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Journal of Medical Engineering & Technology
URL: http://mc.manuscriptcentral.com/tmet Email: John.Woodcock@CardiffandVale.wales.nhs.uk
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Structure and Motion Design of a Mock Circulatory Test Rig
Yuhui Shi *, Theodosios Korakianitis $, Zhongjian Li &, and Yubing Shi
#
* Northwest Institute of Mechanical and Electrical Engineering, Shaanxi Province,
China
USA
For Peer Review Only
$ Parks College of Engineering, Aviation and Technology, Saint Louis University,
& College of Automation, Northwestern Polytechnical University, China
# Faculty of Arts, Science and Technology, University of Northampton, Northampton,
Corresponding author:
Faculty of Arts, Science and Technology, University of Northampton,
University Drive, Northampton, NN1 5PH, UK
Email: yubing.shi@northampton.ac.uk
The total number of words in the main text: 4541
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UK
Yubing
Shi
The number of words in the abstract: 158
The number of figures: 7
The number of tables: 2
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Structure and Motion Design of a Mock Circulatory Test Rig
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9 Abstract
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12 Mock circulatory test rig (MCTR) is the essential and indispensable facility
in
13 the cardiovascular in vitro studies. The system configuration and the motion
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15 profile of the MCTR design directly influence the validity, precision, and
16 accuracy of the experimental data collected. Previous studies gave the 17
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For Peer Review Only
18 schematic but never describes the structure and motion design details of the
19 MCTRs used, which makes comparison of the experimental data reported by
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21 different research groups plausible but not fully convincing. This paper
22 presents the detailed structure and motion design of a sophisticated MCTR
23
24 system, and examines the important issues such as the determination of the
25 ventricular motion waveform, modelling of the physiological impedance, etc. 26
27 in the MCTR designing. The study demonstrates the overall design
procedures
28 from the system conception, cardiac model devising, motion planning, to the 29
30 motor and accessories selection. This can be used as a reference to aid
31 researchers in the design and construction of their own in-house MCTRs for 32
33 cardiovascular studies.
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35 Keywords: mock circulatory test rig; cardiovascular dynamics; in vitro test, 36
37 structure design; motion design
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39
40 Introduction
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42 Clinical investigations play an important role in the cardiovascular physiology 43
44 research. However, due to various limitations (e.g., the complex geometries of the
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47 cardiovascular organs, the difficulty in isolating the influence from each of the
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49 individual physiological factors, and the size of the sensors etc.), not all physiological
50 and pathological phenomena can be observed directly with clinical studies on the human
body (1). Thus it is necessary to construct artificial systems to simulate the functioning of the
human circulatory system, so that in vitro experiments can be
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carried out on the artificial systems instead. Such an artificial system is often
implemented as a mechanical-electrical-hydraulic assembly and is tuned to produce
different blood flow conditions corresponding to the healthy and diseased status in
the human body (2). The mechanical-electrical-hydraulic system is usually called a
mock circulatory test rig (MCTR). Past designs of MCTRs simulate steady or
pulsatile flow, depending on the goals of the experiments. Using these MCTRs,
researchers gained more insight into not only the blood flow physics (i.e., changes
of overall flow field structure as well as the variations of velocity, pressure, shear
stresses, and the different forces acting on the native organs) (2–12), but also
detailed information for the design and performance analysis of prosthetic devices
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57 58 59 60 URL: http://mc.manuscriptcentral.com/tmet Email: John.Woodcock@CardiffandVale.wales.nhs.uk5
such as
artificial
heart
valves,
stents, and
ventricular
assist
devices
(1,2,12–
38). The
MCTR
has
become a
fundament
al and indispensable facility in the in vitro study of the cardiovascular physiology.
The system configuration and the motion profile of the MCTR design determine to
what degree the simulated cardiac flow mimics the physiological reality, and thus
directly influence the validity, precision, and accuracy of the experimental data
collected in the in vitro studies (1,2).
Given the importance of the MCTR design, it is surprising that no structure and
motion design details of the MCTRs have ever been reported in the open literature
so far, and those published cardiovascular in vitro studies usually described only the
schematic of the MCTR followed by a brief list of the components used in the
system. Lacking of such technical details, comparing the experimental data reported
by different research groups becomes plausible but not fully convincing. Besides,
researchers who plan to build their in-house MCTRs but have less design experience
would find themselves helpless after a fruitless literature survey. To fill the gap, this
paper presents the detailed structure and motion design of a sophisticated MCTR
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system, which can be used as a reference by cardiovascular researchers in their
planning to build in-house MCTRs. Also it is hoped that this paper would initiate
further in-depth discussions among researchers about the improvement of the MCTR
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9 designs, which as a result contributes to the continuous advances and refinement of
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12 the MCTR technology to support the ever-increasing requirements about the
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14 reliability and the accuracy in the cardiovascular in vitro studies.
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17 System Design
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20 The aim of the current MCTR design is to provide an embodiment of a fundamental
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22 electric-mechanical platform that simulates the hydro-dynamic characteristics of the 23
24 human circulatory system, to facilitate the in vitro measurement of blood flow
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26 features and testing of response dynamics in cardiovascular prosthetic organs.
