Ultrasound & MRI method of examination

1. Methods of diagnosticMethods of diagnostic
ultrasound, radionuclideultrasound, radionuclide
imaging and magneticimaging and magnetic
resonance imaging (MRI).resonance imaging (MRI).
Bases of ultrasound,Bases of ultrasound,
radionuclide and MRIradionuclide and MRI
semiotics of pathology ofsemiotics of pathology of
different organs and systems.different organs and systems.

2. Major purposes of using ultrasound in radiology:Major purposes of using ultrasound in radiology:
1)1) to make sectional imagesto make sectional images
ultrasonographyultrasonography
2)2) to measure blood flow velocitiesto measure blood flow velocities
Doppler ultrasoundDoppler ultrasound
(or Doppler sonography).(or Doppler sonography).

3. Basic principles of ultrasonographyBasic principles of ultrasonography
Ultrasound refers to sound waves with a frequencyUltrasound refers to sound waves with a frequency
above 20,000 Hz (above the human hearingabove 20,000 Hz (above the human hearing
range).range).
Frequencies in the 2 - 10 MHz range are mostFrequencies in the 2 - 10 MHz range are most
commonly used.commonly used.
Transmitting a narrow beam of ultrasoundTransmitting a narrow beam of ultrasound intointo
the body from a transducerthe body from a transducer ReflectingReflecting
the ultrasound from the various tissues back tothe ultrasound from the various tissues back to
the transducer asthe transducer as echoesechoes formation offormation of
the sectional ultrasound image (similar to thethe sectional ultrasound image (similar to the
sonar of fishing boats).sonar of fishing boats).

4. Basic principles of ultrasonographyBasic principles of ultrasonography
NB!NB! The ultrasound isThe ultrasound is generatedgenerated in a hand-heldin a hand-held
transducertransducer, usually placed on the skin of the patient, usually placed on the skin of the patient
adjacent to the anatomical region to be examined.adjacent to the anatomical region to be examined.
The most essential part of a transducer is one orThe most essential part of a transducer is one or
severalseveral piezo-electrical crystalspiezo-electrical crystals with awith a dual propertydual property --
they are the generator of ultrasound and receiver ofthey are the generator of ultrasound and receiver of
echoes.echoes.

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6. Attenuation and reflectionAttenuation and reflection
AttenuationAttenuation isis total loss of intensity of the ultrasoundtotal loss of intensity of the ultrasound
transmitted during passage through the tissues of thetransmitted during passage through the tissues of the
body (mostly due tobody (mostly due to absorption of the ultrasound asabsorption of the ultrasound as
heat).heat).
The part of the ultrasound may be scatteredThe part of the ultrasound may be scattered oror
reflectedreflected from the tissues back to the transducer asfrom the tissues back to the transducer as
echoesechoes..
NB!NB! A fraction of the ultrasound will be reflected if there isA fraction of the ultrasound will be reflected if there is
a change in the "resistance" to the propagation of thea change in the "resistance" to the propagation of the
ultrasound. “ultrasound. “ResistanceResistance" (or acoustic impedance) of" (or acoustic impedance) of
tissue is determined by the density and elasticity of atissue is determined by the density and elasticity of a
tissue.tissue.
The larger the change in acoustic impedance, the largerThe larger the change in acoustic impedance, the larger
the reflection of ultrasound.the reflection of ultrasound.

7. Attenuation and reflectionAttenuation and reflection
Extremely large difference in acoustic impedanceExtremely large difference in acoustic impedance
betweenbetween soft tissue and gassoft tissue and gas nearly all of thenearly all of the
ultrasound is reflected at the border a gel is appliedultrasound is reflected at the border a gel is applied
between a patient's skin and thebetween a patient's skin and the
transducer.transducer.
ultrasonography is unable to display lungs and regionsultrasonography is unable to display lungs and regions
covered by bowel gas.covered by bowel gas.
Relatively large difference in acoustic impedanceRelatively large difference in acoustic impedance
betweenbetween soft tissue and cortical bonesoft tissue and cortical bone most bonesmost bones
therefore restrict the application of diagnostictherefore restrict the application of diagnostic
ultrasound.ultrasound.
NB!NB! Diagnostic ultrasound don’t use ionizing radiation.Diagnostic ultrasound don’t use ionizing radiation.
Biological effects:Biological effects: heatingheating andand microvibrationmicrovibration in thein the

