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The department of Medical Engineering
סימולטור לימודי דינמי: שם הפרויקט להערכת זרימה בחבל הטבור באמצעות
אולטרה סאונד דופלר
Project Name: Dynamic Simulator for Umbilical Flow Assessment
Using Doppler Ultrasound
Project book
Ofir AgranatiStudent Name:
**************ID:
Dr. Sara NaftaliSupervisor Name:
20//05/2015Submission Date:
1
1 1. Table of Contents2 Lists.....................................................................................................4
2.1 Figures.............................................................................................42.2 Tables...............................................................................................4
3 6......................................................................................תקציר מנהלים4 Executive Summary............................................................................85 Introduction.........................................................................................96 Literature review...............................................................................10
6.1 Anatomy of the umbilical cord........................................................106.2 Umbilical cord flow physiology........................................................116.3 Doppler Ultrasonography................................................................126.4 Medical simulation..........................................................................136.5 Base flow system............................................................................14
7 Objectives..........................................................................................157.1 Main Objective................................................................................157.2 Client and users..............................................................................157.3 Requirements.................................................................................16
7.3.1 Client requirements....................................................................167.3.2 Engineering Requirements.........................................................16
8 Method...............................................................................................178.1 The Flow System............................................................................18
8.1.1 Pump controller and power supply.............................................188.1.2 A\D card.....................................................................................198.1.3 Venturi sensor............................................................................208.1.4 Pump..........................................................................................218.1.5 Fluid reservoir............................................................................21
8.2 The GUI..........................................................................................228.2.1 GUI interface..............................................................................228.2.2 GUI Functions............................................................................238.2.3 GUI Functions Results explanation............................................26
8.3 The Application Model....................................................................278.3.1 Model Calculations.....................................................................278.3.2 Model Design.............................................................................298.3.3 The Lid.......................................................................................318.3.4 Assembly....................................................................................318.3.5 Water drainage...........................................................................328.3.6 Model Modifications....................................................................338.3.7 US Compatibility.........................................................................34
8.4 The US device................................................................................349 Results...............................................................................................35
9.1 Physician Examination...................................................................3510 Discussion.........................................................................................37
10.1 Comparison to Physiological Data..................................................3710.2 Physician Review...........................................................................40
2
11 Conclusion........................................................................................4012 Suggestion for Future Research.....................................................41
12.1 Finalizing the System.....................................................................4112.2 The Experimental System for the Medical Lab...............................4212.3 Application model modification.......................................................4212.4 Ultrasound and flow field correlation..............................................42
13 References........................................................................................4314 Appendix...........................................................................................44
14.1 National Instrument USB-6009 Electrical drawing..........................4414.2 Venturi tube drawing.......................................................................4514.3 Gear pump specifications...............................................................4614.4 Project Process..............................................................................4714.5 Direction for Use (DFU)..................................................................48
3
2 Lists2.1 Figures
Figure 3.1 Illustration of the system and its components..................................7Figure 6.1 The UC Anatomy [14]....................................................................11Figure 6.2 Spectral Doppler scan of the carotid artery [5].............................12Figure 6.3 Laerdal's SimMan emergenrcy response training [8]....................13Figure 6.4 Simbionix's Lap Mentor laparoscopy clinical training [9]...............14Figure 6.5 Biometric Fetal Ultrasound Training Phantom by CIRS [15].........14Figure 6.6 The experimental system used at the ME laboratory [6]...............15Figure 8.1 Illustration of the system and its components................................17Figure 8.2 The system and its components....................................................18Figure 8.3 Pump controller and power supply................................................19Figure 8.4 National instrument USB-6009......................................................20Figure 8.5 Electronic differential sensor.........................................................20Figure 8.6 Venturi tube...................................................................................21Figure 8.7 Gear pump....................................................................................21Figure 8.8 Water reservoir..............................................................................22Figure 8.9 The GUI interface..........................................................................22Figure 8.10 The final prototype of the application model with the UC model. 27Figure 8.11 Perspex lid, standard 3 views with isometric view, all units are in meters............................................................................................................30Figure 8.12 The final container with the vessel, connenctors and and sponge like material....................................................................................................30Figure 8.13 Perspex lid, standard 3 views with isometric view, units are in meters............................................................................................................31Figure 8.14 The final lid with latex sheet........................................................31Figure 8.15 Box and lid assembly, units are in [cm].......................................32Figure 8.16 Water overflow control.................................................................33Figure 8.17 Leak-proof coupler......................................................................33Figure 8.18 GE Logiq C5 Premium................................................................35Figure 9.1 The system values for the physician review..................................35Figure 9.2 US image of the vessel.................................................................36Figure 9.3 US Doppler spectrography of the vessel.......................................37Figure 10.1 The model velocity waveform......................................................38Figure 10.2 A real UC velocity waveform [12]................................................38Figure 10.3 Model diameter measurement taken with the US tools...............39Figure 10.4 Screenshot taken from the US Doppler spectrography of the simulator video (https://youtu.be/brBYPSaJ9Cw)...........................................39Figure 10.5 Screenshot taken from Introduction to Doppler Ultrasound [13]..40
2.2 Tables
Table 6.1 Combined cardiac output and distribution in human fetus. (units are mL/min ) [4]....................................................................................................12
4
Table 8.1 Pump controller functionality..........................................................19Table 8.2 GUI function comparison................................................................24Table 8.3 GUI function comparison numeric results.......................................26Table 9.1 The system values for the physician review...................................35
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תקציר מנהלים3 כחלק מבדיקה שגרתית של עובר, נעשית הערכה מקיפה של ממדי חבל הטבור
זרימת הדם אל זרימת הדם שבתוכו. הבדיקה מאפשרת לרופא לאמוד את ואפיון
העובר ולהעריך האם קיימת מצוקה עוברית או בעיות שונות המיוחסות לאופי זרימת
הדם בטבור. בדיקת אולטרה-סאונד דופלר מאפשרת בדיקה של אופי הזרימה ע"י
שימוש באפקט דופלר. במהלך הכשרתו של מתמחה אולטרה-סאונד, על המתמחה
להתנסות בבדיקת תרחישים שונים אשר לעיתים אינם זמינים. נכון להיום, אין פתרון
הדופלר בדיקת את לחוות למתמחה המאפשרים זה מסוג תנאים מדמה אשר
ולהתאמן באופן אפקטיבי.
