Ultrasound Flashcards
The Medical Sonographer
RDMS- registered diagnostic medical sonographer
Typical 2 year education program
Now typically tied to Bachelor’s degree
Didactic and Clinical
Other routes, i.e. on the job (OTJ) cross training
National boards
Different specialties
Ultrasound physics as additional part of certification
Ultrasound Provider- UP
Mid level provider for ultrasound department
Has not “taken off” except in echo
Masters Degree
OB/GYNE
TAS
transabdominal approach
Full urinary bladder
Later pregnancy (very late may not need full bladder), ovaries, uterus
OB/GYNE
EVS
endovaginal sonography
Empty bladder
Early pregnancy, ovaries, uterus
Frequencies of 5-10 MHz
Limited FOV (Field of View)
First Trimester Studies
indications
Ectopic pregnancy
Threatened Ab
Cervix open vs closed
Fetal viability/death
Anembryonic pregnancy (blighted ovum)
Sonographic dates
Gestational sac size (see Figure)
Crown Rump length (see Figure)
gesttional sac size
measure the size of the ovum when the fetus isnt big enough to measure
crown to rump size
2nd and 3rd trimesters
fetal measurements (4)
Fetal measurements
BPD- biparietal diameter
HC- head circumference
AC- abdominal circumference
FL/HL- femoral length to humeral length ratio
obgyn
IUGR- intrauterine growth retardation
baby isnt growing at proper rate
OBGYN
PROM- premature rupture of membranes
As seen in “Volume” ultrasound mode
3D look
Biophysical Profile
Level II US (See table)
Fetal assessment
Number, position, lie
Breathing, movements, tone, reactive heart rate
Fetal Data
Measurements BPD, FL, AC
Systematic organ review
Placenta, amniotic fluid amount
Cord
measurements taken to grade the baby, this is done if there are concerns for baby.
US Guided OB Procedures
Amniocentesis
Chorionic Villus sampling (CVS)
Amneocentesis
AFP level abnormal
Fetal lung maturity check
Level of fluid
CVS can help identify certain genetic diseases, including problems with chromosomes. These cell structures hold fetal DNA.
Gyne Exams
Transducers
Change one form of energy into another
Piezoelectric crystals (created a voltage when mechanically deformed) –>The active component of transducer
Emits ultrasound frequency waves
Conductivity gel is needed to make an image
frequency
Numbers of cycles per second
Hertz or Hz
Hearing 30-20,000 Hz
US uses >20,000
Clinical imaging 2MHz –10 MHz
Determined by sound source
Transducer named for main frequency
Beam Anatomy
Beam starts as size of transducer
Converges to focal point
Focal length
Diverges in the far zone
Larger diameters have further focal length
Ultrasound transducer beam
Sound waves in transducers don’t diffract
Most energy transmitted along main central beam
Resolution
Lateral resolution
2 points distinguishable when side by side
Depth resolution
2 pts distinguishable when “front to back”
Wavelength influences resolution
Higher frequency, higher resolution (less penetration)
Pulsed Waves
Collection of number of cycles that travel together
On time- transducer sending
Off time- receiving
Capturing return trip information
Receiver
As image depth increases, the pulse repetition frequency decreases (number of pulses per second) so more listening time
Operator determines maximum imaging depth
Acoustic Propagation Properties
Effects of medium upon sound wave
Propagation speed
Attenuation
Absorption
Reflection
Scattering
Impedance
Propagation speed
Determined by density and stiffness of medium
All sound travels at the same speed through same medium
Soft tissue (st)- 1.54 km/s (1.54 mm/s)
Lung< fat < soft tissue < bone
0.5, 1.45, 1.54, 3.0 km/sec respectively
Speed m/s = frequency (Hz) x wavelength (m)
know that fat and soft tissue are similar speed, but fat is slightly fas
Attenuation
Decrease in intensity and amplification in soft tissue
Greater frequency, greater attenuation
Limits maximum depth from which can obtain images
Absorption
Energy imparted to cell is lost by conversion to another form such as heat or vibration of intracellular particles
Reflection
Some of propagating acoustic energy is redirected back toward transducer
Smooth reflector (i.e. mirror) is specular reflector (e.g. diaphragm)
Specular reflector is the line around the kidney in this image, it disappears where the reflection doesnt bounce back to the transducer.
the inside of the kidney that is hyperechoic (lighter) is due to the collectiong ducts.
