A Virtual Environment for Breast Exams Practice
with Haptics and Gamification
André Luiz Brazil
Aura Conci
Computing Institute
Universidade Federal Fluminense
Niteroi - RJ, Brazil
[email protected]
Computing Institute
Universidade Federal Fluminense
Niteroi - RJ, Brazil
[email protected]
Esteban Clua
Leonardo Kayat Bittencourt
Computing Institute
Universidade Federal Fluminense
Niteroi - RJ, Brazil
[email protected]
Antonio Pedro Hospital - Radiology Department
Universidade Federal Fluminense
Rio de Janeiro - RJ, Brazil
[email protected]
Lúcia Blondet Baruque
Digital Media Dep.
Fundação CECIERJ
Rio de Janeiro - RJ, Brazil
[email protected]
Abstract - Breast cancer is the second most frequent cancer in
the world, with 250 thousands of deaths each year. Early detection
of tumors by breast exams and procedures can help to reduce these
numbers. More medical practice is required. Professional training
for medical procedures in real environments is costly and risky both
for the student and the patient. A way to reduce costs and risks of
training is by the use of a virtual simulator. An environment closer
to the real world in medical simulations can provide a better quality
experience of to the trainee. The use of haptic devices can emulate
tactile sensations and feedback forces that correspond to body
structures and density of tissues. The used device has six degrees of
freedom (DOF): movement on three axes (x, y, and z), rotations,
and horizontal and vertical inclinations. This work presents a
virtual environment for breast exams practice and sentinel nodes
detection procedures that employ the use of a haptic device and a
gamified interface for feedbacks. The objective is to improve early
breast cancer diagnosis chances. A model for tissue deformation
calculations on tridimensional patient body mesh is proposed, to
add visual realism to the interactions in the virtual environment.
Needle depth and its tridimensional position data are updated at
real-time on needle insertion. Tumor nodes size and position are
dynamically generated upon each simulation, increasing training
possibilities for the student. The gamification strategy improves the
practice on environment, with elements to engage the player on
activity. User progress is tracked by subdivision of breast exams and
procedures into smaller challenges, for better performance
evaluation on the virtual environment. A gamified interface, with
player score and achievements mapping is included. These
gamification features have not been employed on breast simulators
from previously investigated works.
Keywords: Breast Palpation, Medical Procedure, Needle Insertion,
Gamification, Training, Sentinel Node Detection.
I. INTRODUCTION
Cancer National Institute data (INCA) indicates breast
cancer as the second most frequent cancer in the world [1].
This is the most common cancer among brazilian women,
corresponding to 25% of cancer occurrences. World Health
Organization (OMS) estimates 520 thousands of deaths for
year due to breast cancer [2]. Groups with increased risks are
at ages beyond 45. New cases on young people are increasing
at each year.
The early cancer diagnosis by breast exams helps to avoid
its progression and improves the chances for its cure. Medical
expertise in the procedures can contribute to reduce these
numbers.
Options available for medical training improvement
include visualization of 2D drawings, specialized videos or 3D
animations, practice with phantoms and virtual simulators.
This last option has been most accepted by students in medical
field of experience [3].
Use of virtual simulators for practicing is a reality in many
society sectors nowadays. They offer options for the trainee to
interact and experience situations before facing contact with
the real environment. They intend to speed up training and
improve skill and risk security of procedures.
Medical computational simulators can constitute in an
interesting alternative to the use of phantoms [4] for practice.
Phantoms are physical mannequins with replaceable parts.
They usually have a high cost associated to their use. Haptic
device use in computational simulations offer a lower cost
option when compared to others.
Haptic devices are capable to reproduce physical tactile
sensations in response to movements. Their use is employed in
many application areas, including tridimensional modeling
and medical procedures. The most popular and low cost haptic
devices are the Phantom Omni and the Novint Falcon.
