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ULTRASOUND IN MEDICAL DIAGNOSTICS. Prof. Ivo Hrazdira, MD., DSc. WHAT IS ULTRASOUND?. Acoustic vibrations of frequencies higher than 20 kHz, non audible by human ear
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ULTRASOUND IN MEDICAL DIAGNOSTICS Prof. Ivo Hrazdira, MD., DSc.
WHAT IS ULTRASOUND? • Acoustic vibrations of frequencies higher than 20 kHz, non audible by human ear • According to the type of interaction with cells and tissues: - ACTIVE ULTRASOUND – high intensity(applications in physical therapy and surgery) - PASSIVE ULTRASOUND – low intensity(applications in medical diagnostics)
ACOUSTIC PARAMETERS • Source: - FREQUENCY - INTENSITY • Medium: - SPEED OF PROPAGATION - ACOUSTIC IMPEDANCE - ATTENUATION: - absorption . - scattering
DIAGNOSTIC ULTRASOUND • PHYSICAL PRINCIPLE ULTRASONIC WAVES PASSING THROUGH THE BODY ARE PARTIALLY REFLECTED ON TISSUE INTERFACES. REFLECTIONS (ECHOES) ARE RECEIVED, PROCESSED AND DISPLAYED
HISTORY OF ULTRASOUND PREPARATORY PERIOD • 1842 - DOPPLER: PRINCIPLE OF FREQUENCY SHIFT • 1880 - BROTHERS CURIE: DISCOVERY OF PIEZOELECTRIC PHENOMENON • 1916 - LANGEVIN AND CHILOWSKI: CONSTRUCTION OF THE FIRST ULTRASOUND GENERATOR (SONAR) • 1929 - SOKOLOV: BASIS OF NON-DESTRUCTIVE ULTRASOUND MATERIAL TESTING
HISTORY OF DIAGNOSTIC ULTRASOUND FIRST ATTEMPS • 1942 - DUSSIK: HYPERPHONOGRAPIE (TRANSMISSION METHOD) • 1949 - KEIDEL: HEART VOLUME MEASUREMENT • 1949 - UCHIDA: A-MODE ENCEPHALOGRAPHY • 1950 - WILD: TISSUE DIFFERENTIATION • 1951 - WAGAI: BILL STONE DETECTION
HISTORY OF DIAGNOSTIC ULTRASOUND • 1942 - FIRST ATTEMP - UNSUCCESSFUL CLINICAL APPLICATIONS • 1950 - 1D IMAGING (A- MODE) • 1954 - ECHOCARDIOGRAPHY (M-MODE) • 1955 - 2D - IMAGE OF ABDOMEN (B - MODE) • 1958 - 2D - IMAGING IN OBSTETRICS • 1958 - 2D - IMAGING IN OPHTHALMOLOGY • 1968 - TRANSRECTAL EXAMINATION • 1968 - FIRST CONTRAST IMAGING (SALINE)
HISTORY OF DIAGNOSTIC ULTRASOUND CLINICAL APPLICATIONS (CONTINUED) • 1978 - TRANSESOPHAGEAL EXAMINATION • 1990 - BROAD-BAND TRANSDUCERS • 1992 - 3D IMAGING IN OB/GYN • 1992 - TRANSPULMONARY ECHOCONTRAST AGENTS • 1996 - NATIVE HARMONIC IMAGING • 1998 – 4D (3D imaging in real time)
DIAGNOSTIC DEVICE • MAIN PARTS OF A DIAGNOSTIC DEVICE • ELECTROACOUTIC TRANSDUCER • GENERATOR OF ELECTRIC IMPULSES • PROCESSING OF RECEIVED ECHOES • DISPLAY • RECORDING SYSTEM
TRANSDUCERS sector convex linear transvaginal/transrectal transesophageal
DIAGNOSTIC ULTRASOUND • IMAGING METHODS: - A MODE (one-dimensional) - B MODE (two-dimensional, three-dimensional) • DOPPLER METHODS: - CW - PULSED - COLOUR • COMBINED METHODS (duplex, triplex)
DIAGNOSTIC FREQUENCIES • 2 - 6 MHz abdominal ultrasound, obstetrical and gynaecological exam, echocardiography, transcranial Doppler • 7.5 - 14 MHz small parts, vascular Doppler, musculoskelatal ultrasound
DIAGNOSTIC FREQUENCIES • 10 - 20 MHzophthalmology, special vascular exam • 20 - 50 MHz endoluminal exam, ultrasound biomicroscopy (ophthalmology, dermatology)
B- MODE IN MUSCULOSKELETAL ULTRASOUND Meniscal Tear
PROGRESS IN ULTRASONOGRAPHY • IMPROVED IMAGE DISPLAY - digital technology - 3D/4D imaging IMPROVED SIGNAL DETECTION - echo-enhancing agents - harmonic imaging
PROGRESS IN ULTRASONOGRAPHY • NOVEL METHODS - anisotropic imaging - perfusion imaging - elastography • NOVEL APPLICATIONS - intraoperative - intraluminal
DIGITAL TECHNOLOGY • BROADBAND SCANHEADS/ BROADBAND BEAMFORMING - captures full tissue signature • EXTENDED SIGNAL PROCESSING - digitally preserves entire signal • TISSUE SPECIFIC IMAGING - improves signal/noise ratio for detection of small, low-contrast lesions