פתרונות שונים לאימון רופאים מתמחים בתחומים מגוונים קיימים כיום במרכזי
סימולציה אשר ממוקמים במרכזים רפואיים. במרכזים אלו קיימים מכשירי סימולציה
שונים המדמים תרחישים אשר בזמן אמת עלולים לסכן חיים.
ידמה סימולציה אשר ולבנות אבטיפוס למכשיר הינה לתכנן מטרת הפרויקט
זרימה בחבל הטבור בתוך הסביבה המקיפה אותו כאשר בדיקת אפיון הזרימה, תיערך
באמצעות מכשיר אולטרה סאונד קיים. המערכת תזרים נוזל בזמן אמת, התרחיש יוזן
את ולאבחן הזרימה את לזהות יידרש והמתמחה מחשב באמצעות המאמן ע"י
מאחוריה העומד –התרחיש רפואית לסימולציה המרכז עבור בוצע הפרויקט .
. כ"כ, המערכת תשמשסימולטק בהנהלתו של פרופ' רוני טפר, המרכז רפואי מאיר
כעמדת מעבדה באפקה לבצוע ניסויים ולמחקר.
] מחלוקת לשלושה מרכיבים עיקריים: מחשב, מערכת זרימה 3.1 איור המערכת [
ומודל אשר מדמה חבל טבור בסביבתו. הזרימה במערכת נוצרת ע"י משאבה אשר
) לאנלוגי מדיגיטלי אות המרת וכרטיס בקר דרך אישי מחשב ע"י ).D\Aנשלטת
הזרימה מתרחשת במודל של חבל הטבור, חיישני לחץ, מאגר המים והצנרת אשר
מחברת אותם למשאבה. את מאפייני הזרימה ניתן לשנות ע"י הזנת נתונים למחשב
) גרפי ). הזרימה נמדדת פעמיים, פעםGUIבאמצעות תוכנה עם ממשק משתמש
מכשיר ע"י שניה ופעם ולמאמן, לתוכנה משוב לצורך הבקרים ע"י אחת
האולטרה-סאונד של המתמחה.
6
Figure 3.1 Illustration of the system and its components
של ופיזיולוגיה אנטומיה בנושאי מקיף ספרות סקר בוצע מהפרויקט, כחלק
הפרויקט יתבסס עליה אשר הזרימה מערכת דופלר, אולטרה-סאונד הטבור,
פיזיקלית מבחינה יתאים אשר דגם לבנות מנת על רפואיות. וסימולציות
מהפן מלאכותיות רקמות המדמים חומרים אחר חיפוש נערך לאולטרה-סאונד,
הפיזיקלי והשוואת תכונות אלו לרקמות פיזיולוגיות.
המערכת. של הפרויקט בתוצאות ודיון תוצאות תכנון, מכיל הפרויקט ספר
התוצאות הושגו ע"י בדיקת רופא מומחה בתחום האולטרה-סאונד ומראות כי אכן ניתן
יהיה להשתמש במערכת זו ככלי לימודי. הבדיקות בוצעו ע"י מכשיר אולטרה-סאונד
שנרכש ע"י מכללת אפקה לצורך כך ולפרויקטים עתידיים.
תכנות ממשק משתמש פיזיולוגית, זרימה כגון: רבים נושאים כולל הפרויקט
ואלקטרוניקה. המערכת תשמש תחילה לסימולציות בסיסיות עם מודל טבור בסיסי,
ודגמים מתקדמים אפשרויות בעתיד לכלול יוכלו המכשיר של מודלים מתקדמים
הטבור באמצעותלחבל מעקב הכוללים נוספים דם בכלי לזרימות ולפלטפורמה
האולטרה-סאונד דופלר.
7
4 Executive SummaryAs part of fetus examination routine, an extensive evaluation of umbilical
cord (UC) and its blood flow is required. The examination enables the
physician to evaluate the hemodynamic state of the fetus and diagnose
whether there is fetal distress or other hemodynamic related problems. The
Doppler ultrasound (DUS) examination enables a detailed view of the flow
properties using the Doppler effect. During the ultrasound (US) physician
training, the trainee must practice different scenarios which may not frequently
occur. As of today, no solution that mimics these conditions for an effective
physician practice is available.
There are different solution systems that can help physician to practice
in various situations without patients. These simulators mimic life risking
situations of varied practice fields and located in simulation facilities centers. .
The project goal was to design and build a prototype for a simulation
device which mimics a pulsatile blood flow in an UC in its natural fluid
environment, and is compatible with US and DUS monitoring. The system
contains a real time flow that can be controlled by a trainer using a personal
computer (PC). The trainee will be required to estimate the flow and diagnose
the scenario. The project was conducted as a request of Simultech, Meir
Hospital medical simulation facility, under the supervision of Professor Roni
Tepper. In addition the system will be used at Afeka laboratory for further
research and student lab.
The system [Figure 3.1] is divided into three main components; PC, flow
system and an application model that mimics the UC in its natural
environment. The flow is generated by a PC controlled pump that receives a
signal via analog to digital (A/D) card, and a pump controller. The flow system
includes pressure sensor, fluid reservoir and tubing. The pulse wave
properties can be controlled using the PC by a graphical user interface (GUI).
The flow is measured twice; by the flow sensor and by the physician US
device.
8
As part of the project, a literature review was conducted on the anatomy
and physiology of the UC, DUS, the base flow system and medical
simulations. In order to build a physically compatible prototype with US,
materials properties were researched and compared to a real tissue.
The project book contains design, results and discussion on the results.
The results were achieved by an US physician expert examination and
present a positive conclusion that the system can be used as part of the
training process of the physician. The examinations of the system were
conducted using a US device purchased by Afeka for this and future projects.
The project includes many subjects such as; physiological flow, GUI
programming and electronics. The system will initially be used to simulate flow
with a basic UC model, while more advanced model could be included in
future projects. Due to simplicity of the application model, it can be used not
only for UC vessel but for numerous kinds of vessels with suitable design.
5 IntroductionDuring the training of an ultrasound physician, the intern, or trainee, is
required to conduct an extensive practice with DUS transducer. By a relatively
short period, the interns should encounter a wide variety of cases, which
include an umbilical cord exam. The umbilical cord flow and shape properties
may indicate a fetal distress state, which requires immediate intervention.