User motivation and interest for practicing on virtual
simulators can be improved by inclusion of game elements
[5]. Gamification can help to direct and intensify the player
efforts in a virtual simulator. A gameplay experience linked to
the medical practices, with defined objectives to be fulfilled, is
the target. Immediate feedback and virtual rewards, as points
and statuses are important to achieve this.
The idea is to combine and integrate the use of a low cost
haptic device and game elements into a virtual environment
for medical breast exams practice. Two types of feedback are
available to the user: physical and motivational. Reactions
similar to the real experience on procedures are programmed
to be sensed through the apprentices hands, by haptic
feedback. Visual interface and gamification provide real-time
significant information to the player.
The extended use of virtual simulators to achieve the
desired expertise in medical procedures also can be improved,
in terms of motivation, interest and user experience by
incorporating game elements into the simulators. This
approach turns the virtual simulator into a serious game
experience. This may improve and shorten the learning curve
of the trainee, and also reduce the time needed to acquire the
required skill on the procedure, by giving her a more joyful
learning experience.
The work is subdivided in the following sections: section
2 shows comments about related works; section 3, which
explains details about the proposal; section 4 presents results
and discussions, with the development and use of simulation
prototypes; section 5 presents conclusions and future works
and finally, the references.
II. RELATED WORKS
Related works include a small description of breast
palpation exams and sentinel node detection, both included in
the virtual simulator proposed. Breast and needle insertion
simulators, and gamification related work is also reported.
A. Breast palpation exam
The breast palpation diagnosis is not only tactile. Ask the
patient for looking at breasts in the mirror with arms on hips
for size, shape, color or nipple orientation changes, distortions,
skin bulging or fluid coming out is important.
Hand touch on the breasts use few finger pads flat and
together. It is important to look for hard nodules, consistence
changes, secretions or protuberances [6]. With a circular
motion, is necessary to cover the entire breast from top to
bottom and side to side. It is important to feel all the tissue
from the front to the back of your breasts, including the
ribcage. Figure 1 indicates these moves.
Figure 1. Breast palpation exam
B. Sentinel node detection
In the sentinel node detection, the physician injects a
radioactive dye liquid into the breast area. The dye travels and
its concentration is observed afterwards, by a special breast
scan [7]. Figure 2 illustrates this process in three steps.
The dye movement indicates the pathway of lymph. The
dye is drained in the direction of a lymph node from the part
of the breast that is "housing" the tumor. It shows the lymph
node that is the "sentinel node" for the tumor. Afterwards, the
sentinel node and closest nodes can be located and removed
by a surgeon and sent to a pathology lab for analysis. Figure 2
shows steps for sentinel node detection by dye application.
Figure 2. Sentinel node detection by dye injection. Left: Dye injection.
Middle: Dye drains towards nodes. Right: Dye concentrates in sentinel node
C. Simulators
A literature review on breast self-examination training is
reported by [8], where training in breast self-examination
improves compliance, confidence, and proficiency. Authors
emphasize that practice on breast models should be included
in breast self-examination training.
Tactile simulators for breast palpation exams are available.
A single synthetic breast in a box includes pre-defined nodes
inside, for tumor and cancer sensations [9] (figure 3 left).
Another simulator offers a single breast in a “pad”, linked to a
computer, and provide physical sensations to touch [10]. Both
are limited on their setup options. This last one is limited to 4
diagnosis setups (replaceable breast pads) with fixed tumor
locations, and few computational feedback (figure 3 middle).
A virtual simulator with haptic feedback, developed with
Vizard software, was reported by [11]. It provides one
tridimensional breast with a node and a hand for detection, but
few visual and computational feedback (Figure 3 right).
achieving more realism on a simulation of needle insertion
procedures. Tissue thickness data is available on table 1.
Figure 3. Breast exam simulators. Left: a tactile simulator [9]. Middle: A
computer assisted breast "pad" simulator [10]. Right: A virtual breast
simulator with haptic feedback [11].
