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Basics of sonography and anatomy of chest wall
 

Basics of sonography and anatomy of chest wall

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    Basics of sonography and anatomy of chest wall Basics of sonography and anatomy of chest wall Presentation Transcript

    • Basics of Chest Sonographyand Anatomy of Chest WallByGamal Rabie Agmy , MD , FCCPProfessor of Chest Diseases ,Assiut UniversityERS National Delegate of Egypt
    • • Diagnostic ultrasonographyis the only clinical imagingtechnology currently in usethat does not depend onelectromagnetic radiation.
    • Ultrasound TransducerSpeakertransmits sound pulsesMicrophonereceives echoes• Acts as both speaker & microphoneEmits very short sound pulseListens a very long time for returning echoes• Can only do one at a time
    • Physical Principles
    • Cycle• 1 Cycle = 1 repetitive periodic oscillationCycle
    • Frequency• # of cycles per second• Measured in Hertz (Hz)-Human Hearing 20 - 20,000 Hz-Ultrasound > 20,000 Hz-Diagnostic Ultrasound 2.5 to 10MHz(this is what we use!)
    • frequency1 cycle in 1 second = 1Hz1 second= 1 Hertz
    • High Frequency• High frequency (5-10 MHz)greater resolutionless penetration• Shallow structuresvascular, abscess, t/v gyn,testicular
    • Low Frequency• Low frequency (2-3.5 MHz)greater penetrationless resolution• Deep structuresAorta, t/a gyn, card, gb, renal
    • Wavelength• The length of one complete cycle• A measurable distance
    • WavelengthWavelength
    • Amplitude• The degree of variance from the normalAmplitude
    • The Machine
    • Ultrasound scanners• Anatomy of a scanner:– Transmitter– Transducer– Receiver– Processor– Display– Storage
    • Transmitter• a crystal makes energy into soundwaves and then receives sound wavesand converts to energy• This is the Piezoelectric effect• u/s machines use time elapsed with apresumed velocity (1,540 m/s) tocalculate depth of tissue interface• Image accuracy is therefore dependenton accuracy of the presumed velocity.
    • Transducers• Continuous mode– continuous alternating current– doppler or theraputic u/s– 2 crystals –1 talks, 1 listens• Pulsed mode– Diagnostic u/s– Crystal talks and then listens
    • Receiver• Sound waves hit and make voltageacross the crystal-• The receiver detects and amplifiesthese voltages• Compensates for attenuation
    • Signal Amplification• TGC (time gaincompensation)– Manual control– Selective enhancementor suppression of sectorsof the image– enhance deep andsuppress superficial*blinders• Gain– Manual control– Affects all parts of theimage equally– Seen as a change in“brightness” of theimages on the entirescreen*glasses
    • Changing the TGC
    • Changing the Gain
    • Displays• B-mode– Real time gray scale, 2D– Flip book- 15-60 images per second• M-mode– Echo amplitude and position of movingtargets– Valves, vessels, chambers
    • “B” Mode
    • “M” Mode
    • Image properties• Echogenicity- amount of energyreflected back from tissue interface– Hyperechoic - greatest intensity - white– Anechoic - no signal - black– Hypoechoic – Intermediate - shades ofgray
    • HyperechoicHypoechoicAnechoic
    • Image Resolution• Image quality is dependent on– Axial Resolution– Lateral Resolution– Focal Zone– Probe Selection– Frequency Selection– Recognition of Artifacts
    • Axial Resolution• Ability to differentiate two objects alongthe long axis of the ultrasound beam• Determined by the pulse length• Product of wavelength λ and # of cycles inpulse• Decreases as frequency f increases• Higher frequencies produce betterresolution
    • Axial Resolution• 5 MHz transducer– Wavelength 0.308mm– Pulse of 3 cycles– Pulse lengthapproximately 1mm– Maximum resolutiondistance of two objects= 1 mm• 10 MHz transducer– Wavelength 0.15mm– Pulse of 3 cycles– Pulse lengthapproximately 0.5mm– Maximum resolutiondistance of two objects= 0.5mm
    • Axial Resolutionbodyscreen
    • Lateral Resolution• The ultrasound beam is made up ofmultiple individual beams• The individual beams are fused toappear as one beam• The distances between the singlebeams determines the lateral resolution
    • Lateral resolution• Ability to differentiate objects along anaxis perpendicular to the ultrasoundbeam• Dependent on the width of theultrasound beam, which can becontrolled by focusing the beam• Dependent on the distance between theobjects
    • Lateral Resolutionbodyscreen
    • Focal Zone• Objects within the focal zone • Objects outside of focal zoneFocal zoneFocal zone
    • Probe options• Linear Array • Curved Array
