTERFACE DEVICE FOR NODULE PALPATION IN A PERCEPTION ENHANCED FORM
|Abstract||A tactile interface device for nodule palpation in a perception enhanced form comprises a deformable force stretch array sensor comprising plurality of components comprising plurality of first major components (la , 5) and plurality of second major components (10). The first major components have predetermined rigidity; and said second major components are operatively interconnected with each of the first major components. The device comprises actuator means for indwelling nodule simulation, being operatively connected with said deformable force stretch array sensor, and adapted to provide perception of the nodule in the body.|
|Full Text||FIELD OF INVENTION
The present invention relates to a tactile interface device for nodule palpation in a perception
enhanced form. More particularly, the invention relates to a tactile interface device
comprising a deformable force stretch array (DFSA) sensor and an actuator for nodule
palpation in a perception enhanced form adapted for medical diagnosis.
BACKGROUND AND PRIOR ART
In clinical practice doctors routinely palpate the patient's body with the fingers and palm to
detect indwelling lumps and smaller nodules. However, correct diagnosis of pathological
conditions such as the presence of tumor and lumps can be obtained only through expert
palpation. Moreover, even when the nodule is detected, estimation of its clinically significant
parameters such as its size and depth below the skin surface poses considerable difficulties.
Thus, there is a need for sensors that can augment palpation acuity for nodules, especially in
homogeneous body tissue such as the breast. However, there are still considerable unknowns
regarding how the palpating hand actually senses a nodule, with a number of scientific
controversies on this subject.
M. H. Lee, H. R. Nicholls, Review Article Tactile sensing for mechatronics-a state of the art
survey, Mechatronics, ED-9 ( 1) ( 1999) 1 31 indicates that there are sensed parameters other
than force and pressure. Additional parameters such as slippage, shear and hardness are more
difficult to define and quantify by sensor technology. Moreover, sensed parameters in
palpation for a breast nodule using several fingers and the palm differ from that for palpation
with one finger as for example for feeling the wall 'rigidity' of the radial artery at the wrist.
Nevertheless, palpation for the former case seems to assess a combination of point forces,
global 'hardness' and its regional variations together with skin shape changes.
The earliest approach, which was used to model such a scenario, was an array of sensor
elements oriented to measure pressure normal to the surface. R. F. Wolfenbuttel, P. P. L.
Regtien, Polysilicon bridges for the realization of tactile sensors. Sensors and Actuators A -
Physical, ED-26 ( 1-3) ( 1991) 257 264 reported some of the earliest tactile sensor designs
utilizing silicon fabrication technology. Their sensor designs for arrays of force sensing
elements use piezoresistive and capacitive transduction principles.
C. Domenici, D. De Rossi, A stress-component-selective tactile sensor array, Sensor
andActuatorsA-Physical, ED. 31 (1-3) (1992) 97 100 reported a stress.component-selective
tactile sensor array. The array was developed with the aim of obtaining a skin-like sensor
able to perform fine-form discrimination of objects in contact with it. A tactile transducer for
pressure distribution measurement on the sole of the foot was reported in J. Volf, S. Holy, J.
Vlcek, Using of tactile transducer for pressure-distribution measurement on the sole of the
foot. Sensor and Actuators A-Physical, ED-62(l-3) (1997) 556 561 The tactile carpet is
based on conductive rubber of Japanese origin and uses standard tactel arrays.
