Ultrasound and imaging

16- Dec - 201416- Dec - 2014

UltrasoundUltrasound

Arsalan KhanArsalan KhanMPhil (Clinical Medicine & Surgery)MPhil (Clinical Medicine & Surgery)

2014-ag-14512014-ag-1451

University of Agriculture, Faisalabad University of Agriculture, Faisalabad PakistanPakistan



The sound waves of frequency higher than The sound waves of frequency higher than 20KHz used for diagnostic and therapeutic 20KHz used for diagnostic and therapeutic purpose and imaging are called ultrasoundpurpose and imaging are called ultrasound

Sound waves are measured in Hertz (Hz)Sound waves are measured in Hertz (Hz) Diagnostic Ultrasound = 1-20 MHzDiagnostic Ultrasound = 1-20 MHz

Sound waves are produced by a Sound waves are produced by a transducertransducer

Principle: Pulse echo principlePrinciple: Pulse echo principle

Ultrasound waves not heard because Ultrasound waves not heard because human middle ear (eardrum) can’t vibrate human middle ear (eardrum) can’t vibrate at such frequency.at such frequency.

Frequency: 3.5 (intestines and U. bladder), Frequency: 3.5 (intestines and U. bladder), 5 (liver, pancreas and spleen), 5 (liver, pancreas and spleen),

7.5 (Rectum and testicles) and 7.5 (Rectum and testicles) and

10MHz (Superficial organs).10MHz (Superficial organs).

www.dvmdocs.webs.comwww.dvmdocs.webs.com

Transducer (probe)Transducer (probe)It consists of ; Piezoelectric crystalIt consists of ; Piezoelectric crystal

When electric charge is applied it emits sound When electric charge is applied it emits sound waveswavesSound is reflected from patientSound is reflected from patientReturning echo is converted to electric signal Returning echo is converted to electric signal grayscale image on monitor is formed grayscale image on monitor is formedEcho may be reflected, transmitted or refractedEcho may be reflected, transmitted or refractedThis probe has dual function that is it produces This probe has dual function that is it produces as well as receive the sound wavesas well as receive the sound wavesThe monitor converts these signals to imageThe monitor converts these signals to image

• As frequency increases, resolution improvesAs frequency increases, resolution improves

• As frequency increases, depth of penetration As frequency increases, depth of penetration decreasesdecreases

– Use higher frequency transducers to image more Use higher frequency transducers to image more superficial structuressuperficial structures

• Velocities:Velocities:– Soft tissues = 1400-1600m/secSoft tissues = 1400-1600m/sec– Bone = 4080 m/secBone = 4080 m/sec– Air = 330 m/secAir = 330 m/sec

WorkingWorkingA sound wave is produced by the vibration of Piezo A sound wave is produced by the vibration of Piezo electric crystals in the transducer and focused by the electric crystals in the transducer and focused by the transducer or lens in front of transducertransducer or lens in front of transducer

Water based gel is placed between the patient body and Water based gel is placed between the patient body and probe probe

These waves return in the same manner and are These waves return in the same manner and are received by the transducerreceived by the transducer

These waves are processed and are transformed into These waves are processed and are transformed into digital image on the monitordigital image on the monitor

Modes of SonographyModes of SonographyA-modeA-mode: A-mode (amplitude mode) is the : A-mode (amplitude mode) is the simplest type of ultrasound.; signals are simplest type of ultrasound.; signals are recorded as spikes on a graph. The vertical recorded as spikes on a graph. The vertical (Y) axis of the display shows the echo (Y) axis of the display shows the echo amplitude, and the horizontal (X) axis shows amplitude, and the horizontal (X) axis shows depth or distance into the patient. This type of depth or distance into the patient. This type of ultrasonography is used for ophthalmologic ultrasonography is used for ophthalmologic scanning.scanning.

It is single dimension and represented in the It is single dimension and represented in the form of spikes and peaks. form of spikes and peaks.

B-mode or 2D modeB-mode or 2D mode: In B-mode : In B-mode (brightness mode) ultrasound, a linear (brightness mode) ultrasound, a linear array of transducers simultaneously scans array of transducers simultaneously scans a plane through the body that can be a plane through the body that can be viewed as a two-dimensional image on viewed as a two-dimensional image on screen. B-mode is commonly used to screen. B-mode is commonly used to evaluate the developing fetus and to evaluate the developing fetus and to evaluate organs, including the liver, evaluate organs, including the liver, spleen, kidneys, thyroid gland, testes, spleen, kidneys, thyroid gland, testes, breasts, and prostate gland.breasts, and prostate gland.

Image shown by grey to bright dots.Image shown by grey to bright dots.


