Lecture 11- Ultrasounds Flashcards
Training for Medical Sonographer
- typically 2 yr education program tied to bachelor’s degree
example certifications
- RDMS: OB/GYN, abd
- RVT: vascular
- RDCS: echo, peds echo
- can get certs in neuro, B mode/eye
Ultrasound Provider
UP, mid level provider (only really find these in echos)
master’s degree
OB/GYN
transabd approach
- TAS- transabdominal approach
- requires full urinary bladder
- used in later pregnancy (very late may not need full bladder), ovaries, uterus
OB/GYN
endovaginal sonography
- requires empty bladder
- use in early pregnancy, ovaries, uterus
- frquencies 5-10MHz, limited FOV
OB/GYN
First trimester studies
- Ectopic pregnancy
- Threatened AB (cervix open/closed, fetal viability/death, anembryonic pregnancy/blighted ovum)
- Sonographic dates (gestational sac size, crown rump length)
OB/GYN
Crown rump length
measured as the greatest length in a straight line from the cranial to the caudal end of the body in the straightest possible position of the embryo/fetus
OB/GYN
2nd and 3rd trimester US use
Fetal measurements
* biparietal diameter (BPD)
* head circumference (HC)
* abd circumference (AC)
* femoral length to humeral length ratio (FL/HL)
OBGYN
Other uses
- Intrauterine growth retardation (IUGR)
- premature rupture of membranes (PROM)
- multiple gestations (seen on volume ultrasound mode)
- congenital anomalies
OB/GYN
Biophysical Profile Fetal Assessment
- Level II US
- Fetal Assessment: number, position, lie; breathing, movement, tone, reactive heart rate
- Fetal Data: measure BPD, FL, AC; systematic organ review
- Placenta, amniotic fluid, cord
OB/GYN
US guided OB procedures
- Amniocentesis: AFP level abnormal, fetal lung maturity check, level of fluid
- Chorionic Villus Sampling (CVS): prenatal test that involves taking a sample of tissue from the placenta to test for chromosomal abnormalities and certain other genetic problems
OB/GYN
purpose of US for GYN exams
- uterine abnormalities
- adnexa-ovarian pathology (tumor vs cyst)
- IUD placement
- PID changes
US Overview
Transducers
- change one form of energy into another
- Piezoelectric crystals creat a voltage when mechanically deformed and is the active component of the transducer (emits US frequency waves)
- requires conductivity gel
US Overview
Frequency
- Number of cycles per sec
- Hertz/Hz (hearing is 30-20,000 Hz; US is > 20,000 Hz- usually 2MHz-10MHz)
- determined by sound source (variable frequency based on what you’re imaging)
US Overview
Beam Anatomy
- beam starts as size of transducer
- converges to focal point (focal length, diverges in far zone, larger diameteres have further focal length)
US Overview
US transducer beam
- sound waves in transducers don’t diffract
- most energy transmitted along main central beam
US Overview
Resolution
- Lateral Resolution : 2 points distinguishable when side by side
- Depth resolution : 2 points distinguishable when front to back
- Wavelength influences resolution (higher frequency –> higher resolution, but lower penetration)
- Ex: thyroid use 10MHz bc it’s superficial; liver might require 2MHz bc it’s deeper
US Overview
Pulsed Waves
- collection of number of cycles that travel together
- On time: transducer sending
- Off time: receiving (capturing return trip information)
US Overview
receiver
- as image depth increases, the pulse repetition frequency decreases (# of pulses per second) so requires more listening time
- operator determines maximum imaging depth
US Overview
Acoustic Propagation Properties
Effects of medium upon sound wave
* propagation speed
* attenuation (absorption, reflection, scattering)
* impedance
US Overview
propagation speed
- determined by density and stiffness of medium
- lungs (0.5 km/sec), fat (1.45 km/sec), soft tissue (1.54 km/sec), bone (3.0 km/sec)
- speed m/s = frequency (Hz) x wavelength (m)
US Overview
Attenuation
- decrease in intensity and amplification in soft tissue
- greater frequency, greater attenuation
- limits maximum depth from which one can obtain images
US Overview
Absorption
- energy imparted to cell is lost by conversion to another form such as heat/vibration of intracellular particles
US Overview
reflextion
- some of propagating acoustic energy is re-directed back toward transducer
- smooth reflector (mirror) is specular reflector (diaphragm)
when to do specular reflector longitudinal scan
- diaphragm
- liver
- kidney (loss of curve on outline)
US Overview
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
US Overview
Impedance
- acoustic resistance to sound as travels through medium
- intensity increases w/ decreased density and with increased propagation speed
US Overview
media that is difficult to image
- bone: reflects too much, high speed (increased impedance, attenuation)
- lung: too much scatter, low propagation speed
US Overview
artifact sources
- machine malfunctioning
- poor engineering
- acoustic artifacts
- operator error
- interpretor error
US Overview
acoustic artifact types
- reverberation
- shadowing
- enhancement
- reflectors
- propagation speed
- resolution
Acoustic Artifact
describe reverberation
multiple echos or reflextion equally spaced (2+ reflectors in US beam)
Acoustic Artifact
describe shadowing
- occurs when US can’t pass through first structure
- occurs when first structure is highly reflective, highly attenuated, highly scattered
- sound does not penetrate, so acoustic shadow as useful artifact: renal claculi, cholelithiasis
Acoustic Artifact
describe 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
Acoustic Artifact
describe curved/oblique reflextors