    • Ultrasound Artifacts• Can be falsely interpreted as realpathology• May obscure pathology• Important to understand and appreciate
    • Ultrasound Artifacts• Acoustic enhancement• Acoustic shadowing• Lateral cystic shadowing (edge artifact)• Wide beam artifact• Side lobe artifact• Reverberation artifact• Gain artifact• Contact artifact
    • Acoustic Enhancement• Opposite of acoustic shadowing• Better ultrasound transmission allowsenhancement of the ultrasound signaldistal to that region
    • Acoustic Enhancement
    • Acoustic Shadowing• Occurs distal to any highly reflective orhighly attenuating surface• Important diagnostic clue seen in alarge number of medical conditions– Biliary stones– Renal stones– Tissue calcifications
    • Acoustic Shadowing• Shadow may be more prominent thanthe object causing it• Failure to visualize the source of ashadow is usually caused by the objectbeing outside the plane of theultrasound beam
    • Acoustic Shadowing
    • Acoustic Shadowing
    • Lateral Cystic Shadowing• A type of refraction artifact• Can be falsely interpreted as anacoustic shadow (similar to gallstone)
    • XLateral Cystic Shadowing
    • Beam-Width Artifact• Gas bubbles in the duodenum cansimulate a gall stone• Does not assume a dependent posture• Do not conform precisely to the walls ofthe gallbladder
    • Beam-Width ArtifactBeam-width artifactGas in the duodenumsimulating stones
    • Side Lobe Artifact• More than one ultrasound beam isgenerated at the transducer head• The beams other than the central axisbeam are referred to as side lobes• Side lobes are of low intensity
    • Side Lobe Artifact• Occasionally causeartifacts• The artifact by beobviated byalternating the angleof the transducerhead
    • Side Lobe Artifact
    • Reverberation Artifacts• Several types• Caused by the echo bouncing back andforth between two or more highlyreflective surfaces
    • Reverberation Artifacts• On the monitor parallel bands ofreverberation echoes are seen• This causes a “comet-tail” pattern• Common reflective layers– Abdominal wall– Foreign bodies– Gas
    • Reverberation Artifacts
    • Reverberation Artifacts
    • Gain Artifact
    • Contact artifact• Caused by poor probe-patient interface
    • Traditionally, air has been considered theenemy of ultrasound and the lung has beenconsidered an organ not amenable toultrasonographic examination. Visualizing thelung is essential to treating patients who arecritically ill.
    • Lines written on ultrasound in the fiveLight’s editions43781021222781983 1990 1995 2001 2008
    • 1998 -2008
    • 2009
    • 2010V SCAN
    • Probes
    • A high-resolution linear transducer of 5–10 MHz issuitable for imaging the thorax wall and theparietal pleura (Mathis 2004). More recentlyintroduced probes of 10–13 MHz are excellent forevaluating lymph nodes (Gritzmann 2005), pleuraand the surface of the lung.For investigation of the lung a convex or sector probeof 3–5 MHz provides adequate depth of penetration.
    • Transthoracic Sonography
    • Scanning Positions forChest Sonography
    • Normal Anatomy
    • Normal lung surfaceLeft panel: Pleural line and A line (real-time).The pleural line is located 0.5 cm below the rib line in the adult.Its visible length between two ribs in the longitudinal scan isapproximately 2 cm. The upper rib, pleural line, and lower rib (verticalarrows) outline a characteristicpattern called the bat sign.
    • Normal Chest UltrasoundSuperficial tissuesribsPosterioracousticshadowingImpureacousticshadowingPleurallineMuscleFatPleuraLung
    • the "seashore sign" (Fig.3).
    • Duplex Doppler sonogram of a 5 x 3 cm hypoechoic mass(adenocarcinoma) in upper lobe of left lung shows blood flowat margin of tumor near pleura. Spectral waveform revealsarteriovenous shunting: low-impedance flow with highsystolic and diastolic velocities. Pulsatility index = 0.90,resistive index = 0.51, peak systolic velocity = 0.47 m/sec, enddiastolic velocity =0.23 m/sec, peak frequency shift = 3.8 kHz,
    • Duplex Doppler sonogram in 67-year-old man with pulmonarytuberculosis in lower lobe of left lung shows several blue andred flow signals in massiike lesion. Spectral waveform revealshigh-impedance flow. Pulsetility index = 4.20, resistive index =0.93, peak systolic velocity = 0.45 m/sec, end diastolicvelocity = 0.03 m/sec, Doppler angle = 21#{
    • Alveolar-interstitialsyndrome
    • (Chest. 2008; 133:836-837)© 2008 American College of ChestPhysiciansUltrasound: The Pulmonologist’s NewBest FriendMomen M. Wahidi, MD, FCCPDurham, NCDirector, Interventional Pulmonology, DukeUniversity Medical Center, Box 3683,Durham, NC 27710