S. Omata, Y. Terunama, New tactile sensor like the human hand and its applications, Sensor
and Actuators A-Physical, ED- 35 (1) (1992) 9 15, reported a new tactile sensor that was
able to detect the hardness/softness of an extraneous substance impressed upon it. The sensor
has a piezoelectric resonator and works on the principle that contact with an object will cause
a change in its resonating frequency. A similar purpose active tactile sensor for detecting
contact force and hardness of an object has been reported in M. Shikida, T. Shimizu, K. Sato,
K. Itoigawa, Active tactile sensor for detecting contact force and hardness of an object,
Sensor and Actuators A-Physical, ED- 103 (1-2) (2003) 213 218. A sensor system consisting
of a piezoelectric (PZT) transducer and a pressure sensor element has also been reported in
S. Omata, Y. Murayama, C. E. Constantinou, Real time robotic tactile sensor system for the
determination of the physical properties of biomaterials, Sensor and Actuators A-Physical,
ED- 112 (2-3) (2004) 278 285 for the determination of biomaterials' properties. The sensor
developed uses the strain gauge element to detect contact pressure in addition to employing
similar principles for the PZT disc transducer as outlined above. Work on other related force
and stress sensors having tactile applications has also been reported in several publications.
US6726638 discloses a direct manual examination of remote patient with virtual examination
US6428323 relates to a system for teaching students to perform medical exams performed
manually inside a body cavity. The device has an anatomical simulator with a simulator
cavity, a tactile sensor in the simulator, and a feedback presentation unit in communication
with the sensor. This device is that it is only suitable for cavities. Further the device does not
give a tactile perception and is not suitable for diagnostic examination but more for medical
US6336812 relates to a clinical and/or surgical training apparatus in which there is a housing
providing a simulation of at least part of a body and a plurality of simulations of internal
body structures for reception in the housing, these simulations being a set of simulations of a
particular part of the anatomy and being of increasing anatomical complexity and/or
presenting increasing clinical or surgical difficulty. The limitation however with the system is
that it gives anatomical display of body organ as told in the databank and such display is not
related to an individual patient. The device is suitable for medical teaching and not effective
for clinical diagnosis.
US Patent Application No.20030219705 relates to an interactive breast examination training
model which is used for the training of physicians and other medical personnel on techniques
for clinical breast examinations. The device cannot be linked to an actual patient examination
and the factor of elasticity of skin has not been taken into account for the purpose of the
examination. Moreover, the system is suited for training and not actual treatment.
WO 02/43558 describes a device in which the elasticity of a human or animal organ is
measured by the generation of an ultrasonic signal after ultrasonic illumination which are
represented in the form of two or three dimensional form. The device has several drawbacks
and the most critical being that it gives only force feedbacks.
Additional parameters such as slippage, shear and hardness are more difficult to define and
quantify by sensor technology. Sensed parameters in palpation for a breast nodule using
several fingers and the palm differs from that for palpation with one finger as for example for
feeling the wall 'rigidity' of the radial artery at the wrist. Palpation to detect the presence of a
tumor within a living body essentially is a task of contact pressure and shear force
distribution mapping and spatial discrimination. The earliest approach, which was used to
model such scenario, was an array of sensor elements oriented to measure pressure normal to
While the art reported deals with several aspects of tactile sensors but there is a long felt need
to provide a tactile sensor that can identify small and deep seated nodules embedded in
homogenous tissue to provide a reliable means for nodule detection in the breast.
The present inventors have found that a tactile interface device comprising a novel deformable
force stretch array (DFSA) sensor designed in a manner that it can augment palpation for
nodules, even the small and deep-seated nodules of homogeneous tissue and can transduce the
perception of the nodule with enhanced sensitivity.
OBJECTS OF INVENTION
Thus the basic object of the present invention is to provide a tactile interface device comprising
deformable force stretch array (DFSA) sensor and an actuator for accurate identification of
small and deep seated nodules.
Another object of the present invention is to provide a tactile interface device comprising
deformable force stretch array (DFSA) sensor which can also be used for diagnosing actual
information from an object which is not capable of being directly palpated.
Another object of the present invention is to provide a tactile interface device comprising
deformable force stretch array (DFSA) sensor and an actuator for routine diagnosis.