8. Ultrasound modes used in medicine:Ultrasound modes used in medicine:
A-, M- and B-modes.A-, M- and B-modes.
Every echo returning to the transducer generates anEvery echo returning to the transducer generates an
electrical signalelectrical signal (amplitude is determined by the(amplitude is determined by the
strength of the echo).strength of the echo).
The transformation of electrical signals intoThe transformation of electrical signals into an imagean image
on a monitoron a monitor is based on the relatively constantis based on the relatively constant
propagation velocity of ultrasound through tissues.propagation velocity of ultrasound through tissues.
Measuring the time from transmission of theMeasuring the time from transmission of the
ultrasound pulse to reception of the echoesultrasound pulse to reception of the echoes
estimating the depths from which the echoesestimating the depths from which the echoes
originated .originated .

9. A-mode displayA-mode display (the simplest visual display of the(the simplest visual display of the
recorded echoes):recorded echoes):
thethe echoesechoes from the various depths are shown asfrom the various depths are shown as
vertical spikes on a horizontal linevertical spikes on a horizontal line indicating depth.indicating depth.
The strength of the echo the amplitude ofThe strength of the echo the amplitude of
each spike.each spike.

10. M-mode:M-mode: adding dynamics to A-mode format:adding dynamics to A-mode format:
the depth axis has a vertical orientation on the monitor. Thethe depth axis has a vertical orientation on the monitor. The
variousvarious echoesechoes are shown asare shown as dotsdots (brightness determined by the(brightness determined by the
echo strength).echo strength).
BrightBright curvescurves indicate theindicate the
change in positionchange in position of theof the
structures with time.structures with time.

11. B-modeB-mode isis a two-dimensional, sectional display of the anatomy:a two-dimensional, sectional display of the anatomy:
real-time scannersreal-time scanners are used. A narrow beam of transmittedare used. A narrow beam of transmitted
ultrasound is made to scan through the patient in a linear orultrasound is made to scan through the patient in a linear or
sector-shaped fashion, and echoes are recorded from eachsector-shaped fashion, and echoes are recorded from each
position of the beam. The echoes from all positions formposition of the beam. The echoes from all positions form
rectangular or sector-shaped imagerectangular or sector-shaped image on the screen.on the screen.
Solid and soft tissues areSolid and soft tissues are bright (echopositive)bright (echopositive)and fluid isand fluid is darkdark
(echonegative).(echonegative).
Image is dynamic!Image is dynamic!

12. Doppler sonography:Doppler sonography:
Doppler effect:Doppler effect: the frequency of a wave form is dependentthe frequency of a wave form is dependent
on the relative velocity between the emitter and receptoron the relative velocity between the emitter and receptor
of the wave. Inof the wave. In DSDS of blood vessels and cardiac chambers,of blood vessels and cardiac chambers,
a narrow beam of ultrasound is transmitted into the bodya narrow beam of ultrasound is transmitted into the body
from a Doppler transducer, a small fraction of thefrom a Doppler transducer, a small fraction of the
ultrasound will beultrasound will be reflected from the red blood cells.reflected from the red blood cells.
Doppler shift:Doppler shift: the difference between the frequency of thethe difference between the frequency of the
echoes and the frequency of the ultrasound (directlyechoes and the frequency of the ultrasound (directly
proportional to the blood flow velocity).proportional to the blood flow velocity).
During flow measurement the change in ultrasoundDuring flow measurement the change in ultrasound
frequencyfrequency is automaticallyis automatically converted into blood flowconverted into blood flow
velocityvelocity..

13. Doppler sonography:Doppler sonography:
We see Doppler sonography as a graph or wave formWe see Doppler sonography as a graph or wave form
showingshowing
velocity along the ordinate and time along the abscissa.velocity along the ordinate and time along the abscissa.

14. Doppler sonography:Doppler sonography:
NB!NB! If the red blood cellsIf the red blood cells move towards the Dopplermove towards the Doppler
transducertransducer, the echoes reflected will have a higher frequency, the echoes reflected will have a higher frequency
than the one emitted from the transducer. In these cases wethan the one emitted from the transducer. In these cases we
seesee wave above linewave above line..
When blood flowsWhen blood flows away from the transduceraway from the transducer, the echoes will, the echoes will
have a lower frequency than the emitted one and we seehave a lower frequency than the emitted one and we see wavewave
under lineunder line..