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28 Besides, the MCTR design should be able to simulate the circulatory response in a
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31 range of healthy and diseased conditions: from the healthy rest condition to the
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33 exercise condition, and even the heart failure condition. For such purposes, the
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35 operating parameters for the MCTR are first chosen as shown in Table 1, by referring 36
37 to the ranges of the physiological variables reported in the literature (39–41).
38
39 (Table 1 comes here)
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43 2.1 System configuration
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45 The MCTR design comprises two circulation loops: the systemic loop and the
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48 pulmonary loop. In each loop, two throttle valves and a compliance unit are used to
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50 simulate the corresponding physiological impedance, and a tank separated from the
rest of the system by a one-way check valve is used to provide the correct mass of
fluid in circulation (adjusted during system commissioning). Three pressure
transducers and two flow transducers are installed in each loop, to measure the
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pressure in the atrium, the ventricle and the main artery, and the flow rates in the
artery and the vein. Fig. 1 shows the system configuration of the MCTR design.
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(Fi
gur
e 1
co
me
s
her
e)
2.2
Structure
Design of
the heart
model
(Fi
gur
e 2
co
me
s
her
e)
The heart
model is
the central
part in in
the MCTR
design. The heart design consists mainly of five parts, as illustrated in Fig. 2.
Except the difference in shape in the left and right ventricles, the whole heart model
is almost symmetrical along the centre plane. As shown in Fig. 2, parts A, B and E
represent the ventricles and the atriums. The ventricle part is separated into Part A
and B in order to minimize the difficulty in manufacturing the ventricle chambers.
Parts DKG and DV are two silicon rubber membranes that represent the atrium-
ventricle septum and the ventricle wall, and they are separated by Part C to
eliminate the potential motion interference between them. Besides these main parts,
some accessories such as heart valves, sealing components and motion mechanism
etc. are used to help mimicking the proper function of the model. Under the action
of the external motion control system, blood analogue is circulated in the heart
model to simulate the functioning of the heart. The arrows in the figure show the
flow direction of the blood analogue.
In the figure, LA is the abbreviation of left atrium, LV for left ventricle, RA for
right atrium, RV for right ventricle, mi for mitral valve, ao for aortic valve, ti for
tricuspid valve and po for pulmonary aorta.
In Parts A and B, the left and right ventricle chambers covered under the ventricle
sac
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DV are
filled with
water.
Water is
filled and
drained
through
flow
channels
near the
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Page 6 of 25
apex of the ventricle chambers. The flow channel and the ventricle chambers are
connected through honey combs that are tiled towards the ventricle bottom direction,
in order to eliminate the possible water jet effect acted on the ventricle sac DV when
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9 water is filling in the chambers to simulate the systolic phase.
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12 Fig. 3 shows the MRI measured geometry of the left and right ventricles at the
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15 instances of peak-systole and end-diastole in a heart cycle, and Fig. 4 shows the
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17 corresponding ventricular volume change in the left ventricle, which have been
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19 reported in a previous study (42). The MCTR design aims to give realistic description 20
21 of the cardiac motion and functioning, but does not need to duplicate every
22
23 anatomical details. The irregular shape of the right ventricular is very difficult to 24
25 fabricate mechanically, thus it is represented using the same geometry as that for the
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28 left ventricular, but working in the pressure range compatible with the pulmonary
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30 circulation. In the MCTR design, the ventricle sac DV in the unstressed condition
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32 exhibits the ventricle shape in the peak-systole in the rest condition, and the internal 33
34 wall of Part A and B are cut into the ventricle shapes in the end-diastole in the
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36 extreme exercise condition. When the amount of the water in the space between the 37
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38 ventricle sac and the internal wall of Part A and B is changed using the ventricular
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41 motion control motor and piston, blood analogue flows in and out of the space LV and
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43 RV to compensate the volume change induced by the water flow, thus mimicking the
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45 ventricular volume changes as shown in Fig. 4. The LA and RA chambers are
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47 represented with cylindrical shaped spaces whose volumes approximately equal the
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49 MRI measured left and right atrial volumes.
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51 (Figures 3 and 4 come here)
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54 Part DKG and Part E combined to represent the blood flow in the left and right atriums,
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the aorta
and the
pulmonary
artery.
Two heart
valves are
equipped
on the
silicon
septum
DKG, and they are functioned as the mitral valve and the tricuspid valve in the heart.
The two valves and the septum are attached to and driven by the motion control
mechanism which moves in the vertical direction, thus to simulate the bulging of the
septum in the heart in the diastolic phase. Two vertical channels in Part E represent
the roots of the aorta and the pulmonary artery. Two more heart valves are installed
near the inlet to the aorta and the pulmonary artery to simulate the aortic valve and
the pulmonary valve.
