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Ultrasonography

Ultrasonography. Dr. LeeAnn Pack Dipl. ACVR. Ultrasonography vs. Radiography. They complement each other Both have strengths and weaknesses Cost concerns  correct selection All patients should receive abdominal radiographs before ultrasonography Get all the information

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Ultrasonography

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  1. Ultrasonography Dr. LeeAnn Pack Dipl. ACVR

  2. Ultrasonography vs. Radiography • They complement each other • Both have strengths and weaknesses • Cost concerns  correct selection • All patients should receive abdominal radiographs before ultrasonography • Get all the information • May eliminate need for ultrasound

  3. Strengths of Ultrasonography • Determining origin of an abdominal mass • Evaluation of organ parenchyma • Liver, spleen, kidneys, adrenals, pancreas, intestines, prostate, bladder, heart • Fetal viability • Real time scanning – see movement/motion • Performing fine needle aspiration/ biopsy • Cells or tissue NOT images ultimately give us the definitive diagnosis for neoplasia, etc. • Ultrasound does not provide a histopathologic diagnosis

  4. Weaknesses of Ultrasonography • Ultrasound can’t penetrate gas or bone • Difficult to evaluate liver size, kidney size in dogs • Can’t assess intestinal gas patterns • Can’t evaluate some extra abdominal structures (i.e. spine) • Equipment can be expensive • Diagnostic success is user dependent • Must know anatomy very well

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

  6. Basic Ultrasound Physics • Transducer (probe) • Piezoelectric crystal • Emit sound after electric charge applied • Sound reflected from patient • Returning echo is converted to electric signal- grayscale image on monitor • Echo may be reflected, transmitted, or refracted • Transmit 1% receive 99% of the time

  7. Acoustic Impedance • The velocity of sound in a tissue and tissue density = determine acoustic impedance • Most soft tissues = 1400-1600m/sec • Bone = 4080, Air = 330 • Sound will not penetrate – gets reflected or absorbed • Travel time – dot depth

  8. Attenuation • Absorption = energy is captured by the tissue then converted to heat • Reflection = occurs at interfaces between tissues of different acoustic properties • Scattering = beam hits irregular interface – beam gets scattered

  9. Basic Ultrasound Physics • Sound waves are measured in Hertz (Hz) • Diagnostic ultrasound typically • 1-20 MHz • As frequency increases, resolution improves • As frequency increases, depth of penetration decreases Frequency Penetration

  10. Examples of Ultrasound Probes A B C A B C

  11. Transducers • Sector scanner – fan shaped beam • Small surface require for contact • Linear scanner – rectangle beam • Large contact area required • New ones are curvi-linear • These scan heads are much smaller with wide field of view

  12. Basic Ultrasound Physics • Monitor and computer • Convert signal to an image/ archive • Tools for image manipulation • Gain – amplification of returning echoes • Overall brightness • Time gain compensation (curve) • Adjust brightness at different depths • Freeze • Depth • Zoom in superficial, or zoom out for wide view • Depth limited by frequency • Focal zone • Optimal resolution wherever focal zone is

  13. Image controls

  14. Modes of Display • A mode • Spikes – where precise length and depth measurements are needed – ophtho • B mode (brightness) – used most often • 2 D reconstruction of the image slice • M mode – motion mode • Moving 1D image – cardiac mainly

  15. Artifacts • Improper machine settings – gain • Reverberation • Mirror image – liver GB • Comet tail – gas bubble • Ring down – skin transducer surface • Acoustic shadowing • Acoustic enhancement • Edge enhancement • Border of kidney

  16. Reverb – Comet Tails

  17. Reverb

  18. What Happened Here?

  19. Partial Mirror

  20. Enhancement

  21. Enhancement

  22. Enhancement

  23. Refraction

  24. Ultrasound Terminology • Never use dense, opaque, lucent • Anechoic • No returning echoes= black (acellular fluid) • Echogenic • Regarding fluid--some shade of grey d/t returning echoes • Relative terms • Comparison to normal echogenicity of the same organ or other structure • Hypoechoic, isoechoic, hyperechoic • Spleen should be hyperechoic to liver

  25. Patient Positioning - Prep • Dorsal recumbency • Lateral recumbency • Standing • Clip hair • Be sure to check with owners • Apply ultrasound gel • Alcohol can be used – esp. in horses

  26. Image Orientation and Labeling • Must be consistent • Symbol on screen ~ dot on transducer • “dot” to head and “dot” to patients right • “dot” lateral for transverse and proximal for longitudinal images • Label label label

  27. Indications for Abdominal Ultrasonography • Same as with abdominal radiographs • Should have some idea of what you are looking for—not just a fishing expedition • Further investigate a radiographic finding • ***If clinical signs or history indicate abdominal ultrasound, then it should be performed even if radiographs are normal!!!

  28. Ultrasound-guided FNA/ biopsies • NORMAL ABD U/S FINDINGS DO NOT MEAN ORGANS ARE NORMAL!!! • ***Do FNA if suspect disease • Abnormal u/s findings nonspecific • Benign and malignant masses identical • Bright liver may be secondary to Cushing’s dz or lymphoma • Aspirate abnormal structures (with few exceptions)!!! • Obtain owner approval prior to exam • Warn owner of risks • +/- Clotting profile

  29. Ultrasound-guided FNA/ biopsies • Risks of FNA’s • Fatal hemorrhage • Pneumothorax w/ pulmonary masses • Seeding of tumors • TCC • Sepsis • Abscesses

  30. Ultrasound-guided FNA/ biopsies • I 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 • I Occasionally aspirate • Kidneys (esp. if enlarged) • Pancreas • Urinary bladder masses • I Never aspirate • Adrenals • Gall bladder

  31. Ultrasound-guided FNA/ Fine Needle biopsies • Non-aspiration Technique • 22g 1.5in needle • 6 cc syringe • Short jabs into organ • Spray onto slide, smear, and check abd for hemorrhage

  32. Ultrasound-guided FNA • Aspiration technique • Same set up as with non-aspiration technique • With needle in structure, pull back plunger vigorously several times • Remove needle, fill syringe with air • Spray onto slide and smear

  33. Ultrasound-guided Core Biopsies • Use a special biopsy “gun” • 14-20g • Insert thru small skin incision • Much more representative sample • Tissue not just cells • Sometimes it is necessary to get the answer • But…. MUCH MORE LIKELY TO BLEED!

  34. Biopsy – Bleeding???

  35. Catheter in Bladder

  36. Intro Summary • Know your limitations • Lack of expertise • $15,000 vs. $150,000 machine • For abd or thx, do radiographs first • If safe and reasonable, do FNA’s of all suspected abnormal structures based on history, clinical signs, or the ultrasound exam • Abnormal structures can look normal • Of the structures that do look abnormal, benign and malignant processes can be identical • Documentation – save images in some fashion

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