Several pathologies are common and can be diagnosed on a daily or even a
weekly basis, but some cases are rarer. Early identification of pathologies that
might risk the fetal or the patient is a matter of practice and familiarization with
the transducer.
As current state training, the interns conduct exam on patients that are
available. Life risking pathologies might not be so common, an immediate
intervention is required, and in many cases will not be delayed for training
purposes. The information about those once-in-awhile cases are usually
passed down by written data or orally, but without any in-hand practice. Due
to lack of practice with the fetal distress cases, many physician refrain from
signing any statements which are related to the fetus health condition. A new
9
method of training might increase the physician knowledge, allowing better
diagnostics.
In this project, a prototype system of a simulator for blood flow
estimation in the umbilical cord for practicing DUS was designed and built.
The project is in the field of mechanism of the physiological flow and includes
a prototype of a system which intent to be used by interns or any trainee and
their instructors in the ultrasound training facility.
The project is a thought product of Prof. Roni Tepper, the head of the
ultrasound unit in Meir hospital. The requirement system was a working unit in
which the instructor could set a certain fetal state which will be represented by
the flow and vessel properties. Some of the settings that will be able to be
controlled are pressure and flow rate.
With the supervision of Dr. Sara Naftali, and the proficient advice of Prof.
Roni Tepper and Dr. Yoav Alpert, this project intent to serve as a training
device and can also be an experimental device for medical engineering (ME)
students and may be used as a platform for further research.
6 Literature review6.1 Anatomy of the umbilical cord
The umbilical cord (UC) [Figure 6.2], also known as Funiculus
Umbilicalis, is the vessel which connects the fetus through the placenta to the
mother blood system. The UC contains 3 vessels; one vein and two arteries.
In the vein flow oxygenated blood towards the fetus, the fetus pumps
deoxygenated blood to the placenta through the arteries. The three sub
vessels are protected by a fluid called Wharton's jelly, the fluid is a gelatinous
substance made largely from mucopolysaccharides [1].
10
Figure 6.2 The UC Anatomy [14]
After week 37 of gestation, the UC length at normal state can range from
50 to 60 cm. a study shown that the whole UC diameter in healthy pregnancy
range from 3.19 ± 0.40 mm at 10 weeks to 16.72 ± 2.57mm at 33-35 weeks,
and decline to 14.42 ± 1.50 at 42 weeks [2]. The decline of diameter is related
to the reduction of water in the Wharton's jelly. The UC vein cross section
area range from 28 mm2 at 24 weeks to 58 mm
2 at 34-38 weeks [3]. The vein
cross section area is approximately 30% larger than both of the combined
arteries.
6.2 Umbilical cord flow physiology
According to their cross section area, the fluid velocity in the vein is
approximately half than in one of the arteries. The velocity in the vein ranges
from 10-22cm2 /s . The umbilical venous pressure increased from 600 Pa at
18 weeks to 800 Pa at term, while the cardiac output (CO) can vary from 200
to 1900 ml /min according to gestation stage [4]. Table 6.1 presents the
Cardiac Output as a function of gestation stage.
11
Table 6.1 Combined cardiac output and distribution in human fetus. (units are mL/min ) [4]
Gestation stage 20 weeks 30 weeks 38 weeksCombined Cardiac Output
210 960 1900
Left Ventricle 47 43 40Right Ventricle 53 57 60Foramen ovale 34 18 19Lungs 13 25 21Ductus arteriosus
40 32 39
6.3 Doppler Ultrasonography
Using the Doppler Effect, a virtual window can created in order to
evaluate the velocity of the particles which transverse it. The Doppler effect is
created by sending a sound wave with a certain frequency, and receiving the
reflected wave. If the frequency of the returning wave is decreased compare
to the sent wave, then the object is receding, and if the frequency is higher the
object is approaching to the source. This affect is applied in DUS device using
transducer as the wave source, and receptor.
The physician, using the US device, can evaluate the flow velocity in a
certain direction within the blood vessel, in this case the UC, and generate a
graph which shows the spontaneous velocity as a function of time. The result
of a Doppler M mode scan of the carotid artery is demonstrated in Figure 6.3,
the image resembles the UC scan. This function helps the physician to
diagnose pathologies that might cause a change in the velocity pulse.
Figure 6.3 Spectral Doppler scan of the carotid artery [5]
12
6.4 Medical simulation
The medical simulation subject is divided into 2 sub-branches;
emergency response and clinical training. For the emergency response the
simulation purpose is help reduce accidents during surgery and field patient
treatment. There are many simulators that can emulate a real patient, for
example, Laerdal's SimMan [Figure 6.4] is a full body simulator that can
breathe, have a pulse, blink, talk, bleed and many more functions.
Figure 6.4 Laerdal's SimMan emergenrcy response training [8]
In case of clinical training, the focus is narrowed down to a specific part
of the body. The environment in this case is more calm and educational but
shares the same purpose as emergency response; reduce accidents. There
are many simulation devices for clinical training and each has its own specific
purpose. For example, Simbionx's Lap Mentor [Figure 6.5], which enables the
physician experience a laparoscopy surgery using a control module to
emulate the surgery tools and a monitor to emulate the scope. Another
example is the Biometric Fetal US Training Phantom by CIRS [Figure 6.6].
The fetal phantom resembles by its anatomy to a real fetus and is fully
compatible with an US device. Though this phantom provides high accuracy,
it is a static only phantom without any flow within it. The Doppler function
cannot be tested on this model.
13
Figure 6.5 Simbionix's Lap Mentor laparoscopy clinical training [9]
Figure 6.6 Biometric Fetal Ultrasound Training Phantom by CIRS [15]
6.5 Base flow system
The flow system is based on an existing experimental system that is
located at the student mechanical physiology laboratory of the ME department
at Afeka College. The system was built as a part of a final project
"Development & Design of Experimental System for Flow Measurements in
Coronary Arteries Models" by Ido Muller [6]. The experimental system
consists of a working flow system with pulsatile pump and graphic user
interface (GUI). It was designed to measure blood flow and pressure in
coronary arteries models. Due to similarity to the requirements of this project,
the current project flow system is based on this system. The system consists
14
of a pump and controller, sensors, A/D card, GUI, fluid reserve, and a
replaceable vessel. The pump is a pulsatile pump, which enables a wide
control on the pulse wave. [Figure 6.7]. The schematic drawing of the system
functionality is presented in Figure 8.8.
