Download Related Topics Pulse duration (DT), heart rate, end systolic diameter

Ultrasonic Time Motion Mode
TEAS
9.5.02
-00
)
Related Topics
Pulse duration (DT), heart rate, end systolic diameter (ESD), end systolic volume (ESV), cardiac output
(CO), heart wall motion, echocardiography, Time-Motion-Mode, representation of motion sequences, ultrasonic echography.
Principle
Using a simple heart model, the wall motion is recorded with ultrasonic time-motion method (M-mode or
also TM-mode). The heart rate and the cardiac output (CO) are determined from the recorded TM-mode
curve.
Equipment
1
1
1
1
1
Basic Set Ultrasonic echoscope
consisting of:
1x Ultrasonic echoscope
1x Ultrasonic probe 1 MHz
1x Ultrasonic probe 2 MHz
1x Ultrasonic test block
1x Ultrasonic cylinder set
1x Ultrasonic test plates
1x Ultrasonic gel
Extension set: medical ultrasonic diagnostics
consisting of:
1x simplified heart dummy for echocardiography
1x breast dummy
1x eye dummy
Recommended accessories
Support base variable
Support rod, stainless steel, 500 mm
Boss head
Universal clamp
1
Additionally needed
PC with USB port, Windows XP or higher
1
13921-99
13921-04
02001-00
02032-00
02043-00
37718-00
Caution!
This is not medical equipment, don’t apply to human body. Pay attention to the special operation and
safety instructions included in the user manual of the ultrasonic echoscope.
Fig. 1:
Equipment for Ultrasonic time motion mode measurements.
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Ultrasonic Time Motion Mode
Tasks
1. Simulate with heart model, the cardiac wall motion and record a time-motion-image.
2. On basis of the time-motion image, determine the cardiac output and heart rate parameters.
Set-up and Procedure
The heart model simulates the wall movement of a beating heart. The model is composed of 2 containers separated with a membrane. The lower container is closed and connected to a rubber ball blower.
The upper container is filled up with water. Compressing the rubber ball, the air pressure in the lower
container increases and centre of the membrane is displaced upwards. This movement is similar to the
heart wall displacement and can be recorded in function of time in a time motion image.
Fill up the heart model with water, until the level reaches a high 2-3 cm beneath the upper edge of
the container.
Connect the 2 MHz probe to the “Probe (Reflection)” plug.
Switch the selection knob to “Reflection”.
Select medium gain and output power.
Switch on the echoscope
Start up the measure Ultra Echo software in A-scan mode. Set the software parameters "sound
speed" to 1480 m / s (Sound velocity of water). Now, the unit of the x-axis can be switched from
"Time" to "Depth". Note: You can measure the x-axis also in time units (µs), in this case you must
perform the conversion in the evaluation step (see ESD).
Place the probe in the water, so that the probe is in contact with the water level in the lower position
and adjust the water level to avoid an overflow in the high position of the membrane. In the A-scan a
clear separation between the surface peak and the membrane reflection peak must be given in all
possible membrane positions. We recommend fixing the probe with a tripod and universal clamp in a
defined position, so that the geometry is fixed during the whole measurement. It is important to place
the probe in the centre of the "heart vessel model ", otherwise the ultrasound waves could be
reflected on the lateral walls on the vessel, which can lead to multiple reflections and blurred
images.
Adjust the transmitter and receiver amplifier settings until the peak of the membrane echo covers the
whole amplitude range in membrane high position, so that no signals are overdriven. Due to the low
damping of ultrasound in water, the TGC (Time Gain Control) can be switched off.
Start the measurement and periodically squeezes the rubber ball to induce a movement of the
rubber membrane, which simulates the heart wall motion. Depending on compression frequency of
the rubber ball, slow or rapid pulse sequences can be simulated. Record two different TM-mode
images with a slow and a rapid sequence.
To optimise the image quality, switch to gray scale and adjust „colour“ range. You can also adjust
the „zoom area“ range to „expand“ the curves.
Software
The measure Ultra Echo software records, displays and evaluates the data transferred from the echoscope. After starting the program the measure mode is active and the main screen “A-Scan mode” is
open. All actions and evaluations can be selected and started in this window.
