Key-words:
Neuroendovascular intervention - remote surgery - robotics - sensor feedback
Introduction
With coronavirus disease (COVID-19) infections becoming a global problem, the risk
of infection by patients to the medical staff, especially surgeons, is exceptionally
high; some deaths have even been reported. Under these circumstances, a surgical support
robot that reproduces the procedure in real time without touching the patient is currently
the most sought-after device, as an alternative to ensure medical professionals' safety.
An endovascular procedure is performed with fluoroscopy and even if a radiation protector
is attached, exposure is unavoidable. Robots are the only solutions to this risk.[[1]],[[2]]
In the cardiovascular field, a simple device for coronary catheterization has already
been put into practical use by the Corindus robot system (CorPath GRX™).[[3]],[[4]],[[5]] Although it has been introduced in Japan and used clinically,[[6]] this device is limited to wired control from a neighboring separate room because
it does not have a wireless operation function. Last year, this system was reportedly
applied to neuroendovascular treatment in humans;[[7]],[[8]],[[9]] however, it has not been in the practical stage yet.
We completed a prototype of an endovascular operation support robot, with a sensing
function developed over 10 years,[[10]] and conducted the world's first wireless remote catheter surgery. After presenting
the results, we describe the issues and suggest countermeasures for practical use.
Materials
The robot has the same specifications as the models we have announced thus far,[[10]] and can operate the catheter and the guidewire separately and simultaneously. It
is combined with the insertion force-measuring device that we have been working on
for many years[[11]],[[12]] [[Figure 1]]. We also succeeded in miniaturizing the robot to some extent, allowing it to be
easily installed and moved on the angiography room's operating table. Specifically,
with the catheter attachment/detachment part, we can attach/detach the Y-connector
with a single touch, using an eccentric cam.
Figure 1: Slave robot system with a catheter and a wire robot and an insertion force sensor
For insertion force detection, the insertion force that is applied to the wire passes
through the curved through-hole of the sensor head in the wire drive robot and is
measured by the sensor load cell. This is converted into the wire insertion force
using a result measured in advance by the calibration load cell. In the previous design,
this was a complicated structure incorporated into the drive unit inside the rotating
body; however, it has been improved to make it easier to attach and detach, as a sensor
that can be separated from the wire drive unit [[Figure 2]].
Figure 2: Inner structure of the insertion force sensor
Methods
We rented a company's experimental angiography room and conducted a remote control
experiment using a blood vessel model from a remote environment in a separate room
(a distance of approximately 50 m) [[Figure 3]]. The slave robot on the operating side was an original machine that enabled sensing
feedback using our originally developed insertion force-measuring device.[[2]] The master side used joysticks. The operation unit transfers the two joysticks'
tilt data to the robot, and the robot drives the catheter and wire according to the
tilt data.
Figure 3: The scheme of remote control and transmission system
When the robot transfers the sensor data of the mounted wire insertion force to the
operation unit, the operation unit informs the operator of the insertion force by
varying the pitch of a sound emitted from the control device connected to the controller.[[1]] Thus, the operator in the separate room can grasp the degree of pressure stress
applied to the blood vessel wall in real time.
The slave robot was placed at the foot of the blood vessel model on the procedure
table of the angiography room. The master side was set in a separate room, at least
50 m away, and they were connected by HTTP communication using a local area network.
The surgeon operated by looking at a personal computer (PC) monitor that shared a
screen with the monitor of the angiography equipment (Alphenix™: Cannon Medical System)
in the angiography room. In the angiography room, the slave robot catheterized and
inserted the coil into the aneurysm in the silicon blood vessel model [[Figure 4]].
Figure 4: The whole view of the slave robot (a) and the monitor of angiography room (b), The
operation of coiling in the master side (c) was exactly corresponding with the slave
side (d)
Results
Verification of operating environment
Delay time analysis
The robot required a time gradient to reach a stable advanced speed at the time of
initial movement, and experienced a slight time lag when braking to a complete stop,
when the surgeon stopped advancing. On measuring the robot operation's delay time,
we found delays in both the catheter and the coil. On the catheter side, the motor
experienced a 0.1-s delay, before stopping from the maximum speed. The wire side experienced
delays in the wireless transmission of the control signal, by Bluetooth, to the motor
in the rotating body and the motor section, resulting in a total delay of approximately
0.1 s. There was no delay due to the return of the joystick. On the other hand, because
the video was captured by a PC and then sent and received via network transfer, the
delay due to this image transmission mechanism was approximately 0.1 s. Moreover,
the delay of the network itself was approximately 0.1 s or less.
Remote operation feasibility
Compared to the conventional wired experiment, the delay was significantly improved,
as described above, and it responded to the joystick's swift movement with some accuracy.
In addition, the surgeon could control the stress on the blood vessels during the
operation, for example, by stopping the operation and reinserting the device, by listening
to the pitch indicating the insertion force, which was picked up by the microphone
in the angiography room in real time.