SUMMARY OF INVENTION
Thus according to the basic aspect of the present invention there is provided a tactile interface
device for nodule palpation in a perception enhanced form as if said nodule is larger and closer
to palpating hand, said device comprising:
(i) a deformable force stretch array sensor and/or sensor comprising
plurality of components comprising one or more first major components
and one or more second major components; wherein said first major
component has predetermined rigidity; and said second major
component is operatively interconnected with the first major
components; whereby solid angle subtended on said palpating hand
surface is relatively more than solid angle subtended at said nodule and
(ii) actuator means for indwelling nodule simulation, being operatively
connected with said deformable force stretch array sensor, and adapted
to provide perception of the nodule in the body.
DETAILED DESCRIPTION OF INVENTION
The tactile interface device of the present invention enables nodule palpation in a perception
enhanced form. This is possible due to the combination of the deformable force stretch array
(DFSA) and the three dimensional actuator. The various components of the DFSA have been
designed and combined so as to identify a nodule by the interpretation of the deformable force
stretch array data.
The deformable force stretch array (DFSA) sensor and/or sensor comprises plurality of
components comprising first major component and second major component. The first major
component comprises one or more transducers (tactels), preferably ten in number, which are
deformable but are more rigid than body tissue part to be palpated. This differential in
deformability mimics the fact that the palpating hand is less deformable than the body part
palpated. The said transducers or tactels are standard strain gauges that are attached to spring
leafs and are provided with miniature cylinder and piston guides. The latter ensures linear
tactel tip movement perpendicular to the tactel base
The second major component comprises one or more elastic stretch elements adapted to bridge
the tips of the tactels and conform to the body surface contour in between the tactels without
exerting significant force onto the body. These elements are stretch sensors giving length
proportional output. Thus the inter-tactel spaces can be assessed.
Additionally when the sensor base is tilted the relative extensions of the various stretch
elements provide an indication of the shape of the indwelling nodule within the surrounding
soft tissue of the body.
In the DFSA's system the input side of the tactile interface is the tactile sensor array, DFSA,
which is a combination of vertical deformable force sensing tactels with linked electrical
resistance varying stretch elements. The system enables the analysis of the tactel force and
the extension of the stretch elements gives a very good indication of small and deep seated
nodules. The device is pressed on the body and the tactel-stretch element data is processed to
corresponding electrical signals determines the presence of a nodule, size of the nodule and
location of the nodule.
When the three dimensional actuator is pressed with the hand gives a feel of nodule presence.
This actuator is physically co-operatively located above the sensor array but there is no
mechanical linkage between the two subunits. The processed electrical signals from the
sensor array by feed-forward control modifies the bulk elasticity; size of phantom nodule;
and location of the phantom nodule. The three dimensional actuator when touched by hand
gives the feel of the phantom nodule. As a result of the interpretation of the DFSA data and
feedback control of the phantom nodule gives a better perception than the actual nodule
palpated without the help of the system according to the invention.
The signals from the DFSA are processed by the amplification and signal-processing unit and
are subsequently transmitted to the actuator controls. The actuator controls regulate the size
and shape of the nodule as well as the general tissue and skin elasticity perceived by the
doctor's hand. The actuator consists of a pouch, which can be filled with fluid, placed inside
a cubical box. The cubical box provides the structural framework for the fluid filled pouch,
which serves as the body tissue analog. It is filled with fluid - usually water - by means of a
tube that opens into the pouch. A syringe controls the flow of water through the tube. The
syringe itself is operated by a slider crank mechanism powered by a DC motor. By means of
the above arrangement, it is possible to regulate the water inside the body tissue analog to the
tune of micro-liters.
The power provided by the DC motor depends on the processed DFSA signals that indicate
the bulk elasticity of the body tissue. In accordance with the signals, the amount of liquid to
be input through the tubes is estimated. For example, if a hard body tissue is sensed then the
DC motor is regulated to a larger input power such that more fluid is pumped in to the
diaphragm. This gives a perception of a harder body tissue to the hand that is in contact with
the actuator. Above this fluid-filled diaphragm, a latex sheet is stretched out and connected
to a tensioning motor. This motor is controlled by the DFSA signals that indicate the skin
elasticity of the body part. The sheet is stretched out more if the body part is sensed by the
DFSA to have "tighter" skin and vice-versa. These two separate arrangements together give a
combined feel of the elasticity of the skin and tissue being sensed.