2.3 Motion design for the system
(Figures 5 and 6 come here)
Proper functioning of the heart model depends largely on the careful motion
planning and synchronisation of the motion control system in the septum driving
mechanism and the ventricle driving mechanism. Fig. 4 above shows the typical left
ventricular volume change in a heart cycle measured with MRI, which is used as the
blueprint in the motion profile design of the ventricular driving mechanism in the
MCTR design. To reduce the impact and vibrations in the driving motor and the
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mechanica
l parts in
the
MCTR,
the
volume
change in
Fig. 4 is
further
approxima
ted with
piece-wise
harmonic
waveforms, as exemplified in Fig. 5, which is represented by the following equation:
+ −
+ cos
0≤ <
2 2
+ −
= − cos
≤ <
2 2
+ −
− cos
≤ <
2 2
Equation (1)
In the equation, , , and are the maximum, the minimum, and the saddle
Page 8 of 25
point values in the volume change curve; and are the time corresponding to
the transition points in the waveform segments, and is the heart period. As can be
observed in Fig. 5, the harmonic waveforms shown is based on a set of example
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12 the patient-specific and disease-specific conditions which the researcher expect to
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14 simulate.
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17 For both the left and the right ventricles, a piston actuated by a linear motor is used to
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19 displace the water in the ventricular chamber (as shown in the illustration in Fig. 6),
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21 thus to induce the expansion and contraction of the ventricle sac and to achieve the
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23 designed ventricular volume change as described by equation 1. Since the stroke
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26 volume of the piston is proportional to the stroke of the piston, the following equation
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28 is applied to produce the prescribed volume profile in the ventricular chamber:
29
30 + − − cos
0≤
<
31 2 2
32 + −
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33 = + cos
≤
<
34 2 2
35 + −
36 2 + 2 cos
≤ <
37 Equation (2) 38
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40 In the equation, , , and are the maximum, the minimum, and the saddle
41
42 point values in the stroke profile curve; , and are the same as that in equation
43
44 (1). Considering the dimensions of the left and right ventricles measured in the MRI,
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46 in the current MCTR design the diameter of the piston head is chosen as 50mm. To 47
48 generate the stroke volume of about 70ml/beat at the rest condition, the piston should
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50 have a stroke of:
While to produce the stroke volume of about 110ml/beat (160ml/beat) in the extreme
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exercise condition (39), the piston should have a stroke of:
The working stroke of the piston can be chosen as 0.08+. To leave enough margins,
the overall stroke of the piston is chosen as 0.1+, which can be used in the selection
of the linear motor. For specific modelling cases, the stroke value can be adapted to
produce predefined stroke output to suit the different application requirements. For
example, to model the rest condition in a healthy adult subject, the heart period is set
as 0.83/ (with heart rate being 72012/ +34⁄ ) and the stroke is chosen as 0.05+
(which is greater than the 0.036+ calculated above, considering that there are
certain levels of regurgitant flows in the mitral and aortic valves, which reduce the
overall cardiac output produced). The stroke profile of the piston in the ventricle
chambers can be calculated using equation (2), and the velocity and acceleration
profiles of the piston are calculated based the first order and second order
differentiation of the equation (2). Fig. 7 shows the calculated motion profile for this
example condition, in which the maximum velocity of the piston is about 0.24+⁄/,
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and the
maximum
acceleratio
n is
3.2+⁄/ .
The
motion
profile for
the
exercise condition have the same shape as illustrated above but elevated stroke,
velocity and acceleration values but reduced heart period value, due to the increased
cardiac contractility and heart rate in the exercise condition. For the extreme
exercise condition of 180012/ +34⁄ for the heart rate and 160+5 012⁄ for
the stroke volume (39), using the piston stroke of 0.1+ calculated above, the
maximum velocity of the piston is about 2.41+⁄/, and the maximum acceleration is
132+⁄/ . While to simulate the heart failure condition, the piston stroke needs to be
reduced and the heart rate increased. The detailed motion profiles for the stroke,
velocity and acceleration can be calculated in the same way as
Page 10 of 25
above.
(Figure 7 comes here)
8 The atrial-ventricular septum moves in a heart cycle due to the contraction of the heart
9
10 muscle, which is in phase with the ventricular motion but with a reduced magnitude, 11
12 thus the septum actuating mechanism has the same motion trajectory as the piston for
13
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15 the ventricle. After checking the MRI measured data, stroke for the septum driving
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17 mechanism is set as 25++, which produces a maximum velocity is 0.496+⁄/ and a
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19 maximum acceleration of 25.9+⁄/ corresponding to the extreme exercise condition 20
21 in a healthy adult subject.
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24
25 2.4 Specification of the linear motors
26
27 Selection of the driving motor is based on the force, the stroke, the maximum velocity
28
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30 and the maximum acceleration requirements for the ventricle and atrium actuating
31
32 pistons. The maximum velocity and the maximum acceleration for the ventricle
33
34 actuating pistons have been evaluated above. Since this is a light-load system, and the
35
36 two ventricles working in the similar velocity and acceleration conditions, it is 37
38 rational to consider using the same motor selection to drive the four motion
39
40 mechanisms in the ventricles and the atrial-ventricular septum. The following 41
42 evaluation of the force requirement is based on the left ventricle driving motor.
