Ultrasound - Engineering World Health
Download
Report
Transcript Ultrasound - Engineering World Health
Ultrasound
WHO. “Scanning System, Ultrasonic.” From the publication: Core Medical Equipment. Geneva, Switzerland, 2011
History
Beginnings in the 1880s when Pierre Curie
introduced simple echo sounding
methods.
1913 discovery of SONAR -(Sound
Navigating and Ranging)
First introduced to medical world in 1950s
Applications
Dog whistle
Bets and dolphins
communication and orientation
Sonar
Submarine-boat
communication
Applications
Ultrasound-welding (for plastic)
Materials testing
Multiphase flow measurement
Medical Applications
Disinfection of instruments
Imaging
Detection of tumors (Oncology)
Assesment of the development of fetus
(OB/GYN)
Evaluation of blood flow (Cardiology)
Insertions
Therapy
WHO. “Scanning System, Ultrasonic.” From the publication: Core Medical
Equipment. Geneva, Switzerland, 2011
Principals of Operation
•
•
•
The ultrasound examination is usually carried out
with the patient in the supine position.
it is often useful to turn the patient in an oblique
position or to scan from the back in a prone
position, e.g. when scanning the kidneys.
Ultrasound also allows examination of the patient
in a sitting or standing position, which may help in
certain situations to diagnose stones or fluid
collection (e.g. pleural effusion)
WHO. “Manual of Diagnostic Ultrasound, Second Edition.” WHO, 2011
Frequency Range
Ultrasound_range_diagram.png:LightYear at en.wikipedia Ultrasound_range_diagram_png_(sk).svg:LightYear at en.wikipedia derivative work: Coolth
[CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], from Wikimedia Commons
Frequency Adjustment
Adjustment
• The choice of frequency (and transducer) depends on the penetration
depth needed. For examination of the abdomen, it may be useful to start
with a lower frequency (curved array, 3.5 MHz) and to use a higher
frequency if the region of interest is close to the transducer, e.g. the
bowel .
• Adaptation to the penetration depth needed: the whole screen should be
used for the region of interest.
• The mechanical index should be as low as possible (< 0.7 in adults).
• The time gain compensation (TGC) setting must compensate for
attenuation, e.g. depending on the abdominal wall, to obtain a
homogeneous image. It is useful to find a good TGC setting when
scanning a homogeneous section of the tissue, e.g. the right liver lobe in
the abdomen, before moving the transducer to the region of interest (Fig.
2.3, Fig. 2.4, Fig. 2.5).
• The focus, or zone of best resolution, should always be adjusted to the
point of interest.
WHO. “Manual of Diagnostic Ultrasound, Second Edition.” WHO, 2011.
Physics
MEDIA 1 - water
MEDIA 2 - air
TRANSMITTED WAVE
Nilock (2010), Ray optics diagram [image]. Retrieved from
https://en.wikipedia.org/wiki/Ray_(optics)#/media/File:Ray_optics_diagram_incidence_reflection_and_refraction.svg
Indices of Refraction
Josell7 (2010), Indices of Reflection [image]. Retrieved from https://commons.wikimedia.org/wiki/File:RefractionReflextion.svg
Principle
Georg Wiora (Dr. Schorsch) (Self drawn with Inkscape) [GFDL (http://www.gnu.org/copyleft/fdl.html), CC-BY-SA-3.0
(http://creativecommons.org/licenses/by-sa/3.0/) or CC BY-SA 2.5 (http://creativecommons.org/licenses/by-sa/2.5)], via Wikimedia Commons
Principle
Bruce Blaus. “Fetal Ultrasound.” Wikipedia Commons, November 9, 2015. Retrieved from: https://commons.wikimedia.org/wiki/File:Fetal_Ultrasound.png
Principals of Operation
Use:
Generally, modern ultrasound equipment consists of
‘all-round scanners’. Two transducers, usually a
curved array for the range 3–5 MHz and a linear
array for the range greater than 5 MHz to 10 MHz,
as a ‘small-part scanner’ can be used as ‘generalpurpose scanners’ for examination of all body
regions with the B-scan technique
WHO. “Manual of Diagnostic Ultrasound, Second Edition.” WHO, 2011.