Scattering
If boundary between 2 media has irregularities, with a size similar to pulses’ wavelength, the wavelength can be redirected into many directions
Backscatter to transducer
Rayleigh scatter- dont need to know this name
Impedance
Acoustic resistance to sound as travels through medium
Intensity increases with decrease density and with increased propagation speed
Difficult to Image Media
Bone
Great reflector
Backscatter/reflection
High propagation speed
Increased impedance
Increased attenuation
Lung
Great scatter
Low propagation speed
Artifact Sources
Machine malfunctioning
Poor engineering
Acoustic artifacts
Operator error
Interpreter error- Anatomic artifact/pitfall
Acoustic Artifact Types
Reverberation
Shadowing
Enhancement
Reflectors
Propagation speed
Resolution
Acoustic Artifact Types
Reverberation
Multiple echos or reflection equally spaced
May occur when 2 strong reflectors lie in line of US beam
Acoustic Artifact Types
Shadowing
US cannot pass through first structure
either highly reflective or high attenuation or highly scattered
sound does not penetrate, so acoustic shadow as useful artifact:
renal calculi
cholelithiasis
Acoustic Artifact Types
Enhancement
Appears higher than normal echo amplitude after sound passes through fluid
increased “ease” of sound transmission through fluid less impedence, faster speed
May have fill in artifact
“opposite fo shadowing”
Acoustic Artifact Types
Curved and Oblique reflectors
Image not present or understated
(see previous renal film/specular reflector)
Acoustic Artifact Types
Propagation speed errors
If tissue is not 1.54 KM/sec, incorrect depth of image
Acoustic Artifact Types
Resolution
Appears as 1, if closer than resolution of machine
Try to image in different plane to confirm
Note: any abnormal finding in any imaging discipline tries to see same in another orientation to “confirm”
Quality Assurance
Tissue equivalent phantom
Cysts
Solids
Resolution
lateral and vertical
Biological Effects & Safety Measures
Very high US intensity can cause damage
Thermal injury
Exams that cause <1 degree Centigrade elevation of temperature are considered safe
Exams that cause >41 degrees Centigrade temperature are harmful to fetus
Safety issues
Cavitation
Bodies of gas, bubbles, cavities may be excited by US
May vibrate, shrink, expand
Could lead to tissue injury
Minimal evidence that this really occurs, but could in theory
Can at lithotripsy levels
Do not perform a scan without reason
Do not prolong a scan without reason
Use minimal output power to produce images
Orientation to transabdominal approach films
Typical “outer” approach
Longitudinal
Head on L
Foot on R
Transverse
R
L
Cavity approach changes orientation
Echogenicity
Presented white on black
More white, more echogenic
(Denser matter)
black, less echogenic
(Fluid)
Imaging choice for cystic vs. solid
Cyst
“Black” fluid filled
Enhancement
Abdominal studies
Transabdominal sonography (TAS)
Usually NPO
Decreases bowel gas
GB should be “full”
Same technique in chest wall cavity when looking for fluid
Pleural effusion
US guided tap
Common Abdominal Studies
GB and Biliary system
Pancreas- should not be visible, if it is its too mig
Kidneys
Spleen
Retroperitoneum
Cholelithiasis
GB and Biliary system
Liver, GB, CHD, CD, HA, PV
Cholecystitis
Cholelithiasis
Choledocholithiasis
GB polyps
Echogenic Bile
Choledocholithiasis
Cholecystitis-thick shaggy GB wall
Pancreas
what can you see w US
Pseudocysts
Pancreatitis
Acute vs chronic
Tumors
Pancreas tricky to visualize when normal
Note classic structures
Aorta round- thicker wall
IVC “collapsed”-thinner wall
Fat around Superior Mesenteric Artery (SMA)
Splenic Vein (SV) courses opposite
Acute pancreatitis, swollen large, less echogenic