Discussion
Significance of this robot
Endovascular treatment robots make simple two-dimensional movements, for example,
pushing, pulling, and twisting devices such as catheters, as opposed to complicated
three-dimensional conventional surgeries. The range of movement is small and stable.
Therefore the road to robotization is very close. Currently, remote surgery is sought
after in various fields to ensure the safety of medical staff in the surgical treatment
of COVID-19-positive patients, and to avoid direct contact with the patients as much
as possible. As the da Vinci surgical system is used widely in abdominal surgery,
it is necessary to develop similar devices in the cerebrovascular field.
In a cerebral embolism, in which a large thrombus clogs the main trunk of cerebral
artery, the brain will suffer an irreversible cerebral infarction if the treatment
is delayed, so a maximally rapid recanalization is required. Acute mechanical thrombectomy
treatment has achieved excellent results in this case, so the spread of this method
has been recognized as essential. In this meaning, a remote emergency surgery by a
specialist using the remote surgery system can be beneficial; for example, when transporting
patients in need of thrombectomy to a far stroke center with neuroendovascular physicians,
or in remote hospitals where it takes time for the arrival of the specialists. There
is a report of the feasibility of long-distance tele-robotic-intervention in coronary
intervention,[[12]] but it may be still a preliminary trial.
Although endovascular treatment is a minimally invasive treatment, the surgeon's and
the staff's cumulative radiation exposure is problematic; thus, if it becomes possible
to operate in a separate room without exposure, it can also contribute to the medical
staff's safety and health.
Items to be improved for practical use
Although the insertion and procedure do not leave a permanent indwelling device in
the human body, it is necessary to ensure operational certainty, as in automatic driving.
The above-mentioned Corindus robot system (GRX) has already been introduced in Japan,
and clinically used in the cardiovascular field.[[6]] We must compare and verify our device with this; however, we suppose that having
a sensing function is more practical in terms of safety. Previous reports did not
address the importance of tactile feedback, because the friction is noted visually
by watching for subtle changes in the shape and motion of devices as a compensation
for the sensory profile.[[7]] However, we may not avoid the penetration of the vessel or aneurysm because it
is too late to stop the robot handling to advance, if we make the decision only by
watching the visual information. That is why we are particular about the equipment
of sensory motor feedback system.
The following improvements and countermeasures are necessary for the practical clinical
use of our system.
Unified, integrated system design
Because these devices are now entirely separate, it is necessary to create a more
compact and elaborate integrated drive and sensing system, for practical use in future.
Therefore, comprehensive development by multiple industries, including hardware design,
is required.
High-performance transmission control system
The system currently requires a time gradient to reach a stable advanced speed at
the time of initial movement, and experiences a slight time lag when braking to a
complete stop when the surgeon stops advancing. In addition, a high-speed wide area
network line and motor improvement are required. In addition, it is essential to prepare
for robot malfunctions or unforeseen complications by adding safety functions, for
example, emergency stop devices and manual intervention methods. Moreover, we should
consider how to rescue patients in these cases.
As a solution to the delay in image transmission, we should improve the current transmission
system: fluoroscope → network transmission → PC network reception → PC display. By
devising a transfer method that avoids the PC, we can expect to shorten the delay
by 0.05–0.08 s. We believe that the mechanical section's delay can be shortened to
0.02 s by improving the motor's performance and changing to infrared communication,
instead of Bluetooth. In addition, a network environment considerably influences the
transmission speed when congested; hence, it is necessary to strengthen the network
as a countermeasure against delays.
As a technical measure, we should set in advance a maximum limit between the master
and the slave, and take measures, for example, pausing the robot or issuing a warning,
when the time lag becomes large.
Confirmation of the safety and operational impact of sterilization
This is related to the equipment design. The device should have a compact design that
is waterproof and sealed. It must also use parts made of materials that do not affect
the human body, and have a structure that withstands the sterilization process. We
will also develop a disposable device insertion kit for each patient, which is attachable
and detachable from the drive unit.
Ethical issues
It is necessary to clarify the ethical issues regarding responsibility, in the event
of complications during the procedure.
Conclusion
In future, when we complete our system, we can apply it to endovascular treatments
other than the brain, and to endoscopic surgery robots equipped with sensing functions.
In the world's first remote experiment using an endovascular treatment robot equipped
with our sensing function, the performance appeared to be sufficiently feasible to
perform the surgery safely. It seems to be clinically applicable in future, if we
make further improvements for long-distance experiments, safety, accuracy, sterilization,
etc., This system seems extremely promising for preventing COVID-19 infection and
radiation exposure to medical staff and increasing safety. It will also enable medical
professionals to operate in remote areas and create a ubiquitous medical environment.
The robotic system was successful at navigating and deploying small-gauge devices
specific to neurovascular procedures. Given the potential benefits of robotic-assisted
surgery for the patient and the surgeon, further investigation is warranted for this
indication.