M-modeM-mode: In M-mode (motion mode) ultrasound, pulses : In M-mode (motion mode) ultrasound, pulses are emitted in quick succession – each time, either an A-are emitted in quick succession – each time, either an A-mode or B-mode image is taken. It is used for moving mode or B-mode image is taken. It is used for moving organs and image is shown as oscillations about vertical organs and image is shown as oscillations about vertical lines. M-mode is used primarily for assessment of fetal lines. M-mode is used primarily for assessment of fetal heartbeat and in cardiac imaging, most notably to heartbeat and in cardiac imaging, most notably to evaluate valvular disorders ( Mitral valve regurgitation).evaluate valvular disorders ( Mitral valve regurgitation).

Doppler modeDoppler mode: This mode makes use of the Doppler : This mode makes use of the Doppler effect in measuring and visualizing blood flow. In this effect in measuring and visualizing blood flow. In this mode, the velocity and direction of blood flows are mode, the velocity and direction of blood flows are depicted in a color map superimposed on the 2-D image. depicted in a color map superimposed on the 2-D image. It evaluates the blood perfusion of the organs.It evaluates the blood perfusion of the organs.

Scanners: Scanners:

1)1)Linear array: It is rectangular. Large Linear array: It is rectangular. Large number of piezo electric crystals. Used for number of piezo electric crystals. Used for superficial organs and rectal examination. superficial organs and rectal examination. It has 64x256 crystals.It has 64x256 crystals.

2)2)Sector array: It is convex probe. It has Sector array: It is convex probe. It has single piezo electric crystal.single piezo electric crystal.


Types of image interpretation: Types of image interpretation:

1)1)Hyper echoic: Returning of echo is very Hyper echoic: Returning of echo is very strong. It is reflecting from very high strong. It is reflecting from very high density tissue. Bright image is formed.density tissue. Bright image is formed.

2)2)Hypo echoic: Returning echo is weak. Low Hypo echoic: Returning echo is weak. Low density tissues. Grey to dark image is density tissues. Grey to dark image is formed. E.g. Tumours, abcess, formed. E.g. Tumours, abcess, Hematoma, granulation, inflammation.Hematoma, granulation, inflammation.

It is more cellular in nature.It is more cellular in nature.


3) An echoic: Complete attenuation. No 3) An echoic: Complete attenuation. No reflection. From fluid or air. Image is dark reflection. From fluid or air. Image is dark black. E.g. Urinary bladder, lungs, odema, black. E.g. Urinary bladder, lungs, odema, fluid or water accumulation.fluid or water accumulation.

4) Iso echoic: It is normal image. Grey color 4) Iso echoic: It is normal image. Grey color image is formed. E.g Liver, spleen, image is formed. E.g Liver, spleen, muscles etc.muscles etc.

N.B: Image of ultrasound is cross sectionalN.B: Image of ultrasound is cross sectional


ArtifactsArtifactsArtifacts lead to the improper display of the structures to Artifacts lead to the improper display of the structures to be imagedbe imaged

1) Acoustic shadowing: 1) Acoustic shadowing: – Ultrasound beam does not pass through an object because of Ultrasound beam does not pass through an object because of

reflection or absorption.reflection or absorption.– When the reflecting tissue is situated behind the strong reflecting When the reflecting tissue is situated behind the strong reflecting

tissue. E.g kidney muscles behind the stone. Weak echoes are tissue. E.g kidney muscles behind the stone. Weak echoes are received and the image can misguide for the presence of fluid. received and the image can misguide for the presence of fluid.

– Black area beyond the surface of the reflectorBlack area beyond the surface of the reflector– Examples: cystic calculi, bonesExamples: cystic calculi, bones

• Acoustic enhancementAcoustic enhancement– Hyperintense (bright) regions below objects of low Hyperintense (bright) regions below objects of low

Ultrasound beam attenuation. High echo. E.g odema Ultrasound beam attenuation. High echo. E.g odema or fluid behind the muscles. or fluid behind the muscles.

3)Refraction:3)Refraction: Occurs when the sound wave reaches two tissues of Occurs when the sound wave reaches two tissues of

differing acoustic impedancesdiffering acoustic impedances Ultrasound beam reaching the second tissue changes Ultrasound beam reaching the second tissue changes

directiondirection May cause an organ to be improperly displayedMay cause an organ to be improperly displayed

4) Reverberation: It is the back and forth motion of 4) Reverberation: It is the back and forth motion of ultrasound waves. E.g due to the presence of air the ultrasound waves. E.g due to the presence of air the waves cannot be processed.waves cannot be processed.

5) Mirror imaging: Double image is seen. It is due to the 5) Mirror imaging: Double image is seen. It is due to the production of large number of waves from the production of large number of waves from the transducer. transducer.