Chronic pancreatitis, increased echogenic damaged areas
Kidneys
Hydronephrosis
Parenchymal changes
CFR- small kidneys, more echogenic
Masses
Cysts
Congenital deformities
Adrenals- not usually visualized
Homogeneous parenchyma
Center is echogenic collecting system
NOT medulla vs cortex, its the parynchema vs collecting ducts
Usually less echogenic than liver
Liver aids visualization of Right
Spleen aids visualization of Left
But spleen normally smaller
Hydronephrosis
Dilated collecting system in renal pelvis
Can have hydroureter as well
Spleen
Enlargement
Infections
Hematopoietic disorders
WBC disorders
Rupture
Sickle cell
Neoplasms
spleen is Normally homogeneous
Retroperitoneum
Enlarged lymph nodes
Masses
Aorta
Abscess
AAA
Lumen walls
Lumen that blood flows through/clot
High Resolution of Superficial Structures
Thyroid
Scrotum and Testes
Breast
Thyroid
Normally homogeneous
True cysts
Malignant lesions
Multinodular goiter
Developmental cysts
Parathyroids are NOT usually visualized
Scrotum and Testes
Normally homogeneous
Edema
Hydrocele
Orchitis and Epididymitis
Carcinoma
Seminoma
Varicocele
Hydrocele
F= Fluid in scrotal sac
Breast
Breast parenchyma fairly homogeneous
Masses
Cysts
Abscess
Pelvic studies
Full urinary bladder for acoustic window
Urinary bladder
Pre and post void for volume/residual volume
Prostate studies
Echogenicity usually homogeneous
Transrectal approach
Size
Masses
Neonatal brain
Acousic window
Cartilage, not bone
Fontanelles
Why is this test not for an adult brain?
Doppler shift
Change in frequency of sound as result of motion between sound and receiver
RBCs bouncing
Hz
Doppler shifts of -10 KHz to +10 KHz in Doppler studies
negative is away from transducer, dec frequency
positive is toward transducer, increased frequency
Doppler
0 or 180 degrees - there is no image as the sound beam and motion are parallel
90 degrees, the velocity is 0, good for imaging
Motion mode for flow- graphic
Aliasing
Artifact when flow appears negative but really positive
the deeper the sample volume (chosen by sonographer) the more likely aliasing
higher frequency, more likely aliasing
lower frequencies used more often
Duplex studies
Images and Doppler in same study
Color flow Doppler
Color is related to direction of flow in relation to transducer (positive/negative)
Many times this may correspond to venous vs. arterial flow
structures imaged B&W
Color added to vessels for flow/fxn
A pulsed US technique
Provides a range of resolution at expense of aliasing
Echocardiography
Heart Imaging
motion mode and imaging modes
valvular abnormalities
wall motion analysis
ejection fraction
pericardial effusion
Need to image through “cardiac window”
Between bones
Echo frequencies
highest frequency but smallest diameter transducers
Peds 3.5, 5.0, 7.5 MHz
diameters 3-6 mm
Adults 3.5, 2.25, 1.6 MHz
also a range of diameters
(transesophageal approach for even better resolution)
FAST Ultrasound
Focused assessment with sonography for trauma (FAST) 4 areas:
(1) hepatorenal recess (Morison pouch)
(2) perisplenic area
(3) subxiphoid pericardial window
(4) suprapubic window (Douglas pouch)
https://www.ncbi.nlm.nih.gov/books/NBK470479/
E-FAST US
extended FAST (E-FAST) add:
(1) bilateral hemithoraces
(2) upper anterior chest wall
https://emedicine.medscape.com/article/104363-overview#a2
https://www.saem.org/about-saem/academies-interest-groups-affiliates2/cdem/for-students/online-education/m3-curriculum/bedside-ultrasonagraphy/fast-exam
US Take Home Points
Anatomical imagine, some function applications
Acoustic properties guide what “tissues” look like so don’t “see” same things as other imaging modalities
Sounds waves, not radiation, theoretical safety issues