Doppler fetal monitor:
Principle
Dirk Hünniger (2007), Doppler Sonography Blood Flow Diagram [image]. Retrieved from
https://en.wikipedia.org/wiki/Doppler_fetal_monitor#/media/File:DopplerSonographyBloodFlowDiagram-de.svg
Transducer
Linear array: small parts, superficial vascular, obstetrics
Curved array: abdominal, obstetric, transabdominal, or for transvaginal
or transrectal or pediatric imaging
Phased array: heart, liver, spleen, fontanelle, temple
Transducer
Wikipedia. “ Medical Ultrasound.” Wikipedia, pgs 1-15. Retrieved from: https://en.wikipedia.org/wiki/Medical_ultrasound
Distance equal to less than a wavelength for the minimum interference and
reduced grating lobes
Transducer
Rakruger (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commo
Transducer
Rakruger (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0) or GFDL (http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons
Transducer
From pulse generator
Delay
Dirk Hünniger (Own work) [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)], via
Wikimedia Commons
Transducer
Transducer
WHO. “Manual of Diagnostic Ultrasound, Second Edition.” WHO, 2011
.
Images
A-Mode
WHO. “Manual of Diagnostic Ultrasound, Second Edition.” WHO, 2011
.
Images
B-Mode
WHO. “Manual of Diagnostic Ultrasound, Second Edition.” WHO, 2011
Images
M-Mode (Motion-mode imaging)
Image line is a function of time
WHO. “Manual of Diagnostic Ultrasound, Second Edition.” WHO, 2011
Examples:
• Heart valves
• Cross-section of a carotid artery
.
Images
Doppler Mode
WHO. “Manual of Diagnostic Ultrasound, Second Edition.” WHO, 2011
.
Images
Doppler Mode - Flow track (reverse flow)
WHO. “Manual of Diagnostic Ultrasound, Second Edition.” WHO, 2011
.
Images
3D Imaging (4D + time)
4dsonogram.jpg: Madcapslaugh Ecografía_4D_-_Feto_12semanas_D.jpg: Rizome derivative work: Rizome (4dsonogram.jpg Ecografía_4D__Feto_12semanas_D.jpg) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Images
Frame Rate (for f = 3.5 MHz)
Bruce Blaus. “Fetal Ultrasound.” Wikipedia Commons, November 9,
2015. Retrieved from:
https://commons.wikimedia.org/wiki/File:Fetal_Ultrasound.png
4dsonogram.jpg: Madcapslaugh Ecografía_4D_-_Feto_12semanas_D.jpg:
Rizome derivative work: Rizome (4dsonogram.jpg Ecografía_4D__Feto_12semanas_D.jpg) [CC BY-SA 3.0
(http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Resolution
The size of an area in a scene that is
represented by one pixel in the image
Lower resolution leads to data reduction!
No author provided. Thegreenj~commonswiki assumed (based on copyright claims). [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0
(http://creativecommons.org/licenses/by-sa/3.0/)], via Wikimedia Commons
Resolution
Tradeoff between resolution and attenuation
↑higher frequency
↓shorter wavelength
Power loss:
↑ higher attenuation
dB
1
cm MHz
Typical Ultrasound Frequencies:
Deep Body
1.5 to 3.0 MHz
Superficial Structures
5.0 to 10.0 MHz
Gel
WHO. “Manual of Diagnostic Ultrasound, Second Edition.” WHO, 2011
A coupling agent is necessary to ensure good contact between the
transducer and the skin and to avoid artefacts caused by the presence of air
between them
Safety
Ultrasound at high energy can be used to
ablate (kill) tissue.
Cavitation (bubble formation)
Temperature increase is limited to 1º C for
safety
Block Diagram
RF AMPLIFIER
FM DEMODULATOR
AMPLIFIER
SIGNAL PROCESSING
SPEAKER
DISPLAY
RECEPTOR
BODY
TRANSMITTER
OSCILLATOR
Engineering World Health (2015), Ultrasound. Retrieved from library.ewh.org
Common Problems
Broken Probe
Broken cables
Power supply
User error
Therapy
George Lewis Jr (2008), ATDD Therapy [image]. Retrieved from https://en.wikipedia.org/wiki/Therapeutic_ultrasound#/media/File:ATDD_Topical_Application.jpg
Phacoemulsification
Takuma-sa (Own work) [CC BY-SA 3.0
(http://creativecommons.org/licenses/by-sa/3.0) or GFDL
(http://www.gnu.org/copyleft/fdl.html)], via Wikimedia Commons
Kidney Stones
A biplane x-ray apparatus is used to make sure the stone is at the focal point of
spark-generated shock waves from the ellipsoidal reflector.
Blausen.com staff. "Blausen gallery 2014". Wikiversity Journal of Medicine. DOI:10.15347/wjm/2014.010. ISSN 20018762. (Own work)
[CC BY 3.0 (http://creativecommons.org/licenses/by/3.0)], via Wikimedia Commons
Kidney Stones
Lithotriptor Machine
By DiverDave (Own work) [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Kidney Stones
Ureteroscopy
Percutaneous Nephrolithotomy
No author (2005), Ultrasonic instrument and kidney stone [Image]. Retrieved from
https://commons.wikimedia.org/wiki/File:Kidney_Stone_Image_4172-PH.jpg