The phantom nodule is placed inside the body tissue analog. A spherical bag, which can be
filled with fluid, simulates the phantom nodule. It is positioned by means of a X-Y-Z control
(e.g., a probe), which is in turn controlled by the DFSA position and depth information. The
size of the bag is varied in a similar fashion to the variation of elasticity of the body tissue
analog. Depending upon the DFSA nodule size information, the phantom nodule is filled with
water by a variable pressure pump. A mechanism similar to the syringe-slider crank-DC
motor arrangement described above could be used. Thus, the position, depth and size of the
phantom nodule are subjected to fine control in the 3-D actuator setup. Consequently, the
user gets an enhanced perception of the actual nodule that is detected in the body part by the
WORKING OF INVENTION
Case I: Force exerted on the transducers (tactels)
2-D analysis, where tactels along a particular Z-column are subjected to the same force, is
undertaken to simplify the contact elasticity problem. Uniform vertical pressure 'p' acts on
the rigid tactel base having width 'b', depth 'd' and length 'L' where d base is treated as a semi-infinite body.
Further, the force exerted on the base is considered as a combination of infinite number of
line loads along the X-axis that give a uniform pressure distribution 'p' on the base. Each of
these line loads ' W' exerts stress on any given point on the lower surface of the slab (the
surface on which the tactel elements are attached). As per standard solid mechanics analysis,
due to a line load on the surface of a semi-infinite body, the following equation is achieved :
where (r, 0) defines the position of the point with respect to the line load. Therefore, the
stress in the Y-direction at the point x = xi due to the line load W in terms of p is given by:
Substituting rcos9 = d which restricts the domain to the top surface loading in Eq. (4) and
integrating for all such line loads, the line load equation is
Thus for equilibrium, the sum of all the tactel reaction forces is equal to the total force on the
base undersurface. Thus, the force on each tactel is calculated by dividing the entire slab A
into NxM portions (where there are NxM tactels) - each such portion being treated as the
"zone of influence" of the respective tactel. Force transmitted onto a particular tactel is then
calculated as the total force that corresponds to its zone of influence on the base
where Fi is the force transmitted onto the ith tactel and N and M are the number of total tactels
along the X and Z axes respectively.
Case II: Deformation of the transducers (tactels)
The tactel deformation is determined by calculating the contact pressure at the tactel-slab
interface needs. The displacement and the force on the tactile element are related by the
following equation (7)
E1 = elasticity of the tactels,
E2 = elasticity of slab A,
a = contact radius, and
d = total displacement of the contact point.
The localized deformations of the tactels and the slab A at the interface are estimated from
the following Eqs. (8, 9):
where d1 = deformation of the tactel,
h = nominal length of the tactel,
pc = contact force,
A = area of tactel tip.
By the superposition principle, the displacement of the contact point at the tactel-slab
interface is equal to the sum of the deformations of the two bodies in contact. Thus,
From Eqs (7, 8, 9, 10), the following equation is achieved:
Therefore, the deformation of the tactile element d1 is determined by evaluating pc from Eq
(11) and substituting the value obtained in Eq (8).
Case III: Deformation of the stretch elements
The slab A applies a normal pressure ps(x) on the stretch element between x = -a and x - a
(the end points of the stretch element) thereby causing a vertical displacement v(x). ps(x) is
estimated in terms of the forces acting on the tips of the tactels (from Eq. (6)) to which the
stretch element is joined.
The surface displacement distribution due to a line load of Ws per unit length acting
vertically at x = § is given by:
v = v for plane stress approximation,
E and v are the elastic material constants for the stretch elements.
Analysis for sensor pressed onto a body tissue analog with a nodule
Deformation of transducers (tactels) and extension of the stretch element:
To analyze the presence of two separate displacement fields is taken into account: the
displacement field (81) due to top surface loading of tactel base and the displacement field (u)
due to the presence of a rigid nodule I (Enodule>> E2). The net deformation is calculated by
the superposition of these two fields.