15. Duplex scanning:Duplex scanning:
combining real-time ultrasonography and Dopplercombining real-time ultrasonography and Doppler
sonography.sonography.
ColoursColours are superimposed on the real-time B-modeare superimposed on the real-time B-mode
image and indicateimage and indicate the presence of flowing bloodthe presence of flowing blood..
Stationary tissues are grey and vessels are colourStationary tissues are grey and vessels are colour
(blue, red, yellow,(blue, red, yellow,
green).green).
ColourColour is determined byis determined by
relative mean velocityrelative mean velocity
andand directiondirection of flow.of flow.

16. The advantages of US:
– Ionizing radiation is not used.
– No contraindications; harmlessness and the possibility of multiple
application.
– The possibility of application under any conditions with the help of
mobile and portable apparatuses.
– The high resolution capacity of soft tissues visualization.
– Investigation is performed in the real time mode.
– The method enables to conduct intracavitary and intraoperative
investigation with the help of special detectors which are introduced
immediately in cavities (for example, transesophageally, transrectally,
transvaginally, etc.). Special detectors built in endoscopes enable to
carry out laparoscopic, intravascular, ultrasound investigations.

17. The disadvantages of US:
– The weakening of a signal with the enlargement of
tissues thickness (the weakening of ultrasound
penetration).
– An US-signal does not penetrate bone tissue.
– The gas in the lungs and cavities reflects acoustic
waves and prevents from organs visualization.
– Dependence of investigation result on a patient’s
being prepared for investigation and an operator’s
qualification.

18. RADIONUCLIDE IMAGING (DIAGNOSTIC NUCLEARRADIONUCLIDE IMAGING (DIAGNOSTIC NUCLEAR
MEDICINE)MEDICINE)
Basis:Basis: radioactive isotopes concentrated in certain tissuesradioactive isotopes concentrated in certain tissues
emitemit gamma radiationgamma radiation..
Introducing of radiopharmaceuticalsIntroducing of radiopharmaceuticals (RPH)(RPH) into bodyinto body
accumulation of RPH detection of radiation emitted
from RPH inside patient.
NB! Radioactive part of RPH is often coupled to carrier
molecule to determine RPH distribution in body.
Distribution may be determined by metabolic
processes or by local perfusion or blood flow or by
ventilation.
Major advantage of RN imaging:
functional information.
Relative disadvantage:
low spatial resolution.

19. Detector:Detector:
large, disk-shapedlarge, disk-shaped scintillation crystalscintillation crystal (main(main
component of the gamma camera)component of the gamma camera)
scintigraphy.scintigraphy.
Radiography:Radiography: only curves – without image!only curves – without image!

20. Tomographic techniquesTomographic techniques of RN imaging:of RN imaging:
I)I) single photon emission computed tomographysingle photon emission computed tomography
(SPECT):(SPECT):
gamma cameragamma camera rotatesrotates around patientaround patient
recording radioactivity at numerous anglesrecording radioactivity at numerous angles
reconstruction of sectional images;reconstruction of sectional images;
2)2) positron emission tomographypositron emission tomography (PET):(PET):
using positrons emitting radionuclides and specialusing positrons emitting radionuclides and special
detectors.detectors.
NB!NB! PET allows estimation of RN concentrationPET allows estimation of RN concentration
and study of metabolic processes at various diseaseand study of metabolic processes at various disease
states, especially in heart and brain.states, especially in heart and brain.

21. MRI:MRI:
sectional imagessectional images inin any planeany plane ofof any partany part of the body.of the body.
No ionizing radiationNo ionizing radiation is involved, and air or bone represent nois involved, and air or bone represent no
obstacle to imaging.obstacle to imaging.
TheThe most basic componentsmost basic components of a MR unit:of a MR unit:
- a very strong magnet,- a very strong magnet,
- a radio transmitter,- a radio transmitter,
- a radio frequency receiver coil,- a radio frequency receiver coil,
- a computer.- a computer.
The interior of the magnet is oftenThe interior of the magnet is often
tunnel-shaped and big enough totunnel-shaped and big enough to
contain a human adult.contain a human adult.
Most magnets have a magnetic fieldMost magnets have a magnetic field
orientated parallel to the long axis of theorientated parallel to the long axis of the
patient.patient.
For clinical MRI, field strengthsFor clinical MRI, field strengths
till 3.0 tesla have been used.till 3.0 tesla have been used.