The main screen shows in the upper part the A-scan signal, the frequency of the connected transducer,
the mode (reflection/ transmission). Actual positions of cursors (red and green line) are displayed at the
bottom of the window. The cursors can be positioned by mouse click. The time of flight is displayed under the cursor buttons. Starting from this main screen, you can select B-mode, TM-mode and CT-mode
screens.
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Ultrasonic Time Motion Mode
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Note
Do not fill the heart model with aggressive liquids. If the membrane is damaged it can be easily changed.
Screw off the cover, the sealing ring must stay in the blue cover ring. Take off the round plastic insert
and remove the old rubber membrane. Stretch the new membrane over the plastic insert. Manipulate the
rubber membrane with caution, as smooth as possible without damaging it. Pay attention to your fingernails! Roll the rubber membrane back to leave the air inlet free. Place the plastic insert with the membrane on the basic vessel, screw on the cover with the sealing ring.
Theory and Evaluation
Echocardiography is used to diagnose cardiovascular diseases. In fact, it is one of the most widely used
diagnostic tests for heart disease. It can provide a wealth of helpful information, including the size and
shape of the heart, its pumping capacity and the location and extent of any damage to its tissues. It is
especially useful for assessing diseases of the heart valves. It not only allows doctors to evaluate the
heart valves, but it can detect abnormalities in the pattern of blood flow, such as the backward flow of
blood through partly closed heart valves, known as regurgitation. By assessing the motion of the heart
wall, echocardiography can help detect the presence and assess the severity of coronary artery disease,
as well as help determine whether any chest pain is related to heart disease. The biggest advantage to
echocardiography is that it is noninvasive (doesn't involve breaking the skin or entering body cavities)
and has no known risks or side effects.
Cardiac output (Q) is the volume of blood being pumped by the heart, in particular by a ventricle in a minute. This is measured in dm3/min (1 dm3 equals 1000 cm3 or 1 litre). An average cardiac output would
be 5 L/min for a human male and 4.5 L/min for a female.
The function of the heart is to transport the blood to deliver oxygen, nutrients and chemicals to the cells
of the body to ensure their survival and proper function and to remove the cellular wastes. Q indicates
how well the heart is performing this function. Q is regulated principally by the demand for oxygen by the
cells of the body. If the cells are working hard, with a high metabolic oxygen demand then the Q is raised
to increase the supply of oxygen to the cells, while at rest when the cellular demand is low, the Q is said
to be baseline. Q is regulated not only by the heart as it pumps, but also by the function of the vessels of
the body as they actively relax and contract thereby increasing and decreasing the resistance to flow.
When Q increases in a healthy but untrained individual, most of the increase can be attributed to an increase in heart rate (HR). Change of posture, increased sympathetic nervous system activity, and decreased parasympathetic nervous system activity can also increase cardiac output. HR can vary by a
factor of approximately 3, between 60 and 180 beats per minute, while stroke volume (SV) can vary between 70 and 120 ml, a factor of only 1.7.
A parameter related to SV is Ejection Fraction (EF). EF is the fraction of blood ejected by the Left Ventricle (LV) during the contraction or ejection phase of the cardiac cycle or Systole. Prior to the start of Systole, the LV is filled with blood to the capacity known as End Diastolic Volume (EDV) during the filling
phase or diastole. During Systole, the LV contracts and ejects blood until it reaches its minimum capacity
known as End Systolic Volume (ESV), it does not empty completely. Clearly the EF is dependent on the
ventricular EDV which may vary with ventricular disease associated with ventricular dilatation. Even with
LV dilatation and impaired contraction the Q may remain constant due to an increase in EDV.
Stroke Volume (SV)  ESV - EDV
 SV 
Ejection Fraction (EF)  
  100%
 EDV 
Cardiac Output (Q)  SV  HR

Q
Cardiac Index (CI)  
 Body Surface Area (BSA)
  SV  HR 
  

  BSA 
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Ultrasonic Time Motion Mode
HR is Heart Rate, expressed as BPM (Beats per Minute)
BSA is Body Surface Area in square metres.