Figure 6.7 The experimental system used at the ME laboratory [6]
7 Objectives
7.1 Main Objective
The purpose of the project is to design and develop a prototype system
that will be used as a simulator for blood flow estimation within the UC for
intern practicing DUS. The device will be located at a training medical facility
in Meir hospital. Similar device will be used at Afeka's ME laboratory as an
experimental system.
7.2 Client and users
The device will be used in Meir hospital medical training facility,
Simultech, under the supervision of the client, Professor Roni Tepper. The
instructors of the facility will be the high level users of the system, they will
control the system and maintain it. The low level user of the system will be the
US interns, under the supervision of the instructor. The interns will have
minimal interaction with the device, mainly with the UC model and the US
device provided by the training facility.
15
7.3 Requirements
7.3.1 Client requirements
The following specific requirements were provided by the client:
To mimic an UC in its natural fluid environment
Characteristic physiological flow values such as fluid velocity and
pressure
Pulsatile flow
GUI controlled
A 'readable' flow by an US device with the least ultrasonic artifacts
Generate a pulse wave within the vessel model which resembles an
umbilical pulse wave
7.3.2 Engineering Requirements
Some requirements are required due engineering considerations. The
following requirements were derived for those reasons:
The electrical equipment must fit 220V and 50Hz (Israel electrical
network)
The project budget limitation; if a component is beyond the budget
provided by Afeka, the client must confirm the purchase
Look and feel design is not mandatory since the project is a prototype.
All design requirements are defined as 'nice to have'; hiding the
permanent parts such as tubes wires and so on, and paint on the basin
which will conceal to content
User friendly GUI for an US medical physician/intern
A direction for use (DFU) must be written to elaborate on steps the
instructor needs to do before, during and after the exam. A
maintenance section will be added as well
A flow sensor that indicates the instructor the current pulse wave shape
and properties for comparison
An easy vessel replacement procedure due to deterioration and simple
switch between vessel geometries
An US compatible materials that can transfer sound wave with the least
wave unneeded reflection possible
16
8 MethodThe system is compiled of 3 sections; application model, GUI and flow
system as illustrate in Figure 8.8, and fully built in Figure 8.9. The PC, using
the data provided in the GUI, sends a digital signal to the D/A card which
translated as an analog signal to the pump via pump controller. The fluid from
the reservoir flows through the pump into the application model whereafter it
is being measure in the Venturi flow meter, and finally injected back to the
fluid reservoir. The flow through the application model is detected by the US
device and presented on its monitor. The Venturi flow sensor sends an analog
signal to the A/D card, to be translated to a digital signal, processed and
presented on the GUI by the PC.
Figure 8.8 Illustration of the system and its components
17
Figure 8.9 The system and its components
8.1 The Flow System
The system is based on an existing system that fits this project purpose.
A full review of the system will not be included in this project but rather a
description of it. The description was derived from Ido Muller project book [6].
8.1.1 Pump controller and power supply
The pump controller and power supply were planned by Dr. Uri Zaretsky,
and can be seen in Figure 8.10. The power supply provides the pump with up
to 5V and the controller enables the pump to be either controlled by an
external signal (the A\D card) or internally with a current knob on the
controller. Table 8.2 Pump controller functionality presents all the function on
the controller and their description.
18
Figure 8.10 Pump controller and power supply
Table 8.2 Pump controller functionality
Function DescriptionOn/Off Toggle button for the power supply to the controllerExt/Int Toggle button for internal or external controlCurrent Controls internal current provided18V Input voltage for the power supplyMotor Output voltage for the pumpD.A in Input for external control
8.1.2 A\D card
The A\D card used for this system was the National Instrument USB-
6009, Figure 8.11. The card is used to connect the PC to the pump controller
and the Venturi sensor. A full electrical drawing of the card circuit is described
in Appendix 14.1.
19
Figure 8.11 National instrument USB-6009
8.1.3 Venturi sensor
The sensor is an assembly of 2 elements, the deferential sensor (Figure
8.12) and the Venturi tube (Figure 8.13). The fluid transvers the tube while the
upstream and downstream pressure taps are measured with the deferential
sensor. A full drawing description of the Venturi tube can be seen in Appendix
14.2.
Figure 8.12 Electronic differential sensor
20
Figure 8.13 Venturi tube
8.1.4 Pump
The pump (Figure 8.14) in the flow system is a miniature gear pump
2.52L/min. The specification can be seen in Appendix 14.3.
Figure 8.14 Gear pump
8.1.5 Fluid reservoir
The Fluid reservoir (Figure 8.15) used is a simple water container and lid
with holes to insert the tubes.
21
Figure 8.15 Water reservoir
8.2 The GUI
The GUI was programmed in LabView 2010 and redesigned in this
project to allow the user (i.e. instructor) to set the flow with the settings he or
she requires and convert them to a signal sent to the pump, the GUI output.
The GUI also acquires from the system via A/D card, the flow rate as detected
by the Venturi differential sensor. The GUI interface and functionality are
reviewed in this section. The LabView files were added in the project disk.
8.2.1 GUI interface
The GUI interface comprises with controls and display as follows (Figure
8.16):
Figure 8.16 The GUI interface
22
Umax – The max volt sent to the A/D card and eventually to the
pump, function as systolic value.
Umin – The min volt sent to the A/D card and eventually to the
pump, function as diastolic value
BPM – pump's beat per minute
Duty cycle – the signal Umax percentage of the pump
Enable – turns the pump on and off
Clear graphs – reset the graphs on the right display
Flow signal –the Venturi sensor detected flow display
Volt output – the output signal sent to the A/D card and eventually
to the pump display
Flow zero –zero level calibration for the Venturi flow sensor.
Lower cut-off – High pass filter of the output volt signal
Stop D/A – disconnects the signal sent to the pump and shuts
down the program
8.2.2 GUI Functions
In order to examine each of the GUI function, a comparison of the
function was made to show effective difference. Each of the user-defined
values for the sent wave was tested separately and the end results were
compared to the same basic values. The end results were examined by the
flow sensor, though a thorough examination to indicate functionality of each
value should be conducted with an US Doppler.
Table 8.3 contains the parameters and their end results, while the first
row represents the basic values to compare the rest to. For example, the
second row describes a decrease of Umax to 2.5V from the basic value of 5V
(as presented in the first row, marked in red). The two graphs in the 2nd row
present the end result of the decreased Umax parameter. These graphs were
compared with the basic parameters in the 1st row. In this example, the
maximal flow of 400 ml/min as shown in the 1st row, decreased to maximal
flow of 200 ml/min as shown in the 2nd row.