Needle insertion studies are also relevant, for dye fluid
application in sentinel node detection procedure. Needle
insertion is a less invasive procedure, necessary for a broad
range of traditional medical treatments, including injections,
punctures and percutaneous treatments [12]. The authors
consider the effectiveness of treatment as strongly dependent
from needle tip position, whose accuracy improves according
to the skill and expertise from professionals.
Forces for needle insertion were mapped by experiments in
porcine cadavers and human subjects [13,14]. A list of the
bypassed tissues is provided, with their thickness and average
necessary insertion forces (in Newtons) to be applied to
puncture the tissue and move a needle inside them. The values
can be visualized in table 1.
Table 1. Tissue layers on needle insertion: Insertion forces, thickness and
depth approximation based on porcine and human trials
Tissue Layer
Skin
Subcutaneous Fat
Supraspinous
ligament
Interspinous
ligament
Ligamentum
flavum
Epidural space
Dura
Tissue Thickness
(mm)
3
6
4
Needle
Depth (mm)
0
3
9
Insertion
Force (N)
12.9
6
9
26
13
8
3
39
11.1
6
15
42
48
0
2.0
The failure rate of needle insertion procedures can be
reduced by the use of virtual 3D simulators [2]. A failure rate
study on needle insertion procedures on soft tissues (skin, fat
and muscle) was conducted by [15]. They employed several
experiments using a 1 DOF haptic device for tasks on a 2D
virtual simulator by medical field trainees and experts. The
work reported an improvement rate of 87% on procedure
accuracy (ex. fewer errors) for tests in which the simulator
offered a visual interface with real-time feedback and a 52%
improvement rate for experiments using some haptic device
force feedback. The work was not specifically directed at
epidural procedures and used simple force calculation with 2D
dynamic images for feedback.
Another relevant aspect to be considered when developing
a virtual simulator for needle insertion is the thickness of each
tissue in the virtual patient body to be bypassed during the
needle insertion procedure. This is a relevant factor for
D. Gamification
The gamification aims to make use of elements and
mechanics available in games to transform real tasks into
attractive and ludic ones, in order to improve the people´s
motivation and engagement to execute these tasks [16].
Studies have shown these ones as configurable mechanisms
capable to stimulate individuals toward objectives and ideals.
Corporative, academic and scientific society fields are
adopting gamification practices in their environments.
Most common elements from a game that can be used in
other contexts are the points, badges and leaderboards. They
compose a basic gamification called PBL [17]. These elements
must be significant and meaningful to the apprentices, in order
to mobilize them [18].
Medical simulations employing gamification achieved a
significant boost from 2.7 to 83.9 average practice hours with
USA urology residents. They trained on a simulator for
minimally invasive surgeries, with precision exercises used to
improve and maintain their skill level [19]. The experiment
involved practicing minimally invasive surgeries procedures
and ring-walk exercises on a simulator, with the use of points,
a leaderboard and rewards as gamification strategies.
Serious games also use game elements, targeted for
learning and practice. On medical field, they include themes as
x-ray, computer tomography (CT), magnetic resonance
imaging (MRI), pathology and cardiology, available at [20].
III. THE PROPOSAL
The proposal objectives the development of a virtual
environment for breast exams and diagnosis practice. It
includes the integration with a haptic device for force
feedback, use of gamification elements and a visual interface.
Virtual environments help to support medical skill
development practice. Haptic integration improves the
outcome of simulation by physical sensations. Dynamic tissue
deformation enhances the visual aspect of simulation. The use
of gamification elements auxiliate on turning the simulation
into a playful experience. Figure 4 illustrates the features.
The proposal includes palpation of patient breasts,
feedback forces corresponding to tactile sensations and tumors
presence, syringe movement around virtual environment,
needle insertion on skin tissue and dye application for sentinel
node detection.