22. MRI bases:MRI bases:
hydrogen nuclei ( protons) of the patients body within the stronghydrogen nuclei ( protons) of the patients body within the strong
magnetic field line up in the direction of the external field (similarmagnetic field line up in the direction of the external field (similar
to compass needles) and rotate around the direction of the externalto compass needles) and rotate around the direction of the external
magnetic field (magnetic field (precessionprecession).).
A majority of protons precess with magneticA majority of protons precess with magnetic
moments in a direction closely parallel to themoments in a direction closely parallel to the
external magnetic fieldexternal magnetic field ("parallelprotons“),("parallelprotons“),
the remainder - towards return directionthe remainder - towards return direction
(“antiparallelprotons“)(“antiparallelprotons“) creation of a netcreation of a net
magnetic moment in the tissues of the patientmagnetic moment in the tissues of the patient
the tissues become magnetic.the tissues become magnetic.
NB!NB! The size of tissues magnetismThe size of tissues magnetism is determined by:is determined by:
- the- the surplus of parallel protonssurplus of parallel protons (proportional to the external(proportional to the external
magnetic field strength, but is always very small - 1 to 10 per 1magnetic field strength, but is always very small - 1 to 10 per 1
million protons;million protons;
- the- the proton density of tissueproton density of tissue..

23. The net magnetic moment in tissues isThe net magnetic moment in tissues is not strong enoughnot strong enough to induceto induce
an electric current in a receiver coil located outside the patient.an electric current in a receiver coil located outside the patient.
To make the tissue magnetism induce a current in a coil,To make the tissue magnetism induce a current in a coil, radioradio
waves are needed -waves are needed - to enhance the tissue magnetism.to enhance the tissue magnetism.
NB!NB! The frequency of the radio waves must beThe frequency of the radio waves must be exactly equalexactly equal to theto the
resonance frequency of the protonsresonance frequency of the protons (the phenomenon of magnetic(the phenomenon of magnetic
resonance).resonance).
The tissue magnetism forced by resonance with electromagneticThe tissue magnetism forced by resonance with electromagnetic
waves induces an electric currentwaves induces an electric current (the MR signal)(the MR signal) in the receiverin the receiver
coil.coil.
used for reconstruction of sectionalused for reconstruction of sectional
MR imagesMR images
Tissues with aTissues with a strong magnetismstrong magnetism induce strong signals and appearinduce strong signals and appear
brightbright in the image, tissues with ain the image, tissues with a weak magnetismweak magnetism induce weakinduce weak
signals and appearsignals and appear darkdark..

24. Contrast in MRI is determined by:Contrast in MRI is determined by:
- differences in tissue magnetism (- differences in tissue magnetism (proton densityproton density): air –): air –
darkdark, fluids –, fluids – brightbright, soft tissues –, soft tissues – graygray;;
- parameters- parameters T1T1 andand T2:T2: to reconstruct an image, severalto reconstruct an image, several
MR signals are needed, and several radio frequency pulsesMR signals are needed, and several radio frequency pulses
must be transmitted. Between the pulse transmissions, themust be transmitted. Between the pulse transmissions, the
protons undergoprotons undergo two different relaxation processestwo different relaxation processes, T1- and, T1- and
T2-relaxation.T2-relaxation.

25. The rapid decay of the induced signal is the result ofThe rapid decay of the induced signal is the result of T2-T2-
relaxationrelaxation..
The T2 value is dependantThe T2 value is dependant on the physical and chemicalon the physical and chemical
propertiesproperties of the tissues. Fluid and fluid-like tissues typicallyof the tissues. Fluid and fluid-like tissues typically
have a long T2, and solid tissues and substances have a shorthave a long T2, and solid tissues and substances have a short
T2.T2. The longer T2, the brighter tissueThe longer T2, the brighter tissue..
NB!NB! MR images where contrast is largely determined byMR images where contrast is largely determined by
differences in T2 are calleddifferences in T2 are called T2-weighted imagesT2-weighted images..

26. T1 relaxationT1 relaxation is a slower process than T2 relaxation.is a slower process than T2 relaxation.
The T1 value is largely determined byThe T1 value is largely determined by molecular size andmolecular size and
mobility:mobility: T1 is shortest in tissues having molecules of medium sizeT1 is shortest in tissues having molecules of medium size
and mobility, e.g. adipose tissue. Smaller, more mobile moleculesand mobility, e.g. adipose tissue. Smaller, more mobile molecules
(as in fluids) and larger, less mobile molecules (as in solids) have(as in fluids) and larger, less mobile molecules (as in solids) have
longer T1 values.longer T1 values. The shorter T1, the brighter tissue.The shorter T1, the brighter tissue.
NB!NB! MR images where contrast is largely determined byMR images where contrast is largely determined by
differences in T1, are calleddifferences in T1, are called T1-weighted imagesT1-weighted images..
Thus, there areThus, there are proton densityproton density
weighted MR images,weighted MR images, T2T2-and-and
T1T1-weighted images.-weighted images.