43
44
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46 The piston driving force is a summation of the pressure force, the inertial force due to
47
48 fluid acceleration, and the frictional force. To calculate the pressure force, the peak
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50 pressure in the left ventricular chamber is set as 200++67 (which gives sufficient
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margin over the upper limit of 160++67 for the hypertension condition (43)), and
the pressure force is estimated as:
Page 11 of 25
1
2
3 F P Ap = ⋅ =13.6 10× 3 ×9.8×0.2×0.25π×0.052 = 52.34 (N) 4
5
6 The inertial force exists in the piston and the circulating fluid in the heart chambers
7
8 and the flow channel between the aortic valve and the compliance element, with the
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10 piston plays the major part due to the greater density of the steel piston material 11
12 compared with the density of the blood analogue. Assuming the piston has a diameter
13
14 of 50++ and a thickness of 10++, while the piston rod has a diameter of 10++ 15
1617 and a length of 100++, the piston assembly thus has a mass of:
1819 +=8∙ =7.8×109× ∙ 0.1×0.01 +0.01×0.05 ⁄4=0.2144:7
20
21 and the inertial force associated with the maximum acceleration is:
22
23 ; =+∙2=0.2144×132=28.3<
24
25 Assume the friction acted on the driving mechanism is 5<, the overall force to be
26
27
28 applied on the piston is:
29
30 ;=;=+; +;> =52.34+28.3+5=85.64<
31
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32 Use a safety factor of 2~3, and round the force to a nominal value in the product
33
34 catalogue, the force output from the piston is selected as 200<. The right ventricle 35
3637 has a smaller pressure level thus the force requirement is also smaller. The atrial
38
39 septum driving piston not only works under lower pressure but also experiences
40
41 smaller acceleration. Since 200< is not a big value, it is convenient to use the same
42
43 specifications for all the four ventricle and atrium driving pistons. The specifications 44
45 for the linear motors to drive the ventricle/atrium pistons are then summarised and
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47 listed in Table 2.
48
49
50 (Table 2 comes here)
2.5 System accessory
Besides the main parts of the heart model, the piston and the driving motor, some
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For Peer Review Only
accessories are needed to form the complete MCTR system as detailed in the
following.
8
9 2.5.1 Valve and compliance units, to simulate the physiological impedance
10
11 Sharp et. al. (2) analysed the characteristics of the physiological impedance in the
12
13 artery network, and suggested that the three-element Windkessel model is the simplest
14
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16 model that could describe both the low frequency and high frequency features of the
17
18 physiological impedance, while the two-element Windkessel model as used in
19
20 majority of the previous MCTR designs was unable to reveal the high frequency
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22 features. Thus the three-element Windkessel model is used in both the systemic and 23
24 the pulmonary loops in the current MCTR design. For this purpose, two throttle
25
26 valves are used to function as the characteristic resistance and the peripheral 27
28 resistance, and a compliance unit to simulate the elastic effect of the artery. Generally,
29
30
31 the overall resistance value produced by the two resistances equals to the ratio of the
32
33 mean pressure to the mean flow rate in the loop, and the characteristic resistance is
34
35 about one tenth of the peripheral resistance. Besides, the human aorta has a diameter 36
37 of about 25++, thus to have better geometrical resemblance and to avoid the
38
39 unnecessary pressure loss and flow disturbance, the internal diameter of the throttle 40
41 25++. The compliance unit is made of an elastic rubber sac 42 valves is chosen to be
43
44 emerged in a container filled with compressed air, so that different values of air
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46 pressure result in different values of the compliance. During system commissioning,
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48 the air pressure in the compliance and the openings of the valves are continuously 49
50 adjusted, until the pressure and flow responses in the system match that in the
physiological conditions as reported in the literature. Page 13 of 25
1
2
3 2.5.2 Water tank, to provide the necessary flow reserve 4
5 A normal adult of 75kg body weight has about 5 of blood in the circulation system
6
7
8 (40,41). In the MCTR design, two water tanks, each has an overall volume of 4 and
9
10 contains 3 of blood analogue, are used to represent the blood storage capacity in the
11
12 systemic and the pulmonary veins. The overall volume of the blood analogue exceeds 13
14 that of 5 in the human body but this does not influence the system response. The 15
16 water tanks can be placed on the same horizontal level with the other system parts, to
17
18
19 simplify the system settlement; or they can be placed on shelves so that they are on a
20
21 higher altitude to produce the right level of the preload (about 10++67 in the
22
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23 normal condition) to the left and right atriums.
24
25
26
27 2.5.3 Silicon rubber tube, to connect different parts in the system
28
29 Silicon rubber tube provides a flexible but water-tight connection of the components
30
31 in the MCTR design. To be compatible with the geometry of the artery, the silicon 32
33 rubber tube also has an internal diameter of 25++.
