• USG

• Blood flow

• Doppler effect

• Pulse oxymetry

USG IMAGING

Ultrasound (US)

sound waves with frequencies higher than theupper audible limit of human hearing (>20 kHz).

Low-frequency ultrasound (20 kHz - 100 kHz) surgery, tools and material cleaning, ...

High-frequency ultrasound (from 100 kHz) therapy (1 - 3 MHz), diagnostic (2 - 40 MHz).

Hyper sound (from 1 GHz)acoustic microscopy

https://upload.wikimedia.org/wikipedia/commons/7/74/Ultrasound_range_diagram.svg

http://acousticmicroscopy.net/wp-content/uploads/2012/05/LifeScience-11.jpg

In linear waves the particles oscillate in direction of the wave and concentration and dilution of particles in the environment happens.

K : bulk modulus (Pa) (volumetric elasticity)ρ : density (kg/m3)𝒄𝒄 = 𝑲𝑲

𝝆𝝆

The stronger bonds among particles, the faster spreading of ultrasound.

Tissue Velocity of wave spreading[m/s]

acoustic impedance[Pa.s.m-1]

Fat 1450 1,48Skull 3360 6Blood 1550 1,61

Air 343 0,0004Shung, K. Kirk: Diagnostic ultrasound – Imaging and Blood flow measurements. 2006. Taylor&Francis Group. Boca Raton. 203 s. ISBN: 0-8247-4096-3

Range and Resolution

• Lower frequency

• Longer wave lenght

• Worse resolution

• Deeper penetration

into the tissue

• Higher frequency

• Shorter wave lenght

• Better resolution

• Smaller penetration

into the tissue

SkinSubcutal structures

Eye, breasts, fingers

Thyroid gland, circulation, endoscopy

Kidneys, pankreas, muscles, skeleton

Liver, spleen

Heart, brain

o 1880 Pierre Curie.o Material generates an electric potential in response

to a mechanical stress (deformation of piezoelectric crystal).

o Vice versa. The voltage changes the crystal and this generates its oscillations.

Piezoelectric effect

Ultrasound waves spread in soft tissue as a linear wave.

https://giphy.com/gifs/waves-T4K5Lynx75UpG

In bones US spreads as transverse wave.

https://i1.wp.com/www.churchofzero.com/wp-content/uploads/wave2.gif

US in Tissues

o Velocity of US does not depend on used frequency, but on acoustic resistance or impedance, thus on resistance of tissue.

o Acoustic impedance characterizes US spreading in an environment. It is defined as density of matter multiplied by velocity of the sound in the material (kg.m-2.s-1).

o Thanks to AI US can depict different tissues.

o Acoustic window – tissue that has minimal AI – shows what is behind the tissue – full bladder.

https://image.slidesharecdn.com/ultrasounddiagnostics-fin-110914111504-phpapp02/95/ultrasound-diagnostics-fin-29-728.jpg?cb=1316000711

o Echo – a discontinuity in the propagation medium –US wave spreads through material with different acoustic impedance.

o To minimalize losses in US energy during US wave spreading into environment/medium we use gels –acoustic environments.

https://teacheratsea.files.wordpress.com/2012/08/dlphfish1.gif?w=530

A – linear probe, B – sector probe, C – convex probe

ProbesAccording to geometric shape of generated picture

there are few types of probes:Linear array transducer

Piezocrystals in line - linear picture easy to read. Sector array transducer

Effective for small surfaces and wide final picture. Convex array transducer

Combination of previous two.

A B C

https://sites.google.com/site/tritonbkrzysztofczyk/_/rsrc/1387168402085/transducer-arrays/1-s2_0-S0079610706000861-gr1.jpg

Modes of USG

A – Amplitude mode– amount of reflected energy

B – Brightness mode: - 2D imaging

• Intensity of reflexion – echogenita• Depht and direction

M – Motion mode: combination of A and B– creation of video motion capture

AdvantagesNon-invaive, speed, no transport

of patient needed, availability, low price

Disadvantagesworse imaging in areas with differentacoustic impedances (gas in colon, lung parenchyma, compact bone …)

Blood flow – physical principles and laws

http://intranet.tdmu.edu.ua/data/kafedra/internal/normal_phiz/classes_stud/en/nurse/Bacchaour%20of%20sciences%20in%20nurses/ADN/12_Blood_flow.htm

1. Poisseuille law

2. Continuity laws – only for 1 part of vessel

A1.v1 = A2.v2

If A increases, then v decreases

Flowing blood volume is constant

http://figures.boundless-cdn.com/17400/full/flow.jpeg

3. Bernoulli principle for whole system

You need to considertotal section area ofvessels:

– Sum area of capillaries>> area of aorta

– Blood velocity in capillaries << blood velocity in aorta

– Pressure in capillaries << pressure in aorta (distance betweenaorta and capillaries)

http://biology.stackexchange.com/questions/36443/how-does-bernoulli-s-principle-apply-to-the-cardiovascular-system

4. Energy conservation law - elastic recoil of artery

http://faculty.pasadena.edu/dkwon/chapter%2015/chapter%2015_files/textmostly/slide10.html

Ea>Ek

Ev>Ep

Ea+Ev = const

Measurement ofblood flow velocity

Doppler effectchange in frequency or wavelenghtdue to relative motion between the

source and observer

http://www.spacetelescope.org/videos/hubblecast43f/

Doppler ultrasound measurement of blood flowbased on the difference between frequency of ultrasound

emitted by a probe and frequency reflected by moving erythrocytes

Difference between frequencies of emitted and detected (reflected) ultrasound – proportional to the blood flow

velocity

Upravené podľa: Deeg, K., Rupprecht, T., Hofbeck, M.: Doppler Sonography in Infancy and Childhood. Springer Switzerland 2015 ISBN 978-3-319-03505-5.