27. NB!NB! Radio frequency pulses will induce MR signals onlyRadio frequency pulses will induce MR signals only
if the pulse frequency is exactly equal to theif the pulse frequency is exactly equal to the
proton resonance frequencyproton resonance frequency
possible to collect MR signals from a predeterminedpossible to collect MR signals from a predetermined
thin slice of tissue.thin slice of tissue.
MRI isMRI is tomographic technique!tomographic technique!

28. ““Empty phenomenon”:Empty phenomenon”: circulating bloodcirculating blood due to its flow velocitydue to its flow velocity
don’t induce MR signal and is an effective "negative" contrastdon’t induce MR signal and is an effective "negative" contrast
medium.medium. Vessel lumen and heart chambersVessel lumen and heart chambers appearappear darkdark andand
delineated by the brighter surrounding stationary tissue.delineated by the brighter surrounding stationary tissue.
NB!NB! Stagnant bloodStagnant blood has a high signal intensity (has a high signal intensity (brightnessbrightness) due) due
to the proton density, T1, and T2 of blood.to the proton density, T1, and T2 of blood.

29. Contrast media used for MRI:Contrast media used for MRI:
all have magnetic properties andall have magnetic properties and change the signal intensitychange the signal intensity ofof
the tissues where they are located, by shortening the relaxationthe tissues where they are located, by shortening the relaxation
processes of the surrounding protons.processes of the surrounding protons.
The most commonly used contrast mediaThe most commonly used contrast media
contain the paramagnetic metal ioncontain the paramagnetic metal ion
gadoliniumgadolinium. These contrast media are. These contrast media are
administered by intravenous injection.administered by intravenous injection.

30. NBNB! MRI hasn’t harmful effects.! MRI hasn’t harmful effects.
Main biological effect:Main biological effect: heatingheating first trimesterfirst trimester pregnancypregnancy is anis an
absolute contraindication to MRI (possible heating of the foetus).absolute contraindication to MRI (possible heating of the foetus).
OtherOther contraindications:contraindications:
- ferromagnetic intracranial aneurysmal clips,- ferromagnetic intracranial aneurysmal clips,
- intraocular ferromagnetic foreign objects,- intraocular ferromagnetic foreign objects,
- cardiac pacemaker.- cardiac pacemaker.

31. The advantages of MRI:
- A high tissue contrast as compared to US and CT.
- The possibility of visualizing a circulating fluid and
vascular pathology by the methods of non-contrast
angiography, cholangiopancreatography, myelography,
pyelography and urethrography.
- Obtaining MRI images in different impulsive sequences
by changing the intensity of signals from fatty tissue and
vascular edemas.
- Obtaining images immediately in any projection (axial,
coronary, sagittal).

32. The disadvantages of MRI:
– A considerable duration of MRI.
– Insufficient visualization of calcifications.
– A wide spectrum of artifacts.
– Application of sedative means in investigating
children of early age and patients with
claustrophobia.

33. The indications for performing MRI:
- Congenital pathology of organs and systems.
- Demyelizing and other diseases of the CNS, voluminous formations of the
CNS, cerebrovascular stroke and others.
- Pathology of organs of mediastinum and retroperitoneal space, digestive and
eliminative organs, skeleton, pelvic organs, soft tissues and others.
- Diseases of the CNS: tumors, infarctions, hematomas, vascular diseases.
- Heart and great vessels diseases.
- Diseases of the GIT.
- Diseases of the musculoskeletal system, including the spinal column.

34. The contraindications for performing MRI:
- The presence of an artificial cardiac pacemaker in the
organism.
- The presence of ferromagnetic prostheses in the
organism.
- The presence of cerebral ventricular shunts in the
organism.
- The presence of any metallic objects in the body
(splinters, clips and others).
- Possible epileptic seizures, convulsions, loss of
consciousness.
- The first trimester of pregnancy.

35. The side effects of MRI:
- Dizziness, a metallic taste for a short time.
- Fibrillation of the ventricles.
- Thermal effects.