34
35
36
37 2.5.4 Blood analogue
38
3940 To match the density of 1060:7 +⁄ 9 and the viscosity of 3.2?@ in the real human
41
42 blood (40,41), a mixture of glycerine and water is used as the working fluid. If the
43
44 MCTR is to be used for applications involving sophisticated optical observations of 45
46 the velocity distributions, such as in the Particle Image Velocimetry measurement of
47
48 the flow field, the test section often needs to be manufactured using transparent 49
50 materials (e.g., Perspex), which has a different refractive index to the blood analogue
and may cause optical distortion in the images captured. In such situations, chemicals such as sodium
iodide (<2A) can be added to the blood analogue so that the refractive
Page 14 of 25
index of the fluid matches the index for the transparent wall material in the
observation windows, to eliminate the potential of optical distortion. However, this
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will change the density and the viscosity of the final working fluid and a compromise
8
9 among the different aspects of the fluid properties needs to be considered.
10
11
12
13 2.5.5 Pressure and flow transducers
14
15
16 Three pressure transducers and two flow-rate transducers are installed in each loop, to
17
18 measure the pressure in the atrium, the ventricle and the main artery, and the flow
19
20 rates in the artery and the vein. The operating range of the pressure transducers is
21
22 chosen as −20~300++67, in case there may be temporary pressure overload in the
23
24 system. Electromagnetic type or ultrasound type flow transducers are good candidates
25
26 for the measurement of the pulsatile flow in the systematic artery and the pulmonary 27
28 ⁄ and it may
29 artery positions. Considering that the
normal cardiac output is 5 +34
30
31 raise to about 28 +34⁄ in the maximum exercise condition (39), the operating range
32
33 of the flow transducer can be set as −10~30 +34⁄ . Flows in the simulated
34
35 systematic and pulmonary vein positions are much steady, so the rotameters can be
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37 used in these locations to save the expense.
38
39
40
41 2.5.6 Computer monitoring and control system
42
43 A computer monitoring and control system is needed to record the pressure and flow
44
45
46 response in the MCTR, as well as to command the linear motors to generate the
47
48 necessary designed motions in the ventricle/atrium actuating pistons. A normal PC
49
50 enhanced with the hardware (suitable A/D & D/A board) and the software
(accompanying data acquisition and motion control program) support is OK for the
purpose. Besides, the pressure and flow signals from the transducers are weak signals,
and need to be conditioned and amplified before being picked up by the data
Page 15 of 25
1
2
3 acquisition system, thus the signal conditioning and amplifying circuits accompanying
4
5 the transducers need to be purchased. The motion command signals sent by the 6
7 computer to the linear motors often need to be amplified with a separate amplifier as
8
9 well. With the computer monitoring and control system, signals from the pressure and
10
11
12 flow transducers and from the motor driving channels can be displayed real-time on
13
14 the computer screen or saved as data files for further post-processing.
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15
16
17 2.5.7 Other application specific components
18
19
20 The MCTR system provides the fundamental platform for the in vitro study, while for
21
22 specific applications it often needs to be adapted or expanded to include other 23
24 measurement components. For example, to observe the flow field in a new artificial
25
26 heart design or in a patient-specific vessel segment geometry, the artificial heart or the 27
28 vessel segment can be fabricated using transparent materials and then embedded in
29
30
31 the MCTR. Specific flow field measurement equipment, such as Laser Doppler
32
33 Anemometry, Particle Image Velocimetry, CCD camera etc. can then be attached to
34
35 the MCTR for flow measurement.
36
37
38
39 Discussion
40
41 MCTR is widely used in the in vitro study of the cardiovascular physiology. Plenty of
42
43 MCTRs have been built in the past. Although the general configurations of these 44
45 MCTRs were introduced in the literature, the structure and motion design details have
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47
48 seldom been explained. This paper presents a MCTR design with sophisticated
49
50 structures and describes the technical details that were missing in the literature, thus
provides a reference to researchers who are planning to build their own MCTRs. Compared with the
previous MCTR designs, the current design adopts improved
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Page 16 of 25
cardiac and vascular system models, thus can provide more in-depth knowledge about
the cardiac dynamics and vascular hemodynamics to the researchers. The proposed
MCTR design when fully implemented can be used as a platform to aid the clinical 8
9 study of the native cardiovascular system in healthy and diseased conditions and the
10
11
12 performance evaluation of prosthetic cardiovascular devices.
13
14
15 The proposed MCTR design is focused on the real-size modelling of the circulatory
16
17 system. It is possible that in some situations scaled-up modelling is need to facilitate
18
19 the observation of the flow field details in some confined regions of the
20
21 cardiovascular flow. In such cases the dimensional analysis can be applied to change
22
23 the geometrical dimensions of the cardiac/vascular model and the motion parameters 24
25 (velocity, frequency etc.), and to maintain the non-dimensional numbers (e.g.,
26
27
28 Reynolds’ number, Womersley number) so that the dynamic similarity between the
29
30 MCTR model system and the original physiological system is guaranteed. Once the
31
32 revised geometrical dimensions and the notion parameters are decided, the same 33
34 procedures as presented in this paper can be applied to determine the design
35
36 parameters for the actuating pistons and the driving linear motors, thus to finalise the
37
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38 MCTR design.