23
Table 8.3 GUI function comparison
Parameter Value Flow graph [mL/min] Volt Graph [V]Basic values
Umin=0 VUmax=5 VDuty cycle=20%BPM=70Lower cut-off=10
Umax [V] decreased to 2.5 V
Umin [V] increased to 1.5 V
24
Time [sec]
Time [sec]
Time [sec]
Time [sec]
Time [sec]
Time [sec]
Parameter Value Flow graph [mL/min] Volt Graph [V]Duty cycle increased to
40%
BPM increased to 150 BPM
Lower cut-off
decreased to 3
25
Time [sec]
Time [sec]
Time [sec]
Time [sec]
Time [sec]
Time [sec]
8.2.3 GUI Functions Results explanation
All parameters changes show a significant effect on the appropriate graph. The
test leads to the conclusion that all function are working correctly. Table 8.4
summaries the results comparison.
Table 8.4 GUI function comparison numeric results
ParameterBasic
value
New
valueFlow change Volt change
Umax [V] 5 2.5 Max flow decreased
from 400 to 200
mL/min, A 50%
decrease
Max volt was
decreased from 5 to 2.5
V as expected
Umin [V] 0 1.5 Min flow increased
from 50 to 250 mL/h, a
500% increase
min volt was increased
from 0 to 1.5 V as
expected
Duty cycle 20% 40% Systolic section was
increased from about
0.15 seconds to 0.33
seconds. Almost twice,
like the duty cycle
increase
Systolic section was
increased from about
0.15 seconds to 0.33
seconds. Almost twice,
like the duty cycle
increase
BPM 70 150 5.5 pulses were able to
fit in a 5 seconds
interval in the basic
parameter, while in the
tested, almost 13 were
fitted.
5.5 pulses were able to
fit in a 5 seconds
interval in the basic
parameter, while in the
tested, almost 13 were
fitted.
Lower cut-
off
10 3 No significant changes
occurred
The pulse shape is
significantly round
compared to the basic
value
26
8.3 The Application Model
The model container is made from Perspex material and is divided into two
parts; a fluid container and a lid. The lid is a frame to hold a latex sheet that will
mimic the human skin and the US transducer will be applied on top of it.
The container and lid were designed using Solidworks software. The model
was eventually sent to a manufacturer using a standard three sided and isometric
view of the both of the designs.
The final prototype of the application model with the UC model is presented in
Figure 8.17. In this figure the assembly of container and lid, red latex sheet, leak-
proof connectors, the vessel and the green sponge material to absorb the sonic
waves are presented
Figure 8.17 The final prototype of the application model with the UC model
The model features were calculated to ensure a fully developed laminar flow in
8.3.1, and design to ensure maximal US compatibility in 8.3.2.
8.3.1 Model Calculations
The Reynolds number was calculated in order to estimate if the flow was
laminar or turbulent. The general Reynolds number equation is described in
Equation 8.1.
(8.1) Re=
Q eff⋅Dυ⋅A
27
Where Re is the Reynolds number, Qeff is the effective flow rate, D is the
characteristic linear dimension, υ is the kinematic viscosity of the fluid and A is the
vessel cross section area. Each of the parameters was calculated separately.
The effective flow rate was calculated with the estimation of 33% duty cycle;
33% of the time the pump will be activated on maximal power while the other 67%
was estimated to be with no power at all. The maximal value of the taken flow was
the maximal value as described in the pump specification (Appendix 14.3).
(8.2) Qeff =
Qmax3
+2Qmin3
Qmax=2520mLmin
=2520⋅(10−2 )3
60m3
sec=4 .2⋅10−5m
3
secQmax=0
Qeff=4 .2⋅10−5 /3=1. 4⋅10−5 m
3
secFor the characteristic linear dimension D, the tube diameter was chosen. The
estimated tube diameter that was used is the diameter of the holes that were drilled
in the side of the container where the vessel transverse as described in Equation
8.3.
(8.3) D= 0.01m
The kinematic viscosity of the fluid υ , was estimated to be resembling to blood,
since there is a chance in future project that a fluid with similar properties will be
used. Equation 8.4 describes this value with its units.
(8.4) υ= 3⋅10−6 m
2
sec
The cross section of the tubeA , is based on the tube diameter D as described
before in Equation 8.3, while Equation 8.5 describes the cross section area.
(8.5) A=πD
2
4= π⋅0 .01
2
4=7 .854⋅10−5 m2
All the calculated parameters in Equations 8.2-8.5 were integrated within
Equation 8.1 as follows in Equation 8.6.
28
(8.6) Re=
Q eff⋅Dυ⋅A
= 1.4⋅10−5⋅0 .013⋅10−6⋅7 .854⋅10−5
=594 .1<2000
The Reynolds number is smaller than 2000, thus, the flow is laminar. In this
case 10 diameters will suffice. Equation 8.7 presents the final length that ensures a
fully developed laminar pulse wave.
(8.7) Le≈10⋅D=10⋅0 .01=0.1 m<0 .3 m
8.3.2 Model Design
A detailed drawing of the container can be seen in Figure 8.18, and fully built in
Figure 8.19.
The container internal dimensions are:
Width – 20cm
Height – 24cm
Depth – 30cm
The width and height allows enough area for the US device while the length
ensures a fully developed laminar pulse wave. The velocity profile develops fully and
remains unchanged after some distance from the inlet (about 10 pipe diameters in
turbulent flow, and less in laminar pipe flow) [11]. The walls of the container are 1cm
thick.
The container was designed using SolidWorks software. The model was
eventually sent to a manufacturer using a standard three sided and isometric view of
the design. The final design as sent to the manufacturer is presented in Figure 8.19.
Figure 8.18 describes a standard three sided and isometric views of the
SolidWorks design. On the front side of the container, two holes are visible; 'A' and
'B'. Both holes are 1cm in diameter, a silicone tube is fitted and cemented to the
holes and to these tube the vessel is connected. Hole 'A' transverse the container
and through it the vessel enters and exits the container. The hole is located 15cm
high from the floor to make sure there is enough medium for an US image
requirements. The customer requirement was 5 cm distance from the top and
29
another 5 at lease from the bottom, another 5 cm were added to be on the safe side.
