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ULTRASOUND SCANNING

ULTRASOUND SCANNING. Introduction to Ultrasound. Ultrasound Scanning Physics. Characterized by sound waves of high frequency Higher than the range of human hearing Sound waves are measured in Hertz (Hz) Diagnostic U/S = 1-20 MHz Sound waves are produced by a transducer.

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ULTRASOUND SCANNING

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  1. ULTRASOUND SCANNING

  2. Introduction to Ultrasound

  3. Ultrasound Scanning Physics • Characterized by sound waves of high frequency • Higher than the range of human hearing • Sound waves are measured in Hertz (Hz) • Diagnostic U/S = 1-20 MHz • Sound waves are produced by a transducer

  4. Instrumentation - Ultrasound Probes B C

  5. Transducers/Probes • Sector scanner • Fan-shaped beam • Small surface required for contact • Cardiac imaging • Linear scanner • Rectanglular beam • Large contact area required • Curvi-linear scanner • Smaller scan head • Wider field of view

  6. Indications • As a compliment to abdominal radiographs • To determine the origin of an abdominal mass • Spleen, Liver • To facilitate fine needle aspiration/cystocentesis • To evaluate organ parenchyma • To rule in/out intestinal obstruction (foreign body) • ***If clinical signs or history indicate abdominal ultrasound, then it should be performed even if radiographs are normal!!!

  7. Indications for USG • Indications: abdomen, OBG,& Gynec. • Abdomen: Liver- Size, configuration, texture and contour. • To R/o ascites, abscess, cystic disease etc. • Growth – Primary and secondaries. • Jaundice: Viral Obstructive – Calculi, growth and annular pancreas.

  8. Renal US • Kidney: size and trauma. • Congenital: Agenesis • Calculi (Radiolucent) • Hydronephrosis. • Infections and abscess. • Tumors

  9. Pancreas • Pancreas: • Infections – calcification, duct dilatation • Complications of pancreatitis. • Pseudo cyst and abscess. • Spleen: • Splenomegaly- Fever and abscess. • Portal hypertension • RTA – Splenic injury

  10. Abdominal US • Abdominal mass, Lymphadenopathy • G.I tract: Mass Obstruction Volvulus Worms Omentalsecondaries

  11. OBG • OBG: • Missed abortion • Ectopic pregnancy • 5th week – Gestation sac • 6th week - Fetal pole • Cardiac activity • 12th week – Head (BPD) • 18-20 week- Fetal anomaly scan. • Placenta: Praevia and abruption. • Hydramnios, twins, molar pregnancy. • Position of fetus - Cephalic, breech. • Gestational age: BPD, HC, AC and FL

  12. Gynec • Gynec: • Uterus – Size, congenital anomaly (Bifid, septate etc) • Mass – Fibroids and growth. • Infertility. • Ovaries: Ovulation, mass – cysts and growth. • P.I.D: Free fluid in POD.

  13. Why do you need both X-ray and USG? • Examples • Prostatic adenocarcinoma seen on ultrasound • Has it spread to the lumbar vertebrae? • Coughing patient with mitral regurgitation on echocardiogram • Does the patient have pulmonary edema? • Enlarged liver on radiographs • Can get a guided FNA with ultrasound

  14. Mirror Image Artifact

  15. Comet Tails

  16. Artifacts • Acoustic shadowing • U/S beam does not pass through an object because of reflection or absorption • Black area beyond the surface of the reflector • Examples: cystic calculi, bones • Acoustic enhancement • Hyperintense (bright) regions below objects of low U/S beam attenuation • AKA Through transmission • Examples: cyst or urinary bladder

  17. Acoustic Shadowing

  18. Acoustic Enhancement

  19. Artifacts • Refraction: • Occurs when the sound wave reaches two tissues of differing acoustic impedances • U/S beam reaching the second tissue changes direction • May cause an organ to be improperly displayed

  20. Ultrasound-Guided FNA/ Biopsies • Routinely aspirate: • Liver (masses and diffuse disease) • Spleen (nodules and diffuse disease) • Gastrointestinal masses • Enlarged lymph nodes • Enlarged prostate • Pulmonary/ mediastinal masses (usually don’t biopsy due to risk of pneumothorax • Occasionally aspirate: • Kidneys (esp. if enlarged) • Pancreas • Urinary bladder masses • Never aspirate: • Adrenal glands • Gall bladder

  21. Ultrasound-Guided FNA/Biopsies • Non-aspiration Technique • 22g 1.5in needle • 10 cc syringe • Short jabs into organ • Spray onto slide, smear, and check abdomen for hemorrhage

  22. DOPPLER

  23. Waves from stationary and moving sources Stationary Moving

  24. Doppler Effect • Shift in perceived frequency when either source or listener are moving relative to one another • Familiar occurrence in audible sounds • Also occurs in medical ultrasound

  25. Please note: the ‘squishing’ of the wave-fronts in the middle diagram and the stretching in the lower diagram are exaggerated. Realistically the Doppler shifts are so small in ultrasound you would hardly see any difference in the wave-fronts compared to the unshifted one on top. These are artists’ diagrams.

  26. Doppler shift • Doppler shift is the difference between the transmitted and received frequencies. • Transmitted and received frequencies are in the MHz range • Doppler shift frequencies often in audible range

  27. Scattering from blood • Source of signals for flow imaging: • Red blood cells • Much smaller than l • Rayleigh scatterers • Scattering increases with frequency • Scattering increases with number of targets • Double the number of scatterers, scattered intensity doubles!

  28. h cos 2o = 0.999 a h cos 60o = 0.5 a Cosine Function h cos q = a/h q a

  29. The frequency of the Doppler shift is proportional to the cosine of the Doppler angle • Angle formed by the ultrasound beam and the direction of flow • Doppler frequency varies with the cosine of the angle. • Cosine = 1 for 0o • Cosine = ½ for 60o • Cosine = 0 for 90o • For angles between 0 and 10o, cosine is close to 1. • The larger the angle (up to 90o), the smaller the cosine

  30. Angle Correct Error

  31. Range (depth) selection done by a procedure called “gating” Gating +beam dimensions, define “sample volume”

  32. Duplex Mode (Duplex Doppler) B-mode imaging + Doppler

  33. THANK YOU

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