39
40
41
42 The study presents a sample MCTR design, elaborates on the different aspects of the
43
44 structure and motion design considerations, and demonstrates the procedures for
45
46 determining the geometrical parameters and the motion profiles. Researchers can use
47
48 this as the reference and adapt the design by revising the geometrical and kinematic
49
50 parameters, removing and incorporating system components, to suit different research
51
52 needs. For example, if the motion of the atrial-ventricular septum is not needed then 53
54 the related parts can be moved, and this helps to further simplify the system design
55
Page 17 of 25
1
2
3 and reduce the expense; if there is no requirement to model the exercise condition
4
5 then the stroke, velocity, and acceleration requirements of the driving mechanism can 6
7 all be lowered so that cheaper motors can be used; if the pulmonary loop is not
8
9 relevant then only half of the current MCTR design can suffice the research needs.
10
11
12 A deficiency of the current study is that the designed MCTR has not been physically
13
14
15 built, thus no pressure and flow response can be demonstrated for comparison with
16
17 the typical response curves reported in the physiological textbooks for validation
18
19 purpose. This will be conducted in the next stage of the study once the necessary 20
21 resources are secured.
22
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24
25 Conclusion
26
27 This paper presents the detailed structure and motion design of a sophisticated MCTR 28
29 system, and examines the important issues such as the determination of the ventricular
30
31
32 motion waveform, modelling of the physiological impedance, etc. in the MCTR
33
34 designing. The study demonstrates the overall design procedures from the system
35
36 conception, cardiac model devising, motion planning, to the motor and accessories
37
38 selection. This can be used as a reference to aid researchers in the design and 39
40 construction of their own in-house MCTRs for cardiovascular studies.
41
42
43
44 Conflicts of interest
45
46 None declared.
47
48
49
50 References
1. Leefe SE, Gentle CR. A review of the in vitro evaluation of conduit-mounted cardiac valve
prostheses. Med Eng Phys. 1995 Oct;17(7):497–506.
2. Sharp MK, Dharmalingham RK. Development of a hydraulic model of the human systemic
circulation. ASAIO J. 1999 Dec;45(6):535–40.
Journal of Medical Engineering & Technology
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52
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55
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Page 18 of 25
3. Boes S, Ochsner G, Amacher R, Petrou A, Meboldt M, Daners MS. Control of the Fluid Viscosity in
a Mock Circulation. Artif Organs. 2018 Jan;42(1):68–77.
4. Heise M, Krüger U, Rückert R, Pfitzman R, Neuhaus P, Settmacher U.
Correlation of Intimal Hyperplasia Development and Shear Stress Distribution at
8 the Distal End-side-anastomosis, in vitro Study Using Particle Image
9 Velocimetry. Eur J Vasc Endovasc Surg. 2003 Oct 1;26(4):357–66. 10
11 5. Kaufmann TAS, Wong KC, Schmitz‐Rode T, Steinseifer U. Mimicking of 12 Cerebral
Autoregulation by Flow-Dependent Cerebrovascular Resistance: A
13 Feasibility Study. Artif Organs. 2012 Apr 1;36(4):E97–101.
14
15 6. May-Newman K, Vu V, Herold B. Modeling the Link between Left Ventricular
16
17 Flow and Thromboembolic Risk Using Lagrangian Coherent Structures. Fluids.
18 2016 Nov 22;1(4):38.
19
20 7. McKenzie SC, Dunster K, Chan W, Brown MR, Platts DG, Javorsky G, et al. 21
Reliability of thermodilution derived cardiac output with different operator 22 characteristics. J Clin
Monit Comput. 2018 Apr 1;32(2):227–34.
23
24 8. Misgeld BJE, Werner J, Hexamer M. Robust and self-tuning blood flow control 25
during extracorporeal circulation in the presence of system parameter 26 uncertainties. Med Biol
Eng Comput. 2005 Oct 1;43(5):589–98. 27
28 9. Ninomiya S, Tokaji M, Tokumine A, Kurosaki T. Virtual patient simulator for
29 the perfusion resource management drill. J Extra Corpor Technol. 2009
30 Dec;41(4):206–12. 31
32 10. Piatti F, Palumbo MC, Consolo F, Pluchinotta F, Greiser A, Sturla F, et al.
33 Experimental quantification of the fluid dynamics in blood-processing devices
34 through 4D-flow imaging: A pilot study on a real oxygenator/heat-exchanger
35 module. J Biomech. 2018 Feb 8;68:14–23. 36
37 11. Seong J, Jeong W, Smith N, Towner RA. Hemodynamic effects of long-term
Journal of Medical Engineering & Technology
1
2
3
4
5
6
7
51
52
53
54
55
56
57 58 59 60 URL: http://mc.manuscriptcentral.com/tmet Email: John.Woodcock@CardiffandVale.wales.nhs.uk32
38
39 morphological changes in the human carotid sinus. J Biomech. 2015 Apr
40 13;48(6):956–62.
41
42 12. Valverde I. Three-dimensional Printed Cardiac Models: Applications in the Field 43 of
Medical Education, Cardiovascular Surgery, and Structural Heart 44 Interventions. Rev Espanola Cardiol
Engl Ed. 2017 Apr;70(4):282–91.