The governing equation for the displacement field u of the elastic slab, in the presence of the
rigid nodule I, is given by:
The displacement on the nodule surface is zero (the 'no flux condition') since the nodule is
significantly more rigid as compared to the surrounding slab. Thus, the following boundary
condition is ahieved:
where v is the unit exterior normal to d1 and r is any infinitesimal rigid displacement.
Knowledge of the parameters of I enables the determination of the displacement field u. Eqs
(13, 14) are analogous to fluid mechanics formulations where the flow past a solid object is
computed. The stream function (?), analogous to the displacement function, satisfies a
similar governing equation as Eq (13) coupled with the no flow (zero velocity) condition
across the boundary of the solid object (similar to Eq (14)). The stream function ? for flow
past a cylinder of radius r is obtained by combining the expression of stream function for a
doublet with that for rectilinear flow and is given by:
where v0 is the velocity of uniform flow in the x-direction.
Similarly, the displacement function u of an elastic slab having an embedded nodule of
radius r at a depth of dnodulc is:
where k is a dimensionless parameter that depends on the impressed traction pressure and
the equivalent elasticity of the slab tactile combination (keq).
From Eq. (16) and Eq. (8) the net tactel deformations are obtained. From these deformations,
the contact forces at the slab-tactel interface are estimated. This leads to the determination of
the extension of the stretch elements using Eq. (12).
The invention will now be described with reference to non-limiting embodiment of the
invention illustrated in the accompanying drawings.
BRIEF DESCRIPTION OF ACCOMPANYING FIGURES
Figure 1 illustrates DFSA sensor configuration with sensor pressed upon a deformable slab.
Enlarged view of a tactile element (tactel) is shown on the top left corner. A strain gauge is
attached to a spring leaf, which is joined to a piston-cylinder guide. The combination is fixed
on the tactel base. Enlarged view of the stretch element conforming to the contour of the slab
material, bulging upwards in between the tactel tips, is shown on the top right corner.
Figure 2 illustrates schematic view of three dimensional actuator of the present invention.
Figure 3 illustrates comparison of tactile strain without nodule (diamonds), with nodule of 8
mm diameter (crosses) and with nodules of 16 mm diameter (circles). Nodule depth = 50
Figure 4 illustrates comparison of inter-tactel slab material bulge without nodule (diamonds),
with nodule of 8 mm diameter (crosses) and nodules of 16 mm diameter (circles). Nodule
depth = 50 mm.
Figure 5 SI and BI graphs for different nodule sizes and depth. For deriving the size and
depth data from experimental values of SI and BI a representative example of marking for
SI=9.6 and BI=5.6 is shown.
DETAILED DESCRIPTION OF ACCOMPANYING FIGURES
In figure 1 DFSA sensor configuration with sensor pressed upon a deformable slab is
illustrated. The slab body (8) as shown bulging upwards between the tactel tips. Enlarged
view of a tactile element (la) (tactel) is shown on the top left corner (Please see view X).
From view X it is realizable that the sensor device comprises tactel base (1) which is
substantially rectangular having rigid base upon which the linear guide (6) is attached along
with the strain gauge (2) and leaf spring (3). It has height 'd' and length '1' and width 'b' in
the Z-direction (not shown in the figure). The Strain gauge (2) measures the strain of each
tactel (la). The strain gauge (2) has a gauge factor ranging from 1.5 to 150 and resistance
ranging from 50 to 5000 ohms. Spring leaf (3) is attached to the strain gauge (2) which are
both connected to the linear guide (6). The leaf (2) bends proportional to the tactel force.
The linear guide (6) is constituted by an arrangement of cylinder (4) and piston (5) and
ensures linear tactel tip movement perpendicular to the tactel base (1).