Hole 'B' function as drainage in case the water will reach overflow.
Figure 8.18 Perspex lid, standard 3 views with isometric view, all units are in meters
Figure 8.19 The final container with the vessel, connenctors and and sponge like material
30
8.3.3 The Lid
The lid is placed on top of the container and function as a frame for a latex
sheet. The area in which the transducer can be applied is 15X25 cm2. Figure 8.20
presents a three sided and isometric views of the lid as designed in Solidworks and
sent to the manufacturer. The fully built lid is presented in Figure 8.21.
Figure 8.20 Perspex lid, standard 3 views with isometric view, units are in meters
Figure 8.21 The final lid with latex sheet
8.3.4 Assembly
Figure 8.22 represents the box and lid assembly by a standard three sided and
isometric view, as designed in SolidWorks and sent to the manufacturer. Figure 8.17
presents the final assembly of the whole application model.
31
Figure 8.22 Box and lid assembly, units are in [cm]
8.3.5 Water drainage
During the US examination some force applies on the surface area. In this
model, the surface area is made of latex and it in contact with the top of the water. It
is expected that the water level will rise from the sides of the lid when pressed (as
seen in Figure 8.23), then, when the released the water level should return back. A
range of water volume is required to ensure enough water can remain in the lid sides
for a normal water return. The extra water can drain from hole 'B' as seen in Figure
8.18. The bottom of the hole is located 1.5 cm from the top of the tank, while the
bottom of the lid is 4 cm from the top. The lid is designed to be 0.5 cm from each
side of the tank. The box top inner area is 30X20 cm2.
The following (Equation 8.8) calculates the total volume of water which can
remain after drainage between the lid sides and the box.
(8.8) V=H⋅{2⋅D⋅L1+2⋅D⋅(L2−1)}=H⋅{2DL1+2DL2−2D}
⇒ V=2DH {L1+L2−1}
32
Where, V is the remaining volume, H is the height between the bottom of the
lid and the bottom of hole 'B', D is the distance between the lid and box walls, andL1
,L2 are the box walls length. Thus,
V=2⋅0 .5cm⋅(4−1 .5 )cm⋅{30+20−1}cm=127 .5cm3
Figure 8.23 Water overflow control
8.3.6 Model Modifications
Some minor modifications were added to the application model after the
SolidWorks design that were necessary while building the model:
Holes A and B in Figure 8.18 were dilated to 1/2 inch (or 1.27 cm) diameter.
The new diameter allows inserting a leak-proof coupler [Figure 8.24] in the
middle and connecting tubes directly to it instead of using a 1 cm outer
diameter silicone tube with 2 coupler connected in each end.
Figure 8.24 Leak-proof coupler
33
All adhesive application were conducted in 2 stage; first adhesion with quick
dry glue for fixation and a second adhesion with epoxy cement to prevent
leakage
A sponge like, plastic material layers were added into the bottom of the
container. The material, along with air bubble that were trapped within it,
provided a sonic filter for sonic waves that were emitted from the transducer
and reflected by the Perspex bottom, i.e. US artifacts.
8.3.7 US Compatibility
As required, the application model needs to be compatible with the least sonic
artifacts. In order to answer this requirement, several layers of sonic wave mediator
were placed. These layers are described in the order as the sonic wave encounter:
1. A thin layer of 1mm Latex sheet: The latex was selected due to its high
flexibility and durability while being stretched. Since the sheet is only 1mm the
sonic wave can transverse it with very minimal interference
2. Water: Water is the main mediator in model due to low maintenance and
resemblance to amniotic fluid, both of which are mainly composed of water.
3. Latex tube with a 0.5mm thin wall, and 7mm inner diameter: As the latex
sheet, this tube allows minimal power reduction of the sonic wave due to its
very thin wall.
4. A sponge like, plastic material layers at the bottom of the container: The
material, along with air bubble that were trapped within it, provided a sonic
filter for sonic waves that were emitted from the transducer and reflected by
the Perspex bottom, i.e. US artifacts.
8.4 The US device
The testing of the system was conducted with a GE Healthcare Logiq C5
Premium [Figure 8.25]. The device is a portable ultrasound system with 3D and 4D
functionality suited for hospitals covering various requirements such as general
imaging, obstetrics and gynecology, and cardiovascular applications.
34
Figure 8.25 GE Logiq C5 Premium
9 Results9.1 Physician Examination
In order to examine whether the system is capable to simulate efficiently an UC
blood flow, a physician specializing in US examination conducted a review. The
physician tested the device was Dr. Abraham Agranat, from Laniado hospital, using
Afeka's Logiq C5. The system compatibility with the US and USD tests were
examined. The system parameters were set during the whole exam to the same
values, as described in Figure 9.26 and in Table 9.5.
Figure 9.26 The system values for the physician review
Table 9.5 The system values for the physician review
Parameter
Umax Umin BPM Duty cycle Lower cut-off
35
Value 5 [V] 2 [V] 100 30% 10
The first examination is to check the vessel compatibility with the US and any
sonic artifact that might occur. The exam resulted with a clean image of the vessel
[Figure 9.27] without any artifacts. A video of the exam was recorded (link to video:
https://youtu.be/zEZB9aAf498) as well to show the pulsatility as it displayed at the
US device monitor, the fluid movement can be seen as well. On a later examination
a Doppler spectrography was added to the image [Figure 9.28] to present the fluid
velocity. The Velocity is also presented in graph below the image where the pulse
wave is clearly identifiable. A video of the Doppler addition was recorded as well (link
to video: https://youtu.be/brBYPSaJ9Cw), though the velocity graph was not
recorded due to device limitations. In the video, the pulse direction is distinguishable
though a higher frame rate would emphasize it even more.