45
46 13. Brücker C. Dual-camera DPIV for flow studies past artificial heart valves. Exp
47 Fluids. 1997 Apr 1;22(6):496–506. 48
49 14. Crosby JR, DeCook KJ, Tran PL, Smith RG, Larson DF, Khalpey ZI, et al.
50 Physiological characterization of the SynCardia total artificial heart in a mock circulation
system. ASAIO J Am Soc Artif Intern Organs 1992. 2015 Jun;61(3):274–81.
15. Crosby JR, DeCook KJ, Tran PL, Betterton E, Smith RG, Larson DF, et al. A
Physical Heart Failure Simulation System Utilizing the Total Artificial Heart and
Modified Donovan Mock Circulation. Artif Organs. 2017 Jul;41(7):E52–65. Page 19 of 25
1
2
3 16. Donovan FM. Design of a hydraulic analog of the circulatory system for 4 evaluating artificial hearts.
Biomater Med Devices Artif Organs. 1975;3(4):439–
5 49.
6
7 17. Feng Z, Umezu M, Fujimoto T, Tsukahara T, Nurishi M, Kawaguchi D. In vitro 8 hydrodynamic
characteristics among three bileaflet valves in the mitral position.
9 Artif Organs. 2000 May;24(5):346–54.
10
11 18. Feng Z, Nakamura T, Fujimoto T, Umezu M. In vitro investigation of opening
12 behavior and hydrodynamics of bileaflet valves in the mitral position. Artif
13 Organs. 2002 Jan;26(1):32–9.
Journal of Medical Engineering & Technology
51
52
53
54
55
56
57 58 59 60 URL: http://mc.manuscriptcentral.com/tmet Email: John.Woodcock@CardiffandVale.wales.nhs.uk33
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14
15 19. Förster F, Kaufmann R, Reul H, Rau G. A small pulsatile blood pump for
16
17 ventricular support during end-stage heart failure. Artif Organs. 2000
18 May;24(5):373–6. 19
20 20. Geier A, Kunert A, Albrecht G, Liebold A, Hoenicka M. Influence of
21 Cannulation Site on Carotid Perfusion During Extracorporeal Membrane 22 Oxygenation in a
Compliant Human Aortic Model. Ann Biomed Eng. 2017
23 Oct;45(10):2281–97.
24
25 21. Giridharan GA, Koenig SC, Kennington J, Sobieski MA, Chen J, Frankel SH, et 26 al. Performance evaluation
of a pediatric viscous impeller pump for Fontan
27 cavopulmonary assist. J Thorac Cardiovasc Surg. 2013 Jan 1;145(1):249–57.
28
29 22. Gregory SD, Schummy E, Pearcy M, Pauls JP, Tansley G, Fraser JF, et al. A 30 Compliant, Banded Outflow
Cannula for Decreased Afterload Sensitivity of 31 Rotary Right Ventricular Assist Devices. Artif Organs. 2015 Feb
1;39(2):102–9. 32
33 23. Horvath D, Byram N, Karimov JH, Kuban B, Sunagawa G, Golding LAR, et al. 34
Mechanism of Self-
Regulation and In Vivo Performance of the Cleveland Clinic 35
Continuous-Flow Total Artificial Heart. Artif Organs. 2017 May;41(5):411–7.
36
37 24. König CS, Clark C. Flow mixing and fluid residence times in a model of a
38
39 ventricular assist device. Med Eng Phys. 2001 Mar;23(2):99–110.
40
41 25. Lim E, Dokos S, Salamonsen RF, Rosenfeldt FL, Ayre PJ, Lovell NH. Effect of 42 Parameter Variations on
the Hemodynamic Response Under Rotary Blood Pump 43 Assistance. Artif Organs. 2012 May 1;36(5):E125–37.
44
45 26. Mansouri M, Gregory SD, Salamonsen RF, Lovell NH, Stevens MC, Pauls JP, et
46 al. Preload-based Starling-like control of rotary blood pumps: An in-vitro 47 evaluation. PLOS ONE.
2017 Feb 17;12(2):e0172393. 48
49 27. Morsi YS, Sakhaeimanesh A, Clayton BR. Hydrodynamic evaluation of three 50 artificial aortic valve chambers.
Artif Organs. 2000 Jan;24(1):57–63.
Journal of Medical Engineering & Technology
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2
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4
5
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7
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52
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57 58 59 60 URL: http://mc.manuscriptcentral.com/tmet Email: John.Woodcock@CardiffandVale.wales.nhs.uk34
28. Ng BC, Kleinheyer M, Smith PA, Timms D, Cohn WE, Lim E. Pulsatile
operation of a continuous-flow right ventricular assist device (RVAD) to improve
vascular pulsatility. PLOS ONE. 2018 Apr 20;13(4):e0195975. Page 20 of 25
29. Ng BC, Smith PA, Nestler F, Timms D, Cohn WE, Lim E. Application of
Adaptive Starling-Like Controller to Total Artificial Heart Using Dual Rotary
Blood Pumps. Ann Biomed Eng. 2017 Mar 1;45(3):567–79.