The tactel (la) is constituted by the strain gauge (2), spring leaf (3) and linear guide (6) and
has a nominal length of 'h'. In the embodiment shown in Figure 1 the tactels (la) are ten in
number. Stretch element (10) joins the tips of the tactel (la).
Nodule (9) is embedded in Body (8) and the sensor is placed on the body part (or as in this
experimental case the homogeneous slab) during palpation. When the sensor is placed on the
body multiple bulges dissimilar in shape and magnitude are created between different pair of
tactels and the maximum bulge is limited to the bulge(max) (12) of the stretch element (10).
Tactels (5) ensure linear tactel tip movement perpendicular to the tactel base.
The differential in deformability mimics the fact that the palpating hand is less deformable
than the body part palpated. Only when such a condition prevails can the tissues of the body
part be compressed to get a feel of underlying nodule. If the reverse condition occurs, as
happens for the very rigid abdomen in peritonitis, the palpating hand is unable to discern
The elastic stretch elements (10) bridge the tips of the tactels and conform to the body surface
contour in between the tactels without exerting significant force onto the body. These
elements are stretch sensors that give length proportional output. Thus the inter-tactel tissue
bulge can be determined. The stretch elements provide a combination of geometric (such as
nodule curvature) and dynamometric (such as elasticity) information about the body tissue.
Biomechanical analysis of a human body palpation model comprising of DFSA pressed upon
a homogenous elastic slab containing a hard nodule shows that the sensor enables
identification of the location of relatively small and deep seated nodules. The DFSA is able to
estimate the nodule position, size and depth as well as the elasticity of the surrounding body
tissue. Normally a nodule would have size between 5-15 mm. Larger sizes are referred
to as "lumps". An 8 mm nodule occurring at a depth of from 3- 50 mm in homogeneous tissue
can be sensed by the DFSA.
In figure 2 schematic view of three dimensional actuator of the present invention is illustrated.
The rubber sheet (13) is stretched out and connected to the skin tensioning motor (14). It
simulates the skin surface. The skin tensioning motor (14) tensions/stretches the rubber sheet
(13). A Fluid filled bag (15) serves as the body tissue analog. A phantom nodule (21) that is
placed inside the bag (15). The X-Y-Z control (16) controls the position of the phantom
nodule (21). Its operation is controlled by the DFSA signals of nodule depth and location. A
variable pressure pump (18) is used to pump fluid into the bag (15). Another Variable
pressure pump (19) is used to pump fluid into the phantom nodule (21) XYZ control (16).
Control signals (20) are generated by sensor, signal processor and actuator controls (22) are
sent to the variable pressure pumps (18) and (19). The DFSA sends signals to the signal
processor, which sends the processed signal to the actuator control as shown in the figure (2).
In figure 3 comparison of tactile strain without nodule (diamonds), with nodule of 8 mm
diameter (crosses) and with nodules of 16 mm diameter (circles). Nodule depth = 50 mm. is
illustrated. The elasticity of the slab (8) is 0.075 times the elasticity of the tactels
(E2=0.075xE,) It is realizable from the figure that the strain difference between the central
tactels (numbers 5 and 6) and the extreme peripheral tactels (numbers 1 and 10) is a
parameter of significance. It has a value of 0.0096, 0.0237 and 0.0648 for the cases of no
nodule, an 8 mm nodule at a depth of 50 mm and a 16 mm nodule at a depth of 50 mm being
embedded in the homogeneous slab. This is also illustrated in table A given below. The
presence of nodule thus gives a marked difference from the control experiment result. These
figures suggest that a strain difference of 0.02 or more is indicative of the presence of nodule
of size over 8 mm at 50 mm depth. With non-deforming tactels such detection would not
have been possible.