Diseases of the cardiovascular system are often associated with changes in Q, particularly the pandemic
diseases of hypertension and heart failure. Cardiovascular disease can be associated with increased Q
as occurs during infection and sepsis, or decreased Q, as in cardiomyopathy and heart failure. The ability to accurately measure Q is important in clinical medicine as it provides for improved diagnosis of abnormalities, and can be used to guide appropriate management. Q measurement, if it were accurate and
non-invasive, would be adopted as part of every clinical examination from general observations to the intensive care ward, and would be as common as simple blood pressure measurements are now. Such
practice, if it were adopted, may revolutionise the treatment of many cardiovascular diseases including
hypertension and heart failure. This is the reason why Q measurement is now an important research and
clinical focus in cardiovascular medicine.
Fig. 2:
Screenshots TM-mode, slow heart (pump) rate.
Results
The figures 2 and 3 show TM-mode images recorded on the hard model with a low heart rate and a
higher heart rate. The values represented in these two figures are transferred in table 1 and 2. The values are determined by placing the mouse cursor to a specific position in the image, the corresponding
coordinates are t [s] = x-axis and depth [mm] = y-axis shown above the TM image. For evaluation all
recorded pulses are measured on the picture and all values are used to calculate the average.
“Start” and “End” represent the starting and the end point of each pulse. “Tstart” and “Tend” are respectively
the difference between the starting and the endpoint of two consecutive pulses.
Tstart [1]  start [2] - start [1] etc.
The mean values of “Tstart” and “Tend” is the pulse duration (pulse duration DT). The heart rate (HR) is derived from pulse duration by:
HR 
4
1
DT
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For all pulses the end-systolic diameter ESD (distance between the highest membrane position and the
lowest) of the heart model is determined. This is the stroke of the membrane.
Stroke  ESDmm   Xmax mm  - Xmin mm 
If X is expressed in time and not in depth this formula transforms to:
ESD mm  
1480 m/s 
 X max µs  - X min µs 
2000
Assuming that the membrane deforms in a conical way, the displaced volume will be:
V
1
   D2  h
12
The heart model has a diameter of 45 mm and h is equal to ESD. So the formula for ESV is:
1
ESV 
   D 2  ESD
12
ESV ml  0.53014  ESDmm
Assuming the end-diastolic volume is zero, the membrane is flat, we can calculate the cardiac output as
follows:
Q  ESV  HR
Fig. 3:
Screenshots TM-mode, high heart (pump) rate
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Table 1: values from Fig. 2:
Screenshots TM-mode, slow heart (pump) rate.
Zero position : 55,8 mm
Pulse N°
1
2
3
4
5
Mean value
Start [s]
0,2
2,1
4,3
6,3
8,1
End [s]
1,7
3,8
5,7
7,6
9,6
Peak value [mm]
32,3
31,7
32,7
33,8
33,5
Measures values
32,8
Calculated values
Tstart[s]
1,9
2,2
2,0
1,8
2,0
Tend[s]
2,1
1,9
1,9
2,0
2,0
ESD [mm]
23,5
Table 2: values from Fig. 3:
24,1
23,1
22
22,3
23,0
Screenshots TM-mode, high heart (pump) rate.
Zero position : 55,2 mm
Pulse N°
1
2
3
4
5
6
7
8
9
10
Start [s]
0,0
1,1
2,1
3,1
4,1
5,1
6,1
7,1
8,0
9,0
End [s]
0,8
1,9
2,9
3,8
4,8
5,8
6,8
7,8
8,7
9,7
Mean value
Measures values
Peak value [mm]
31,5 32,0 32,7 32,7 32,9 32,8 32,0 33,6 32,2 32,7
32,5
Calculated values
Tstart[s]
1,1
1,0
1,0
1,0
1,0
1,0
1,0
0,9
1,0
1,0
Tend[s]
1,1
1,0
0,9
1,0
1,0
1,0
1,0
0,9
1,0
1,0
ESD [mm]
23,7 23,2 22,5 22,5 22,3 22,4 23,2 21,6
23
22,5
22,7
Table 3: Characteristic values of Fig 2 and Fig. 3.
Pulse duration (DT) [s]
Heart rate [Hz]
HRHz   1 / DTs
End systolic diameter ESD [mm]
6
Fig.: 2
Fig.: 3
2,0
1,0
0,5
1,0
23,0
22,7
End systolic volume ESV [ml]
ESV ml  0.53014  ESDmm
12,2
12,0
Cardiac output (Q) [ml/s]
Qml / s  ESVml* HRHz 
6,1
12,0
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