Figure 9.27 US image of the vessel
36
Figure 9.28 US Doppler spectrography of the vessel
10 Discussion10.1 Comparison to Physiological Data
The pulse wave from the model was compared to a physiological pulse wave of
a real umbilical cord [Figure 10.29]. The comparison reveals high resemblance
though many differences as well. The data was analyzed visually due to two main
reasons; during practice the data will only be analyzed visually as well, and the
manner of data transfer between the US and a PC (i.e. using simple monitor
screenshot versus Digital Imaging and Communication in Medicine – DICOM); The
data derived from the US device currently is a low resolution image as seen on the
US monitor while the data transferred using DICOM is raw numeric data that can
analyzed using Matlab or other data processing software. During visual inspection of
the model waveform one can discover two main differences from the UC waveform;
the model waveform is not smooth and the values are almost twice as much as the
physiological value, the model velocity reaches 100 cm/s while a real UC rarely pass
the 50 cm/s mark. Equation 10.1 present Reynolds number calculation, assuming
both the literature example and the model are at the same of 0.61 cm, which is within
the normal UC diameter values [2]. Figure 10.31 presents a measurement of the
tube diameter with the US device measurement tool. In the tube, water is used while
37
in the literature example blood is being used. The velocity calculated was used as an
average between minimum velocity and the maximum.
(10.1) Re=VD
ν
Where Re - Reynolds number, V-mean flow velocity and ν is the kinematic
viscosity of the fluid.
Model UC Reynolds:ReModel=
VDν
=0 .75⋅0 .00618 .9⋅10−4
=5.14
Real UC Reynolds:ReReal=
VDν
=0 .25⋅0 .00613⋅10−3
=0 .508
Though the difference between the two Reynolds numbers is tenfold, mainly
due to the fluid viscosity, both numbers are significantly low and provide proof that
the flow is laminar.
The lack of smoothness of the waveform is caused by many factors; rigid
artifacts (such as connectors, walls etc.), movement of the vessel in the water,
reflected waves etc.
Figure 10.29 The model velocity waveform
38
Figure 10.30 A real UC velocity waveform [12]
Figure 10.31 Model diameter measurement taken with the US tools
Figure 10.32 is a screen shot taken from the video that was mentioned in 9.1, in
this image we can see a clear pulse wave fully formed in the tube. The wave acts as
expected with a parabolic shape with no slip conditions at the vessel walls. When
compare to an US examination [Figure 10.33], beyond the model vessel there is
some movement while in a real no movement be seen outside of the vessel. The
model vessel is 'hanging' in water with minor support, unlike a real vessel which has
support from the environment that surround it, along with high pressure. The
movement of the model vessel creates a secondary reading outside of it.
39
Figure 10.32 Screenshot taken from the US Doppler spectrography of the simulator video (https://youtu.be/brBYPSaJ9Cw)
Figure 10.33 Screenshot taken from Introduction to Doppler Ultrasound [13]
10.2 Physician Review
In order to estimate whether this project has achieved the goal that were initially
set, the end result must be efficient for the physician to conduct training. The
physician review this project agreed that the project is indeed efficient and can be
used for medical training. The physician added that in his current facility, Laniado
Hospital, there are not many physicians that conduct Doppler examination due to the
complexity of the process. Integrating this system with the regular physician US
training might increase the number of physician that can conduct the examination
and increase the efficiency of the exam itself.
The expert also added that the image extracted from the model, in terms of
Doppler color, is not as smooth as he would expect (see Figure 10.32 in comparison
to Figure 10.33). He suggested that this effect might be caused due to the fluid type
40
in the vessel; water. If the fluid that traverses the vessel might be similar to blood,
then the image could be much smoother.
11 ConclusionIn order to effectively improve the of DUS training for physicians, a destined
simulator with pulsatile UC model was required. In this project the system was built
and answered all the customer requirements; pulsatile, GUI controlled and US
compatible system. Before the system will ready to be duplicated and implemented
at Meir Hospital for medical training, a full set of calibration is required to be applied
to make sure the values presented by the GUI are accurate. The images extracted
from the model, to the client opinion, are not complete, replacing the fluid type to
simulate blood properties might improve the results quality.
The simple design, as described in the project process [14.4], and materials
that were used in the model affect the versatility of the model; the vessel can be
changed easily and the system can be used for a different type of DUS examination.
Due to the model high versatility, it can be used for many purposes such as a
medical lab in Afeka for ME students. Directions for Use (DFU) were written to
ensure correct use of the system [14.5].
The system was examined by an US physician in order evaluate the device
efficacy during training, whether it can help improve it. To the expert opinion, this
device can help the trainee practice the US device and learn how to operate it before
examine a patient. The pulsatile flow capability allows a Doppler examination which
usually can only be practiced on a live patient.
In conclusion, the project can mimic an UC in its natural environment, and may
help improve the physician training allowing a better US Doppler examination in
practice.
12 Suggestion for Future Research12.1 Finalizing the System
There is a lot of work remaining to perfect the system to fit the exact need of
the trainer, though this system is a solid baseline that is capable to yield results as
well. In terms of esthetics, the system might not be good looking, but if duplicated
41
and built from scratch to fit Meir Hospital, it would be suggested to redesign the
electronics to fit into a single box (i.e. the pump controller and A/D card). The GUI
can be redesigned as well; additions of functionality for ease of use and design it to
be more user-friendly. Furthermore, it is recommended to use a fluid with similar
properties to blood, such as glycerin-water solution with sodium chloride to simulate
blood cell, or other types of fluids. The more viscous solution can help generate a
better image from the model.
12.2 The Experimental System for the Medical Lab
As mentioned in 7.1, one of the objectives of the project is to be used as an
experimental system in Afeka's medial lab. The system, in its current state, is a
prototype and should be considered as a baseline for future projects. In order to
convert it to a lab, a protocol must be composed. The protocol should explain about
the whole system and set objectives that should be studied. Some objectives should
include; experience with the US device function, measure and compare US results to
other methods of measurements, the effect of different tube materials on the US
reading, etc.
12.3 Application model modification
Due to lack of time and budget, some aspects of the model were left out to be
implemented after the system is work in the basic mode and can be execute in the
future. The current vessel model is linear, far different from a real UC. A coiled, three
ways tube is highly recommended; one line upstream and two downstream. The new
vessel should highly resemble an UC, and can further help with the simulation of the
original objective of this project. A new tubing system must be design to support
within the container in order to support the three lined tube.
Another modification that was mentioned in the meetings with the client is a
backflow pump. In some case, the flow in the UC can be reversed, this case is highly
dangerous for the fetus and require immediate intervention. It is recommended to
achieve this feature to add a pump that will push the flow against the main pump. Of
course this will require another tube to bypass the secondary pump. It is reasonable
to think that if the secondary pump will be on a continuous flow, a backflow might be
seen between the intervals of the main pump.