image may not be present or understated
Acoustic Artifact
describe propagation speed errors
- if tissue is not 1.54 km/sec, there will be incorrect depth of image
- ex: fatty liver disease will change speed
Acoustic Artifact
describe resolution
- appears as 1, if closer than resolution of machine (try imaging in different plane to confirm)
US Overview
quality assurance
- tissue equivalent phantom: cysts, solids, same resolution lateral and vertical
US Overview
biological effects & safety measures
- very high US intensity can cause damage
- thermal injury: exams that cause < 1 deg C elevation of temp is safe; anything > 41 degC can be harmful to fetus
- Cavitation: bodies of gas/bubbles which can become excited by US (vibrate/shrink) leading to soft tissue injury
- do not perform w/out reason, do not prolong scan w/out reason, use minimal output power needed
Real Time Imaging Studies
Sector imaging
- transverse, sagittal plane images
- can obtain obliques
- array of elements w/in transducer
Real Time Imaging Studies
orientation to transabdominal approach fils
- Outer approach
- Longitudinal: head on L, foot on R
- Transverse: point toward pt’s R
- cavity approach changes orientation
US Overview
echogenicity
- more white = more echogenic = more dense
- more black = less echogenic = fluid
- imaging choice for cystic vs solid
US Overview
describe cyst appearance
black fluid filled sac
US Overview
describe transabdominal sonography (TAS)
- NPO (reduces bowel gas, GB should be “full”)
- look for free fluid & tap if found
US Overview
Biliary System Etiologies
- cholecystitis
- Cholelithiasis
- choledocholithiasis
- GB polyps
- echogenic bile
US Overview
pancreatic etiologies and US use
- pseudocysts
- tumors
- acute pancreatitis: swollen/large, less echogenic
- chronic pancreatitis: damaged, more echogenic areas
- hard to visualized when normal
US Overview
vessels around pancreas on US
- aorta is round w/ thicker wall
- IVC is “collapsed” w/ thinner wall
- fat around SMA
- splenic vein courses opposite
US Overview
kidney etiologies
- hydronephrosis
- parenchymal changes
- masses
- cysts
- congenital deformities
- adrenals (not usually visualized)
US Overview
why does kidney appear different colors
- NOT MEDULLA VS CORTEX
- center is echogenic due to the collecting system
US Overview
what aids in kidney visualization
- liver aids in R kidney (kidney usually less echogenic)
- spleen aids in L kidney (spleen smaller)
US Overview
describe hydronephrosis
- dilated collecting system in renal pelvis
- +/- hydroureter
US Overview
splenic etiologies
- enlargement
- rupture
- sickle cell
- neoplasms
US Overview
spleen appearances on US
normally homogenous
US Overview
retroperitoneum etiologies
- enlarged lymph nodes
- masses
- aorta
- abscess
US Overview
use of US in AAA
- visualize lumen walls and blood flow/clots
US Overview
high resolution of superficial structures
- thyroid
- scrotum/testes
- breast
US Overview
Thyroid US
- normally homogenous but can see cysts, malignant lesions, multi-nodular goiter, and developmental cysts
- Parathyroids are not visible on US
US Overview
Scrotum/Testicular US
- normall homogenous but can visualize edema, hydrocele, orchitis, epididymitis, carcinoma, seminoma, variocele
US Overview
what is hydrocele
fluid in scrotal sac
US Overview
Breast US
- breast parenchyma is fairly homogenous
- can detect masses, cysts, abscesses
US Overview
purpose of pelvis studies
- full urinary bladder for acoustic window
- can do pre and post void for volume/residual volume
US Overview
prostate US
- echogenicity is usually homogenous
- do transrectal approach to view size/masses
US Overview
neonatal imaging
- can do because they have fontanelles and cartilage not bone, so we can see through it
- evaluate for hydrocephalus (enlarged ventricular system w/ CSF)
US Overview
Misc uses
eye, vascular
- eye: retinal detachment
- vascular: venous or arterial doppler
US Overview
describe doppler shift
- change infrequency of sound as result of motion between sound and receiver (RBCs bounching)
- Hz: doppler shifts of -10KHz to +10KHz in doppler studies
- Negative #s: away from transducer
- Positive #s: toward transducer
US Overview
describe doppler
- 0 or 180 deg: no image as the sound beam and motion are parallel
- 90deg: velocity is 0, use for imaging
- motion mode for flow- graphic
US Overview
describe aliasing
- artifact when flow appears negative but is actually positive
- the deeper the sample volume the more and the higher the frequency the more likely aliasing is to occur
US Overview
what are duplex studies
- imaging and doppler in same study
US Overview
color flow doppler
- color is related to direction of flow in relation to transducer (pos/neg)
- many times this may correspond to venous vs arterial flow
US Overview
echocardiograms
- heart imaging
- has motion and imaging modes which show valvular abnormalities, wall motion analysis, ejection fraction, pericardial effusion
- need to image through cardiac window (aka between bones)
US Overview
Echo frequencies
- Peds: diamters 3-6mm; 3.5, 5.0, 7.5 MHz
- Adults: 3.5, 2.25, 1.6 MHz
- can do transesophageal approach for best resolution
FAST ultrasound
- Focused Assessment w/ Sonography for Trauma (FAST)
- Hepatorenal recess (morison pouch), peisplenic area, subxiphoid pericardial window, suprapubic window (Douglas pouch)
what does E Fast add?
- extended fast
- Hepatorenal recess (morison pouch), peisplenic area, subxiphoid pericardial window, suprapubic window (Douglas pouch)
PLUS
* bilateral hemithoraces and upper anterior chest wall