Figure 4. Virtual environment and its main features
A. Haptic Device Integration
Haptic devices are capable of producing physical forces
resisting to the hands movement operating them. The use of
haptic devices together with a virtual simulator environment
can provide a better sense of reality into the anesthesia
procedure, which helps to bridge the gap between the real
world situations and the practices executed on the virtual
simulator. This helps to improve students experience and
confidence, due to exposure for facing the simulated reality.
The proposal is to use the Phantom Omni as the feedback
device (figure 6 left). Its arm is capable of six degrees of
freedom (6 DOF), for tri-axial movement with arm rotation
and inclinations. Force feedback is configured by the use of
OpenHaptics API [21]. It contains a set of device commands
that can be integrated to the engine prototypes, for reading and
adjusting haptic data.
The forces applied on haptic device are read, mapped and
converted to a Vector3 structure, available in engine. It is
composed of 3 floating-point variables, to store the force
components, in directions x, y and z. A script reads and
converts these values from haptic device to float data type.
Configuration of resistance forces for skin tissue is based on
data reported on table 1.
It is also possible to set a maximum depth value, as a limit
for needle perforation by the haptic device. A
GetPunctureRatio function, implemented by script, divides the
current needle depth by the maximum needle depth and
returns the result as a value between from 0 and 1.
This proposition is extendable for displacement calculation
on other axis. Considering both the contact point and needle
tip as tridimensional positions, it is possible to measure needle
displacement in x and y axis. Displacements (Δ) can be
calculated as the difference between these positions, only
taking the respective axial information into account.
C. Dynamic Tissue Deformation
A displacement effect will be calculated upon the nodes
(vertices) from the patient body tridimensional mesh, used as
the base structure for nodal displacement operations. The body
mesh can be visualized on figure 6 (right), composed by
triangles and vertices.
The haptic device movement is tracked by scripts that use
API functions and constantly read the device current
coordinates. They are converted to a Vector3 structure, used to
update the 3D syringe position in the virtual environment.
The haptic interactions with 3D patient body require the
mesh information being sent to the haptic device memory. A
script uses API communication resources to update mesh data
for all intractable objects, so the user is able to "feel" them.
B. Syringe Penetration
The needle depth calculation starts soon after the virtual
needle collides with the patient body (skin) on the virtual
environment. The location of this collision is referenced as the
puncture point position. The difference between needle current
position and this puncture point position is the needle depth.
Needle displacement (depth) in z axis (Δz) is to be
measured as the distance from the initial contact point between
a virtual skin surface and the needle (Zcontact), and the current
needle tip position (Ztip), as depicted on figure 5.
Figure 5. Syringe needle displacement calculation, based on distance from
skin contact point to current needle tip position
Figure 6. Left: Phantom Omni (left) haptic. Right: Tridimensional body mesh,
with triangles and vertices
The deformation results can be achieved by considering a
proximal zone, composed by a group of nodes (vertices) near
to the region pressed by the needle tip. These nodes are
vertices from the tissue 3D mesh to be affected by a
displacement effect. The displacement of these nodes is
proportional to: the current depth (z axis location) of the
needle tip and the vertex distance from needle tip. Simplified
idea is shown on figure 7, considering only vertex distance
from y axis. Other proximal vertices should be displaced.
The displacement effect has a magnitude (Md) that can be
calculated by the expression: Md = Ztip / (Ntd 2 + 1).
The parameter Ztip references the needle tip depth. Ntd is
the distance from a node to the needle tip contact point with
the tissue. Md is the resultant magnitude of the displacement
effect to be applied on the node. The magnitude of
displacement effect on a node is lower when the distance
between the node and contact point (Ntd) increases. If a node
location is very distant from the contact point, the influence
upon it will be so low that it can just be ignored. Only a
proximal area on tissue mesh around the contact point of the
needle tip will be significantly influenced by the displacement
effect. The graphical representation of this function generates
a curve similar to the shape of a "bell" statistic curve from
normal distribution, displayed on figure 7, at right. Note that
the displacement effect will always be relative to the needle
movement direction along the three axis (x, y and z). In figure
7, the needle movement was represented only on the z (depth)
axis, to exemplify the displacement effects calculations
relative to this axis. The displacement should also be
calculated for the movement on other axis (x and y), when it is
the case.
exams to be executed into subtasks. These tasks are to be
concluded by the player, linked to a points reward. Table 2
shows a list with the proposed tasks with their points.