WHAT ARE ECHOCONTRAST AGENTS? • AIR OR GAS MICROBUBBLES, FREE OR INCAPSULATED IN A POLYMER COVER • ACCORDING TO THEIR HIGHER DIFFERENCE IN ACOUSTIC IMPEDANCE, CONTRAST AGENTS ENHANCE THE ECHOGENICITY OF THE BODY SPACE IN WHICH THEY WERE INTRODUCED
ECHOCONTRAST AGENTS CATEGORY OF ECHOCONTRAST AGENTS: • GAS BUBBLES INTRODUCED INTO THE ORGANISM (ECHOVIST, LEVOVIST, ALBUNEX, ECHOVIEW) • GAS BUBBLES FORMED IN THE ORGANISM (ECHOGEN)
ECHOCONTRAST AGENTS • IN VASCULAR IMAGING - enhance weak signals resulting from deep vessels or slow flow (hyperaemia, ischaemia) - improve signals from malignant neovascularization • IN NON-VASCULAR IMAGING - increase the reflectivity of particular normal or pathologic tissues (targeted agents) - delineate body cavities and communications
HARMONIC IMAGING NEW MODE OF ULTRASOUND IMAGING, IN WHICH THE FUNDAMENTAL FREQUENCY OF RETOURNING ECHOES IS SUPPRESSED AND SIGNALS OF HARMONIC FREQUENCY ARE RECEIVED, PROCESSED AND DISPLEYED
FORMS OF HARMONIC IMAGING • CONTRAST HARMONIC IMAGING microbubbles of echo enhancing agents are able to resonate and emit harmonic signal • NATIVE HARMONIC IMAGING harmonic signal is produced by oscillation of tissue structures due to the non-linear propagation of ultrasound
receiving 5 MHz 2.5 5 transmission 2.5 MHz PRINCIPLE OF HARMONIC IMAGING supression
HARMONIC IMAGING stone FUNDAMENTAL HARMONIC
3-D IMAGING • 3-D IMAGING TECHNOLOGY ALLOWS PHYSICIANS TO VIEW PATIENT´S NORMAL AND PATHOLOGIC ANATOMY AS A VOLUME IMAGE • IT IS SUGGESTED THAT 3-D IMAGING WILL PROVIDE A CENTRAL INTEGRATING FOCUS IN ULTRASOUND DIAGNOSTICS
3-D IMAGING PHYSICAL PRINCIPLE: • THE TRANSDUCER IS MOVED DURING EXPOSURE (linear shift, swinging, rotation) • RECEIVED ECHOES ARE STORED IN THE MEMORY • THE IMAGE IN THE CHOSEN PLAIN IS RECONSTRUCTED MATHEMATICALY
3-D COLOUR DOPPLER SONOGRAPHY • REPRESENTS A COMBINATION OF 3-D AND POWER DOPPLER TECHNOLOGY: transducer elements are electronically or manually sectored during exposure • 3D CDS ALLOWS DEPICTION OF THE OVERALL VASCULARITY IN THE AREA OF INTEREST (esp. tumours)
ANISOTROPIC IMAGING PHYSICAL PRINCIPLE • IN ULTRASOUND TECHNOLOGY, ANISOTROPY REPRESENTS A DIRECTIONAL DEPENDENCY OF BACKSCATTERED WAVES • THIS MODALITY CAN BE USED FOR DIFFERENTIATING NORMAL ANISOTROPIC TISSUES FROM ISOTROPIC ABNORMALITIES
ANISOTROPIC IMAGING AREAS OF CLINICAL APPLICATIONS • CARDIOLOGY: MYOCARDIUM EXAMINATION • NEPHROLOGY: EXAMINATION OF RENAL CORTEX • MUSCULOSKELETAL ULTRASOUND: EXAMINATIONS OF TENDONS AND CARTILAGES
ELASTOGRAPHY METHOD FOR IMAGING THE ELASTIC PROPERTIES OF TISSUES • REPRESENTS AN IMAGING ANALOGY TO PHYSICAL EXAMINATION BY TOUCH • DIFFERENCES IN MECHANICAL PROPERTIES OF TISSUES CAN BE IMAGED IN 2D- OR 3D- COLOUR-SCALE MANNER
ELASTOGRAPHY MODEL MIMICING CONTRAST LESION IN PROSTATE
ENDOLUMINAL IMAGING Transversal view of oesophageal sphincter 1 mucosa, 2 submucosa, 3 circular muscle, 4 intermuscular connective tissue, 5 longitudinal muscle, 6 adventitia 2D and 3D image of advanced oesophageal cancer
DOPPLER ULTRASOUND • A.Ch. Doppler (1803-1853) • DOPPLER PRINCIPLE (1842) - frequency shift due to the movement of the source or reflector • DOPPLER METHODS SERVE IN MEDICINE FOR: - DETECTION OF TISSUE MOVEMENTS - MEASUREMENT OF BLOOD FLOW VELOCITY AND DIRECTION
MILESTONES OF DOPPLER ULTRASOUND • 1960 -CONTINUOUS WAVE DOPPLER (CWD) • 1974 -PULSE WAVE DOPPLER (PWD) • 1982 -TRANSCRANIAL DOPPLER (TCD) • 1986 -COLOUR FLOW MAPPING (CFM) • 1992 -CONTRAST HARMONIC IMAGING (CHI) • 1994 -POWER DOPPLER (PD) • 1996 -TISSUE DOPPLER IMAGING (TDI)