AdvantagesAdvantagesIt images It images muscle, , soft tissue, and bone surfaces very , and bone surfaces very well & interfaces between solid and fluid-filled spaces.well & interfaces between solid and fluid-filled spaces.

It renders "live" images, where the operator can It renders "live" images, where the operator can dynamically select the most useful section for diagnosingdynamically select the most useful section for diagnosing

Live images also allow for ultrasound-guided biopsiesLive images also allow for ultrasound-guided biopsies

It shows the structure of organs.It shows the structure of organs.

It has no known long-term side effects and rarely causes It has no known long-term side effects and rarely causes any discomfort to the patient.any discomfort to the patient.

Equipment is widely available and comparatively flexible.Equipment is widely available and comparatively flexible.

Small, easily carried scanners are available; Small, easily carried scanners are available;

Relatively inexpensive compared to other modes of Relatively inexpensive compared to other modes of investigation, such as investigation, such as computed X-ray tomography,or ,or magnetic resonance imaging..

DisadvantagesDisadvantages

Sonography performs very poorly when there is a gas Sonography performs very poorly when there is a gas between the transducer and the organ of interestbetween the transducer and the organ of interest

Sonographic devices have trouble penetrating Sonographic devices have trouble penetrating bone

Even in the absence of bone or air, the depth penetration Even in the absence of bone or air, the depth penetration of ultrasound may be limited depending on the frequency of ultrasound may be limited depending on the frequency of imagingof imaging

A high level of skill and experience is needed to acquire A high level of skill and experience is needed to acquire good-quality images and make accurate diagnosesgood-quality images and make accurate diagnoses

There is no scout image as there is with CT and MRI. There is no scout image as there is with CT and MRI. Once an image has been acquired there is no exact way Once an image has been acquired there is no exact way to tell which part of the body was imagedto tell which part of the body was imaged

Bioluminescence Bioluminescence ImagingImaging

Bioluminescence imagingBioluminescence imagingBioluminescence, the biochemical generation of light Bioluminescence, the biochemical generation of light by a living organism, is a naturally occurring by a living organism, is a naturally occurring phenomenon.phenomenon.

Bioluminescence imaging detects light produced by Bioluminescence imaging detects light produced by the reaction of luciferase enzymes with a defined the reaction of luciferase enzymes with a defined substrate. Luciferase enzymes catalyze the oxidation substrate. Luciferase enzymes catalyze the oxidation of a substrate (luciferin), and photons of light are a of a substrate (luciferin), and photons of light are a product of the reaction. product of the reaction.

Optical imaging by bioluminescence allows a low-Optical imaging by bioluminescence allows a low-cost, noninvasive, and real-time analysis of disease cost, noninvasive, and real-time analysis of disease processes at the molecular level in living organisms. processes at the molecular level in living organisms. Bioluminescence has been used to track tumor cells, Bioluminescence has been used to track tumor cells, bacterial and viral infections, gene expression, and bacterial and viral infections, gene expression, and treatment response. treatment response.

TechniqueTechnique

Instruments for BLI use a very sensitive charge-Instruments for BLI use a very sensitive charge-coupled device (CCD) camera to detect the low coupled device (CCD) camera to detect the low levels of light emitted from luciferase reporters levels of light emitted from luciferase reporters in in vivovivo. .

Bioluminescence can be measured by computer Bioluminescence can be measured by computer analysis of emitted photons, allowing relative analysis of emitted photons, allowing relative quantification of data. quantification of data.

Bioluminescence imaging utilizes native light emission Bioluminescence imaging utilizes native light emission from one of several organisms which bioluminesce. The from one of several organisms which bioluminesce. The three main sources are the North American three main sources are the North American firefly, the , the sea pansy (and related marine organisms), and bacteria (and related marine organisms), and bacteria like like Photorhabdus luminescens and and Vibrio fischeri. The . The DNAencoding the luminescent protein is incorporated encoding the luminescent protein is incorporated into the laboratory animal either via a into the laboratory animal either via a viral vector or by or by creating a creating a transgenic animal..

Systems derived from the three groups above differ in Systems derived from the three groups above differ in key ways;key ways;

1)1) Firefly luciferase requires D-luciferin to be injected into Firefly luciferase requires D-luciferin to be injected into the subject prior to imaging. The peak emission the subject prior to imaging. The peak emission wavelength is about 560 nm.wavelength is about 560 nm.

2)2) Renilla luciferase (from the Renilla luciferase (from the Sea pansy) requires its ) requires its substrate, coelenterazine, to be injected as well. substrate, coelenterazine, to be injected as well.