Table 2. Gamification proposed tasks and their associated score
Exam
Breast
Diagnosis
Figure 7. Displacement of nodes in a mesh based on needle tip position on z
axis (needle depth)
The farther the node is located from the contact point,
lesser will be the displacement effect magnitude (Md) upon the
node, so a node distant from the contact point will only be
affected by a smaller displacement from its original position,
or not affected at all, depending on the displacement factor
resulting from the function.
Tissue deformation calculations can be exemplified by
data displayed on figure 7. Assuming the displacement occurs
only along the y axis, the numbers 1 to 5 represent the nodes
interlinking the surface segments. On picture A, no contact
and no deformation occurs. On picture B, nodes 1 and 5
suffered a displacement of 0.1, nodes 2 and 4 were displaced
by 0.2 and node 3 (the contact point), by 1.0. It assumes the yaxis as the distance between the nodes and needle tip (Ntd).
Distance values are -2 and 2 for nodes 2 and 4 related to node
3 (tip). The nodal displacement magnitude (Md) can be
accounted as Md = Ztip / (Nad2 + 1) = 1 / 22+1 = 1/5 = 0.2, for
nodes 2 and 4.
There is also a proposal to affect the amount of
displacement of the nodes by tissue stiffness property value
(St). This is a constant value, which ranges from 0 to 1
(maximum stiffness), based on each tissue layer
characteristics. The magnitude of displacement on each tissue
node (Md) would then be inversely proportionally affected by
the tissue stiffness property value (St), so final node
displacement effect (Nd) becomes the calculated magnitude
divided by tissue stiffness, resulting in: Nd = Md / St.
Other two important configurable parameters to be
considered as influences for this proposal are the needle's type
and its diameter. Thicker and pointed needles usually present a
different area of effect, that can be determined according to
these parameters.
The simulation of a visual tissue puncture effect is
achievable by use of interactive cloth component, from Unity
engine. It enables real time body mesh geometry change,
based on adjustable parameter values.
D. Gamification
The gamification proposal is tied to the use of score and
achievements. It intends to subdivide the main diagnosis
Proposed Subtask/Challenge
Breast contact
Achievement
Points
50
Breast nodes identification
100
Breast tumor identification
350
Sentinel
Syringe contact
50
Node Exam
Dye application
250
The use of this strategy facilitates the tracking of player
advancement inside the virtual environment. Another
objective is to improve the user engagement for practice.
Tracking of player score, progress and concluded
challenges is done by a game manager script. It structures and
stores the current user points and status of all tasks available.
E. Tumor nodes generation
The inclusion of virtual tumor nodes inside the breasts is
another relevant feature available on breast exams detection.
The node amount, their size (small, medium, big) and their
placement (location) are generated by script. Haptic touch
sensations are provided to identify them by breast palpation.
They can also be identified by the dye application with a
syringe, on sentinel node detection procedure. This feature is
linked to the breast tumor identification task, listed on table 2.
IV. RESULTS AND FEEDBACK
Achieved results include a virtual simulator environment
with features for practice on breast cancer diagnosis exams.
Nodes detection with haptic feedback and dye application with
a syringe for the sentinel node detection are implemented.
Realism is added on the simulation with tissue deformation
feature.
Results show more visual details and feedback information
available than investigated simulators [9-11] is presented. This
work includes dye application for sentinel node detection
practices, not reported on other breast simulators before.
The Unity3D engine was chosen for the development of
prototypes of a virtual simulator to enable breast diagnosis
exams practice and incorporate together haptic feedback with
gamification elements. The engine have a visual interface to
facilitate 3D models import and placement on simulation
scenes. A dedicated developers online community, and scripts
on C#, JavaScript and Python languages are other advantages.