42
12.4 Ultrasound and flow field correlation
A new project is now suggested to be based on the system; "Ultrasound and
flow field correlation of an embryonic cord model". The purpose of the project is to
analyze the correlation between a computational fluid dynamics (CFD) data in a 3D
UC model and the vessel flow within the application as examined with the US device
13 References1. Spurway J, Logan P and Pak S. The development, structure and blood
flow within the umbilical cord with particular reference to the venous system. AJUM. 2012 15 (3).
2. Naro Di E, Ghezzi F, Raio L, Franchi M, and D’Addario V. Umbilical cord morphology and pregnancy outcome. Eur J Obstet Gynecol Reprod Biol 2001; 96 (2): 150–57.
3. Li WC, Ruan XZ, Zhang HM, and Zeng YJ. Biomechanical properties of different segments of human umbilical cord vein and its value for clinical application. J Biomed Mater Res B Appl Biomater 2006; 76B: 93–7.
4. Kiserud T. Physiology of fetal circulation. Semin Fetal Neonatal Med 2005; 10: 493–503.
5. Medical ultrasonography, Wikipedia, http://en.wikipedia.org/wiki/Medical_ultrasonography. last modified on September 4th, 2014
6. Muller I., Zaretsky U and Naftali S. Development & Design of Experimental System for Flow Measurements in Coronary Arteries Models. Final project book, Department of ME, Afeka College 05/2011.
7. Callen P.W. Ultrasonography in obstetrics and gynecology 5'Th edition. Sounder Elsevier 2008.
8. Laerdal, SimMan 3G http://www.laerdal.com/SimMan3G. Last entry on September 16th, 2014.
9. Simbionix, Lap Mentor http://simbionix.com/simulators/lap-mentor. Last entry on September 16th, 2014.
10. Methodology of Doppler assessment of the placental & fetal circulation Sonoworld.com, http://sonoworld.com/Client/Fetus/html/doppler/capitulos-html/chapter_03.htm Last entry on December 27th, 2014.
11. Çengel Y. A., Cimbala J. M. Fluid Mechanics: Fundamentals and Applications (1st ed.) Boston: McGraw-Hill Higher Education 2006
12. Maulik D, Yarlagadda P, Downing G. Doppler Velocimetry in Obstetrics. Obstet Gynecol Clin North Am 1990;17:163–86
13. Introduction to Doppler Ultrasound, https://youtu.be/tQn8jKtwk6o, Ultrasound Institute at the University Of South Carolina School Of Medicine. YouTube, Last entry on May 8th, 2014.
14. Umbilical Cord Anatomy , http://imgkid.com/umbilical-cord-anatomy.shtml, Last entry on May 11th, 2015.
15. Biometric Fetal Ultrasound Training Phantom, http://www.cirsinc.com/products/all/88/fetal-ultrasound-biometrics-
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phantom/, Computerized Imaging Reference Systems, Inc. Last entry on May 11th, 2015.
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14 Appendix14.1 National Instrument USB-6009 Electrical drawing
45
14.2 Venturi tube drawing
46
14.3 Gear pump specificationsThe pump chosen in system is the miniature gear pump model No.EW-07012-
20 by Cole-Parmer. The following image present the specifications of the pump.
47
14.4 Project ProcessThe construction of the model was made easy due to careful designing. The
SolidWorks drawing were sent to a Perspex manufacturer and was constructed in
less than a week. After the model was complete a rather long process initiated; small
parts were glued together one part at a time to make sure everything is sealed tight
with no leakage. Initially the Latex sheet was attached using both super glue
adhesive and epoxy cement, the first is to create a fusion between the materials
while the other is used to prevent leaks.
Finding the correct tubes for the project proved to be a difficult task. There are
many types and sizes of tubes, but those that were needed for the project are not a
standard in market. The initial design for the vessel connection was a tube traversing
the container with 2 leak-proof connector in each side. The inner connecter where
then connected to the vessel while the outer ones were connected to the flow
system. Due to the shape of the connectors [Figure 8.24] a more elegant solution
was suggested; inserting the connector to the Perspex drill and using and reducing
the total number of connector to two instead of four. The fitting of the connecter
required widening the original drills, this was done in Afeka's workshop. The
connectors were then glued as well with both layers of super glue adhesive and
epoxy cement.
The integration of the model with the flow system was first seemed to be a
major issue; since the system is currently being used as a medical lab every year, a
new system must be built to support the model. An elegant solution was brought up
to disconnect the tubing in the system at a strategic location and insert leak-proof
connectors [Figure 8.24] that will lead water through the model. This quick fix
prevents any addition costs while maintain the project fully function without affecting
the medical lab.
48
14.5 Direction for Use (DFU)1. Overview
The Dynamic Simulator Model was developed and designed to simulate a flow within blood vessels of various types. The model was made compatible with the ultrasound (US) device in order to minimize sonic artifact that might occur.
2. Equipmenta. Flow system
The flow system is compiled from an A/D card, pump power supply, pump, fluid container and a Venturi flow sensor. The A/D converts the digital signal from the PC to the pump via power supply. The Venturi flow sensor send a signal of the flow through the A/D to the PC.
b. Application model The model allows a compatible window to the vessel within it for an US transducer
c. GUI Allows the user to control the flow properties that will be sent to the pump.
49
d. GE's Logiq C5 Premium US device
3. MethodIf the application model is currently connected to the system, start from step C.
a. Empty the flow system b. Replace the tube on the flow system and connect the application model
instead.c. In the application model, connect the blood vessel. Make sure it is
tightly connected, soft tube might need to be secured with cuffs.d. Place the model at the correct position. After this step the model will be
too heavy to be moved around.e. Fill the container with water all the up to the drainage. (it is
recommended to place a bottle at the end of the drainage to collect excess water)
f. Place the lid on top. Air bubble might be trapped underneath the latex, apply mild pressure with your hand to remove it. Note that some water can be extracted from the drainage.
g. Make sure the 'Current' knob on the pump controller is on 0 (turn counter-clockwise all the way).
h. Make sure the source switch is set to 'INT'.i. Turn the pump controller ON.j. Slowly increase the controller current to remove air from the system.
When all air is removed, switch the current back to 0.k. Open the GUI.l. Switch the source on the pump controller to 'EXT'. The pump is now
being controlled by the GUI.m. Turn the US device ONn. Select the appropriate probe and preset settings using the 'PROBE"
button.o. Apply small amount of water on the model latex and place the US
transducer.
50