1. Detected frequency same as frequency emitted by a source that does not move

2. Detected frequency higher if the source is moving toward detector

3. Detected frequency lower if the source is moving away from detector

Principle of the measurementSource

(erythrocytes)Detector

(USG probe)

1.

2.

3.

Charly Whisky 18:20, 27 January 2007

dependence of detected frequency on movement of anobserved or a source

c – velocity of the waves/ultrasound in the mediumfv – frequency emitted by a sourcefd – detected frequency (reflected waves/ultrasound)α – angle subtended by the direction of emitted ultrasound and direction

of the movement of the measured object

Velocity overestimation

Pulse oxymetry• Pulse oximeters

measure how much of the hemoglobin in blood is carrying oxygen (oxygen saturation).– Cheap– Non invasive

• Pulse oximetermeasures pulsatileblood

https://www.howequipmentworks.com/pulse_oximeter/https://www.google.sk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwij8P_m74TQAhULchQKHUgIAzcQjRwIBw&url=https%3A%2F%2Fwww.aliexpress.com%2Fbluetooth-pulse-oximeter_reviews.html&bvm=bv.136811127,d.d24&psig=AFQjCNHucO2_4vdNTu2bCod7gGAJtHIncA&ust=1477997341833339

Oximeter – physical principleLambert Beer law

Light source

Light detector

https://www.howequipmentworks.com/pulse_oximeter/

I = I0 . 10-εcd

A =ε.c.d

I0 – intensity of originallightI – intensity of passing lightD-thicknes of arteryC-concentration ofhaemoglobin of artery

𝑆𝑆𝑆𝑆𝑆𝑆2 = 𝐾𝐾 ×𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐷𝐷𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐷𝐷𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴𝐴

Absorption of pulsing arterial bloodAbsorption of non pulsing arterial bloodAbsorption of non pulsing venal blood

Absorption of tissue

SpO2 – level values

• Levels:– physiological values 90 – 100 % (95– 100 %)– acceptable as a standard 85 – 89 %

(for chronic diseases, such as COPD)– abnormal values < 80 %– life-threatening < 70 %

Objective:Using an ultrasound (USG) device and a vernier calliper - determine the dimensions of the selected cavity within the ultrasound phantom and the depth of its upper edge below the phantom's surface.

Verify the acquired values on real structures.

Tasks:1. Use the ultrasound device to measure the size of the cavity found in the ultrasound phantom. Calculate its circumference and its area in the cross-section.2. Use the ultrasound device to measure the distance from the top edge of the cavity (found within the ultrasound phantom) to the phantom's surface.

3. Use a vernier calliper to measure the dimension of the real structure corresponding to the cavity within the phantom, calculate its circumference and the area in its cross-section.

4. Use a ruler to measure the depth of the cavity from the surface of the phantom from its outer side.

5. Discuss and explain possible differences within the measured results.

ON/OFF switch

Figure 3: Location of the control elements for the measurement. 1. Trackball – used for cursor movement. 2. Buttons used for ellipse measurement. 3. Measurement button. Measurement

selection. 4. Set button. Start and end of

consecutive measurement. 5. Clear button. Clears the cursor and

measurement data from the screen. "

Ultrasonographic imagingon the monitor if USG device.

1. Probe of the USG device.2. Top edge of the image.

Starting point for depth.3. Ultrasonographic field.4. Structure of interest.5. Measurement of diameters

(2x) or longitude and heigthof the found structure.

6. Depth measurement od thefound structure.

Measurement using a ruler and a caliper

1. From the outer side, for the choosen cavity measure the phantom’s shortest depthUsing a ruler. Write the measured value in the table. Put the phatom to its place.

2. Using a caliper measure the respective dimensions (2x diameter, or the sidelongitude and height) on the real choosen structure with a tenth of a millimeteraccuracy. Write the measureds value in the table.

3. Calculate the circumferences and areas of the respective cross-sections.

How to work with a caliper

Vernier scale

Result = 23 + 0.6 = 213.6 mm

Main scale

Liver (20), kidney (60, 61), spleen (50)

Real ultrasonographic measurement. (Very well observable structures, women)

Berthold Block: Color Atlas of Ultrasound Anatomy. Georg Thieme Verlag, Stuttgart, Nemecko. 2014. ISBN 3-13-139051- 4.

Liver (20), kidney (60, 61), spleen (50)

Real ultrasonographic measurement. (Very well observable structures, men)

Berthold Block: Color Atlas of Ultrasound Anatomy. Georg Thieme Verlag, Stuttgart, Nemecko. 2014. ISBN 3-13-139051- 4.

Kidney

Berthold Block: Color Atlas of Ultrasound Anatomy. Georg Thieme Verlag, Stuttgart, Nemecko. 2014. ISBN 3-13-139051- 4.