A. The Visual interface
The visual interface is created by combination of
components from Unity 5 engine. The canvas is used to place
2D elements and feedback on a 3D environment, a graphic bar
tracks the needle depth and text fields and images are used to
display information and achievement conclusion messages.
Figure 8 shows the use of these interface elements at right.
The woman 3D model used on simulation was produced
with FUSE TM software. A free syringe 3D model was also
included, available from http://archive3d.net/?a=download&
id=6bad032e.
environment, which awarded the player with 50 points for
needle contact and 250 points for dye application. After dye
application, a purple sphere appears, indicating the location of
a sentinel node. Interface shows current player score, needle
depth and syringe axial location. Figures 8 and 10 show the
gamified interface with tasks feedback upon their conclusion.
Figure 10. Virtual environment with gamified interface and visual feedback
for dye injection achievement conclusion and sentinel node detection
Figure 8. Virtual environment with gamified interface and feedback for
syringe contact achievement conclusion
B. Dynamic Tissue Deformation
The interactive cloth engine component (available from
Unity version 4) was used to simulate the implementation of
flexible external skin tissue and patient body deformation.
Among configurable parameters are: bending and stretching
stiffness, thickness, friction, density pressure and collision
response (figure 9 left). They enabled real time visual results
with tissue interactions by the haptic device. Figure 9 (right)
shows body tissue deformation after having its mesh “pressed”
by contact with the object. The other observed breast exam
simulators did not present this feature available.
Tumor nodes can be detected by haptic sensations on
breast palpation exams or by dye application with a syringe. A
sentinel node detected by dye application can be visualized on
figure 10.
The gamification elements use have shown that the
subdivision of exams and procedure into smaller tasks can
achieve better results both in student performance tracking as
well as engagement for tasks execution. A sample of what can
be done in terms of motivation for the trainee to improve the
learning and practice.
V. CONCLUSIONS
This work presented a virtual simulator supported by a
visual interface with haptic feedback and gamification
features. The work includes haptic forces that are applied upon
breast contact and needle insertion for dye application,
significant for breast exams and sentinel node detection.
The current prototype shows that it is possible and viable
to implement breast palpation exams feedback and needle
insertions for sentinel node detection by using the engine
Unity3D with the Phantom Omni haptic device.
Tissue deformations emulate breast response to the touch
and adds visual realism to the simulator. Haptic forces
improve this feedback. Inclusion of sensations of virtual tumor
nodes, randomly placed inside the breasts at each simulation
run, for breast exams detection tasks, add new challenges to
the student on every play attempt.
Needle position and depth are mapped in the simulator.
Tracking occur in three axis (x, y, z) and haptic feedback
forces are applied, improving simulation realism.
Figure 9. Unity3D Interactive Cloth resource parameters (left) and female 3D
body and skin tissue deformation after haptic force interaction
C. Dye application and Gamification Results
Results are concentrated on two tasks: skin penetration by
syringe needle and a subsequent dye application. Both were
configured as achievements inside the simulation
The investigated gamification works have shown that their
use can be an interesting resource to keep the medical students
practicing for a longer time. Skill and proficiency are
necessary before interaction with real patients.
Gamification of environment subdivides breast exams into
smaller and easier achievable challenges. The tasks are tied to
score awards and a visual conclusion feedback. It motivates
the players into practicing for improvement and a perfection of
execution. This strategy results in better learning curves and
continuous tracking of the student progress. Experiences about
the use of a gamified environment for breast exams and
sentinel node detection practices were not found.
Further works include simulation of dye fluid to better
visually indicate sentinel node location. Tests with the virtual
environment subdividing the medical team in two groups
(with and without gamification) are also planned. This will
help to map the effectivity of gamification use for each
implemented feature. Implementation of minimal invasive
surgery for nodes and tumor removal into the simulation is
also desired.
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