In figure 4 comparison of inter-tactel slab material bulge without nodule (diamonds), with
nodule of 8 mm diameter (crosses) and nodules of 16 mm diameter (circles). Nodule depth =
50 mm is illustrated. Inter-tactel tissue bulge is quantified by the stretch elements and
improves nodule detection. A "bulge parameter" (Bp - average inter-tactel tissue bulge
divided by inter-tactel distance) is computed for nodules of various sizes (Fig. 4). Bp for the
no-nodule case is close to zero throughout the sensor array while for the 8 mm and the 16
mm nodules this value is considerably larger. Therefore an average bulge/inter-tactel distance
value of over 0.1 indicates the presence of nodule and together with the tactel strain data is
able to give unambiguous determination of the presence or absence of a nodule of 8 mm or
over in size at a depth of 50 mm or less.
In figure 5 SI and BI graphs for different nodule sizes and depth for deriving the size and
depth data from values of SI and BI a representative example of marking for SI=9.6 and
BI=5.6 is illustrated. The data of the graphs are restructured by computing two parameters
termed STRAIN INDEX (SI) and BULGE INDEX (BI), where
Central tactel strain - Peripheral tactel strain
Peripheral tactel strain
Averagebulgeincentralstretchelement - Average bulge in peripheralstretch element
Average bulge in peripheralstretch element
In the expressions for both the parameters, slab elasticity figures in the numerator as well as
in the denominator. Consequently, the resultant indices become independent of the body
elasticity value. The SI and B1 values have been computed for various nodule sizes and
depths and are represented in in the figure.
In figure 6 lines parallel to the abscissa represents specific SI and BI values of SI=9.6 and
BI=5.6. An intersection with both SI and B1 graphs which gives the same nodule size and
depth is the correct match which gives nodule size of 23 mm at a depth of 40 mm. Similarly,
for other experimental values of SI and BI the nodule size and depth data can be obtained.
A DFSA sensor prototype of the present invention comprises a strain gauge attached to a
phosphor-bronze spring leaf, which is again operatively connected to a miniaturized piston-
cylinder arrangement. The cylinder is realized using a 16 gauge hypodermic needle and the
piston with a sewing needle having a sliding fit within the lumen of the hypodermic needle.
The strain gauges used have a resistance of 120 ohms (O) and a gauge factor of 2. This setup
makes up one tactel, which has a nominal length of 10 mm. The tactels are attached to a hard
plastic base and juxtaposed to each other having predetermined spacing between each of the
tactels. The predetermined spacing is maintained at 10 mm by the use of suitable washers. For
the stretch elements, carbon compound impregnated conductive elastomers, manufactured by
Timpac Engineers, India, are used. The ends of each of these elastomers are fixed to tactel tips.
As the spacing between the tactels is 10 mm, the nominal length of the stretch elements is also
Experiments with the prototype built DFSA sensor are carried out on a variable elasticity
model. The variable elasticity model comprises sponge, with a nodule embedded in it, kept
inside a hard plastic box. The sponge is soaked with varying quantities of water to simulate a
variable elasticity model. This is performed by means of a water-air cylinder arrangement,
where a thin tube connects the water volume in the cylinder to the sponge and another tube is
provided with pressure gauge and bellows adapted to control air column in the cylinder. The
top surface of the sponge is covered with a rubber diaphragm so as to prevent water leakage.
The diaphragm, however, does not exert any significant force on the sponge.
When the diaphragm is palpated some water from the sponge is squeezed out into the water-air
cylinder. However, the air in the cylinder gives an 'elastic' reaction which alters the equivalent
elasticity of the water soaked sponge and thus maintains equilibrium in the setup. There is a
pressure gauge attached to the air tubing so that the air pressure can be monitored and the
appropriate amount of 'elastic' reaction can be given to the water-soaked sponge. Thus the
setup is able to regulate the equivalent elasticity felt by the palpating hand. Fig. 3 shows the
experimental validation system.
The tactile interface device is advantageous in teaching of medical students and such like
applications where in they get more perception enhanced feel initially and as they get more
skilled the level of help from the tactile interface decreases. The enhancement is perception is
such that as if the nodule is larger and closer to palpating hand.
In telemedicine applications where a robot or an unskilled person presses the sensor with
uniform pressure on the body part under inspection. The expert sits in a different place and
gets the perception of the nodule - if any are present in the said body part.