As opposed to luciferin, coelenterazine has a lower As opposed to luciferin, coelenterazine has a lower Additionally, the peak emission wavelength is about Additionally, the peak emission wavelength is about 480 nm480 nm

3) Bacterial luciferase has an advantage in that the 3) Bacterial luciferase has an advantage in that the luxlux operon used to express it also encodes the enzymes used to express it also encodes the enzymes required for substrate biosynthesis. Although originally required for substrate biosynthesis. Although originally believed to be functional only in believed to be functional only in prokaryotic organisms, organisms, where it is widely used for developing bioluminescent where it is widely used for developing bioluminescent pathogens, it has been genetically engineered to work in pathogens, it has been genetically engineered to work in mammalian expression systems as well. This mammalian expression systems as well. This luciferase reaction has a peak wavelength of about 490 nm. reaction has a peak wavelength of about 490 nm.

Diffuse Optical ImagingDiffuse Optical Imaging

Diffuse Optical ImagingDiffuse Optical ImagingDiffuse optical imagingDiffuse optical imaging (DOI) is a method of imaging (DOI) is a method of imaging using using Near Infrared Spectroscopic (NIRS) or (NIRS) or Fluorescence based methodsFluorescence based methods

InfraredInfrared ( (IRIR) is invisible radiant energy, ) is invisible radiant energy, electromagnetic radiation with longer with longer wavelengths than than those of those of visible light, extending from the nominal , extending from the nominal red edge of the edge of the visible spectrum at 700 at 700 nanometers to 1 mm to 1 mm

When used to create 3D volumetric models of the When used to create 3D volumetric models of the imaged material DOI is referred to as imaged material DOI is referred to as diffuse optical diffuse optical tomographytomography, whereas 2D imaging methods are , whereas 2D imaging methods are classified as classified as diffuse optical topographydiffuse optical topography

Diffuse Optical Tomography (DOT) and Imaging Diffuse Optical Tomography (DOT) and Imaging (DOI) are non-invasive techniques that utilize light in (DOI) are non-invasive techniques that utilize light in the near infrared spectral region to measure the the near infrared spectral region to measure the optical properties of physiological tissue. It works optical properties of physiological tissue. It works best on soft tissues such as breast and brain tissuebest on soft tissues such as breast and brain tissue

The technique has many applications to The technique has many applications to neuroscience, sports medicine, wound monitoring, neuroscience, sports medicine, wound monitoring, and cancer detection. Typically DOI techniques and cancer detection. Typically DOI techniques monitor changes in concentrations of oxygenated monitor changes in concentrations of oxygenated and deoxygenated and deoxygenated hemoglobin and may additionally and may additionally measure redox states of cytochromesmeasure redox states of cytochromes

By using this technique the neuroscientists study the By using this technique the neuroscientists study the natural neural activities and functioning of the brainnatural neural activities and functioning of the brain

In this method, a near-infrared laser is positioned on the In this method, a near-infrared laser is positioned on the scalp. Detectors composed of . Detectors composed of optical fiber bundles are bundles are located a few centimeters away from the light source. located a few centimeters away from the light source. These detectors sense how the path of light is altered, These detectors sense how the path of light is altered, either through either through absorption or scattering, as it crosses or scattering, as it crosses brain tissue.brain tissue.

This method can provide two types of information. First, This method can provide two types of information. First, it can be used to measure the absorption of light, which it can be used to measure the absorption of light, which is related to concentration of chemicals in the brain. is related to concentration of chemicals in the brain. Second, it can measure the scattering of light, which is Second, it can measure the scattering of light, which is related to physiological characteristics such as the related to physiological characteristics such as the swelling of ganglia and neuronsswelling of ganglia and neurons

The ability of light to penetrate tissue was first exploited The ability of light to penetrate tissue was first exploited by by Bright (1831)Bright (1831), who noted that light could be , who noted that light could be transmitted through the head of a child with transmitted through the head of a child with hydrocephalus. Hydrocephalus is an increase in the hydrocephalus. Hydrocephalus is an increase in the volume of cerebro-spinal fluid (CSF) in the head, and volume of cerebro-spinal fluid (CSF) in the head, and transillumination became an accepted diagnostic transillumination became an accepted diagnostic technique for hydrocephalus and intraventricular technique for hydrocephalus and intraventricular haemorrhage before the development of transcranial haemorrhage before the development of transcranial ultrasound.ultrasound.

CSF is relatively transparent and, more importantly, CSF is relatively transparent and, more importantly, does not significantly scatter light.does not significantly scatter light.

In an extension of the same concept, In an extension of the same concept, Curling Curling (1843)(1843) used transillumination to investigate a build-up of used transillumination to investigate a build-up of clear fluid in the testis, a condition known as hydrocele.clear fluid in the testis, a condition known as hydrocele.

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Ultrasound and imaging