Ultrasound Flashcards
US Physics Principles (4 “steps”)
- Sound waves are tiny vibrations in air pressure
- These vibrations move at a constant speed and reflect a counstant amount back while moving through similar media (ie soft tissues)
- When vibrations encounter different media (ie fluid, air, bone), these vibrations will dramatically change.
- This is what accounts for image-creation in US
Media good for US (2)
- Soft tissue
- Fluid-filled structures
US MOA (5 steps)
- Transducer emits a sound beam
- Sound beam encounters tissue and sends a specific echo back to the transducer
- The transducer calculates the time for the echo to return and correlates that with a distance traveled
- Machine draws a representing distance info
- Many dots together create an interpretable image
Transducer Operations
Detectable frequencies in:
- Human ear
- US machine
- Human ear: 20-20,000 cycles/sec (hz)
- US: 2,000,000-15,000,000 cycles/sec (hz)
Define Doppler Effect
Echoes emitted from moving objects vary in frequency compared to that same object in a stationary position
- Frequency is higher from an object moving towards the receiver
- Frequency is lower from an object moving away from the receiver
Doppler in US (3 purposes)
- Monitor fetal heart
- Evaluate blood flow in heart and carotid arteries
- Describe the following characteristics of blood flow
- Presence/absence
- Direction
- Speed
- Character
Doppler Presentation
Fluid appearance in US
Dark black c enhancement beyond the structure
Define “Enhancement”
Lack of attentuation causes sound passing through fluid filled structures to appear brighter than sound passing through tissue. This creates a lightened column beyond the fluid-filled structure
Define “Shadowing”
Failure of sound beam to pass through certain structrures, usually air or calcifications. Appears as a brighter structure (this absorbs all of the light) above a band of darkness.
Define “Edge Shadow”
Dark beams on either side of enhanced tissue due to reflection of incident beam off the sides of a fluid-filled object
Define “Anechoic”
A structure without internal echoes. These are tissues that do not show well on US, and will appear black.
Examples:
- Bone
- Blood vessels without doppler
- Fat
- Lymph notes
- Nerves
Define “Complex” Tissue
Tissue that contains both fluid-filled (anechoic) and solid areas
Define “Cyst” in terms of US
Fluid-filled structure with the following qualities on US:
- Well-defined borders
- Anechoic (or nearly anechoic)
- Good acoustic enhancement
Define “Echogenic”/”Hyperechoic”
Descriptive term for a structure that produces brighter echos relative to its surroundings.
Define “Hypoechoic”
Descriptive term for a structure that produces lower brightness (echogenicity) relative to its surroundings.
Define “Homogeneous”
Tissue of uniform composition. In US, homogeneous tissues will appear the same.
See generally homoegenous liver texture:
Define “Loculated”
Cystic structure divided into various compartments
Most popular US applications, in terms of tissues studied (16)
Think about the composition of these tissues and how they are compatible with US
- Obstetrics
- Fetal brain
- Gynocology
- Fertility
- Palpable masses
- Breast
- Testicle
- Prostate
- Liver
- Gallbladder
- Pancreas
- Spleen
- Kidneys
- Thyroid
- Pediatric hips
- Echocardiography
- Aorta
- Doppler studies
- Carotid arteries
- Venous leg studies
- Arterial leg studies
Identify Pathology
AAA
Note anechoic structure with bulge in middle, representing the aneurism
Identify Pathology
Interventricular Hemorrhage
Identify Pathology
Hydronephrosis
Note heterogenic contrast between anechoic fluid sacs and normal tissue. Observe some enhancement beyond fluid portions of the kidney. Ultimately, kidney borders are definable.
Identify Pathology
Kidney Stone
Note small echogenic/hyperechoic nodules with shadowing. Lateral border of kidney is at the top of the screen, renal pelvis is at the bottom.
Identify Patholgy and Describe US features (This is an easy one…)
Gallstone
Note anechoic organ with a echogenic/hyperechoic, regularly bordered, generally homoegeneous mass. Observe strong shadowing beyond GS. Regular borders to the rest of the GB
Identify Pathology
Liver metastasis
Note heterogenicity within clearly defined liver borders. Also to be noted, the anechoic mass is a blood vessel.
Echocardiogram Views (4)
FAST Scan (define, use, 4 areas examined)
Define: FAST stands for Focused Accessment c Sonography for Trauma. It is an emergency scan done to determine the extent of internal trauma.
Use: Examine for free fluid
Exam Areas:
- Perihepatic + Hepato-renal space
- Perisplenic
- Pelvis
- Pericardium
Advantages of US (3)
- Fast, immediate results
- Cheap, especially compared to other modalities
- Good for the pt, no radiation