This device is advantageous in applications where the surgeon or the examiner cannot touch
the skin of the patient directly due to infectious diseases or some other reason. In such a case
this interface could act as an ideal contraption, where the examiner still gets the feel without
having to physically touch the patient's body. It is also important to note that wearing gloves
or such protective gear prohibits any significant tactile feedback from reaching the examiner.
1. A tactile interface device for nodule palpation in a perception enhanced form as if said
nodule is larger and closer to palpating hand, said device comprising:
(i) a deformable force stretch array sensor and/or sensor comprising plurality
of components comprising one or more of first major components and one
or more of second major components; wherein said first major component
has predetermined rigidity; and said second major component is
operatively interconnected with the first major component; whereby solid
angle subtended on said palpating hand surface is relatively more than solid
angle subtended at said nodule and
(ii) actuator means for indwelling nodule simulation, being operatively
connected with said deformable force stretch array sensor, and adapted to
provide perception of the nodule in the body.
2. A tactile interface device as claimed in claim 1, wherein the actuating means
comprises phantom nodule located in a body tissue analog such that positioning and
size of phantom nodule is controllable by deformable force stretch array sensor.
3. A tactile interface device as claimed in claims 1 and 2, wherein the actuator means
comprises three dimensional actuator physically co-operatively located above the
sensor array such that data from stretch sensors being processed to corresponding
electrical signals from the sensor array modifies the bulk elasticity; size of the phantom
nodule; and location of the phantom nodule by feed-forward control and wherein the
three dimensional actuator is adapted to provide enhanced feel of nodule presence in
the body, when pressed.
4. A tactile interface device as claimed in claim 1, wherein said first major components
comprise plurality of transducers being more rigid than body tissue part to be palpated
comprises plurality of deformable strain gauges adapted to analyze the force on the
5. A tactile interface device as claimed in claim 4, wherein strain gauges comprises
resistance of 50 to 5000 ohms and gauge factor of 1.5 to 150.
6. A tactile interface device as claimed in claims 4 and 5, wherein strain gauges comprises
resistance of 120 ohms and gauge factor of 2.
7. A tactile interface device as claimed in any of claims 4 to 6, wherein each of the
transducers of the plurality of transducers are in juxtaposition to each other having
predetermined spacing using suitable washers such that the nominal length of the
transducers corresponds to the predetermined spacing.
8. A tactile interface device as claimed in claim 7, wherein the predetermined spacing is
about 10mm and thereby the nominal length of the transducers is about 10mm.
9. A tactile interface device as claimed in claim 1. wherein the second major component
comprising plurality of stretching elements comprises stretch sensors bridging the tips
of the transducers such that it conforms to the body surface contour in between the
transducers without exerting significant force onto the body.
10. A tactile interface device as claimed in claim 9, wherein the stretch sensors are adapted
to sense length proportional output thereby providing information of combination of
selective geometry such as nodule curvature and selective dynamometry such as
elasticity about the body tissue.
11. A tactile interface device for nodule palpation in a perception enhanced form
substantially as herein described and illustrated with reference to the accompanying
A tactile interface device for nodule palpation in a perception enhanced form comprises a
deformable force stretch array sensor comprising plurality of components comprising
plurality of first major components (la , 5) and plurality of second major components (10).
The first major components have predetermined rigidity; and said second major components
are operatively interconnected with each of the first major components. The device comprises
actuator means for indwelling nodule simulation, being operatively connected with said
deformable force stretch array sensor, and adapted to provide perception of the nodule in the
829-kol-2004-granted-reply to examination report.pdf
|Indian Patent Application Number||829/KOL/2004|
|PG Journal Number||17/2009|
|Date of Filing||17-Dec-2004|
|Name of Patentee||INDIAN INSTITUTE OF TECHNOLOGY|
|PCT International Classification Number||64 B|
|PCT International Application Number||N/A|
|PCT International Filing date|