30. Nishida M, Asztalos B, Yamane T, Masuzawa T, Tsukiya T, Endo S, et al. Flow
8 visualization study to improve hemocompatibility of a centrifugal blood
pump.
9 Artif Organs. 1999 Aug;23(8):697–703.
10
11 31. Noor MR, Ho CH, Parker KH, Simon AR, Banner NR, Bowles CT.
12 Investigation of the Characteristics of HeartWare HVAD and Thoratec 13 HeartMate II
Under Steady and Pulsatile Flow Conditions. Artif Organs. 2016
14
15 Jun 1;40(6):549–60.
16
17 32. Pauls JP, Stevens MC, Bartnikowski N, Fraser JF, Gregory SD, Tansley G. In
18 Vitro Comparison of Active and Passive Physiological Control Systems for
19 Biventricular Assist Devices. Ann Biomed Eng [Internet]. 2016 [cited 2018 May
20 21]; Available from: https://link.springer.com/article/10.1007%2Fs10439-015-
21 1425-1 22
23 33. Pauls JP, Stevens MC, Bartnikowski N, Fraser JF, Gregory SD, Tansley G. 24 Evaluation
of Physiological Control Systems for Rotary Left Ventricular Assist 25 Devices: an in vitro Study.
Ann Biomed Eng. 2016 Aug 1;44(8):2377–87. 26
Journal of Medical Engineering & Technology
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27 34. Petrou A, Lee J, Dual S, Ochsner G, Meboldt M, Daners MS. Standardized 28
Comparison of Selected Physiological Controllers for Rotary Blood Pumps: In
29 Vitro Study. Artif Organs. 2018 Mar 1;42(3):E29–42.
30
31 35. Schumer E, Höffler K, Kuehn C, Slaughter M, Haverich A, Wiegmann B. In-
32 vitro evaluation of limitations and possibilities for the future use of
33 intracorporeal gas exchangers placed in the upper lobe position. J Artif Organs.
34 2018 Mar 1;21(1):68–75. 35
36 36. Sénage T, Février D, Michel M, Pichot E, Duveau D, Tsui S, et al. A mock 37
38 circulatory system to assess the performance of continuous-flow left ventricular 39 assist devices
(LVADs): does axial flow unload better than centrifugal LVAD? 40 ASAIO J Am Soc Artif Intern
Organs 1992. 2014 Apr;60(2):140–7.
41
42 37. Stephens AF, Stevens MC, Gregory SD, Kleinheyer M, Salamonsen RF. In Vitro 43
Evaluation of an Immediate Response Starling-Like Controller for Dual Rotary 44 Blood Pumps. Artif
Organs. 2017 Oct;41(10):911–22. 45
46 38. Wu EL, Nestler F, Kleinheyer M, Stevens MC, Pauls JP, Fraser JF, et al. 47 Pulmonary
Valve Opening With Two Rotary Left Ventricular Assist Devices for
48 Biventricular Support. Artif Organs. 2018 Jan 1;42(1):31–40.
49
50 39. Burton DA, Stokes K, Hall GM. Physiological effects of exercise. Contin Educ
Anaesth Crit Care Pain. 2004 Dec 1;4(6):185–8.
40. Guyton AC, Hall JE. Textbook of Medical Physiology. 11 edition. Philadelphia,
Pa: Saunders; 2005. 1152 p. Page 21 of 25
1
2
3 41. Levick RJ. An Introduction to Cardiovascular Physiology 5E. 5 edition. London:
4 CRC Press; 2009. 432 p. 5
6 42. Korakianitis T, Shi Y. A concentrated parameter model for the human 7 cardiovascular system including
heart valve dynamics and atrioventricular
8 interaction. Med Eng Phys. 2006 Sep;28(7):613–28.
9
10 43. Kotchen TA. Developing Hypertension Guidelines: An Evolving Process. Am J
11 Hypertens. 2014 Jun 1;27(6):765–72.
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Table 1. Operating parameters for the MCTR design 2
Heart rate (bpm) 30~180
Ventricular pressure (mmHg) 0~200
Atrial pressure (mmHg) 0~50
Arterial pressure (mmHg) 30~200
Cardiac output (L/min) 2~18
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Table 2. Specifications of the linear motors
Stroke (m) Force output (N) Maximum
velocity(m/s)
Maximum
acceleration (m/s 2 )
200 0.1 3 150
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47 Fig. 2 Section view of the heart model in the test rig
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Fig. 1 System configuration of the mock circulatory test rig
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( a) End systolic phase ( b) End diastolic phase
Fig 3. Ventricle geometry reconstructed from MRI results
Fig. 4 Volume change of the left ventricle in a heart cycle measured with MRI
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Fig. 5 Smoothed and approximated left ventricular volume changing 3
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Fig. 6 Illustration of the ventricular motion actuated by the motor driven piston
( a ) Stroke ( b) Velocity ( c) Acceleration
Fig. 7 Motion profile of the ventricle actuating piston in an example of the rest
condition in a healthy adult subject
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